crypto: gcm - make GMAC work when dst and src are different

The GMAC code assumes that dst==src, which causes problems when trying to add
rfc4543(gcm(aes)) test vectors.

So fix this code to work when source and destination buffer are different.
Signed-off-by: Jussi Kivilinna <jussi.kivilinna@iki.fi>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>

crypto/Kconfig

@@ -198,6 +198,7 @@ config CRYPTO_GCM
 	select CRYPTO_CTR
 	select CRYPTO_AEAD
 	select CRYPTO_GHASH
+	select CRYPTO_NULL
 	help
 	  Support for Galois/Counter Mode (GCM) and Galois Message
 	  Authentication Code (GMAC). Required for IPSec.

crypto/gcm.c

@@ -37,8 +37,14 @@ struct crypto_rfc4106_ctx {
 	u8 nonce[4];
 };
 
+struct crypto_rfc4543_instance_ctx {
+	struct crypto_aead_spawn aead;
+	struct crypto_skcipher_spawn null;
+};
+
 struct crypto_rfc4543_ctx {
 	struct crypto_aead *child;
+	struct crypto_blkcipher *null;
 	u8 nonce[4];
 };
 
@@ -1094,20 +1100,20 @@ static int crypto_rfc4543_setauthsize(struct crypto_aead *parent,
 }
 
 static struct aead_request *crypto_rfc4543_crypt(struct aead_request *req,
-						 int enc)
+						 bool enc)
 {
 	struct crypto_aead *aead = crypto_aead_reqtfm(req);
 	struct crypto_rfc4543_ctx *ctx = crypto_aead_ctx(aead);
 	struct crypto_rfc4543_req_ctx *rctx = crypto_rfc4543_reqctx(req);
 	struct aead_request *subreq = &rctx->subreq;
-	struct scatterlist *dst = req->dst;
+	struct scatterlist *src = req->src;
 	struct scatterlist *cipher = rctx->cipher;
 	struct scatterlist *payload = rctx->payload;
 	struct scatterlist *assoc = rctx->assoc;
 	unsigned int authsize = crypto_aead_authsize(aead);
 	unsigned int assoclen = req->assoclen;
-	struct page *dstp;
-	u8 *vdst;
+	struct page *srcp;
+	u8 *vsrc;
 	u8 *iv = PTR_ALIGN((u8 *)(rctx + 1) + crypto_aead_reqsize(ctx->child),
 			   crypto_aead_alignmask(ctx->child) + 1);
 
@@ -1118,19 +1124,19 @@ static struct aead_request *crypto_rfc4543_crypt(struct aead_request *req,
 	if (enc)
 		memset(rctx->auth_tag, 0, authsize);
 	else
-		scatterwalk_map_and_copy(rctx->auth_tag, dst,
+		scatterwalk_map_and_copy(rctx->auth_tag, src,
 					 req->cryptlen - authsize,
 					 authsize, 0);
 
 	sg_init_one(cipher, rctx->auth_tag, authsize);
 
 	/* construct the aad */
-	dstp = sg_page(dst);
-	vdst = PageHighMem(dstp) ? NULL : page_address(dstp) + dst->offset;
+	srcp = sg_page(src);
+	vsrc = PageHighMem(srcp) ? NULL : page_address(srcp) + src->offset;
 
 	sg_init_table(payload, 2);
 	sg_set_buf(payload, req->iv, 8);
-	scatterwalk_crypto_chain(payload, dst, vdst == req->iv + 8, 2);
+	scatterwalk_crypto_chain(payload, src, vsrc == req->iv + 8, 2);
 	assoclen += 8 + req->cryptlen - (enc ? 0 : authsize);
 
 	sg_init_table(assoc, 2);
@@ -1147,6 +1153,19 @@ static struct aead_request *crypto_rfc4543_crypt(struct aead_request *req,
 	return subreq;
 }
 
+static int crypto_rfc4543_copy_src_to_dst(struct aead_request *req, bool enc)
+{
+	struct crypto_aead *aead = crypto_aead_reqtfm(req);
+	struct crypto_rfc4543_ctx *ctx = crypto_aead_ctx(aead);
+	unsigned int authsize = crypto_aead_authsize(aead);
+	unsigned int nbytes = req->cryptlen - (enc ? 0 : authsize);
+	struct blkcipher_desc desc = {
+		.tfm = ctx->null,
+	};
+
+	return crypto_blkcipher_encrypt(&desc, req->dst, req->src, nbytes);
+}
+
 static int crypto_rfc4543_encrypt(struct aead_request *req)
 {
 	struct crypto_aead *aead = crypto_aead_reqtfm(req);
@@ -1154,7 +1173,13 @@ static int crypto_rfc4543_encrypt(struct aead_request *req)
 	struct aead_request *subreq;
 	int err;
 
-	subreq = crypto_rfc4543_crypt(req, 1);
+	if (req->src != req->dst) {
+		err = crypto_rfc4543_copy_src_to_dst(req, true);
+		if (err)
+			return err;
+	}
+
+	subreq = crypto_rfc4543_crypt(req, true);
 	err = crypto_aead_encrypt(subreq);
 	if (err)
 		return err;
@@ -1167,7 +1192,15 @@ static int crypto_rfc4543_encrypt(struct aead_request *req)
 
 static int crypto_rfc4543_decrypt(struct aead_request *req)
 {
-	req = crypto_rfc4543_crypt(req, 0);
+	int err;
+
+	if (req->src != req->dst) {
+		err = crypto_rfc4543_copy_src_to_dst(req, false);
+		if (err)
+			return err;
+	}
+
+	req = crypto_rfc4543_crypt(req, false);
 
 	return crypto_aead_decrypt(req);
 }
@@ -1175,16 +1208,25 @@ static int crypto_rfc4543_decrypt(struct aead_request *req)
 static int crypto_rfc4543_init_tfm(struct crypto_tfm *tfm)
 {
 	struct crypto_instance *inst = (void *)tfm->__crt_alg;
-	struct crypto_aead_spawn *spawn = crypto_instance_ctx(inst);
+	struct crypto_rfc4543_instance_ctx *ictx = crypto_instance_ctx(inst);
+	struct crypto_aead_spawn *spawn = &ictx->aead;
 	struct crypto_rfc4543_ctx *ctx = crypto_tfm_ctx(tfm);
 	struct crypto_aead *aead;
+	struct crypto_blkcipher *null;
 	unsigned long align;
+	int err = 0;
 
 	aead = crypto_spawn_aead(spawn);
 	if (IS_ERR(aead))
 		return PTR_ERR(aead);
 
+	null = crypto_spawn_blkcipher(&ictx->null.base);
+	err = PTR_ERR(null);
+	if (IS_ERR(null))
+		goto err_free_aead;
+
 	ctx->child = aead;
+	ctx->null = null;
 
 	align = crypto_aead_alignmask(aead);
 	align &= ~(crypto_tfm_ctx_alignment() - 1);
@@ -1194,6 +1236,10 @@ static int crypto_rfc4543_init_tfm(struct crypto_tfm *tfm)
 				align + 16;
 
 	return 0;
+
+err_free_aead:
+	crypto_free_aead(aead);
+	return err;
 }
 
 static void crypto_rfc4543_exit_tfm(struct crypto_tfm *tfm)
@@ -1201,6 +1247,7 @@ static void crypto_rfc4543_exit_tfm(struct crypto_tfm *tfm)
 	struct crypto_rfc4543_ctx *ctx = crypto_tfm_ctx(tfm);
 
 	crypto_free_aead(ctx->child);
+	crypto_free_blkcipher(ctx->null);
 }
 
 static struct crypto_instance *crypto_rfc4543_alloc(struct rtattr **tb)
@@ -1209,6 +1256,7 @@ static struct crypto_instance *crypto_rfc4543_alloc(struct rtattr **tb)
 	struct crypto_instance *inst;
 	struct crypto_aead_spawn *spawn;
 	struct crypto_alg *alg;
+	struct crypto_rfc4543_instance_ctx *ctx;
 	const char *ccm_name;
 	int err;
 
@@ -1223,11 +1271,12 @@ static struct crypto_instance *crypto_rfc4543_alloc(struct rtattr **tb)
 	if (IS_ERR(ccm_name))
 		return ERR_CAST(ccm_name);
 
-	inst = kzalloc(sizeof(*inst) + sizeof(*spawn), GFP_KERNEL);
+	inst = kzalloc(sizeof(*inst) + sizeof(*ctx), GFP_KERNEL);
 	if (!inst)
 		return ERR_PTR(-ENOMEM);
 
-	spawn = crypto_instance_ctx(inst);
+	ctx = crypto_instance_ctx(inst);
+	spawn = &ctx->aead;
 	crypto_set_aead_spawn(spawn, inst);
 	err = crypto_grab_aead(spawn, ccm_name, 0,
 			       crypto_requires_sync(algt->type, algt->mask));
@@ -1236,15 +1285,23 @@ static struct crypto_instance *crypto_rfc4543_alloc(struct rtattr **tb)
 
 	alg = crypto_aead_spawn_alg(spawn);
 
+	crypto_set_skcipher_spawn(&ctx->null, inst);
+	err = crypto_grab_skcipher(&ctx->null, "ecb(cipher_null)", 0,
+				   CRYPTO_ALG_ASYNC);
+	if (err)
+		goto out_drop_alg;
+
+	crypto_skcipher_spawn_alg(&ctx->null);
+
 	err = -EINVAL;
 
 	/* We only support 16-byte blocks. */
 	if (alg->cra_aead.ivsize != 16)
-		goto out_drop_alg;
+		goto out_drop_ecbnull;
 
 	/* Not a stream cipher? */
 	if (alg->cra_blocksize != 1)
-		goto out_drop_alg;
+		goto out_drop_ecbnull;
 
 	err = -ENAMETOOLONG;
 	if (snprintf(inst->alg.cra_name, CRYPTO_MAX_ALG_NAME,
@@ -1252,7 +1309,7 @@ static struct crypto_instance *crypto_rfc4543_alloc(struct rtattr **tb)
 	    snprintf(inst->alg.cra_driver_name, CRYPTO_MAX_ALG_NAME,
 		     "rfc4543(%s)", alg->cra_driver_name) >=
 	    CRYPTO_MAX_ALG_NAME)
-		goto out_drop_alg;
+		goto out_drop_ecbnull;
 
 	inst->alg.cra_flags = CRYPTO_ALG_TYPE_AEAD;
 	inst->alg.cra_flags |= alg->cra_flags & CRYPTO_ALG_ASYNC;
@@ -1279,6 +1336,8 @@ static struct crypto_instance *crypto_rfc4543_alloc(struct rtattr **tb)
 out:
 	return inst;
 
+out_drop_ecbnull:
+	crypto_drop_skcipher(&ctx->null);
 out_drop_alg:
 	crypto_drop_aead(spawn);
 out_free_inst:
@@ -1289,7 +1348,11 @@ static struct crypto_instance *crypto_rfc4543_alloc(struct rtattr **tb)
 
 static void crypto_rfc4543_free(struct crypto_instance *inst)
 {
-	crypto_drop_spawn(crypto_instance_ctx(inst));
+	struct crypto_rfc4543_instance_ctx *ctx = crypto_instance_ctx(inst);
+
+	crypto_drop_aead(&ctx->aead);
+	crypto_drop_skcipher(&ctx->null);
+
 	kfree(inst);
 }