crypto: sig - Prepare for algorithms with variable signature size

The callers of crypto_sig_sign() assume that the signature size is
always equivalent to the key size.

This happens to be true for RSA, which is currently the only algorithm
implementing the ->sign() callback.  But it is false e.g. for X9.62
encoded ECDSA signatures because they have variable length.

Prepare for addition of a ->sign() callback to such algorithms by
letting the callback return the signature size (or a negative integer
on error).  When testing the ->sign() callback in test_sig_one(),
use crypto_sig_maxsize() instead of crypto_sig_keysize() to verify that
the test vector's signature does not exceed an algorithm's maximum
signature size.

There has been a relatively recent effort to upstream ECDSA signature
generation support which may benefit from this change:

https://lore.kernel.org/linux-crypto/20220908200036.2034-1-ignat@cloudflare.com/

However the main motivation for this commit is to reduce the number of
crypto_sig_keysize() callers:  This function is about to be changed to
return the size in bits instead of bytes and that will require amending
most callers to divide the return value by 8.

Signed-off-by: Lukas Wunner <lukas@wunner.de>
Reviewed-by: Stefan Berger <stefanb@linux.ibm.com>
Cc: Ignat Korchagin <ignat@cloudflare.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>

diff --git a/crypto/asymmetric_keys/public_key.c b/crypto/asymmetric_keys/public_key.c
index bbd07a9022e60994f647ba4ab8dc71b6f7144537..bf165d321440d5dbfdd8ad5547b37f85bb566e64 100644 (file)
--- a/crypto/asymmetric_keys/public_key.c
+++ b/crypto/asymmetric_keys/public_key.c
@@ -267,7 +267,6 @@ static int software_key_eds_op(struct kernel_pkey_params *params,
        struct crypto_sig *sig;
        char *key, *ptr;
        bool issig;
-       int ksz;
        int ret;
 
        pr_devel("==>%s()\n", __func__);
@@ -302,8 +301,6 @@ static int software_key_eds_op(struct kernel_pkey_params *params,
                        ret = crypto_sig_set_pubkey(sig, key, pkey->keylen);
                if (ret)
                        goto error_free_tfm;
-
-               ksz = crypto_sig_keysize(sig);
        } else {
                tfm = crypto_alloc_akcipher(alg_name, 0, 0);
                if (IS_ERR(tfm)) {
@@ -317,8 +314,6 @@ static int software_key_eds_op(struct kernel_pkey_params *params,
                        ret = crypto_akcipher_set_pub_key(tfm, key, pkey->keylen);
                if (ret)
                        goto error_free_tfm;
-
-               ksz = crypto_akcipher_maxsize(tfm);
        }
 
        ret = -EINVAL;
@@ -347,8 +342,8 @@ static int software_key_eds_op(struct kernel_pkey_params *params,
                BUG();
        }
 
-       if (ret == 0)
-               ret = ksz;
+       if (!issig && ret == 0)
+               ret = crypto_akcipher_maxsize(tfm);
 
 error_free_tfm:
        if (issig)

diff --git a/crypto/rsassa-pkcs1.c b/crypto/rsassa-pkcs1.c
index f68ffd338f483f12358e37f2b01c32ae169c2323..d01ac75635e00881b9b7a10356dd72d9fc6184c2 100644 (file)
--- a/crypto/rsassa-pkcs1.c
+++ b/crypto/rsassa-pkcs1.c
@@ -210,7 +210,7 @@ static int rsassa_pkcs1_sign(struct crypto_sig *tfm,
                memset(dst, 0, pad_len);
        }
 
-       return 0;
+       return ctx->key_size;
 }
 
 static int rsassa_pkcs1_verify(struct crypto_sig *tfm,

diff --git a/crypto/testmgr.c b/crypto/testmgr.c
index e61490ba409589777cdcb757032fa627a1d7848e..b69877db3f33dee9affbe2d343cd4fc900a37ffd 100644 (file)
--- a/crypto/testmgr.c
+++ b/crypto/testmgr.c
@@ -4328,7 +4328,7 @@ static int test_sig_one(struct crypto_sig *tfm, const struct sig_testvec *vecs)
        if (vecs->public_key_vec)
                return 0;
 
-       sig_size = crypto_sig_keysize(tfm);
+       sig_size = crypto_sig_maxsize(tfm);
        if (sig_size < vecs->c_size) {
                pr_err("alg: sig: invalid maxsize %u\n", sig_size);
                return -EINVAL;
@@ -4340,13 +4340,14 @@ static int test_sig_one(struct crypto_sig *tfm, const struct sig_testvec *vecs)
 
        /* Run asymmetric signature generation */
        err = crypto_sig_sign(tfm, vecs->m, vecs->m_size, sig, sig_size);
-       if (err) {
+       if (err < 0) {
                pr_err("alg: sig: sign test failed: err %d\n", err);
                return err;
        }
 
        /* Verify that generated signature equals cooked signature */
-       if (memcmp(sig, vecs->c, vecs->c_size) ||
+       if (err != vecs->c_size ||
+           memcmp(sig, vecs->c, vecs->c_size) ||
            memchr_inv(sig + vecs->c_size, 0, sig_size - vecs->c_size)) {
                pr_err("alg: sig: sign test failed: invalid output\n");
                hexdump(sig, sig_size);

diff --git a/include/crypto/sig.h b/include/crypto/sig.h
index cff41ad93824c06a51d2e9f21a3d2f0c60d9af75..11024708c06929b401b6108fb976a996d9d48639 100644 (file)
--- a/include/crypto/sig.h
+++ b/include/crypto/sig.h
@@ -23,7 +23,8 @@ struct crypto_sig {
  * struct sig_alg - generic public key signature algorithm
  *
  * @sign:      Function performs a sign operation as defined by public key
- *             algorithm. Optional.
+ *             algorithm. On success, the signature size is returned.
+ *             Optional.
  * @verify:    Function performs a complete verify operation as defined by
  *             public key algorithm, returning verification status. Optional.
  * @set_pub_key: Function invokes the algorithm specific set public key
@@ -186,7 +187,7 @@ static inline unsigned int crypto_sig_maxsize(struct crypto_sig *tfm)
  * @dst:       destination obuffer
  * @dlen:      destination length
  *
- * Return: zero on success; error code in case of error
+ * Return: signature size on success; error code in case of error
  */
 static inline int crypto_sig_sign(struct crypto_sig *tfm,
                                  const void *src, unsigned int slen,