These functions manipulate the X509_VERIFY_PARAM structure associated with
a certificate verification operation.
The X509_VERIFY_PARAM_set_flags() function sets the flags in param by oring
it with flags. See the VERIFICATION FLAGS section for a complete
description of values the flags parameter can take.
X509_VERIFY_PARAM_get_flags() returns the flags in param.
X509_VERIFY_PARAM_clear_flags() clears the flags flags in param.
X509_VERIFY_PARAM_set_purpose() sets the verification purpose in param
to purpose. This determines the acceptable purpose of the certificate
chain, for example SSL client or SSL server.
X509_VERIFY_PARAM_set_trust() sets the trust setting in param to
X509_VERIFY_PARAM_set_time() sets the verification time in param to
t. Normally the current time is used.
X509_VERIFY_PARAM_add0_policy() enables policy checking (it is disabled
by default) and adds policy to the acceptable policy set.
X509_VERIFY_PARAM_set1_policies() enables policy checking (it is disabled
by default) and sets the acceptable policy set to policies. Any existing
policy set is cleared. The policies parameter can be NULL to clear
an existing policy set.
X509_VERIFY_PARAM_set_depth() sets the maximum verification depth to depth.
That is the maximum number of untrusted CA certificates that can appear in a
The verification flags consists of zero or more of the following flags
X509_V_FLAG_CRL_CHECK enables CRL checking for the certificate chain leaf
certificate. An error occurs if a suitable CRL cannot be found.
X509_V_FLAG_CRL_CHECK_ALL enables CRL checking for the entire certificate
X509_V_FLAG_IGNORE_CRITICAL disabled critical extension checking. By default
any unhandled critical extensions in certificates or (if checked) CRLs results
in a fatal error. If this flag is set unhandled critical extensions are
ignored. WARNING setting this option for anything other than debugging
purposes can be a security risk. Finer control over which extensions are
supported can be performed in the verification callback.
THe X509_V_FLAG_X509_STRICT flag disables workarounds for some broken
certificates and makes the verification strictly apply X509 rules.
X509_V_FLAG_ALLOW_PROXY_CERTS enables proxy certificate verification.
X509_V_FLAG_POLICY_CHECK enables certificate policy checking, by default
no policy checking is peformed. Additional information is sent to the
verification callback relating to policy checking.
X509_V_FLAG_EXPLICIT_POLICY, X509_V_FLAG_INHIBIT_ANY and
X509_V_FLAG_INHIBIT_MAP set the require explicit policy, inhibit any
policy and inhibit policy mapping flags respectively as defined in
RFC3280. Policy checking is automatically enabled if any of these flags
If X509_V_FLAG_NOTIFY_POLICY is set and the policy checking is successful
a special status code is set to the verification callback. This permits it
to examine the valid policy tree and perform additional checks or simply
log it for debugging purposes.
By default some additional features such as indirect CRLs and CRLs signed by
different keys are disabled. If X509_V_FLAG_EXTENDED_CRL_SUPPORT is set
they are enabled.
If X509_V_FLAG_USE_DELTAS ise set delta CRLs (if present) are used to
determine certificate status. If not set deltas are ignored.
X509_V_FLAG_CHECK_SS_SIGNATURE enables checking of the root CA self signed
cerificate signature. By default this check is disabled because it doesnt
add any additional security but in some cases applications might want to
check the signature anyway. A side effect of not checking the root CA
signature is that disabled or unsupported message digests on the root CA
are not treated as fatal errors.
The X509_V_FLAG_CB_ISSUER_CHECK flag enables debugging of certificate
issuer checks. It is not needed unless you are logging certificate
verification. If this flag is set then additional status codes will be sent
to the verification callback and it must be prepared to handle such cases
without assuming they are hard errors.
The X509_V_FLAG_NO_ALT_CHAINS flag suppresses checking for alternative
chains. By default, when building a certificate chain, if the first certificate
chain found is not trusted, then OpenSSL will continue to check to see if an
alternative chain can be found that is trusted. With this flag set the behaviour
will match that of OpenSSL versions prior to 1.0.1n and 1.0.2b.