X509_GET_EXTENSION_FLAGS(3SSL) OpenSSL X509_GET_EXTENSION_FLAGS(3SSL)
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_NO_FINGERPRINT
Failed to compute the internal SHA1 hash value of the certificate or
CRL. This may be due to malloc failure or because no SHA1
implementation was found.
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 2015-2021 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>.
3.5.7 2026-06-09 X509_GET_EXTENSION_FLAGS(3SSL)
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