crypto: xts - consolidate sanity check for keys

The patch centralizes the XTS key check logic into the service function
xts_check_key which is invoked from the different XTS implementations.
With this, the XTS implementations in ARM, ARM64, PPC and S390 have now
a sanity check for the XTS keys similar to the other arches.

In addition, this service function received a check to ensure that the
key != the tweak key which is mandated by FIPS 140-2 IG A.9. As the
check is not present in the standards defining XTS, it is only enforced
in FIPS mode of the kernel.

Signed-off-by: Stephan Mueller <smueller@chronox.de>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>

arch/arm/crypto/aes-ce-glue.c

@@ -152,6 +152,10 @@ static int xts_set_key(struct crypto_tfm *tfm, const u8 *in_key,
 	struct crypto_aes_xts_ctx *ctx = crypto_tfm_ctx(tfm);
 	int ret;
 
+	ret = xts_check_key(tfm, in_key, key_len);
+	if (ret)
+		return ret;
+
 	ret = ce_aes_expandkey(&ctx->key1, in_key, key_len / 2);
 	if (!ret)
 		ret = ce_aes_expandkey(&ctx->key2, &in_key[key_len / 2],

arch/arm/crypto/aesbs-glue.c

@@ -89,6 +89,11 @@ static int aesbs_xts_set_key(struct crypto_tfm *tfm, const u8 *in_key,
 {
 	struct aesbs_xts_ctx *ctx = crypto_tfm_ctx(tfm);
 	int bits = key_len * 4;
+	int err;
+
+	err = xts_check_key(tfm, in_key, key_len);
+	if (err)
+		return err;
 
 	if (private_AES_set_encrypt_key(in_key, bits, &ctx->enc.rk)) {
 		tfm->crt_flags |= CRYPTO_TFM_RES_BAD_KEY_LEN;

arch/arm64/crypto/aes-glue.c

@@ -85,6 +85,10 @@ static int xts_set_key(struct crypto_tfm *tfm, const u8 *in_key,
 	struct crypto_aes_xts_ctx *ctx = crypto_tfm_ctx(tfm);
 	int ret;
 
+	ret = xts_check_key(tfm, in_key, key_len);
+	if (ret)
+		return ret;
+
 	ret = aes_expandkey(&ctx->key1, in_key, key_len / 2);
 	if (!ret)
 		ret = aes_expandkey(&ctx->key2, &in_key[key_len / 2],

arch/powerpc/crypto/aes-spe-glue.c

@@ -126,6 +126,11 @@ static int ppc_xts_setkey(struct crypto_tfm *tfm, const u8 *in_key,
 		   unsigned int key_len)
 {
 	struct ppc_xts_ctx *ctx = crypto_tfm_ctx(tfm);
+	int err;
+
+	err = xts_check_key(tfm, in_key, key_len);
+	if (err)
+		return err;
 
 	key_len >>= 1;
 

arch/s390/crypto/aes_s390.c

@@ -587,6 +587,11 @@ static int xts_aes_set_key(struct crypto_tfm *tfm, const u8 *in_key,
 {
 	struct s390_xts_ctx *xts_ctx = crypto_tfm_ctx(tfm);
 	u32 *flags = &tfm->crt_flags;
+	int err;
+
+	err = xts_check_key(tfm, in_key, key_len);
+	if (err)
+		return err;
 
 	switch (key_len) {
 	case 32:

arch/x86/crypto/aesni-intel_glue.c

@@ -639,16 +639,11 @@ static int xts_aesni_setkey(struct crypto_tfm *tfm, const u8 *key,
 			    unsigned int keylen)
 {
 	struct aesni_xts_ctx *ctx = crypto_tfm_ctx(tfm);
-	u32 *flags = &tfm->crt_flags;
 	int err;
 
-	/* key consists of keys of equal size concatenated, therefore
-	 * the length must be even
-	 */
-	if (keylen % 2) {
-		*flags |= CRYPTO_TFM_RES_BAD_KEY_LEN;
-		return -EINVAL;
-	}
+	err = xts_check_key(tfm, key, keylen);
+	if (err)
+		return err;
 
 	/* first half of xts-key is for crypt */
 	err = aes_set_key_common(tfm, ctx->raw_crypt_ctx, key, keylen / 2);

arch/x86/crypto/camellia_glue.c

@@ -1503,13 +1503,9 @@ int xts_camellia_setkey(struct crypto_tfm *tfm, const u8 *key,
 	u32 *flags = &tfm->crt_flags;
 	int err;
 
-	/* key consists of keys of equal size concatenated, therefore
-	 * the length must be even
-	 */
-	if (keylen % 2) {
-		*flags |= CRYPTO_TFM_RES_BAD_KEY_LEN;
-		return -EINVAL;
-	}
+	err = xts_check_key(tfm, key, keylen);
+	if (err)
+		return err;
 
 	/* first half of xts-key is for crypt */
 	err = __camellia_setkey(&ctx->crypt_ctx, key, keylen / 2, flags);

arch/x86/crypto/cast6_avx_glue.c

@@ -329,13 +329,9 @@ static int xts_cast6_setkey(struct crypto_tfm *tfm, const u8 *key,
 	u32 *flags = &tfm->crt_flags;
 	int err;
 
-	/* key consists of keys of equal size concatenated, therefore
-	 * the length must be even
-	 */
-	if (keylen % 2) {
-		*flags |= CRYPTO_TFM_RES_BAD_KEY_LEN;
-		return -EINVAL;
-	}
+	err = xts_check_key(tfm, key, keylen);
+	if (err)
+		return err;
 
 	/* first half of xts-key is for crypt */
 	err = __cast6_setkey(&ctx->crypt_ctx, key, keylen / 2, flags);

arch/x86/crypto/serpent_avx_glue.c

@@ -332,16 +332,11 @@ int xts_serpent_setkey(struct crypto_tfm *tfm, const u8 *key,
 		       unsigned int keylen)
 {
 	struct serpent_xts_ctx *ctx = crypto_tfm_ctx(tfm);
-	u32 *flags = &tfm->crt_flags;
 	int err;
 
-	/* key consists of keys of equal size concatenated, therefore
-	 * the length must be even
-	 */
-	if (keylen % 2) {
-		*flags |= CRYPTO_TFM_RES_BAD_KEY_LEN;
-		return -EINVAL;
-	}
+	err = xts_check_key(tfm, key, keylen);
+	if (err)
+		return err;
 
 	/* first half of xts-key is for crypt */
 	err = __serpent_setkey(&ctx->crypt_ctx, key, keylen / 2);

arch/x86/crypto/serpent_sse2_glue.c

@@ -309,16 +309,11 @@ static int xts_serpent_setkey(struct crypto_tfm *tfm, const u8 *key,
 			      unsigned int keylen)
 {
 	struct serpent_xts_ctx *ctx = crypto_tfm_ctx(tfm);
-	u32 *flags = &tfm->crt_flags;
 	int err;
 
-	/* key consists of keys of equal size concatenated, therefore
-	 * the length must be even
-	 */
-	if (keylen % 2) {
-		*flags |= CRYPTO_TFM_RES_BAD_KEY_LEN;
-		return -EINVAL;
-	}
+	err = xts_check_key(tfm, key, keylen);
+	if (err)
+		return err;
 
 	/* first half of xts-key is for crypt */
 	err = __serpent_setkey(&ctx->crypt_ctx, key, keylen / 2);

arch/x86/crypto/twofish_glue_3way.c

@@ -277,13 +277,9 @@ int xts_twofish_setkey(struct crypto_tfm *tfm, const u8 *key,
 	u32 *flags = &tfm->crt_flags;
 	int err;
 
-	/* key consists of keys of equal size concatenated, therefore
-	 * the length must be even
-	 */
-	if (keylen % 2) {
-		*flags |= CRYPTO_TFM_RES_BAD_KEY_LEN;
-		return -EINVAL;
-	}
+	err = xts_check_key(tfm, key, keylen);
+	if (err)
+		return err;
 
 	/* first half of xts-key is for crypt */
 	err = __twofish_setkey(&ctx->crypt_ctx, key, keylen / 2, flags);

crypto/xts.c

@@ -35,16 +35,11 @@ static int setkey(struct crypto_tfm *parent, const u8 *key,
 {
 	struct priv *ctx = crypto_tfm_ctx(parent);
 	struct crypto_cipher *child = ctx->tweak;
-	u32 *flags = &parent->crt_flags;
 	int err;
 
-	/* key consists of keys of equal size concatenated, therefore
-	 * the length must be even */
-	if (keylen % 2) {
-		/* tell the user why there was an error */
-		*flags |= CRYPTO_TFM_RES_BAD_KEY_LEN;
-		return -EINVAL;
-	}
+	err = xts_check_key(parent, key, keylen);
+	if (err)
+		return err;
 
 	/* we need two cipher instances: one to compute the initial 'tweak'
 	 * by encrypting the IV (usually the 'plain' iv) and the other

include/crypto/xts.h

@@ -2,6 +2,9 @@
 #define _CRYPTO_XTS_H
 
 #include <crypto/b128ops.h>
+#include <linux/crypto.h>
+#include <crypto/algapi.h>
+#include <linux/fips.h>
 
 struct scatterlist;
 struct blkcipher_desc;
@@ -24,4 +27,28 @@ int xts_crypt(struct blkcipher_desc *desc, struct scatterlist *dst,
 	      struct scatterlist *src, unsigned int nbytes,
 	      struct xts_crypt_req *req);
 
+static inline int xts_check_key(struct crypto_tfm *tfm,
+				const u8 *key, unsigned int keylen)
+{
+	u32 *flags = &tfm->crt_flags;
+
+	/*
+	 * key consists of keys of equal size concatenated, therefore
+	 * the length must be even.
+	 */
+	if (keylen % 2) {
+		*flags |= CRYPTO_TFM_RES_BAD_KEY_LEN;
+		return -EINVAL;
+	}
+
+	/* ensure that the AES and tweak key are not identical */
+	if (fips_enabled &&
+	    !crypto_memneq(key, key + (keylen / 2), keylen / 2)) {
+		*flags |= CRYPTO_TFM_RES_WEAK_KEY;
+		return -EINVAL;
+	}
+
+	return 0;
+}
+
 #endif  /* _CRYPTO_XTS_H */