OPENSSL-X509(1ossl)

📦
version 3.5.9 · 8 versions
, in alpine 3.23, alpine 3.24

🎀 OPENSSL-X509(1ossl) 🎀 — Certificate display and signing command

okay bestie, welcome to openssl-x509 💅 this is the OpenSSL manual page OPENSSL-X509(1ossl), aka the certificate display and signing command. she does a lot, so buckle up 🦋

🌸 NAME 🌸

openssl-x509 — certificate display and signing command ✨

✨ SYNOPSIS ✨

here's the whole flag parade, character-for-character, no cap:

       openssl x509 [-help] [-in filename|uri] [-passin arg] [-new]
       [-x509toreq] [-req] [-copy_extensions arg] [-inform DER|PEM] [-vfyopt
       nm:v] [-key filename|uri] [-keyform DER|PEM|P12|ENGINE] [-signkey
       filename|uri] [-out filename] [-outform DER|PEM] [-nocert] [-noout]
       [-dateopt] [-text] [-certopt option] [-fingerprint] [-alias] [-serial]
       [-startdate] [-enddate] [-dates] [-subject] [-issuer] [-nameopt option]
       [-email] [-hash] [-subject_hash] [-subject_hash_old] [-issuer_hash]
       [-issuer_hash_old] [-ext extensions] [-ocspid] [-ocsp_uri] [-purpose]
       [-pubkey] [-modulus] [-checkend num] [-checkhost host] [-checkemail
       host] [-checkip ipaddr] [-set_serial n] [-next_serial] [-not_before
       date] [-not_after date] [-days arg] [-preserve_dates] [-set_issuer arg]
       [-set_subject arg] [-subj arg] [-force_pubkey filename] [-clrext]
       [-extfile filename] [-extensions section] [-sigopt nm:v] [-badsig]
       [-digest] [-CA filename|uri] [-CAform DER|PEM|P12] [-CAkey filename|uri]
       [-CAkeyform DER|PEM|P12|ENGINE] [-CAserial filename] [-CAcreateserial]
       [-trustout] [-setalias arg] [-clrtrust] [-addtrust arg] [-clrreject]
       [-addreject arg] [-rand files] [-writerand file] [-engine id] [-provider
       name] [-provider-path path] [-provparam [name:]key=value] [-propquery
       propq]

🦋 DESCRIPTION 🦋

This command is a multi-purposes certificate handling command. Like, genuinely multi-purposes 💅 It can be used to print certificate information, convert certificates to various forms, edit certificate trust settings, generate certificates from scratch or from certification requests, and then self-signing them or signing them like a "micro CA" 👑

Generated certificates bear X.509 version 3. Unless specified otherwise, key identifier extensions are included as described in x509v3_config(5).

Since there are a large number of options they will split up into various sections. bestie, there are so many options 😭

💖 OPTIONS 💖

🌈 Input, Output, and General Purpose Options 🌈

  • -help — Print out a usage message. cute and simple 🫶
  • -in filename|uri — This specifies the input to read a certificate from or the input file for reading a certificate request if the -req flag is used. In both cases this defaults to standard input.

This option cannot be combined with the -new flag.

  • -passin arg — The key and certificate file password source 🔐 For more information about the format of arg see openssl-passphrase-options(1).
  • -new — Generate a certificate from scratch, not using an input certificate or certificate request. So this excludes the -in and -req options. Instead, the -set_subject option needs to be given. The public key to include can be given with the -force_pubkey option and defaults to the key given with the -key (or -signkey) option, which implies self-signature ✨
  • -x509toreq — Output a PKCS#10 certificate request (rather than a certificate). The -key (or -signkey) option must be used to provide the private key for self-signing; the corresponding public key is placed in the subjectPKInfo field.

X.509 extensions included in a certificate input are not copied by default. X.509 extensions to be added can be specified using the -extfile option.

  • -req — By default a certificate is expected on input. With this option a PKCS#10 certificate request is expected instead, which must be correctly self-signed.

X.509 extensions included in the request are not copied by default. X.509 extensions to be added can be specified using the -extfile option.

  • -copy_extensions arg — Determines how to handle X.509 extensions when converting from a certificate to a request using the -x509toreq option or converting from a request to a certificate using the -req option. If arg is none or this option is not present then extensions are ignored. If arg is copy or copyall then all extensions are copied, except that subject identifier and authority key identifier extensions are not taken over when producing a certificate request.

The -ext option can be used to further restrict which extensions to copy 🎀

  • -inform DER|PEM — The input file format to use; by default PEM is tried first. See openssl-format-options(1) for details.
  • -vfyopt nm:v — Pass options to the signature algorithm during verify operations. Names and values of these options are algorithm-specific.
  • -key filename|uri — This option provides the private key for signing a new certificate or certificate request. Unless -force_pubkey is given, the corresponding public key is placed in the new certificate or certificate request, resulting in a self-signature.

This option cannot be used in conjunction with the -CA option.

It sets the issuer name to the subject name (i.e., makes it self-issued). Unless the -preserve_dates option is supplied, it sets the validity start date to the current time and the end date to a value determined by the -days option. Start date and end date can also be explicitly supplied with options -not_before and -not_after 👑

  • -signkey filename|uri — This option is an alias of -key.
  • -keyform DER|PEM|P12|ENGINE — The key input format; unspecified by default. See openssl-format-options(1) for details.
  • -out filename — This specifies the output filename to write to or standard output by default.
  • -outform DER|PEM — The output format; the default is PEM. See openssl-format-options(1) for details.
  • -nocert — Do not output a certificate (except for printing as requested by below options).
  • -noout — This option prevents output except for printing as requested by below options.

🎀 Certificate Printing Options 🎀

note bestie: the -alias and -purpose options are also printing options but are described in the "Trust Settings" section. iykyk 💅
  • -dateopt — Specify the date output format. Values are: rfc_822 and iso_8601. Defaults to rfc_822.
  • -text — Prints out the certificate in text form. Full details are printed including the public key, signature algorithms, issuer and subject names, serial number any extensions present and any trust settings 👑
  • -certopt option — Customise the print 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 Printing Flags" section for more information.
  • -fingerprint — Calculates and prints 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.
  • -alias — Prints the certificate "alias" (nickname), if any.
  • -serial — Prints the certificate serial number.
  • -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.
  • -subject — Prints the subject name.
  • -issuer — Prints the issuer name.
  • -nameopt option — This specifies how the subject or issuer names are displayed. See openssl-namedisplay-options(1) for details.
  • -email — Prints the email address(es) if any.
  • -hash — Synonym for -subject_hash for backward compatibility reasons.
  • -subject_hash — Prints 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.
  • -subject_hash_old — Prints the "hash" of the certificate subject name using the older algorithm as used by OpenSSL before version 1.0.0.
  • -issuer_hash — Prints the "hash" of the certificate issuer name.
  • -issuer_hash_old — Prints the "hash" of the certificate issuer name using the older algorithm as used by OpenSSL before version 1.0.0.
  • -ext extensions — Prints out the certificate extensions in text form. Can also be used to restrict which extensions to copy. Extensions are specified with a comma separated string, e.g., "subjectAltName, subjectKeyIdentifier". See the x509v3_config(5) manual page for the extension names.
  • -ocspid — Prints the OCSP hash values for the subject name and public key.
  • -ocsp_uri — Prints the OCSP responder address(es) if any.
  • -purpose — This option performs tests on the certificate extensions and outputs the results. For a more complete description see "Certificate Extensions" in openssl-verification-options(1).
  • -pubkey — Prints 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.

🧚 Certificate Checking Options 🧚

  • -checkend arg — Checks if the certificate expires within the next arg seconds and exits nonzero if yes it will expire or zero if not.
  • -checkhost host — Check that the certificate matches the specified host.
  • -checkemail email — Check that the certificate matches the specified email address.
  • -checkip ipaddr — Check that the certificate matches the specified IP address.

👑 Certificate Output Options 👑

  • -set_serial n — Specifies the serial number to use. This option can be used with the -key, -signkey, or -CA options. If used in conjunction with the -CA option the serial number file (as specified by the -CAserial option) is not used.

The serial number can be decimal or hex (if preceded by "0x").

  • -next_serial — Set the serial to be one more than the number in the certificate.
  • -not_before date — This allows the start date to be explicitly set. The format of the date is YYMMDDHHMMSSZ (the same as an ASN1 UTCTime structure), or YYYYMMDDHHMMSSZ (the same as an ASN1 GeneralizedTime structure). In both formats, seconds SS and timezone Z must be present. Alternatively, you can also use "today".

Cannot be used together with the -preserve_dates option.

  • -not_after date — okay so this lets you explicitly set the expiry date. The format is YYMMDDHHMMSSZ (the same as an ASN1 UTCTime structure), or YYYYMMDDHHMMSSZ (the same as an ASN1 GeneralizedTime structure). In both formats, seconds SS and timezone Z must be present. You can also use "today".

Cannot be used together with the -preserve_dates option. This overrides the option -days.

  • -days arg — specifies the number of days from today until a newly generated certificate expires. Default is 30.

Cannot be used together with the option -preserve_dates. If option -not_after is set, the explicit expiry date takes precedence.

  • -preserve_dates — when signing a certificate, preserve "notBefore" and "notAfter" dates of any input certificate instead of adjusting them to current time and duration. Cannot be used together with the options -days, -not_before and -not_after.
  • -set_issuer arg — when a certificate is created, set its issuer name to the given value.

See -set_subject on how the arg must be formatted.

  • -set_subject arg — when a certificate is created, set its subject name to the given value. When the certificate is self-signed the issuer name is set to the same value, unless the -set_issuer option is given.

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 certificate. 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:

"/DC=org/DC=OpenSSL/DC=users/UID=123456+CN=John Doe"

This option can be used with the -new and -force_pubkey options to create a new certificate without providing an input certificate or certificate request.

  • -subj arg — this option is an alias of -set_subject.
  • -force_pubkey filename — when a new certificate or certificate request is created, set its public key to the given key instead of the key contained in the input or given with the -key (or -signkey) option. If the input contains no public key but a private key, its public part is used.

This option can be used in conjunction with -new and -set_subject to directly generate a certificate containing any desired public key.

This option is also useful for creating self-issued certificates that are not self-signed, for instance when the key cannot be used for signing, such as DH.

  • -clrext — when transforming a certificate to a new certificate, by default all certificate extensions are retained.

When transforming a certificate or certificate request, the -clrext option prevents taking over any extensions from the source. In any case, when producing a certificate request, neither subject identifier nor authority key identifier extensions are included.

  • -extfile filename — configuration file containing certificate and request X.509 extensions to add.
  • -extensions section — the section in the extfile to add X.509 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.

Unless specified otherwise, key identifier extensions are included as described in x509v3_config(5).

  • -sigopt nm:v — pass options to the signature algorithm during sign operations. This option may be given multiple times. Names and values provided using this option are algorithm-specific.
  • -badsig — corrupt the signature before writing it; this can be useful for testing.
  • -digest — the digest to use. This affects any signing or printing option that uses a message digest, such as the -fingerprint, -key, and -CA options. Any digest supported by the openssl-dgst(1) 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.

🫶 Micro-CA Options 🫶

  • -CA filename|uri — specifies the "CA" certificate to be used for signing. 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 detailed below.

This option cannot be used in conjunction with -key (or -signkey). This option is normally combined with the -req option referencing a CSR. Without the -req option the input must be an existing certificate unless the -new option is given, which generates a certificate from scratch.

  • -CAform DER|PEM|P12, — the format for the CA certificate; unspecified by default. See openssl-format-options(1) for details.
  • -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.
  • -CAkeyform DER|PEM|P12|ENGINE — the format for the CA key; unspecified by default. See openssl-format-options(1) for details.
  • -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 nor -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.

🛡️ 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 possibly an "alias" (nickname).

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 openssl-verification-options(1) 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 — mark any certificate PEM output as <trusted> certificate rather than ordinary. 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".
  • -clrtrust — clears all the permitted or trusted uses of the certificate.
  • -addtrust arg — adds a trusted certificate use. Any object name can be used here but currently only clientAuth, serverAuth, emailProtection, and anyExtendedKeyUsage are defined. 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.
  • -clrreject — clears all the prohibited or rejected uses of the certificate.
  • -addreject arg — adds a prohibited trust anchor purpose. It accepts the same values as the -addtrust option.

🌈 Generic options 🌈

💅 Text Printing Flags 💅

As well as customising the name printing format, it is also possible to customise the actual fields printed using the certopt option 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 printing 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 openssl-ca(1) uses, equivalent to no_issuer, no_pubkey, no_header, and no_version. One preset doing four no's, we love a low-effort icon 💅

✨ EXAMPLES ✨

Quick note bestie: in these examples, the \ means the example should be all on one line. No cap.

Print the contents of a certificate:

openssl x509 -in cert.pem -noout -text

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

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

Print more extensions of a certificate:

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

Print the certificate serial number:

openssl x509 -in cert.pem -noout -serial

Print the certificate subject name:

openssl x509 -in cert.pem -noout -subject

Print the certificate subject name in RFC2253 form:

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

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

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

Print 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 -key 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 \
       -key 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 conversion to UTF8 format used with the name options assumes that T61Strings use the ISO8859-1 character set. That's wrong, but Netscape and MSIE do this, as do many certificates. So even though this is incorrect, it's more likely to print the majority of certificates correctly. Iconic messy legacy behavior, honestly 😭

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.

💀 BUGS 💀

It is possible to produce invalid certificates or requests by specifying the wrong private key, using unsuitable X.509 extensions, 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.

🫶 SEE ALSO 🫶

⏳ 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 openssl-rehash(1) or similar.

The -signkey option has been renamed to -key in OpenSSL 3.0, keeping the old name as an alias.

The -engine option was deprecated in OpenSSL 3.0.

The -C option was removed in OpenSSL 3.0.

Since OpenSSL 3.2, generated certificates bear X.509 version 3, and key identifier extensions are included by default.

Copyright 2000-2024 The OpenSSL Project Authors. All Rights Reserved.

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>.

That's a wrap on OPENSSL-X509(1ossl) — this page is from OpenSSL 3.5.9, dated 2026-09-29. Mwah, bestie 💜

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