cifs: fork arc4 and add a private copy in fs/cifs

SMB supports two authentication modes, a modified krb5 mode which contains
ActiveDirectory extensions and accound information for the tickets and
NTLMSSP.

For NTLMSSP in SMB1/2/3 authentication uses a combination of all three of
md4/md5/arc4.

Fork/copy the ARC4 implementation from the crypto library into fs/cifs
so that we have a private version for NTLMSSP once ARC4 is removed from the
kernel crypto libraries.

Signed-off-by: Ronnie Sahlberg <lsahlber@redhat.com>

fs/cifs/Kconfig

@@ -10,7 +10,6 @@ config CIFS
 	select CRYPTO_SHA512
 	select CRYPTO_CMAC
 	select CRYPTO_HMAC
-	select CRYPTO_LIB_ARC4
 	select CRYPTO_AEAD2
 	select CRYPTO_CCM
 	select CRYPTO_GCM

fs/cifs/Makefile

@@ -7,7 +7,7 @@ obj-$(CONFIG_CIFS) += cifs.o
 
 cifs-y := trace.o cifsfs.o cifssmb.o cifs_debug.o connect.o dir.o file.o \
 	  inode.o link.o misc.o netmisc.o smbencrypt.o transport.o \
-	  cifs_unicode.o nterr.o cifsencrypt.o \
+	  arc4.o cifs_unicode.o nterr.o cifsencrypt.o \
 	  readdir.o ioctl.o sess.o export.o unc.o winucase.o \
 	  smb2ops.o smb2maperror.o smb2transport.o \
 	  smb2misc.o smb2pdu.o smb2inode.o smb2file.o cifsacl.o fs_context.o \

fs/cifs/arc4.c

@@ -0,0 +1,69 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * Cryptographic API
+ *
+ * ARC4 Cipher Algorithm
+ *
+ * Jon Oberheide <jon@oberheide.org>
+ */
+
+#include "arc4.h"
+
+int arc4_setkey(struct arc4_ctx *ctx, const u8 *in_key, unsigned int key_len)
+{
+	int i, j = 0, k = 0;
+
+	ctx->x = 1;
+	ctx->y = 0;
+
+	for (i = 0; i < 256; i++)
+		ctx->S[i] = i;
+
+	for (i = 0; i < 256; i++) {
+		u32 a = ctx->S[i];
+
+		j = (j + in_key[k] + a) & 0xff;
+		ctx->S[i] = ctx->S[j];
+		ctx->S[j] = a;
+		if (++k >= key_len)
+			k = 0;
+	}
+
+	return 0;
+}
+
+void arc4_crypt(struct arc4_ctx *ctx, u8 *out, const u8 *in, unsigned int len)
+{
+	u32 *const S = ctx->S;
+	u32 x, y, a, b;
+	u32 ty, ta, tb;
+
+	if (len == 0)
+		return;
+
+	x = ctx->x;
+	y = ctx->y;
+
+	a = S[x];
+	y = (y + a) & 0xff;
+	b = S[y];
+
+	do {
+		S[y] = a;
+		a = (a + b) & 0xff;
+		S[x] = b;
+		x = (x + 1) & 0xff;
+		ta = S[x];
+		ty = (y + ta) & 0xff;
+		tb = S[ty];
+		*out++ = *in++ ^ S[a];
+		if (--len == 0)
+			break;
+		y = ty;
+		a = ta;
+		b = tb;
+	} while (true);
+
+	ctx->x = x;
+	ctx->y = y;
+}

fs/cifs/arc4.h

@@ -0,0 +1,23 @@
+/* SPDX-License-Identifier: GPL-2.0+ */
+/*
+ * Common values for ARC4 Cipher Algorithm
+ */
+
+#ifndef _CRYPTO_ARC4_H
+#define _CRYPTO_ARC4_H
+
+#include <linux/types.h>
+
+#define ARC4_MIN_KEY_SIZE	1
+#define ARC4_MAX_KEY_SIZE	256
+#define ARC4_BLOCK_SIZE		1
+
+struct arc4_ctx {
+	u32 S[256];
+	u32 x, y;
+};
+
+int arc4_setkey(struct arc4_ctx *ctx, const u8 *in_key, unsigned int key_len);
+void arc4_crypt(struct arc4_ctx *ctx, u8 *out, const u8 *in, unsigned int len);
+
+#endif /* _CRYPTO_ARC4_H */

fs/cifs/cifsencrypt.c

@@ -22,7 +22,7 @@
 #include <linux/random.h>
 #include <linux/highmem.h>
 #include <linux/fips.h>
-#include <crypto/arc4.h>
+#include "arc4.h"
 #include <crypto/aead.h>
 
 int __cifs_calc_signature(struct smb_rqst *rqst,