lib/crypto/chacha20poly1305.c - linux - Git at Google

 // SPDX-License-Identifier: GPL-2.0 OR MIT
 /*
  * Copyright (C) 2015-2019 Jason A. Donenfeld <Jason@zx2c4.com>. All Rights Reserved.
  *
  * This is an implementation of the ChaCha20Poly1305 AEAD construction.
  *
  * Information: https://tools.ietf.org/html/rfc8439
  */

 #include <crypto/algapi.h>
 #include <crypto/chacha20poly1305.h>
 #include <crypto/chacha.h>
 #include <crypto/poly1305.h>
 #include <crypto/scatterwalk.h>

 #include <asm/unaligned.h>
 #include <linux/kernel.h>
 #include <linux/init.h>
 #include <linux/mm.h>
 #include <linux/module.h>

 #define CHACHA_KEY_WORDS	(CHACHA_KEY_SIZE / sizeof(u32))

 static void chacha_load_key(u32 *k, const u8 *in)
 {
 	k[0] = get_unaligned_le32(in);
 	k[1] = get_unaligned_le32(in + 4);
 	k[2] = get_unaligned_le32(in + 8);
 	k[3] = get_unaligned_le32(in + 12);
 	k[4] = get_unaligned_le32(in + 16);
 	k[5] = get_unaligned_le32(in + 20);
 	k[6] = get_unaligned_le32(in + 24);
 	k[7] = get_unaligned_le32(in + 28);
 }

 static void xchacha_init(u32 *chacha_state, const u8 *key, const u8 *nonce)
 {
 	u32 k[CHACHA_KEY_WORDS];
 	u8 iv[CHACHA_IV_SIZE];

 	memset(iv, 0, 8);
 	memcpy(iv + 8, nonce + 16, 8);

 	chacha_load_key(k, key);

 	/* Compute the subkey given the original key and first 128 nonce bits */
 	chacha_init(chacha_state, k, nonce);
 	hchacha_block(chacha_state, k, 20);

 	chacha_init(chacha_state, k, iv);

 	memzero_explicit(k, sizeof(k));
 	memzero_explicit(iv, sizeof(iv));
 }

 static void
 __chacha20poly1305_encrypt(u8 *dst, const u8 *src, const size_t src_len,
 			   const u8 *ad, const size_t ad_len, u32 *chacha_state)
 {
 	const u8 *pad0 = page_address(ZERO_PAGE(0));
 	struct poly1305_desc_ctx poly1305_state;
 	union {
 		u8 block0[POLY1305_KEY_SIZE];
 		__le64 lens[2];
 	} b;

 	chacha20_crypt(chacha_state, b.block0, pad0, sizeof(b.block0));
 	poly1305_init(&poly1305_state, b.block0);

 	poly1305_update(&poly1305_state, ad, ad_len);
 	if (ad_len & 0xf)
 		poly1305_update(&poly1305_state, pad0, 0x10 - (ad_len & 0xf));

 	chacha20_crypt(chacha_state, dst, src, src_len);

 	poly1305_update(&poly1305_state, dst, src_len);
 	if (src_len & 0xf)
 		poly1305_update(&poly1305_state, pad0, 0x10 - (src_len & 0xf));

 	b.lens[0] = cpu_to_le64(ad_len);
 	b.lens[1] = cpu_to_le64(src_len);
 	poly1305_update(&poly1305_state, (u8 *)b.lens, sizeof(b.lens));

 	poly1305_final(&poly1305_state, dst + src_len);

 	memzero_explicit(chacha_state, CHACHA_STATE_WORDS * sizeof(u32));
 	memzero_explicit(&b, sizeof(b));
 }

 void chacha20poly1305_encrypt(u8 *dst, const u8 *src, const size_t src_len,
 			      const u8 *ad, const size_t ad_len,
 			      const u64 nonce,
 			      const u8 key[CHACHA20POLY1305_KEY_SIZE])
 {
 	u32 chacha_state[CHACHA_STATE_WORDS];
 	u32 k[CHACHA_KEY_WORDS];
 	__le64 iv[2];

 	chacha_load_key(k, key);

 	iv[0] = 0;
 	iv[1] = cpu_to_le64(nonce);

 	chacha_init(chacha_state, k, (u8 *)iv);
 	__chacha20poly1305_encrypt(dst, src, src_len, ad, ad_len, chacha_state);

 	memzero_explicit(iv, sizeof(iv));
 	memzero_explicit(k, sizeof(k));
 }
 EXPORT_SYMBOL(chacha20poly1305_encrypt);

 void xchacha20poly1305_encrypt(u8 *dst, const u8 *src, const size_t src_len,
 			       const u8 *ad, const size_t ad_len,
 			       const u8 nonce[XCHACHA20POLY1305_NONCE_SIZE],
 			       const u8 key[CHACHA20POLY1305_KEY_SIZE])
 {
 	u32 chacha_state[CHACHA_STATE_WORDS];

 	xchacha_init(chacha_state, key, nonce);
 	__chacha20poly1305_encrypt(dst, src, src_len, ad, ad_len, chacha_state);
 }
 EXPORT_SYMBOL(xchacha20poly1305_encrypt);

 static bool
 __chacha20poly1305_decrypt(u8 *dst, const u8 *src, const size_t src_len,
 			   const u8 *ad, const size_t ad_len, u32 *chacha_state)
 {
 	const u8 *pad0 = page_address(ZERO_PAGE(0));
 	struct poly1305_desc_ctx poly1305_state;
 	size_t dst_len;
 	int ret;
 	union {
 		u8 block0[POLY1305_KEY_SIZE];
 		u8 mac[POLY1305_DIGEST_SIZE];
 		__le64 lens[2];
 	} b;

 	if (unlikely(src_len < POLY1305_DIGEST_SIZE))
 		return false;

 	chacha20_crypt(chacha_state, b.block0, pad0, sizeof(b.block0));
 	poly1305_init(&poly1305_state, b.block0);

 	poly1305_update(&poly1305_state, ad, ad_len);
 	if (ad_len & 0xf)
 		poly1305_update(&poly1305_state, pad0, 0x10 - (ad_len & 0xf));

 	dst_len = src_len - POLY1305_DIGEST_SIZE;
 	poly1305_update(&poly1305_state, src, dst_len);
 	if (dst_len & 0xf)
 		poly1305_update(&poly1305_state, pad0, 0x10 - (dst_len & 0xf));

 	b.lens[0] = cpu_to_le64(ad_len);
 	b.lens[1] = cpu_to_le64(dst_len);
 	poly1305_update(&poly1305_state, (u8 *)b.lens, sizeof(b.lens));

 	poly1305_final(&poly1305_state, b.mac);

 	ret = crypto_memneq(b.mac, src + dst_len, POLY1305_DIGEST_SIZE);
 	if (likely(!ret))
 		chacha20_crypt(chacha_state, dst, src, dst_len);

 	memzero_explicit(&b, sizeof(b));

 	return !ret;
 }

 bool chacha20poly1305_decrypt(u8 *dst, const u8 *src, const size_t src_len,
 			      const u8 *ad, const size_t ad_len,
 			      const u64 nonce,
 			      const u8 key[CHACHA20POLY1305_KEY_SIZE])
 {
 	u32 chacha_state[CHACHA_STATE_WORDS];
 	u32 k[CHACHA_KEY_WORDS];
 	__le64 iv[2];
 	bool ret;

 	chacha_load_key(k, key);

 	iv[0] = 0;
 	iv[1] = cpu_to_le64(nonce);

 	chacha_init(chacha_state, k, (u8 *)iv);
 	ret = __chacha20poly1305_decrypt(dst, src, src_len, ad, ad_len,
 					 chacha_state);

 	memzero_explicit(chacha_state, sizeof(chacha_state));
 	memzero_explicit(iv, sizeof(iv));
 	memzero_explicit(k, sizeof(k));
 	return ret;
 }
 EXPORT_SYMBOL(chacha20poly1305_decrypt);

 bool xchacha20poly1305_decrypt(u8 *dst, const u8 *src, const size_t src_len,
 			       const u8 *ad, const size_t ad_len,
 			       const u8 nonce[XCHACHA20POLY1305_NONCE_SIZE],
 			       const u8 key[CHACHA20POLY1305_KEY_SIZE])
 {
 	u32 chacha_state[CHACHA_STATE_WORDS];

 	xchacha_init(chacha_state, key, nonce);
 	return __chacha20poly1305_decrypt(dst, src, src_len, ad, ad_len,
 					  chacha_state);
 }
 EXPORT_SYMBOL(xchacha20poly1305_decrypt);

 static
 bool chacha20poly1305_crypt_sg_inplace(struct scatterlist *src,
 				       const size_t src_len,
 				       const u8 *ad, const size_t ad_len,
 				       const u64 nonce,
 				       const u8 key[CHACHA20POLY1305_KEY_SIZE],
 				       int encrypt)
 {
 	const u8 *pad0 = page_address(ZERO_PAGE(0));
 	struct poly1305_desc_ctx poly1305_state;
 	u32 chacha_state[CHACHA_STATE_WORDS];
 	struct sg_mapping_iter miter;
 	size_t partial = 0;
 	unsigned int flags;
 	bool ret = true;
 	int sl;
 	union {
 		struct {
 			u32 k[CHACHA_KEY_WORDS];
 			__le64 iv[2];
 		};
 		u8 block0[POLY1305_KEY_SIZE];
 		u8 chacha_stream[CHACHA_BLOCK_SIZE];
 		struct {
 			u8 mac[2][POLY1305_DIGEST_SIZE];
 		};
 		__le64 lens[2];
 	} b __aligned(16);

 	if (WARN_ON(src_len > INT_MAX))
 		return false;

 	chacha_load_key(b.k, key);

 	b.iv[0] = 0;
 	b.iv[1] = cpu_to_le64(nonce);

 	chacha_init(chacha_state, b.k, (u8 *)b.iv);
 	chacha20_crypt(chacha_state, b.block0, pad0, sizeof(b.block0));
 	poly1305_init(&poly1305_state, b.block0);

 	if (unlikely(ad_len)) {
 		poly1305_update(&poly1305_state, ad, ad_len);
 		if (ad_len & 0xf)
 			poly1305_update(&poly1305_state, pad0, 0x10 - (ad_len & 0xf));
 	}

 	flags = SG_MITER_TO_SG;
 	if (!preemptible())
 		flags |= SG_MITER_ATOMIC;

 	sg_miter_start(&miter, src, sg_nents(src), flags);

 	for (sl = src_len; sl > 0 && sg_miter_next(&miter); sl -= miter.length) {
 		u8 *addr = miter.addr;
 		size_t length = min_t(size_t, sl, miter.length);

 		if (!encrypt)
 			poly1305_update(&poly1305_state, addr, length);

 		if (unlikely(partial)) {
 			size_t l = min(length, CHACHA_BLOCK_SIZE - partial);

 			crypto_xor(addr, b.chacha_stream + partial, l);
 			partial = (partial + l) & (CHACHA_BLOCK_SIZE - 1);

 			addr += l;
 			length -= l;
 		}

 		if (likely(length >= CHACHA_BLOCK_SIZE || length == sl)) {
 			size_t l = length;

 			if (unlikely(length < sl))
 				l &= ~(CHACHA_BLOCK_SIZE - 1);
 			chacha20_crypt(chacha_state, addr, addr, l);
 			addr += l;
 			length -= l;
 		}

 		if (unlikely(length > 0)) {
 			chacha20_crypt(chacha_state, b.chacha_stream, pad0,
 				       CHACHA_BLOCK_SIZE);
 			crypto_xor(addr, b.chacha_stream, length);
 			partial = length;
 		}

 		if (encrypt)
 			poly1305_update(&poly1305_state, miter.addr,
 					min_t(size_t, sl, miter.length));
 	}

 	if (src_len & 0xf)
 		poly1305_update(&poly1305_state, pad0, 0x10 - (src_len & 0xf));

 	b.lens[0] = cpu_to_le64(ad_len);
 	b.lens[1] = cpu_to_le64(src_len);
 	poly1305_update(&poly1305_state, (u8 *)b.lens, sizeof(b.lens));

 	if (likely(sl <= -POLY1305_DIGEST_SIZE)) {
 		if (encrypt) {
 			poly1305_final(&poly1305_state,
 				       miter.addr + miter.length + sl);
 			ret = true;
 		} else {
 			poly1305_final(&poly1305_state, b.mac[0]);
 			ret = !crypto_memneq(b.mac[0],
 					     miter.addr + miter.length + sl,
 					     POLY1305_DIGEST_SIZE);
 		}
 	}

 	sg_miter_stop(&miter);

 	if (unlikely(sl > -POLY1305_DIGEST_SIZE)) {
 		poly1305_final(&poly1305_state, b.mac[1]);
 		scatterwalk_map_and_copy(b.mac[encrypt], src, src_len,
 					 sizeof(b.mac[1]), encrypt);
 		ret = encrypt ||
 		      !crypto_memneq(b.mac[0], b.mac[1], POLY1305_DIGEST_SIZE);
 	}

 	memzero_explicit(chacha_state, sizeof(chacha_state));
 	memzero_explicit(&b, sizeof(b));

 	return ret;
 }

 bool chacha20poly1305_encrypt_sg_inplace(struct scatterlist *src, size_t src_len,
 					 const u8 *ad, const size_t ad_len,
 					 const u64 nonce,
 					 const u8 key[CHACHA20POLY1305_KEY_SIZE])
 {
 	return chacha20poly1305_crypt_sg_inplace(src, src_len, ad, ad_len,
 						 nonce, key, 1);
 }
 EXPORT_SYMBOL(chacha20poly1305_encrypt_sg_inplace);

 bool chacha20poly1305_decrypt_sg_inplace(struct scatterlist *src, size_t src_len,
 					 const u8 *ad, const size_t ad_len,
 					 const u64 nonce,
 					 const u8 key[CHACHA20POLY1305_KEY_SIZE])
 {
 	if (unlikely(src_len < POLY1305_DIGEST_SIZE))
 		return false;

 	return chacha20poly1305_crypt_sg_inplace(src,
 						 src_len - POLY1305_DIGEST_SIZE,
 						 ad, ad_len, nonce, key, 0);
 }
 EXPORT_SYMBOL(chacha20poly1305_decrypt_sg_inplace);

 static int __init mod_init(void)
 {
 	if (!IS_ENABLED(CONFIG_CRYPTO_MANAGER_DISABLE_TESTS) &&
 	    WARN_ON(!chacha20poly1305_selftest()))
 		return -ENODEV;
 	return 0;
 }

 module_init(mod_init);
 MODULE_LICENSE("GPL v2");
 MODULE_DESCRIPTION("ChaCha20Poly1305 AEAD construction");
 MODULE_AUTHOR("Jason A. Donenfeld <Jason@zx2c4.com>");
	// SPDX-License-Identifier: GPL-2.0 OR MIT
	/*
	* Copyright (C) 2015-2019 Jason A. Donenfeld <Jason@zx2c4.com>. All Rights Reserved.
	*
	* This is an implementation of the ChaCha20Poly1305 AEAD construction.
	*
	* Information: https://tools.ietf.org/html/rfc8439
	*/

	#include <crypto/algapi.h>
	#include <crypto/chacha20poly1305.h>
	#include <crypto/chacha.h>
	#include <crypto/poly1305.h>
	#include <crypto/scatterwalk.h>

	#include <asm/unaligned.h>
	#include <linux/kernel.h>
	#include <linux/init.h>
	#include <linux/mm.h>
	#include <linux/module.h>

	#define CHACHA_KEY_WORDS (CHACHA_KEY_SIZE / sizeof(u32))

	static void chacha_load_key(u32 k, const u8 in)
	{
	k[0] = get_unaligned_le32(in);
	k[1] = get_unaligned_le32(in + 4);
	k[2] = get_unaligned_le32(in + 8);
	k[3] = get_unaligned_le32(in + 12);
	k[4] = get_unaligned_le32(in + 16);
	k[5] = get_unaligned_le32(in + 20);
	k[6] = get_unaligned_le32(in + 24);
	k[7] = get_unaligned_le32(in + 28);
	}

	static void xchacha_init(u32 chacha_state, const u8 key, const u8 *nonce)
	{
	u32 k[CHACHA_KEY_WORDS];
	u8 iv[CHACHA_IV_SIZE];

	memset(iv, 0, 8);
	memcpy(iv + 8, nonce + 16, 8);

	chacha_load_key(k, key);

	/* Compute the subkey given the original key and first 128 nonce bits */
	chacha_init(chacha_state, k, nonce);
	hchacha_block(chacha_state, k, 20);

	chacha_init(chacha_state, k, iv);

	memzero_explicit(k, sizeof(k));
	memzero_explicit(iv, sizeof(iv));
	}

	static void
	__chacha20poly1305_encrypt(u8 dst, const u8 src, const size_t src_len,
	const u8 ad, const size_t ad_len, u32 chacha_state)
	{
	const u8 *pad0 = page_address(ZERO_PAGE(0));
	struct poly1305_desc_ctx poly1305_state;
	union {
	u8 block0[POLY1305_KEY_SIZE];
	__le64 lens[2];
	} b;

	chacha20_crypt(chacha_state, b.block0, pad0, sizeof(b.block0));
	poly1305_init(&poly1305_state, b.block0);

	poly1305_update(&poly1305_state, ad, ad_len);
	if (ad_len & 0xf)
	poly1305_update(&poly1305_state, pad0, 0x10 - (ad_len & 0xf));

	chacha20_crypt(chacha_state, dst, src, src_len);

	poly1305_update(&poly1305_state, dst, src_len);
	if (src_len & 0xf)
	poly1305_update(&poly1305_state, pad0, 0x10 - (src_len & 0xf));

	b.lens[0] = cpu_to_le64(ad_len);
	b.lens[1] = cpu_to_le64(src_len);
	poly1305_update(&poly1305_state, (u8 *)b.lens, sizeof(b.lens));

	poly1305_final(&poly1305_state, dst + src_len);

	memzero_explicit(chacha_state, CHACHA_STATE_WORDS * sizeof(u32));
	memzero_explicit(&b, sizeof(b));
	}

	void chacha20poly1305_encrypt(u8 dst, const u8 src, const size_t src_len,
	const u8 *ad, const size_t ad_len,
	const u64 nonce,
	const u8 key[CHACHA20POLY1305_KEY_SIZE])
	{
	u32 chacha_state[CHACHA_STATE_WORDS];
	u32 k[CHACHA_KEY_WORDS];
	__le64 iv[2];

	chacha_load_key(k, key);

	iv[0] = 0;
	iv[1] = cpu_to_le64(nonce);

	chacha_init(chacha_state, k, (u8 *)iv);
	__chacha20poly1305_encrypt(dst, src, src_len, ad, ad_len, chacha_state);

	memzero_explicit(iv, sizeof(iv));
	memzero_explicit(k, sizeof(k));
	}
	EXPORT_SYMBOL(chacha20poly1305_encrypt);

	void xchacha20poly1305_encrypt(u8 dst, const u8 src, const size_t src_len,
	const u8 *ad, const size_t ad_len,
	const u8 nonce[XCHACHA20POLY1305_NONCE_SIZE],
	const u8 key[CHACHA20POLY1305_KEY_SIZE])
	{
	u32 chacha_state[CHACHA_STATE_WORDS];

	xchacha_init(chacha_state, key, nonce);
	__chacha20poly1305_encrypt(dst, src, src_len, ad, ad_len, chacha_state);
	}
	EXPORT_SYMBOL(xchacha20poly1305_encrypt);

	static bool
	__chacha20poly1305_decrypt(u8 dst, const u8 src, const size_t src_len,
	const u8 ad, const size_t ad_len, u32 chacha_state)
	{
	const u8 *pad0 = page_address(ZERO_PAGE(0));
	struct poly1305_desc_ctx poly1305_state;
	size_t dst_len;
	int ret;
	union {
	u8 block0[POLY1305_KEY_SIZE];
	u8 mac[POLY1305_DIGEST_SIZE];
	__le64 lens[2];
	} b;

	if (unlikely(src_len < POLY1305_DIGEST_SIZE))
	return false;

	chacha20_crypt(chacha_state, b.block0, pad0, sizeof(b.block0));
	poly1305_init(&poly1305_state, b.block0);

	poly1305_update(&poly1305_state, ad, ad_len);
	if (ad_len & 0xf)
	poly1305_update(&poly1305_state, pad0, 0x10 - (ad_len & 0xf));

	dst_len = src_len - POLY1305_DIGEST_SIZE;
	poly1305_update(&poly1305_state, src, dst_len);
	if (dst_len & 0xf)
	poly1305_update(&poly1305_state, pad0, 0x10 - (dst_len & 0xf));

	b.lens[0] = cpu_to_le64(ad_len);
	b.lens[1] = cpu_to_le64(dst_len);
	poly1305_update(&poly1305_state, (u8 *)b.lens, sizeof(b.lens));

	poly1305_final(&poly1305_state, b.mac);

	ret = crypto_memneq(b.mac, src + dst_len, POLY1305_DIGEST_SIZE);
	if (likely(!ret))
	chacha20_crypt(chacha_state, dst, src, dst_len);

	memzero_explicit(&b, sizeof(b));

	return !ret;
	}

	bool chacha20poly1305_decrypt(u8 dst, const u8 src, const size_t src_len,
	const u8 *ad, const size_t ad_len,
	const u64 nonce,
	const u8 key[CHACHA20POLY1305_KEY_SIZE])
	{
	u32 chacha_state[CHACHA_STATE_WORDS];
	u32 k[CHACHA_KEY_WORDS];
	__le64 iv[2];
	bool ret;

	chacha_load_key(k, key);

	iv[0] = 0;
	iv[1] = cpu_to_le64(nonce);

	chacha_init(chacha_state, k, (u8 *)iv);
	ret = __chacha20poly1305_decrypt(dst, src, src_len, ad, ad_len,
	chacha_state);

	memzero_explicit(chacha_state, sizeof(chacha_state));
	memzero_explicit(iv, sizeof(iv));
	memzero_explicit(k, sizeof(k));
	return ret;
	}
	EXPORT_SYMBOL(chacha20poly1305_decrypt);

	bool xchacha20poly1305_decrypt(u8 dst, const u8 src, const size_t src_len,
	const u8 *ad, const size_t ad_len,
	const u8 nonce[XCHACHA20POLY1305_NONCE_SIZE],
	const u8 key[CHACHA20POLY1305_KEY_SIZE])
	{
	u32 chacha_state[CHACHA_STATE_WORDS];

	xchacha_init(chacha_state, key, nonce);
	return __chacha20poly1305_decrypt(dst, src, src_len, ad, ad_len,
	chacha_state);
	}
	EXPORT_SYMBOL(xchacha20poly1305_decrypt);

	static
	bool chacha20poly1305_crypt_sg_inplace(struct scatterlist *src,
	const size_t src_len,
	const u8 *ad, const size_t ad_len,
	const u64 nonce,
	const u8 key[CHACHA20POLY1305_KEY_SIZE],
	int encrypt)
	{
	const u8 *pad0 = page_address(ZERO_PAGE(0));
	struct poly1305_desc_ctx poly1305_state;
	u32 chacha_state[CHACHA_STATE_WORDS];
	struct sg_mapping_iter miter;
	size_t partial = 0;
	unsigned int flags;
	bool ret = true;
	int sl;
	union {
	struct {
	u32 k[CHACHA_KEY_WORDS];
	__le64 iv[2];
	};
	u8 block0[POLY1305_KEY_SIZE];
	u8 chacha_stream[CHACHA_BLOCK_SIZE];
	struct {
	u8 mac[2][POLY1305_DIGEST_SIZE];
	};
	__le64 lens[2];
	} b __aligned(16);

	if (WARN_ON(src_len > INT_MAX))
	return false;

	chacha_load_key(b.k, key);

	b.iv[0] = 0;
	b.iv[1] = cpu_to_le64(nonce);

	chacha_init(chacha_state, b.k, (u8 *)b.iv);
	chacha20_crypt(chacha_state, b.block0, pad0, sizeof(b.block0));
	poly1305_init(&poly1305_state, b.block0);

	if (unlikely(ad_len)) {
	poly1305_update(&poly1305_state, ad, ad_len);
	if (ad_len & 0xf)
	poly1305_update(&poly1305_state, pad0, 0x10 - (ad_len & 0xf));
	}

	flags = SG_MITER_TO_SG;
	if (!preemptible())
	flags \|= SG_MITER_ATOMIC;

	sg_miter_start(&miter, src, sg_nents(src), flags);

	for (sl = src_len; sl > 0 && sg_miter_next(&miter); sl -= miter.length) {
	u8 *addr = miter.addr;
	size_t length = min_t(size_t, sl, miter.length);

	if (!encrypt)
	poly1305_update(&poly1305_state, addr, length);

	if (unlikely(partial)) {
	size_t l = min(length, CHACHA_BLOCK_SIZE - partial);

	crypto_xor(addr, b.chacha_stream + partial, l);
	partial = (partial + l) & (CHACHA_BLOCK_SIZE - 1);

	addr += l;
	length -= l;
	}

	if (likely(length >= CHACHA_BLOCK_SIZE \|\| length == sl)) {
	size_t l = length;

	if (unlikely(length < sl))
	l &= ~(CHACHA_BLOCK_SIZE - 1);
	chacha20_crypt(chacha_state, addr, addr, l);
	addr += l;
	length -= l;
	}

	if (unlikely(length > 0)) {
	chacha20_crypt(chacha_state, b.chacha_stream, pad0,
	CHACHA_BLOCK_SIZE);
	crypto_xor(addr, b.chacha_stream, length);
	partial = length;
	}

	if (encrypt)
	poly1305_update(&poly1305_state, miter.addr,
	min_t(size_t, sl, miter.length));
	}

	if (src_len & 0xf)
	poly1305_update(&poly1305_state, pad0, 0x10 - (src_len & 0xf));

	b.lens[0] = cpu_to_le64(ad_len);
	b.lens[1] = cpu_to_le64(src_len);
	poly1305_update(&poly1305_state, (u8 *)b.lens, sizeof(b.lens));

	if (likely(sl <= -POLY1305_DIGEST_SIZE)) {
	if (encrypt) {
	poly1305_final(&poly1305_state,
	miter.addr + miter.length + sl);
	ret = true;
	} else {
	poly1305_final(&poly1305_state, b.mac[0]);
	ret = !crypto_memneq(b.mac[0],
	miter.addr + miter.length + sl,
	POLY1305_DIGEST_SIZE);
	}
	}

	sg_miter_stop(&miter);

	if (unlikely(sl > -POLY1305_DIGEST_SIZE)) {
	poly1305_final(&poly1305_state, b.mac[1]);
	scatterwalk_map_and_copy(b.mac[encrypt], src, src_len,
	sizeof(b.mac[1]), encrypt);
	ret = encrypt \|\|
	!crypto_memneq(b.mac[0], b.mac[1], POLY1305_DIGEST_SIZE);
	}

	memzero_explicit(chacha_state, sizeof(chacha_state));
	memzero_explicit(&b, sizeof(b));

	return ret;
	}

	bool chacha20poly1305_encrypt_sg_inplace(struct scatterlist *src, size_t src_len,
	const u8 *ad, const size_t ad_len,
	const u64 nonce,
	const u8 key[CHACHA20POLY1305_KEY_SIZE])
	{
	return chacha20poly1305_crypt_sg_inplace(src, src_len, ad, ad_len,
	nonce, key, 1);
	}
	EXPORT_SYMBOL(chacha20poly1305_encrypt_sg_inplace);

	bool chacha20poly1305_decrypt_sg_inplace(struct scatterlist *src, size_t src_len,
	const u8 *ad, const size_t ad_len,
	const u64 nonce,
	const u8 key[CHACHA20POLY1305_KEY_SIZE])
	{
	if (unlikely(src_len < POLY1305_DIGEST_SIZE))
	return false;

	return chacha20poly1305_crypt_sg_inplace(src,
	src_len - POLY1305_DIGEST_SIZE,
	ad, ad_len, nonce, key, 0);
	}
	EXPORT_SYMBOL(chacha20poly1305_decrypt_sg_inplace);

	static int __init mod_init(void)
	{
	if (!IS_ENABLED(CONFIG_CRYPTO_MANAGER_DISABLE_TESTS) &&
	WARN_ON(!chacha20poly1305_selftest()))
	return -ENODEV;
	return 0;
	}

	module_init(mod_init);
	MODULE_LICENSE("GPL v2");
	MODULE_DESCRIPTION("ChaCha20Poly1305 AEAD construction");
	MODULE_AUTHOR("Jason A. Donenfeld <Jason@zx2c4.com>");