x509¶

NAME¶

openssl-x509, x509 - Certificate display and signing utility

SYNOPSIS¶

openssl x509 [-help] [-inform DER|PEM] [-outform DER|PEM] [-keyform DER|PEM|ENGINE] [-CAform DER|PEM] [-CAkeyform DER|PEM] [-in filename] [-out filename] [-serial] [-hash] [-subject_hash] [-issuer_hash] [-ocspid] [-subject] [-issuer] [-nameopt option] [-email] [-ocsp_uri] [-startdate] [-enddate] [-purpose] [-dates] [-checkend num] [-modulus] [-pubkey] [-fingerprint] [-alias] [-noout] [-trustout] [-clrtrust] [-clrreject] [-addtrust arg] [-addreject arg] [-setalias arg] [-days arg] [-set_serial n] [-signkey arg] [-passin arg] [-x509toreq] [-req] [-CA filename] [-CAkey filename] [-CAcreateserial] [-CAserial filename] [-force_pubkey key] [-text] [-ext extensions] [-certopt option] [-C] [-digest] [-clrext] [-extfile filename] [-extensions section] [-sigopt nm:v] [-rand file...] [-writerand file] [-engine id] [-preserve_dates]

DESCRIPTION¶

The x509 command is a multi purpose certificate utility. It can be used to display certificate information, convert certificates to various forms, sign certificate requests like a "mini CA" or edit certificate trust settings.

Since there are a large number of options they will split up into various sections.

OPTIONS¶

Input, Output, and General Purpose Options¶

-help
Print out a usage message.
-inform DER|PEM
This specifies the input format normally the command will expect an X509 certificate but this can change if other options such as -req are present. The DER format is the DER encoding of the certificate and PEM is the base64 encoding of the DER encoding with header and footer lines added. The default format is PEM.
-outform DER|PEM
This specifies the output format, the options have the same meaning and default as the -inform option.
-in filename
This specifies the input filename to read a certificate from or standard input if this option is not specified.
-out filename
This specifies the output filename to write to or standard output by default.
-digest
The digest to use. This affects any signing or display option that uses a message digest, such as the -fingerprint, -signkey and -CA options. Any digest supported by the OpenSSL dgst command can be used. If not specified then SHA1 is used with -fingerprint or the default digest for the signing algorithm is used, typically SHA256.
-rand file...
A file or files containing random data used to seed the random number generator. Multiple files can be specified separated by an OS-dependent character. The separator is ; for MS-Windows, , for OpenVMS, and : for all others.
[-writerand file]
Writes random data to the specified file upon exit. This can be used with a subsequent -rand flag.
-engine id
Specifying an engine (by its unique id string) will cause x509 to attempt to obtain a functional reference to the specified engine, thus initialising it if needed. The engine will then be set as the default for all available algorithms.
-preserve_dates
When signing a certificate, preserve the "notBefore" and "notAfter" dates instead of adjusting them to current time and duration. Cannot be used with the -days option.

Display Options¶

Note: the -alias and -purpose options are also display options but are described in the TRUST SETTINGS section.

-text
Prints out the certificate in text form. Full details are output including the public key, signature algorithms, issuer and subject names, serial number any extensions present and any trust settings.
-ext extensions
Prints out the certificate extensions in text form. Extensions are specified with a comma separated string, e.g., "subjectAltName,subjectKeyIdentifier". See the x509v3_config(5) manual page for the extension names.
-certopt option
Customise the output format used with -text. The option argument can be a single option or multiple options separated by commas. The -certopt switch may be also be used more than once to set multiple options. See the TEXT OPTIONS section for more information.
-noout
This option prevents output of the encoded version of the certificate.
-pubkey
Outputs the certificate's SubjectPublicKeyInfo block in PEM format.
-modulus
This option prints out the value of the modulus of the public key contained in the certificate.
-serial
Outputs the certificate serial number.
-subject_hash
Outputs the "hash" of the certificate subject name. This is used in OpenSSL to form an index to allow certificates in a directory to be looked up by subject name.
-issuer_hash
Outputs the "hash" of the certificate issuer name.
-ocspid
Outputs the OCSP hash values for the subject name and public key.
-hash
Synonym for "-subject_hash" for backward compatibility reasons.
-subject_hash_old
Outputs the "hash" of the certificate subject name using the older algorithm as used by OpenSSL before version 1.0.0.
-issuer_hash_old
Outputs the "hash" of the certificate issuer name using the older algorithm as used by OpenSSL before version 1.0.0.
-subject
Outputs the subject name.
-issuer
Outputs the issuer name.
-nameopt option
Option which determines how the subject or issuer names are displayed. The option argument can be a single option or multiple options separated by commas. Alternatively the -nameopt switch may be used more than once to set multiple options. See the NAME OPTIONS section for more information.
-email
Outputs the email address(es) if any.
-ocsp_uri
Outputs the OCSP responder address(es) if any.
-startdate
Prints out the start date of the certificate, that is the notBefore date.
-enddate
Prints out the expiry date of the certificate, that is the notAfter date.
-dates
Prints out the start and expiry dates of a certificate.
-checkend arg
Checks if the certificate expires within the next arg seconds and exits nonzero if yes it will expire or zero if not.
-fingerprint
Calculates and outputs the digest of the DER encoded version of the entire certificate (see digest options). This is commonly called a "fingerprint". Because of the nature of message digests, the fingerprint of a certificate is unique to that certificate and two certificates with the same fingerprint can be considered to be the same.
-C
This outputs the certificate in the form of a C source file.

Trust Settings¶

A trusted certificate is an ordinary certificate which has several additional pieces of information attached to it such as the permitted and prohibited uses of the certificate and an "alias".

Normally when a certificate is being verified at least one certificate must be "trusted". By default a trusted certificate must be stored locally and must be a root CA: any certificate chain ending in this CA is then usable for any purpose.

Trust settings currently are only used with a root CA. They allow a finer control over the purposes the root CA can be used for. For example a CA may be trusted for SSL client but not SSL server use.

See the description of the verify utility for more information on the meaning of trust settings.

Future versions of OpenSSL will recognize trust settings on any certificate: not just root CAs.

-trustout
This causes x509 to output a trusted certificate. An ordinary or trusted certificate can be input but by default an ordinary certificate is output and any trust settings are discarded. With the -trustout option a trusted certificate is output. A trusted certificate is automatically output if any trust settings are modified.
-setalias arg
Sets the alias of the certificate. This will allow the certificate to be referred to using a nickname for example "Steve's Certificate".
-alias
Outputs the certificate alias, if any.
-clrtrust
Clears all the permitted or trusted uses of the certificate.
-clrreject
Clears all the prohibited or rejected uses of the certificate.
-addtrust arg
Adds a trusted certificate use. Any object name can be used here but currently only clientAuth (SSL client use), serverAuth (SSL server use), emailProtection (S/MIME email) and anyExtendedKeyUsage are used. As of OpenSSL 1.1.0, the last of these blocks all purposes when rejected or enables all purposes when trusted. Other OpenSSL applications may define additional uses.
-addreject arg
Adds a prohibited use. It accepts the same values as the -addtrust option.
-purpose
This option performs tests on the certificate extensions and outputs the results. For a more complete description see the CERTIFICATE EXTENSIONS section.

Signing Options¶

The x509 utility can be used to sign certificates and requests: it can thus behave like a "mini CA".

-signkey arg
This option causes the input file to be self signed using the supplied private key or engine. The private key's format is specified with the -keyform option.
If the input file is a certificate it sets the issuer name to the subject name (i.e. makes it self signed) changes the public key to the supplied value and changes the start and end dates. The start date is set to the current time and the end date is set to a value determined by the -days option. Any certificate extensions are retained unless the -clrext option is supplied; this includes, for example, any existing key identifier extensions.
If the input is a certificate request then a self signed certificate is created using the supplied private key using the subject name in the request.
-sigopt nm:v
Pass options to the signature algorithm during sign or verify operations. Names and values of these options are algorithm-specific.
-passin arg
The key password source. For more information about the format of arg see "Pass Phrase Options" in openssl(1).
-clrext
Delete any extensions from a certificate. This option is used when a certificate is being created from another certificate (for example with the -signkey or the -CA options). Normally all extensions are retained.
-keyform PEM|DER|ENGINE
Specifies the format (DER or PEM) of the private key file used in the -signkey option.
-days arg
Specifies the number of days to make a certificate valid for. The default is 30 days. Cannot be used with the -preserve_dates option.
-x509toreq
Converts a certificate into a certificate request. The -signkey option is used to pass the required private key.
-req
By default a certificate is expected on input. With this option a certificate request is expected instead.
-set_serial n
Specifies the serial number to use. This option can be used with either the -signkey or -CA options. If used in conjunction with the -CA option the serial number file (as specified by the -CAserial or -CAcreateserial options) is not used.
The serial number can be decimal or hex (if preceded by 0x).
-CA filename
Specifies the CA certificate to be used for signing. When this option is present x509 behaves like a "mini CA". The input file is signed by this CA using this option: that is its issuer name is set to the subject name of the CA and it is digitally signed using the CAs private key.
This option is normally combined with the -req option. Without the -req option the input is a certificate which must be self signed.
-CAkey filename
Sets the CA private key to sign a certificate with. If this option is not specified then it is assumed that the CA private key is present in the CA certificate file.
-CAserial filename
Sets the CA serial number file to use.
When creating a certificate with this option, and with the -CA option, the certificate serial number is stored in the given file. This file consists of one line containing an even number of hex digits with the serial number used last time. After reading this number, it is incremented and used, and the file is updated.
The default filename consists of the CA certificate file base name with ".srl" appended. For example if the CA certificate file is called "mycacert.pem" it expects to find a serial number file called "mycacert.srl".
If the -CA option is specified and neither <-CAserial> or <-CAcreateserial> is given and the default serial number file does not exist, a random number is generated; this is the recommended practice.
-CAcreateserial
With this option and the -CA option the CA serial number file is created if it does not exist. A random number is generated, used for the certificate, and saved into the serial number file determined as described above.
-extfile filename
File containing certificate extensions to use. If not specified then no extensions are added to the certificate.
-extensions section
The section to add certificate extensions from. If this option is not specified then the extensions should either be contained in the unnamed (default) section or the default section should contain a variable called "extensions" which contains the section to use. See the x509v3_config(5) manual page for details of the extension section format.
-force_pubkey key
When a certificate is created set its public key to key instead of the key in the certificate or certificate request. This option is useful for creating certificates where the algorithm can't normally sign requests, for example DH.
The format or key can be specified using the -keyform option.

Name Options¶

The nameopt command line switch determines how the subject and issuer names are displayed. If no nameopt switch is present the default "oneline" format is used which is compatible with previous versions of OpenSSL. Each option is described in detail below, all options can be preceded by a - to turn the option off. Only the first four will normally be used.

compat
Use the old format.
RFC2253
Displays names compatible with RFC2253 equivalent to esc_2253, esc_ctrl, esc_msb, utf8, dump_nostr, dump_unknown, dump_der, sep_comma_plus, dn_rev and sname.
oneline
A oneline format which is more readable than RFC2253. It is equivalent to specifying the esc_2253, esc_ctrl, esc_msb, utf8, dump_nostr, dump_der, use_quote, sep_comma_plus_space, space_eq and sname options. This is the default of no name options are given explicitly.
multiline
A multiline format. It is equivalent esc_ctrl, esc_msb, sep_multiline, space_eq, lname and align.
esc_2253
Escape the "special" characters required by RFC2253 in a field. That is ,+"<>;. Additionally # is escaped at the beginning of a string and a space character at the beginning or end of a string.
esc_2254
Escape the "special" characters required by RFC2254 in a field. That is the NUL character as well as and ()*.
esc_ctrl
Escape control characters. That is those with ASCII values less than 0x20 (space) and the delete (0x7f) character. They are escaped using the RFC2253 \XX notation (where XX are two hex digits representing the character value).
esc_msb
Escape characters with the MSB set, that is with ASCII values larger than 127.
use_quote
Escapes some characters by surrounding the whole string with " characters, without the option all escaping is done with the \ character.
utf8
Convert all strings to UTF8 format first. This is required by RFC2253. If you are lucky enough to have a UTF8 compatible terminal then the use of this option (and not setting esc_msb) may result in the correct display of multibyte (international) characters. Is this option is not present then multibyte characters larger than 0xff will be represented using the format \UXXXX for 16 bits and \WXXXXXXXX for 32 bits. Also if this option is off any UTF8Strings will be converted to their character form first.
ignore_type
This option does not attempt to interpret multibyte characters in any way. That is their content octets are merely dumped as though one octet represents each character. This is useful for diagnostic purposes but will result in rather odd looking output.
show_type
Show the type of the ASN1 character string. The type precedes the field contents. For example "BMPSTRING: Hello World".
dump_der
When this option is set any fields that need to be hexdumped will be dumped using the DER encoding of the field. Otherwise just the content octets will be displayed. Both options use the RFC2253 #XXXX... format.
dump_nostr
Dump non character string types (for example OCTET STRING) if this option is not set then non character string types will be displayed as though each content octet represents a single character.
dump_all
Dump all fields. This option when used with dump_der allows the DER encoding of the structure to be unambiguously determined.
dump_unknown
Dump any field whose OID is not recognised by OpenSSL.
sep_comma_plus, sep_comma_plus_space, sep_semi_plus_space, sep_multiline
These options determine the field separators. The first character is between RDNs and the second between multiple AVAs (multiple AVAs are very rare and their use is discouraged). The options ending in "space" additionally place a space after the separator to make it more readable. The sep_multiline uses a linefeed character for the RDN separator and a spaced + for the AVA separator. It also indents the fields by four characters. If no field separator is specified then sep_comma_plus_space is used by default.
dn_rev
Reverse the fields of the DN. This is required by RFC2253. As a side effect this also reverses the order of multiple AVAs but this is permissible.
nofname, sname, lname, oid
These options alter how the field name is displayed. nofname does not display the field at all. sname uses the "short name" form (CN for commonName for example). lname uses the long form. oid represents the OID in numerical form and is useful for diagnostic purpose.
align
Align field values for a more readable output. Only usable with sep_multiline.
space_eq
Places spaces round the = character which follows the field name.

Text Options¶

As well as customising the name output format, it is also possible to customise the actual fields printed using the certopt options when the text option is present. The default behaviour is to print all fields.

compatible
Use the old format. This is equivalent to specifying no output options at all.
no_header
Don't print header information: that is the lines saying "Certificate" and "Data".
no_version
Don't print out the version number.
no_serial
Don't print out the serial number.
no_signame
Don't print out the signature algorithm used.
no_validity
Don't print the validity, that is the notBefore and notAfter fields.
no_subject
Don't print out the subject name.
no_issuer
Don't print out the issuer name.
no_pubkey
Don't print out the public key.
no_sigdump
Don't give a hexadecimal dump of the certificate signature.
no_aux
Don't print out certificate trust information.
no_extensions
Don't print out any X509V3 extensions.
ext_default
Retain default extension behaviour: attempt to print out unsupported certificate extensions.
ext_error
Print an error message for unsupported certificate extensions.
ext_parse
ASN1 parse unsupported extensions.
ext_dump
Hex dump unsupported extensions.
ca_default
The value used by the ca utility, equivalent to no_issuer, no_pubkey, no_header, and no_version.

EXAMPLES¶

Note: in these examples the '\' means the example should be all on one line.

Display the contents of a certificate:

openssl x509 -in cert.pem -noout -text

Display the "Subject Alternative Name" extension of a certificate:

openssl x509 -in cert.pem -noout -ext subjectAltName

Display more extensions of a certificate:

openssl x509 -in cert.pem -noout -ext subjectAltName,nsCertType

Display the certificate serial number:

openssl x509 -in cert.pem -noout -serial

Display the certificate subject name:

openssl x509 -in cert.pem -noout -subject

Display the certificate subject name in RFC2253 form:

openssl x509 -in cert.pem -noout -subject -nameopt RFC2253

Display the certificate subject name in oneline form on a terminal supporting UTF8:

openssl x509 -in cert.pem -noout -subject -nameopt oneline,-esc_msb

Display the certificate SHA1 fingerprint:

openssl x509 -sha1 -in cert.pem -noout -fingerprint

Convert a certificate from PEM to DER format:

openssl x509 -in cert.pem -inform PEM -out cert.der -outform DER

Convert a certificate to a certificate request:

openssl x509 -x509toreq -in cert.pem -out req.pem -signkey key.pem

Convert a certificate request into a self signed certificate using extensions for a CA:

openssl x509 -req -in careq.pem -extfile openssl.cnf -extensions v3_ca \
       -signkey key.pem -out cacert.pem

Sign a certificate request using the CA certificate above and add user certificate extensions:

openssl x509 -req -in req.pem -extfile openssl.cnf -extensions v3_usr \
       -CA cacert.pem -CAkey key.pem -CAcreateserial

Set a certificate to be trusted for SSL client use and change set its alias to "Steve's Class 1 CA"

openssl x509 -in cert.pem -addtrust clientAuth \
       -setalias "Steve's Class 1 CA" -out trust.pem

NOTES¶

The PEM format uses the header and footer lines:

-----BEGIN CERTIFICATE-----
-----END CERTIFICATE-----

it will also handle files containing:

-----BEGIN X509 CERTIFICATE-----
-----END X509 CERTIFICATE-----

Trusted certificates have the lines

-----BEGIN TRUSTED CERTIFICATE-----
-----END TRUSTED CERTIFICATE-----

The conversion to UTF8 format used with the name options assumes that T61Strings use the ISO8859-1 character set. This is wrong but Netscape and MSIE do this as do many certificates. So although this is incorrect it is more likely to display the majority of certificates correctly.

The -email option searches the subject name and the subject alternative name extension. Only unique email addresses will be printed out: it will not print the same address more than once.

CERTIFICATE EXTENSIONS¶

The -purpose option checks the certificate extensions and determines what the certificate can be used for. The actual checks done are rather complex and include various hacks and workarounds to handle broken certificates and software.

The same code is used when verifying untrusted certificates in chains so this section is useful if a chain is rejected by the verify code.

The basicConstraints extension CA flag is used to determine whether the certificate can be used as a CA. If the CA flag is true then it is a CA, if the CA flag is false then it is not a CA. All CAs should have the CA flag set to true.

If the basicConstraints extension is absent then the certificate is considered to be a "possible CA" other extensions are checked according to the intended use of the certificate. A warning is given in this case because the certificate should really not be regarded as a CA: however it is allowed to be a CA to work around some broken software.

If the certificate is a V1 certificate (and thus has no extensions) and it is self signed it is also assumed to be a CA but a warning is again given: this is to work around the problem of Verisign roots which are V1 self signed certificates.

If the keyUsage extension is present then additional restraints are made on the uses of the certificate. A CA certificate must have the keyCertSign bit set if the keyUsage extension is present.

The extended key usage extension places additional restrictions on the certificate uses. If this extension is present (whether critical or not) the key can only be used for the purposes specified.

A complete description of each test is given below. The comments about basicConstraints and keyUsage and V1 certificates above apply to all CA certificates.

SSL Client
The extended key usage extension must be absent or include the "web client authentication" OID. keyUsage must be absent or it must have the digitalSignature bit set. Netscape certificate type must be absent or it must have the SSL client bit set.
SSL Client CA
The extended key usage extension must be absent or include the "web client authentication" OID. Netscape certificate type must be absent or it must have the SSL CA bit set: this is used as a work around if the basicConstraints extension is absent.
SSL Server
The extended key usage extension must be absent or include the "web server authentication" and/or one of the SGC OIDs. keyUsage must be absent or it must have the digitalSignature, the keyEncipherment set or both bits set. Netscape certificate type must be absent or have the SSL server bit set.
SSL Server CA
The extended key usage extension must be absent or include the "web server authentication" and/or one of the SGC OIDs. Netscape certificate type must be absent or the SSL CA bit must be set: this is used as a work around if the basicConstraints extension is absent.
Netscape SSL Server
For Netscape SSL clients to connect to an SSL server it must have the keyEncipherment bit set if the keyUsage extension is present. This isn't always valid because some cipher suites use the key for digital signing. Otherwise it is the same as a normal SSL server.
Common S/MIME Client Tests
The extended key usage extension must be absent or include the "email protection" OID. Netscape certificate type must be absent or should have the S/MIME bit set. If the S/MIME bit is not set in Netscape certificate type then the SSL client bit is tolerated as an alternative but a warning is shown: this is because some Verisign certificates don't set the S/MIME bit.
S/MIME Signing
In addition to the common S/MIME client tests the digitalSignature bit or the nonRepudiation bit must be set if the keyUsage extension is present.
S/MIME Encryption
In addition to the common S/MIME tests the keyEncipherment bit must be set if the keyUsage extension is present.
S/MIME CA
The extended key usage extension must be absent or include the "email protection" OID. Netscape certificate type must be absent or must have the S/MIME CA bit set: this is used as a work around if the basicConstraints extension is absent.
CRL Signing
The keyUsage extension must be absent or it must have the CRL signing bit set.
CRL Signing CA
The normal CA tests apply. Except in this case the basicConstraints extension must be present.

BUGS¶

Extensions in certificates are not transferred to certificate requests and vice versa.

It is possible to produce invalid certificates or requests by specifying the wrong private key or using inconsistent options in some cases: these should be checked.

There should be options to explicitly set such things as start and end dates rather than an offset from the current time.

HISTORY¶

The hash algorithm used in the -subject_hash and -issuer_hash options before OpenSSL 1.0.0 was based on the deprecated MD5 algorithm and the encoding of the distinguished name. In OpenSSL 1.0.0 and later it is based on a canonical version of the DN using SHA1. This means that any directories using the old form must have their links rebuilt using c_rehash or similar.

COPYRIGHT¶

Licensed under the OpenSSL license (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