[PATCH] crypto: fix null encryption/compression

null_encrypt() needs to copy the data in case src and dst are disjunct,
null_compress() needs to copy the data in any case as far as I can tell.  I
joined compress/decompress and encrypt/decrypt to avoid duplicating code.

Without this patch ESP null_enc packets look like this:

IP (tos 0x0, ttl  64, id 23130, offset 0, flags [DF], length: 128)
10.0.0.1 > 10.0.0.2: ESP(spi=0x0f9ca149,seq=0x4)
	0x0000:  4500 0080 5a5a 4000 4032 cbef 0a00 0001  E...ZZ@.@2......
	0x0010:  0a00 0002 0f9c a149 0000 0004 0000 0000  .......I........
	0x0020:  0000 0000 0000 0000 0000 0000 0000 0000  ................
	0x0030:  0000 0000 0000 0000 0000 0000 0000 0000  ................
	0x0040:  0000 0000 0000 0000 0000 0000 0000 0000  ................
	0x0050:  0000                                     ..

IP (tos 0x0, ttl  64, id 256, offset 0, flags [DF], length: 128)
10.0.0.2 > 10.0.0.1: ESP(spi=0x0e4f7b51,seq=0x2)
	0x0000:  4500 0080 0100 4000 4032 254a 0a00 0002  E.....@.@2%J....
	0x0010:  0a00 0001 0e4f 7b51 0000 0002 a8a8 a8a8  .....O{Q........
	0x0020:  a8a8 a8a8 a8a8 a8a8 a8a8 a8a8 a8a8 a8a8  ................
	0x0030:  a8a8 a8a8 a8a8 a8a8 a8a8 a8a8 a8a8 a8a8  ................
	0x0040:  a8a8 a8a8 a8a8 a8a8 a8a8 a8a8 a8a8 a8a8  ................
	0x0050:  a8a8                                     ..

Signed-off-by: Patrick McHardy <kaber@trash.net>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

crypto/crypto_null.c

@@ -21,6 +21,7 @@
 #include <linux/mm.h>
 #include <asm/scatterlist.h>
 #include <linux/crypto.h>
+#include <linux/string.h>
 
 #define NULL_KEY_SIZE		0
 #define NULL_BLOCK_SIZE		1
@@ -28,11 +29,13 @@
 
 static int null_compress(void *ctx, const u8 *src, unsigned int slen,
                          u8 *dst, unsigned int *dlen)
-{ return 0; }
-
-static int null_decompress(void *ctx, const u8 *src, unsigned int slen,
-                           u8 *dst, unsigned int *dlen)
-{ return 0; }
+{
+	if (slen > *dlen)
+		return -EINVAL;
+	memcpy(dst, src, slen);
+	*dlen = slen;
+	return 0;
+}
 
 static void null_init(void *ctx)
 { }
@@ -47,11 +50,10 @@ static int null_setkey(void *ctx, const u8 *key,
                        unsigned int keylen, u32 *flags)
 { return 0; }
 
-static void null_encrypt(void *ctx, u8 *dst, const u8 *src)
-{ }
-
-static void null_decrypt(void *ctx, u8 *dst, const u8 *src)
-{ }
+static void null_crypt(void *ctx, u8 *dst, const u8 *src)
+{
+	memcpy(dst, src, NULL_BLOCK_SIZE);
+}
 
 static struct crypto_alg compress_null = {
 	.cra_name		=	"compress_null",
@@ -62,7 +64,7 @@ static struct crypto_alg compress_null = {
 	.cra_list		=       LIST_HEAD_INIT(compress_null.cra_list),
 	.cra_u			=	{ .compress = {
 	.coa_compress 		=	null_compress,
-	.coa_decompress		=	null_decompress } }
+	.coa_decompress		=	null_compress } }
 };
 
 static struct crypto_alg digest_null = {
@@ -90,8 +92,8 @@ static struct crypto_alg cipher_null = {
 	.cia_min_keysize	=	NULL_KEY_SIZE,
 	.cia_max_keysize	=	NULL_KEY_SIZE,
 	.cia_setkey		= 	null_setkey,
-	.cia_encrypt		=	null_encrypt,
-	.cia_decrypt		=	null_decrypt } }
+	.cia_encrypt		=	null_crypt,
+	.cia_decrypt		=	null_crypt } }
 };
 
 MODULE_ALIAS("compress_null");