Cryptography and SSL/TLS Toolkit



X509_VERIFY_PARAM_set_flags, X509_VERIFY_PARAM_clear_flags, X509_VERIFY_PARAM_get_flags, X509_VERIFY_PARAM_set_purpose, X509_VERIFY_PARAM_set_trust, X509_VERIFY_PARAM_set_depth, X509_VERIFY_PARAM_get_depth, X509_VERIFY_PARAM_set_auth_level, X509_VERIFY_PARAM_get_auth_level, X509_VERIFY_PARAM_set_time, X509_VERIFY_PARAM_add0_policy, X509_VERIFY_PARAM_set1_policies, X509_VERIFY_PARAM_set1_host, X509_VERIFY_PARAM_add1_host, X509_VERIFY_PARAM_set_hostflags, X509_VERIFY_PARAM_get0_peername, X509_VERIFY_PARAM_set1_email, X509_VERIFY_PARAM_set1_ip, X509_VERIFY_PARAM_set1_ip_asc - X509 verification parameters


 #include <openssl/x509_vfy.h>

 int X509_VERIFY_PARAM_set_flags(X509_VERIFY_PARAM *param,
                                        unsigned long flags);
 int X509_VERIFY_PARAM_clear_flags(X509_VERIFY_PARAM *param,
                                        unsigned long flags);
 unsigned long X509_VERIFY_PARAM_get_flags(X509_VERIFY_PARAM *param);

 int X509_VERIFY_PARAM_set_purpose(X509_VERIFY_PARAM *param, int purpose);
 int X509_VERIFY_PARAM_set_trust(X509_VERIFY_PARAM *param, int trust);

 void X509_VERIFY_PARAM_set_time(X509_VERIFY_PARAM *param, time_t t);

 int X509_VERIFY_PARAM_add0_policy(X509_VERIFY_PARAM *param,
                                        ASN1_OBJECT *policy);
 int X509_VERIFY_PARAM_set1_policies(X509_VERIFY_PARAM *param,
                                        STACK_OF(ASN1_OBJECT) *policies);

 void X509_VERIFY_PARAM_set_depth(X509_VERIFY_PARAM *param, int depth);
 int X509_VERIFY_PARAM_get_depth(const X509_VERIFY_PARAM *param);

 void X509_VERIFY_PARAM_set_auth_level(X509_VERIFY_PARAM *param,
                                        int auth_level);
 int X509_VERIFY_PARAM_get_auth_level(const X509_VERIFY_PARAM *param);

 int X509_VERIFY_PARAM_set1_host(X509_VERIFY_PARAM *param,
                                 const char *name, size_t namelen);
 int X509_VERIFY_PARAM_add1_host(X509_VERIFY_PARAM *param,
                                 const char *name, size_t namelen);
 void X509_VERIFY_PARAM_set_hostflags(X509_VERIFY_PARAM *param,
                                      unsigned int flags);
 char *X509_VERIFY_PARAM_get0_peername(X509_VERIFY_PARAM *param);
 int X509_VERIFY_PARAM_set1_email(X509_VERIFY_PARAM *param,
                                 const char *email, size_t emaillen);
 int X509_VERIFY_PARAM_set1_ip(X509_VERIFY_PARAM *param,
                               const unsigned char *ip, size_t iplen);
 int X509_VERIFY_PARAM_set1_ip_asc(X509_VERIFY_PARAM *param, const char *ipasc);


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 trust.

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 intermediate CA certificates that can appear in a chain. A maximal depth chain contains 2 more certificates than the limit, since neither the end-entity certificate nor the trust-anchor count against this limit. Thus a depth limit of 0 only allows the end-entity certificate to be signed directly by the trust-anchor, while with a depth limit of 1 there can be one intermediate CA certificate between the trust-anchor and the end-entity certificate.

X509_VERIFY_PARAM_set_auth_level() sets the authentication security level to auth_level. The authentication security level determines the acceptable signature and public key strength when verifying certificate chains. For a certificate chain to validate, the public keys of all the certificates must meet the specified security level. The signature algorithm security level is not enforced for the chain's trust anchor certificate, which is either directly trusted or validated by means other than its signature. See SSL_CTX_set_security_level for the definitions of the available levels. The default security level is -1, or "not set". At security level 0 or lower all algorithms are acceptable. Security level 1 requires at least 80-bit-equivalent security and is broadly interoperable, though it will, for example, reject MD5 signatures or RSA keys shorter than 1024 bits.

X509_VERIFY_PARAM_set1_host() sets the expected DNS hostname to name clearing any previously specified host name or names. If name is NULL, or empty the list of hostnames is cleared, and name checks are not performed on the peer certificate. If name is NUL-terminated, namelen may be zero, otherwise namelen must be set to the length of name. When a hostname is specified, certificate verification automatically invokes X509_check_host with flags equal to the flags argument given to X509_VERIFY_PARAM_set_hostflags() (default zero). Applications are strongly advised to use this interface in preference to explicitly calling X509_check_host, hostname checks are out of scope with the DANE-EE(3) certificate usage, and the internal check will be suppressed as appropriate when DANE support is added to OpenSSL.

X509_VERIFY_PARAM_add1_host() adds name as an additional reference identifier that can match the peer's certificate. Any previous names set via X509_VERIFY_PARAM_set1_host() or X509_VERIFY_PARAM_add1_host() are retained, no change is made if name is NULL or empty. When multiple names are configured, the peer is considered verified when any name matches.

X509_VERIFY_PARAM_get0_peername() returns the DNS hostname or subject CommonName from the peer certificate that matched one of the reference identifiers. When wildcard matching is not disabled, or when a reference identifier specifies a parent domain (starts with ".") rather than a hostname, the peer name may be a wildcard name or a sub-domain of the reference identifier respectively. The return string is allocated by the library and is no longer valid once the associated param argument is freed. Applications must not free the return value.

X509_VERIFY_PARAM_set1_email() sets the expected RFC822 email address to email. If email is NUL-terminated, emaillen may be zero, otherwise emaillen must be set to the length of email. When an email address is specified, certificate verification automatically invokes X509_check_email.

X509_VERIFY_PARAM_set1_ip() sets the expected IP address to ip. The ip argument is in binary format, in network byte-order and iplen must be set to 4 for IPv4 and 16 for IPv6. When an IP address is specified, certificate verification automatically invokes X509_check_ip.

X509_VERIFY_PARAM_set1_ip_asc() sets the expected IP address to ipasc. The ipasc argument is a NUL-terminal ASCII string: dotted decimal quad for IPv4 and colon-separated hexadecimal for IPv6. The condensed "::" notation is supported for IPv6 addresses.


X509_VERIFY_PARAM_set_flags(), X509_VERIFY_PARAM_clear_flags(), X509_VERIFY_PARAM_set_purpose(), X509_VERIFY_PARAM_set_trust(), X509_VERIFY_PARAM_add0_policy() X509_VERIFY_PARAM_set1_policies(), X509_VERIFY_PARAM_set1_host(), X509_VERIFY_PARAM_add1_host(), X509_VERIFY_PARAM_set1_email(), X509_VERIFY_PARAM_set1_ip() and X509_VERIFY_PARAM_set1_ip_asc() return 1 for success and 0 for failure.

X509_VERIFY_PARAM_get_flags() returns the current verification flags.

X509_VERIFY_PARAM_set_time() and X509_VERIFY_PARAM_set_depth() do not return values.

X509_VERIFY_PARAM_get_depth() returns the current verification depth.

X509_VERIFY_PARAM_get_auth_level() returns the current authentication security level.


The verification flags consists of zero or more of the following flags ored together.

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 chain.

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 performed. 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 are set.

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 is 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 certificate signature. By default this check is disabled because it doesn't 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.

If X509_V_FLAG_TRUSTED_FIRST is set, when constructing the certificate chain, X509_verify_cert will search the trust store for issuer certificates before searching the provided untrusted certificates. As of OpenSSL 1.1.0 this option is on by default and cannot be disabled.

The X509_V_FLAG_NO_ALT_CHAINS flag suppresses checking for alternative chains. By default, unless X509_V_FLAG_TRUSTED_FIRST is set, when building a certificate chain, if the first certificate chain found is not trusted, then OpenSSL will attempt to replace untrusted certificates supplied by the peer with certificates from the trust store to see if an alternative chain can be found that is trusted. As of OpenSSL 1.1.0, with X509_V_FLAG_TRUSTED_FIRST always set, this option has no effect.

The X509_V_FLAG_NO_CHECK_TIME flag suppresses checking the validity period of certificates and CRLs against the current time. If X509_VERIFY_PARAM_set_time() is used to specify a verification time, the check is not suppressed.


The above functions should be used to manipulate verification parameters instead of legacy functions which work in specific structures such as X509_STORE_CTX_set_flags().


Delta CRL checking is currently primitive. Only a single delta can be used and (partly due to limitations of X509_STORE) constructed CRLs are not maintained.

If CRLs checking is enable CRLs are expected to be available in the corresponding X509_STORE structure. No attempt is made to download CRLs from the CRL distribution points extension.


Enable CRL checking when performing certificate verification during SSL connections associated with an SSL_CTX structure ctx:

  X509_VERIFY_PARAM *param;
  param = X509_VERIFY_PARAM_new();
  X509_VERIFY_PARAM_set_flags(param, X509_V_FLAG_CRL_CHECK);
  SSL_CTX_set1_param(ctx, param);


X509_verify_cert, X509_check_host, X509_check_email, X509_check_ip


The X509_V_FLAG_NO_ALT_CHAINS flag was added in OpenSSL 1.1.0 The legacy X509_V_FLAG_CB_ISSUER_CHECK flag is deprecated as of OpenSSL 1.1.0, and has no effect.

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