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: [e-mail]
Cc: Paul Mackerras <[e-mail]>
Signed-off-by: Ard Biesheuvel <[e-mail]>
Signed-off-by: Herbert Xu <[e-mail]>

drivers/net/ppp/Kconfig

···
 	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

···
  *                    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>
···
 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
 
···
  * 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];
···
  */
 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);
 	}
···
 		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);
 }
 
 /*
···
 	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))
···
 		crypto_free_shash(state->sha1->tfm);
 		kzfree(state->sha1);
 	}
-	crypto_free_sync_skcipher(state->arc4);
 	kfree(state);
 out:
 	return NULL;
···
 		kfree(state->sha1_digest);
 		crypto_free_shash(state->sha1->tfm);
 		kzfree(state->sha1);
-		crypto_free_sync_skcipher(state->arc4);
-		kfree(state);
+		kzfree(state);
 	}
 }
 
···
 	      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.
···
 	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++;
···
 		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)
···
 	 * 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.
···
 	}
 
 	/* 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++;
···
 	/* good packet credit */
 	state->sanity_errors >>= 1;
 
-out_zap_req:
-	skcipher_request_zero(req);
 	return osize;
 
 sanity_error:
···
 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);