NAME

       X509_get0_subject_key_id, X509_get0_authority_key_id, X509_get0_authority_issuer,
       X509_get0_authority_serial, X509_get_pathlen, X509_get_extension_flags, X509_get_key_usage,
       X509_get_extended_key_usage, X509_set_proxy_flag, X509_set_proxy_pathlen, X509_get_proxy_pathlen -
       retrieve certificate extension data

SYNOPSIS

        #include <openssl/x509v3.h>

        long X509_get_pathlen(X509 *x);
        uint32_t X509_get_extension_flags(X509 *x);
        uint32_t X509_get_key_usage(X509 *x);
        uint32_t X509_get_extended_key_usage(X509 *x);
        const ASN1_OCTET_STRING *X509_get0_subject_key_id(X509 *x);
        const ASN1_OCTET_STRING *X509_get0_authority_key_id(X509 *x);
        const GENERAL_NAMES *X509_get0_authority_issuer(X509 *x);
        const ASN1_INTEGER *X509_get0_authority_serial(X509 *x);
        void X509_set_proxy_flag(X509 *x);
        void X509_set_proxy_pathlen(int l);
        long X509_get_proxy_pathlen(X509 *x);

DESCRIPTION

       These functions retrieve information related to commonly used certificate extensions.

       X509_get_pathlen() retrieves the path length extension from a certificate.  This extension is used to
       limit the length of a cert chain that may be issued from that CA.

       X509_get_extension_flags() retrieves general information about a certificate, it will return one or more
       of the following flags ored together.

       EXFLAG_V1
           The certificate is an obsolete version 1 certificate.

       EXFLAG_BCONS
           The certificate contains a basic constraints extension.

       EXFLAG_CA
           The certificate contains basic constraints and asserts the CA flag.

       EXFLAG_PROXY
           The certificate is a valid proxy certificate.

       EXFLAG_SI
           The certificate is self issued (that is subject and issuer names match).

       EXFLAG_SS
           The subject and issuer names match and extension values imply it is self signed.

       EXFLAG_FRESHEST
           The freshest CRL extension is present in the certificate.

       EXFLAG_CRITICAL
           The certificate contains an unhandled critical extension.

       EXFLAG_INVALID
           Some  certificate  extension  values are invalid or inconsistent. The certificate should be rejected.
           This bit may also be raised after an out-of-memory error while processing the X509 object, so it  may
           not be related to the processed ASN1 object itself.

       EXFLAG_INVALID_POLICY
           The NID_certificate_policies certificate extension is invalid or inconsistent. The certificate should
           be  rejected.   This  bit  may  also be raised after an out-of-memory error while processing the X509
           object, so it may not be related to the processed ASN1 object itself.

       EXFLAG_KUSAGE
           The  certificate  contains  a   key   usage   extension.   The   value   can   be   retrieved   using
           X509_get_key_usage().

       EXFLAG_XKUSAGE
           The  certificate  contains  an  extended  key  usage  extension.  The  value  can  be retrieved using
           X509_get_extended_key_usage().

       X509_get_key_usage() returns the value of the key usage extension.  If key usage is present  will  return
       zero   or   more   of   the   flags:   KU_DIGITAL_SIGNATURE,   KU_NON_REPUDIATION,   KU_KEY_ENCIPHERMENT,
       KU_DATA_ENCIPHERMENT,    KU_KEY_AGREEMENT,    KU_KEY_CERT_SIGN,    KU_CRL_SIGN,    KU_ENCIPHER_ONLY    or
       KU_DECIPHER_ONLY  corresponding  to  individual key usage bits. If key usage is absent then UINT32_MAX is
       returned.

       X509_get_extended_key_usage() returns the value of the extended key  usage  extension.  If  extended  key
       usage  is  present  it  will return zero or more of the flags: XKU_SSL_SERVER, XKU_SSL_CLIENT, XKU_SMIME,
       XKU_CODE_SIGN XKU_OCSP_SIGN, XKU_TIMESTAMP, XKU_DVCS or XKU_ANYEKU. These correspond to the  OIDs  id-kp-
       serverAuth,   id-kp-clientAuth,   id-kp-emailProtection,   id-kp-codeSigning,  id-kp-OCSPSigning,  id-kp-
       timeStamping, id-kp-dvcs and anyExtendedKeyUsage respectively.  Additionally XKU_SGC  is  set  if  either
       Netscape or Microsoft SGC OIDs are present.

       X509_get0_subject_key_id()  returns  an  internal  pointer  to  the  subject  key  identifier  of x as an
       ASN1_OCTET_STRING or NULL if the extension is not present or cannot be parsed.

       X509_get0_authority_key_id() returns an internal pointer to the authority  key  identifier  of  x  as  an
       ASN1_OCTET_STRING or NULL if the extension is not present or cannot be parsed.

       X509_get0_authority_issuer()  returns  an  internal pointer to the authority certificate issuer of x as a
       stack of GENERAL_NAME structures or NULL if the extension is not present or cannot be parsed.

       X509_get0_authority_serial() returns an internal pointer to the authority certificate serial number of  x
       as an ASN1_INTEGER or NULL if the extension is not present or cannot be parsed.

       X509_set_proxy_flag()  marks  the certificate with the EXFLAG_PROXY flag.  This is for the users who need
       to mark non-RFC3820 proxy certificates as such, as OpenSSL only detects RFC3820 compliant ones.

       X509_set_proxy_pathlen() sets the proxy certificate path length for the given certificate x.  This is for
       the users who need to mark non-RFC3820 proxy certificates  as  such,  as  OpenSSL  only  detects  RFC3820
       compliant ones.

       X509_get_proxy_pathlen() returns the proxy certificate path length for the given certificate x if it is a
       proxy certificate.

NOTES

       The  value  of  the  flags  correspond to extension values which are cached in the X509 structure. If the
       flags returned do not provide sufficient information  an  application  should  examine  extension  values
       directly for example using X509_get_ext_d2i().

       If the key usage or extended key usage extension is absent then typically usage is unrestricted. For this
       reason  X509_get_key_usage()  and  X509_get_extended_key_usage() return UINT32_MAX when the corresponding
       extension is absent. Applications can additionally check the return value  of  X509_get_extension_flags()
       and take appropriate action is an extension is absent.

       If  X509_get0_subject_key_id()  returns  NULL then the extension may be absent or malformed. Applications
       can determine the precise reason using X509_get_ext_d2i().

RETURN VALUES

       X509_get_pathlen() returns the path length value, or -1 if the extension is not present.

       X509_get_extension_flags(), X509_get_key_usage() and X509_get_extended_key_usage() return sets  of  flags
       corresponding to the certificate extension values.

       X509_get0_subject_key_id()  returns  the  subject  key  identifier  as  a pointer to an ASN1_OCTET_STRING
       structure or NULL if the extension is absent or an error occurred during parsing.

       X509_get_proxy_pathlen() returns the path length value if the given certificate is a proxy one and has  a
       path length set, and -1 otherwise.

SEE ALSO

       X509_check_purpose(3)

HISTORY

       X509_get_pathlen(),  X509_set_proxy_flag(),  X509_set_proxy_pathlen()  and  X509_get_proxy_pathlen() were
       added in OpenSSL 1.1.0.

COPYRIGHT

       Copyright 2015-2020 The OpenSSL Project Authors. All Rights Reserved.

       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
       <https://www.openssl.org/source/license.html>.

1.1.1f                                             2025-02-05                     X509_GET_EXTENSION_FLAGS(3SSL)