Support key check in EVP interface

A new method is added to EVP_PKEY_METH as:

    int (*check) (EVP_PKEY_CTX *ctx);

and to EVP_PKEY_ASN1_METHOD as:

    int (*pkey_check) (EVP_PKEY_CTX *ctx);

This is used to check the validity of a specific key.

The order of calls is:
EVP_PKEY_check -> pmeth.check -> ameth.pkey_check.

Reviewed-by: Rich Salz <rsalz@openssl.org>
Reviewed-by: Richard Levitte <levitte@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/4337)

3 files changed, 29 insertions, 5 deletions

diff --git a/doc/man1/pkey.pod b/doc/man1/pkey.pod
index 3c277a55a3..d6b0db4d80 100644
--- a/doc/man1/pkey.pod
+++ b/doc/man1/pkey.pod
@@ -22,6 +22,7 @@ B<openssl> B<pkey>
 [B<-pubin>]
 [B<-pubout>]
 [B<-engine id>]
+[B<-check>]
 
 =head1 DESCRIPTION
 
@@ -110,6 +111,11 @@ to attempt to obtain a functional reference to the specified engine,
 thus initialising it if needed. The engine will then be set as the default
 for all available algorithms.
 
+=item B<-check>
+
+This option checks the consistency of a key pair for both public and private
+components.
+
 =back
 
 =head1 EXAMPLES
diff --git a/doc/man3/EVP_PKEY_keygen.pod b/doc/man3/EVP_PKEY_keygen.pod
index b7f2128baa..3687f9bfff 100644
--- a/doc/man3/EVP_PKEY_keygen.pod
+++ b/doc/man3/EVP_PKEY_keygen.pod
@@ -6,8 +6,8 @@ EVP_PKEY_keygen_init, EVP_PKEY_keygen, EVP_PKEY_paramgen_init,
 EVP_PKEY_paramgen, EVP_PKEY_CTX_set_cb, EVP_PKEY_CTX_get_cb,
 EVP_PKEY_CTX_get_keygen_info, EVP_PKEY_CTX_set_app_data,
 EVP_PKEY_CTX_get_app_data,
-EVP_PKEY_gen_cb
-- key and parameter generation functions
+EVP_PKEY_gen_cb, EVP_PKEY_check
+- key and parameter generation and check functions
 
 =head1 SYNOPSIS
 
@@ -28,6 +28,8 @@ EVP_PKEY_gen_cb
  void EVP_PKEY_CTX_set_app_data(EVP_PKEY_CTX *ctx, void *data);
  void *EVP_PKEY_CTX_get_app_data(EVP_PKEY_CTX *ctx);
 
+ int EVP_PKEY_check(EVP_PKEY_CTX *ctx);
+
 =head1 DESCRIPTION
 
 The EVP_PKEY_keygen_init() function initializes a public key algorithm
@@ -58,6 +60,10 @@ and retrieve an opaque pointer. This can be used to set some application
 defined value which can be retrieved in the callback: for example a handle
 which is used to update a "progress dialog".
 
+EVP_PKEY_check() validates the key-pair given by B<ctx>. This function first tries
+to use customized key check method in B<EVP_PKEY_METHOD> if it's present; otherwise
+it calls a default one defined in B<EVP_PKEY_ASN1_METHOD>.
+
 =head1 NOTES
 
 After the call to EVP_PKEY_keygen_init() or EVP_PKEY_paramgen_init() algorithm
@@ -89,6 +95,9 @@ EVP_PKEY_paramgen() return 1 for success and 0 or a negative value for failure.
 In particular a return value of -2 indicates the operation is not supported by
 the public key algorithm.
 
+EVP_PKEY_check() returns 1 for success or others for failure. It
+returns -2 if the operation is not supported for the specific algorithm.
+
 =head1 EXAMPLES
 
 Generate a 2048 bit RSA key:
@@ -171,7 +180,7 @@ These functions were first added to OpenSSL 1.0.0.
 
 =head1 COPYRIGHT
 
-Copyright 2006-2016 The OpenSSL Project Authors. All Rights Reserved.
+Copyright 2006-2017 The OpenSSL Project Authors. All Rights Reserved.
 
 Licensed under the OpenSSL license (the "License").  You may not use
 this file except in compliance with the License.  You can obtain a copy
diff --git a/doc/man3/EVP_PKEY_meth_new.pod b/doc/man3/EVP_PKEY_meth_new.pod
index 041492a8f0..acff78a16c 100644
--- a/doc/man3/EVP_PKEY_meth_new.pod
+++ b/doc/man3/EVP_PKEY_meth_new.pod
@@ -8,12 +8,12 @@ EVP_PKEY_meth_set_init, EVP_PKEY_meth_set_copy, EVP_PKEY_meth_set_cleanup,
 EVP_PKEY_meth_set_paramgen, EVP_PKEY_meth_set_keygen, EVP_PKEY_meth_set_sign,
 EVP_PKEY_meth_set_verify, EVP_PKEY_meth_set_verify_recover, EVP_PKEY_meth_set_signctx,
 EVP_PKEY_meth_set_verifyctx, EVP_PKEY_meth_set_encrypt, EVP_PKEY_meth_set_decrypt,
-EVP_PKEY_meth_set_derive, EVP_PKEY_meth_set_ctrl,
+EVP_PKEY_meth_set_derive, EVP_PKEY_meth_set_ctrl, EVP_PKEY_meth_set_check,
 EVP_PKEY_meth_get_init, EVP_PKEY_meth_get_copy, EVP_PKEY_meth_get_cleanup,
 EVP_PKEY_meth_get_paramgen, EVP_PKEY_meth_get_keygen, EVP_PKEY_meth_get_sign,
 EVP_PKEY_meth_get_verify, EVP_PKEY_meth_get_verify_recover, EVP_PKEY_meth_get_signctx,
 EVP_PKEY_meth_get_verifyctx, EVP_PKEY_meth_get_encrypt, EVP_PKEY_meth_get_decrypt,
-EVP_PKEY_meth_get_derive, EVP_PKEY_meth_get_ctrl
+EVP_PKEY_meth_get_derive, EVP_PKEY_meth_get_ctrl, EVP_PKEY_meth_get_check
 - manipulating EVP_PKEY_METHOD structure
 
 =head1 SYNOPSIS
@@ -106,6 +106,8 @@ EVP_PKEY_meth_get_derive, EVP_PKEY_meth_get_ctrl
                              int (*ctrl_str) (EVP_PKEY_CTX *ctx,
                                               const char *type,
                                               const char *value));
+ void EVP_PKEY_meth_set_check(EVP_PKEY_METHOD *pmeth,
+                              int (*check) (EVP_PKEY *pkey));
 
  void EVP_PKEY_meth_get_init(EVP_PKEY_METHOD *pmeth,
                              int (**pinit) (EVP_PKEY_CTX *ctx));
@@ -185,6 +187,8 @@ EVP_PKEY_meth_get_derive, EVP_PKEY_meth_get_ctrl
                              int (**pctrl_str) (EVP_PKEY_CTX *ctx,
                                                 const char *type,
                                                 const char *value));
+ void EVP_PKEY_meth_get_check(EVP_PKEY_METHOD *pmeth,
+                              int (**pcheck) (EVP_PKEY *pkey));
 
 =head1 DESCRIPTION
 
@@ -309,6 +313,11 @@ The digestsign() and digestverify() methods are used to generate or verify
 a signature in a one-shot mode. They could be called by L<EVP_DigetSign(3)>
 and L<EVP_DigestVerify(3)>.
 
+ int (*check) (EVP_PKEY *pkey);
+
+The check() method is used to validate a key-pair for a given B<pkey>. It
+could be called by L<EVP_PKEY_check(3)>.
+
 =head2 Functions
 
 EVP_PKEY_meth_new() creates and returns a new B<EVP_PKEY_METHOD> object,