crypto: remove CRYPTO_TFM_RES_BAD_KEY_LEN

The CRYPTO_TFM_RES_BAD_KEY_LEN flag was apparently meant as a way to
make the ->setkey() functions provide more information about errors.

However, no one actually checks for this flag, which makes it pointless.

Also, many algorithms fail to set this flag when given a bad length key.
Reviewing just the generic implementations, this is the case for
aes-fixed-time, cbcmac, echainiv, nhpoly1305, pcrypt, rfc3686, rfc4309,
rfc7539, rfc7539esp, salsa20, seqiv, and xcbc.  But there are probably
many more in arch/*/crypto/ and drivers/crypto/.

Some algorithms can even set this flag when the key is the correct
length.  For example, authenc and authencesn set it when the key payload
is malformed in any way (not just a bad length), the atmel-sha and ccree
drivers can set it if a memory allocation fails, and the chelsio driver
sets it for bad auth tag lengths, not just bad key lengths.

So even if someone actually wanted to start checking this flag (which
seems unlikely, since it's been unused for a long time), there would be
a lot of work needed to get it working correctly.  But it would probably
be much better to go back to the drawing board and just define different
return values, like -EINVAL if the key is invalid for the algorithm vs.
-EKEYREJECTED if the key was rejected by a policy like "no weak keys".
That would be much simpler, less error-prone, and easier to test.

So just remove this flag.

Signed-off-by: Eric Biggers <ebiggers@google.com>
Reviewed-by: Horia Geantă <horia.geanta@nxp.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>

4 files changed, 10 insertions, 31 deletions

diff --git a/arch/s390/crypto/aes_s390.c b/arch/s390/crypto/aes_s390.c
index ead0b2c9881d..2db167e5871c 100644
--- a/arch/s390/crypto/aes_s390.c
+++ b/arch/s390/crypto/aes_s390.c
@@ -414,10 +414,8 @@ static int xts_aes_set_key(struct crypto_skcipher *tfm, const u8 *in_key,
 		return err;
 
 	/* In fips mode only 128 bit or 256 bit keys are valid */
-	if (fips_enabled && key_len != 32 && key_len != 64) {
-		crypto_skcipher_set_flags(tfm, CRYPTO_TFM_RES_BAD_KEY_LEN);
+	if (fips_enabled && key_len != 32 && key_len != 64)
 		return -EINVAL;
-	}
 
 	/* Pick the correct function code based on the key length */
 	fc = (key_len == 32) ? CPACF_KM_XTS_128 :
diff --git a/arch/s390/crypto/crc32-vx.c b/arch/s390/crypto/crc32-vx.c
index 423ee05887e6..fafecad20752 100644
--- a/arch/s390/crypto/crc32-vx.c
+++ b/arch/s390/crypto/crc32-vx.c
@@ -111,10 +111,8 @@ static int crc32_vx_setkey(struct crypto_shash *tfm, const u8 *newkey,
 {
 	struct crc_ctx *mctx = crypto_shash_ctx(tfm);
 
-	if (newkeylen != sizeof(mctx->key)) {
-		crypto_shash_set_flags(tfm, CRYPTO_TFM_RES_BAD_KEY_LEN);
+	if (newkeylen != sizeof(mctx->key))
 		return -EINVAL;
-	}
 	mctx->key = le32_to_cpu(*(__le32 *)newkey);
 	return 0;
 }
@@ -124,10 +122,8 @@ static int crc32be_vx_setkey(struct crypto_shash *tfm, const u8 *newkey,
 {
 	struct crc_ctx *mctx = crypto_shash_ctx(tfm);
 
-	if (newkeylen != sizeof(mctx->key)) {
-		crypto_shash_set_flags(tfm, CRYPTO_TFM_RES_BAD_KEY_LEN);
+	if (newkeylen != sizeof(mctx->key))
 		return -EINVAL;
-	}
 	mctx->key = be32_to_cpu(*(__be32 *)newkey);
 	return 0;
 }
diff --git a/arch/s390/crypto/ghash_s390.c b/arch/s390/crypto/ghash_s390.c
index a3e7400e031c..6b07a2f1ce8a 100644
--- a/arch/s390/crypto/ghash_s390.c
+++ b/arch/s390/crypto/ghash_s390.c
@@ -43,10 +43,8 @@ static int ghash_setkey(struct crypto_shash *tfm,
 {
 	struct ghash_ctx *ctx = crypto_shash_ctx(tfm);
 
-	if (keylen != GHASH_BLOCK_SIZE) {
-		crypto_shash_set_flags(tfm, CRYPTO_TFM_RES_BAD_KEY_LEN);
+	if (keylen != GHASH_BLOCK_SIZE)
 		return -EINVAL;
-	}
 
 	memcpy(ctx->key, key, GHASH_BLOCK_SIZE);
 
diff --git a/arch/s390/crypto/paes_s390.c b/arch/s390/crypto/paes_s390.c
index c7119c617b6e..e2a85783f804 100644
--- a/arch/s390/crypto/paes_s390.c
+++ b/arch/s390/crypto/paes_s390.c
@@ -151,11 +151,7 @@ static int ecb_paes_set_key(struct crypto_skcipher *tfm, const u8 *in_key,
 	if (rc)
 		return rc;
 
-	if (__paes_set_key(ctx)) {
-		crypto_skcipher_set_flags(tfm, CRYPTO_TFM_RES_BAD_KEY_LEN);
-		return -EINVAL;
-	}
-	return 0;
+	return __paes_set_key(ctx);
 }
 
 static int ecb_paes_crypt(struct skcipher_request *req, unsigned long modifier)
@@ -254,11 +250,7 @@ static int cbc_paes_set_key(struct crypto_skcipher *tfm, const u8 *in_key,
 	if (rc)
 		return rc;
 
-	if (__cbc_paes_set_key(ctx)) {
-		crypto_skcipher_set_flags(tfm, CRYPTO_TFM_RES_BAD_KEY_LEN);
-		return -EINVAL;
-	}
-	return 0;
+	return __cbc_paes_set_key(ctx);
 }
 
 static int cbc_paes_crypt(struct skcipher_request *req, unsigned long modifier)
@@ -386,10 +378,9 @@ static int xts_paes_set_key(struct crypto_skcipher *tfm, const u8 *in_key,
 	if (rc)
 		return rc;
 
-	if (__xts_paes_set_key(ctx)) {
-		crypto_skcipher_set_flags(tfm, CRYPTO_TFM_RES_BAD_KEY_LEN);
-		return -EINVAL;
-	}
+	rc = __xts_paes_set_key(ctx);
+	if (rc)
+		return rc;
 
 	/*
 	 * xts_check_key verifies the key length is not odd and makes
@@ -526,11 +517,7 @@ static int ctr_paes_set_key(struct crypto_skcipher *tfm, const u8 *in_key,
 	if (rc)
 		return rc;
 
-	if (__ctr_paes_set_key(ctx)) {
-		crypto_skcipher_set_flags(tfm, CRYPTO_TFM_RES_BAD_KEY_LEN);
-		return -EINVAL;
-	}
-	return 0;
+	return __ctr_paes_set_key(ctx);
 }
 
 static unsigned int __ctrblk_init(u8 *ctrptr, u8 *iv, unsigned int nbytes)