OPENSSL-X509(1SSL)

📦
version 4.0.3 · 13 versions
, in ubuntu stonking

💖 openssl-x509 (1SSL) 💖

okay bestie, this is openssl-x509 from the 1SSL manual — cert display and signing, but make it make sense. 💅

✨ NAME ✨

  • openssl-x509 — Certificate display and signing command. 🎀

✨ SYNOPSIS ✨

       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] [-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] [-multi] [-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] [-CAserial filename]
       [-CAcreateserial] [-trustout] [-setalias arg] [-clrtrust] [-addtrust
       arg] [-clrreject] [-addreject arg] [-rand files] [-writerand file]
       [-provider name] [-provider-path path] [-provparam [name:]key=value]
       [-propquery propq]

✨ DESCRIPTION ✨

This command is a multi-purpose certificate-handling queen. She can print certificate information, convert certificates to various forms, edit certificate trust settings, generate certificates from scratch or from certification requests, and then self-sign them or sign 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. No cap.

👑 OPTIONS 👑

🛠️ Input, Output, and General Purpose Options 🛠️

  • -help — Print out a usage message. Because a little reminder never hurt nobody. 🫶
  • -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 — 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: the -alias and -purpose options are also printing options, but they are described in the "Trust Settings" section.
  • -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 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. 🧮
  • -multi — This option prints selected information about all certificates contained in the input. 🧺

🔎 Certificate Checking Options 🔎

  • -checkend arg — Without -multi, checks if the certificate expires within the next arg seconds and exits nonzero if it will expire, or zero if not. ⏳ With -multi, checks if any certificate in the input will expire within the next arg seconds and exits nonzero if any will expire, or zero if none will.
  • -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 one lets you straight up hardcode when the cert dies. The date format is YYMMDDHHMMSSZ (same vibe as an ASN1 UTCTime structure), or YYYYMMDDHHMMSSZ (same as an ASN1 GeneralizedTime structure). In both formats, the seconds SS and the timezone Z must be there, no skipping. You can also just write "today" if that's the energy you're on.

Not compatible with -preserve_dates, bestie, pick a lane. And heads up: this one overrides the -days option entirely.

  • -days arg — how many days from today until a freshly generated certificate says goodbye. Default is 30.

Cannot be used together with -preserve_dates. And if -not_after is set, that explicit expiry date wins, periodt.

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

Peep -set_subject for how the arg has to be formatted.

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

The arg must be formatted as "/type0=value0/type1=value1/type2=...". Special characters can be escaped with "\" (backslash), and whitespace is retained, no cap. Empty values are allowed, but then that type won't show up in the certificate at all. Giving a single "/" gets you an empty sequence of RDNs (a NULL-DN). Multi-valued RDNs? Form them by putting 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 -new and -force_pubkey to create a whole new certificate without providing an input certificate or certificate request. Iconic behaviour, honestly.

  • -subj arg — this option is an alias of -set_subject. Same girl, different name 💅
  • -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 does contain a private key, its public part gets used.

This one can vibe with -new and -set_subject to directly generate a certificate containing literally any public key you want.

Also super useful for creating self-issued certificates that are not self-signed — for instance when the key can't be used for signing, like with DH.

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

But when transforming a certificate or certificate request, -clrext stops any extensions from being taken over from the source. In any case, when producing a certificate request, neither the subject identifier nor the authority key identifier extensions are included.

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

When both -extfile filename and -extensions section options are given, the extensions to add come from the named section of the file named filename. That file must exist, be readable, and all the listed extensions must be valid.

If only the -extfile filename option is given, the section name to use comes from the value of the variable named "extensions" in the file's unnamed section (also called its default section, see config(5)). If no extensions setting is found, the file's default (unnamed) section itself is used instead as the list of extensions to add. As before, the file must be readable and all the extensions must be valid.

Prior to OpenSSL 4.0, the -extensions option required that the -extfile option be also specified. As of OpenSSL 4.0 the default configuration file is used instead, as described below.

If only the -extensions section option is given, the named section of the default configuration file — whether from the "OPENSSL_CONF" environment variable, or the built-in default — is used as the list of extensions to add. As before, the file must be readable and all the extensions must be valid.

If neither option is given, an attempt is made to open the default configuration file (as detailed above). If the file doesn't exist or can't be opened, no extensions are added. If the unnamed section (default, see config(5)) of the file doesn't list an extensions variable, no extensions are added. Otherwise, the section named by the extensions variable is taken to be the list of extensions to add. The extensions listed there must all be valid.

  • -extensions section — the section in the extfile to add X.509 extensions from. See the description of -extfile above for the deets.

And see the x509v3_config(5) manual page for details of the extension section format.

  • -sigopt nm:v — pass options to the signature algorithm during sign operations. You can give this one multiple times. The names and values you provide with it are algorithm-specific.
  • -badsig — corrupt the signature before writing it. Lowkey 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 works. 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", like so: the subject name of the "CA" certificate is placed as the 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). It's 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 you don't provide this option, then the key must be present in the -CA input.
  • -CAkeyform DER|PEM|P12 — 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 gets 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's incremented and used, and the file is updated.

The default filename is 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 doesn't 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 just an ordinary certificate that has several extra pieces of information attached to it, like the permitted and prohibited uses of the certificate and possibly an "alias" (nickname). Main character with a nickname? We love to see it.

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 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 info on what trust settings actually mean.

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 -trustout 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 lets the certificate 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, that last one 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 ✨

  • -rand files, -writerand file — see "Random State Options" in openssl(1) for details.
  • -provider name
  • -provider-path path
  • -provparam [name:]key=value
  • -propquery propq — see "Provider Options" in openssl(1), provider(7), and property(7).

As well as customising the name printing format, you can also pick and choose which actual fields get printed — that's the certopt option doing its thing, but it only works when text is also in the mix. Default vibe? Everything gets printed, no skips. 🎀

  • compatible — brings back the old format. Same energy as passing literally zero printing options. Nostalgia core.
  • no_header — skip the header info, aka those little lines that say Certificate and Data.
  • no_version — the version number stays unprinted. Not invited to the party.
  • no_serial — no serial number for you.
  • no_signame — the signature algorithm used isn't printed. Shy behavior honestly.
  • no_validity — validity is not printed, meaning the notBefore and notAfter fields get skipped.
  • no_subject — the subject name is staying home.
  • no_issuer — issuer name? not printed. 💅
  • no_pubkey — the public key isn't printed out.
  • no_sigdump — you don't get a hexadecimal dump of the certificate signature.
  • no_aux — certificate trust information isn't printed.
  • no_extensions — zero X509V3 extensions printed. none. gone. ✨
  • ext_default — keeps the default extension behaviour: it attempts to print out certificate extensions that aren't supported.
  • ext_error — prints an error message for unsupported certificate extensions instead.
  • ext_parse — does an ASN1 parse on unsupported extensions.
  • ext_dump — hex dumps unsupported extensions.
  • ca_default — this is the value openssl-ca(1) uses, and it's equivalent to no_issuer, no_pubkey, no_header, and no_version all together. the group chat bundle 🫶

🌈 EXAMPLES 🌈

okay quick heads up bestie: in all of these, when you see a \, that means the example is supposed to be all on one line. it's a line-continuation thing, not a "type the backslash" thing. 🙈

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

Check if any certificates in a chain are due to expire within the next 30 days (returns zero if none will expire, nonzero if any will expire):

openssl x509 -in chain.pem -multi -checkend $[3600*24*30] \
       && echo 'perform renewal' || echo 'renewal unnecessary'

📝 NOTES 📝

The conversion to UTF8 format that the name options use assumes T61Strings are using the ISO8859-1 character set. wild, because that's actually wrong — but Netscape and MSIE do it this way, and so do a whole lot of certificates. So yeah, it's incorrect, but it's way more likely to print the majority of certificates correctly. choosing incorrectness that works, iconic honestly. 😭

The -email option searches the subject name and the subject alternative name extension. Only unique email addresses get printed — it won't print the same address more than once. no duplicates, we keep it clean. ✨

💀 BUGS 💀

ngl you can end up producing invalid certificates or requests by specifying the wrong private key, by using unsuitable X.509 extensions, or by using inconsistent options in some cases. these should be checked. please check them. ⚠️

There should be options to explicitly set things like start and end dates rather than only an offset from the current time. it's giving "missing feature" fr fr.

👀 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's based on a canonical version of the DN using SHA1. Which means any directories still using the old form have to get their links rebuilt with openssl-rehash(1) or something similar. sorry to that one directory. 🫶

The -signkey option got renamed to -key in OpenSSL 3.0, and the old name is kept as an alias. so it's fine either way, lowkey.

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. slay ✨

The -engine option was removed in OpenSSL 4.0.

OpenSSL 4.0 added support for specifying extensions to add via the default configuration file. See -extfile above for details.

As of OpenSSL 4.0, the x509 utility no longer has specialised built-in logic to add the SKID or AKID extensions — they're handled through configuration files and command-line options just like any other extension. no special treatment, periodt. 👑

Copyright 2000-2026 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>.

okay that's the whole page, bestie, you made it to the end 🎀 this was version 4.0.3, dated 2026-09-29, and it's the OPENSSL-X509(1SSL) manual page. go forth and inspect some certs, you absolute main character. 💖🦋

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