SUDO_PLUGIN(5) | File Formats Manual | SUDO_PLUGIN(5) |
NAME
sudo_plugin
— Sudo
Plugin API
DESCRIPTION
Starting with version 1.8, sudo
supports a
plugin API for policy and session logging. Plugins may be compiled as
dynamic shared objects (the default on systems that support them) or
compiled statically into the sudo
binary itself. By
default, the sudoers
plugin provides audit, security
policy and I/O logging capabilities. Via the plugin API,
sudo
can be configured to use alternate plugins
provided by third parties. The plugins to be used are specified in the
sudo.conf(5) file.
The API is versioned with a major and minor number. The minor version number is incremented when additions are made. The major number is incremented when incompatible changes are made. A plugin should be check the version passed to it and make sure that the major version matches.
The plugin API is defined by the
<sudo_plugin.h>
header
file.
Policy plugin API
A policy plugin must declare and populate a struct
policy_plugin in the global scope. This structure contains pointers to
the functions that implement the sudo
policy checks.
The name of the symbol should be specified in
sudo.conf(5) along with a path
to the plugin so that sudo
can load it.
struct policy_plugin { #define SUDO_POLICY_PLUGIN 1 unsigned int type; /* always SUDO_POLICY_PLUGIN */ unsigned int version; /* always SUDO_API_VERSION */ int (*open)(unsigned int version, sudo_conv_t conversation, sudo_printf_t sudo_plugin_printf, char * const settings[], char * const user_info[], char * const user_env[], char * const plugin_options[], const char **errstr); void (*close)(int exit_status, int error); int (*show_version)(int verbose); int (*check_policy)(int argc, char * const argv[], char *env_add[], char **command_info[], char **argv_out[], char **user_env_out[], const char **errstr); int (*list)(int argc, char * const argv[], int verbose, const char *user, const char **errstr); int (*validate)(const char **errstr); void (*invalidate)(int rmcred); int (*init_session)(struct passwd *pwd, char **user_env[], const char **errstr); void (*register_hooks)(int version, int (*register_hook)(struct sudo_hook *hook)); void (*deregister_hooks)(int version, int (*deregister_hook)(struct sudo_hook *hook)); struct sudo_plugin_event * (*event_alloc)(void); };
A struct policy_plugin has the following fields:
- type
- The type field should always be set to SUDO_POLICY_PLUGIN.
- version
- The version field should be set to
SUDO_API_VERSION
.This allows
sudo
to determine the API version the plugin was built against. - open
-
int (*open)(unsigned int version, sudo_conv_t conversation, sudo_printf_t sudo_plugin_printf, char * const settings[], char * const user_info[], char * const user_env[], char * const plugin_options[], const char **errstr);
Returns 1 on success, 0 on failure, -1 if a general error occurred, or -2 if there was a usage error. In the latter case,
sudo
will print a usage message before it exits. If an error occurs, the plugin may optionally call theconversation
() orsudo_plugin_printf
() function withSUDO_CONF_ERROR_MSG
to present additional error information to the user.The function arguments are as follows:
- version
- The version passed in by
sudo
allows the plugin to determine the major and minor version number of the plugin API supported bysudo
. - conversation
- A pointer to the
conversation
() function that can be used by the plugin to interact with the user (see Conversation API for details). Returns 0 on success and -1 on failure. - sudo_plugin_printf
- A pointer to a
printf
()-style function that may be used to display informational or error messages (see Conversation API for details). Returns the number of characters printed on success and -1 on failure. - settings
- A vector of user-supplied
sudo
settings in the form of “name=value” strings. The vector is terminated by aNULL
pointer. These settings correspond to options the user specified when runningsudo
. As such, they will only be present when the corresponding option has been specified on the command line.When parsing settings, the plugin should split on the first equal sign (‘
=
’) since the name field will never include one itself but the value might.The following values may be set by
sudo
:- bsdauth_type=string
- Authentication type, if specified by the
-a
option, to use on systems where BSD authentication is supported. - closefrom=number
- If specified, the user has requested via the
-C
option thatsudo
close all files descriptors with a value of number or higher. The plugin may optionally pass this, or another value, back in the command_info list. - cmnd_chroot=string
- The root directory (see
chroot(2)) to run the
command in, as specified by the user via the
-R
option. The plugin may ignore or restrict the user's ability to specify a new root directory. Only available starting with API version 1.16. - cmnd_cwd=string
- The working directory to run the command in, as specified by the
user via the
-D
option. The plugin may ignore or restrict the user's ability to specify a new working directory. Only available starting with API version 1.16. - debug_flags=string
- A debug file path name followed by a space and a comma-separated
list of debug flags that correspond to the plugin's
Debug entry in
sudo.conf(5), if
there is one. The flags are passed to the plugin exactly as they
appear in
sudo.conf(5). The
syntax used by
sudo
and thesudoers
plugin is subsystem@priority but a plugin is free to use a different format so long as it does not include a comma (‘,
’). Prior tosudo
1.8.12, there was no way to specify plugin-specific debug_flags so the value was always the same as that used by thesudo
front-end and did not include a path name, only the flags themselves. As of version 1.7 of the plugin interface,sudo
will only pass debug_flags if sudo.conf(5) contains a plugin-specific Debug entry. - ignore_ticket=bool
- Set to true if the user specified the
-k
option along with a command, indicating that the user wishes to ignore any cached authentication credentials. implied_shell to true. This allowssudo
with no arguments to be used similarly to su(1). If the plugin does not to support this usage, it may return a value of -2 from thecheck_policy
() function, which will causesudo
to print a usage message and exit. - implied_shell=bool
- If the user does not specify a program on the command line,
sudo
will pass the plugin the path to the user's shell and set implied_shell. - intercept_ptrace=bool
- Indicates whether or not the system supports intercept mode using ptrace(2). This is currently only true for Linux systems that support seccomp(2) filtering and the “trap” action. Other systems will use a dynamic shared object to implement intercept. Only available starting with API version 1.19.
- intercept_setid=bool
- Indicates whether or not the system supports running set-user-ID and set-group-ID binaries in intercept mode. This is currently only true for Linux systems that support seccomp(2) filtering and the “trap” action. On systems that use a dynamic shared object to implement intercept, the dynamic linker (ld.so or the equivalent) will disable preloading of shared objects when executing a set-user-ID or set-group-ID binary. This will disable intercept mode for that program and any other programs that it executes. The policy plugin may refuse to execute a set-user-ID or set-group-ID binary in intercept mode to avoid this. Only available starting with API version 1.19.
- login_class=string
- BSD login class to use when setting
resource limits and nice value, if specified by the
-c
option. - login_shell=bool
- Set to true if the user specified the
-i
option, indicating that the user wishes to run a login shell. - max_groups=int
- The maximum number of groups a user may belong to. This will only be present if there is a corresponding setting in sudo.conf(5).
- network_addrs=list
- A space-separated list of IP network addresses and netmasks in the
form “addr/netmask”, e.g.,
“192.168.1.2/255.255.255.0”. The address and netmask
pairs may be either IPv4 or IPv6, depending on what the operating
system supports. If the address contains a colon
(‘
:
’), it is an IPv6 address, else it is IPv4. - noninteractive=bool
- Set to true if the user specified the
-n
option, indicating thatsudo
should operate in non-interactive mode. The plugin may reject a command run in non-interactive mode if user interaction is required. - plugin_dir=string
- The default plugin directory used by the
sudo
front-end. This is the default directory set at compile time and may not correspond to the directory the running plugin was loaded from. It may be used by a plugin to locate support files. - plugin_path=string
- The path name of plugin loaded by the
sudo
front-end. The path name will be a fully-qualified unless the plugin was statically compiled intosudo
. - preserve_environment=bool
- Set to true if the user specified the
-E
option, indicating that the user wishes to preserve the environment. - preserve_groups=bool
- Set to true if the user specified the
-P
option, indicating that the user wishes to preserve the group vector instead of setting it based on the runas user. - progname=string
- The command name that sudo was run as, typically “sudo” or “sudoedit”.
- prompt=string
- The prompt to use when requesting a password, if specified via the
-p
option. - remote_host=string
- The name of the remote host to run the command on, if specified
via the
-h
option. Support for running the command on a remote host is meant to be implemented via a helper program that is executed in place of the user-specified command. Thesudo
front-end is only capable of executing commands on the local host. Only available starting with API version 1.4. - run_shell=bool
- Set to true if the user specified the
-s
option, indicating that the user wishes to run a shell. - runas_group=string
- The group name or group-ID to run the command as, if specified via
the
-g
option. - runas_user=string
- The user name or user-ID to run the command as, if specified via
the
-u
option. - selinux_role=string
- SELinux role to use when executing the command, if specified by
the
-r
option. - selinux_type=string
- SELinux type to use when executing the command, if specified by
the
-t
option. - set_home=bool
- Set to true if the user specified the
-H
option. If true, set theHOME
environment variable to the target user's home directory. - sudoedit=bool
- Set to true when the
-e
option is specified or if invoked assudoedit
. The plugin shall substitute an editor into argv in thecheck_policy
() function or return -2 with a usage error if the plugin does not support sudoedit. For more information, see thecheck_policy
() section. - timeout=string
- Command timeout specified by the user via the
-T
option. Not all plugins support command timeouts and the ability of the user to set a timeout may be restricted by policy. The format of the timeout string is plugin-specific. - update_ticket=bool
- Set to false if the user specified the
-N
option, indicating that the user wishes to avoid updating any cached authentication credentials. Only available starting with API version 1.20.
Additional settings may be added in the future so the plugin should silently ignore settings that it does not recognize.
- user_info
- A vector of information about the user running the command in the form
of “name=value” strings. The vector is terminated by a
NULL
pointer.When parsing user_info, the plugin should split on the first equal sign (‘
=
’) since the name field will never include one itself but the value might.The following values may be set by
sudo
:- cols=int
- The number of columns the user's terminal supports. If there is no terminal device available, a default value of 80 is used.
- cwd=string
- The user's current working directory.
- egid=gid_t
- The effective group-ID of the user invoking
sudo
. - euid=uid_t
- The effective user-ID of the user invoking
sudo
. - gid=gid_t
- The real group-ID of the user invoking
sudo
. - groups=list
- The user's supplementary group list formatted as a string of comma-separated group-IDs.
- host=string
- The local machine's hostname as returned by the gethostname(2) system call.
- lines=int
- The number of lines the user's terminal supports. If there is no terminal device available, a default value of 24 is used.
- pgid=int
- The ID of the process group that the running
sudo
process is a member of. Only available starting with API version 1.2. - pid=int
- The process ID of the running
sudo
process. Only available starting with API version 1.2. - ppid=int
- The parent process ID of the running
sudo
process. Only available starting with API version 1.2. - rlimit_as=soft,hard
- The maximum size to which the process's address space may grow (in bytes), if supported by the operating system. The soft and hard limits are separated by a comma. A value of “infinity” indicates that there is no limit. Only available starting with API version 1.16.
- rlimit_core=soft,hard
- The largest size core dump file that may be created (in bytes). The soft and hard limits are separated by a comma. A value of “infinity” indicates that there is no limit. Only available starting with API version 1.16.
- rlimit_cpu=soft,hard
- The maximum amount of CPU time that the process may use (in seconds). The soft and hard limits are separated by a comma. A value of “infinity” indicates that there is no limit. Only available starting with API version 1.16.
- rlimit_data=soft,hard
- The maximum size of the data segment for the process (in bytes). The soft and hard limits are separated by a comma. A value of “infinity” indicates that there is no limit. Only available starting with API version 1.16.
- rlimit_fsize=soft,hard
- The largest size file that the process may create (in bytes). The soft and hard limits are separated by a comma. A value of “infinity” indicates that there is no limit. Only available starting with API version 1.16.
- rlimit_locks=soft,hard
- The maximum number of locks that the process may establish, if supported by the operating system. The soft and hard limits are separated by a comma. A value of “infinity” indicates that there is no limit. Only available starting with API version 1.16.
- rlimit_memlock=soft,hard
- The maximum size that the process may lock in memory (in bytes), if supported by the operating system. The soft and hard limits are separated by a comma. A value of “infinity” indicates that there is no limit. Only available starting with API version 1.16.
- rlimit_nofile=soft,hard
- The maximum number of files that the process may have open. The soft and hard limits are separated by a comma. A value of “infinity” indicates that there is no limit. Only available starting with API version 1.16.
- rlimit_nproc=soft,hard
- The maximum number of processes that the user may run simultaneously. The soft and hard limits are separated by a comma. A value of “infinity” indicates that there is no limit. Only available starting with API version 1.16.
- rlimit_rss=soft,hard
- The maximum size to which the process's resident set size may grow (in bytes). The soft and hard limits are separated by a comma. A value of “infinity” indicates that there is no limit. Only available starting with API version 1.16.
- rlimit_stack=soft,hard
- The maximum size to which the process's stack may grow (in bytes). The soft and hard limits are separated by a comma. A value of “infinity” indicates that there is no limit. Only available starting with API version 1.16.
- sid=int
- The session ID of the running
sudo
process or 0 ifsudo
is not part of a POSIX job control session. Only available starting with API version 1.2. - tcpgid=int
- The ID of the foreground process group associated with the
terminal device associated with the
sudo
process or 0 if there is no terminal present. Only available starting with API version 1.2. - tty=string
- The path to the user's terminal device, if one exists. This entry is only present if the user has a terminal device associated with the session.
- ttydev=dev_t
- The number of the user's terminal device, if one exists, formatted as a long long value. This entry is only present if the user has a terminal device associated with the session. Only available starting with API version 1.22.
- uid=uid_t
- The real user-ID of the user invoking
sudo
. - umask=octal
- The invoking user's file creation mask. Only available starting with API version 1.10.
- user=string
- The name of the user invoking
sudo
.
- user_env
- The user's environment in the form of a
NULL
-terminated vector of “name=value” strings.When parsing user_env, the plugin should split on the first equal sign (‘
=
’) since the name field will never include one itself but the value might. - plugin_options
- Any (non-comment) strings immediately after the plugin path are passed
as arguments to the plugin. These arguments are split on a white space
boundary and are passed to the plugin in the form of a
NULL
-terminated array of strings. If no arguments were specified, plugin_options will be theNULL
pointer.The plugin_options parameter is only available starting with API version 1.2. A plugin must check the API version specified by the
sudo
front-end before using plugin_options. Failure to do so may result in a crash. - errstr
- If the
open
() function returns a value other than 1, the plugin may store a message describing the failure or error in errstr. Thesudo
front-end will then pass this value to any registered audit plugins. The string stored in errstr must remain valid until the plugin'sclose
() function is called.The errstr parameter is only available starting with API version 1.15. A plugin must check the API version specified by the
sudo
front-end before using errstr. Failure to do so may result in a crash.
- close
-
void (*close)(int exit_status, int error);
The
close
() function is called whensudo
is finished, shortly before it exits. Starting with API version 1.15,close
() is called regardless of whether or not a command was actually executed. This makes it possible for plugins to perform cleanup even when a command was not run. It is not possible to tell whether a command was run based solely on the arguments passed to theclose
() function. To determine if a command was actually run, the plugin must keep track of whether or not thecheck_policy
() function returned successfully.The function arguments are as follows:
- exit_status
- The command's exit status, as returned by the wait(2) system call, or zero if no command was run. The value of exit_status is undefined if error is non-zero.
- error
- If the command could not be executed, this is set to the value of
errno set by the
execve(2) system call. The
plugin is responsible for displaying error information via the
conversation
() orsudo_plugin_printf
() function. If the command was successfully executed, the value of error is zero.
If no
close
() function is defined, no I/O logging plugins are loaded, and neither the timeout nor use_pty options are set in the command_info list, thesudo
front-end may execute the command directly instead of running it as a child process. - show_version
-
int (*show_version)(int verbose);
The
show_version
() function is called bysudo
when the user specifies the-V
option. The plugin may display its version information to the user via theconversation
() orsudo_plugin_printf
() function usingSUDO_CONV_INFO_MSG
. If the user requests detailed version information, the verbose flag will be non-zero.Returns 1 on success, 0 on failure, -1 if a general error occurred, or -2 if there was a usage error, although the return value is currently ignored.
- check_policy
-
int (*check_policy)(int argc, char * const argv[], char *env_add[], char **command_info[], char **argv_out[], char **user_env_out[], const char **errstr);
The
check_policy
() function is called bysudo
to determine whether the user is allowed to run the specified commands.If the sudoedit option was enabled in the settings array passed to the
open
() function, the user has requested sudoedit mode. sudoedit is a mechanism for editing one or more files where an editor is run with the user's credentials instead of with elevated privileges.sudo
achieves this by creating user-writable temporary copies of the files to be edited and then overwriting the originals with the temporary copies after editing is complete. If the plugin supports sudoedit, it must set sudoedit=true in the command_info list. The plugin is responsible for choosing the editor to be used, potentially from a variable in the user's environment, such asEDITOR
, and should be stored in argv_out (environment variables may include command line options). The files to be edited should be copied from argv to argv_out, separated from the editor and its arguments by a ‘--
’ element. The ‘--
’ will be removed bysudo
before the editor is executed. The plugin may also set sudoedit_nfiles to the number of files to be edited in the command_info list; this will only be used by thesudo
front-end starting with API version 1.21.The
check_policy
() function returns 1 if the command is allowed, 0 if not allowed, -1 for a general error, or -2 for a usage error or if sudoedit was specified but is unsupported by the plugin. In the latter case,sudo
will print a usage message before it exits. If an error occurs, the plugin may optionally call theconversation
() orsudo_plugin_printf
() function withSUDO_CONF_ERROR_MSG
to present additional error information to the user.The function arguments are as follows:
- argc
- The number of elements in argv, not counting the
final
NULL
pointer. - argv
- The argument vector describing the command the user wishes to run, in
the same form as what would be passed to the
execve(2) system call. The
vector is terminated by a
NULL
pointer. - env_add
- Additional environment variables specified by the user on the command
line in the form of a
NULL
-terminated vector of “name=value” strings. The plugin may reject the command if one or more variables are not allowed to be set, or it may silently ignore such variables.When parsing env_add, the plugin should split on the first equal sign (‘
=
’) since the name field will never include one itself but the value might. - command_info
- Information about the command being run in the form of
“name=value” strings. These values are used by
sudo
to set the execution environment when running a command. The plugin is responsible for creating and populating the vector, which must be terminated with aNULL
pointer. The following values are recognized bysudo
:- apparmor_profile=string
- AppArmor profile to transition to when executing the command. Only available starting with API version 1.19.
- chroot=string
- The root directory to use when running the command.
- closefrom=number
- If specified,
sudo
will close all files descriptors with a value of number or higher. - command=string
- Fully qualified path to the command to be executed.
- cwd=string
- The current working directory to change to when executing the
command. If
sudo
is unable to change to the new working directory, the command will not be run unless cwd_optional is also set (see below). - cwd_optional=bool
- If set,
sudo
will treat an inability to change to the new working directory as a non-fatal error. This setting has no effect unless cwd is also set. - exec_background=bool
- By default,
sudo
runs a command as the foreground process as long assudo
itself is running in the foreground. When exec_background is enabled and the command is being run in a pseudo-terminal (due to I/O logging or the use_pty setting), the command will be run as a background process. Attempts to read from the controlling terminal (or to change terminal settings) will result in the command being suspended with theSIGTTIN
signal (orSIGTTOU
in the case of terminal settings). If this happens whensudo
is a foreground process, the command will be granted the controlling terminal and resumed in the foreground with no user intervention required. The advantage of initially running the command in the background is thatsudo
need not read from the terminal unless the command explicitly requests it. Otherwise, any terminal input must be passed to the command, whether it has required it or not (the kernel buffers terminals so it is not possible to tell whether the command really wants the input). This is different from historicsudo
behavior or when the command is not being run in a pseudo-terminal.For this to work seamlessly, the operating system must support the automatic restarting of system calls. Unfortunately, not all operating systems do this by default, and even those that do may have bugs. For example, macOS fails to restart the
tcgetattr
() andtcsetattr
() system calls (this is a bug in macOS). Furthermore, because this behavior depends on the command stopping with theSIGTTIN
orSIGTTOU
signals, programs that catch these signals and suspend themselves with a different signal (usuallySIGTOP
) will not be automatically foregrounded. Some versions of the linux su(1) command behave this way. Because of this, a plugin should not set exec_background unless it is explicitly enabled by the administrator and there should be a way to enabled or disable it on a per-command basis.This setting has no effect unless I/O logging is enabled or use_pty is enabled.
- execfd=number
- If specified,
sudo
will use the fexecve(2) system call to execute the command instead of execve(2). The specified number must refer to an open file descriptor. - intercept=bool
- If set,
sudo
will intercept attempts to execute a subsequent command and perform a policy check via the policy plugin'scheck_policy
() function to determine whether or not the command is permitted. This can be used to prevent shell escapes on supported platforms but it has a number of limitations. See Preventing shell escapes in sudoers(5) for details. Only available starting with API version 1.18. - intercept_verify=bool
- If set,
sudo
will attempt to verify that a command run in intercept mode has the expected path name, command line arguments and environment. This setting has no effect unless use_ptrace is also enabled. Only available starting with API version 1.20. - iolog_compress=bool
- Set to true if the I/O logging plugins, if any, should compress the log data. This is a hint to the I/O logging plugin which may choose to ignore it.
- iolog_group=string
- The group that will own newly created I/O log files and directories. This is a hint to the I/O logging plugin which may choose to ignore it.
- iolog_mode=octal
- The file permission mode to use when creating I/O log files and directories. This is a hint to the I/O logging plugin which may choose to ignore it.
- iolog_user=string
- The user that will own newly created I/O log files and directories. This is a hint to the I/O logging plugin which may choose to ignore it.
- iolog_path=string
- Fully qualified path to the file or directory in which I/O log is to be stored. This is a hint to the I/O logging plugin which may choose to ignore it. If no I/O logging plugin is loaded, this setting has no effect.
- iolog_stdin=bool
- Set to true if the I/O logging plugins, if any, should log the standard input if it is not connected to a terminal device. This is a hint to the I/O logging plugin which may choose to ignore it.
- iolog_stdout=bool
- Set to true if the I/O logging plugins, if any, should log the standard output if it is not connected to a terminal device. This is a hint to the I/O logging plugin which may choose to ignore it.
- iolog_stderr=bool
- Set to true if the I/O logging plugins, if any, should log the standard error if it is not connected to a terminal device. This is a hint to the I/O logging plugin which may choose to ignore it.
- iolog_ttyin=bool
- Set to true if the I/O logging plugins, if any, should log all terminal input. This only includes input typed by the user and not from a pipe or redirected from a file. This is a hint to the I/O logging plugin which may choose to ignore it.
- iolog_ttyout=bool
- Set to true if the I/O logging plugins, if any, should log all terminal output. This only includes output to the screen, not output to a pipe or file. This is a hint to the I/O logging plugin which may choose to ignore it.
- login_class=string
- BSD login class to use when setting resource limits and nice value (optional). This option is only set on systems that support login classes.
- nice=int
- Nice value (priority) to use when executing the command. The nice value, if specified, overrides the priority associated with the login_class on BSD systems.
- log_subcmds=bool
- If set,
sudo
will call the audit plugin'saccept
() function to log when the command runs a subsequent command, if supported by the system. If intercept is also specified, log_subcmds will be ignored. See Preventing shell escapes in sudoers(5) for more information. Only available starting with API version 1.18. - noexec=bool
- If set, prevent the command from executing other programs.
- preserve_fds=list
- A comma-separated list of file descriptors that should be preserved, regardless of the value of the closefrom setting. Only available starting with API version 1.5.
- preserve_groups=bool
- If set,
sudo
will preserve the user's group vector instead of initializing the group vector based on runas_user. - rlimit_as=soft,hard
- The maximum size to which the process's address space may grow (in bytes), if supported by the operating system. The soft and hard limits are separated by a comma. If only a single value is specified, both the hard and soft limits are set. A value of “infinity” indicates that there is no limit. A value of “user” will cause the invoking user's resource limit to be preserved. A value of “default” will cause the target user's default resource limit to be used on systems that allow per-user resource limits to be configured. Only available starting with API version 1.18.
- rlimit_core=soft,hard
- The largest size core dump file that may be created (in bytes). The soft and hard limits are separated by a comma. If only a single value is specified, both the hard and soft limits are set. A value of “infinity” indicates that there is no limit. A value of “user” will cause the invoking user's resource limit to be preserved. A value of “default” will cause the target user's default resource limit to be used on systems that allow per-user resource limits to be configured. Only available starting with API version 1.18.
- rlimit_cpu=soft,hard
- The maximum amount of CPU time that the process may use (in seconds). The soft and hard limits are separated by a comma. If only a single value is specified, both the hard and soft limits are set. A value of “infinity” indicates that there is no limit. A value of “user” will cause the invoking user's resource limit to be preserved. A value of “default” will cause the target user's default resource limit to be used on systems that allow per-user resource limits to be configured. Only available starting with API version 1.18.
- rlimit_data=soft,hard
- The maximum size of the data segment for the process (in bytes). The soft and hard limits are separated by a comma. If only a single value is specified, both the hard and soft limits are set. A value of “infinity” indicates that there is no limit. A value of “user” will cause the invoking user's resource limit to be preserved. A value of “default” will cause the target user's default resource limit to be used on systems that allow per-user resource limits to be configured. Only available starting with API version 1.18.
- rlimit_fsize=soft,hard
- The largest size file that the process may create (in bytes). The soft and hard limits are separated by a comma. If only a single value is specified, both the hard and soft limits are set. A value of “infinity” indicates that there is no limit. A value of “user” will cause the invoking user's resource limit to be preserved. A value of “default” will cause the target user's default resource limit to be used on systems that allow per-user resource limits to be configured. Only available starting with API version 1.18.
- rlimit_locks=soft,hard
- The maximum number of locks that the process may establish, if supported by the operating system. The soft and hard limits are separated by a comma. If only a single value is specified, both the hard and soft limits are set. A value of “infinity” indicates that there is no limit. A value of “user” will cause the invoking user's resource limit to be preserved. A value of “default” will cause the target user's default resource limit to be used on systems that allow per-user resource limits to be configured. Only available starting with API version 1.18.
- rlimit_memlock=soft,hard
- The maximum size that the process may lock in memory (in bytes), if supported by the operating system. The soft and hard limits are separated by a comma. If only a single value is specified, both the hard and soft limits are set. A value of “infinity” indicates that there is no limit. A value of “user” will cause the invoking user's resource limit to be preserved. A value of “default” will cause the target user's default resource limit to be used on systems that allow per-user resource limits to be configured. Only available starting with API version 1.18.
- rlimit_nofile=soft,hard
- The maximum number of files that the process may have open. The soft and hard limits are separated by a comma. If only a single value is specified, both the hard and soft limits are set. A value of “infinity” indicates that there is no limit. A value of “user” will cause the invoking user's resource limit to be preserved. A value of “default” will cause the target user's default resource limit to be used on systems that allow per-user resource limits to be configured. Only available starting with API version 1.18.
- rlimit_nproc=soft,hard
- The maximum number of processes that the user may run simultaneously. The soft and hard limits are separated by a comma. If only a single value is specified, both the hard and soft limits are set. A value of “infinity” indicates that there is no limit. A value of “user” will cause the invoking user's resource limit to be preserved. A value of “default” will cause the target user's default resource limit to be used on systems that allow per-user resource limits to be configured. Only available starting with API version 1.18.
- rlimit_rss=soft,hard
- The maximum size to which the process's resident set size may grow (in bytes). The soft and hard limits are separated by a comma. If only a single value is specified, both the hard and soft limits are set. A value of “infinity” indicates that there is no limit. A value of “user” will cause the invoking user's resource limit to be preserved. A value of “default” will cause the target user's default resource limit to be used on systems that allow per-user resource limits to be configured. Only available starting with API version 1.18.
- rlimit_stack=soft,hard
- The maximum size to which the process's stack may grow (in bytes). The soft and hard limits are separated by a comma. If only a single value is specified, both the hard and soft limits are set. A value of “infinity” indicates that there is no limit. A value of “user” will cause the invoking user's resource limit to be preserved. A value of “default” will cause the target user's default resource limit to be used on systems that allow per-user resource limits to be configured. Only available starting with API version 1.18.
- runas_egid=gid
- Effective group-ID to run the command as. If not specified, the value of runas_gid is used.
- runas_euid=uid
- Effective user-ID to run the command as. If not specified, the value of runas_uid is used.
- runas_gid=gid
- Group-ID to run the command as.
- runas_group=string
- The name of the group the command will run as, if it is different
from the runas_user's default group. This value
is provided for auditing purposes only, the
sudo
front-end uses runas_egid and runas_gid when executing the command. - runas_groups=list
- The supplementary group vector to use for the command in the form of a comma-separated list of group-IDs. If preserve_groups is set, this option is ignored.
- runas_uid=uid
- User-ID to run the command as.
- runas_user=string
- The name of the user the command will run as, which should
correspond to runas_euid (or
runas_uid if runas_euid is not
set). This value is provided for auditing purposes only, the
sudo
front-end uses runas_euid and runas_uid when executing the command. - selinux_role=string
- SELinux role to use when executing the command.
- selinux_type=string
- SELinux type to use when executing the command.
- set_utmp=bool
- Create a utmp (or utmpx) entry when a pseudo-terminal is allocated. By default, the new entry will be a copy of the user's existing utmp entry (if any), with the tty, time, type, and pid fields updated.
- sudoedit=bool
- Set to true when in sudoedit mode. The plugin
may enable sudoedit mode even if
sudo
was not invoked assudoedit
. This allows the plugin to perform command substitution and transparently enable sudoedit when the user attempts to run an editor. - sudoedit_checkdir=bool
- Set to false to disable directory writability checks in
sudoedit
. By default,sudoedit
1.8.16 and higher will check all directory components of the path to be edited for writability by the invoking user. Symbolic links will not be followed in writable directories andsudoedit
will refuse to edit a file located in a writable directory. These restrictions are not enforced whensudoedit
is run by root. The sudoedit_checkdir option can be set to false to disable this check. Only available starting with API version 1.8. - sudoedit_follow=bool
- Set to true to allow
sudoedit
to edit files that are symbolic links. By default,sudoedit
1.8.15 and higher will refuse to open a symbolic link. The sudoedit_follow option can be used to restore the older behavior and allowsudoedit
to open symbolic links. Only available starting with API version 1.8. - sudoedit_nfiles=number
- The number of files to be edited by the user. If present, this is
will be used by the
sudo
front-end to determine which elements of the argv_out vector are files to be edited. The ‘--
’ element must immediately precede the first file to be edited. If sudoedit_nfiles is not specified, thesudo
front-end will use the position of the ‘--
’ element to determine where the file list begins. Only available starting with API version 1.21. - timeout=int
- Command timeout. If non-zero then when the timeout expires the command will be killed.
- umask=octal
- The file creation mask to use when executing the command. This value may be overridden by PAM or login.conf on some systems unless the umask_override option is also set.
- umask_override=bool
- Force the value specified by the umask option to override any umask set by PAM or login.conf.
- use_ptrace=bool
- If set,
sudo
will use ptrace(2) to implement intercept mode if supported by the system. This setting has no effect unless intercept is also set. Only available starting with API version 1.19. - use_pty=bool
- Allocate a pseudo-terminal to run the command in, regardless of
whether or not I/O logging is in use. By default,
sudo
will only run the command in a pseudo-terminal when an I/O log plugin is loaded. - utmp_user=string
- User name to use when constructing a new utmp (or utmpx) entry
when
set_utmp
is enabled. This option can be used to set the user field in the
utmp entry to the user the command runs as rather than the
invoking user. If not set,
sudo
will base the new entry on the invoking user's existing entry.
Unsupported values will be ignored.
- argv_out
- The
NULL
-terminated argument vector to pass to the execve(2) system call when executing the command. The plugin is responsible for allocating and populating the vector. - user_env_out
- The
NULL
-terminated environment vector to use when executing the command. The plugin is responsible for allocating and populating the vector. - errstr
- If the
check_policy
() function returns a value other than 1, the plugin may store a message describing the failure or error in errstr. Thesudo
front-end will then pass this value to any registered audit plugins. The string stored in errstr must remain valid until the plugin'sclose
() function is called.The errstr parameter is only available starting with API version 1.15. A plugin must check the API version specified by the
sudo
front-end before using errstr. Failure to do so may result in a crash.
- list
-
int (*list)(int argc, char * const argv[], int verbose, const char *user, const char **errstr);
List available privileges for the invoking user. Returns 1 on success, 0 on failure, and -1 on error. On error, the plugin may optionally call the
conversation
() orsudo_plugin_printf
() function withSUDO_CONF_ERROR_MSG
to present additional error information to the user.Privileges should be output via the
conversation
() orsudo_plugin_printf
() function usingSUDO_CONV_INFO_MSG
.The function arguments are as follows:
- argc
- The number of elements in argv, not counting the
final
NULL
pointer. - argv
- If non-
NULL
, an argument vector describing a command the user wishes to check against the policy in the same form as what would be passed to the execve(2) system call. If the command is permitted by the policy, the fully-qualified path to the command should be displayed along with any command line arguments. - verbose
- Flag indicating whether to list in verbose mode or not.
- user
- The name of a different user to list privileges for if the policy
allows it. If
NULL
, the plugin should list the privileges of the invoking user. - errstr
- If the
list
() function returns a value other than 1, the plugin may store a message describing the failure or error in errstr. Thesudo
front-end will then pass this value to any registered audit plugins. The string stored in errstr must remain valid until the plugin'sclose
() function is called.The errstr parameter is only available starting with API version 1.15. A plugin must check the API version specified by the
sudo
front-end before using errstr. Failure to do so may result in a crash.
- validate
-
int (*validate)(const char **errstr);
The
validate
() function is called whensudo
is run with the-v
option. For policy plugins such assudoers
that cache authentication credentials, this function will validate and cache the credentials.The
validate
() function should beNULL
if the plugin does not support credential caching.Returns 1 on success, 0 on failure, and -1 on error. On error, the plugin may optionally call the
conversation
() orsudo_plugin_printf
() function withSUDO_CONF_ERROR_MSG
to present additional error information to the user.The function arguments are as follows:
- errstr
- If the
validate
() function returns a value other than 1, the plugin may store a message describing the failure or error in errstr. Thesudo
front-end will then pass this value to any registered audit plugins. The string stored in errstr must remain valid until the plugin'sclose
() function is called.The errstr parameter is only available starting with API version 1.15. A plugin must check the API version specified by the
sudo
front-end before using errstr. Failure to do so may result in a crash.
- invalidate
-
void (*invalidate)(int rmcred);
The
invalidate
() function is called whensudo
is run with the-k
or-K
option. For policy plugins such assudoers
that cache authentication credentials, this function will invalidate the credentials. If the rmcred flag is non-zero, the plugin may remove the credentials instead of simply invalidating them.The
invalidate
() function should beNULL
if the plugin does not support credential caching. - init_session
-
int (*init_session)(struct passwd *pwd, char **user_env[], const char **errstr);
The
init_session
() function is called beforesudo
sets up the execution environment for the command. It is run in the parentsudo
process before any user-ID or group-ID changes. This can be used to perform session setup that is not supported by command_info, such as opening the PAM session. Theclose
() function can be used to tear down the session that was opened byinit_session
().Returns 1 on success, 0 on failure, and -1 on error. On error, the plugin may optionally call the
conversation
() orsudo_plugin_printf
() function withSUDO_CONF_ERROR_MSG
to present additional error information to the user.The function arguments are as follows:
- pwd
- If the user-ID the command will run as was found in the password
database, pwd will describe that user, otherwise
it will be
NULL
. - user_env_out
- The
NULL
-terminated environment vector to use when executing the command. This is the same string passed back to the front-end via the Policy Plugin's user_env_out parameter. If theinit_session
() function needs to modify the user environment, it should update the pointer stored in user_env_out. The expected use case is to merge the contents of the PAM environment (if any) with the contents of user_env_out. The user_env_out parameter is only available starting with API version 1.2. A plugin must check the API version specified by thesudo
front-end before using user_env_out. Failure to do so may result in a crash. - errstr
- If the
init_session
() function returns a value other than 1, the plugin may store a message describing the failure or error in errstr. Thesudo
front-end will then pass this value to any registered audit plugins. The string stored in errstr must remain valid until the plugin'sclose
() function is called.The errstr parameter is only available starting with API version 1.15. A plugin must check the API version specified by the
sudo
front-end before using errstr. Failure to do so may result in a crash.
- register_hooks
-
void (*register_hooks)(int version, int (*register_hook)(struct sudo_hook *hook));
The
register_hooks
() function is called by the sudo front-end to register any hooks the plugin needs. If the plugin does not support hooks, register_hooks should be set to theNULL
pointer.The version argument describes the version of the hooks API supported by the
sudo
front-end.The
register_hook
() function should be used to register any supported hooks the plugin needs. It returns 0 on success, 1 if the hook type is not supported, and -1 if the major version in struct sudo_hook does not match the front-end's major hook API version.See the Hook function API section below for more information about hooks.
The
register_hooks
() function is only available starting with API version 1.2. If thesudo
front-end doesn't support API version 1.2 or higher,register_hooks
() will not be called. - deregister_hooks
-
void (*deregister_hooks)(int version, int (*deregister_hook)(struct sudo_hook *hook));
The
deregister_hooks
() function is called by the sudo front-end to deregister any hooks the plugin has registered. If the plugin does not support hooks, deregister_hooks should be set to theNULL
pointer.The version argument describes the version of the hooks API supported by the
sudo
front-end.The
deregister_hook
() function should be used to deregister any hooks that were put in place by theregister_hook
() function. If the plugin tries to deregister a hook that the front-end does not support,deregister_hook
() will return an error.See the Hook function API section below for more information about hooks.
The
deregister_hooks
() function is only available starting with API version 1.2. If thesudo
front-end doesn't support API version 1.2 or higher,deregister_hooks
() will not be called. - event_alloc
-
struct sudo_plugin_event * (*event_alloc)(void);
The
event_alloc
() function is used to allocate a struct sudo_plugin_event which provides access to the mainsudo
event loop. Unlike the other fields, the event_alloc pointer is filled in by thesudo
front-end, not by the plugin.See the Event API section below for more information about events.
The
event_alloc
() function is only available starting with API version 1.15. If thesudo
front-end doesn't support API version 1.15 or higher, event_alloc will not be set.
/* Plugin API version major/minor. */ #define SUDO_API_VERSION_MAJOR 1 #define SUDO_API_VERSION_MINOR 13 #define SUDO_API_MKVERSION(x, y) ((x << 16) | y) #define SUDO_API_VERSION SUDO_API_MKVERSION(SUDO_API_VERSION_MAJOR,\ SUDO_API_VERSION_MINOR) /* Getters and setters for API version */ #define SUDO_API_VERSION_GET_MAJOR(v) ((v) >> 16) #define SUDO_API_VERSION_GET_MINOR(v) ((v) & 0xffff) #define SUDO_API_VERSION_SET_MAJOR(vp, n) do { \ *(vp) = (*(vp) & 0x0000ffff) | ((n) << 16); \ } while(0) #define SUDO_API_VERSION_SET_MINOR(vp, n) do { \ *(vp) = (*(vp) & 0xffff0000) | (n); \ } while(0)
I/O plugin API
struct io_plugin { #define SUDO_IO_PLUGIN 2 unsigned int type; /* always SUDO_IO_PLUGIN */ unsigned int version; /* always SUDO_API_VERSION */ int (*open)(unsigned int version, sudo_conv_t conversation, sudo_printf_t sudo_plugin_printf, char * const settings[], char * const user_info[], char * const command_info[], int argc, char * const argv[], char * const user_env[], char * const plugin_options[], const char **errstr); void (*close)(int exit_status, int error); /* wait status or error */ int (*show_version)(int verbose); int (*log_ttyin)(const char *buf, unsigned int len, const char **errstr); int (*log_ttyout)(const char *buf, unsigned int len, const char **errstr); int (*log_stdin)(const char *buf, unsigned int len, const char **errstr); int (*log_stdout)(const char *buf, unsigned int len, const char **errstr); int (*log_stderr)(const char *buf, unsigned int len, const char **errstr); void (*register_hooks)(int version, int (*register_hook)(struct sudo_hook *hook)); void (*deregister_hooks)(int version, int (*deregister_hook)(struct sudo_hook *hook)); int (*change_winsize)(unsigned int lines, unsigned int cols, const char **errstr); int (*log_suspend)(int signo, const char **errstr); struct sudo_plugin_event * (*event_alloc)(void); };
When an I/O plugin is loaded, sudo
runs
the command in a pseudo-terminal. This makes it possible to log the input
and output from the user's session. If any of the standard input, standard
output, or standard error do not correspond to a tty,
sudo
will open a pipe to capture the I/O for logging
before passing it on.
The
log_ttyin
()
function receives the raw user input from the terminal device (this will
include input even when echo is disabled, such as when a password is read).
The log_ttyout
() function receives output from the
pseudo-terminal that is suitable for replaying the user's session at a later
time. The log_stdin
(),
log_stdout
(), and
log_stderr
() functions are only called if the
standard input, standard output, or standard error respectively correspond
to something other than a tty.
Any of the logging functions may be set to the
NULL
pointer if no logging is to be performed. If
the open function returns 0, no I/O will be sent to the plugin.
If a logging function returns an error (-1), the running command will be terminated and all of the plugin's logging functions will be disabled. Other I/O logging plugins will still receive any remaining input or output that has not yet been processed.
If an input logging function rejects the data by returning 0, the command will be terminated and the data will not be passed to the command, though it will still be sent to any other I/O logging plugins. If an output logging function rejects the data by returning 0, the command will be terminated and the data will not be written to the terminal, though it will still be sent to any other I/O logging plugins.
A struct audit_plugin has the following fields:
- type
- The type field should always be set to
SUDO_IO_PLUGIN
. - version
- The version field should be set to
SUDO_API_VERSION
.This allows
sudo
to determine the API version the plugin was built against. - open
-
int (*open)(unsigned int version, sudo_conv_t conversation, sudo_printf_t sudo_plugin_printf, char * const settings[], char * const user_info[], char * const command_info[], int argc, char * const argv[], char * const user_env[], char * const plugin_options[]);
The
open
() function is run before thelog_ttyin
(),log_ttyout
(),log_stdin
(),log_stdout
(),log_stderr
(),log_suspend
(),change_winsize
(), orshow_version
() functions are called. It is only called if the version is being requested or if the policy plugin'scheck_policy
() function has returned successfully. It returns 1 on success, 0 on failure, -1 if a general error occurred, or -2 if there was a usage error. In the latter case,sudo
will print a usage message before it exits. If an error occurs, the plugin may optionally call theconversation
() orsudo_plugin_printf
() function withSUDO_CONF_ERROR_MSG
to present additional error information to the user.The function arguments are as follows:
- version
- The version passed in by
sudo
allows the plugin to determine the major and minor version number of the plugin API supported bysudo
. - conversation
- A pointer to the
conversation
() function that may be used by theFa
(show_version) function to display version information (seeshow_version
() below). Theconversation
() function may also be used to display additional error message to the user. Theconversation
() function returns 0 on success and -1 on failure. - sudo_plugin_printf
- A pointer to a
printf
()-style function that may be used by theshow_version
() function to display version information (see show_version below). Thesudo_plugin_printf
() function may also be used to display additional error message to the user. Thesudo_plugin_printf
() function returns number of characters printed on success and -1 on failure. - settings
- A vector of user-supplied
sudo
settings in the form of “name=value” strings. The vector is terminated by aNULL
pointer. These settings correspond to options the user specified when runningsudo
. As such, they will only be present when the corresponding option has been specified on the command line.When parsing settings, the plugin should split on the first equal sign (‘
=
’) since the name field will never include one itself but the value might.See the Policy plugin API section for a list of all possible settings.
- user_info
- A vector of information about the user running the command in the form
of “name=value” strings. The vector is terminated by a
NULL
pointer.When parsing user_info, the plugin should split on the first equal sign (‘
=
’) since the name field will never include one itself but the value might.See the Policy plugin API section for a list of all possible strings.
- command_info
- A vector of information describing the command being run in the form
of “name=value” strings. The vector is terminated by a
NULL
pointer.When parsing command_info, the plugin should split on the first equal sign (‘
=
’) since the name field will never include one itself but the value might.See the Policy plugin API section for a list of all possible strings.
- argc
- The number of elements in argv, not counting the
final
NULL
pointer. It can be zero, such as whensudo
is called with the-V
option. - argv
- If non-
NULL
, an argument vector describing a command the user wishes to run in the same form as what would be passed to the execve(2) system call. - user_env
- The user's environment in the form of a
NULL
-terminated vector of “name=value” strings.When parsing user_env, the plugin should split on the first equal sign (‘
=
’) since the name field will never include one itself but the value might. - plugin_options
- Any (non-comment) strings immediately after the plugin path are
treated as arguments to the plugin. These arguments are split on a
white space boundary and are passed to the plugin in the form of a
NULL
-terminated array of strings. If no arguments were specified, plugin_options will be theNULL
pointer.The plugin_options parameter is only available starting with API version 1.2. A plugin must check the API version specified by the
sudo
front-end before using plugin_options. Failure to do so may result in a crash. - errstr
- If the
open
() function returns a value other than 1, the plugin may store a message describing the failure or error in errstr. Thesudo
front-end will then pass this value to any registered audit plugins. The string stored in errstr must remain valid until the plugin'sclose
() function is called.The errstr parameter is only available starting with API version 1.15. A plugin must check the API version specified by the
sudo
front-end before using errstr. Failure to do so may result in a crash.
- close
-
void (*close)(int exit_status, int error);
The
close
() function is called whensudo
is finished, shortly before it exits.The function arguments are as follows:
- exit_status
- The command's exit status, as returned by the wait(2) system call, or zero if no command was run. The value of exit_status is undefined if error is non-zero.
- error
- If the command could not be executed, this is set to the value of errno set by the execve(2) system call. If the command was successfully executed, the value of error is zero.
- show_version
-
int (*show_version)(int verbose);
The
show_version
() function is called bysudo
when the user specifies the-V
option. The plugin may display its version information to the user via theconversation
() orsudo_plugin_printf
() function usingSUDO_CONV_INFO_MSG
. If the user requests detailed version information, the verbose flag will be non-zero.Returns 1 on success, 0 on failure, -1 if a general error occurred, or -2 if there was a usage error, although the return value is currently ignored.
- log_ttyin
-
int (*log_ttyin)(const char *buf, unsigned int len, const char **errstr);
The
log_ttyin
() function is called whenever data can be read from the user but before it is passed to the running command. This allows the plugin to reject data if it chooses to (for instance if the input contains banned content). Returns 1 if the data should be passed to the command, 0 if the data is rejected (which will terminate the running command), or -1 if an error occurred.The function arguments are as follows:
- buf
- The buffer containing user input.
- len
- The length of buf in bytes.
- errstr
- If the
log_ttyin
() function returns a value other than 1, the plugin may store a message describing the failure or error in errstr. Thesudo
front-end will then pass this value to any registered audit plugins. The string stored in errstr must remain valid until the plugin'sclose
() function is called.The errstr parameter is only available starting with API version 1.15. A plugin must check the API version specified by the
sudo
front-end before using errstr. Failure to do so may result in a crash.
- log_ttyout
-
int (*log_ttyout)(const char *buf, unsigned int len, const char **errstr);
The
log_ttyout
() function is called whenever data can be read from the command but before it is written to the user's terminal. This allows the plugin to reject data if it chooses to (for instance if the output contains banned content). Returns 1 if the data should be passed to the user, 0 if the data is rejected (which will terminate the running command), or -1 if an error occurred.The function arguments are as follows:
- buf
- The buffer containing command output.
- len
- The length of buf in bytes.
- errstr
- If the
log_ttyout
() function returns a value other than 1, the plugin may store a message describing the failure or error in errstr. Thesudo
front-end will then pass this value to any registered audit plugins. The string stored in errstr must remain valid until the plugin'sclose
() function is called.The errstr parameter is only available starting with API version 1.15. A plugin must check the API version specified by the
sudo
front-end before using errstr. Failure to do so may result in a crash.
- log_stdin
-
int (*log_stdin)(const char *buf, unsigned int len, const char **errstr);
The
log_stdin
() function is only used if the standard input does not correspond to a tty device. It is called whenever data can be read from the standard input but before it is passed to the running command. This allows the plugin to reject data if it chooses to (for instance if the input contains banned content). Returns 1 if the data should be passed to the command, 0 if the data is rejected (which will terminate the running command), or -1 if an error occurred.The function arguments are as follows:
- buf
- The buffer containing user input.
- len
- The length of buf in bytes.
- errstr
- If the
log_stdin
() function returns a value other than 1, the plugin may store a message describing the failure or error in errstr. Thesudo
front-end will then pass this value to any registered audit plugins. The string stored in errstr must remain valid until the plugin'sclose
() function is called.The errstr parameter is only available starting with API version 1.15. A plugin must check the API version specified by the
sudo
front-end before using errstr. Failure to do so may result in a crash.
- log_stdout
-
int (*log_stdout)(const char *buf, unsigned int len, const char **errstr);
The
log_stdout
() function is only used if the standard output does not correspond to a tty device. It is called whenever data can be read from the command but before it is written to the standard output. This allows the plugin to reject data if it chooses to (for instance if the output contains banned content). Returns 1 if the data should be passed to the user, 0 if the data is rejected (which will terminate the running command), or -1 if an error occurred.The function arguments are as follows:
- buf
- The buffer containing command output.
- len
- The length of buf in bytes.
- errstr
- If the
log_stdout
() function returns a value other than 1, the plugin may store a message describing the failure or error in errstr. Thesudo
front-end will then pass this value to any registered audit plugins. The string stored in errstr must remain valid until the plugin'sclose
() function is called.The errstr parameter is only available starting with API version 1.15. A plugin must check the API version specified by the
sudo
front-end before using errstr. Failure to do so may result in a crash.
- log_stderr
-
int (*log_stderr)(const char *buf, unsigned int len, const char **errstr);
The
log_stderr
() function is only used if the standard error does not correspond to a tty device. It is called whenever data can be read from the command but before it is written to the standard error. This allows the plugin to reject data if it chooses to (for instance if the output contains banned content). Returns 1 if the data should be passed to the user, 0 if the data is rejected (which will terminate the running command), or -1 if an error occurred.The function arguments are as follows:
- buf
- The buffer containing command output.
- len
- The length of buf in bytes.
- errstr
- If the
log_stderr
() function returns a value other than 1, the plugin may store a message describing the failure or error in errstr. Thesudo
front-end will then pass this value to any registered audit plugins. The string stored in errstr must remain valid until the plugin'sclose
() function is called.The errstr parameter is only available starting with API version 1.15. A plugin must check the API version specified by the
sudo
front-end before using errstr. Failure to do so may result in a crash.
- register_hooks
- See the Policy plugin API
section for a description of
register_hooks
(). - deregister_hooks
- See the Policy plugin API
section for a description of
deregister_hooks
(). - change_winsize
-
int (*change_winsize)(unsigned int lines, unsigned int cols, const char **errstr);
The
change_winsize
() function is called whenever the window size of the terminal changes from the initial values specified in the user_info list. Returns -1 if an error occurred, in which case no further calls tochange_winsize
() will be made,The function arguments are as follows:
- lines
- The number of lines (rows) in the re-sized terminal.
- cols
- The number of columns in the re-sized terminal.
- errstr
- If the
change_winsize
() function returns a value other than 1, the plugin may store a message describing the failure or error in errstr. Thesudo
front-end will then pass this value to any registered audit plugins. The string stored in errstr must remain valid until the plugin'sclose
() function is called.The errstr parameter is only available starting with API version 1.15. A plugin must check the API version specified by the
sudo
front-end before using errstr. Failure to do so may result in a crash.
- log_suspend
-
int (*log_suspend)(int signo, const char **errstr);
The
log_suspend
() function is called whenever a command is suspended or resumed. Logging this information makes it possible to skip the period of time when the command was suspended during playback of a session. Returns -1 if an error occurred, in which case no further calls tolog_suspend
() will be made,The function arguments are as follows:
- signo
- The signal that caused the command to be suspended, or
SIGCONT
if the command was resumed. - errstr
- If the
log_suspend
() function returns a value other than 1, the plugin may store a message describing the failure or error in errstr. Thesudo
front-end will then pass this value to any registered audit plugins. The string stored in errstr must remain valid until the plugin'sclose
() function is called.The errstr parameter is only available starting with API version 1.15. A plugin must check the API version specified by the
sudo
front-end before using errstr. Failure to do so may result in a crash. - event_alloc
-
struct sudo_plugin_event * (*event_alloc)(void);
The
event_alloc
() function is used to allocate a struct sudo_plugin_event which provides access to the mainsudo
event loop. Unlike the other fields, theevent_alloc
() pointer is filled in by thesudo
front-end, not by the plugin.See the Event API section below for more information about events.
The
event_alloc
() function is only available starting with API version 1.15. If thesudo
front-end doesn't support API version 1.15 or higher,event_alloc
() will not be set.
Same as for the Policy plugin API.
Audit plugin API
/* Audit plugin close function status types. */ #define SUDO_PLUGIN_NO_STATUS 0 #define SUDO_PLUGIN_WAIT_STATUS 1 #define SUDO_PLUGIN_EXEC_ERROR 2 #define SUDO_PLUGIN_SUDO_ERROR 3 #define SUDO_AUDIT_PLUGIN 3 struct audit_plugin { unsigned int type; /* always SUDO_AUDIT_PLUGIN */ unsigned int version; /* always SUDO_API_VERSION */ int (*open)(unsigned int version, sudo_conv_t conversation, sudo_printf_t sudo_plugin_printf, char * const settings[], char * const user_info[], int submit_optind, char * const submit_argv[], char * const submit_envp[], char * const plugin_options[], const char **errstr); void (*close)(int status_type, int status); int (*accept)(const char *plugin_name, unsigned int plugin_type, char * const command_info[], char * const run_argv[], char * const run_envp[], const char **errstr); int (*reject)(const char *plugin_name, unsigned int plugin_type, const char *audit_msg, char * const command_info[], const char **errstr); int (*error)(const char *plugin_name, unsigned int plugin_type, const char *audit_msg, char * const command_info[], const char **errstr); int (*show_version)(int verbose); void (*register_hooks)(int version, int (*register_hook)(struct sudo_hook *hook)); void (*deregister_hooks)(int version, int (*deregister_hook)(struct sudo_hook *hook)); struct sudo_plugin_event * (*event_alloc)(void); }
An audit plugin can be used to log successful and unsuccessful
attempts to run sudo
independent of the policy or
any I/O plugins. Multiple audit plugins may be specified in
sudo.conf(5).
A struct audit_plugin has the following fields:
- type
- The type field should always be set to
SUDO_AUDIT_PLUGIN
. - version
- The version field should be set to
SUDO_API_VERSION
.This allows
sudo
to determine the API version the plugin was built against. - open
-
int (*open)(unsigned int version, sudo_conv_t conversation, sudo_printf_t sudo_plugin_printf, char * const settings[], char * const user_info[], int submit_optind, char * const submit_argv[], char * const submit_envp[], char * const plugin_options[], const char **errstr);
The audit
open
() function is run before any othersudo
plugin API functions. This makes it possible to audit failures in the other plugins. It returns 1 on success, 0 on failure, -1 if a general error occurred, or -2 if there was a usage error. In the latter case,sudo
will print a usage message before it exits. If an error occurs, the plugin may optionally call theconversation
() orplugin_printf
() function withSUDO_CONF_ERROR_MSG
to present additional error information to the user.The function arguments are as follows:
- version
- The version passed in by
sudo
allows the plugin to determine the major and minor version number of the plugin API supported bysudo
. - conversation
- A pointer to the
conversation
() function that may be used by theshow_version
() function to display version information (seeshow_version
() below). Theconversation
() function may also be used to display additional error message to the user. Theconversation
() function returns 0 on success, and -1 on failure. - plugin_printf
- A pointer to a
printf
()-style function that may be used by theshow_version
() function to display version information (see show_version below). Theplugin_printf
() function may also be used to display additional error message to the user. Theplugin_printf
() function returns number of characters printed on success and -1 on failure. - settings
- A vector of user-supplied
sudo
settings in the form of “name=value” strings. The vector is terminated by aNULL
pointer. These settings correspond to options the user specified when runningsudo
. As such, they will only be present when the corresponding option has been specified on the command line.When parsing settings, the plugin should split on the first equal sign (‘
=
’) since the name field will never include one itself but the value might.See the Policy plugin API section for a list of all possible settings.
- user_info
- A vector of information about the user running the command in the form
of “name=value” strings. The vector is terminated by a
NULL
pointer.When parsing user_info, the plugin should split on the first equal sign (‘
=
’) since the name field will never include one itself but the value might.See the Policy plugin API section for a list of all possible strings.
- submit_optind
- The index into submit_argv that corresponds to
the first entry that is not a command line option. If
submit_argv only consists of options, which may
be the case with the
-l
or-v
options, submit_argv[submit_optind] will evaluate to the NULL pointer. - submit_argv
- The argument vector
sudo
was invoked with, including all command line options. The submit_optind argument can be used to determine the end of the command line options. - submit_envp
- The invoking user's environment in the form of a
NULL
-terminated vector of “name=value” strings.When parsing submit_envp, the plugin should split on the first equal sign (‘
=
’) since the name field will never include one itself but the value might. - plugin_options
- Any (non-comment) strings immediately after the plugin path are
treated as arguments to the plugin. These arguments are split on a
white space boundary and are passed to the plugin in the form of a
NULL
-terminated array of strings. If no arguments were specified, plugin_options will be theNULL
pointer. - errstr
- If the
open
() function returns a value other than 1, the plugin may store a message describing the failure or error in errstr. Thesudo
front-end will then pass this value to any registered audit plugins. The string stored in errstr must remain valid until the plugin'sclose
() function is called.
- close
-
void (*close)(int status_type, int status);
The
close
() function is called whensudo
is finished, shortly before it exits.The function arguments are as follows:
- status_type
- The type of status being passed. One of
SUDO_PLUGIN_NO_STATUS
,SUDO_PLUGIN_WAIT_STATUS
,SUDO_PLUGIN_EXEC_ERROR
orSUDO_PLUGIN_SUDO_ERROR
. - status
- Depending on the value of status_type, this
value is either ignored, the command's exit status as returned by the
wait(2) system call, the value
of errno set by the
execve(2) system call, or
the value of errno resulting from an error in
the
sudo
front-end.
- accept
-
int (*accept)(const char *plugin_name, unsigned int plugin_type, char * const command_info[], char * const run_argv[], char * const run_envp[], const char **errstr);
The
accept
() function is called when a command or action is accepted by a policy or approval plugin. The function arguments are as follows:- plugin_name
- The name of the plugin that accepted the command or
“sudo” for the
sudo
front-end. - plugin_type
- The type of plugin that accepted the command, currently either
SUDO_POLICY_PLUGIN
,SUDO_POLICY_APPROVAL
, orSUDO_FRONT_END
. Theaccept
() function is called multiple times--once for each policy or approval plugin that succeeds and once for the sudo front-end. When called on behalf of the sudo front-end, command_info may include information from an I/O logging plugin as well.Typically, an audit plugin is interested in either the accept status from the
sudo
front-end or from the various policy and approval plugins, but not both. It is possible for the policy plugin to accept a command that is later rejected by an approval plugin, in which case the audit plugin'saccept
() andreject
() functions will both be called. - command_info
- An optional vector of information describing the command being run in
the form of “name=value” strings. The vector is
terminated by a
NULL
pointer.When parsing command_info, the plugin should split on the first equal sign (‘
=
’) since the name field will never include one itself but the value might.See the Policy plugin API section for a list of all possible strings.
- run_argv
- A
NULL
-terminated argument vector describing a command that will be run in the same form as what would be passed to the execve(2) system call. - run_envp
- The environment the command will be run with in the form of a
NULL
-terminated vector of “name=value” strings.When parsing run_envp, the plugin should split on the first equal sign (‘
=
’) since the name field will never include one itself but the value might. - errstr
- If the
accept
() function returns a value other than 1, the plugin may store a message describing the failure or error in errstr. Thesudo
front-end will then pass this value to any registered audit plugins. The string stored in errstr must remain valid until the plugin'sclose
() function is called.
- reject
-
int (*reject)(const char *plugin_name, unsigned int plugin_type, const char *audit_msg, char * const command_info[], const char **errstr);
The
reject
() function is called when a command or action is rejected by a plugin. The function arguments are as follows:- plugin_name
- The name of the plugin that rejected the command.
- plugin_type
- The type of plugin that rejected the command, currently either
SUDO_POLICY_PLUGIN
,SUDO_APPROVAL_PLUGIN
, orSUDO_IO_PLUGIN
.Unlike the
accept
() function, thereject
() function is not called on behalf of thesudo
front-end. - audit_msg
- An optional string describing the reason the command was rejected by
the plugin. If the plugin did not provide a reason,
audit_msg will be the
NULL
pointer. - command_info
- An optional vector of information describing the command being run in
the form of “name=value” strings. The vector is
terminated by a
NULL
pointer.When parsing command_info, the plugin should split on the first equal sign (‘
=
’) since the name field will never include one itself but the value might.See the Policy plugin API section for a list of all possible strings.
- errstr
- If the
reject
() function returns a value other than 1, the plugin may store a message describing the failure or error in errstr. Thesudo
front-end will then pass this value to any registered audit plugins. The string stored in errstr must remain valid until the plugin'sclose
() function is called.
- error
-
int (*error)(const char *plugin_name, unsigned int plugin_type, const char *audit_msg, char * const command_info[], const char **errstr);
The
error
() function is called when a plugin or thesudo
front-end returns an error. The function arguments are as follows:- plugin_name
- The name of the plugin that generated the error or
“sudo” for the
sudo
front-end. - plugin_type
- The type of plugin that generated the error, or
SUDO_FRONT_END
for thesudo
front-end. - audit_msg
- An optional string describing the plugin error. If the plugin did not
provide a description, audit_msg will be the
NULL
pointer. - command_info
- An optional vector of information describing the command being run in
the form of “name=value” strings. The vector is
terminated by a
NULL
pointer.When parsing command_info, the plugin should split on the first equal sign (‘
=
’) since the name field will never include one itself but the value might.See the Policy plugin API section for a list of all possible strings.
- errstr
- If the
error
() function returns a value other than 1, the plugin may store a message describing the failure or error in errstr. Thesudo
front-end will then pass this value to any registered audit plugins. The string stored in errstr must remain valid until the plugin'sclose
() function is called.
- show_version
-
int (*show_version)(int verbose);
The
show_version
() function is called bysudo
when the user specifies the-V
option. The plugin may display its version information to the user via theconversation
() orplugin_printf
() function usingSUDO_CONV_INFO_MSG
. If the user requests detailed version information, the verbose flag will be set.Returns 1 on success, 0 on failure, -1 if a general error occurred, or -2 if there was a usage error, although the return value is currently ignored.
- register_hooks
- See the Policy plugin API
section for a description of
register_hooks
(). - deregister_hooks
- See the Policy plugin API
section for a description of
deregister_hooks
(). - event_alloc
-
struct sudo_plugin_event * (*event_alloc)(void);
The
event_alloc
() function is used to allocate a struct sudo_plugin_event which provides access to the mainsudo
event loop. Unlike the other fields, the event_alloc pointer is filled in by thesudo
front-end, not by the plugin.See the Event API section below for more information about events.
The
event_alloc
() function is only available starting with API version 1.17. If thesudo
front-end doesn't support API version 1.17 or higher,event_alloc
() will not be set.
Approval plugin API
struct approval_plugin { #define SUDO_APPROVAL_PLUGIN 4 unsigned int type; /* always SUDO_APPROVAL_PLUGIN */ unsigned int version; /* always SUDO_API_VERSION */ int (*open)(unsigned int version, sudo_conv_t conversation, sudo_printf_t sudo_plugin_printf, char * const settings[], char * const user_info[], int submit_optind, char * const submit_argv[], char * const submit_envp[], char * const plugin_options[], const char **errstr); void (*close)(void); int (*check)(char * const command_info[], char * const run_argv[], char * const run_envp[], const char **errstr); int (*show_version)(int verbose); };
An approval plugin can be used to apply extra
constraints after a command has been accepted by the policy plugin. Unlike
the other plugin types, it does not remain open until the command completes.
The plugin is opened before a call to
check
() or
show_version
() and closed shortly thereafter (audit
plugin functions must be called before the plugin is closed). Multiple
approval plugins may be specified in
sudo.conf(5).
A struct approval_plugin has the following fields:
- type
- The type field should always be set to
SUDO_APPROVAL_PLUGIN
. - version
- The version field should be set to
SUDO_API_VERSION
.This allows
sudo
to determine the API version the plugin was built against. - open
-
int (*open)(unsigned int version, sudo_conv_t conversation, sudo_printf_t sudo_plugin_printf, char * const settings[], char * const user_info[], int submit_optind, char * const submit_argv[], char * const submit_envp[], char * const plugin_options[], const char **errstr);
The approval
open
() function is run immediately before a call to the plugin'scheck
() orshow_version
() functions. It is only called if the version is being requested or if the policy plugin'scheck_policy
() function has returned successfully. It returns 1 on success, 0 on failure, -1 if a general error occurred, or -2 if there was a usage error. In the latter case,sudo
will print a usage message before it exits. If an error occurs, the plugin may optionally call theconversation
() orplugin_printf
() function withSUDO_CONF_ERROR_MSG
to present additional error information to the user.The function arguments are as follows:
- version
- The version passed in by
sudo
allows the plugin to determine the major and minor version number of the plugin API supported bysudo
. - conversation
- A pointer to the
conversation
() function that can be used by the plugin to interact with the user (see Conversation API for details). Returns 0 on success and -1 on failure. - plugin_printf
- A pointer to a
printf
()-style function that may be used to display informational or error messages (see Conversation API for details). Returns the number of characters printed on success and -1 on failure. - settings
- A vector of user-supplied
sudo
settings in the form of “name=value” strings. The vector is terminated by aNULL
pointer. These settings correspond to options the user specified when runningsudo
. As such, they will only be present when the corresponding option has been specified on the command line.When parsing settings, the plugin should split on the first equal sign (‘
=
’) since the name field will never include one itself but the value might.See the Policy plugin API section for a list of all possible settings.
- user_info
- A vector of information about the user running the command in the form
of “name=value” strings. The vector is terminated by a
NULL
pointer.When parsing user_info, the plugin should split on the first equal sign (‘
=
’) since the name field will never include one itself but the value might.See the Policy plugin API section for a list of all possible strings.
- submit_optind
- The index into submit_argv that corresponds to
the first entry that is not a command line option. If
submit_argv only consists of options, which may
be the case with the
-l
or-v
options, submit_argv[submit_optind] will evaluate to the NULL pointer. - submit_argv
- The argument vector
sudo
was invoked with, including all command line options. The submit_optind argument can be used to determine the end of the command line options. - submit_envp
- The invoking user's environment in the form of a
NULL
-terminated vector of “name=value” strings.When parsing submit_envp, the plugin should split on the first equal sign (‘
=
’) since the name field will never include one itself but the value might. - plugin_options
- Any (non-comment) strings immediately after the plugin path are
treated as arguments to the plugin. These arguments are split on a
white space boundary and are passed to the plugin in the form of a
NULL
-terminated array of strings. If no arguments were specified, plugin_options will be theNULL
pointer. - errstr
- If the
open
() function returns a value other than 1, the plugin may store a message describing the failure or error in errstr. Thesudo
front-end will then pass this value to any registered audit plugins. The string stored in errstr must remain valid until the plugin'sclose
() function is called.
- close
-
void (*close)(void);
The
close
() function is called after the approval plugin'scheck
() orshow_version
() functions have been called. It takes no arguments. Theclose
() function is typically used to perform plugin-specific cleanup, such as the freeing of memory objects allocated by the plugin. If the plugin does not need to perform any cleanup,close
() may be set to theNULL
pointer. - check
-
int (*check)(char * const command_info[], char * const run_argv[], char * const run_envp[], const char **errstr);
The approval
check
() function is run after the policy plugincheck_policy
() function and before any I/O logging plugins. If multiple approval plugins are loaded, they must all succeed for the command to be allowed. It returns 1 on success, 0 on failure, -1 if a general error occurred, or -2 if there was a usage error. In the latter case,sudo
will print a usage message before it exits. If an error occurs, the plugin may optionally call theconversation
() orplugin_printf
() function withSUDO_CONF_ERROR_MSG
to present additional error information to the user.The function arguments are as follows:
- command_info
- A vector of information describing the command being run in the form
of “name=value” strings. The vector is terminated by a
NULL
pointer.When parsing command_info, the plugin should split on the first equal sign (‘
=
’) since the name field will never include one itself but the value might.See the Policy plugin API section for a list of all possible strings.
- run_argv
- A
NULL
-terminated argument vector describing a command that will be run in the same form as what would be passed to the execve(2) system call. - run_envp
- The environment the command will be run with in the form of a
NULL
-terminated vector of “name=value” strings.When parsing run_envp, the plugin should split on the first equal sign (‘
=
’) since the name field will never include one itself but the value might. - errstr
- If the
open
() function returns a value other than 1, the plugin may store a message describing the failure or error in errstr. Thesudo
front-end will then pass this value to any registered audit plugins. The string stored in errstr must remain valid until the plugin'sclose
() function is called.
- show_version
-
int (*show_version)(int verbose);
The
show_version
() function is called bysudo
when the user specifies the-V
option. The plugin may display its version information to the user via theconversation
() orplugin_printf
() function usingSUDO_CONV_INFO_MSG
. If the user requests detailed version information, the verbose flag will be set.Returns 1 on success, 0 on failure, -1 if a general error occurred, or -2 if there was a usage error, although the return value is currently ignored.
Signal handlers
The sudo
front-end installs default signal
handlers to trap common signals while the plugin functions are run. The
following signals are trapped by default before the command is executed:
If a fatal signal is received before the command is
executed, sudo
will call the plugin's
close
()
function with an exit status of 128 plus the value of the signal that was
received. This allows for consistent logging of commands killed by a signal
for plugins that log such information in their
close
() function. An exception to this is
SIGPIPE
, which is ignored until the command is
executed.
A plugin may temporarily install its own signal handlers but must restore the original handler before the plugin function returns.
Hook function API
Beginning with plugin API version 1.2, it is possible to install
hooks for certain functions called by the sudo
front-end.
Currently, the only supported hooks relate to the handling of
environment variables. Hooks can be used to intercept attempts to get, set,
or remove environment variables so that these changes can be reflected in
the version of the environment that is used to execute a command. A future
version of the API will support hooking internal
sudo
front-end functions as well.
Hook structure
Hooks in sudo
are described by the
following structure:
typedef int (*sudo_hook_fn_t)(); struct sudo_hook { unsigned int hook_version; unsigned int hook_type; sudo_hook_fn_t hook_fn; void *closure; };
A struct sudo_hook has the following fields:
- hook_version
- The hook_version field should be set to
SUDO_HOOK_VERSION
. - hook_type
- The hook_type field may be one of the following
supported hook types:
SUDO_HOOK_SETENV
- The C library setenv(3)
function. Any registered hooks will run before the C library
implementation. The hook_fn field should be a
function that matches the following typedef:
typedef int (*sudo_hook_fn_setenv_t)(const char *name, const char *value, int overwrite, void *closure);
If the registered hook does not match the typedef the results are unspecified.
SUDO_HOOK_UNSETENV
- The C library unsetenv(3)
function. Any registered hooks will run before the C library
implementation. The hook_fn field should be a
function that matches the following typedef:
typedef int (*sudo_hook_fn_unsetenv_t)(const char *name, void *closure);
SUDO_HOOK_GETENV
- The C library getenv(3)
function. Any registered hooks will run before the C library
implementation. The hook_fn field should be a
function that matches the following typedef:
typedef int (*sudo_hook_fn_getenv_t)(const char *name, char **value, void *closure);
If the registered hook does not match the typedef the results are unspecified.
SUDO_HOOK_PUTENV
- The C library putenv(3)
function. Any registered hooks will run before the C library
implementation. The hook_fn field should be a
function that matches the following typedef:
typedef int (*sudo_hook_fn_putenv_t)(char *string, void *closure);
If the registered hook does not match the typedef the results are unspecified.
- hook_fn
-
sudo_hook_fn_t hook_fn;
The hook_fn field should be set to the plugin's hook implementation. The actual function arguments will vary depending on the hook_type (see hook_type above). In all cases, the closure field of struct sudo_hook is passed as the last function parameter. This can be used to pass arbitrary data to the plugin's hook implementation.
The function return value may be one of the following:
SUDO_HOOK_RET_ERROR
- The hook function encountered an error.
SUDO_HOOK_RET_NEXT
- The hook completed without error, go on to the next hook (including
the system implementation if applicable). For example, a
getenv(3) hook might return
SUDO_HOOK_RET_NEXT
if the specified variable was not found in the private copy of the environment. SUDO_HOOK_RET_STOP
- The hook completed without error, stop processing hooks for this invocation. This can be used to replace the system implementation. For example, a setenv hook that operates on a private copy of the environment but leaves environ unchanged.
Care must be taken when hooking C library functions, it is very easy to create an infinite loop. For example, a getenv(3) hook that calls the snprintf(3) function may create a loop if the snprintf(3) implementation calls getenv(3) to check the locale. To prevent this, you may wish to use a static variable in the hook function to guard against nested calls. For example:
static int in_progress = 0; /* avoid recursion */ if (in_progress) return SUDO_HOOK_RET_NEXT; in_progress = 1; ... in_progress = 0; return SUDO_HOOK_RET_STOP;
Hook API Version Macros
/* Hook API version major/minor */ #define SUDO_HOOK_VERSION_MAJOR 1 #define SUDO_HOOK_VERSION_MINOR 0 #define SUDO_HOOK_VERSION SUDO_API_MKVERSION(SUDO_HOOK_VERSION_MAJOR,\ SUDO_HOOK_VERSION_MINOR)
For getters and setters see the Policy plugin API.
Event API
When sudo
runs a command, it uses an event
loop to service signals and I/O. Events may be triggered based on time, a
file or socket descriptor becoming ready, or due to receipt of a signal.
Starting with API version 1.15, it is possible for a plugin to participate
in this event loop by calling the
event_alloc
()
function.
Events are described by the following structure:
typedef void (*sudo_plugin_ev_callback_t)(int fd, int what, void *closure); struct sudo_plugin_event { int (*set)(struct sudo_plugin_event *pev, int fd, int events, sudo_plugin_ev_callback_t callback, void *closure); int (*add)(struct sudo_plugin_event *pev, struct timespec *timeout); int (*del)(struct sudo_plugin_event *pev); int (*pending)(struct sudo_plugin_event *pev, int events, struct timespec *ts); int (*fd)(struct sudo_plugin_event *pev); void (*setbase)(struct sudo_plugin_event *pev, void *base); void (*loopbreak)(struct sudo_plugin_event *pev); void (*free)(struct sudo_plugin_event *pev); };
A struct sudo_plugin_event contains the following function pointers:
- set
-
int (*set)(struct sudo_plugin_event *pev, int fd, int events, sudo_plugin_ev_callback_t callback, void *closure);
The
set
() function takes the following arguments:- struct sudo_plugin_event *pev
- A pointer to the struct sudo_plugin_event itself.
- fd
- The file or socket descriptor for I/O-based events or the signal number for signal events. For time-based events, fd must be -1.
- events
- The following values determine what will trigger the event callback:
SUDO_PLUGIN_EV_TIMEOUT
- callback is run after the specified timeout expires
SUDO_PLUGIN_EV_READ
- callback is run when the file descriptor is readable
SUDO_PLUGIN_EV_WRITE
- callback is run when the file descriptor is writable
SUDO_PLUGIN_EV_PERSIST
- event is persistent and remains enabled until explicitly deleted
SUDO_PLUGIN_EV_SIGNAL
- callback is run when the specified signal is received
The
SUDO_PLUGIN_EV_PERSIST
flag may be ORed with any of the event types. It is also possible to ORSUDO_PLUGIN_EV_READ
andSUDO_PLUGIN_EV_WRITE
together to run the callback when a descriptor is ready to be either read from or written to. All other event values are mutually exclusive. - sudo_plugin_ev_callback_t callback
-
typedef void (*sudo_plugin_ev_callback_t)(int fd, int what, void *closure);
The function to call when an event is triggered. The
callback
() function is run with the following arguments:- fd
- The file or socket descriptor for I/O-based events or the signal number for signal events.
- what
- The event type that triggered that callback. For events that have
multiple event types (for example
SUDO_PLUGIN_EV_READ
andSUDO_PLUGIN_EV_WRITE
) or have an associated timeout, what can be used to determine why the callback was run. - closure
- The generic pointer that was specified in the
set
() function.
- closure
- A generic pointer that will be passed to the callback function.
The
set
() function returns 1 on success, and -1 if a error occurred. - add
-
int (*add)(struct sudo_plugin_event *pev, struct timespec *timeout);
The
add
() function adds the event pev tosudo
's event loop. The event must have previously been initialized via theset
() function. If the timeout argument is not NULL, it should specify a (relative) timeout after which the event will be triggered if the main event criteria has not been met. This is often used to implement an I/O timeout where the event will fire if a descriptor is not ready within a certain time period. If the event is already present in the event loop, its timeout will be adjusted to match the new value, if any.The
add
() function returns 1 on success, and -1 if a error occurred. - del
-
int (*del)(struct sudo_plugin_event *pev);
The
del
() function deletes the event pev fromsudo
's event loop. Deleted events can be added back via theadd
() function.The
del
() function returns 1 on success, and -1 if a error occurred. - pending
-
int (*pending)(struct sudo_plugin_event *pev, int events, struct timespec *ts);
The
pending
() function can be used to determine whether one or more events is pending. The events argument specifies which events to check for. See theset
() function for a list of valid event types. IfSUDO_PLUGIN_EV_TIMEOUT
is specified in events, the event has an associated timeout and the ts pointer is non-NULL, it will be filled in with the remaining time. - fd
-
int (*fd)(struct sudo_plugin_event *pev);
The
fd
() function returns the descriptor or signal number associated with the event pev. - setbase
-
void (*setbase)(struct sudo_plugin_event *pev, void *base);
The
setbase
() function sets the underlying event base for pev to the specified value. This can be used to move an event created viaevent_alloc
() to a new event loop allocated by sudo's event subsystem. If base isNULL
, pev's event base is reset to the default value, which corresponds tosudo
's main event loop. Using this function requires linking the plugin with the sudo_util library. It is unlikely to be used outside of thesudoers
plugin. - loopbreak
-
void (*loopbreak)(struct sudo_plugin_event *pev);
The
loopbreak
() function causessudo
's event loop to exit immediately and the running command to be terminated. - free
-
void (*free)(struct sudo_plugin_event *pev);
The
free
() function deletes the event pev from the event loop and frees the memory associated with it.
Remote command execution
The sudo
front-end does not support
running remote commands. However, starting with sudo
1.8.8, the -h
option may be used to specify a remote
host that is passed to the policy plugin. A plugin may also accept a
runas_user in the form of “user@hostname”
which will work with older versions of sudo
. It is
anticipated that remote commands will be supported by executing a
“helper” program. The policy plugin should setup the execution
environment such that the sudo
front-end will run
the helper which, in turn, will connect to the remote host and run the
command.
For example, the policy plugin could utilize
ssh
to perform remote command execution. The helper
program would be responsible for running ssh
with
the proper options to use a private key or certificate that the remote host
will accept and run a program on the remote host that would setup the
execution environment accordingly.
Remote sudoedit
functionality must be
handled by the policy plugin, not sudo
itself as the
front-end has no knowledge that a remote command is being executed. This may
be addressed in a future revision of the plugin API.
Conversation API
If the plugin needs to interact with the user, it may do so via
the
conversation
()
function. A plugin should not attempt to read directly from the standard
input or the user's terminal (neither of which are guaranteed to exist). The
caller must include a trailing newline in msg if one
is to be printed.
A
printf
()-style
function is also available that can be used to display informational or
error messages to the user, which is usually more convenient for simple
messages where no use input is required.
Conversation function structures
The conversation function takes as arguments pointers to the following structures:
struct sudo_conv_message { #define SUDO_CONV_PROMPT_ECHO_OFF 0x0001 /* do not echo user input */ #define SUDO_CONV_PROMPT_ECHO_ON 0x0002 /* echo user input */ #define SUDO_CONV_ERROR_MSG 0x0003 /* error message */ #define SUDO_CONV_INFO_MSG 0x0004 /* informational message */ #define SUDO_CONV_PROMPT_MASK 0x0005 /* mask user input */ #define SUDO_CONV_PROMPT_ECHO_OK 0x1000 /* flag: allow echo if no tty */ #define SUDO_CONV_PREFER_TTY 0x2000 /* flag: use tty if possible */ int msg_type; int timeout; const char *msg; }; #define SUDO_CONV_REPL_MAX 1023 struct sudo_conv_reply { char *reply; }; typedef int (*sudo_conv_callback_fn_t)(int signo, void *closure); struct sudo_conv_callback { unsigned int version; void *closure; sudo_conv_callback_fn_t on_suspend; sudo_conv_callback_fn_t on_resume; };
Pointers to the
conversation
()
and printf
()-style functions are passed in to the
plugin's open
() function when the plugin is
initialized. The following type definitions can be used in the declaration
of the open
() function:
typedef int (*sudo_conv_t)(int num_msgs, const struct sudo_conv_message msgs[], struct sudo_conv_reply replies[], struct sudo_conv_callback *callback); typedef int (*sudo_printf_t)(int msg_type, const char * restrict fmt, ...);
To use the
conversation
()
function, the plugin must pass an array of struct
sudo_conv_message and struct sudo_conv_reply.
There must be a struct sudo_conv_message and
struct sudo_conv_reply for each message in the
conversation, that is, both arrays must have the same number of elements.
Each struct sudo_conv_reply must have its
reply member initialized to
NULL
. The struct
sudo_conv_callback pointer, if not NULL
,
should contain function pointers to be called when the
sudo
process is suspended and/or resumed during
conversation input. The on_suspend and
on_resume functions are called with the signal that
caused sudo
to be suspended and the
closure pointer from the struct
sudo_conv_callback. These functions should return 0 on success and -1
on error. On error, the conversation will end and the conversation function
will return a value of -1. The intended use is to allow the plugin to
release resources, such as locks, that should not be held indefinitely while
suspended and then reacquire them when the process is resumed. The functions
are not actually invoked from within a signal handler.
The msg_type must be set to one of the following values:
SUDO_CONV_PROMPT_ECHO_OFF
- Prompt the user for input with echo disabled; this is generally used for
passwords. The reply will be stored in the replies
array, and it will never be
NULL
. SUDO_CONV_PROMPT_ECHO_ON
- Prompt the user for input with echo enabled. The reply will be stored in
the replies array, and it will never be
NULL
. SUDO_CONV_ERROR_MSG
- Display an error message. The message is written to the standard error
unless the
SUDO_CONV_PREFER_TTY
flag is set, in which case it is written to the user's terminal if possible. SUDO_CONV_INFO_MSG
- Display a message. The message is written to the standard output unless
the
SUDO_CONV_PREFER_TTY
flag is set, in which case it is written to the user's terminal if possible. SUDO_CONV_PROMPT_MASK
- Prompt the user for input but echo an asterisk character for each
character read. The reply will be stored in the
replies array, and it will never be
NULL
. This can be used to provide visual feedback to the user while reading sensitive information that should not be displayed.
In addition to the above values, the following flag bits may also be set:
SUDO_CONV_PROMPT_ECHO_OK
- Allow input to be read when echo cannot be disabled when the message type
is
SUDO_CONV_PROMPT_ECHO_OFF
orSUDO_CONV_PROMPT_MASK
. By default,sudo
will refuse to read input if the echo cannot be disabled for those message types. SUDO_CONV_PREFER_TTY
- When displaying a message via
SUDO_CONV_ERROR_MSG
orSUDO_CONV_INFO_MSG
, try to write the message to the user's terminal. If the terminal is unavailable, the standard error or standard output will be used, depending upon whetherSUDO_CONV_ERROR_MSG
orSUDO_CONV_INFO_MSG
was used. The user's terminal is always used when possible for input, this flag is only used for output.
The timeout in seconds until the prompt will wait for no more input. A zero value implies an infinite timeout.
The plugin is responsible for freeing the reply buffer located in
each struct sudo_conv_reply, if it is not
NULL
. SUDO_CONV_REPL_MAX
represents the maximum length of the reply buffer (not including the
trailing NUL character). In practical terms, this is the longest password
sudo
will support.
The
printf
()-style
function uses the same underlying mechanism as the
conversation
() function but only supports
SUDO_CONV_INFO_MSG
and
SUDO_CONV_ERROR_MSG
for the
msg_type parameter. It can be more convenient than
using the conversation
() function if no user reply
is needed and supports standard printf
() escape
sequences.
See the sample plugin for an example of the
conversation
()
function usage.
Plugin invocation order
As of sudo
1.9.0, the plugin
open
() and close
() functions
are called in the following order:
- audit open
- policy open
- approval open
- approval close
- I/O log open
- command runs
- command exits
- I/O log close
- policy close
- audit close
- sudo exits
Prior to sudo
1.9.0, the I/O
log close
()
function was called
after
the policy close
() function.
Sudoers group plugin API
The sudoers
plugin supports its own plugin
interface to allow non-Unix group lookups. This can be used to query a group
source other than the standard Unix group database. Two sample group plugins
are bundled with sudo
,
group_file,
and
system_group,
are detailed in sudoers(5). Third
party group plugins include a QAS AD plugin available from Quest
Software.
A group plugin must declare and populate a struct sudoers_group_plugin in the global scope. This structure contains pointers to the functions that implement plugin initialization, cleanup, and group lookup.
struct sudoers_group_plugin { unsigned int version; int (*init)(int version, sudo_printf_t sudo_plugin_printf, char *const argv[]); void (*cleanup)(void); int (*query)(const char *user, const char *group, const struct passwd *pwd); };
A struct sudoers_group_plugin has the following fields:
- version
- The version field should be set to
GROUP_API_VERSION.
This allows
sudoers
to determine the API version the group plugin was built against. - init
-
int (*init)(int version, sudo_printf_t sudo_plugin_printf, char *const argv[]);
The
init
() function is called after sudoers has been parsed but before any policy checks. It returns 1 on success, 0 on failure (or if the plugin is not configured), and -1 if a error occurred. If an error occurs, the plugin may call theplugin_printf
() function withSUDO_CONF_ERROR_MSG
to present additional error information to the user.The function arguments are as follows:
- version
- The version passed in by
sudoers
allows the plugin to determine the major and minor version number of the group plugin API supported bysudoers
. - plugin_printf
- A pointer to a
printf
()-style function that may be used to display informational or error message to the user. Returns the number of characters printed on success and -1 on failure. - argv
- A
NULL
-terminated array of arguments generated from the group_plugin option in sudoers. If no arguments were given, argv will beNULL
.
- cleanup
-
void (*cleanup)();
The
cleanup
() function is called whensudoers
has finished its group checks. The plugin should free any memory it has allocated and close open file handles. - query
-
int (*query)(const char *user, const char *group, const struct passwd *pwd);
The
query
() function is used to ask the group plugin whether user is a member of group.The function arguments are as follows:
- user
- The name of the user being looked up in the external group database.
- group
- The name of the group being queried.
- pwd
- The password database entry for user, if any. If
user is not present in the password database,
pwd will be
NULL
.
/* Sudoers group plugin version major/minor */ #define GROUP_API_VERSION_MAJOR 1 #define GROUP_API_VERSION_MINOR 0 #define GROUP_API_VERSION ((GROUP_API_VERSION_MAJOR << 16) | \ GROUP_API_VERSION_MINOR)
PLUGIN API CHANGELOG
The following revisions have been made to the Sudo Plugin API.
- Version 1.0
- Initial API version.
- Version 1.1 (sudo 1.8.0)
- The I/O logging plugin's
open
() function was modified to take the command_info list as an argument. - Version 1.2 (sudo 1.8.5)
- The Policy and I/O logging plugins'
open
() functions are now passed a list of plugin parameters if any are specified in sudo.conf(5).A simple hooks API has been introduced to allow plugins to hook in to the system's environment handling functions.
The
init_session
() Policy plugin function is now passed a pointer to the user environment which can be updated as needed. This can be used to merge in environment variables stored in the PAM handle before a command is run. - Version 1.3 (sudo 1.8.7)
- Support for the exec_background entry has been added to
the command_info list.
The max_groups and plugin_dir entries were added to the settings list.
The
version
() andclose
() functions are now optional. Previously, a missingversion
() orclose
() function would result in a crash. If no policy pluginclose
() function is defined, a defaultclose
() function will be provided by thesudo
front-end that displays a warning if the command could not be executed.The
sudo
front-end now installs default signal handlers to trap common signals while the plugin functions are run. - Version 1.4 (sudo 1.8.8)
- The remote_host entry was added to the settings list.
- Version 1.5 (sudo 1.8.9)
- The preserve_fds entry was added to the command_info list.
- Version 1.6 (sudo 1.8.11)
- The behavior when an I/O logging plugin returns an error (-1) has changed.
Previously, the
sudo
front-end took no action when thelog_ttyin
(),log_ttyout
(),log_stdin
(),log_stdout
(), orlog_stderr
() function returned an error.The behavior when an I/O logging plugin returns 0 has changed. Previously, output from the command would be displayed to the terminal even if an output logging function returned 0.
- Version 1.7 (sudo 1.8.12)
- The
plugin_path
entry was added to the settings list.
The debug_flags entry now starts with a debug file path name and may occur multiple times if there are multiple plugin-specific Debug lines in the sudo.conf(5) file.
- Version 1.8 (sudo 1.8.15)
- The sudoedit_checkdir and
sudoedit_follow entries were added to the
command_info list. The default value of
sudoedit_checkdir was changed to true in sudo 1.8.16.
The sudo
conversation
() function now takes a pointer to a struct sudo_conv_callback as its fourth argument. The sudo_conv_t definition has been updated to match. The plugin must specify that it supports plugin API version 1.8 or higher to receive a conversation function pointer that supports this argument. - Version 1.9 (sudo 1.8.16)
- The execfd entry was added to the command_info list.
- Version 1.10 (sudo 1.8.19)
- The umask entry was added to the user_info list. The iolog_group, iolog_mode, and iolog_user entries were added to the command_info list.
- Version 1.11 (sudo 1.8.20)
- The timeout entry was added to the settings list.
- Version 1.12 (sudo 1.8.21)
- The
change_winsize
() function was added to struct io_plugin. - Version 1.13 (sudo 1.8.26)
- The
log_suspend
() function was added to struct io_plugin. - Version 1.14 (sudo 1.8.29)
- The umask_override entry was added to the command_info list.
- Version 1.15 (sudo 1.9.0)
- The cwd_optional entry was added to the
command_info list.
The
event_alloc
() function was added to struct policy_plugin and struct io_plugin.The errstr argument was added to the policy and I/O plugin functions which the plugin function can use to return an error string. This string may be used by the audit plugin to report failure or error conditions set by the other plugins.
The
close
() function is now is called regardless of whether or not a command was actually executed. This makes it possible for plugins to perform cleanup even when a command was not run.SUDO_CONV_REPL_MAX
has increased from 255 to 1023 bytes.Support for audit and approval plugins was added.
- Version 1.16 (sudo 1.9.3)
- Initial resource limit values were added to the
user_info list.
The cmnd_chroot and cmnd_cwd entries were added to the settings list.
- Version 1.17 (sudo 1.9.4)
- The
event_alloc
() function was added to struct audit_plugin and struct approval_plugin. - Version 1.18 (sudo 1.9.9)
- The policy may now set resource limit values in the command_info list. The intercept and log_subcmds entries were added to the command_info list.
- Version 1.19 (sudo 1.9.11)
- The intercept_ptrace and intercept_setid entries were added to the settings list. The apparmor_profile and use_ptrace entries were added to the command_info list.
- Version 1.20 (sudo 1.9.12)
- The update_ticket entry was added to the settings list. The intercept_verify entry was added to the command_info list.
- Version 1.21 (sudo 1.9.13)
- The sudoedit_nfiles entry was added to the command_info list.
- Version 1.22 (sudo 1.9.16)
- The ttydev entry was added to the user_info list.
SEE ALSO
AUTHORS
Many people have worked on sudo
over the
years; this version consists of code written primarily by:
See the CONTRIBUTORS.md file in the sudo
distribution (https://www.sudo.ws/about/contributors/) for an exhaustive
list of people who have contributed to sudo
.
BUGS
If you believe you have found a bug in
sudo_plugin
, you can either file a bug report in the
sudo bug database, https://bugzilla.sudo.ws/, or open an issue at
https://github.com/sudo-project/sudo/issues. If you would prefer to use
email, messages may be sent to the sudo-workers mailing list,
https://www.sudo.ws/mailman/listinfo/sudo-workers (public) or
<sudo@sudo.ws> (private).
Please not report security vulnerabilities through public GitHub issues, Bugzilla or mailing lists. Instead, report them via email to <Todd.Miller@sudo.ws>. You may encrypt your message with PGP if you would like, using the key found at https://www.sudo.ws/dist/PGPKEYS.
SUPPORT
Limited free support is available via the sudo-users mailing list, see https://www.sudo.ws/mailman/listinfo/sudo-users to subscribe or search the archives.
DISCLAIMER
sudo
is provided “AS IS” and
any express or implied warranties, including, but not limited to, the
implied warranties of merchantability and fitness for a particular purpose
are disclaimed. See the LICENSE.md file distributed with
sudo
or https://www.sudo.ws/about/license/ for
complete details.
August 14, 2024 | Sudo 1.9.16 |