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NAME

       X509_VERIFY_PARAM_set_flags, X509_VERIFY_PARAM_clear_flags, X509_VERIFY_PARAM_get_flags,
       X509_VERIFY_PARAM_set_purpose, X509_VERIFY_PARAM_get_inh_flags,
       X509_VERIFY_PARAM_set_inh_flags, 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_get_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_get_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

SYNOPSIS

        #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_inh_flags(X509_VERIFY_PARAM *param,
                                            uint32_t flags);
        uint32_t X509_VERIFY_PARAM_get_inh_flags(const 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);
        time_t X509_VERIFY_PARAM_get_time(const X509_VERIFY_PARAM *param);

        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);
        unsigned int X509_VERIFY_PARAM_get_hostflags(const X509_VERIFY_PARAM *param);
        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);

DESCRIPTION

       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_get_inh_flags() returns the inheritance flags in param which specifies
       how verification flags are copied from one structure to another.
       X509_VERIFY_PARAM_set_inh_flags() sets the inheritance flags.  See the INHERITANCE FLAGS
       section for a description of these bits.

       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(3) 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(3) 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(3), hostname checks
       may be out of scope with the DANE-EE(3) certificate usage, and the internal check will be
       suppressed as appropriate when DANE verification is enabled.

       When the subject CommonName will not be ignored, whether as a result of the
       X509_CHECK_FLAG_ALWAYS_CHECK_SUBJECT host flag, or because no DNS subject alternative
       names are present in the certificate, any DNS name constraints in issuer certificates
       apply to the subject CommonName as well as the subject alternative name extension.

       When the subject CommonName will be ignored, whether as a result of the
       X509_CHECK_FLAG_NEVER_CHECK_SUBJECT host flag, or because some DNS subject alternative
       names are present in the certificate, DNS name constraints in issuer certificates will not
       be applied to the subject DN.  As described in X509_check_host(3) the
       X509_CHECK_FLAG_NEVER_CHECK_SUBJECT flag takes precedence over the
       X509_CHECK_FLAG_ALWAYS_CHECK_SUBJECT flag.

       X509_VERIFY_PARAM_get_hostflags() returns any host flags previously set via a call to
       X509_VERIFY_PARAM_set_hostflags().

       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(3).

       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.

RETURN VALUES

       X509_VERIFY_PARAM_set_flags(), X509_VERIFY_PARAM_clear_flags(),
       X509_VERIFY_PARAM_set_inh_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_get_hostflags() returns any current host flags.

       X509_VERIFY_PARAM_get_inh_flags() returns the current inheritance 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.

VERIFICATION FLAGS

       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.

       When X509_V_FLAG_TRUSTED_FIRST is set, construction of the certificate chain in
       X509_verify_cert(3) will search the trust store for issuer certificates before searching
       the provided untrusted certificates.  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 x509(1)).  As of OpenSSL 1.1.0 this option is on by
       default.

       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_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 1.1.0 and later and
       <X509_V_FLAG_PARTIAL_CHAIN> set, chain construction stops as soon as the first certificate
       from the trust store is added to the chain, whether that certificate is a self-signed
       "root" certificate or a not self-signed intermediate certificate.  Thus, when an
       intermediate certificate is found in the trust store, the verified chain passed to
       callbacks may be shorter than it otherwise would be without the X509_V_FLAG_PARTIAL_CHAIN
       flag.

       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.

INHERITANCE FLAGS

       These flags specify how parameters are "inherited" from one structure to another.

       If X509_VP_FLAG_ONCE is set then the current setting is zeroed after the next call.

       If X509_VP_FLAG_LOCKED is set then no values are copied.  This overrides all of the
       following flags.

       If X509_VP_FLAG_DEFAULT is set then anything set in the source is copied to the
       destination. Effectively the values in "to" become default values which will be used only
       if nothing new is set in "from".  This is the default.

       If X509_VP_FLAG_OVERWRITE is set then all value are copied across whether they are set or
       not. Flags is still Ored though.

       If X509_VP_FLAG_RESET_FLAGS is set then the flags value is copied instead of ORed.

NOTES

       The above functions should be used to manipulate verification parameters instead of
       functions which work in specific structures such as X509_STORE_CTX_set_flags() which are
       likely to be deprecated in a future release.

BUGS

       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.

EXAMPLE

       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_PARAM_free(param);

SEE ALSO

       X509_verify_cert(3), X509_check_host(3), X509_check_email(3), X509_check_ip(3), x509(1)

HISTORY

       The X509_V_FLAG_NO_ALT_CHAINS flag was added in OpenSSL 1.1.0.  The flag
       X509_V_FLAG_CB_ISSUER_CHECK was deprecated in OpenSSL 1.1.0 and has no effect.

       The X509_VERIFY_PARAM_get_hostflags() function was added in OpenSSL 1.1.0i.

COPYRIGHT

       Copyright 2009-2018 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>.