=pod

=head1 NAME

X509_LOOKUP, X509_LOOKUP_TYPE,
X509_LOOKUP_new, X509_LOOKUP_free, X509_LOOKUP_init,
X509_LOOKUP_shutdown,
X509_LOOKUP_set_method_data, X509_LOOKUP_get_method_data,
X509_LOOKUP_ctrl_ex, X509_LOOKUP_ctrl,
X509_LOOKUP_load_file_ex, X509_LOOKUP_load_file,
X509_LOOKUP_add_dir,
X509_LOOKUP_add_store_ex, X509_LOOKUP_add_store,
X509_LOOKUP_load_store_ex, X509_LOOKUP_load_store,
X509_LOOKUP_get_store,
X509_LOOKUP_by_subject_ex, X509_LOOKUP_by_subject,
X509_LOOKUP_by_issuer_serial, X509_LOOKUP_by_fingerprint,
X509_LOOKUP_by_alias
- OpenSSL certificate lookup mechanisms

=head1 SYNOPSIS

 #include <openssl/x509_vfy.h>

 typedef x509_lookup_st X509_LOOKUP;

 typedef enum X509_LOOKUP_TYPE;

 X509_LOOKUP *X509_LOOKUP_new(X509_LOOKUP_METHOD *method);
 int X509_LOOKUP_init(X509_LOOKUP *ctx);
 int X509_LOOKUP_shutdown(X509_LOOKUP *ctx);
 void X509_LOOKUP_free(X509_LOOKUP *ctx);

 int X509_LOOKUP_set_method_data(X509_LOOKUP *ctx, void *data);
 void *X509_LOOKUP_get_method_data(const X509_LOOKUP *ctx);

 int X509_LOOKUP_ctrl_ex(X509_LOOKUP *ctx, int cmd, const char *argc, long argl,
                         char **ret, OSSL_LIB_CTX *libctx, const char *propq);
 int X509_LOOKUP_ctrl(X509_LOOKUP *ctx, int cmd, const char *argc,
                      long argl, char **ret);
 int X509_LOOKUP_load_file_ex(X509_LOOKUP *ctx, char *name, long type,
                              OSSL_LIB_CTX *libctx, const char *propq);
 int X509_LOOKUP_load_file(X509_LOOKUP *ctx, char *name, long type);
 int X509_LOOKUP_load_file_ex(X509_LOOKUP *ctx, char *name, long type,
                              OSSL_LIB_CTX *libctx, const char *propq);
 int X509_LOOKUP_add_dir(X509_LOOKUP *ctx, char *name, long type);
 int X509_LOOKUP_add_store_ex(X509_LOOKUP *ctx, char *uri, OSSL_LIB_CTX *libctx,
                              const char *propq);
 int X509_LOOKUP_add_store(X509_LOOKUP *ctx, char *uri);
 int X509_LOOKUP_load_store_ex(X509_LOOKUP *ctx, char *uri, OSSL_LIB_CTX *libctx,
                               const char *propq);
 int X509_LOOKUP_load_store(X509_LOOKUP *ctx, char *uri);

 X509_STORE *X509_LOOKUP_get_store(const X509_LOOKUP *ctx);

 int X509_LOOKUP_by_subject_ex(X509_LOOKUP *ctx, X509_LOOKUP_TYPE type,
                               const X509_NAME *name, X509_OBJECT *ret,
                               OSSL_LIB_CTX *libctx, const char *propq);
 int X509_LOOKUP_by_subject(X509_LOOKUP *ctx, X509_LOOKUP_TYPE type,
                            const X509_NAME *name, X509_OBJECT *ret);
 int X509_LOOKUP_by_issuer_serial(X509_LOOKUP *ctx, X509_LOOKUP_TYPE type,
                                  const X509_NAME *name,
                                  const ASN1_INTEGER *serial, X509_OBJECT *ret);
 int X509_LOOKUP_by_fingerprint(X509_LOOKUP *ctx, X509_LOOKUP_TYPE type,
                                const unsigned char *bytes, int len,
                                X509_OBJECT *ret);
 int X509_LOOKUP_by_alias(X509_LOOKUP *ctx, X509_LOOKUP_TYPE type,
                          const char *str, int len, X509_OBJECT *ret);

=head1 DESCRIPTION

The B<X509_LOOKUP> structure holds the information needed to look up
certificates and CRLs according to an associated L<X509_LOOKUP_METHOD(3)>.
Multiple B<X509_LOOKUP> instances can be added to an L<X509_STORE(3)>
to enable lookup in that store.

X509_LOOKUP_new() creates a new B<X509_LOOKUP> using the given lookup
I<method>.
It can also be created by calling L<X509_STORE_add_lookup(3)>, which
will associate a B<X509_STORE> with the lookup mechanism.

X509_LOOKUP_init() initializes the internal state and resources as
needed by the given B<X509_LOOKUP> to do its work.

X509_LOOKUP_shutdown() tears down the internal state and resources of
the given B<X509_LOOKUP>.

X509_LOOKUP_free() destructs the given B<X509_LOOKUP>.
If the argument is NULL, nothing is done.

X509_LOOKUP_set_method_data() and X509_LOOKUP_get_method_data()
associates and retrieves a pointer to application data to and from the
given B<X509_LOOKUP>, respectively.

X509_LOOKUP_ctrl_ex() is used to set or get additional data to or from
a B<X509_LOOKUP> structure using any control function in the
associated L<X509_LOOKUP_METHOD(3)>.
The arguments of the control command are passed via I<argc> and I<argl>,
its return value via I<*ret>. The library context I<libctx> and property
query I<propq> are used when fetching algorithms from providers.
The meaning of the arguments depends on the I<cmd> number of the
control command. In general, this function is not called directly, but
wrapped by a macro call, see below.
The control I<cmd>s known to OpenSSL are discussed in more depth
in L</Control Commands>.

X509_LOOKUP_ctrl() is similar to X509_LOOKUP_ctrl_ex() but
uses NULL for the library context I<libctx> and property query I<propq>.

X509_LOOKUP_load_file_ex() passes a filename to be loaded immediately
into the associated B<X509_STORE>. The library context I<libctx> and property
query I<propq> are used when fetching algorithms from providers.
I<type> indicates what type of object is expected.
This can only be used with a lookup using the implementation
L<X509_LOOKUP_file(3)>.

X509_LOOKUP_load_file() is similar to X509_LOOKUP_load_file_ex() but
uses NULL for the library context I<libctx> and property query I<propq>.

X509_LOOKUP_add_dir() passes a directory specification from which
certificates and CRLs are loaded on demand into the associated
B<X509_STORE>.
I<type> indicates what type of object is expected.
This can only be used with a lookup using the implementation
L<X509_LOOKUP_hash_dir(3)>.

X509_LOOKUP_add_store_ex() passes a URI for a directory-like structure
from which containers with certificates and CRLs are loaded on demand
into the associated B<X509_STORE>. The library context I<libctx> and property
query I<propq> are used when fetching algorithms from providers.

X509_LOOKUP_add_store() is similar to X509_LOOKUP_add_store_ex() but
uses NULL for the library context I<libctx> and property query I<propq>.

X509_LOOKUP_load_store_ex() passes a URI for a single container from
which certificates and CRLs are immediately loaded into the associated
B<X509_STORE>. The library context I<libctx> and property query I<propq> are used
when fetching algorithms from providers.
These functions can only be used with a lookup using the
implementation L<X509_LOOKUP_store(3)>.

X509_LOOKUP_load_store() is similar to X509_LOOKUP_load_store_ex() but
uses NULL for the library context I<libctx> and property query I<propq>.

X509_LOOKUP_load_file_ex(), X509_LOOKUP_load_file(),
X509_LOOKUP_add_dir(),
X509_LOOKUP_add_store_ex() X509_LOOKUP_add_store(),
X509_LOOKUP_load_store_ex() and X509_LOOKUP_load_store() are
implemented as macros that use X509_LOOKUP_ctrl().

X509_LOOKUP_by_subject_ex(), X509_LOOKUP_by_subject(),
X509_LOOKUP_by_issuer_serial(), X509_LOOKUP_by_fingerprint(), and
X509_LOOKUP_by_alias() look up certificates and CRLs in the L<X509_STORE(3)>
associated with the B<X509_LOOKUP> using different criteria, where the looked up
object is stored in I<ret>.
Some of the underlying B<X509_LOOKUP_METHOD>s will also cache objects
matching the criteria in the associated B<X509_STORE>, which makes it
possible to handle cases where the criteria have more than one hit.

=head2 Control Commands

The B<X509_LOOKUP_METHOD>s built into OpenSSL recognize the following
X509_LOOKUP_ctrl() I<cmd>s:

=over 4

=item B<X509_L_FILE_LOAD>

This is the command that X509_LOOKUP_load_file_ex() and
X509_LOOKUP_load_file() use.
The filename is passed in I<argc>, and the type in I<argl>.

=item B<X509_L_ADD_DIR>

This is the command that X509_LOOKUP_add_dir() uses.
The directory specification is passed in I<argc>, and the type in
I<argl>.

=item B<X509_L_ADD_STORE>

This is the command that X509_LOOKUP_add_store_ex() and
X509_LOOKUP_add_store() use.
The URI is passed in I<argc>.

=item B<X509_L_LOAD_STORE>

This is the command that X509_LOOKUP_load_store_ex() and
X509_LOOKUP_load_store() use.
The URI is passed in I<argc>.

=back

=head1 RETURN VALUES

X509_LOOKUP_new() returns a B<X509_LOOKUP> pointer when successful,
or NULL on error.

X509_LOOKUP_init() and X509_LOOKUP_shutdown() return 1 on success, or
0 on error.

X509_LOOKUP_ctrl_ex() and X509_LOOKUP_ctrl()
return -1 if the B<X509_LOOKUP> doesn't have an
associated B<X509_LOOKUP_METHOD>, or 1 if the X<509_LOOKUP_METHOD>
doesn't have a control function.
Otherwise, it returns what the control function in the
B<X509_LOOKUP_METHOD> returns, which is usually 1 on success and 0 on error
but could also be -1 on failure.

X509_LOOKUP_get_store() returns a B<X509_STORE> pointer if there is
one, otherwise NULL.

X509_LOOKUP_by_subject_ex() returns 0 if there is no B<X509_LOOKUP_METHOD>
that implements any of the get_by_subject_ex() or get_by_subject() functions.
It calls get_by_subject_ex() if present, otherwise get_by_subject(), and returns
the result of the function, which is usually 1 on success and 0 on error.

X509_LOOKUP_by_subject() is similar to X509_LOOKUP_by_subject_ex()
but passes NULL for both the libctx and propq.

X509_LOOKUP_by_issuer_serial(), X509_LOOKUP_by_fingerprint(), and
X509_LOOKUP_by_alias() all return 0 if there is no B<X509_LOOKUP_METHOD> or that
method doesn't implement the corresponding function.
Otherwise, they return what the corresponding function in the
B<X509_LOOKUP_METHOD> returns, which is usually 1 on success and 0 in
error.

=head1 SEE ALSO

L<X509_LOOKUP_METHOD(3)>, L<X509_STORE(3)>

=head1 HISTORY

The functions X509_LOOKUP_by_subject_ex() and
X509_LOOKUP_ctrl_ex() were added in OpenSSL 3.0.

The macros X509_LOOKUP_load_file_ex(),
X509_LOOKUP_load_store_ex() and X509_LOOKUP_add_store_ex() were
added in OpenSSL 3.0.

=head1 COPYRIGHT

Copyright 2020-2025 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
L<https://www.openssl.org/source/license.html>.

=cut
