crypto: chacha20poly1305 - import construction and selftest from Zinc

This incorporates the chacha20poly1305 from the Zinc library, retaining
the library interface, but replacing the implementation with calls into
the code that already existed in the kernel's crypto API.

Note that this library API does not implement RFC7539 fully, given that
it is limited to 64-bit nonces. (The 96-bit nonce version that was part
of the selftest only has been removed, along with the 96-bit nonce test
vectors that only tested the selftest but not the actual library itself)
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>

include/crypto/chacha20poly1305.h

+/* SPDX-License-Identifier: GPL-2.0 OR MIT */
+/*
+ * Copyright (C) 2015-2019 Jason A. Donenfeld <Jason@zx2c4.com>. All Rights Reserved.
+ */
+
+#ifndef __CHACHA20POLY1305_H
+#define __CHACHA20POLY1305_H
+
+#include <linux/types.h>
+
+enum chacha20poly1305_lengths {
+	XCHACHA20POLY1305_NONCE_SIZE = 24,
+	CHACHA20POLY1305_KEY_SIZE = 32,
+	CHACHA20POLY1305_AUTHTAG_SIZE = 16
+};
+
+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]);
+
+bool __must_check
+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]);
+
+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]);
+
+bool __must_check 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]);
+
+#endif /* __CHACHA20POLY1305_H */

lib/crypto/Kconfig

@@ -119,5 +119,12 @@ config CRYPTO_LIB_POLY1305
 	  by either the generic implementation or an arch-specific one, if one
 	  is available and enabled.
 
+config CRYPTO_LIB_CHACHA20POLY1305
+	tristate "ChaCha20-Poly1305 AEAD support (8-byte nonce library version)"
+	depends on CRYPTO_ARCH_HAVE_LIB_CHACHA || !CRYPTO_ARCH_HAVE_LIB_CHACHA
+	depends on CRYPTO_ARCH_HAVE_LIB_POLY1305 || !CRYPTO_ARCH_HAVE_LIB_POLY1305
+	select CRYPTO_LIB_CHACHA
+	select CRYPTO_LIB_POLY1305
+
 config CRYPTO_LIB_SHA256
 	tristate

lib/crypto/Makefile

@@ -16,6 +16,9 @@ libblake2s-generic-y				+= blake2s-generic.o
 obj-$(CONFIG_CRYPTO_LIB_BLAKE2S)		+= libblake2s.o
 libblake2s-y					+= blake2s.o
 
+obj-$(CONFIG_CRYPTO_LIB_CHACHA20POLY1305)	+= libchacha20poly1305.o
+libchacha20poly1305-y				+= chacha20poly1305.o
+
 obj-$(CONFIG_CRYPTO_LIB_CURVE25519_GENERIC)	+= libcurve25519.o
 libcurve25519-y					:= curve25519-fiat32.o
 libcurve25519-$(CONFIG_ARCH_SUPPORTS_INT128)	:= curve25519-hacl64.o
@@ -32,4 +35,5 @@ libsha256-y					:= sha256.o
 
 ifneq ($(CONFIG_CRYPTO_MANAGER_DISABLE_TESTS),y)
 libblake2s-y					+= blake2s-selftest.o
+libchacha20poly1305-y				+= chacha20poly1305-selftest.o
 endif

lib/crypto/chacha20poly1305.c

+// 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 <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))
+
+bool __init chacha20poly1305_selftest(void);
+
+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;
+
+	chacha_crypt(chacha_state, b.block0, pad0, sizeof(b.block0), 20);
+	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));
+
+	chacha_crypt(chacha_state, dst, src, src_len, 20);
+
+	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;
+
+	chacha_crypt(chacha_state, b.block0, pad0, sizeof(b.block0), 20);
+	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))
+		chacha_crypt(chacha_state, dst, src, dst_len, 20);
+
+	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 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>");