Provided by: libssl-doc_3.0.13-0ubuntu3.5_all 
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_get0_host, 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_get0_email, X509_VERIFY_PARAM_set1_email, X509_VERIFY_PARAM_set1_ip,
X509_VERIFY_PARAM_get1_ip_asc, 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(const 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);
char *X509_VERIFY_PARAM_get0_host(X509_VERIFY_PARAM *param, int n);
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(const X509_VERIFY_PARAM *param);
char *X509_VERIFY_PARAM_get0_email(X509_VERIFY_PARAM *param);
int X509_VERIFY_PARAM_set1_email(X509_VERIFY_PARAM *param,
const char *email, size_t emaillen);
char *X509_VERIFY_PARAM_get1_ip_asc(X509_VERIFY_PARAM *param);
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
"VERIFICATION FLAGS" 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 X509_PURPOSE_SSL_CLIENT. The purpose
requirement is cleared if purpose is 0.
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() adds policy to the acceptable policy set. Contrary to preexisting
documentation of this function it does not enable policy checking.
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_get0_host() returns the nth expected DNS hostname that has been set using
X509_VERIFY_PARAM_set1_host() or X509_VERIFY_PARAM_add1_host(). To obtain all names start with n = 0 and
increment n as long as no NULL pointer is returned.
X509_VERIFY_PARAM_set1_host() sets the expected DNS hostname to name clearing any previously specified
hostname. 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_get0_email() returns the expected RFC822 email address.
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_get1_ip_asc() returns the expected IP address as a string. The caller is responsible
for freeing it.
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_get0_host(), X509_VERIFY_PARAM_get0_email(), and X509_VERIFY_PARAM_get1_ip_asc(),
return the string pointer specified above or NULL if the respective value has not been set or on error.
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 disables critical extension checking. By default any unhandled critical
extensions in certificates or (if checked) CRLs result 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 requests checking the signature of the last certificate in a chain if the
certificate is supposedly self-signed. This is prohibited and will result in an error if it is a non-
conforming CA certificate with key usage restrictions not including the keyCertSign bit. 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 self-signature of such a
certificate is that disabled or unsupported message digests used for the signature are not treated as
fatal errors.
When X509_V_FLAG_TRUSTED_FIRST is set, which is always the case since OpenSSL 1.1.0, construction of the
certificate chain in X509_verify_cert(3) searches 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
openssl-x509(1)).
The X509_V_FLAG_NO_ALT_CHAINS flag could have been used before OpenSSL 1.1.0 to suppress 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 non-self-signed certificates in the trust store to be treated
as trust anchors, in the same way as self-signed root CA certificates. This makes it possible to trust
self-issued certificates as well as certificates issued by an intermediate CA without having to trust
their 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 contained in the trust store is added to the chain,
whether that certificate is a self-signed "root" certificate or a not self-signed "intermediate" or self-
issued 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.
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
X509_verify_cert(3), X509_check_host(3), X509_check_email(3), X509_check_ip(3), openssl-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.
The X509_VERIFY_PARAM_get0_host(), X509_VERIFY_PARAM_get0_email(), and X509_VERIFY_PARAM_get1_ip_asc()
functions were added in OpenSSL 3.0.
The function X509_VERIFY_PARAM_add0_policy() was historically documented as enabling policy checking
however the implementation has never done this. The documentation was changed to align with the
implementation.
COPYRIGHT
Copyright 2009-2023 The OpenSSL Project Authors. All Rights Reserved.
Licensed under the Apache License 2.0 (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>.