fs: cifs: move from the crypto cipher API to the new DES library interface

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>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>

3 files changed, 10 insertions, 11 deletions

diff --git a/fs/cifs/Kconfig b/fs/cifs/Kconfig
index b16219e5dac9..350bc3061656 100644
--- a/fs/cifs/Kconfig
+++ b/fs/cifs/Kconfig
@@ -16,7 +16,7 @@ config CIFS
         select CRYPTO_GCM
         select CRYPTO_ECB
         select CRYPTO_AES
-        select CRYPTO_DES
+        select CRYPTO_LIB_DES
         select KEYS
         help
           This is the client VFS module for the SMB3 family of NAS protocols,
diff --git a/fs/cifs/cifsfs.c b/fs/cifs/cifsfs.c
index 3289b566463f..4e2f74894e9b 100644
--- a/fs/cifs/cifsfs.c
+++ b/fs/cifs/cifsfs.c
@@ -1601,7 +1601,6 @@ MODULE_DESCRIPTION
         ("VFS to access SMB3 servers e.g. Samba, Macs, Azure and Windows (and "
         "also older servers complying with the SNIA CIFS Specification)");
 MODULE_VERSION(CIFS_VERSION);
-MODULE_SOFTDEP("pre: des");
 MODULE_SOFTDEP("pre: ecb");
 MODULE_SOFTDEP("pre: hmac");
 MODULE_SOFTDEP("pre: md4");
diff --git a/fs/cifs/smbencrypt.c b/fs/cifs/smbencrypt.c
index 2b6d87bfdf8e..39a938443e3e 100644
--- a/fs/cifs/smbencrypt.c
+++ b/fs/cifs/smbencrypt.c
@@ -11,13 +11,14 @@
 
 */
 
-#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"
@@ -58,19 +59,18 @@ 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;
 }