crypto: ccm - switch to separate cbcmac driver

Update the generic CCM driver to defer CBC-MAC processing to a
dedicated CBC-MAC ahash transform rather than open coding this
transform (and much of the associated scatterwalk plumbing) in
the CCM driver itself.

This cleans up the code considerably, but more importantly, it allows
the use of alternative CBC-MAC implementations that don't suffer from
performance degradation due to significant setup time (e.g., the NEON
based AES code needs to enable/disable the NEON, and load the S-box
into 16 SIMD registers, which cannot be amortized over the entire input
when using the cipher interface)
Signed-off-by: NArd Biesheuvel <ard.biesheuvel@linaro.org>
Signed-off-by: NHerbert Xu <herbert@gondor.apana.org.au>

crypto/Kconfig

@@ -263,6 +263,7 @@ comment "Authenticated Encryption with Associated Data"
 config CRYPTO_CCM
 	tristate "CCM support"
 	select CRYPTO_CTR
+	select CRYPTO_HASH
 	select CRYPTO_AEAD
 	help
 	  Support for Counter with CBC MAC. Required for IPsec.

crypto/ccm.c

@@ -11,6 +11,7 @@
  */
 
 #include <crypto/internal/aead.h>
+#include <crypto/internal/hash.h>
 #include <crypto/internal/skcipher.h>
 #include <crypto/scatterwalk.h>
 #include <linux/err.h>
@@ -23,11 +24,11 @@
 
 struct ccm_instance_ctx {
 	struct crypto_skcipher_spawn ctr;
-	struct crypto_spawn cipher;
+	struct crypto_ahash_spawn mac;
 };
 
 struct crypto_ccm_ctx {
-	struct crypto_cipher *cipher;
+	struct crypto_ahash *mac;
 	struct crypto_skcipher *ctr;
 };
 
@@ -44,15 +45,22 @@ struct crypto_rfc4309_req_ctx {
 
 struct crypto_ccm_req_priv_ctx {
 	u8 odata[16];
-	u8 idata[16];
 	u8 auth_tag[16];
-	u32 ilen;
 	u32 flags;
 	struct scatterlist src[3];
 	struct scatterlist dst[3];
 	struct skcipher_request skreq;
 };
 
+struct cbcmac_tfm_ctx {
+	struct crypto_cipher *child;
+};
+
+struct cbcmac_desc_ctx {
+	unsigned int len;
+	u8 dg[];
+};
+
 static inline struct crypto_ccm_req_priv_ctx *crypto_ccm_reqctx(
 	struct aead_request *req)
 {
@@ -84,7 +92,7 @@ static int crypto_ccm_setkey(struct crypto_aead *aead, const u8 *key,
 {
 	struct crypto_ccm_ctx *ctx = crypto_aead_ctx(aead);
 	struct crypto_skcipher *ctr = ctx->ctr;
-	struct crypto_cipher *tfm = ctx->cipher;
+	struct crypto_ahash *mac = ctx->mac;
 	int err = 0;
 
 	crypto_skcipher_clear_flags(ctr, CRYPTO_TFM_REQ_MASK);
@@ -96,11 +104,11 @@ static int crypto_ccm_setkey(struct crypto_aead *aead, const u8 *key,
 	if (err)
 		goto out;
 
-	crypto_cipher_clear_flags(tfm, CRYPTO_TFM_REQ_MASK);
-	crypto_cipher_set_flags(tfm, crypto_aead_get_flags(aead) &
+	crypto_ahash_clear_flags(mac, CRYPTO_TFM_REQ_MASK);
+	crypto_ahash_set_flags(mac, crypto_aead_get_flags(aead) &
 				    CRYPTO_TFM_REQ_MASK);
-	err = crypto_cipher_setkey(tfm, key, keylen);
-	crypto_aead_set_flags(aead, crypto_cipher_get_flags(tfm) &
+	err = crypto_ahash_setkey(mac, key, keylen);
+	crypto_aead_set_flags(aead, crypto_ahash_get_flags(mac) &
 			      CRYPTO_TFM_RES_MASK);
 
 out:
@@ -167,119 +175,61 @@ static int format_adata(u8 *adata, unsigned int a)
 	return len;
 }
 
-static void compute_mac(struct crypto_cipher *tfm, u8 *data, int n,
-		       struct crypto_ccm_req_priv_ctx *pctx)
-{
-	unsigned int bs = 16;
-	u8 *odata = pctx->odata;
-	u8 *idata = pctx->idata;
-	int datalen, getlen;
-
-	datalen = n;
-
-	/* first time in here, block may be partially filled. */
-	getlen = bs - pctx->ilen;
-	if (datalen >= getlen) {
-		memcpy(idata + pctx->ilen, data, getlen);
-		crypto_xor(odata, idata, bs);
-		crypto_cipher_encrypt_one(tfm, odata, odata);
-		datalen -= getlen;
-		data += getlen;
-		pctx->ilen = 0;
-	}
-
-	/* now encrypt rest of data */
-	while (datalen >= bs) {
-		crypto_xor(odata, data, bs);
-		crypto_cipher_encrypt_one(tfm, odata, odata);
-
-		datalen -= bs;
-		data += bs;
-	}
-
-	/* check and see if there's leftover data that wasn't
-	 * enough to fill a block.
-	 */
-	if (datalen) {
-		memcpy(idata + pctx->ilen, data, datalen);
-		pctx->ilen += datalen;
-	}
-}
-
-static void get_data_to_compute(struct crypto_cipher *tfm,
-			       struct crypto_ccm_req_priv_ctx *pctx,
-			       struct scatterlist *sg, unsigned int len)
-{
-	struct scatter_walk walk;
-	u8 *data_src;
-	int n;
-
-	scatterwalk_start(&walk, sg);
-
-	while (len) {
-		n = scatterwalk_clamp(&walk, len);
-		if (!n) {
-			scatterwalk_start(&walk, sg_next(walk.sg));
-			n = scatterwalk_clamp(&walk, len);
-		}
-		data_src = scatterwalk_map(&walk);
-
-		compute_mac(tfm, data_src, n, pctx);
-		len -= n;
-
-		scatterwalk_unmap(data_src);
-		scatterwalk_advance(&walk, n);
-		scatterwalk_done(&walk, 0, len);
-		if (len)
-			crypto_yield(pctx->flags);
-	}
-
-	/* any leftover needs padding and then encrypted */
-	if (pctx->ilen) {
-		int padlen;
-		u8 *odata = pctx->odata;
-		u8 *idata = pctx->idata;
-
-		padlen = 16 - pctx->ilen;
-		memset(idata + pctx->ilen, 0, padlen);
-		crypto_xor(odata, idata, 16);
-		crypto_cipher_encrypt_one(tfm, odata, odata);
-		pctx->ilen = 0;
-	}
-}
-
 static int crypto_ccm_auth(struct aead_request *req, struct scatterlist *plain,
 			   unsigned int cryptlen)
 {
+	struct crypto_ccm_req_priv_ctx *pctx = crypto_ccm_reqctx(req);
 	struct crypto_aead *aead = crypto_aead_reqtfm(req);
 	struct crypto_ccm_ctx *ctx = crypto_aead_ctx(aead);
-	struct crypto_ccm_req_priv_ctx *pctx = crypto_ccm_reqctx(req);
-	struct crypto_cipher *cipher = ctx->cipher;
+	AHASH_REQUEST_ON_STACK(ahreq, ctx->mac);
 	unsigned int assoclen = req->assoclen;
-	u8 *odata = pctx->odata;
-	u8 *idata = pctx->idata;
-	int err;
+	struct scatterlist sg[3];
+	u8 odata[16];
+	u8 idata[16];
+	int ilen, err;
 
 	/* format control data for input */
 	err = format_input(odata, req, cryptlen);
 	if (err)
 		goto out;
 
-	/* encrypt first block to use as start in computing mac  */
-	crypto_cipher_encrypt_one(cipher, odata, odata);
+	sg_init_table(sg, 3);
+	sg_set_buf(&sg[0], odata, 16);
 
 	/* format associated data and compute into mac */
 	if (assoclen) {
-		pctx->ilen = format_adata(idata, assoclen);
-		get_data_to_compute(cipher, pctx, req->src, req->assoclen);
+		ilen = format_adata(idata, assoclen);
+		sg_set_buf(&sg[1], idata, ilen);
+		sg_chain(sg, 3, req->src);
 	} else {
-		pctx->ilen = 0;
+		ilen = 0;
+		sg_chain(sg, 2, req->src);
 	}
 
-	/* compute plaintext into mac */
-	if (cryptlen)
-		get_data_to_compute(cipher, pctx, plain, cryptlen);
+	ahash_request_set_tfm(ahreq, ctx->mac);
+	ahash_request_set_callback(ahreq, pctx->flags, NULL, NULL);
+	ahash_request_set_crypt(ahreq, sg, NULL, assoclen + ilen + 16);
+	err = crypto_ahash_init(ahreq);
+	if (err)
+		goto out;
+	err = crypto_ahash_update(ahreq);
+	if (err)
+		goto out;
 
+	/* we need to pad the MAC input to a round multiple of the block size */
+	ilen = 16 - (assoclen + ilen) % 16;
+	if (ilen < 16) {
+		memset(idata, 0, ilen);
+		sg_init_table(sg, 2);
+		sg_set_buf(&sg[0], idata, ilen);
+		if (plain)
+			sg_chain(sg, 2, plain);
+		plain = sg;
+		cryptlen += ilen;
+	}
+
+	ahash_request_set_crypt(ahreq, plain, pctx->odata, cryptlen);
+	err = crypto_ahash_finup(ahreq);
 out:
 	return err;
 }
@@ -453,21 +403,21 @@ static int crypto_ccm_init_tfm(struct crypto_aead *tfm)
 	struct aead_instance *inst = aead_alg_instance(tfm);
 	struct ccm_instance_ctx *ictx = aead_instance_ctx(inst);
 	struct crypto_ccm_ctx *ctx = crypto_aead_ctx(tfm);
-	struct crypto_cipher *cipher;
+	struct crypto_ahash *mac;
 	struct crypto_skcipher *ctr;
 	unsigned long align;
 	int err;
 
-	cipher = crypto_spawn_cipher(&ictx->cipher);
-	if (IS_ERR(cipher))
-		return PTR_ERR(cipher);
+	mac = crypto_spawn_ahash(&ictx->mac);
+	if (IS_ERR(mac))
+		return PTR_ERR(mac);
 
 	ctr = crypto_spawn_skcipher(&ictx->ctr);
 	err = PTR_ERR(ctr);
 	if (IS_ERR(ctr))
-		goto err_free_cipher;
+		goto err_free_mac;
 
-	ctx->cipher = cipher;
+	ctx->mac = mac;
 	ctx->ctr = ctr;
 
 	align = crypto_aead_alignmask(tfm);
@@ -479,8 +429,8 @@ static int crypto_ccm_init_tfm(struct crypto_aead *tfm)
 
 	return 0;
 
-err_free_cipher:
-	crypto_free_cipher(cipher);
+err_free_mac:
+	crypto_free_ahash(mac);
 	return err;
 }
 
@@ -488,7 +438,7 @@ static void crypto_ccm_exit_tfm(struct crypto_aead *tfm)
 {
 	struct crypto_ccm_ctx *ctx = crypto_aead_ctx(tfm);
 
-	crypto_free_cipher(ctx->cipher);
+	crypto_free_ahash(ctx->mac);
 	crypto_free_skcipher(ctx->ctr);
 }
 
@@ -496,7 +446,7 @@ static void crypto_ccm_free(struct aead_instance *inst)
 {
 	struct ccm_instance_ctx *ctx = aead_instance_ctx(inst);
 
-	crypto_drop_spawn(&ctx->cipher);
+	crypto_drop_ahash(&ctx->mac);
 	crypto_drop_skcipher(&ctx->ctr);
 	kfree(inst);
 }
@@ -505,12 +455,13 @@ static int crypto_ccm_create_common(struct crypto_template *tmpl,
 				    struct rtattr **tb,
 				    const char *full_name,
 				    const char *ctr_name,
-				    const char *cipher_name)
+				    const char *mac_name)
 {
 	struct crypto_attr_type *algt;
 	struct aead_instance *inst;
 	struct skcipher_alg *ctr;
-	struct crypto_alg *cipher;
+	struct crypto_alg *mac_alg;
+	struct hash_alg_common *mac;
 	struct ccm_instance_ctx *ictx;
 	int err;
 
@@ -521,25 +472,26 @@ static int crypto_ccm_create_common(struct crypto_template *tmpl,
 	if ((algt->type ^ CRYPTO_ALG_TYPE_AEAD) & algt->mask)
 		return -EINVAL;
 
-	cipher = crypto_alg_mod_lookup(cipher_name,  CRYPTO_ALG_TYPE_CIPHER,
-				       CRYPTO_ALG_TYPE_MASK);
-	if (IS_ERR(cipher))
-		return PTR_ERR(cipher);
+	mac_alg = crypto_find_alg(mac_name, &crypto_ahash_type,
+				  CRYPTO_ALG_TYPE_HASH,
+				  CRYPTO_ALG_TYPE_AHASH_MASK |
+				  CRYPTO_ALG_ASYNC);
+	if (IS_ERR(mac_alg))
+		return PTR_ERR(mac_alg);
 
+	mac = __crypto_hash_alg_common(mac_alg);
 	err = -EINVAL;
-	if (cipher->cra_blocksize != 16)
-		goto out_put_cipher;
+	if (mac->digestsize != 16)
+		goto out_put_mac;
 
 	inst = kzalloc(sizeof(*inst) + sizeof(*ictx), GFP_KERNEL);
 	err = -ENOMEM;
 	if (!inst)
-		goto out_put_cipher;
+		goto out_put_mac;
 
 	ictx = aead_instance_ctx(inst);
-
-	err = crypto_init_spawn(&ictx->cipher, cipher,
-				aead_crypto_instance(inst),
-				CRYPTO_ALG_TYPE_MASK);
+	err = crypto_init_ahash_spawn(&ictx->mac, mac,
+				      aead_crypto_instance(inst));
 	if (err)
 		goto err_free_inst;
 
@@ -548,7 +500,7 @@ static int crypto_ccm_create_common(struct crypto_template *tmpl,
 				   crypto_requires_sync(algt->type,
 							algt->mask));
 	if (err)
-		goto err_drop_cipher;
+		goto err_drop_mac;
 
 	ctr = crypto_spawn_skcipher_alg(&ictx->ctr);
 
@@ -564,16 +516,16 @@ static int crypto_ccm_create_common(struct crypto_template *tmpl,
 	err = -ENAMETOOLONG;
 	if (snprintf(inst->alg.base.cra_driver_name, CRYPTO_MAX_ALG_NAME,
 		     "ccm_base(%s,%s)", ctr->base.cra_driver_name,
-		     cipher->cra_driver_name) >= CRYPTO_MAX_ALG_NAME)
+		     mac->base.cra_driver_name) >= CRYPTO_MAX_ALG_NAME)
 		goto err_drop_ctr;
 
 	memcpy(inst->alg.base.cra_name, full_name, CRYPTO_MAX_ALG_NAME);
 
 	inst->alg.base.cra_flags = ctr->base.cra_flags & CRYPTO_ALG_ASYNC;
-	inst->alg.base.cra_priority = (cipher->cra_priority +
+	inst->alg.base.cra_priority = (mac->base.cra_priority +
 				       ctr->base.cra_priority) / 2;
 	inst->alg.base.cra_blocksize = 1;
-	inst->alg.base.cra_alignmask = cipher->cra_alignmask |
+	inst->alg.base.cra_alignmask = mac->base.cra_alignmask |
 				       ctr->base.cra_alignmask |
 				       (__alignof__(u32) - 1);
 	inst->alg.ivsize = 16;
@@ -593,23 +545,24 @@ static int crypto_ccm_create_common(struct crypto_template *tmpl,
 	if (err)
 		goto err_drop_ctr;
 
-out_put_cipher:
-	crypto_mod_put(cipher);
+out_put_mac:
+	crypto_mod_put(mac_alg);
 	return err;
 
 err_drop_ctr:
 	crypto_drop_skcipher(&ictx->ctr);
-err_drop_cipher:
-	crypto_drop_spawn(&ictx->cipher);
+err_drop_mac:
+	crypto_drop_ahash(&ictx->mac);
 err_free_inst:
 	kfree(inst);
-	goto out_put_cipher;
+	goto out_put_mac;
 }
 
 static int crypto_ccm_create(struct crypto_template *tmpl, struct rtattr **tb)
 {
 	const char *cipher_name;
 	char ctr_name[CRYPTO_MAX_ALG_NAME];
+	char mac_name[CRYPTO_MAX_ALG_NAME];
 	char full_name[CRYPTO_MAX_ALG_NAME];
 
 	cipher_name = crypto_attr_alg_name(tb[1]);
@@ -620,12 +573,16 @@ static int crypto_ccm_create(struct crypto_template *tmpl, struct rtattr **tb)
 		     cipher_name) >= CRYPTO_MAX_ALG_NAME)
 		return -ENAMETOOLONG;
 
+	if (snprintf(mac_name, CRYPTO_MAX_ALG_NAME, "cbcmac(%s)",
+		     cipher_name) >= CRYPTO_MAX_ALG_NAME)
+		return -ENAMETOOLONG;
+
 	if (snprintf(full_name, CRYPTO_MAX_ALG_NAME, "ccm(%s)", cipher_name) >=
 	    CRYPTO_MAX_ALG_NAME)
 		return -ENAMETOOLONG;
 
 	return crypto_ccm_create_common(tmpl, tb, full_name, ctr_name,
-					cipher_name);
+					mac_name);
 }
 
 static struct crypto_template crypto_ccm_tmpl = {
@@ -899,14 +856,161 @@ static struct crypto_template crypto_rfc4309_tmpl = {
 	.module = THIS_MODULE,
 };
 
+static int crypto_cbcmac_digest_setkey(struct crypto_shash *parent,
+				     const u8 *inkey, unsigned int keylen)
+{
+	struct cbcmac_tfm_ctx *ctx = crypto_shash_ctx(parent);
+
+	return crypto_cipher_setkey(ctx->child, inkey, keylen);
+}
+
+static int crypto_cbcmac_digest_init(struct shash_desc *pdesc)
+{
+	struct cbcmac_desc_ctx *ctx = shash_desc_ctx(pdesc);
+	int bs = crypto_shash_digestsize(pdesc->tfm);
+
+	ctx->len = 0;
+	memset(ctx->dg, 0, bs);
+
+	return 0;
+}
+
+static int crypto_cbcmac_digest_update(struct shash_desc *pdesc, const u8 *p,
+				       unsigned int len)
+{
+	struct crypto_shash *parent = pdesc->tfm;
+	struct cbcmac_tfm_ctx *tctx = crypto_shash_ctx(parent);
+	struct cbcmac_desc_ctx *ctx = shash_desc_ctx(pdesc);
+	struct crypto_cipher *tfm = tctx->child;
+	int bs = crypto_shash_digestsize(parent);
+
+	while (len > 0) {
+		unsigned int l = min(len, bs - ctx->len);
+
+		crypto_xor(ctx->dg + ctx->len, p, l);
+		ctx->len +=l;
+		len -= l;
+		p += l;
+
+		if (ctx->len == bs) {
+			crypto_cipher_encrypt_one(tfm, ctx->dg, ctx->dg);
+			ctx->len = 0;
+		}
+	}
+
+	return 0;
+}
+
+static int crypto_cbcmac_digest_final(struct shash_desc *pdesc, u8 *out)
+{
+	struct crypto_shash *parent = pdesc->tfm;
+	struct cbcmac_tfm_ctx *tctx = crypto_shash_ctx(parent);
+	struct cbcmac_desc_ctx *ctx = shash_desc_ctx(pdesc);
+	struct crypto_cipher *tfm = tctx->child;
+	int bs = crypto_shash_digestsize(parent);
+
+	if (ctx->len)
+		crypto_cipher_encrypt_one(tfm, out, ctx->dg);
+	else
+		memcpy(out, ctx->dg, bs);
+
+	return 0;
+}
+
+static int cbcmac_init_tfm(struct crypto_tfm *tfm)
+{
+	struct crypto_cipher *cipher;
+	struct crypto_instance *inst = (void *)tfm->__crt_alg;
+	struct crypto_spawn *spawn = crypto_instance_ctx(inst);
+	struct cbcmac_tfm_ctx *ctx = crypto_tfm_ctx(tfm);
+
+	cipher = crypto_spawn_cipher(spawn);
+	if (IS_ERR(cipher))
+		return PTR_ERR(cipher);
+
+	ctx->child = cipher;
+
+	return 0;
+};
+
+static void cbcmac_exit_tfm(struct crypto_tfm *tfm)
+{
+	struct cbcmac_tfm_ctx *ctx = crypto_tfm_ctx(tfm);
+	crypto_free_cipher(ctx->child);
+}
+
+static int cbcmac_create(struct crypto_template *tmpl, struct rtattr **tb)
+{
+	struct shash_instance *inst;
+	struct crypto_alg *alg;
+	int err;
+
+	err = crypto_check_attr_type(tb, CRYPTO_ALG_TYPE_SHASH);
+	if (err)
+		return err;
+
+	alg = crypto_get_attr_alg(tb, CRYPTO_ALG_TYPE_CIPHER,
+				  CRYPTO_ALG_TYPE_MASK);
+	if (IS_ERR(alg))
+		return PTR_ERR(alg);
+
+	inst = shash_alloc_instance("cbcmac", alg);
+	err = PTR_ERR(inst);
+	if (IS_ERR(inst))
+		goto out_put_alg;
+
+	err = crypto_init_spawn(shash_instance_ctx(inst), alg,
+				shash_crypto_instance(inst),
+				CRYPTO_ALG_TYPE_MASK);
+	if (err)
+		goto out_free_inst;
+
+	inst->alg.base.cra_priority = alg->cra_priority;
+	inst->alg.base.cra_blocksize = 1;
+
+	inst->alg.digestsize = alg->cra_blocksize;
+	inst->alg.descsize = sizeof(struct cbcmac_desc_ctx) +
+			     alg->cra_blocksize;
+
+	inst->alg.base.cra_ctxsize = sizeof(struct cbcmac_tfm_ctx);
+	inst->alg.base.cra_init = cbcmac_init_tfm;
+	inst->alg.base.cra_exit = cbcmac_exit_tfm;
+
+	inst->alg.init = crypto_cbcmac_digest_init;
+	inst->alg.update = crypto_cbcmac_digest_update;
+	inst->alg.final = crypto_cbcmac_digest_final;
+	inst->alg.setkey = crypto_cbcmac_digest_setkey;
+
+	err = shash_register_instance(tmpl, inst);
+
+out_free_inst:
+	if (err)
+		shash_free_instance(shash_crypto_instance(inst));
+
+out_put_alg:
+	crypto_mod_put(alg);
+	return err;
+}
+
+static struct crypto_template crypto_cbcmac_tmpl = {
+	.name = "cbcmac",
+	.create = cbcmac_create,
+	.free = shash_free_instance,
+	.module = THIS_MODULE,
+};
+
 static int __init crypto_ccm_module_init(void)
 {
 	int err;
 
-	err = crypto_register_template(&crypto_ccm_base_tmpl);
+	err = crypto_register_template(&crypto_cbcmac_tmpl);
 	if (err)
 		goto out;
 
+	err = crypto_register_template(&crypto_ccm_base_tmpl);
+	if (err)
+		goto out_undo_cbcmac;
+
 	err = crypto_register_template(&crypto_ccm_tmpl);
 	if (err)
 		goto out_undo_base;
@@ -922,6 +1026,8 @@ static int __init crypto_ccm_module_init(void)
 	crypto_unregister_template(&crypto_ccm_tmpl);
 out_undo_base:
 	crypto_unregister_template(&crypto_ccm_base_tmpl);
+out_undo_cbcmac:
+	crypto_register_template(&crypto_cbcmac_tmpl);
 	goto out;
 }
 
@@ -930,6 +1036,7 @@ static void __exit crypto_ccm_module_exit(void)
 	crypto_unregister_template(&crypto_rfc4309_tmpl);
 	crypto_unregister_template(&crypto_ccm_tmpl);
 	crypto_unregister_template(&crypto_ccm_base_tmpl);
+	crypto_unregister_template(&crypto_cbcmac_tmpl);
 }
 
 module_init(crypto_ccm_module_init);