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_time,
     X509_VERIFY_PARAM_set1_host, X509_VERIFY_PARAM_add1_host,
     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);

      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.

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     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

     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

     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 chain.

     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(3) with flags equal to
     the flags argument given to
     XX550099_VVEERRIIFFYY_PPAARRAAMM_sseett_hhoossttffllaaggss(()) (default zero).
     Applications are strongly advised to use this interface in
     preference to explicitly calling X509_check_host(3),
     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.

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     X509_VERIFY_PARAM_add1_host() adds name as an additional
     reference identifer 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

     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_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(3).

     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_set1_email(), X509_VERIFY_PARAM_set1_ip()
     and X509_VERIFY_PARAM_set1_ip_asc() return 1 for success and
     0 for failure.

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     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.


     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

     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_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.

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     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 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.

     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

     The X509_V_FLAG_TRUSTED_FIRST flag causes chain construction
     to look for issuers in the trust store before looking at the
     untrusted certificates provided as part of the the peer
     chain.  Though it is not on by default in OpenSSL 1.0.2,
     applications should generally set this flag.  Local issuer
     certificates are often more likely to satisfy local security
     requirements and lead to a locally trusted root.  This is
     especially important When some certificates in the trust
     store have explicit trust settings (see "TRUST SETTINGS" in

     The X509_V_FLAG_PARTIAL_CHAIN flag causes intermediate
     certificates in the trust store to be treated as
     trust-anchors, in the same way as the self-signed root CA
     certificates.  This makes it possible to trust certificates
     issued by an intermediate CA without having to trust its
     ancestor root CA.  With OpenSSL 1.0.2, chain construction
     continues as long as there are additional trusted issuers in
     the trust store, and the last trusted issuer becomes the
     trust-anchor.  Thus, even when an intermediate certificate
     is found in the trust store, the verified chain passed to

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     callbacks may still be anchored by a root CA.


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


     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


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

       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(3), X509_check_host(3),
     X509_check_email(3), X509_check_ip(3), x509(1)


     The X509_V_FLAG_NO_ALT_CHAINS flag was added in OpenSSL

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