[RFC PATCH 30/30] fs: cifs: move from the crypto cipher API to the new DES library interface

[Ard Biesheuvel <ard.biesheuvel@linaro.org>]

Some legacy code in the CIFS driver uses single DES to calculate
some password hash, and uses the crypto cipher API to do so. Given
that there is no point in invoking an accelerated cipher for doing
56-bit symmetric encryption on a single 8-byte block of input, the
flexibility of the crypto cipher API does not add much value here,
and so we're much better off using a library call into the generic
C implementation.

Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
---
 fs/cifs/Kconfig      |  2 +-
 fs/cifs/smbencrypt.c | 18 +++++++++---------
 2 files changed, 10 insertions(+), 10 deletions(-)

diff --git a/fs/cifs/Kconfig b/fs/cifs/Kconfig
index 3da294231dcc..dedab8f79ee8 100644
--- a/fs/cifs/Kconfig
+++ b/fs/cifs/Kconfig
@@ -14,7 +14,7 @@ config CIFS
 	select CRYPTO_CCM
 	select CRYPTO_ECB
 	select CRYPTO_AES
-	select CRYPTO_DES
+	select CRYPTO_LIB_DES
 	help
 	  This is the client VFS module for the SMB3 family of NAS protocols,
 	  (including support for the most recent, most secure dialect SMB3.1.1)
diff --git a/fs/cifs/smbencrypt.c b/fs/cifs/smbencrypt.c
index a0b80ac651a6..5c55c35f47d6 100644
--- a/fs/cifs/smbencrypt.c
+++ b/fs/cifs/smbencrypt.c
@@ -23,13 +23,14 @@
    Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
 */
 
-#include <linux/crypto.h>
 #include <linux/module.h>
 #include <linux/slab.h>
+#include <linux/fips.h>
 #include <linux/fs.h>
 #include <linux/string.h>
 #include <linux/kernel.h>
 #include <linux/random.h>
+#include <crypto/des.h>
 #include "cifs_fs_sb.h"
 #include "cifs_unicode.h"
 #include "cifspdu.h"
@@ -70,19 +71,18 @@ static int
 smbhash(unsigned char *out, const unsigned char *in, unsigned char *key)
 {
 	unsigned char key2[8];
-	struct crypto_cipher *tfm_des;
+	struct des_ctx ctx;
 
 	str_to_key(key, key2);
 
-	tfm_des = crypto_alloc_cipher("des", 0, 0);
-	if (IS_ERR(tfm_des)) {
-		cifs_dbg(VFS, "could not allocate des crypto API\n");
-		return PTR_ERR(tfm_des);
+	if (fips_enabled) {
+		cifs_dbg(VFS, "FIPS compliance enabled: DES not permitted\n");
+		return -ENOENT;
 	}
 
-	crypto_cipher_setkey(tfm_des, key2, 8);
-	crypto_cipher_encrypt_one(tfm_des, out, in);
-	crypto_free_cipher(tfm_des);
+	des_expand_key(&ctx, key2, DES_KEY_SIZE);
+	des_encrypt(&ctx, out, in);
+	memzero_explicit(&ctx, sizeof(ctx));
 
 	return 0;
 }
-- 
2.20.1