[PATCH v2 17/18] crypto: Accept pss as valid encoding during signature verification

[Varad Gautam]

Accept pss encoding for public_key_verify_signature. If
CONFIG_CRYPTO_RSASSA_PSS is disabled, crypto_alloc_akcipher will
fail to find a pss backend anyway.

Signed-off-by: Varad Gautam <varad.gau...@suse.com>
Acked-by: Jarkko Sakkinen <jar...@kernel.org>
---
 crypto/asymmetric_keys/public_key.c | 18 +++++++++++++-----
 1 file changed, 13 insertions(+), 5 deletions(-)

diff --git a/crypto/asymmetric_keys/public_key.c 
b/crypto/asymmetric_keys/public_key.c
index 788a4ba1e2e74..b9cc83ba7a127 100644
--- a/crypto/asymmetric_keys/public_key.c
+++ b/crypto/asymmetric_keys/public_key.c
@@ -69,19 +69,20 @@ int software_key_determine_akcipher(const char *encoding,
 {
        int n;
 
-       if (strcmp(encoding, "pkcs1") == 0) {
+       if (strcmp(encoding, "pkcs1") == 0 || strcmp(encoding, "pss") == 0) {
                /* The data wangled by the RSA algorithm is typically padded
                 * and encoded in some manner, such as EMSA-PKCS1-1_5 [RFC3447
-                * sec 8.2].
+                * sec 8.2] or EMSA-PSS [RFC8017 sec 9.1].
                 */
                if (!hash_algo)
                        n = snprintf(alg_name, CRYPTO_MAX_ALG_NAME,
-                                    "pkcs1pad(%s)",
+                                    "%spad(%s)",
+                                    encoding,
                                     pkey->pkey_algo);
                else
                        n = snprintf(alg_name, CRYPTO_MAX_ALG_NAME,
-                                    "pkcs1pad(%s,%s)",
-                                    pkey->pkey_algo, hash_algo);
+                                    "%spad(%s,%s)",
+                                    encoding, pkey->pkey_algo, hash_algo);
                return n >= CRYPTO_MAX_ALG_NAME ? -EINVAL : 0;
        }
 
@@ -363,6 +364,13 @@ int public_key_verify_signature(const struct public_key 
*pkey,
                        goto error_free_key;
        }
 
+       if (strcmp(sig->encoding, "pss") == 0) {
+               ret = crypto_akcipher_set_sig_params(tfm, sig, sizeof(*sig));
+               if (ret) {
+                       goto error_free_key;
+               }
+       }
+
        sg_init_table(src_sg, 2);
        sg_set_buf(&src_sg[0], sig->s, sig->s_size);
        sg_set_buf(&src_sg[1], sig->digest, sig->digest_size);
-- 
2.30.2