OPENSSL-X509(1ossl)

📦
version 15.1 · 2 versions
, in freebsd 15.1

🌸 OPENSSL-X509(1ossl) 🌸

okay bestie, welcome to the certificate command. this is openssl-x509 from the OpenSSL fam — it's giving "swiss army knife but make it a manpage" energy, and honestly? iconic. let's get into it 💅

✨ NAME ✨

openssl-x509 — certificate display and signing command. that's the whole vibe. it shows you certs, it signs certs, it's a whole multihyphenate 👑

🦋 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|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]

like yeah it's a lot. we'll get through it together 🫶

💖 DESCRIPTION 💖

so this command is a multi-purpose certificate handling situation. it does so many things, and it does them well, no cap. here's the rundown:

  • it prints certificate information 📋
  • it converts certificates into various forms 🔄
  • it edits certificate trust settings 🛠️
  • it generates certificates from scratch, or from certification requests — and then either self-signs them or signs them like a little "micro CA" 👑

certificates it generates bear X.509 version 3. periodt. and unless you say otherwise, key identifier extensions get included exactly as described in x509v3_config(5) — that's just the default behaviour, iykyk.

and because there are soooo many options (like, an unhinged number), they're split up into various sections below so your brain doesn't melt 💀

🌈 OPTIONS 🌈

🎀 Input, Output, and General Purpose Options

  • -help — prints out a usage message. tiny helpful king 👑
  • -in filename|uri — this picks the input to read a certificate from, or the input file to read a certificate request from if the -req flag is being used. in both cases, this defaults to standard input.
heads up bestie: this option cannot be combined with the -new flag. they do not coexist, fr fr 🙈
  • -passin arg — the key and certificate file password source. for the full tea on how arg is formatted, go peek at openssl-passphrase-options(1) 🔑
  • -new — generates a certificate from scratch, not using an input certificate or certificate request. so yes, this excludes the -in and -req options entirely. instead, you need to give the -set_subject option. the public key that goes into it can be handed over with the -force_pubkey option, and it defaults to the key given with the -key (or -signkey) option — which implies a self-signature ✨
  • -x509toreq — outputs a PKCS#10 certificate request instead of a certificate. the -key (or -signkey) option is required here to give the private key for self-signing; the corresponding public key gets placed in the subjectPKInfo field. X.509 extensions that were in the certificate input are not copied by default. any X.509 extensions you actually want 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, and it must be correctly self-signed. X.509 extensions that were in the request are not copied by default. any X.509 extensions you want added can be specified using the -extfile option.
  • -copy_extensions arg — decides how X.509 extensions get handled when you're converting from a certificate to a request with the -x509toreq option, or converting from a request to a certificate with the -req option. if arg is none, or this option just isn't present, then extensions get ignored. if arg is copy or copyall, then all extensions are copied — except that the 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 actually get copied 🎯
  • -inform DER|PEM — the input file format to use; by default PEM is tried first. see openssl-format-options(1) for the details.
  • -vfyopt nm:v — passes options along to the signature algorithm during verify operations. the names and values of these options are algorithm-specific, so it's giving "you'll know if you know" 🤷‍♀️
  • -key filename|uri — this one provides the private key for signing a new certificate or certificate request. unless -force_pubkey is given, the corresponding public key gets placed in the new certificate or certificate request, which results in a self-signature.
this option cannot be used together with the -CA option. that's a hard no 💀

it sets the issuer name to the subject name (i.e., it makes the thing self-issued). and 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 the -not_before and -not_after options.

  • -signkey filename|uri — this option is an alias of -key. same thing, different name, we love a rebrand 💅
  • -keyform DER|PEM|P12|ENGINE — the key input format; unspecified by default. see openssl-format-options(1) for details.
  • -out filename — 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 the options below). so it's a "print only, no cert" mood.
  • -noout — this option prevents output, except for printing as requested by the options below. same energy, different flag 🎀

🦋 Certificate Printing Options

note, bestie: the -alias and -purpose options are also printing options, but they get described down in the "Trust Settings" section. just so you don't go looking for them here and get confused 🫶
  • -dateopt — specify the date output format. the values are: rfc_822 and iso_8601. defaults to rfc_822. 📅
  • -text — prints out the certificate in text form. full details get printed, including the public key, signature algorithms, issuer and subject names, serial number, any extensions present, and any trust settings. it's the full unboxing video, no skips ✨
  • -certopt option — customises 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 info.
  • -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. it's basically the cert's government name 🫡
  • -alias — prints the certificate "alias" (nickname), if any. cute.
  • -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. two for one, we love efficiency 💖
  • -subject — prints the subject name.
  • -issuer — prints the issuer name.
  • -nameopt option — specifies how the subject or issuer names get displayed. see openssl-namedisplay-options(1) for the details.
  • -email — prints the email address(es), if any.
  • -hash — synonym for -subject_hash, kept around for backward compatibility reasons. legacy queen 👑
  • -subject_hash — prints the "hash" of the certificate subject name. this is used in OpenSSL to form an index so certificates sitting in a directory can be looked up by subject name. very "let me find your file for you" of it 📂
  • -subject_hash_old — prints the "hash" of the certificate subject name using the older algorithm, as used by OpenSSL before version 1.0.0. throwback 🕰️
  • -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 get copied. 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). it's the vibe check for your cert 🔍
  • -pubkey — prints the certificate's SubjectPublicKeyInfo block in PEM format.
  • -modulus — 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. binary answer, no nuance, love that for us 💀
  • -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 it's preceded by "0x". 🔢
  • -next_serial — set the serial to be one more than the number in the certificate. math but make it certificate 💅
  • -not_before date — lets the start date 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. pick a lane, bestie 🙈
  • -not_after date — okay so this one lets you literally just say when the cert expires ✨. The date format is YYMMDDHHMMSSZ (same shape as an ASN1 UTCTime structure) or YYYYMMDDHHMMSSZ (same shape as an ASN1 GeneralizedTime structure). In both formats the seconds SS and the timezone Z have to be there — no skipping them, bestie 🫶. You can also just write "today" and call it a day.
🚫 Cannot be used together with the -preserve_dates option. Also heads up: this overrides the -days option.
  • -days arg — tells it how many days from today until a newly generated certificate expires. Default is 30, cutie 🎀.
🚫 Cannot be used together with the -preserve_dates option. And if the -not_after option is set, that explicit expiry date takes precedence — it wins, periodt.
  • -preserve_dates — when signing a certificate, this keeps the "notBefore" and "notAfter" dates of whatever input certificate you handed over, instead of adjusting them to current time and duration. Like, it respects the original vibe 💅.
🚫 Cannot be used together with the -days, -not_before and -not_after options.
  • -set_issuer arg — when a certificate is created, this sets its issuer name to the given value.

Peep -set_subject below for how the arg has to be formatted — same rules, no cap.

  • -set_subject arg — when a certificate is created, this sets its subject name to the given value. And when the certificate is self-signed, the issuer name gets set to the same value too — unless you also give -set_issuer, bestie 👑

The arg must be formatted as "/type0=value0/type1=value1/type2=...". Special characters can be escaped with "\" (backslash), and whitespace is retained. Empty values are permitted, but then that type just won't be included in the certificate. Giving a single "/" leads to an empty sequence of RDNs (a NULL-DN) — iconic little edge case 😌. Multi-valued RDNs can be formed 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 the -new and -force_pubkey options to create a new certificate without providing an input certificate or certificate request. Slay, no input needed 🌈.

  • -subj arg — this one's just an alias of -set_subject. Same thing, shorter name, we love a nickname 💖.
  • -force_pubkey filename — when a new certificate or certificate request is created, this sets its public key to the given key instead of the key contained in the input or given with the -key (or -signkey) option. And 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. So good.

It's also useful for creating self-issued certificates that are not self-signed — for instance when the key can't be used for signing, such as DH. Big fan of a cert that knows what it is 💅.

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

When transforming a certificate or certificate request, -clrext prevents taking over any extensions from the source. And in any case, when producing a certificate request, neither subject identifier nor authority key identifier extensions are included. Not up for discussion 🌸.

  • -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 isn't 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. Sneaky, but it works 🧚.

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

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

  • -sigopt nm:v — passes options to the signature algorithm during sign operations. This option may be given multiple times 🔥, and the names and values you provide using it are algorithm-specific.
  • -badsig — corrupts the signature before writing it; this can be useful for testing. Yes bestie, it's on purpose 💀.
  • -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 you don't specify one, then SHA1 is used with -fingerprint, or the default digest for the signing algorithm is used — typically SHA256. Defaults doing their thing, we respect it 👑

💅 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. Tiny CA, huge main character energy 👑✨.
🚫 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. Fresh start, baby 🦋.
  • -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 isn't provided, then the key must be present in the -CA input. No mismatches allowed, ngl 🔐.
  • -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's incremented and used, and the file is updated. Little counter that keeps on counting 🔢.

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 — and 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. Creation station 🎀.

🌸 Trust Settings 🌸

A trusted certificate is an ordinary certificate which has several additional pieces of information attached to it — stuff like 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. Root CA = the final boss 👑.

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. Selective trust, we love to see it 💅.

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. Manifesting this fr fr.
  • -trustout — marks any certificate PEM output as a <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. And a trusted certificate is automatically output if any trust settings are modified — it just knows ✨.
  • -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. Reset button, go 💅.
  • -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. Symmetry, bestie 🦋.

⭐ Generic options ⭐

  • -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. Like, old news.
  • -provider name
  • -provider-path path
  • -provparam [name:]key=value
  • -propquery propq

See "Provider Options" in openssl(1), provider(7), and property(7). Provider gang 🌈.

🎀 Text Printing Flags 🎀

As well as customising the name printing format, you can also customise the actual fields printed using the certopt option when the text option is present. The default behaviour is to print all fields. Everything on, by default ✨.

  • compatible — use the old format. This is equivalent to specifying no printing options at all. Throwback vibes 🦋.
  • 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 that openssl-ca(1) uses, and it's literally the same as setting no_issuer, no_pubkey, no_header, and no_version all at once. slay 💅

🌸 EXAMPLES 🌸

📝 Note: in these examples the '\' means the example should be all on one line. no cap, that's just the rule 😌

Print the contents of a certificate — the classic "show me everything" move:

openssl x509 -in cert.pem -noout -text

Print the "Subject Alternative Name" extension of a certificate — just the SAN, nothing extra:

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

Print more extensions of a certificate — okay bestie, now we're asking for multiple:

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

Print the certificate serial number — the cert's little ID number:

openssl x509 -in cert.pem -noout -serial

Print the certificate subject name — who even is she:

openssl x509 -in cert.pem -noout -subject

Print the certificate subject name in RFC2253 form — fancy formatting unlocked:

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

Print the certificate subject name in oneline form on a terminal supporting UTF8 — cute little one-liner, UTF8-friendly:

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

Print the certificate SHA1 fingerprint — a whole SHA1 moment:

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

Convert a certificate from PEM to DER format — glow-up from text to binary:

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

Convert a certificate to a certificate request — reverse uno card:

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 — main character CA energy:

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 — yes, we're signing with the CA we just made:

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" — trust fall but make it certificate:

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. This is wrong but Netscape and MSIE do this as do many certificates. So although this is incorrect it is more likely to print the majority of certificates correctly. yeah, it's a whole legacy vibe 😭

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. periodt, no duplicates 💅

💀 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. bestie please double-check your flags, this is not a drill 🙈

There should be options to explicitly set such things as start and end dates rather than an offset from the current time. lowkey yes, we deserve that 😤

🌈 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. glow-up gone right ✨

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

The -engine option was deprecated in OpenSSL 3.0. rip bozo 🫶

The -C option was removed in OpenSSL 3.0. gone, reduced to atoms 💀

Since OpenSSL 3.2, generated certificates bear X.509 version 3, and key identifier extensions are included by default. newer, shinier, very version-3 of them 🎀

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>. legal bestie stuff, but make it official 💜

okay bestie, that's the whole OPENSSL-X509(1ossl) page — brought to you by OpenSSL 3.5.6, dated 2026-04-07 💖✨ go forth and inspect those certs, ily 🫶

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