X509_VERIFY_PARAM_SET_FLAGS(3)

NAME
X509_VERIFY_PARAM_new, X509_VERIFY_PARAM_free, X509_VERIFY_PARAM_get0_name, X509_VERIFY_PARAM_set1_name, 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_time, X509_VERIFY_PARAM_add0_policy, X509_VERIFY_PARAM_set1_policies, X509_VERIFY_PARAM_set_depth, X509_VERIFY_PARAM_get_depth, 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_VERIFY_PARAM_add0_table, X509_VERIFY_PARAM_lookup, X509_VERIFY_PARAM_get_count, X509_VERIFY_PARAM_get0, X509_VERIFY_PARAM_table_cleanup - X509 verification parameters

SYNOPSIS
#include <openssl/x509_vfy.h>
X509_VERIFY_PARAM *
X509_VERIFY_PARAM_new(void);
void
X509_VERIFY_PARAM_free(X509_VERIFY_PARAM *param);
const char *
X509_VERIFY_PARAM_get0_name(const X509_VERIFY_PARAM *param);
int
X509_VERIFY_PARAM_set1_name(X509_VERIFY_PARAM *param, const char *name);
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);
int
X509_VERIFY_PARAM_add0_table(X509_VERIFY_PARAM *param);
const X509_VERIFY_PARAM *
X509_VERIFY_PARAM_lookup(const char *name);
int
X509_VERIFY_PARAM_get_count(void);
const X509_VERIFY_PARAM *
X509_VERIFY_PARAM_get0(int id);
void
X509_VERIFY_PARAM_table_cleanup(void);

DESCRIPTION
These functions manipulate an X509_VERIFY_PARAM object associated with a certificate verification operation.

X509_VERIFY_PARAM_new() allocates and initializes an empty X509_VERIFY_PARAM object.

X509_VERIFY_PARAM_free() clears all data contained in param and releases all memory used by it. If param is a NULL pointer, no action occurs.

X509_VERIFY_PARAM_get0_name() returns the name of the given param object, usually describing its purpose, for example "default", "pkcs7", "smime_sign", "ssl_client", or "ssl_server". For user-defined objects, the returned pointer may be NULL even if the object is otherwise valid.

X509_VERIFY_PARAM_set1_name() sets the name of param to a copy of name, or to NULL if name is NULL.

X509_VERIFY_PARAM_set_flags() sets the flags in param by OR'ing 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 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 hostname or names. If name is NULL or empty, the list of hostnames is cleared, and name checks are not performed on the peer certificate. namelen should be set to the length of name. For historical compatibility, if name is NUL-terminated, namelen may be specified as zero. 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). X509_VERIFY_PARAM_set1_host() will fail if name contains any embedded 0 bytes.

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() and X509_VERIFY_PARAM_add1_host() are retained. No change is made if name is NULL or empty. namelen should be set to the length of name. For historical compatibility, if name is NUL-terminated, namelen may be specified as zero. X509_VERIFY_PARAM_add1_host() will fail if name contains any embedded 0 bytes. 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.

X509_VERIFY_PARAM_set1_email() sets the expected RFC822 email address to email. emaillen should be set to the length of email. For historical compatibility, if email is NUL-terminated, emaillen may be specified as zero, X509_VERIFY_PARAM_set1_email() will fail if email is NULL, an empty string, or contains embedded 0 bytes. 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. X509_VERIFY_PARAM_set1_ip() will fail if ip is NULL or if iplen is not 4 or 16. 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_ip_asc() will fail if ipasc is unparsable.

X509_VERIFY_PARAM_add0_table() adds param to a static list of X509_VERIFY_PARAM objects maintained by the library. This function is extremely dangerous because contrary to the name of the function, if the list already contains an object that happens to have the same name, that old object is not only silently removed from the list, but also silently freed, which may silently invalidate various pointers existing elsewhere in the program.

X509_VERIFY_PARAM_lookup() searches this list for an object of the given name. If no match is found, the predefined objects built-in to the library are also inspected.

X509_VERIFY_PARAM_get_count() returns the sum of the number of objects on this list and the number of predefined objects built-in to the library. Note that this is not necessarily the total number of X509_VERIFY_PARAM objects existing in the program because there may be additional such objects that were never added to the list.

X509_VERIFY_PARAM_get0() accesses predefined and user-defined objects using id as an index, useful for looping over objects without knowing their names. An argument less than the number of predefined objects selects one of the predefined objects; a higher argument selects an object from the list.

X509_VERIFY_PARAM_table_cleanup() deletes all objects from this list. It is extremely dangerous because it also invalidates all data that was contained in all objects that were on the list and because it frees all these objects, which may invalidate various pointers existing elsewhere in the program.

RETURN VALUES
X509_VERIFY_PARAM_new() returns a pointer to the new object, or NULL on allocation failure.

X509_VERIFY_PARAM_set1_name(), 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(), and X509_VERIFY_PARAM_add0_table() return 1 for success or 0 for failure.

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 or 0 for failure. A failure from these routines will poison the X509_VERIFY_PARAM object so that future calls to X509_verify_cert(3) using the poisoned object will fail.

X509_VERIFY_PARAM_get_flags() returns the current verification flags.

X509_VERIFY_PARAM_get_depth() returns the current verification depth.

X509_VERIFY_PARAM_get0_name() and X509_VERIFY_PARAM_get0_peername() return pointers to strings that are only valid during the lifetime of the given param object and that must not be freed by the application program.

X509_VERIFY_PARAM_lookup() and X509_VERIFY_PARAM_get0() return a pointer to an existing built-in or user-defined object, or NULL if no object with the given name is found, or if id is at least X509_VERIFY_PARAM_get_count().

X509_VERIFY_PARAM_get_count() returns a number of objects.

VERIFICATION FLAGS
The verification flags consists of zero or more of the following flags OR'ed 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 disables 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 RFC 3280. 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.

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.

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 the trust settings options of the x509 command in openssl(1).

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.

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.

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.

EXAMPLES
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
SSL_set1_host(3), SSL_set1_param(3), X509_check_host(3), X509_STORE_CTX_set0_param(3), X509_STORE_set1_param(3), X509_verify_cert(3)

HISTORY
X509_VERIFY_PARAM_new(), X509_VERIFY_PARAM_free(), X509_VERIFY_PARAM_set1_name(), X509_VERIFY_PARAM_set_flags(), X509_VERIFY_PARAM_set_purpose(), X509_VERIFY_PARAM_set_trust(), X509_VERIFY_PARAM_set_time(), X509_VERIFY_PARAM_add0_policy(), X509_VERIFY_PARAM_set1_policies(), X509_VERIFY_PARAM_set_depth(), X509_VERIFY_PARAM_get_depth(), X509_VERIFY_PARAM_add0_table(), X509_VERIFY_PARAM_lookup(), and X509_VERIFY_PARAM_table_cleanup() first appeared in OpenSSL 0.9.8. X509_VERIFY_PARAM_clear_flags() and X509_VERIFY_PARAM_get_flags() first appeared in OpenSSL 0.9.8a. All these functions have been available since OpenBSD 4.5.

X509_VERIFY_PARAM_get0_name() 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_VERIFY_PARAM_get_count(), and X509_VERIFY_PARAM_get0() first appeared in OpenSSL 1.0.2 and have been available since OpenBSD 6.3.

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 enabled, 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.