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 ctx using, for example X509_STORE_CTX_get_error().
NOTES
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 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 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.
BUGS
This function uses the header x509.h as opposed to most chain verification functions which use x509_vfy.h.
SEE ALSO
COPYRIGHT
Copyright 2009-2016 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.