linux-kernel - [PATCH 3.2 044/153] crypto: hash - annotate algorithms taking optional key

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Message-ID: <lsq.1527677561.685610822@decadent.org.uk>
Date:   Wed, 30 May 2018 11:52:41 +0100
From:   Ben Hutchings <ben@...adent.org.uk>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
CC:     akpm@...ux-foundation.org,
        "Herbert Xu" <herbert@...dor.apana.org.au>,
        "Eric Biggers" <ebiggers@...gle.com>
Subject: [PATCH 3.2 044/153] crypto: hash - annotate algorithms taking
 optional key

3.2.102-rc1 review patch.  If anyone has any objections, please let me know.

------------------

From: Eric Biggers <ebiggers@...gle.com>

commit a208fa8f33031b9e0aba44c7d1b7e68eb0cbd29e upstream.

We need to consistently enforce that keyed hashes cannot be used without
setting the key.  To do this we need a reliable way to determine whether
a given hash algorithm is keyed or not.  AF_ALG currently does this by
checking for the presence of a ->setkey() method.  However, this is
actually slightly broken because the CRC-32 algorithms implement
->setkey() but can also be used without a key.  (The CRC-32 "key" is not
actually a cryptographic key but rather represents the initial state.
If not overridden, then a default initial state is used.)

Prepare to fix this by introducing a flag CRYPTO_ALG_OPTIONAL_KEY which
indicates that the algorithm has a ->setkey() method, but it is not
required to be called.  Then set it on all the CRC-32 algorithms.

The same also applies to the Adler-32 implementation in Lustre.

Also, the cryptd and mcryptd templates have to pass through the flag
from their underlying algorithm.

Signed-off-by: Eric Biggers <ebiggers@...gle.com>
Signed-off-by: Herbert Xu <herbert@...dor.apana.org.au>
[bwh: Backported to 3.2:
 - Drop changes to nonexistent drivers
 - There's no CRYPTO_ALG_INTERNAL flag
 - Adjust filenames]
Signed-off-by: Ben Hutchings <ben@...adent.org.uk>
---
--- a/arch/x86/crypto/crc32c-intel.c
+++ b/arch/x86/crypto/crc32c-intel.c
@@ -166,6 +166,7 @@ static struct shash_alg alg = {
 		.cra_name		=	"crc32c",
 		.cra_driver_name	=	"crc32c-intel",
 		.cra_priority		=	200,
+		.cra_flags		=	CRYPTO_ALG_OPTIONAL_KEY,
 		.cra_blocksize		=	CHKSUM_BLOCK_SIZE,
 		.cra_ctxsize		=	sizeof(u32),
 		.cra_module		=	THIS_MODULE,
--- a/crypto/crc32c.c
+++ b/crypto/crc32c.c
@@ -234,6 +234,7 @@ static struct shash_alg alg = {
 		.cra_name		=	"crc32c",
 		.cra_driver_name	=	"crc32c-generic",
 		.cra_priority		=	100,
+		.cra_flags		=	CRYPTO_ALG_OPTIONAL_KEY,
 		.cra_blocksize		=	CHKSUM_BLOCK_SIZE,
 		.cra_alignmask		=	3,
 		.cra_ctxsize		=	sizeof(struct chksum_ctx),
--- a/crypto/cryptd.c
+++ b/crypto/cryptd.c
@@ -603,7 +603,8 @@ static int cryptd_create_hash(struct cry
 	if (err)
 		goto out_free_inst;
 
-	inst->alg.halg.base.cra_flags = CRYPTO_ALG_ASYNC;
+	inst->alg.halg.base.cra_flags = CRYPTO_ALG_ASYNC |
+		(alg->cra_flags & CRYPTO_ALG_OPTIONAL_KEY);
 
 	inst->alg.halg.digestsize = salg->digestsize;
 	inst->alg.halg.base.cra_ctxsize = sizeof(struct cryptd_hash_ctx);
--- a/include/linux/crypto.h
+++ b/include/linux/crypto.h
@@ -89,6 +89,12 @@
 #define CRYPTO_ALG_INSTANCE		0x00000800
 
 /*
+ * Set if the algorithm has a ->setkey() method but can be used without
+ * calling it first, i.e. there is a default key.
+ */
+#define CRYPTO_ALG_OPTIONAL_KEY		0x00004000
+
+/*
  * Transform masks and values (for crt_flags).
  */
 #define CRYPTO_TFM_REQ_MASK		0x000fff00