openssl-req - PKCS#10 certificate request and certificate generating command
openssl req [-help] [-inform DER|PEM] [-outform DER|PEM] [-in filename] [-passin arg] [-out filename] [-passout arg] [-text] [-pubkey] [-noout] [-verify] [-modulus] [-new] [-newkey arg] [-pkeyopt opt:value] [-noenc] [-nodes] [-key filename|uri] [-keyform DER|PEM|P12|ENGINE] [-keyout filename] [-keygen_engine id] [-digest] [-config filename] [-section name] [-x509] [-CA filename|uri] [-CAkey filename|uri] [-days n] [-set_serial n] [-newhdr] [-copy_extensions arg] [-addext ext] [-extensions section] [-reqexts section] [-precert] [-utf8] [-reqopt] [-subject] [-subj arg] [-multivalue-rdn] [-sigopt nm:v] [-vfyopt nm:v] [-batch] [-verbose] [-nameopt option] [-rand files] [-writerand file] [-engine id] [-provider name] [-provider-path path] [-propquery propq]
This command primarily creates and processes certificate requests (CSRs) in PKCS#10 format. It can additionally create self-signed certificates for use as root CAs for example.
- Print out a usage message.
- -inform DER|PEM, -outform DER|PEM
- The input and output formats; unspecified by default. See
openssl-format-options(1) for details.
The data is a PKCS#10 object.
- -in filename
- This specifies the input filename to read a request from. This defaults to standard input unless -x509 or -CA is specified. A request is only read if the creation options (-new or -newkey or -precert) are not specified.
- -sigopt nm:v
- Pass options to the signature algorithm during sign operations. Names and values of these options are algorithm-specific.
- -vfyopt nm:v
- Pass options to the signature algorithm during verify operations. Names and values of these options are algorithm-specific.
- -passin arg
- The password source for private key and certificate input. For more information about the format of arg see openssl-passphrase-options(1).
- -passout arg
- The password source for the output file. For more information about the format of arg see openssl-passphrase-options(1).
- -out filename
- This specifies the output filename to write to or standard output by default.
- Prints out the certificate request in text form.
- Prints out the certificate request subject (or certificate subject if -x509 is in use).
- Prints out the public key.
- This option prevents output of the encoded version of the certificate request.
- Prints out the value of the modulus of the public key contained in the request.
- Verifies the self-signature on the request.
- This option generates a new certificate request. It will prompt the user
for the relevant field values. The actual fields prompted for and their
maximum and minimum sizes are specified in the configuration file and any
If the -key option is not given it will generate a new private key using information specified in the configuration file or given with the -newkey and -pkeyopt options, else by default an RSA key with 2048 bits length.
- -newkey arg
- This option is used to generate a new private key unless -key is
given. It is subsequently used as if it was given using the -key
This option implies the -new flag to create a new certificate request or a new certificate in case -x509 is given.
The argument takes one of several forms.
[rsa:]nbits generates an RSA key nbits in size. If nbits is omitted, i.e., -newkey rsa is specified, the default key size specified in the configuration file with the default_bits option is used if present, else 2048.
All other algorithms support the -newkey algname:file form, where file is an algorithm parameter file, created with "openssl genpkey -genparam" or an X.509 certificate for a key with appropriate algorithm.
param:file generates a key using the parameter file or certificate file, the algorithm is determined by the parameters.
algname[:file] generates a key using the given algorithm algname. If a parameter file file is given then the parameters specified there are used, where the algorithm parameters must match algname. If algorithm parameters are not given, any necessary parameters should be specified via the -pkeyopt option.
dsa:filename generates a DSA key using the parameters in the file filename. ec:filename generates EC key (usable both with ECDSA or ECDH algorithms), gost2001:filename generates GOST R 34.10-2001 key (requires gost engine configured in the configuration file). If just gost2001 is specified a parameter set should be specified by -pkeyopt paramset:X
- -pkeyopt opt:value
- Set the public key algorithm option opt to value. The precise set of options supported depends on the public key algorithm used and its implementation. See "KEY GENERATION OPTIONS" in openssl-genpkey(1) for more details.
- -key filename|uri
- This option provides the private key for signing a new certificate or
certificate request. Unless -in is given, the corresponding public
key is placed in the new certificate or certificate request, resulting in
For certificate signing this option is overridden by the -CA option.
This option also accepts PKCS#8 format private keys for PEM format files.
- -keyform DER|PEM|P12|ENGINE
- The format of the private key; unspecified by default. See openssl-format-options(1) for details.
- -keyout filename
- This gives the filename to write any private key to that has been newly created or read from -key. If neither the -keyout option nor the -key option are given then the filename specified in the configuration file with the default_keyfile option is used, if present. Thus, if you want to write the private key and the -key option is provided, you should provide the -keyout option explicitly. If a new key is generated and no filename is specified the key is written to standard output.
- If this option is specified then if a private key is created it will not be encrypted.
- This option is deprecated since OpenSSL 3.0; use -noenc instead.
- This specifies the message digest to sign the request. Any digest
supported by the OpenSSL dgst command can be used. This overrides
the digest algorithm specified in the configuration file.
Some public key algorithms may override this choice. For instance, DSA signatures always use SHA1, GOST R 34.10 signatures always use GOST R 34.11-94 (-md_gost94), Ed25519 and Ed448 never use any digest.
- -config filename
- This allows an alternative configuration file to be specified. Optional; for a description of the default value, see "COMMAND SUMMARY" in openssl(1).
- -section name
- Specifies the name of the section to use; the default is req.
- -subj arg
- Sets subject name for new request or supersedes the subject name when
processing a certificate request.
The arg must be formatted as "/type0=value0/type1=value1/type2=...". Special characters may be escaped by "\" (backslash), whitespace is retained. Empty values are permitted, but the corresponding type will not be included in the request. Giving a single "/" will lead to an empty sequence of RDNs (a NULL-DN). Multi-valued RDNs can be formed by placing a "+" character instead of a "/" between the AttributeValueAssertions (AVAs) that specify the members of the set. Example:
- This option has been deprecated and has no effect.
- This option outputs a certificate instead of a certificate request. This
is typically used to generate test certificates. It is implied by the
This option implies the -new flag if -in is not given.
If an existing request is specified with the -in option, it is converted to the a certificate; otherwise a request is created from scratch.
Unless specified using the -set_serial option, a large random number will be used for the serial number.
Unless the -copy_extensions option is used, X.509 extensions are not copied from any provided request input file.
X.509 extensions to be added can be specified in the configuration file or using the -addext option.
- -CA filename|uri
- Specifies the "CA" certificate to be used for signing a new certificate and implies use of -x509. When present, this behaves like a "micro CA" as follows: The subject name of the "CA" certificate is placed as issuer name in the new certificate, which is then signed using the "CA" key given as specified below.
- -CAkey filename|uri
- Sets the "CA" private key to sign a certificate with. The private key must match the public key of the certificate given with -CA. If this option is not provided then the key must be present in the -CA input.
- -days n
- When -x509 is in use this specifies the number of days to certify the certificate for, otherwise it is ignored. n should be a positive integer. The default is 30 days.
- -set_serial n
- Serial number to use when outputting a self-signed certificate. This may be specified as a decimal value or a hex value if preceded by "0x". If not given, a large random number will be used.
- -copy_extensions arg
- Determines how X.509 extensions in certificate requests should be handled
when -x509 is in use. If arg is none or this option
is not present then extensions are ignored. If arg is copy
or copyall then all extensions in the request are copied to the
The main use of this option is to allow a certificate request to supply values for certain extensions such as subjectAltName.
- -addext ext
- Add a specific extension to the certificate (if -x509 is in use) or
certificate request. The argument must have the form of a key=value pair
as it would appear in a config file.
This option can be given multiple times.
- -extensions section
- -reqexts section
- These options specify alternative sections to include certificate extensions (if -x509 is in use) or certificate request extensions. This allows several different sections to be used in the same configuration file to specify requests for a variety of purposes.
- A poison extension will be added to the certificate, making it a
"pre-certificate" (see RFC6962). This can be submitted to
Certificate Transparency logs in order to obtain signed certificate
timestamps (SCTs). These SCTs can then be embedded into the
pre-certificate as an extension, before removing the poison and signing
This implies the -new flag.
- This option causes field values to be interpreted as UTF8 strings, by default they are interpreted as ASCII. This means that the field values, whether prompted from a terminal or obtained from a configuration file, must be valid UTF8 strings.
- -reqopt option
- Customise the printing format used with -text. The option
argument can be a single option or multiple options separated by commas.
See discussion of the -certopt parameter in the openssl-x509(1) command.
- Adds the word NEW to the PEM file header and footer lines on the outputted request. Some software (Netscape certificate server) and some CAs need this.
- Non-interactive mode.
- Print extra details about the operations being performed.
- -keygen_engine id
- Specifies an engine (by its unique id string) which would be used for key generation operations.
- -nameopt option
- This specifies how the subject or issuer names are displayed. See openssl-namedisplay-options(1) for details.
- -rand files, -writerand file
- See "Random State Options" in openssl(1) for details.
- -engine id
- See "Engine Options" in openssl(1). This option is deprecated.
- -provider name
- -provider-path path
- -propquery propq
- See "Provider Options" in openssl(1), provider(7), and property(7).
The configuration options are specified in the req section of the configuration file. An alternate name be specified by using the -section option. As with all configuration files, if no value is specified in the specific section then the initial unnamed or default section is searched too.
The options available are described in detail below.
- input_password, output_password
- The passwords for the input private key file (if present) and the output private key file (if one will be created). The command line options passin and passout override the configuration file values.
- Specifies the default key size in bits.
This option is used in conjunction with the -new option to generate a new key. It can be overridden by specifying an explicit key size in the -newkey option. The smallest accepted key size is 512 bits. If no key size is specified then 2048 bits is used.
- This is the default filename to write a private key to. If not specified the key is written to standard output. This can be overridden by the -keyout option.
- This specifies a file containing additional OBJECT IDENTIFIERS. Each line of the file should consist of the numerical form of the object identifier followed by whitespace then the short name followed by whitespace and finally the long name.
- This specifies a section in the configuration file containing extra object identifiers. Each line should consist of the short name of the object identifier followed by = and the numerical form. The short and long names are the same when this option is used.
- At startup the specified file is loaded into the random number generator, and at exit 256 bytes will be written to it. It is used for private key generation.
- If this is set to no then if a private key is generated it is not encrypted. This is equivalent to the -noenc command line option. For compatibility encrypt_rsa_key is an equivalent option.
- This option specifies the digest algorithm to use. Any digest supported by the OpenSSL dgst command can be used. This option can be overridden on the command line. Certain signing algorithms (i.e. Ed25519 and Ed448) will ignore any digest that has been set.
- This option masks out the use of certain string types in certain fields.
Most users will not need to change this option.
It can be set to several values default which is also the default option uses PrintableStrings, T61Strings and BMPStrings if the pkix value is used then only PrintableStrings and BMPStrings will be used. This follows the PKIX recommendation in RFC2459. If the utf8only option is used then only UTF8Strings will be used: this is the PKIX recommendation in RFC2459 after 2003. Finally the nombstr option just uses PrintableStrings and T61Strings: certain software has problems with BMPStrings and UTF8Strings: in particular Netscape.
- This specifies the configuration file section containing a list of extensions to add to the certificate request. It can be overridden by the -reqexts command line switch. See the x509v3_config(5) manual page for details of the extension section format.
- This specifies the configuration file section containing a list of extensions to add to certificate generated when -x509 is in use. It can be overridden by the -extensions command line switch.
- If set to the value no this disables prompting of certificate fields and just takes values from the config file directly. It also changes the expected format of the distinguished_name and attributes sections.
- If set to the value yes then field values to be interpreted as UTF8 strings, by default they are interpreted as ASCII. This means that the field values, whether prompted from a terminal or obtained from a configuration file, must be valid UTF8 strings.
- This specifies the section containing any request attributes: its format is the same as distinguished_name. Typically these may contain the challengePassword or unstructuredName types. They are currently ignored by OpenSSL's request signing utilities but some CAs might want them.
- This specifies the section containing the distinguished name fields to prompt for when generating a certificate or certificate request. The format is described in the next section.
There are two separate formats for the distinguished name and attribute sections. If the prompt option is set to no then these sections just consist of field names and values: for example,
CN=My Name OU=My Organization emailAddressemail@example.com
This allows external programs (e.g. GUI based) to generate a template file with all the field names and values and just pass it to this command. An example of this kind of configuration file is contained in the EXAMPLES section.
Alternatively if the prompt option is absent or not set to no then the file contains field prompting information. It consists of lines of the form:
fieldName="prompt" fieldName_default="default field value" fieldName_min= 2 fieldName_max= 4
"fieldName" is the field name being used, for example commonName (or CN). The "prompt" string is used to ask the user to enter the relevant details. If the user enters nothing then the default value is used if no default value is present then the field is omitted. A field can still be omitted if a default value is present if the user just enters the '.' character.
The number of characters entered must be between the fieldName_min and fieldName_max limits: there may be additional restrictions based on the field being used (for example countryName can only ever be two characters long and must fit in a PrintableString).
Some fields (such as organizationName) can be used more than once in a DN. This presents a problem because configuration files will not recognize the same name occurring twice. To avoid this problem if the fieldName contains some characters followed by a full stop they will be ignored. So for example a second organizationName can be input by calling it "1.organizationName".
The actual permitted field names are any object identifier short or long names. These are compiled into OpenSSL and include the usual values such as commonName, countryName, localityName, organizationName, organizationalUnitName, stateOrProvinceName. Additionally emailAddress is included as well as name, surname, givenName, initials, and dnQualifier.
Additional object identifiers can be defined with the oid_file or oid_section options in the configuration file. Any additional fields will be treated as though they were a DirectoryString.
Examine and verify certificate request:
openssl req -in req.pem -text -verify -noout
Create a private key and then generate a certificate request from it:
openssl genrsa -out key.pem 2048 openssl req -new -key key.pem -out req.pem
The same but just using req:
openssl req -newkey rsa:2048 -keyout key.pem -out req.pem
Generate a self-signed root certificate:
openssl req -x509 -newkey rsa:2048 -keyout key.pem -out req.pem
Create an SM2 private key and then generate a certificate request from it:
openssl ecparam -genkey -name SM2 -out sm2.key openssl req -new -key sm2.key -out sm2.csr -sm3 -sigopt "distid:1234567812345678"
Examine and verify an SM2 certificate request:
openssl req -verify -in sm2.csr -sm3 -vfyopt "distid:1234567812345678"
Example of a file pointed to by the oid_file option:
184.108.40.206 shortName A longer Name 220.127.116.11 otherName Other longer Name
Example of a section pointed to by oid_section making use of variable expansion:
Sample configuration file prompting for field values:
[ req ] default_bits = 2048 default_keyfile = privkey.pem distinguished_name = req_distinguished_name attributes = req_attributes req_extensions = v3_ca dirstring_type = nobmp [ req_distinguished_name ] countryName = Country Name (2 letter code) countryName_default = AU countryName_min = 2 countryName_max = 2 localityName = Locality Name (eg, city) organizationalUnitName = Organizational Unit Name (eg, section) commonName = Common Name (eg, YOUR name) commonName_max = 64 emailAddress = Email Address emailAddress_max = 40 [ req_attributes ] challengePassword = A challenge password challengePassword_min = 4 challengePassword_max = 20 [ v3_ca ] subjectKeyIdentifier=hash authorityKeyIdentifier=keyid:always,issuer:always basicConstraints = critical, CA:true
Sample configuration containing all field values:
[ req ] default_bits = 2048 default_keyfile = keyfile.pem distinguished_name = req_distinguished_name attributes = req_attributes prompt = no output_password = mypass [ req_distinguished_name ] C = GB ST = Test State or Province L = Test Locality O = Organization Name OU = Organizational Unit Name CN = Common Name emailAddress = firstname.lastname@example.org [ req_attributes ] challengePassword = A challenge password
Example of giving the most common attributes (subject and extensions) on the command line:
openssl req -new -subj "/C=GB/CN=foo" \ -addext "subjectAltName = DNS:foo.co.uk" \ -addext "certificatePolicies = 18.104.22.168" \ -newkey rsa:2048 -keyout key.pem -out req.pem
The certificate requests generated by Xenroll with MSIE have extensions added. It includes the keyUsage extension which determines the type of key (signature only or general purpose) and any additional OIDs entered by the script in an extendedKeyUsage extension.
The following messages are frequently asked about:
Using configuration from /some/path/openssl.cnf Unable to load config info
This is followed some time later by:
unable to find 'distinguished_name' in config problems making Certificate Request
The first error message is the clue: it can't find the configuration file! Certain operations (like examining a certificate request) don't need a configuration file so its use isn't enforced. Generation of certificates or requests however does need a configuration file. This could be regarded as a bug.
Another puzzling message is this:
this is displayed when no attributes are present and the request includes the correct empty SET OF structure (the DER encoding of which is 0xa0 0x00). If you just see:
then the SET OF is missing and the encoding is technically invalid (but it is tolerated). See the description of the command line option -asn1-kludge for more information.
OpenSSL's handling of T61Strings (aka TeletexStrings) is broken: it effectively treats them as ISO-8859-1 (Latin 1), Netscape and MSIE have similar behaviour. This can cause problems if you need characters that aren't available in PrintableStrings and you don't want to or can't use BMPStrings.
As a consequence of the T61String handling the only correct way to represent accented characters in OpenSSL is to use a BMPString: unfortunately Netscape currently chokes on these. If you have to use accented characters with Netscape and MSIE then you currently need to use the invalid T61String form.
The current prompting is not very friendly. It doesn't allow you to confirm what you've just entered. Other things like extensions in certificate requests are statically defined in the configuration file. Some of these: like an email address in subjectAltName should be input by the user.
The -section option was added in OpenSSL 3.0.0.
The -multivalue-rdn option has become obsolete in OpenSSL 3.0.0 and has no effect.
The -engine option was deprecated in OpenSSL 3.0. The <-nodes> option was deprecated in OpenSSL 3.0, too; use -noenc instead.
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Licensed under the Apache License 2.0 (the "License"). You may not use this file except in compliance with the License. You can obtain a copy in the file LICENSE in the source distribution or at https://www.openssl.org/source/license.html.