/* 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 <openssl/aead.h>
#include <string.h>
#include <openssl/chacha.h>
#include <openssl/cipher.h>
#include <openssl/cpu.h>
#include <openssl/err.h>
#include <openssl/mem.h>
#include <openssl/poly1305.h>
#include "internal.h"
#include "../internal.h"
#define POLY1305_TAG_LEN 16
struct aead_chacha20_poly1305_ctx {
unsigned char key[32];
unsigned char tag_len;
};
#if defined(OPENSSL_X86_64) && !defined(OPENSSL_NO_ASM) && \
!defined(OPENSSL_WINDOWS)
static int asm_capable(void) {
const int sse41_capable = (OPENSSL_ia32cap_P[1] & (1 << 19)) != 0;
return sse41_capable;
}
// chacha20_poly1305_open is defined in chacha20_poly1305_x86_64.pl. It
// decrypts |plaintext_len| bytes from |ciphertext| and writes them to
// |out_plaintext|. On entry, |aead_data| must contain the final 48 bytes of
// the initial ChaCha20 block, i.e. the key, followed by four zeros, followed
// by the nonce. On exit, it will contain the calculated tag value, which the
// caller must check.
extern void chacha20_poly1305_open(uint8_t *out_plaintext,
const uint8_t *ciphertext,
size_t plaintext_len, const uint8_t *ad,
size_t ad_len, uint8_t *aead_data);
// chacha20_poly1305_open is defined in chacha20_poly1305_x86_64.pl. It
// encrypts |plaintext_len| bytes from |plaintext| and writes them to
// |out_ciphertext|. On entry, |aead_data| must contain the final 48 bytes of
// the initial ChaCha20 block, i.e. the key, followed by four zeros, followed
// by the nonce. On exit, it will contain the calculated tag value, which the
// caller must append to the ciphertext.
extern void chacha20_poly1305_seal(uint8_t *out_ciphertext,
const uint8_t *plaintext,
size_t plaintext_len, const uint8_t *ad,
size_t ad_len, uint8_t *aead_data);
#else
static int asm_capable(void) {
return 0;
}
static void chacha20_poly1305_open(uint8_t *out_plaintext,
const uint8_t *ciphertext,
size_t plaintext_len, const uint8_t *ad,
size_t ad_len, uint8_t *aead_data) {}
static void chacha20_poly1305_seal(uint8_t *out_ciphertext,
const uint8_t *plaintext,
size_t plaintext_len, const uint8_t *ad,
size_t ad_len, uint8_t *aead_data) {}
#endif
static int aead_chacha20_poly1305_init(EVP_AEAD_CTX *ctx, const uint8_t *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) {
OPENSSL_PUT_ERROR(CIPHER, CIPHER_R_TOO_LARGE);
return 0;
}
if (key_len != sizeof(c20_ctx->key)) {
return 0; /* internal error - EVP_AEAD_CTX_init should catch this. */
}
c20_ctx = OPENSSL_malloc(sizeof(struct aead_chacha20_poly1305_ctx));
if (c20_ctx == NULL) {
return 0;
}
OPENSSL_memcpy(c20_ctx->key, 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));
OPENSSL_free(c20_ctx);
}
static void poly1305_update_length(poly1305_state *poly1305, size_t data_len) {
uint8_t length_bytes[8];
for (unsigned i = 0; i < sizeof(length_bytes); i++) {
length_bytes[i] = data_len;
data_len >>= 8;
}
CRYPTO_poly1305_update(poly1305, length_bytes, sizeof(length_bytes));
}
static void poly1305_update_padded_16(poly1305_state *poly1305,
const uint8_t *data, size_t data_len) {
static const uint8_t padding[16] = { 0 }; /* Padding is all zeros. */
CRYPTO_poly1305_update(poly1305, data, data_len);
if (data_len % 16 != 0) {
CRYPTO_poly1305_update(poly1305, padding,
sizeof(padding) - (data_len % 16));
}
}
/* calc_tag fills |tag| with the authentication tag for the given inputs. */
static void calc_tag(uint8_t tag[POLY1305_TAG_LEN],
const struct aead_chacha20_poly1305_ctx *c20_ctx,
const uint8_t nonce[12], const uint8_t *ad, size_t ad_len,
const uint8_t *ciphertext, size_t ciphertext_len) {
alignas(16) uint8_t poly1305_key[32];
OPENSSL_memset(poly1305_key, 0, sizeof(poly1305_key));
CRYPTO_chacha_20(poly1305_key, poly1305_key, sizeof(poly1305_key),
c20_ctx->key, nonce, 0);
poly1305_state ctx;
CRYPTO_poly1305_init(&ctx, poly1305_key);
poly1305_update_padded_16(&ctx, ad, ad_len);
poly1305_update_padded_16(&ctx, ciphertext, ciphertext_len);
poly1305_update_length(&ctx, ad_len);
poly1305_update_length(&ctx, ciphertext_len);
CRYPTO_poly1305_finish(&ctx, tag);
}
static int aead_chacha20_poly1305_seal(const EVP_AEAD_CTX *ctx, uint8_t *out,
size_t *out_len, size_t max_out_len,
const uint8_t *nonce, size_t nonce_len,
const uint8_t *in, size_t in_len,
const uint8_t *ad, size_t ad_len) {
const struct aead_chacha20_poly1305_ctx *c20_ctx = ctx->aead_state;
const uint64_t in_len_64 = in_len;
if (nonce_len != 12) {
OPENSSL_PUT_ERROR(CIPHER, CIPHER_R_UNSUPPORTED_NONCE_SIZE);
return 0;
}
/* |CRYPTO_chacha_20| uses a 32-bit block counter. Therefore we disallow
* individual operations that work on more than 256GB 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 >= (UINT64_C(1) << 32) * 64 - 64) {
OPENSSL_PUT_ERROR(CIPHER, CIPHER_R_TOO_LARGE);
return 0;
}
if (in_len + c20_ctx->tag_len < in_len) {
OPENSSL_PUT_ERROR(CIPHER, CIPHER_R_TOO_LARGE);
return 0;
}
if (max_out_len < in_len + c20_ctx->tag_len) {
OPENSSL_PUT_ERROR(CIPHER, CIPHER_R_BUFFER_TOO_SMALL);
return 0;
}
alignas(16) uint8_t tag[48];
if (asm_capable()) {
OPENSSL_memcpy(tag, c20_ctx->key, 32);
OPENSSL_memset(tag + 32, 0, 4);
OPENSSL_memcpy(tag + 32 + 4, nonce, 12);
chacha20_poly1305_seal(out, in, in_len, ad, ad_len, tag);
} else {
CRYPTO_chacha_20(out, in, in_len, c20_ctx->key, nonce, 1);
calc_tag(tag, c20_ctx, nonce, ad, ad_len, out, in_len);
}
OPENSSL_memcpy(out + in_len, tag, c20_ctx->tag_len);
*out_len = in_len + c20_ctx->tag_len;
return 1;
}
static int aead_chacha20_poly1305_open(const EVP_AEAD_CTX *ctx, uint8_t *out,
size_t *out_len, size_t max_out_len,
const uint8_t *nonce, size_t nonce_len,
const uint8_t *in, size_t in_len,
const uint8_t *ad, size_t ad_len) {
const struct aead_chacha20_poly1305_ctx *c20_ctx = ctx->aead_state;
size_t plaintext_len;
const uint64_t in_len_64 = in_len;
if (nonce_len != 12) {
OPENSSL_PUT_ERROR(CIPHER, CIPHER_R_UNSUPPORTED_NONCE_SIZE);
return 0;
}
if (in_len < c20_ctx->tag_len) {
OPENSSL_PUT_ERROR(CIPHER, CIPHER_R_BAD_DECRYPT);
return 0;
}
/* |CRYPTO_chacha_20| uses a 32-bit block counter. Therefore we disallow
* individual operations that work on more than 256GB 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 >= (UINT64_C(1) << 32) * 64 - 64) {
OPENSSL_PUT_ERROR(CIPHER, CIPHER_R_TOO_LARGE);
return 0;
}
plaintext_len = in_len - c20_ctx->tag_len;
alignas(16) uint8_t tag[48];
if (asm_capable()) {
OPENSSL_memcpy(tag, c20_ctx->key, 32);
OPENSSL_memset(tag + 32, 0, 4);
OPENSSL_memcpy(tag + 32 + 4, nonce, 12);
chacha20_poly1305_open(out, in, plaintext_len, ad, ad_len, tag);
} else {
calc_tag(tag, c20_ctx, nonce, ad, ad_len, in, plaintext_len);
CRYPTO_chacha_20(out, in, plaintext_len, c20_ctx->key, nonce, 1);
}
if (CRYPTO_memcmp(tag, in + plaintext_len, c20_ctx->tag_len) != 0) {
OPENSSL_PUT_ERROR(CIPHER, CIPHER_R_BAD_DECRYPT);
return 0;
}
*out_len = plaintext_len;
return 1;
}
static const EVP_AEAD aead_chacha20_poly1305 = {
32, /* key len */
12, /* nonce len */
POLY1305_TAG_LEN, /* overhead */
POLY1305_TAG_LEN, /* max tag length */
aead_chacha20_poly1305_init,
NULL, /* init_with_direction */
aead_chacha20_poly1305_cleanup,
aead_chacha20_poly1305_seal,
aead_chacha20_poly1305_open,
NULL, /* get_iv */
};
const EVP_AEAD *EVP_aead_chacha20_poly1305(void) {
return &aead_chacha20_poly1305;
}