SSL_CTX_set_cert_verify_callback - set peer certificate verification procedure
#include <openssl/ssl.h> void SSL_CTX_set_cert_verify_callback(SSL_CTX *ctx, int (*callback)(X509_STORE_CTX *,void *), void *arg);
OpenSSL SSL_CTX_set_cert_verify_callback(3openssl)
NAME
SSL_CTX_set_cert_verify_callback - set peer certificate verification
procedure
SYNOPSIS
#include <openssl/ssl.h>
void SSL_CTX_set_cert_verify_callback(SSL_CTX *ctx, int (*callback)(X509_STORE_CTX *,void *), void *arg);
DESCRIPTION
SSL_CTX_set_cert_verify_callback() sets the verification callback
function for ctx. SSL objects that are created from ctx inherit the
setting valid at the time when SSL_new(3) is called.
ATTRIBUTES
See attributes(7) for descriptions of the following attributes:
+---------------+--------------------------+
|ATTRIBUTE TYPE | ATTRIBUTE VALUE |
+---------------+--------------------------+
|Availability | library/security/openssl |
+---------------+--------------------------+
|Stability | Pass-through uncommitted |
+---------------+--------------------------+
NOTES
Whenever a certificate is verified during a SSL/TLS handshake, a
verification function is called. If the application does not explicitly
specify a verification callback function, the built-in verification
function is used. If a verification callback callback is specified via
SSL_CTX_set_cert_verify_callback(), the supplied callback function is
called instead. By setting callback to NULL, the default behaviour is
restored.
When the verification must be performed, callback will be called with
the arguments callback(X509_STORE_CTX *x509_store_ctx, void *arg). The
argument arg is specified by the application when setting callback.
callback should return 1 to indicate verification success and 0 to
indicate verification failure. If SSL_VERIFY_PEER is set and callback
returns 0, the handshake will fail. As the verification procedure may
allow to continue the connection in case of failure (by always
returning 1) the verification result must be set in any case using the
error member of x509_store_ctx so that the calling application will be
informed about the detailed result of the verification procedure!
Within x509_store_ctx, callback has access to the verify_callback
function set using SSL_CTX_set_verify(3).
Source code for open source software components in Oracle Solaris can
be found at https://www.oracle.com/downloads/opensource/solaris-source-
code-downloads.html.
This software was built from source available at
https://github.com/oracle/solaris-userland. The original community
source was downloaded from
https://www.openssl.org/source/openssl-1.0.2ze.tar.gz.
Further information about this software can be found on the open source
community website at https://www.openssl.org/.
WARNINGS
Do not mix the verification callback described in this function with
the verify_callback function called during the verification process.
The latter is set using the SSL_CTX_set_verify(3) family of functions.
Providing a complete verification procedure including certificate
purpose settings etc is a complex task. The built-in procedure is quite
powerful and in most cases it should be sufficient to modify its
behaviour using the verify_callback function.
BUGS
RETURN VALUES
SSL_CTX_set_cert_verify_callback() does not provide diagnostic
information.
SEE ALSO
ssl(3), SSL_CTX_set_verify(3), SSL_get_verify_result(3),
SSL_CTX_load_verify_locations(3)
HISTORY
Previous to OpenSSL 0.9.7, the arg argument to
SSL_CTX_set_cert_verify_callback was ignored, and callback was called
simply as
int (*callback)(X509_STORE_CTX *) To compile software written for
previous versions of OpenSSL, a dummy argument will have to be added to
callback.
1.0.2ze 2022-05-03
SSL_CTX_set_cert_verify_callback(3openssl)