.\" $OpenBSD: X509_VERIFY_PARAM_set_flags.3,v 1.29 2023/04/30 19:40:23 tb Exp $
.\" full merge up to: OpenSSL d33def66 Feb 9 14:17:13 2016 -0500
.\" selective merge up to: OpenSSL 24a535ea Sep 22 13:14:20 2020 +0100
.\"
.\" This file is a derived work.
.\" The changes are covered by the following Copyright and license:
.\"
.\" Copyright (c) 2018, 2021, 2022 Ingo Schwarze <schwarze@openbsd.org>
.\"
.\" Permission to use, copy, modify, and distribute this software for any
.\" purpose with or without fee is hereby granted, provided that the above
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.\" OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
.\"
.\" The original file was written by Dr. Stephen Henson <steve@openssl.org>
.\" and Viktor Dukhovni <viktor@dukhovni.org>.
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.\" All rights reserved.
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.Dd $Mdocdate: April 30 2023 $
.Dt X509_VERIFY_PARAM_SET_FLAGS 3
.Os
.Sh NAME
.Nm X509_VERIFY_PARAM_get0_name ,
.Nm X509_VERIFY_PARAM_set1_name ,
.Nm X509_VERIFY_PARAM_set_flags ,
.Nm X509_VERIFY_PARAM_clear_flags ,
.Nm X509_VERIFY_PARAM_get_flags ,
.Nm X509_VERIFY_PARAM_set_purpose ,
.Nm X509_VERIFY_PARAM_set_trust ,
.Nm X509_VERIFY_PARAM_set_time ,
.Nm X509_VERIFY_PARAM_get_time ,
.Nm X509_VERIFY_PARAM_add0_policy ,
.Nm X509_VERIFY_PARAM_set1_policies ,
.Nm X509_VERIFY_PARAM_set_depth ,
.Nm X509_VERIFY_PARAM_get_depth ,
.Nm X509_VERIFY_PARAM_set_auth_level ,
.Nm X509_VERIFY_PARAM_set1_host ,
.Nm X509_VERIFY_PARAM_add1_host ,
.Nm X509_VERIFY_PARAM_set_hostflags ,
.Nm X509_VERIFY_PARAM_get0_peername ,
.Nm X509_VERIFY_PARAM_set1_email ,
.Nm X509_VERIFY_PARAM_set1_ip ,
.Nm X509_VERIFY_PARAM_set1_ip_asc
.Nd X509 verification parameters
.Sh SYNOPSIS
.In openssl/x509_vfy.h
.Ft const char *
.Fo X509_VERIFY_PARAM_get0_name
.Fa "const X509_VERIFY_PARAM *param"
.Fc
.Ft int
.Fo X509_VERIFY_PARAM_set1_name
.Fa "X509_VERIFY_PARAM *param"
.Fa "const char *name"
.Fc
.Ft int
.Fo X509_VERIFY_PARAM_set_flags
.Fa "X509_VERIFY_PARAM *param"
.Fa "unsigned long flags"
.Fc
.Ft int
.Fo X509_VERIFY_PARAM_clear_flags
.Fa "X509_VERIFY_PARAM *param"
.Fa "unsigned long flags"
.Fc
.Ft unsigned long
.Fo X509_VERIFY_PARAM_get_flags
.Fa "X509_VERIFY_PARAM *param"
.Fc
.Ft int
.Fo X509_VERIFY_PARAM_set_purpose
.Fa "X509_VERIFY_PARAM *param"
.Fa "int purpose"
.Fc
.Ft int
.Fo X509_VERIFY_PARAM_set_trust
.Fa "X509_VERIFY_PARAM *param"
.Fa "int trust"
.Fc
.Ft void
.Fo X509_VERIFY_PARAM_set_time
.Fa "X509_VERIFY_PARAM *param"
.Fa "time_t t"
.Fc
.Ft time_t
.Fo X509_VERIFY_PARAM_get_time
.Fa const X509_VERIFY_PARAM *param"
.Fc
.Ft int
.Fo X509_VERIFY_PARAM_add0_policy
.Fa "X509_VERIFY_PARAM *param"
.Fa "ASN1_OBJECT *policy"
.Fc
.Ft int
.Fo X509_VERIFY_PARAM_set1_policies
.Fa "X509_VERIFY_PARAM *param"
.Fa "STACK_OF(ASN1_OBJECT) *policies"
.Fc
.Ft void
.Fo X509_VERIFY_PARAM_set_depth
.Fa "X509_VERIFY_PARAM *param"
.Fa "int depth"
.Fc
.Ft int
.Fo X509_VERIFY_PARAM_get_depth
.Fa "const X509_VERIFY_PARAM *param"
.Fc
.Ft void
.Fo X509_VERIFY_PARAM_set_auth_level
.Fa "X509_VERIFY_PARAM *param"
.Fa "int auth_level"
.Fc
.Ft int
.Fo X509_VERIFY_PARAM_set1_host
.Fa "X509_VERIFY_PARAM *param"
.Fa "const char *name"
.Fa "size_t namelen"
.Fc
.Ft int
.Fo X509_VERIFY_PARAM_add1_host
.Fa "X509_VERIFY_PARAM *param"
.Fa "const char *name"
.Fa "size_t namelen"
.Fc
.Ft void
.Fo X509_VERIFY_PARAM_set_hostflags
.Fa "X509_VERIFY_PARAM *param"
.Fa "unsigned int flags"
.Fc
.Ft char *
.Fo X509_VERIFY_PARAM_get0_peername
.Fa "X509_VERIFY_PARAM *param"
.Fc
.Ft int
.Fo X509_VERIFY_PARAM_set1_email
.Fa "X509_VERIFY_PARAM *param"
.Fa "const char *email"
.Fa "size_t emaillen"
.Fc
.Ft int
.Fo X509_VERIFY_PARAM_set1_ip
.Fa "X509_VERIFY_PARAM *param"
.Fa "const unsigned char *ip"
.Fa "size_t iplen"
.Fc
.Ft int
.Fo X509_VERIFY_PARAM_set1_ip_asc
.Fa "X509_VERIFY_PARAM *param"
.Fa "const char *ipasc"
.Fc
.Sh DESCRIPTION
These functions manipulate an
.Vt X509_VERIFY_PARAM
object associated with a certificate verification operation.
.Pp
.Fn X509_VERIFY_PARAM_get0_name
returns the name of the given
.Fa param
object, usually describing its purpose, for example
.Qq default ,
.Qq pkcs7 ,
.Qq smime_sign ,
.Qq ssl_client ,
or
.Qq ssl_server .
For user-defined objects, the returned pointer may be
.Dv NULL
even if the object is otherwise valid.
.Pp
.Fn X509_VERIFY_PARAM_set1_name
sets the name of
.Fa param
to a copy of
.Fa name ,
or to
.Dv NULL
if
.Fa name
is
.Dv NULL .
.Pp
.Fn X509_VERIFY_PARAM_set_flags
sets the flags in
.Fa param
by OR'ing it with
.Fa flags .
See the
.Sx VERIFICATION FLAGS
section for a complete description of values the
.Fa flags
parameter can take.
.Pp
If the
.Fa flags
argument includes any of the flags contained in
.Dv X509_V_FLAG_POLICY_MASK ,
that is, any of
.Dv X509_V_FLAG_POLICY_CHECK ,
.Dv X509_V_FLAG_EXPLICIT_POLICY ,
.Dv X509_V_FLAG_INHIBIT_ANY ,
and
.Dv X509_V_FLAG_INHIBIT_MAP ,
then
.Dv X509_V_FLAG_POLICY_CHECK
is set in addition to the flags contained in the
.Fa flags
argument.
.Pp
.Fn X509_VERIFY_PARAM_get_flags
returns the flags in
.Fa param .
.Pp
.Fn X509_VERIFY_PARAM_clear_flags
clears the specified
.Fa flags
in
.Fa param .
.Pp
Calling this function can result in unusual internal states of the
.Fa param
object, for example having a verification time configured but having
.Dv X509_V_FLAG_USE_CHECK_TIME
unset, or having
.Dv X509_V_FLAG_EXPLICIT_POLICY
set but
.Dv X509_V_FLAG_POLICY_CHECK
unset, which may have surprising effects.
.Pp
.Fn X509_VERIFY_PARAM_set_purpose
sets the verification
.Fa purpose
identifier in
.Fa param .
This determines the acceptable purpose of the certificate chain, for example
.Dv X509_PURPOSE_SSL_CLIENT
or
.Dv X509_PURPOSE_SSL_SERVER .
Standard purposes are listed in
.Xr X509_check_purpose 3 ,
and additional purposes can be defined with
.Xr X509_PURPOSE_add 3 .
.Pp
.Fn X509_VERIFY_PARAM_set_trust
sets the trust setting in
.Fa param
to
.Fa trust .
.Pp
.Fn X509_VERIFY_PARAM_set_time
sets the flag
.Dv X509_V_FLAG_USE_CHECK_TIME
in
.Fa param
in addition to the flags already set and sets the verification time to
.Fa t .
If this function is not called, the current time is used instead,
or the UNIX Epoch (January 1, 1970) if
.Dv X509_V_FLAG_USE_CHECK_TIME
is manually set using
.Fn X509_VERIFY_PARAM_set_flags .
.Pp
.Fn X509_VERIFY_PARAM_add0_policy
enables policy checking (it is disabled by default) and adds
.Fa policy
to the acceptable policy set.
.Pp
.Fn X509_VERIFY_PARAM_set1_policies
enables policy checking (it is disabled by default) and sets the
acceptable policy set to
.Fa policies .
Any existing policy set is cleared.
The
.Fa policies
parameter can be
.Dv NULL
to clear an existing policy set.
.Pp
.Fn X509_VERIFY_PARAM_set_depth
sets the maximum verification depth to
.Fa depth .
That is the maximum number of untrusted CA certificates that can appear
in a chain.
.Pp
.Fn X509_VERIFY_PARAM_set_auth_level
sets the security level as defined in
.Xr SSL_CTX_set_security_level 3
for certificate chain validation.
For a certificate chain to validate, the public keys of all the
certificates must meet the specified security level.
The signature algorithm security level is not enforced for the
chain's trust anchor certificate, which is either directly trusted
or validated by means other than its signature.
.Pp
From the point of view of the X.509 library,
the default security level is 0.
However, the SSL library
uses a different default security level of 1 and calls
.Fn X509_VERIFY_PARAM_set_auth_level
with its own level before validating a certificate chain.
.Pp
.Fn X509_VERIFY_PARAM_set1_host
sets the expected DNS hostname to
.Fa name
clearing any previously specified hostname or names.
If
.Fa name
is
.Dv NULL
or empty, the list of hostnames is cleared, and name checks are not
performed on the peer certificate.
.Fa namelen
should be set to the length of
.Fa name .
For historical compatibility, if
.Fa name
is NUL-terminated,
.Fa namelen
may be specified as zero.
When a hostname is specified, certificate verification automatically
invokes
.Xr X509_check_host 3
with flags equal to the
.Fa flags
argument given to
.Fn X509_VERIFY_PARAM_set_hostflags
(default zero).
.Fn X509_VERIFY_PARAM_set1_host
will fail if
.Fa name
contains any embedded 0 bytes.
.Pp
.Fn X509_VERIFY_PARAM_add1_host
adds
.Fa name
as an additional reference identifier that can match the peer's
certificate.
Any previous names set via
.Fn X509_VERIFY_PARAM_set1_host
and
.Fn X509_VERIFY_PARAM_add1_host
are retained.
No change is made if
.Fa name
is
.Dv NULL
or empty.
.Fa namelen
should be set to the length of
.Fa name .
For historical compatibility, if
.Fa name
is NUL-terminated,
.Fa namelen
may be specified as zero.
.Fn X509_VERIFY_PARAM_add1_host
will fail if
.Fa name
contains any embedded 0 bytes.
When multiple names are configured, the peer is considered verified when
any name matches.
.Pp
.Fn X509_VERIFY_PARAM_get0_peername
returns the DNS hostname or subject CommonName from the peer certificate
that matched one of the reference identifiers.
When wildcard matching is not disabled, or when a reference identifier
specifies a parent domain (starts with ".") rather than a hostname, the
peer name may be a wildcard name or a sub-domain of the reference
identifier respectively.
.Pp
.Fn X509_VERIFY_PARAM_set1_email
sets the expected RFC 822 email address to
.Fa email .
.Fa emaillen
should be set to the length of
.Fa email .
For historical compatibility, if
.Fa email
is NUL-terminated,
.Fa emaillen
may be specified as zero,
.Fn X509_VERIFY_PARAM_set1_email
will fail if
.Fa email
is NULL, an empty string, or contains embedded 0 bytes.
When an email address is specified, certificate verification
automatically invokes
.Xr X509_check_email 3 .
.Pp
.Fn X509_VERIFY_PARAM_set1_ip
sets the expected IP address to
.Fa ip .
The
.Fa ip
argument is in binary format, in network byte-order, and
.Fa iplen
must be set to 4 for IPv4 and 16 for IPv6.
.Fn X509_VERIFY_PARAM_set1_ip
will fail if
.Fa ip
is NULL or if
.Fa iplen
is not 4 or 16.
When an IP address is specified,
certificate verification automatically invokes
.Xr X509_check_ip 3 .
.Pp
.Fn X509_VERIFY_PARAM_set1_ip_asc
sets the expected IP address to
.Fa ipasc .
The
.Fa ipasc
argument is a NUL-terminal ASCII string:
dotted decimal quad for IPv4 and colon-separated hexadecimal for IPv6.
The condensed "::" notation is supported for IPv6 addresses.
.Fn X509_VERIFY_PARAM_set1_ip_asc
will fail if
.Fa ipasc
is unparsable.
.Sh RETURN VALUES
.Fn X509_VERIFY_PARAM_set1_name ,
.Fn X509_VERIFY_PARAM_set_flags ,
.Fn X509_VERIFY_PARAM_clear_flags ,
.Fn X509_VERIFY_PARAM_set_purpose ,
.Fn X509_VERIFY_PARAM_set_trust ,
.Fn X509_VERIFY_PARAM_add0_policy ,
and
.Fn X509_VERIFY_PARAM_set1_policies
return 1 for success or 0 for failure.
.Pp
.Fn X509_VERIFY_PARAM_set1_host ,
.Fn X509_VERIFY_PARAM_add1_host ,
.Fn X509_VERIFY_PARAM_set1_email ,
.Fn X509_VERIFY_PARAM_set1_ip ,
and
.Fn X509_VERIFY_PARAM_set1_ip_asc
return 1 for success or 0 for failure.
A failure from these routines will poison
the
.Vt X509_VERIFY_PARAM
object so that future calls to
.Xr X509_verify_cert 3
using the poisoned object will fail.
.Pp
.Fn X509_VERIFY_PARAM_get_flags
returns the current verification flags.
.Pp
.Fn X509_VERIFY_PARAM_get_time
always returns the configured verification time.
It does so even if the returned time will not be used because the flag
.Dv X509_V_FLAG_USE_CHECK_TIME
is unset.
.Pp
.Fn X509_VERIFY_PARAM_get_depth
returns the current verification depth.
.Pp
.Fn X509_VERIFY_PARAM_get0_name
and
.Fn X509_VERIFY_PARAM_get0_peername
return pointers to strings that are only valid
during the lifetime of the given
.Fa param
object and that must not be freed by the application program.
.Sh VERIFICATION FLAGS
The verification flags consists of zero or more of the following
flags OR'ed together.
.Pp
.Dv X509_V_FLAG_CRL_CHECK
enables CRL checking for the certificate chain leaf certificate.
An error occurs if a suitable CRL cannot be found.
.Pp
.Dv X509_V_FLAG_CRL_CHECK_ALL
enables CRL checking for the entire certificate chain.
.Pp
.Dv X509_V_FLAG_IGNORE_CRITICAL
disables critical extension checking.
By default any unhandled critical extensions in certificates or (if
checked) CRLs results in a fatal error.
If this flag is set, unhandled critical extensions are ignored.
.Sy WARNING :
setting this option for anything other than debugging purposes can be a
security risk.
Finer control over which extensions are supported can be performed in
the verification callback.
.Pp
The
.Dv X509_V_FLAG_X509_STRICT
flag disables workarounds for some broken certificates and makes the
verification strictly apply X509 rules.
.Pp
.Dv X509_V_FLAG_ALLOW_PROXY_CERTS
deprecated flag that used to
enable proxy certificate verification.
In LibreSSL, this flag has no effect.
.Pp
.Dv X509_V_FLAG_POLICY_CHECK
enables certificate policy checking; by default no policy checking is
performed.
Additional information is sent to the verification callback relating to
policy checking.
.Pp
.Dv X509_V_FLAG_EXPLICIT_POLICY ,
.Dv X509_V_FLAG_INHIBIT_ANY ,
and
.Dv X509_V_FLAG_INHIBIT_MAP
set the
.Dq require explicit policy ,
.Dq inhibit any policy ,
and
.Dq inhibit policy mapping
flags, respectively, as defined in RFC 3280.
These three flags are ignored unless
.Dv X509_V_FLAG_POLICY_CHECK
is also set.
.Pp
If
.Dv X509_V_FLAG_NOTIFY_POLICY
is set and policy checking is successful, a special status code is
sent to the verification callback.
.Pp
By default some additional features such as indirect CRLs and CRLs
signed by different keys are disabled.
If
.Dv X509_V_FLAG_EXTENDED_CRL_SUPPORT
is set, they are enabled.
.Pp
If
.Dv X509_V_FLAG_USE_DELTAS
is set, delta CRLs (if present) are used to determine certificate
status.
If not set, deltas are ignored.
.Pp
.Dv X509_V_FLAG_CHECK_SS_SIGNATURE
enables checking of the root CA self signed certificate signature.
By default this check is disabled because it doesn't add any additional
security but in some cases applications might want to check the
signature anyway.
A side effect of not checking the root CA signature is that disabled or
unsupported message digests on the root CA are not treated as fatal
errors.
.Pp
The deprecated
.Dv X509_V_FLAG_CB_ISSUER_CHECK
flag used to enable debugging of certificate issuer checks.
It is provided for binary backwards compatibility and has no effect.
.Pp
When
.Dv X509_V_FLAG_TRUSTED_FIRST
is set, construction of the certificate chain in
.Xr X509_verify_cert 3
will search the trust store for issuer certificates before searching the
provided untrusted certificates.
Local issuer certificates are often more likely to satisfy local
security requirements and lead to a locally trusted root.
This is especially important when some certificates in the trust store
have explicit trust settings; see the trust settings options of the
.Cm x509
command in
.Xr openssl 1 .
.Pp
The
.Dv X509_V_FLAG_NO_ALT_CHAINS
flag suppresses checking for alternative chains.
By default, unless
.Dv X509_V_FLAG_TRUSTED_FIRST
is set, when building a certificate chain, if the first certificate
chain found is not trusted, then OpenSSL will attempt to replace
untrusted certificates supplied by the peer with certificates from the
trust store to see if an alternative chain can be found that is trusted.
.Pp
The
.Dv X509_V_FLAG_PARTIAL_CHAIN
flag causes intermediate certificates in the trust store to be treated
as trust-anchors, in the same way as the self-signed root CA
certificates.
This makes it possible to trust certificates issued by an intermediate
CA without having to trust its ancestor root CA.
.Pp
If
.Dv X509_V_FLAG_USE_CHECK_TIME
is set, the validity period of certificates and CRLs is checked.
In this case,
.Dv X509_V_FLAG_NO_CHECK_TIME
is ignored.
If the validation time was set with
.Fn X509_VERIFY_PARAM_set_time ,
that time is used.
If
.Fn X509_VERIFY_PARAM_set_time
was not called, the UNIX Epoch (January 1, 1970) is used.
.Pp
If neither
.Dv X509_V_FLAG_USE_CHECK_TIME
nor
.Dv X509_V_FLAG_NO_CHECK_TIME
is set, the validity period of certificates and CRLs is checked
using the current time.
This is the default behaviour.
In this case, if a validation time was set with
.Fn X509_VERIFY_PARAM_set_time
but
.Dv X509_V_FLAG_USE_CHECK_TIME
was later cleared with
.Fn X509_VERIFY_PARAM_clear_flags ,
the configured validation time is ignored
and the current time is used anyway.
.Pp
If
.Dv X509_V_FLAG_USE_CHECK_TIME
is not set but
.Dv X509_V_FLAG_NO_CHECK_TIME
is set, the validity period of certificates and CRLs is not checked
at all, and like in the previous case, any configured validation
time is ignored.
.Sh EXAMPLES
Enable CRL checking when performing certificate verification during
SSL connections associated with an
.Vt SSL_CTX
structure
.Fa ctx :
.Bd -literal -offset indent
X509_VERIFY_PARAM *param;

param = X509_VERIFY_PARAM_new();
X509_VERIFY_PARAM_set_flags(param, X509_V_FLAG_CRL_CHECK);
SSL_CTX_set1_param(ctx, param);
X509_VERIFY_PARAM_free(param);
.Ed
.Sh SEE ALSO
.Xr SSL_set1_host 3 ,
.Xr SSL_set1_param 3 ,
.Xr X509_check_host 3 ,
.Xr X509_STORE_CTX_new 3 ,
.Xr X509_STORE_new 3 ,
.Xr X509_verify_cert 3 ,
.Xr X509_VERIFY_PARAM_new 3
.Sh HISTORY
.Fn X509_VERIFY_PARAM_set1_name ,
.Fn X509_VERIFY_PARAM_set_flags ,
.Fn X509_VERIFY_PARAM_set_purpose ,
.Fn X509_VERIFY_PARAM_set_trust ,
.Fn X509_VERIFY_PARAM_set_time ,
.Fn X509_VERIFY_PARAM_add0_policy ,
.Fn X509_VERIFY_PARAM_set1_policies ,
.Fn X509_VERIFY_PARAM_set_depth ,
and
.Fn X509_VERIFY_PARAM_get_depth
first appeared in OpenSSL 0.9.8.
.Fn X509_VERIFY_PARAM_clear_flags
and
.Fn X509_VERIFY_PARAM_get_flags
first appeared in OpenSSL 0.9.8a.
All these functions have been available since
.Ox 4.5 .
.Pp
.Fn X509_VERIFY_PARAM_get0_name ,
.Fn X509_VERIFY_PARAM_set1_host ,
.Fn X509_VERIFY_PARAM_add1_host ,
.Fn X509_VERIFY_PARAM_set_hostflags ,
.Fn X509_VERIFY_PARAM_get0_peername ,
.Fn X509_VERIFY_PARAM_set1_email ,
.Fn X509_VERIFY_PARAM_set1_ip ,
and
.Fn X509_VERIFY_PARAM_set1_ip_asc
first appeared in OpenSSL 1.0.2 and have been available since
.Ox 6.3 .
.Pp
.Fn X509_VERIFY_PARAM_set_auth_level
first appeared in OpenSSL 1.1.0 and
.Fn X509_VERIFY_PARAM_get_time
in OpenSSL 1.1.0d.
Both functions have been available since
.Ox 7.2 .
.Sh BUGS
Delta CRL checking is currently primitive.
Only a single delta can be used and (partly due to limitations of
.Vt X509_STORE )
constructed CRLs are not maintained.
.Pp
If CRLs checking is enabled, CRLs are expected to be available in
the corresponding
.Vt X509_STORE
structure.
No attempt is made to download CRLs from the CRL distribution points
extension.