=pod =head1 NAME X509_verify_cert - discover and verify X509 certificate chain =head1 SYNOPSIS #include int X509_verify_cert(X509_STORE_CTX *ctx); =head1 DESCRIPTION The X509_verify_cert() function attempts to discover and validate a certificate chain based on parameters in B. The verification context, of type B, can be constructed using L and L. It usually includes a set of certificates serving as trust anchors, a set of non-trusted certificates that may be needed 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 L 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() can occur if it is invoked incorrectly, such as with no certificate set in B, or when it is called twice in succession without reinitialising B for the second call. A negative return value can also happen due to internal resource problems or if a retry operation is requested during internal lookups (which never happens with standard lookup methods). Applications must check for <= 0 return value on error. =head1 RETURN VALUES If a complete chain can be built and validated this function returns 1, otherwise it return zero, in exceptional circumstances it can also return a negative code. If the function fails additional error information can be obtained by examining B using, for example L. =head1 BUGS This function uses the header F<< >> as opposed to most chain verification functions which use F<< >>. =head1 SEE ALSO L, L, L =head1 COPYRIGHT Copyright 2009-2020 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 L. =cut