crypto: skcipher - prevent using skciphers without setting key

Similar to what was done for the hash API, update the skcipher API to
track whether each transform has been keyed, and reject
encryption/decryption if a key is needed but one hasn't been set.

This isn't as important as the equivalent fix for the hash API because
symmetric ciphers almost always require a key (the "null cipher" is the
only exception), so are unlikely to be used without one.  Still,
tracking the key will prevent accidental unkeyed use.  algif_skcipher
also had to track the key anyway, so the new flag replaces that and
simplifies the algif_skcipher implementation.

Signed-off-by: Eric Biggers <ebiggers@google.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>

1 files changed, 26 insertions, 4 deletions

diff --git a/crypto/skcipher.c b/crypto/skcipher.c
index 11af5fd6..0fe2a292 100644
--- a/crypto/skcipher.c
+++ b/crypto/skcipher.c
@@ -598,8 +598,11 @@ static int skcipher_setkey_blkcipher(struct crypto_skcipher *tfm,
 	err = crypto_blkcipher_setkey(blkcipher, key, keylen);
 	crypto_skcipher_set_flags(tfm, crypto_blkcipher_get_flags(blkcipher) &
 				       CRYPTO_TFM_RES_MASK);
+	if (err)
+		return err;
 
-	return err;
+	crypto_skcipher_clear_flags(tfm, CRYPTO_TFM_NEED_KEY);
+	return 0;
 }
 
 static int skcipher_crypt_blkcipher(struct skcipher_request *req,
@@ -674,6 +677,9 @@ static int crypto_init_skcipher_ops_blkcipher(struct crypto_tfm *tfm)
 	skcipher->ivsize = crypto_blkcipher_ivsize(blkcipher);
 	skcipher->keysize = calg->cra_blkcipher.max_keysize;
 
+	if (skcipher->keysize)
+		crypto_skcipher_set_flags(skcipher, CRYPTO_TFM_NEED_KEY);
+
 	return 0;
 }
 
@@ -692,8 +698,11 @@ static int skcipher_setkey_ablkcipher(struct crypto_skcipher *tfm,
 	crypto_skcipher_set_flags(tfm,
 				  crypto_ablkcipher_get_flags(ablkcipher) &
 				  CRYPTO_TFM_RES_MASK);
+	if (err)
+		return err;
 
-	return err;
+	crypto_skcipher_clear_flags(tfm, CRYPTO_TFM_NEED_KEY);
+	return 0;
 }
 
 static int skcipher_crypt_ablkcipher(struct skcipher_request *req,
@@ -767,6 +776,9 @@ static int crypto_init_skcipher_ops_ablkcipher(struct crypto_tfm *tfm)
 			    sizeof(struct ablkcipher_request);
 	skcipher->keysize = calg->cra_ablkcipher.max_keysize;
 
+	if (skcipher->keysize)
+		crypto_skcipher_set_flags(skcipher, CRYPTO_TFM_NEED_KEY);
+
 	return 0;
 }
 
@@ -796,6 +808,7 @@ static int skcipher_setkey(struct crypto_skcipher *tfm, const u8 *key,
 {
 	struct skcipher_alg *cipher = crypto_skcipher_alg(tfm);
 	unsigned long alignmask = crypto_skcipher_alignmask(tfm);
+	int err;
 
 	if (keylen < cipher->min_keysize || keylen > cipher->max_keysize) {
 		crypto_skcipher_set_flags(tfm, CRYPTO_TFM_RES_BAD_KEY_LEN);
@@ -803,9 +816,15 @@ static int skcipher_setkey(struct crypto_skcipher *tfm, const u8 *key,
 	}
 
 	if ((unsigned long)key & alignmask)
-		return skcipher_setkey_unaligned(tfm, key, keylen);
+		err = skcipher_setkey_unaligned(tfm, key, keylen);
+	else
+		err = cipher->setkey(tfm, key, keylen);
+
+	if (err)
+		return err;
 
-	return cipher->setkey(tfm, key, keylen);
+	crypto_skcipher_clear_flags(tfm, CRYPTO_TFM_NEED_KEY);
+	return 0;
 }
 
 static void crypto_skcipher_exit_tfm(struct crypto_tfm *tfm)
@@ -834,6 +853,9 @@ static int crypto_skcipher_init_tfm(struct crypto_tfm *tfm)
 	skcipher->ivsize = alg->ivsize;
 	skcipher->keysize = alg->max_keysize;
 
+	if (skcipher->keysize)
+		crypto_skcipher_set_flags(skcipher, CRYPTO_TFM_NEED_KEY);
+
 	if (alg->exit)
 		skcipher->base.exit = crypto_skcipher_exit_tfm;