/* 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 <openssl/type_check.h>
#include "../fipsmodule/cipher/internal.h"
#include "../internal.h"
#define POLY1305_TAG_LEN 16
struct aead_chacha20_poly1305_ctx {
uint8_t key[32];
};
// For convenience (the x86_64 calling convention allows only six parameters in
// registers), the final parameter for the assembly functions is both an input
// and output parameter.
union open_data {
struct {
alignas(16) uint8_t key[32];
uint32_t counter;
uint8_t nonce[12];
} in;
struct {
uint8_t tag[POLY1305_TAG_LEN];
} out;
};
union seal_data {
struct {
alignas(16) uint8_t key[32];
uint32_t counter;
uint8_t nonce[12];
const uint8_t *extra_ciphertext;
size_t extra_ciphertext_len;
} in;
struct {
uint8_t tag[POLY1305_TAG_LEN];
} out;
};
#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;
}
OPENSSL_COMPILE_ASSERT(sizeof(union open_data) == 48, wrong_open_data_size);
OPENSSL_COMPILE_ASSERT(sizeof(union seal_data) == 48 + 8 + 8,
wrong_seal_data_size);
// chacha20_poly1305_open is defined in chacha20_poly1305_x86_64.pl. It decrypts
// |plaintext_len| bytes from |ciphertext| and writes them to |out_plaintext|.
// Additional input parameters are passed in |aead_data->in|. On exit, it will
// write calculated tag value to |aead_data->out.tag|, 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, union open_data *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|.
// Additional input parameters are passed in |aead_data->in|. The calculated tag
// value is over the computed ciphertext concatenated with |extra_ciphertext|
// and written to |aead_data->out.tag|.
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, union seal_data *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, union open_data *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, union seal_data *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);
ctx->aead_state = c20_ctx;
ctx->tag_len = tag_len;
return 1;
}
static void aead_chacha20_poly1305_cleanup(EVP_AEAD_CTX *ctx) {
OPENSSL_free(ctx->aead_state);
}
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));
}
// 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,
const uint8_t *ciphertext_extra,
size_t ciphertext_extra_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);
static const uint8_t padding[16] = { 0 }; // Padding is all zeros.
poly1305_state ctx;
CRYPTO_poly1305_init(&ctx, poly1305_key);
CRYPTO_poly1305_update(&ctx, ad, ad_len);
if (ad_len % 16 != 0) {
CRYPTO_poly1305_update(&ctx, padding, sizeof(padding) - (ad_len % 16));
}
CRYPTO_poly1305_update(&ctx, ciphertext, ciphertext_len);
CRYPTO_poly1305_update(&ctx, ciphertext_extra, ciphertext_extra_len);
const size_t ciphertext_total = ciphertext_len + ciphertext_extra_len;
if (ciphertext_total % 16 != 0) {
CRYPTO_poly1305_update(&ctx, padding,
sizeof(padding) - (ciphertext_total % 16));
}
poly1305_update_length(&ctx, ad_len);
poly1305_update_length(&ctx, ciphertext_total);
CRYPTO_poly1305_finish(&ctx, tag);
}
static int aead_chacha20_poly1305_seal_scatter(
const EVP_AEAD_CTX *ctx, uint8_t *out, uint8_t *out_tag,
size_t *out_tag_len, size_t max_out_tag_len, const uint8_t *nonce,
size_t nonce_len, const uint8_t *in, size_t in_len, const uint8_t *extra_in,
size_t extra_in_len, const uint8_t *ad, size_t ad_len) {
const struct aead_chacha20_poly1305_ctx *c20_ctx = ctx->aead_state;
if (extra_in_len + ctx->tag_len < ctx->tag_len) {
OPENSSL_PUT_ERROR(CIPHER, CIPHER_R_TOO_LARGE);
return 0;
}
if (max_out_tag_len < ctx->tag_len + extra_in_len) {
OPENSSL_PUT_ERROR(CIPHER, CIPHER_R_BUFFER_TOO_SMALL);
return 0;
}
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.
const uint64_t in_len_64 = in_len;
if (in_len_64 >= (UINT64_C(1) << 32) * 64 - 64) {
OPENSSL_PUT_ERROR(CIPHER, CIPHER_R_TOO_LARGE);
return 0;
}
if (max_out_tag_len < ctx->tag_len) {
OPENSSL_PUT_ERROR(CIPHER, CIPHER_R_BUFFER_TOO_SMALL);
return 0;
}
// The the extra input is given, it is expected to be very short and so is
// encrypted byte-by-byte first.
if (extra_in_len) {
static const size_t kChaChaBlockSize = 64;
uint32_t block_counter = 1 + (in_len / kChaChaBlockSize);
size_t offset = in_len % kChaChaBlockSize;
uint8_t block[64 /* kChaChaBlockSize */];
for (size_t done = 0; done < extra_in_len; block_counter++) {
memset(block, 0, sizeof(block));
CRYPTO_chacha_20(block, block, sizeof(block), c20_ctx->key, nonce,
block_counter);
for (size_t i = offset; i < sizeof(block) && done < extra_in_len;
i++, done++) {
out_tag[done] = extra_in[done] ^ block[i];
}
offset = 0;
}
}
union seal_data data;
if (asm_capable()) {
OPENSSL_memcpy(data.in.key, c20_ctx->key, 32);
data.in.counter = 0;
OPENSSL_memcpy(data.in.nonce, nonce, 12);
data.in.extra_ciphertext = out_tag;
data.in.extra_ciphertext_len = extra_in_len;
chacha20_poly1305_seal(out, in, in_len, ad, ad_len, &data);
} else {
CRYPTO_chacha_20(out, in, in_len, c20_ctx->key, nonce, 1);
calc_tag(data.out.tag, c20_ctx, nonce, ad, ad_len, out, in_len, out_tag,
extra_in_len);
}
OPENSSL_memcpy(out_tag + extra_in_len, data.out.tag, ctx->tag_len);
*out_tag_len = extra_in_len + ctx->tag_len;
return 1;
}
static int aead_chacha20_poly1305_open_gather(
const EVP_AEAD_CTX *ctx, uint8_t *out, const uint8_t *nonce,
size_t nonce_len, const uint8_t *in, size_t in_len, const uint8_t *in_tag,
size_t in_tag_len, const uint8_t *ad, size_t ad_len) {
const struct aead_chacha20_poly1305_ctx *c20_ctx = ctx->aead_state;
if (nonce_len != 12) {
OPENSSL_PUT_ERROR(CIPHER, CIPHER_R_UNSUPPORTED_NONCE_SIZE);
return 0;
}
if (in_tag_len != 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.
const uint64_t in_len_64 = in_len;
if (in_len_64 >= (UINT64_C(1) << 32) * 64 - 64) {
OPENSSL_PUT_ERROR(CIPHER, CIPHER_R_TOO_LARGE);
return 0;
}
union open_data data;
if (asm_capable()) {
OPENSSL_memcpy(data.in.key, c20_ctx->key, 32);
data.in.counter = 0;
OPENSSL_memcpy(data.in.nonce, nonce, 12);
chacha20_poly1305_open(out, in, in_len, ad, ad_len, &data);
} else {
calc_tag(data.out.tag, c20_ctx, nonce, ad, ad_len, in, in_len, NULL, 0);
CRYPTO_chacha_20(out, in, in_len, c20_ctx->key, nonce, 1);
}
if (CRYPTO_memcmp(data.out.tag, in_tag, ctx->tag_len) != 0) {
OPENSSL_PUT_ERROR(CIPHER, CIPHER_R_BAD_DECRYPT);
return 0;
}
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
1, // seal_scatter_supports_extra_in
aead_chacha20_poly1305_init,
NULL, // init_with_direction
aead_chacha20_poly1305_cleanup,
NULL /* open */,
aead_chacha20_poly1305_seal_scatter,
aead_chacha20_poly1305_open_gather,
NULL, // get_iv
NULL, // tag_len
};
const EVP_AEAD *EVP_aead_chacha20_poly1305(void) {
return &aead_chacha20_poly1305;
}