KEYS: Allow the public_key struct to hold a private key [ver #2]

Put a flag in the public_key struct to indicate if the structure is holding
a private key.  The private key must be held ASN.1 encoded in the format
specified in RFC 3447 A.1.2.  This is the form required by crypto/rsa.c.

The software encryption subtype's verification and query functions then
need to select the appropriate crypto function to set the key.
Signed-off-by: David Howells <dhowells@redhat.com>
Tested-by: Marcel Holtmann <marcel@holtmann.org>
Reviewed-by: Marcel Holtmann <marcel@holtmann.org>
Reviewed-by: Denis Kenzior <denkenz@gmail.com>
Tested-by: Denis Kenzior <denkenz@gmail.com>
Signed-off-by: James Morris <james.morris@microsoft.com>

crypto/asymmetric_keys/public_key.c

@@ -115,7 +115,12 @@ static int software_key_query(const struct kernel_pkey_params *params,
 	if (IS_ERR(tfm))
 		return PTR_ERR(tfm);
 
-	ret = crypto_akcipher_set_pub_key(tfm, pkey->key, pkey->keylen);
+	if (pkey->key_is_private)
+		ret = crypto_akcipher_set_priv_key(tfm,
+						   pkey->key, pkey->keylen);
+	else
+		ret = crypto_akcipher_set_pub_key(tfm,
+						  pkey->key, pkey->keylen);
 	if (ret < 0)
 		goto error_free_tfm;
 
@@ -170,7 +175,12 @@ int public_key_verify_signature(const struct public_key *pkey,
 	if (!req)
 		goto error_free_tfm;
 
-	ret = crypto_akcipher_set_pub_key(tfm, pkey->key, pkey->keylen);
+	if (pkey->key_is_private)
+		ret = crypto_akcipher_set_priv_key(tfm,
+						   pkey->key, pkey->keylen);
+	else
+		ret = crypto_akcipher_set_pub_key(tfm,
+						  pkey->key, pkey->keylen);
 	if (ret)
 		goto error_free_req;
 

include/crypto/public_key.h

@@ -25,6 +25,7 @@
 struct public_key {
 	void *key;
 	u32 keylen;
+	bool key_is_private;
 	const char *id_type;
 	const char *pkey_algo;
 };