crypto: chacha20poly1305 - Add a ChaCha20-Poly1305 AEAD construction, RFC7539

This AEAD uses a chacha20 ablkcipher and a poly1305 ahash to construct the
ChaCha20-Poly1305 AEAD as defined in RFC7539. It supports both synchronous and
asynchronous operations, even if we currently have no async chacha20 or poly1305
drivers.

Signed-off-by: Martin Willi <martin@strongswan.org>
Acked-by: Steffen Klassert <steffen.klassert@secunet.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>

3 files changed, 676 insertions, 0 deletions

diff --git a/crypto/Kconfig b/crypto/Kconfig
index 9c00454ed024..1bc7e0b85b5d 100644
--- a/crypto/Kconfig
+++ b/crypto/Kconfig
@@ -217,6 +217,18 @@ config CRYPTO_GCM
 	  Support for Galois/Counter Mode (GCM) and Galois Message
 	  Authentication Code (GMAC). Required for IPSec.
 
+config CRYPTO_CHACHA20POLY1305
+	tristate "ChaCha20-Poly1305 AEAD support"
+	select CRYPTO_CHACHA20
+	select CRYPTO_POLY1305
+	select CRYPTO_AEAD
+	help
+	  ChaCha20-Poly1305 AEAD support, RFC7539.
+
+	  Support for the AEAD wrapper using the ChaCha20 stream cipher combined
+	  with the Poly1305 authenticator. It is defined in RFC7539 for use in
+	  IETF protocols.
+
 config CRYPTO_SEQIV
 	tristate "Sequence Number IV Generator"
 	select CRYPTO_AEAD
diff --git a/crypto/Makefile b/crypto/Makefile
index 2424c81d69bc..e6cf6a5426ab 100644
--- a/crypto/Makefile
+++ b/crypto/Makefile
@@ -59,6 +59,7 @@ obj-$(CONFIG_CRYPTO_XTS) += xts.o
 obj-$(CONFIG_CRYPTO_CTR) += ctr.o
 obj-$(CONFIG_CRYPTO_GCM) += gcm.o
 obj-$(CONFIG_CRYPTO_CCM) += ccm.o
+obj-$(CONFIG_CRYPTO_CHACHA20POLY1305) += chacha20poly1305.o
 obj-$(CONFIG_CRYPTO_PCRYPT) += pcrypt.o
 obj-$(CONFIG_CRYPTO_CRYPTD) += cryptd.o
 obj-$(CONFIG_CRYPTO_MCRYPTD) += mcryptd.o
diff --git a/crypto/chacha20poly1305.c b/crypto/chacha20poly1305.c
new file mode 100644
index 000000000000..6171cf14c5f5
--- /dev/null
+++ b/crypto/chacha20poly1305.c
@@ -0,0 +1,663 @@
+/*
+ * ChaCha20-Poly1305 AEAD, RFC7539
+ *
+ * Copyright (C) 2015 Martin Willi
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ */
+
+#include <crypto/internal/aead.h>
+#include <crypto/internal/hash.h>
+#include <crypto/internal/skcipher.h>
+#include <crypto/scatterwalk.h>
+#include <linux/err.h>
+#include <linux/init.h>
+#include <linux/kernel.h>
+#include <linux/module.h>
+
+#include "internal.h"
+
+#define POLY1305_BLOCK_SIZE	16
+#define POLY1305_DIGEST_SIZE	16
+#define POLY1305_KEY_SIZE	32
+#define CHACHA20_KEY_SIZE	32
+#define CHACHA20_IV_SIZE	16
+#define CHACHAPOLY_IV_SIZE	12
+
+struct chachapoly_instance_ctx {
+	struct crypto_skcipher_spawn chacha;
+	struct crypto_ahash_spawn poly;
+	unsigned int saltlen;
+};
+
+struct chachapoly_ctx {
+	struct crypto_ablkcipher *chacha;
+	struct crypto_ahash *poly;
+	/* key bytes we use for the ChaCha20 IV */
+	unsigned int saltlen;
+	u8 salt[];
+};
+
+struct poly_req {
+	/* zero byte padding for AD/ciphertext, as needed */
+	u8 pad[POLY1305_BLOCK_SIZE];
+	/* tail data with AD/ciphertext lengths */
+	struct {
+		__le64 assoclen;
+		__le64 cryptlen;
+	} tail;
+	struct scatterlist src[1];
+	struct ahash_request req; /* must be last member */
+};
+
+struct chacha_req {
+	/* the key we generate for Poly1305 using Chacha20 */
+	u8 key[POLY1305_KEY_SIZE];
+	u8 iv[CHACHA20_IV_SIZE];
+	struct scatterlist src[1];
+	struct ablkcipher_request req; /* must be last member */
+};
+
+struct chachapoly_req_ctx {
+	/* calculated Poly1305 tag */
+	u8 tag[POLY1305_DIGEST_SIZE];
+	/* length of data to en/decrypt, without ICV */
+	unsigned int cryptlen;
+	union {
+		struct poly_req poly;
+		struct chacha_req chacha;
+	} u;
+};
+
+static inline void async_done_continue(struct aead_request *req, int err,
+				       int (*cont)(struct aead_request *))
+{
+	if (!err)
+		err = cont(req);
+
+	if (err != -EINPROGRESS && err != -EBUSY)
+		aead_request_complete(req, err);
+}
+
+static void chacha_iv(u8 *iv, struct aead_request *req, u32 icb)
+{
+	struct chachapoly_ctx *ctx = crypto_aead_ctx(crypto_aead_reqtfm(req));
+	__le32 leicb = cpu_to_le32(icb);
+
+	memcpy(iv, &leicb, sizeof(leicb));
+	memcpy(iv + sizeof(leicb), ctx->salt, ctx->saltlen);
+	memcpy(iv + sizeof(leicb) + ctx->saltlen, req->iv,
+	       CHACHA20_IV_SIZE - sizeof(leicb) - ctx->saltlen);
+}
+
+static int poly_verify_tag(struct aead_request *req)
+{
+	struct chachapoly_req_ctx *rctx = aead_request_ctx(req);
+	u8 tag[sizeof(rctx->tag)];
+
+	scatterwalk_map_and_copy(tag, req->src, rctx->cryptlen, sizeof(tag), 0);
+	if (crypto_memneq(tag, rctx->tag, sizeof(tag)))
+		return -EBADMSG;
+	return 0;
+}
+
+static int poly_copy_tag(struct aead_request *req)
+{
+	struct chachapoly_req_ctx *rctx = aead_request_ctx(req);
+
+	scatterwalk_map_and_copy(rctx->tag, req->dst, rctx->cryptlen,
+				 sizeof(rctx->tag), 1);
+	return 0;
+}
+
+static void chacha_decrypt_done(struct crypto_async_request *areq, int err)
+{
+	async_done_continue(areq->data, err, poly_verify_tag);
+}
+
+static int chacha_decrypt(struct aead_request *req)
+{
+	struct chachapoly_ctx *ctx = crypto_aead_ctx(crypto_aead_reqtfm(req));
+	struct chachapoly_req_ctx *rctx = aead_request_ctx(req);
+	struct chacha_req *creq = &rctx->u.chacha;
+	int err;
+
+	chacha_iv(creq->iv, req, 1);
+
+	ablkcipher_request_set_callback(&creq->req, aead_request_flags(req),
+					chacha_decrypt_done, req);
+	ablkcipher_request_set_tfm(&creq->req, ctx->chacha);
+	ablkcipher_request_set_crypt(&creq->req, req->src, req->dst,
+				     rctx->cryptlen, creq->iv);
+	err = crypto_ablkcipher_decrypt(&creq->req);
+	if (err)
+		return err;
+
+	return poly_verify_tag(req);
+}
+
+static int poly_tail_continue(struct aead_request *req)
+{
+	struct chachapoly_req_ctx *rctx = aead_request_ctx(req);
+
+	if (rctx->cryptlen == req->cryptlen) /* encrypting */
+		return poly_copy_tag(req);
+
+	return chacha_decrypt(req);
+}
+
+static void poly_tail_done(struct crypto_async_request *areq, int err)
+{
+	async_done_continue(areq->data, err, poly_tail_continue);
+}
+
+static int poly_tail(struct aead_request *req)
+{
+	struct chachapoly_ctx *ctx = crypto_aead_ctx(crypto_aead_reqtfm(req));
+	struct chachapoly_req_ctx *rctx = aead_request_ctx(req);
+	struct poly_req *preq = &rctx->u.poly;
+	__le64 len;
+	int err;
+
+	sg_init_table(preq->src, 1);
+	len = cpu_to_le64(req->assoclen);
+	memcpy(&preq->tail.assoclen, &len, sizeof(len));
+	len = cpu_to_le64(rctx->cryptlen);
+	memcpy(&preq->tail.cryptlen, &len, sizeof(len));
+	sg_set_buf(preq->src, &preq->tail, sizeof(preq->tail));
+
+	ahash_request_set_callback(&preq->req, aead_request_flags(req),
+				   poly_tail_done, req);
+	ahash_request_set_tfm(&preq->req, ctx->poly);
+	ahash_request_set_crypt(&preq->req, preq->src,
+				rctx->tag, sizeof(preq->tail));
+
+	err = crypto_ahash_finup(&preq->req);
+	if (err)
+		return err;
+
+	return poly_tail_continue(req);
+}
+
+static void poly_cipherpad_done(struct crypto_async_request *areq, int err)
+{
+	async_done_continue(areq->data, err, poly_tail);
+}
+
+static int poly_cipherpad(struct aead_request *req)
+{
+	struct chachapoly_ctx *ctx = crypto_aead_ctx(crypto_aead_reqtfm(req));
+	struct chachapoly_req_ctx *rctx = aead_request_ctx(req);
+	struct poly_req *preq = &rctx->u.poly;
+	unsigned int padlen, bs = POLY1305_BLOCK_SIZE;
+	int err;
+
+	padlen = (bs - (rctx->cryptlen % bs)) % bs;
+	memset(preq->pad, 0, sizeof(preq->pad));
+	sg_init_table(preq->src, 1);
+	sg_set_buf(preq->src, &preq->pad, padlen);
+
+	ahash_request_set_callback(&preq->req, aead_request_flags(req),
+				   poly_cipherpad_done, req);
+	ahash_request_set_tfm(&preq->req, ctx->poly);
+	ahash_request_set_crypt(&preq->req, preq->src, NULL, padlen);
+
+	err = crypto_ahash_update(&preq->req);
+	if (err)
+		return err;
+
+	return poly_tail(req);
+}
+
+static void poly_cipher_done(struct crypto_async_request *areq, int err)
+{
+	async_done_continue(areq->data, err, poly_cipherpad);
+}
+
+static int poly_cipher(struct aead_request *req)
+{
+	struct chachapoly_ctx *ctx = crypto_aead_ctx(crypto_aead_reqtfm(req));
+	struct chachapoly_req_ctx *rctx = aead_request_ctx(req);
+	struct poly_req *preq = &rctx->u.poly;
+	struct scatterlist *crypt = req->src;
+	int err;
+
+	if (rctx->cryptlen == req->cryptlen) /* encrypting */
+		crypt = req->dst;
+
+	ahash_request_set_callback(&preq->req, aead_request_flags(req),
+				   poly_cipher_done, req);
+	ahash_request_set_tfm(&preq->req, ctx->poly);
+	ahash_request_set_crypt(&preq->req, crypt, NULL, rctx->cryptlen);
+
+	err = crypto_ahash_update(&preq->req);
+	if (err)
+		return err;
+
+	return poly_cipherpad(req);
+}
+
+static void poly_adpad_done(struct crypto_async_request *areq, int err)
+{
+	async_done_continue(areq->data, err, poly_cipher);
+}
+
+static int poly_adpad(struct aead_request *req)
+{
+	struct chachapoly_ctx *ctx = crypto_aead_ctx(crypto_aead_reqtfm(req));
+	struct chachapoly_req_ctx *rctx = aead_request_ctx(req);
+	struct poly_req *preq = &rctx->u.poly;
+	unsigned int padlen, bs = POLY1305_BLOCK_SIZE;
+	int err;
+
+	padlen = (bs - (req->assoclen % bs)) % bs;
+	memset(preq->pad, 0, sizeof(preq->pad));
+	sg_init_table(preq->src, 1);
+	sg_set_buf(preq->src, preq->pad, padlen);
+
+	ahash_request_set_callback(&preq->req, aead_request_flags(req),
+				   poly_adpad_done, req);
+	ahash_request_set_tfm(&preq->req, ctx->poly);
+	ahash_request_set_crypt(&preq->req, preq->src, NULL, padlen);
+
+	err = crypto_ahash_update(&preq->req);
+	if (err)
+		return err;
+
+	return poly_cipher(req);
+}
+
+static void poly_ad_done(struct crypto_async_request *areq, int err)
+{
+	async_done_continue(areq->data, err, poly_adpad);
+}
+
+static int poly_ad(struct aead_request *req)
+{
+	struct chachapoly_ctx *ctx = crypto_aead_ctx(crypto_aead_reqtfm(req));
+	struct chachapoly_req_ctx *rctx = aead_request_ctx(req);
+	struct poly_req *preq = &rctx->u.poly;
+	int err;
+
+	ahash_request_set_callback(&preq->req, aead_request_flags(req),
+				   poly_ad_done, req);
+	ahash_request_set_tfm(&preq->req, ctx->poly);
+	ahash_request_set_crypt(&preq->req, req->assoc, NULL, req->assoclen);
+
+	err = crypto_ahash_update(&preq->req);
+	if (err)
+		return err;
+
+	return poly_adpad(req);
+}
+
+static void poly_init_done(struct crypto_async_request *areq, int err)
+{
+	async_done_continue(areq->data, err, poly_ad);
+}
+
+static int poly_init(struct aead_request *req)
+{
+	struct chachapoly_ctx *ctx = crypto_aead_ctx(crypto_aead_reqtfm(req));
+	struct chachapoly_req_ctx *rctx = aead_request_ctx(req);
+	struct poly_req *preq = &rctx->u.poly;
+	int err;
+
+	ahash_request_set_callback(&preq->req, aead_request_flags(req),
+				   poly_init_done, req);
+	ahash_request_set_tfm(&preq->req, ctx->poly);
+
+	err = crypto_ahash_init(&preq->req);
+	if (err)
+		return err;
+
+	return poly_ad(req);
+}
+
+static int poly_genkey_continue(struct aead_request *req)
+{
+	struct crypto_aead *aead = crypto_aead_reqtfm(req);
+	struct chachapoly_ctx *ctx = crypto_aead_ctx(aead);
+	struct chachapoly_req_ctx *rctx = aead_request_ctx(req);
+	struct chacha_req *creq = &rctx->u.chacha;
+	int err;
+
+	crypto_ahash_clear_flags(ctx->poly, CRYPTO_TFM_REQ_MASK);
+	crypto_ahash_set_flags(ctx->poly, crypto_aead_get_flags(aead) &
+			       CRYPTO_TFM_REQ_MASK);
+
+	err = crypto_ahash_setkey(ctx->poly, creq->key, sizeof(creq->key));
+	crypto_aead_set_flags(aead, crypto_ahash_get_flags(ctx->poly) &
+			      CRYPTO_TFM_RES_MASK);
+	if (err)
+		return err;
+
+	return poly_init(req);
+}
+
+static void poly_genkey_done(struct crypto_async_request *areq, int err)
+{
+	async_done_continue(areq->data, err, poly_genkey_continue);
+}
+
+static int poly_genkey(struct aead_request *req)
+{
+	struct chachapoly_ctx *ctx = crypto_aead_ctx(crypto_aead_reqtfm(req));
+	struct chachapoly_req_ctx *rctx = aead_request_ctx(req);
+	struct chacha_req *creq = &rctx->u.chacha;
+	int err;
+
+	sg_init_table(creq->src, 1);
+	memset(creq->key, 0, sizeof(creq->key));
+	sg_set_buf(creq->src, creq->key, sizeof(creq->key));
+
+	chacha_iv(creq->iv, req, 0);
+
+	ablkcipher_request_set_callback(&creq->req, aead_request_flags(req),
+					poly_genkey_done, req);
+	ablkcipher_request_set_tfm(&creq->req, ctx->chacha);
+	ablkcipher_request_set_crypt(&creq->req, creq->src, creq->src,
+				     POLY1305_KEY_SIZE, creq->iv);
+
+	err = crypto_ablkcipher_decrypt(&creq->req);
+	if (err)
+		return err;
+
+	return poly_genkey_continue(req);
+}
+
+static void chacha_encrypt_done(struct crypto_async_request *areq, int err)
+{
+	async_done_continue(areq->data, err, poly_genkey);
+}
+
+static int chacha_encrypt(struct aead_request *req)
+{
+	struct chachapoly_ctx *ctx = crypto_aead_ctx(crypto_aead_reqtfm(req));
+	struct chachapoly_req_ctx *rctx = aead_request_ctx(req);
+	struct chacha_req *creq = &rctx->u.chacha;
+	int err;
+
+	chacha_iv(creq->iv, req, 1);
+
+	ablkcipher_request_set_callback(&creq->req, aead_request_flags(req),
+					chacha_encrypt_done, req);
+	ablkcipher_request_set_tfm(&creq->req, ctx->chacha);
+	ablkcipher_request_set_crypt(&creq->req, req->src, req->dst,
+				     req->cryptlen, creq->iv);
+	err = crypto_ablkcipher_encrypt(&creq->req);
+	if (err)
+		return err;
+
+	return poly_genkey(req);
+}
+
+static int chachapoly_encrypt(struct aead_request *req)
+{
+	struct chachapoly_req_ctx *rctx = aead_request_ctx(req);
+
+	rctx->cryptlen = req->cryptlen;
+
+	/* encrypt call chain:
+	 * - chacha_encrypt/done()
+	 * - poly_genkey/done/continue()
+	 * - poly_init/done()
+	 * - poly_ad/done()
+	 * - poly_adpad/done()
+	 * - poly_cipher/done()
+	 * - poly_cipherpad/done()
+	 * - poly_tail/done/continue()
+	 * - poly_copy_tag()
+	 */
+	return chacha_encrypt(req);
+}
+
+static int chachapoly_decrypt(struct aead_request *req)
+{
+	struct chachapoly_req_ctx *rctx = aead_request_ctx(req);
+
+	if (req->cryptlen < POLY1305_DIGEST_SIZE)
+		return -EINVAL;
+	rctx->cryptlen = req->cryptlen - POLY1305_DIGEST_SIZE;
+
+	/* decrypt call chain:
+	 * - poly_genkey/done/continue()
+	 * - poly_init/done()
+	 * - poly_ad/done()
+	 * - poly_adpad/done()
+	 * - poly_cipher/done()
+	 * - poly_cipherpad/done()
+	 * - poly_tail/done/continue()
+	 * - chacha_decrypt/done()
+	 * - poly_verify_tag()
+	 */
+	return poly_genkey(req);
+}
+
+static int chachapoly_setkey(struct crypto_aead *aead, const u8 *key,
+			     unsigned int keylen)
+{
+	struct chachapoly_ctx *ctx = crypto_aead_ctx(aead);
+	int err;
+
+	if (keylen != ctx->saltlen + CHACHA20_KEY_SIZE)
+		return -EINVAL;
+
+	keylen -= ctx->saltlen;
+	memcpy(ctx->salt, key + keylen, ctx->saltlen);
+
+	crypto_ablkcipher_clear_flags(ctx->chacha, CRYPTO_TFM_REQ_MASK);
+	crypto_ablkcipher_set_flags(ctx->chacha, crypto_aead_get_flags(aead) &
+				    CRYPTO_TFM_REQ_MASK);
+
+	err = crypto_ablkcipher_setkey(ctx->chacha, key, keylen);
+	crypto_aead_set_flags(aead, crypto_ablkcipher_get_flags(ctx->chacha) &
+			      CRYPTO_TFM_RES_MASK);
+	return err;
+}
+
+static int chachapoly_setauthsize(struct crypto_aead *tfm,
+				  unsigned int authsize)
+{
+	if (authsize != POLY1305_DIGEST_SIZE)
+		return -EINVAL;
+
+	return 0;
+}
+
+static int chachapoly_init(struct crypto_tfm *tfm)
+{
+	struct crypto_instance *inst = (void *)tfm->__crt_alg;
+	struct chachapoly_instance_ctx *ictx = crypto_instance_ctx(inst);
+	struct chachapoly_ctx *ctx = crypto_tfm_ctx(tfm);
+	struct crypto_ablkcipher *chacha;
+	struct crypto_ahash *poly;
+	unsigned long align;
+
+	poly = crypto_spawn_ahash(&ictx->poly);
+	if (IS_ERR(poly))
+		return PTR_ERR(poly);
+
+	chacha = crypto_spawn_skcipher(&ictx->chacha);
+	if (IS_ERR(chacha)) {
+		crypto_free_ahash(poly);
+		return PTR_ERR(chacha);
+	}
+
+	ctx->chacha = chacha;
+	ctx->poly = poly;
+	ctx->saltlen = ictx->saltlen;
+
+	align = crypto_tfm_alg_alignmask(tfm);
+	align &= ~(crypto_tfm_ctx_alignment() - 1);
+	crypto_aead_set_reqsize(__crypto_aead_cast(tfm),
+				align + offsetof(struct chachapoly_req_ctx, u) +
+				max(offsetof(struct chacha_req, req) +
+				    sizeof(struct ablkcipher_request) +
+				    crypto_ablkcipher_reqsize(chacha),
+				    offsetof(struct poly_req, req) +
+				    sizeof(struct ahash_request) +
+				    crypto_ahash_reqsize(poly)));
+
+	return 0;
+}
+
+static void chachapoly_exit(struct crypto_tfm *tfm)
+{
+	struct chachapoly_ctx *ctx = crypto_tfm_ctx(tfm);
+
+	crypto_free_ahash(ctx->poly);
+	crypto_free_ablkcipher(ctx->chacha);
+}
+
+static struct crypto_instance *chachapoly_alloc(struct rtattr **tb,
+						const char *name,
+						unsigned int ivsize)
+{
+	struct crypto_attr_type *algt;
+	struct crypto_instance *inst;
+	struct crypto_alg *chacha;
+	struct crypto_alg *poly;
+	struct ahash_alg *poly_ahash;
+	struct chachapoly_instance_ctx *ctx;
+	const char *chacha_name, *poly_name;
+	int err;
+
+	if (ivsize > CHACHAPOLY_IV_SIZE)
+		return ERR_PTR(-EINVAL);
+
+	algt = crypto_get_attr_type(tb);
+	if (IS_ERR(algt))
+		return ERR_CAST(algt);
+
+	if ((algt->type ^ CRYPTO_ALG_TYPE_AEAD) & algt->mask)
+		return ERR_PTR(-EINVAL);
+
+	chacha_name = crypto_attr_alg_name(tb[1]);
+	if (IS_ERR(chacha_name))
+		return ERR_CAST(chacha_name);
+	poly_name = crypto_attr_alg_name(tb[2]);
+	if (IS_ERR(poly_name))
+		return ERR_CAST(poly_name);
+
+	poly = crypto_find_alg(poly_name, &crypto_ahash_type,
+			       CRYPTO_ALG_TYPE_HASH,
+			       CRYPTO_ALG_TYPE_AHASH_MASK);
+	if (IS_ERR(poly))
+		return ERR_CAST(poly);
+
+	err = -ENOMEM;
+	inst = kzalloc(sizeof(*inst) + sizeof(*ctx), GFP_KERNEL);
+	if (!inst)
+		goto out_put_poly;
+
+	ctx = crypto_instance_ctx(inst);
+	ctx->saltlen = CHACHAPOLY_IV_SIZE - ivsize;
+	poly_ahash = container_of(poly, struct ahash_alg, halg.base);
+	err = crypto_init_ahash_spawn(&ctx->poly, &poly_ahash->halg, inst);
+	if (err)
+		goto err_free_inst;
+
+	crypto_set_skcipher_spawn(&ctx->chacha, inst);
+	err = crypto_grab_skcipher(&ctx->chacha, chacha_name, 0,
+				   crypto_requires_sync(algt->type,
+							algt->mask));
+	if (err)
+		goto err_drop_poly;
+
+	chacha = crypto_skcipher_spawn_alg(&ctx->chacha);
+
+	err = -EINVAL;
+	/* Need 16-byte IV size, including Initial Block Counter value */
+	if (chacha->cra_ablkcipher.ivsize != CHACHA20_IV_SIZE)
+		goto out_drop_chacha;
+	/* Not a stream cipher? */
+	if (chacha->cra_blocksize != 1)
+		goto out_drop_chacha;
+
+	err = -ENAMETOOLONG;
+	if (snprintf(inst->alg.cra_name, CRYPTO_MAX_ALG_NAME,
+		     "%s(%s,%s)", name, chacha_name,
+		     poly_name) >= CRYPTO_MAX_ALG_NAME)
+		goto out_drop_chacha;
+	if (snprintf(inst->alg.cra_driver_name, CRYPTO_MAX_ALG_NAME,
+		     "%s(%s,%s)", name, chacha->cra_driver_name,
+		     poly->cra_driver_name) >= CRYPTO_MAX_ALG_NAME)
+		goto out_drop_chacha;
+
+	inst->alg.cra_flags = CRYPTO_ALG_TYPE_AEAD;
+	inst->alg.cra_flags |= (chacha->cra_flags |
+				poly->cra_flags) & CRYPTO_ALG_ASYNC;
+	inst->alg.cra_priority = (chacha->cra_priority +
+				  poly->cra_priority) / 2;
+	inst->alg.cra_blocksize = 1;
+	inst->alg.cra_alignmask = chacha->cra_alignmask | poly->cra_alignmask;
+	inst->alg.cra_type = &crypto_nivaead_type;
+	inst->alg.cra_aead.ivsize = ivsize;
+	inst->alg.cra_aead.maxauthsize = POLY1305_DIGEST_SIZE;
+	inst->alg.cra_ctxsize = sizeof(struct chachapoly_ctx) + ctx->saltlen;
+	inst->alg.cra_init = chachapoly_init;
+	inst->alg.cra_exit = chachapoly_exit;
+	inst->alg.cra_aead.encrypt = chachapoly_encrypt;
+	inst->alg.cra_aead.decrypt = chachapoly_decrypt;
+	inst->alg.cra_aead.setkey = chachapoly_setkey;
+	inst->alg.cra_aead.setauthsize = chachapoly_setauthsize;
+	inst->alg.cra_aead.geniv = "seqiv";
+
+out:
+	crypto_mod_put(poly);
+	return inst;
+
+out_drop_chacha:
+	crypto_drop_skcipher(&ctx->chacha);
+err_drop_poly:
+	crypto_drop_ahash(&ctx->poly);
+err_free_inst:
+	kfree(inst);
+out_put_poly:
+	inst = ERR_PTR(err);
+	goto out;
+}
+
+static struct crypto_instance *rfc7539_alloc(struct rtattr **tb)
+{
+	return chachapoly_alloc(tb, "rfc7539", 12);
+}
+
+static void chachapoly_free(struct crypto_instance *inst)
+{
+	struct chachapoly_instance_ctx *ctx = crypto_instance_ctx(inst);
+
+	crypto_drop_skcipher(&ctx->chacha);
+	crypto_drop_ahash(&ctx->poly);
+	kfree(inst);
+}
+
+static struct crypto_template rfc7539_tmpl = {
+	.name = "rfc7539",
+	.alloc = rfc7539_alloc,
+	.free = chachapoly_free,
+	.module = THIS_MODULE,
+};
+
+static int __init chacha20poly1305_module_init(void)
+{
+	return crypto_register_template(&rfc7539_tmpl);
+}
+
+static void __exit chacha20poly1305_module_exit(void)
+{
+	crypto_unregister_template(&rfc7539_tmpl);
+}
+
+module_init(chacha20poly1305_module_init);
+module_exit(chacha20poly1305_module_exit);
+
+MODULE_LICENSE("GPL");
+MODULE_AUTHOR("Martin Willi <martin@strongswan.org>");
+MODULE_DESCRIPTION("ChaCha20-Poly1305 AEAD");
+MODULE_ALIAS_CRYPTO("chacha20poly1305");
+MODULE_ALIAS_CRYPTO("rfc7539");