DOC: Add documentation related to X509_LOOKUPs

Most of all, the base X509_LOOKUP functionality is now documented.
Furthermore, the names X509_LOOKUP_METHOD and X509_STORE are added for
reference.

Some functions were moved from X509_LOOKUP_meth_new.pod

Reviewed-by: Matt Caswell <matt@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/11120)

3 files changed, 203 insertions, 12 deletions

diff --git a/doc/man3/X509_LOOKUP.pod b/doc/man3/X509_LOOKUP.pod
new file mode 100644
index 0000000000..603b58c73d
--- /dev/null
+++ b/doc/man3/X509_LOOKUP.pod
@@ -0,0 +1,179 @@
+=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,
+X509_LOOKUP_load_file, X509_LOOKUP_add_dir,
+X509_LOOKUP_get_store, 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(X509_LOOKUP *ctx, int cmd, const char *argc,
+                      long argl, char **ret);
+ int X509_LOOKUP_load_file(X509_LOOKUP *ctx, char *name, long type);
+ int X509_LOOKUP_add_dir(X509_LOOKUP *ctx, char *name, long type);
+
+ X509_STORE *X509_LOOKUP_get_store(const X509_LOOKUP *ctx);
+
+ int X509_LOOKUP_by_subject(X509_LOOKUP *ctx, X509_LOOKUP_TYPE type,
+                            X509_NAME *name, X509_OBJECT *ret);
+ int X509_LOOKUP_by_issuer_serial(X509_LOOKUP *ctx, X509_LOOKUP_TYPE type,
+                                  X509_NAME *name, 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>.
+
+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() is used to set or get additional data to or from a
+B<X509_LOOKUP> structure or its 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 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_load_file() passes a filename to be loaded immediately
+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_file(3)>.
+
+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_load_file(), X509_LOOKUP_add_dir(),
+X509_LOOKUP_add_store(), and X509_LOOKUP_load_store() are implemented
+as macros that use X509_LOOKUP_ctrl().
+
+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 recognise 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() uses.
+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() uses.
+The URI is passed in I<argc>.
+
+=item B<X509_L_LOAD_STORE>
+
+This is the command that X509_LOOKUP_load_store() uses.
+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() returns -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 in
+error.
+
+X509_LOOKUP_get_store() returns a B<X509_STORE> pointer if there is
+one, otherwise NULL.
+
+X509_LOOKUP_by_subject(), 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, it returns 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 COPYRIGHT
+
+Copyright 2020 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
diff --git a/doc/man3/X509_LOOKUP_meth_new.pod b/doc/man3/X509_LOOKUP_meth_new.pod
index e5f0a098b3..bd313cfb40 100644
--- a/doc/man3/X509_LOOKUP_meth_new.pod
+++ b/doc/man3/X509_LOOKUP_meth_new.pod
@@ -2,6 +2,7 @@
 
 =head1 NAME
 
+X509_LOOKUP_METHOD,
 X509_LOOKUP_meth_new, X509_LOOKUP_meth_free, X509_LOOKUP_meth_set_new_item,
 X509_LOOKUP_meth_get_new_item, X509_LOOKUP_meth_set_free,
 X509_LOOKUP_meth_get_free, X509_LOOKUP_meth_set_init,
@@ -16,14 +17,15 @@ X509_LOOKUP_get_by_fingerprint_fn, X509_LOOKUP_meth_set_get_by_fingerprint,
 X509_LOOKUP_meth_get_get_by_fingerprint,
 X509_LOOKUP_get_by_alias_fn, X509_LOOKUP_meth_set_get_by_alias,
 X509_LOOKUP_meth_get_get_by_alias,
-X509_LOOKUP_set_method_data, X509_LOOKUP_get_method_data,
-X509_LOOKUP_get_store, X509_OBJECT_set1_X509, X509_OBJECT_set1_X509_CRL
+X509_OBJECT_set1_X509, X509_OBJECT_set1_X509_CRL
 - Routines to build up X509_LOOKUP methods
 
 =head1 SYNOPSIS
 
  #include <openssl/x509_vfy.h>
 
+ typedef x509_lookup_method_st X509_LOOKUP_METHOD;
+
  X509_LOOKUP_METHOD *X509_LOOKUP_meth_new(const char *name);
  void X509_LOOKUP_meth_free(X509_LOOKUP_METHOD *method);
 
@@ -92,11 +94,6 @@ X509_LOOKUP_get_store, X509_OBJECT_set1_X509, X509_OBJECT_set1_X509_CRL
  X509_LOOKUP_get_by_alias_fn X509_LOOKUP_meth_get_get_by_alias(
      const X509_LOOKUP_METHOD *method);
 
- int X509_LOOKUP_set_method_data(X509_LOOKUP *ctx, void *data);
- void *X509_LOOKUP_get_method_data(const X509_LOOKUP *ctx);
-
- X509_STORE *X509_LOOKUP_get_store(const X509_LOOKUP *ctx);
-
  int X509_OBJECT_set1_X509(X509_OBJECT *a, X509 *obj);
  int X509_OBJECT_set1_X509_CRL(X509_OBJECT *a, X509_CRL *obj);
 
@@ -118,7 +115,7 @@ X509_LOOKUP_get_new_item() and X509_LOOKUP_set_new_item() get and set the
 function that is called when an B<X509_LOOKUP> object is created with
 X509_LOOKUP_new(). If an X509_LOOKUP_METHOD requires any per-X509_LOOKUP
 specific data, the supplied new_item function should allocate this data and
-invoke X509_LOOKUP_set_method_data().
+invoke L<X509_LOOKUP_set_method_data(3)>.
 
 X509_LOOKUP_get_free() and X509_LOOKUP_set_free() get and set the function
 that is used to free any method data that was allocated and set from within
@@ -126,7 +123,7 @@ new_item function.
 
 X509_LOOKUP_meth_get_init() and X509_LOOKUP_meth_set_init() get and set the
 function that is used to initialize the method data that was set with
-X509_LOOKUP_set_method_data() as part of the new_item routine.
+L<X509_LOOKUP_set_method_data(3)> as part of the new_item routine.
 
 X509_LOOKUP_meth_get_shutdown() and X509_LOOKUP_meth_set_shutdown() get and set
 the function that is used to shut down the method data whose state was
@@ -164,9 +161,9 @@ increments the result's reference count.
 
 Any method data that was created as a result of the new_item function
 set by X509_LOOKUP_meth_set_new_item() can be accessed with
-X509_LOOKUP_get_method_data(). The B<X509_STORE> object that owns the
-X509_LOOKUP may be accessed with X509_LOOKUP_get_store(). Successful lookups
-should return 1, and unsuccessful lookups should return 0.
+L<X509_LOOKUP_get_method_data(3)>. The B<X509_STORE> object that owns the
+X509_LOOKUP may be accessed with L<X509_LOOKUP_get_store(3)>. Successful
+lookups should return 1, and unsuccessful lookups should return 0.
 
 X509_LOOKUP_get_get_by_subject(), X509_LOOKUP_get_get_by_issuer_serial(),
 X509_LOOKUP_get_get_by_fingerprint(), X509_LOOKUP_get_get_by_alias() retrieve
diff --git a/doc/man3/X509_STORE_add_cert.pod b/doc/man3/X509_STORE_add_cert.pod
index 3ea5b8b127..5ac69d593b 100644
--- a/doc/man3/X509_STORE_add_cert.pod
+++ b/doc/man3/X509_STORE_add_cert.pod
@@ -2,8 +2,10 @@
 
 =head1 NAME
 
+X509_STORE,
 X509_STORE_add_cert, X509_STORE_add_crl, X509_STORE_set_depth,
 X509_STORE_set_flags, X509_STORE_set_purpose, X509_STORE_set_trust,
+X509_STORE_add_lookup,
 X509_STORE_load_locations,
 X509_STORE_set_default_paths
 - X509_STORE manipulation
@@ -12,6 +14,8 @@ X509_STORE_set_default_paths
 
  #include <openssl/x509_vfy.h>
 
+ typedef x509_store_st X509_STORE;
+
  int X509_STORE_add_cert(X509_STORE *ctx, X509 *x);
  int X509_STORE_add_crl(X509_STORE *ctx, X509_CRL *x);
  int X509_STORE_set_depth(X509_STORE *store, int depth);
@@ -19,6 +23,9 @@ X509_STORE_set_default_paths
  int X509_STORE_set_purpose(X509_STORE *ctx, int purpose);
  int X509_STORE_set_trust(X509_STORE *ctx, int trust);
 
+ X509_LOOKUP *X509_STORE_add_lookup(X509_STORE *store,
+                                    X509_LOOKUP_METHOD *meth);
+
  int X509_STORE_load_locations(X509_STORE *ctx,
                                const char *file, const char *dir);
  int X509_STORE_set_default_paths(X509_STORE *ctx);
@@ -65,6 +72,11 @@ for the corresponding values used in certificate chain validation.  Their
 behavior is documented in the corresponding B<X509_VERIFY_PARAM> manual
 pages, e.g., L<X509_VERIFY_PARAM_set_depth(3)>.
 
+X509_STORE_add_lookup() finds or creates a L<X509_LOOKUP(3)> with the
+L<X509_LOOKUP_METHOD(3)> I<meth> and adds it to the B<X509_STORE>
+I<store>.  This also associates the B<X509_STORE> with the lookup, so
+B<X509_LOOKUP> functions can look up objects in that store.
+
 X509_STORE_load_locations() loads trusted certificate(s) into an
 B<X509_STORE> from a given file and/or directory path.  It is permitted
 to specify just a file, just a directory, or both paths.  The certificates
@@ -83,6 +95,9 @@ X509_STORE_set_flags(), X509_STORE_set_purpose(),
 X509_STORE_set_trust(), X509_STORE_load_locations(), and
 X509_STORE_set_default_paths() return 1 on success or 0 on failure.
 
+X509_STORE_add_lookup() returns the found or created
+L<X509_LOOKUP(3)>, or NULL on error.
+
 =head1 SEE ALSO
 
 L<X509_LOOKUP_hash_dir(3)>.