x509(7ssl)

x5097ssl

X.509 certificate handling

Usage

 #include <openssl/x509.h>

Overview

An X.509 certificate is a structured grouping of information about an individual, a device, or anything one can imagine. An X.509 CRL (certificate revocation list) is a tool to help determine if a certificate is still valid. The exact definition of those can be found in the X.509 document from ITU-T, or in RFC3280 from PKIX. In OpenSSL, the type X509 is used to express such a certificate, and the type X509_CRL is used to express a CRL.

A related structure is a certificate request, defined in PKCS#10 from RSA Security, Inc, also reflected in RFC2896. In OpenSSL, the type X509_REQ is used to express such a certificate request.

To handle some complex parts of a certificate, there are the types X509_NAME (to express a certificate name), X509_ATTRIBUTE (to express a certificate attribute), X509_EXTENSION (to express a certificate extension) and a few more.

Finally, there's the supertype X509_INFO, which can contain a CRL, a certificate and a corresponding private key.

X509_XXX, d2i_X509_XXX, and i2d_X509_XXX functions handle X.509 certificates, with some exceptions, shown below.

X509_CRL_XXX, d2i_X509_CRL_XXX, and i2d_X509_CRL_XXX functions handle X.509 CRLs.

X509_REQ_XXX, d2i_X509_REQ_XXX, and i2d_X509_REQ_XXX functions handle PKCS#10 certificate requests.

X509_NAME_XXX functions handle certificate names.

X509_ATTRIBUTE_XXX functions handle certificate attributes.

X509_EXTENSION_XXX functions handle certificate extensions.

Releases

6 releases since Debian 9 (Stretch); the text changed 5 times.

  1. 9
  2. 10
  3. 11
  4. 12
  5. 13
  6. Arch

From openssl 3.6.5-1 in Arch Linux 2026-11-01. Parsed by carta from the page's man source.