ppp: mppe: switch to RC4 library interface

The MPPE code uses the sync skcipher 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.

Note that the SHA1 shash used by this driver has several accelerated
implementations for various architectures, so retaining that part does
make sense.

Cc: linux-ppp@vger.kernel.org
Cc: Paul Mackerras <paulus@samba.org>
Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>

Author: Ard Biesheuvel

drivers/net/ppp/Kconfig

@@ -86,8 +86,7 @@ config PPP_MPPE
 	depends on PPP
 	select CRYPTO
 	select CRYPTO_SHA1
-	select CRYPTO_ARC4
-	select CRYPTO_ECB
+	select CRYPTO_LIB_ARC4
 	---help---
 	  Support for the MPPE Encryption protocol, as employed by the
 	  Microsoft Point-to-Point Tunneling Protocol.

drivers/net/ppp/ppp_mppe.c

@@ -42,9 +42,10 @@
  *                    deprecated in 2.6
  */
 
+#include <crypto/arc4.h>
 #include <crypto/hash.h>
-#include <crypto/skcipher.h>
 #include <linux/err.h>
+#include <linux/fips.h>
 #include <linux/module.h>
 #include <linux/kernel.h>
 #include <linux/init.h>
@@ -65,13 +66,6 @@ MODULE_LICENSE("Dual BSD/GPL");
 MODULE_ALIAS("ppp-compress-" __stringify(CI_MPPE));
 MODULE_VERSION("1.0.2");
 
-static unsigned int
-setup_sg(struct scatterlist *sg, const void *address, unsigned int length)
-{
-	sg_set_buf(sg, address, length);
-	return length;
-}
-
 #define SHA1_PAD_SIZE 40
 
 /*
@@ -95,7 +89,7 @@ static inline void sha_pad_init(struct sha_pad *shapad)
  * State for an MPPE (de)compressor.
  */
 struct ppp_mppe_state {
-	struct crypto_sync_skcipher *arc4;
+	struct arc4_ctx arc4;
 	struct shash_desc *sha1;
 	unsigned char *sha1_digest;
 	unsigned char master_key[MPPE_MAX_KEY_LEN];
@@ -154,24 +148,11 @@ static void get_new_key_from_sha(struct ppp_mppe_state * state)
  */
 static void mppe_rekey(struct ppp_mppe_state * state, int initial_key)
 {
-	struct scatterlist sg_in[1], sg_out[1];
-	SYNC_SKCIPHER_REQUEST_ON_STACK(req, state->arc4);
-
-	skcipher_request_set_sync_tfm(req, state->arc4);
-	skcipher_request_set_callback(req, 0, NULL, NULL);
-
 	get_new_key_from_sha(state);
 	if (!initial_key) {
-		crypto_sync_skcipher_setkey(state->arc4, state->sha1_digest,
-					    state->keylen);
-		sg_init_table(sg_in, 1);
-		sg_init_table(sg_out, 1);
-		setup_sg(sg_in, state->sha1_digest, state->keylen);
-		setup_sg(sg_out, state->session_key, state->keylen);
-		skcipher_request_set_crypt(req, sg_in, sg_out, state->keylen,
-					   NULL);
-		if (crypto_skcipher_encrypt(req))
-    		    printk(KERN_WARNING "mppe_rekey: cipher_encrypt failed\n");
+		arc4_setkey(&state->arc4, state->sha1_digest, state->keylen);
+		arc4_crypt(&state->arc4, state->session_key, state->sha1_digest,
+			   state->keylen);
 	} else {
 		memcpy(state->session_key, state->sha1_digest, state->keylen);
 	}
@@ -181,9 +162,7 @@ static void mppe_rekey(struct ppp_mppe_state * state, int initial_key)
 		state->session_key[1] = 0x26;
 		state->session_key[2] = 0x9e;
 	}
-	crypto_sync_skcipher_setkey(state->arc4, state->session_key,
-				    state->keylen);
-	skcipher_request_zero(req);
+	arc4_setkey(&state->arc4, state->session_key, state->keylen);
 }
 
 /*
@@ -196,20 +175,15 @@ static void *mppe_alloc(unsigned char *options, int optlen)
 	unsigned int digestsize;
 
 	if (optlen != CILEN_MPPE + sizeof(state->master_key) ||
-	    options[0] != CI_MPPE || options[1] != CILEN_MPPE)
+	    options[0] != CI_MPPE || options[1] != CILEN_MPPE ||
+	    fips_enabled)
 		goto out;
 
 	state = kzalloc(sizeof(*state), GFP_KERNEL);
 	if (state == NULL)
 		goto out;
 
 
-	state->arc4 = crypto_alloc_sync_skcipher("ecb(arc4)", 0, 0);
-	if (IS_ERR(state->arc4)) {
-		state->arc4 = NULL;
-		goto out_free;
-	}
-
 	shash = crypto_alloc_shash("sha1", 0, 0);
 	if (IS_ERR(shash))
 		goto out_free;
@@ -250,7 +224,6 @@ static void *mppe_alloc(unsigned char *options, int optlen)
 		crypto_free_shash(state->sha1->tfm);
 		kzfree(state->sha1);
 	}
-	crypto_free_sync_skcipher(state->arc4);
 	kfree(state);
 out:
 	return NULL;
@@ -266,8 +239,7 @@ static void mppe_free(void *arg)
 		kfree(state->sha1_digest);
 		crypto_free_shash(state->sha1->tfm);
 		kzfree(state->sha1);
-		crypto_free_sync_skcipher(state->arc4);
-		kfree(state);
+		kzfree(state);
 	}
 }
 
@@ -366,10 +338,7 @@ mppe_compress(void *arg, unsigned char *ibuf, unsigned char *obuf,
 	      int isize, int osize)
 {
 	struct ppp_mppe_state *state = (struct ppp_mppe_state *) arg;
-	SYNC_SKCIPHER_REQUEST_ON_STACK(req, state->arc4);
 	int proto;
-	int err;
-	struct scatterlist sg_in[1], sg_out[1];
 
 	/*
 	 * Check that the protocol is in the range we handle.
@@ -420,21 +389,7 @@ mppe_compress(void *arg, unsigned char *ibuf, unsigned char *obuf,
 	ibuf += 2;		/* skip to proto field */
 	isize -= 2;
 
-	/* Encrypt packet */
-	sg_init_table(sg_in, 1);
-	sg_init_table(sg_out, 1);
-	setup_sg(sg_in, ibuf, isize);
-	setup_sg(sg_out, obuf, osize);
-
-	skcipher_request_set_sync_tfm(req, state->arc4);
-	skcipher_request_set_callback(req, 0, NULL, NULL);
-	skcipher_request_set_crypt(req, sg_in, sg_out, isize, NULL);
-	err = crypto_skcipher_encrypt(req);
-	skcipher_request_zero(req);
-	if (err) {
-		printk(KERN_DEBUG "crypto_cypher_encrypt failed\n");
-		return -1;
-	}
+	arc4_crypt(&state->arc4, obuf, ibuf, isize);
 
 	state->stats.unc_bytes += isize;
 	state->stats.unc_packets++;
@@ -480,10 +435,8 @@ mppe_decompress(void *arg, unsigned char *ibuf, int isize, unsigned char *obuf,
 		int osize)
 {
 	struct ppp_mppe_state *state = (struct ppp_mppe_state *) arg;
-	SYNC_SKCIPHER_REQUEST_ON_STACK(req, state->arc4);
 	unsigned ccount;
 	int flushed = MPPE_BITS(ibuf) & MPPE_BIT_FLUSHED;
-	struct scatterlist sg_in[1], sg_out[1];
 
 	if (isize <= PPP_HDRLEN + MPPE_OVHD) {
 		if (state->debug)
@@ -610,19 +563,7 @@ mppe_decompress(void *arg, unsigned char *ibuf, int isize, unsigned char *obuf,
 	 * Decrypt the first byte in order to check if it is
 	 * a compressed or uncompressed protocol field.
 	 */
-	sg_init_table(sg_in, 1);
-	sg_init_table(sg_out, 1);
-	setup_sg(sg_in, ibuf, 1);
-	setup_sg(sg_out, obuf, 1);
-
-	skcipher_request_set_sync_tfm(req, state->arc4);
-	skcipher_request_set_callback(req, 0, NULL, NULL);
-	skcipher_request_set_crypt(req, sg_in, sg_out, 1, NULL);
-	if (crypto_skcipher_decrypt(req)) {
-		printk(KERN_DEBUG "crypto_cypher_decrypt failed\n");
-		osize = DECOMP_ERROR;
-		goto out_zap_req;
-	}
+	arc4_crypt(&state->arc4, obuf, ibuf, 1);
 
 	/*
 	 * Do PFC decompression.
@@ -637,14 +578,7 @@ mppe_decompress(void *arg, unsigned char *ibuf, int isize, unsigned char *obuf,
 	}
 
 	/* And finally, decrypt the rest of the packet. */
-	setup_sg(sg_in, ibuf + 1, isize - 1);
-	setup_sg(sg_out, obuf + 1, osize - 1);
-	skcipher_request_set_crypt(req, sg_in, sg_out, isize - 1, NULL);
-	if (crypto_skcipher_decrypt(req)) {
-		printk(KERN_DEBUG "crypto_cypher_decrypt failed\n");
-		osize = DECOMP_ERROR;
-		goto out_zap_req;
-	}
+	arc4_crypt(&state->arc4, obuf + 1, ibuf + 1, isize - 1);
 
 	state->stats.unc_bytes += osize;
 	state->stats.unc_packets++;
@@ -654,8 +588,6 @@ mppe_decompress(void *arg, unsigned char *ibuf, int isize, unsigned char *obuf,
 	/* good packet credit */
 	state->sanity_errors >>= 1;
 
-out_zap_req:
-	skcipher_request_zero(req);
 	return osize;
 
 sanity_error:
@@ -728,8 +660,7 @@ static struct compressor ppp_mppe = {
 static int __init ppp_mppe_init(void)
 {
 	int answer;
-	if (!(crypto_has_skcipher("ecb(arc4)", 0, CRYPTO_ALG_ASYNC) &&
-	      crypto_has_ahash("sha1", 0, CRYPTO_ALG_ASYNC)))
+	if (fips_enabled || !crypto_has_ahash("sha1", 0, CRYPTO_ALG_ASYNC))
 		return -ENODEV;
 
 	sha_pad = kmalloc(sizeof(struct sha_pad), GFP_KERNEL);