Ubuntu Manpage: X509_STORE_CTX_new_ex, X509_STORE_CTX_new, X509_STORE_CTX_cleanup, X509_STORE_CTX

Provided by: libssl-doc_3.0.5-2ubuntu1_all

NAME

       X509_STORE_CTX_new_ex, X509_STORE_CTX_new, X509_STORE_CTX_cleanup, X509_STORE_CTX_free,
       X509_STORE_CTX_init, X509_STORE_CTX_set0_trusted_stack, X509_STORE_CTX_set_cert,
       X509_STORE_CTX_set0_crls, X509_STORE_CTX_get0_param, X509_STORE_CTX_set0_param,
       X509_STORE_CTX_get0_untrusted, X509_STORE_CTX_set0_untrusted,
       X509_STORE_CTX_get_num_untrusted, X509_STORE_CTX_get0_chain,
       X509_STORE_CTX_set0_verified_chain, X509_STORE_CTX_set_default, X509_STORE_CTX_set_verify,
       X509_STORE_CTX_verify_fn, X509_STORE_CTX_set_purpose, X509_STORE_CTX_set_trust,
       X509_STORE_CTX_purpose_inherit - X509_STORE_CTX initialisation

SYNOPSIS

        #include <openssl/x509_vfy.h>

        X509_STORE_CTX *X509_STORE_CTX_new_ex(OSSL_LIB_CTX *libctx, const char *propq);
        X509_STORE_CTX *X509_STORE_CTX_new(void);
        void X509_STORE_CTX_cleanup(X509_STORE_CTX *ctx);
        void X509_STORE_CTX_free(X509_STORE_CTX *ctx);

        int X509_STORE_CTX_init(X509_STORE_CTX *ctx, X509_STORE *trust_store,
                                X509 *target, STACK_OF(X509) *untrusted);

        void X509_STORE_CTX_set0_trusted_stack(X509_STORE_CTX *ctx, STACK_OF(X509) *sk);

        void X509_STORE_CTX_set_cert(X509_STORE_CTX *ctx, X509 *target);
        void X509_STORE_CTX_set0_crls(X509_STORE_CTX *ctx, STACK_OF(X509_CRL) *sk);

        X509_VERIFY_PARAM *X509_STORE_CTX_get0_param(const X509_STORE_CTX *ctx);
        void X509_STORE_CTX_set0_param(X509_STORE_CTX *ctx, X509_VERIFY_PARAM *param);

        STACK_OF(X509)* X509_STORE_CTX_get0_untrusted(const X509_STORE_CTX *ctx);
        void X509_STORE_CTX_set0_untrusted(X509_STORE_CTX *ctx, STACK_OF(X509) *sk);

        int X509_STORE_CTX_get_num_untrusted(const X509_STORE_CTX *ctx);
        STACK_OF(X509) *X509_STORE_CTX_get0_chain(const X509_STORE_CTX *ctx);
        void X509_STORE_CTX_set0_verified_chain(X509_STORE_CTX *ctx, STACK_OF(X509) *chain);

        int X509_STORE_CTX_set_default(X509_STORE_CTX *ctx, const char *name);
        typedef int (*X509_STORE_CTX_verify_fn)(X509_STORE_CTX *);
        void X509_STORE_CTX_set_verify(X509_STORE_CTX *ctx, X509_STORE_CTX_verify_fn verify);

        int X509_STORE_CTX_set_purpose(X509_STORE_CTX *ctx, int purpose);
        int X509_STORE_CTX_set_trust(X509_STORE_CTX *ctx, int trust);
        int X509_STORE_CTX_purpose_inherit(X509_STORE_CTX *ctx, int def_purpose,
                                           int purpose, int trust);

DESCRIPTION

These functions initialise an X509_STORE_CTX structure for subsequent use by
X509_verify_cert(3) or X509_STORE_CTX_verify(3).

X509_STORE_CTX_new_ex() returns a newly initialised X509_STORE_CTX structure associated
with the specified library context libctx and property query string propq. Any
cryptographic algorithms fetched while performing processing with the X509_STORE_CTX will
use that library context and property query string.

X509_STORE_CTX_new() is the same as X509_STORE_CTX_new_ex() except that the default
library context and a NULL property query string are used.

X509_STORE_CTX_cleanup() internally cleans up an X509_STORE_CTX structure. It is used by
X509_STORE_CTX_init() and X509_STORE_CTX_free().

X509_STORE_CTX_free() completely frees up ctx. After this call ctx is no longer valid. If
ctx is NULL nothing is done.

It must be called before each call to X509_verify_cert(3) or X509_STORE_CTX_verify(3),
i.e., a context is only good for one verification. If you want to verify a further
certificate or chain with the same ctx then you must call X509_STORE_CTX_init() again.
The trusted certificate store is set to trust_store of type X509_STORE. This may be NULL
because there are no trusted certificates or because they are provided simply as a list
using X509_STORE_CTX_set0_trusted_stack(). The certificate to be verified is set to
target, and a list of additional certificates may be provided in untrusted, which will be
untrusted but may be used to build the chain. Each of the trust_store, target and
untrusted parameters can be NULL. Yet note that X509_verify_cert(3) and
X509_STORE_CTX_verify(3) will need a verification target. This can also be set using
X509_STORE_CTX_set_cert(). For X509_STORE_CTX_verify(3), which takes by default the first
element of the list of untrusted certificates as its verification target, this can be also
set indirectly using X509_STORE_CTX_set0_untrusted().

X509_STORE_CTX_set0_trusted_stack() sets the set of trusted certificates of ctx to sk.
This is an alternative way of specifying trusted certificates instead of using an
X509_STORE where its complexity is not needed or to make sure that only the given set sk
of certificates are trusted.

X509_STORE_CTX_set_cert() sets the target certificate to be verified in ctx to target.

X509_STORE_CTX_set0_verified_chain() sets the validated chain to chain. Ownership of the
chain is transferred to ctx, and so it should not be free'd by the caller.

X509_STORE_CTX_get0_chain() returns the internal pointer used by the ctx that contains the
constructed (output) chain.

X509_STORE_CTX_set0_crls() sets a set of CRLs to use to aid certificate verification to
sk. These CRLs will only be used if CRL verification is enabled in the associated
X509_VERIFY_PARAM structure. This might be used where additional "useful" CRLs are
supplied as part of a protocol, for example in a PKCS#7 structure.

X509_STORE_CTX_get0_param() retrieves an internal pointer to the verification parameters
associated with ctx.

X509_STORE_CTX_set0_param() sets the internal verification parameter pointer to param.
After this call param should not be used.

X509_STORE_CTX_get0_untrusted() retrieves an internal pointer to the stack of untrusted
certificates associated with ctx.

X509_STORE_CTX_set0_untrusted() sets the internal pointer to the stack of untrusted
certificates associated with ctx to sk. X509_STORE_CTX_verify() will take the first
element, if any, as its default target if the target certificate is not set explicitly.

X509_STORE_CTX_get_num_untrusted() returns the number of untrusted certificates that were
used in building the chain. This is can be used after calling X509_verify_cert(3) and
similar functions. With X509_STORE_CTX_verify(3), this does not count the first chain
element.

X509_STORE_CTX_get0_chain() returns the internal pointer used by the ctx that contains the
validated chain.

Details of the chain building and checking process are described in "Certification Path
Building" in openssl-verification-options(1) and "Certification Path Validation" in
openssl-verification-options(1).

X509_STORE_CTX_set0_verified_chain() sets the validated chain used by ctx to be chain.
Ownership of the chain is transferred to ctx, and so it should not be free'd by the
caller.

X509_STORE_CTX_set_default() looks up and sets the default verification method to name.
This uses the function X509_VERIFY_PARAM_lookup() to find an appropriate set of parameters
from the purpose identifier name. Currently defined purposes are "sslclient",
"sslserver", "nssslserver", "smimesign", "smimeencrypt", "crlsign", "ocsphelper",
"timestampsign", and "any".

X509_STORE_CTX_set_verify() provides the capability for overriding the default verify
function. This function is responsible for verifying chain signatures and expiration
times.

A verify function is defined as an X509_STORE_CTX_verify type which has the following
signature:

int (*verify)(X509_STORE_CTX *);

This function should receive the current X509_STORE_CTX as a parameter and return 1 on
success or 0 on failure.

X509 certificates may contain information about what purposes keys contained within them
can be used for. For example "TLS WWW Server Authentication" or "Email Protection". This
"key usage" information is held internally to the certificate itself. In addition the
trust store containing trusted certificates can declare what purposes we trust different
certificates for. This "trust" information is not held within the certificate itself but
is "meta" information held alongside it. This "meta" information is associated with the
certificate after it is issued and could be determined by a system administrator. For
example a certificate might declare that it is suitable for use for both "TLS WWW Server
Authentication" and "TLS Client Authentication", but a system administrator might only
trust it for the former. An X.509 certificate extension exists that can record extended
key usage information to supplement the purpose information described above. This extended
mechanism is arbitrarily extensible and not well suited for a generic library API;
applications that need to validate extended key usage information in certifiates will need
to define a custom "purpose" (see below) or supply a nondefault verification callback
(X509_STORE_set_verify_cb_func(3)).

X509_STORE_CTX_set_purpose() sets the purpose for the target certificate being verified in
the ctx. Built-in available values for the purpose argument are X509_PURPOSE_SSL_CLIENT,
X509_PURPOSE_SSL_SERVER, X509_PURPOSE_NS_SSL_SERVER, X509_PURPOSE_SMIME_SIGN,
X509_PURPOSE_SMIME_ENCRYPT, X509_PURPOSE_CRL_SIGN, X509_PURPOSE_ANY,
X509_PURPOSE_OCSP_HELPER and X509_PURPOSE_TIMESTAMP_SIGN. It is also possible to create a
custom purpose value. Setting a purpose will ensure that the key usage declared within
certificates in the chain being verified is consistent with that purpose as well as,
potentially, other checks. Every purpose also has an associated default trust value which
will also be set at the same time. During verification this trust setting will be verified
to check it is consistent with the trust set by the system administrator for certificates
in the chain.

X509_STORE_CTX_set_trust() sets the trust value for the target certificate being verified
in the ctx. Built-in available values for the trust argument are X509_TRUST_COMPAT,
X509_TRUST_SSL_CLIENT, X509_TRUST_SSL_SERVER, X509_TRUST_EMAIL, X509_TRUST_OBJECT_SIGN,
X509_TRUST_OCSP_SIGN, X509_TRUST_OCSP_REQUEST and X509_TRUST_TSA. It is also possible to
create a custom trust value. Since X509_STORE_CTX_set_purpose() also sets the trust value
it is normally sufficient to only call that function. If both are called then
X509_STORE_CTX_set_trust() should be called after X509_STORE_CTX_set_purpose() since the
trust setting of the last call will be used.

It should not normally be necessary for end user applications to call
X509_STORE_CTX_purpose_inherit() directly. Typically applications should call
X509_STORE_CTX_set_purpose() or X509_STORE_CTX_set_trust() instead. Using this function it
is possible to set the purpose and trust values for the ctx at the same time. Both ctx
and its internal verification parameter pointer must not be NULL. The def_purpose and
purpose arguments can have the same purpose values as described for
X509_STORE_CTX_set_purpose() above. The trust argument can have the same trust values as
described in X509_STORE_CTX_set_trust() above. Any of the def_purpose, purpose or trust
values may also have the value 0 to indicate that the supplied parameter should be
ignored. After calling this function the purpose to be used for verification is set from
the purpose argument unless the purpose was already set in ctx before, and the trust is
set from the trust argument unless the trust was already set in ctx before. If trust is 0
then the trust value will be set from the default trust value for purpose. If the default
trust value for the purpose is X509_TRUST_DEFAULT and trust is 0 then the default trust
value associated with the def_purpose value is used for the trust setting instead.

NOTES

       The certificates and CRLs in a store are used internally and should not be freed up until
       after the associated X509_STORE_CTX is freed.

BUGS

       The certificates and CRLs in a context are used internally and should not be freed up
       until after the associated X509_STORE_CTX is freed. Copies should be made or reference
       counts increased instead.

RETURN VALUES

       X509_STORE_CTX_new() returns a newly allocated context or NULL if an error occurred.

       X509_STORE_CTX_init() returns 1 for success or 0 if an error occurred.

       X509_STORE_CTX_get0_param() returns a pointer to an X509_VERIFY_PARAM structure or NULL if
       an error occurred.

       X509_STORE_CTX_cleanup(), X509_STORE_CTX_free(), X509_STORE_CTX_set0_trusted_stack(),
       X509_STORE_CTX_set_cert(), X509_STORE_CTX_set0_crls() and X509_STORE_CTX_set0_param() do
       not return values.

       X509_STORE_CTX_set_default() returns 1 for success or 0 if an error occurred.

       X509_STORE_CTX_get_num_untrusted() returns the number of untrusted certificates used.

HISTORY

       The X509_STORE_CTX_set0_crls() function was added in OpenSSL 1.0.0.  The
       X509_STORE_CTX_get_num_untrusted() function was added in OpenSSL 1.1.0.  The
       X509_STORE_CTX_new_ex() function was added in OpenSSL 3.0.

       There is no need to call X509_STORE_CTX_cleanup() explicitly since OpenSSL 3.0.

COPYRIGHT

       Copyright 2009-2022 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>.