[PATCH v3 7/7] fs: cifs: switch to RC4 library interface

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

The CIFS code uses the sync skcipher API to invoke the ecb(arc4) skcipher,
of which only a single generic C code implementation exists. This means
that going through all the trouble of using scatterlists etc buys us
very little, and we're better off just invoking the arc4 library directly.

Cc: linux-cifs@vger.kernel.org
Cc: Steve French <sfrench@samba.org>
Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
---
 fs/cifs/Kconfig       |  2 +-
 fs/cifs/cifsencrypt.c | 53 ++++++--------------
 2 files changed, 16 insertions(+), 39 deletions(-)

diff --git a/fs/cifs/Kconfig b/fs/cifs/Kconfig
index aae2b8b2adf5..523e9ea78a28 100644
--- a/fs/cifs/Kconfig
+++ b/fs/cifs/Kconfig
@@ -10,7 +10,7 @@ config CIFS
 	select CRYPTO_SHA512
 	select CRYPTO_CMAC
 	select CRYPTO_HMAC
-	select CRYPTO_ARC4
+	select CRYPTO_LIB_ARC4
 	select CRYPTO_AEAD2
 	select CRYPTO_CCM
 	select CRYPTO_ECB
diff --git a/fs/cifs/cifsencrypt.c b/fs/cifs/cifsencrypt.c
index d2a05e46d6f5..3b7b5e83493d 100644
--- a/fs/cifs/cifsencrypt.c
+++ b/fs/cifs/cifsencrypt.c
@@ -33,7 +33,8 @@
 #include <linux/ctype.h>
 #include <linux/random.h>
 #include <linux/highmem.h>
-#include <crypto/skcipher.h>
+#include <linux/fips.h>
+#include <crypto/arc4.h>
 #include <crypto/aead.h>
 
 int __cifs_calc_signature(struct smb_rqst *rqst,
@@ -772,11 +773,12 @@ setup_ntlmv2_rsp(struct cifs_ses *ses, const struct nls_table *nls_cp)
 int
 calc_seckey(struct cifs_ses *ses)
 {
-	int rc;
-	struct crypto_skcipher *tfm_arc4;
-	struct scatterlist sgin, sgout;
-	struct skcipher_request *req;
+	struct arc4_ctx *ctx_arc4;
 	unsigned char *sec_key;
+	int rc = 0;
+
+	if (fips_enabled)
+		return -ENODEV;
 
 	sec_key = kmalloc(CIFS_SESS_KEY_SIZE, GFP_KERNEL);
 	if (sec_key == NULL)
@@ -784,49 +786,24 @@ calc_seckey(struct cifs_ses *ses)
 
 	get_random_bytes(sec_key, CIFS_SESS_KEY_SIZE);
 
-	tfm_arc4 = crypto_alloc_skcipher("ecb(arc4)", 0, CRYPTO_ALG_ASYNC);
-	if (IS_ERR(tfm_arc4)) {
-		rc = PTR_ERR(tfm_arc4);
-		cifs_dbg(VFS, "could not allocate crypto API arc4\n");
-		goto out;
-	}
-
-	rc = crypto_skcipher_setkey(tfm_arc4, ses->auth_key.response,
-					CIFS_SESS_KEY_SIZE);
-	if (rc) {
-		cifs_dbg(VFS, "%s: Could not set response as a key\n",
-			 __func__);
-		goto out_free_cipher;
-	}
-
-	req = skcipher_request_alloc(tfm_arc4, GFP_KERNEL);
-	if (!req) {
+	ctx_arc4 = kmalloc(sizeof(*ctx_arc4), GFP_KERNEL);
+	if (!ctx_arc4) {
 		rc = -ENOMEM;
-		cifs_dbg(VFS, "could not allocate crypto API arc4 request\n");
-		goto out_free_cipher;
+		cifs_dbg(VFS, "could not allocate arc4 context\n");
+		goto out;
 	}
 
-	sg_init_one(&sgin, sec_key, CIFS_SESS_KEY_SIZE);
-	sg_init_one(&sgout, ses->ntlmssp->ciphertext, CIFS_CPHTXT_SIZE);
-
-	skcipher_request_set_callback(req, 0, NULL, NULL);
-	skcipher_request_set_crypt(req, &sgin, &sgout, CIFS_CPHTXT_SIZE, NULL);
-
-	rc = crypto_skcipher_encrypt(req);
-	skcipher_request_free(req);
-	if (rc) {
-		cifs_dbg(VFS, "could not encrypt session key rc: %d\n", rc);
-		goto out_free_cipher;
-	}
+	arc4_setkey(ctx_arc4, ses->auth_key.response, CIFS_SESS_KEY_SIZE);
+	arc4_crypt(ctx_arc4, ses->ntlmssp->ciphertext, sec_key,
+		   CIFS_CPHTXT_SIZE);
 
 	/* make secondary_key/nonce as session key */
 	memcpy(ses->auth_key.response, sec_key, CIFS_SESS_KEY_SIZE);
 	/* and make len as that of session key only */
 	ses->auth_key.len = CIFS_SESS_KEY_SIZE;
 
-out_free_cipher:
-	crypto_free_skcipher(tfm_arc4);
 out:
+	kfree(ctx_arc4);
 	kfree(sec_key);
 	return rc;
 }
-- 
2.20.1