X509_VERIFY_CERT(3ossl) OpenSSL X509_VERIFY_CERT(3ossl)
NAME
X509_build_chain, X509_verify_cert, X509_STORE_CTX_verify - build and
verify X509 certificate chain
SYNOPSIS
#include <openssl/x509_vfy.h>
STACK_OF(X509) *X509_build_chain(X509 *target, STACK_OF(X509) *certs,
X509_STORE *store, int with_self_signed,
OSSL_LIB_CTX *libctx, const char *propq);
int X509_verify_cert(X509_STORE_CTX *ctx);
int X509_STORE_CTX_verify(X509_STORE_CTX *ctx);
DESCRIPTION
X509_build_chain() builds a certificate chain starting from target
using the optional list of intermediate CA certificates certs. If
store is NULL it builds the chain as far down as possible, ignoring
errors. Else the chain must reach a trust anchor contained in store.
It internally uses a X509_STORE_CTX structure associated with the
library context libctx and property query string propq, both of which
may be NULL. In case there is more than one possibility for the chain,
only one is taken.
On success it returns a pointer to a new stack of (up_ref'ed)
certificates starting with target and followed by all available
intermediate certificates. A self-signed trust anchor is included only
if target is the trust anchor of with_self_signed is 1. If a non-NULL
stack is returned the caller is responsible for freeing it.
The X509_verify_cert(3) function attempts to discover and validate a
certificate chain based on parameters in ctx. The verification
context, of type X509_STORE_CTX, can be constructed using
X509_STORE_CTX_new(3) and X509_STORE_CTX_init(3). It usually includes
a target certificate to be verified, a set of certificates serving as
trust anchors, a list of non-trusted certificates that may be helpful
for chain construction, flags such as X509_V_FLAG_X509_STRICT, and
various other optional components such as a callback function that
allows customizing the verification outcome. A complete description of
the certificate verification process is contained in the
openssl-verification-options(1) manual page.
Applications rarely call this function directly but it is used by
OpenSSL internally for certificate validation, in both the S/MIME and
SSL/TLS code.
A negative return value from X509_verify_cert(3) can occur if it is
invoked incorrectly, such as with no certificate set in ctx, or when it
is called twice in succession without reinitialising ctx for the second
call. A negative return value can also happen due to internal resource
problems or because an internal inconsistency has been detected.
Applications must interpret any return value <= 0 as an error.
The X509_verify_cert(3) except that
its target certificate is the first element of the list of untrusted
certificates in ctx unless a target certificate is set explicitly.
When the verification target is a raw public key, rather than a
certificate, both functions validate the target raw public key. In
that case the number of possible checks is significantly reduced. The
raw public key can be authenticated only via DANE TLSA records, either
locally synthesised or obtained by the application from DNS. Raw
public key DANE TLSA records may be added via SSL_add_expected_rpk(3)
or SSL_dane_tlsa_add(3).
RETURN VALUES
X509_build_chain() returns NULL on error, else a stack of certificates.
Both X509_verify_cert(3) and X509_STORE_CTX_verify() return 1 if a
complete chain can be built and validated, otherwise they return 0, and
in exceptional circumstances (such as malloc failure and internal
errors) they can also return a negative code.
If a complete chain can be built and validated both functions return 1.
If the certificate must be rejected on the basis of the data available
or any required certificate status data is not available they return 0.
If no definite answer possible they usually return a negative code.
On error or failure additional error information can be obtained by
examining ctx using, for example, X509_STORE_CTX_get_error(3). Even if
verification indicated success, the stored error code may be different
from X509_V_OK, likely because a verification callback function has
waived the error.
SEE ALSO
SSL_add_expected_rpk(3), SSL_CTX_dane_enable(3), SSL_dane_tlsa_add(3),
X509_STORE_CTX_new(3), X509_STORE_CTX_init(3),
X509_STORE_CTX_init_rpk(3), X509_STORE_CTX_get_error(3)
HISTORY
X509_build_chain() and X509_STORE_CTX_verify() were added in OpenSSL
3.0.
COPYRIGHT
Copyright 2009-2023 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>.
3.3.2 2024-09-04 X509_VERIFY_CERT(3ossl)
openssl 3.3.2 - Generated Sun Sep 29 07:42:34 CDT 2024