KEYS: Split public_key_verify_signature() and make available

Modify public_key_verify_signature() so that it now takes a public_key struct
rather than a key struct and supply a wrapper that takes a key struct.  The
wrapper is then used by the asymmetric key subtype and the modified function is
used by X.509 self-signature checking and can be used by other things also.

Signed-off-by: David Howells <dhowells@redhat.com>
Reviewed-by: Kees Cook <keescook@chromium.org>
Reviewed-by: Josh Boyer <jwboyer@redhat.com>

3 files changed, 39 insertions, 9 deletions

diff --git a/crypto/asymmetric_keys/public_key.c b/crypto/asymmetric_keys/public_key.c
index 796ce0802aa0..49ac8d848ed1 100644
--- a/crypto/asymmetric_keys/public_key.c
+++ b/crypto/asymmetric_keys/public_key.c
@@ -86,21 +86,45 @@ EXPORT_SYMBOL_GPL(public_key_destroy);
 /*
  * Verify a signature using a public key.
  */
-static int public_key_verify_signature(const struct key *key,
-                                       const struct public_key_signature *sig)
+int public_key_verify_signature(const struct public_key *pk,
+                                const struct public_key_signature *sig)
 {
-        const struct public_key *pk = key->payload.data;
+        const struct public_key_algorithm *algo;
+
+        BUG_ON(!pk);
+        BUG_ON(!pk->mpi[0]);
+        BUG_ON(!pk->mpi[1]);
+        BUG_ON(!sig);
+        BUG_ON(!sig->digest);
+        BUG_ON(!sig->mpi[0]);
+
+        algo = pk->algo;
+        if (!algo) {
+                if (pk->pkey_algo >= PKEY_ALGO__LAST)
+                        return -ENOPKG;
+                algo = pkey_algo[pk->pkey_algo];
+                if (!algo)
+                        return -ENOPKG;
+        }
 
-        if (!pk->algo->verify_signature)
+        if (!algo->verify_signature)
                 return -ENOTSUPP;
 
-        if (sig->nr_mpi != pk->algo->n_sig_mpi) {
+        if (sig->nr_mpi != algo->n_sig_mpi) {
                 pr_debug("Signature has %u MPI not %u\n",
-                         sig->nr_mpi, pk->algo->n_sig_mpi);
+                         sig->nr_mpi, algo->n_sig_mpi);
                 return -EINVAL;
         }
 
-        return pk->algo->verify_signature(pk, sig);
+        return algo->verify_signature(pk, sig);
+}
+EXPORT_SYMBOL_GPL(public_key_verify_signature);
+
+static int public_key_verify_signature_2(const struct key *key,
+                                         const struct public_key_signature *sig)
+{
+        const struct public_key *pk = key->payload.data;
+        return public_key_verify_signature(pk, sig);
 }
 
 /*
@@ -111,6 +135,6 @@ struct asymmetric_key_subtype public_key_subtype = {
         .name                   = "public_key",
         .describe               = public_key_describe,
         .destroy                = public_key_destroy,
-        .verify_signature       = public_key_verify_signature,
+        .verify_signature       = public_key_verify_signature_2,
 };
 EXPORT_SYMBOL_GPL(public_key_subtype);
diff --git a/crypto/asymmetric_keys/public_key.h b/crypto/asymmetric_keys/public_key.h
index 5e5e35626899..5c37a22a0637 100644
--- a/crypto/asymmetric_keys/public_key.h
+++ b/crypto/asymmetric_keys/public_key.h
@@ -28,3 +28,9 @@ struct public_key_algorithm {
 };
 
 extern const struct public_key_algorithm RSA_public_key_algorithm;
+
+/*
+ * public_key.c
+ */
+extern int public_key_verify_signature(const struct public_key *pk,
+                                       const struct public_key_signature *sig);
diff --git a/crypto/asymmetric_keys/x509_public_key.c b/crypto/asymmetric_keys/x509_public_key.c
index fac574c457b3..8cb2f7075479 100644
--- a/crypto/asymmetric_keys/x509_public_key.c
+++ b/crypto/asymmetric_keys/x509_public_key.c
@@ -76,7 +76,7 @@ static int x509_check_signature(const struct public_key *pub,
         if (ret < 0)
                 goto error_mpi;
 
-        ret = pub->algo->verify_signature(pub, sig);
+        ret = public_key_verify_signature(pub, sig);
 
         pr_debug("Cert Verification: %d\n", ret);