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

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Date:   Thu,  8 Apr 2021 16:15:15 +0200
From:   Varad Gautam <varad.gautam@...e.com>
To:     linux-crypto@...r.kernel.org
CC:     varad.gautam@...e.com, dhowells@...hat.com,
        herbert@...dor.apana.org.au, davem@...emloft.net, vt@...linux.org,
        tianjia.zhang@...ux.alibaba.com, keyrings@...r.kernel.org,
        linux-kernel@...r.kernel.org, jarkko@...nel.org
Subject: [PATCH v2 17/18] crypto: Accept pss as valid encoding during signature verification

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.gautam@...e.com>
Acked-by: Jarkko Sakkinen <jarkko@...nel.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