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/* $OpenBSD: e_chacha20poly1305.c,v 1.8 2014/07/10 22:45:57 jsing Exp $ */
/*
* Copyright (c) 2014, Google Inc.
*
* Permission to use, copy, modify, and/or distribute this software for any
* purpose with or without fee is hereby granted, provided that the above
* copyright notice and this permission notice appear in all copies.
*
* THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
* WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
* MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY
* SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
* WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION
* OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN
* CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
*/
#include <stdint.h>
#include <string.h>
#include <openssl/opensslconf.h>
#if !defined(OPENSSL_NO_CHACHA) && !defined(OPENSSL_NO_POLY1305)
#include <openssl/err.h>
#include <openssl/evp.h>
#include <openssl/chacha.h>
#include <openssl/poly1305.h>
#include "evp_locl.h"
#define POLY1305_TAG_LEN 16
#define CHACHA20_NONCE_LEN 8
struct aead_chacha20_poly1305_ctx {
unsigned char key[32];
unsigned char tag_len;
};
static int
aead_chacha20_poly1305_init(EVP_AEAD_CTX *ctx, const unsigned char *key,
size_t key_len, size_t tag_len)
{
struct aead_chacha20_poly1305_ctx *c20_ctx;
if (tag_len == 0)
tag_len = POLY1305_TAG_LEN;
if (tag_len > POLY1305_TAG_LEN) {
EVPerr(EVP_F_AEAD_CHACHA20_POLY1305_INIT, EVP_R_TOO_LARGE);
return 0;
}
/* Internal error - EVP_AEAD_CTX_init should catch this. */
if (key_len != sizeof(c20_ctx->key))
return 0;
c20_ctx = malloc(sizeof(struct aead_chacha20_poly1305_ctx));
if (c20_ctx == NULL)
return 0;
memcpy(&c20_ctx->key[0], key, key_len);
c20_ctx->tag_len = tag_len;
ctx->aead_state = c20_ctx;
return 1;
}
static void
aead_chacha20_poly1305_cleanup(EVP_AEAD_CTX *ctx)
{
struct aead_chacha20_poly1305_ctx *c20_ctx = ctx->aead_state;
OPENSSL_cleanse(c20_ctx->key, sizeof(c20_ctx->key));
free(c20_ctx);
}
static void
poly1305_update_with_length(poly1305_state *poly1305,
const unsigned char *data, size_t data_len)
{
size_t j = data_len;
unsigned char length_bytes[8];
unsigned i;
for (i = 0; i < sizeof(length_bytes); i++) {
length_bytes[i] = j;
j >>= 8;
}
CRYPTO_poly1305_update(poly1305, data, data_len);
CRYPTO_poly1305_update(poly1305, length_bytes, sizeof(length_bytes));
}
static int
aead_chacha20_poly1305_seal(const EVP_AEAD_CTX *ctx, unsigned char *out,
size_t *out_len, size_t max_out_len, const unsigned char *nonce,
size_t nonce_len, const unsigned char *in, size_t in_len,
const unsigned char *ad, size_t ad_len)
{
const struct aead_chacha20_poly1305_ctx *c20_ctx = ctx->aead_state;
unsigned char poly1305_key[32];
poly1305_state poly1305;
const uint64_t in_len_64 = in_len;
/* The underlying ChaCha implementation may not overflow the block
* counter into the second counter word. Therefore we disallow
* individual operations that work on more than 2TB at a time.
* in_len_64 is needed because, on 32-bit platforms, size_t is only
* 32-bits and this produces a warning because it's always false.
* Casting to uint64_t inside the conditional is not sufficient to stop
* the warning. */
if (in_len_64 >= (1ULL << 32) * 64 - 64) {
EVPerr(EVP_F_AEAD_CHACHA20_POLY1305_SEAL, EVP_R_TOO_LARGE);
return 0;
}
if (max_out_len < in_len + c20_ctx->tag_len) {
EVPerr(EVP_F_AEAD_CHACHA20_POLY1305_SEAL,
EVP_R_BUFFER_TOO_SMALL);
return 0;
}
if (nonce_len != CHACHA20_NONCE_LEN) {
EVPerr(EVP_F_AEAD_CHACHA20_POLY1305_SEAL, EVP_R_IV_TOO_LARGE);
return 0;
}
memset(poly1305_key, 0, sizeof(poly1305_key));
CRYPTO_chacha_20(poly1305_key, poly1305_key, sizeof(poly1305_key),
c20_ctx->key, nonce, 0);
CRYPTO_poly1305_init(&poly1305, poly1305_key);
poly1305_update_with_length(&poly1305, ad, ad_len);
CRYPTO_chacha_20(out, in, in_len, c20_ctx->key, nonce, 1);
poly1305_update_with_length(&poly1305, out, in_len);
if (c20_ctx->tag_len != POLY1305_TAG_LEN) {
unsigned char tag[POLY1305_TAG_LEN];
CRYPTO_poly1305_finish(&poly1305, tag);
memcpy(out + in_len, tag, c20_ctx->tag_len);
*out_len = in_len + c20_ctx->tag_len;
return 1;
}
CRYPTO_poly1305_finish(&poly1305, out + in_len);
*out_len = in_len + POLY1305_TAG_LEN;
return 1;
}
static int
aead_chacha20_poly1305_open(const EVP_AEAD_CTX *ctx, unsigned char *out,
size_t *out_len, size_t max_out_len, const unsigned char *nonce,
size_t nonce_len, const unsigned char *in, size_t in_len,
const unsigned char *ad, size_t ad_len)
{
const struct aead_chacha20_poly1305_ctx *c20_ctx = ctx->aead_state;
unsigned char mac[POLY1305_TAG_LEN];
unsigned char poly1305_key[32];
poly1305_state poly1305;
const uint64_t in_len_64 = in_len;
size_t plaintext_len;
if (in_len < c20_ctx->tag_len) {
EVPerr(EVP_F_AEAD_CHACHA20_POLY1305_OPEN, EVP_R_BAD_DECRYPT);
return 0;
}
/* The underlying ChaCha implementation may not overflow the block
* counter into the second counter word. Therefore we disallow
* individual operations that work on more than 2TB at a time.
* in_len_64 is needed because, on 32-bit platforms, size_t is only
* 32-bits and this produces a warning because it's always false.
* Casting to uint64_t inside the conditional is not sufficient to stop
* the warning. */
if (in_len_64 >= (1ULL << 32) * 64 - 64) {
EVPerr(EVP_F_AEAD_CHACHA20_POLY1305_OPEN, EVP_R_TOO_LARGE);
return 0;
}
if (nonce_len != CHACHA20_NONCE_LEN) {
EVPerr(EVP_F_AEAD_CHACHA20_POLY1305_OPEN, EVP_R_IV_TOO_LARGE);
return 0;
}
plaintext_len = in_len - c20_ctx->tag_len;
if (max_out_len < plaintext_len) {
EVPerr(EVP_F_AEAD_CHACHA20_POLY1305_OPEN,
EVP_R_BUFFER_TOO_SMALL);
return 0;
}
memset(poly1305_key, 0, sizeof(poly1305_key));
CRYPTO_chacha_20(poly1305_key, poly1305_key, sizeof(poly1305_key),
c20_ctx->key, nonce, 0);
CRYPTO_poly1305_init(&poly1305, poly1305_key);
poly1305_update_with_length(&poly1305, ad, ad_len);
poly1305_update_with_length(&poly1305, in, plaintext_len);
CRYPTO_poly1305_finish(&poly1305, mac);
if (CRYPTO_memcmp(mac, in + plaintext_len, c20_ctx->tag_len) != 0) {
EVPerr(EVP_F_AEAD_CHACHA20_POLY1305_OPEN, EVP_R_BAD_DECRYPT);
return 0;
}
CRYPTO_chacha_20(out, in, plaintext_len, c20_ctx->key, nonce, 1);
*out_len = plaintext_len;
return 1;
}
static const EVP_AEAD aead_chacha20_poly1305 = {
.key_len = 32,
.nonce_len = CHACHA20_NONCE_LEN,
.overhead = POLY1305_TAG_LEN,
.max_tag_len = POLY1305_TAG_LEN,
.init = aead_chacha20_poly1305_init,
.cleanup = aead_chacha20_poly1305_cleanup,
.seal = aead_chacha20_poly1305_seal,
.open = aead_chacha20_poly1305_open,
};
const EVP_AEAD *
EVP_aead_chacha20_poly1305()
{
return &aead_chacha20_poly1305;
}
#endif /* !OPENSSL_NO_CHACHA && !OPENSSL_NO_POLY1305 */
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