ref: 009439541d2c6e8af2596f8fb1b4df85861fd212
dir: /third_party/boringssl/src/crypto/cipher_extra/e_aesgcmsiv.c/
/* Copyright (c) 2017, 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 <assert.h>
#include <openssl/cipher.h>
#include <openssl/crypto.h>
#include <openssl/err.h>
#include "../fipsmodule/cipher/internal.h"
#include "../internal.h"
#define EVP_AEAD_AES_GCM_SIV_NONCE_LEN 12
#define EVP_AEAD_AES_GCM_SIV_TAG_LEN 16
// TODO(davidben): AES-GCM-SIV assembly is not correct for Windows. It must save
// and restore xmm6 through xmm15.
#if defined(OPENSSL_X86_64) && !defined(OPENSSL_NO_ASM) && \
!defined(OPENSSL_WINDOWS)
#define AES_GCM_SIV_ASM
// Optimised AES-GCM-SIV
struct aead_aes_gcm_siv_asm_ctx {
alignas(16) uint8_t key[16*15];
int is_128_bit;
};
// The assembly code assumes 8-byte alignment of the EVP_AEAD_CTX's state, and
// aligns to 16 bytes itself.
static_assert(sizeof(((EVP_AEAD_CTX *)NULL)->state) + 8 >=
sizeof(struct aead_aes_gcm_siv_asm_ctx),
"AEAD state is too small");
static_assert(alignof(union evp_aead_ctx_st_state) >= 8,
"AEAD state has insufficient alignment");
// asm_ctx_from_ctx returns a 16-byte aligned context pointer from |ctx|.
static struct aead_aes_gcm_siv_asm_ctx *asm_ctx_from_ctx(
const EVP_AEAD_CTX *ctx) {
// ctx->state must already be 8-byte aligned. Thus, at most, we may need to
// add eight to align it to 16 bytes.
const uintptr_t offset = ((uintptr_t)&ctx->state) & 8;
return (struct aead_aes_gcm_siv_asm_ctx *)(&ctx->state.opaque[offset]);
}
// aes128gcmsiv_aes_ks writes an AES-128 key schedule for |key| to
// |out_expanded_key|.
extern void aes128gcmsiv_aes_ks(
const uint8_t key[16], uint8_t out_expanded_key[16*15]);
// aes256gcmsiv_aes_ks writes an AES-256 key schedule for |key| to
// |out_expanded_key|.
extern void aes256gcmsiv_aes_ks(
const uint8_t key[32], uint8_t out_expanded_key[16*15]);
static int aead_aes_gcm_siv_asm_init(EVP_AEAD_CTX *ctx, const uint8_t *key,
size_t key_len, size_t tag_len) {
const size_t key_bits = key_len * 8;
if (key_bits != 128 && key_bits != 256) {
OPENSSL_PUT_ERROR(CIPHER, CIPHER_R_BAD_KEY_LENGTH);
return 0; // EVP_AEAD_CTX_init should catch this.
}
if (tag_len == EVP_AEAD_DEFAULT_TAG_LENGTH) {
tag_len = EVP_AEAD_AES_GCM_SIV_TAG_LEN;
}
if (tag_len != EVP_AEAD_AES_GCM_SIV_TAG_LEN) {
OPENSSL_PUT_ERROR(CIPHER, CIPHER_R_TAG_TOO_LARGE);
return 0;
}
struct aead_aes_gcm_siv_asm_ctx *gcm_siv_ctx = asm_ctx_from_ctx(ctx);
assert((((uintptr_t)gcm_siv_ctx) & 15) == 0);
if (key_bits == 128) {
aes128gcmsiv_aes_ks(key, &gcm_siv_ctx->key[0]);
gcm_siv_ctx->is_128_bit = 1;
} else {
aes256gcmsiv_aes_ks(key, &gcm_siv_ctx->key[0]);
gcm_siv_ctx->is_128_bit = 0;
}
ctx->tag_len = tag_len;
return 1;
}
static void aead_aes_gcm_siv_asm_cleanup(EVP_AEAD_CTX *ctx) {}
// aesgcmsiv_polyval_horner updates the POLYVAL value in |in_out_poly| to
// include a number (|in_blocks|) of 16-byte blocks of data from |in|, given
// the POLYVAL key in |key|.
extern void aesgcmsiv_polyval_horner(const uint8_t in_out_poly[16],
const uint8_t key[16], const uint8_t *in,
size_t in_blocks);
// aesgcmsiv_htable_init writes powers 1..8 of |auth_key| to |out_htable|.
extern void aesgcmsiv_htable_init(uint8_t out_htable[16 * 8],
const uint8_t auth_key[16]);
// aesgcmsiv_htable6_init writes powers 1..6 of |auth_key| to |out_htable|.
extern void aesgcmsiv_htable6_init(uint8_t out_htable[16 * 6],
const uint8_t auth_key[16]);
// aesgcmsiv_htable_polyval updates the POLYVAL value in |in_out_poly| to
// include |in_len| bytes of data from |in|. (Where |in_len| must be a multiple
// of 16.) It uses the precomputed powers of the key given in |htable|.
extern void aesgcmsiv_htable_polyval(const uint8_t htable[16 * 8],
const uint8_t *in, size_t in_len,
uint8_t in_out_poly[16]);
// aes128gcmsiv_dec decrypts |in_len| & ~15 bytes from |out| and writes them to
// |in|. |in| and |out| may be equal, but must not otherwise alias.
//
// |in_out_calculated_tag_and_scratch|, on entry, must contain:
// 1. The current value of the calculated tag, which will be updated during
// decryption and written back to the beginning of this buffer on exit.
// 2. The claimed tag, which is needed to derive counter values.
//
// While decrypting, the whole of |in_out_calculated_tag_and_scratch| may be
// used for other purposes. In order to decrypt and update the POLYVAL value, it
// uses the expanded key from |key| and the table of powers in |htable|.
extern void aes128gcmsiv_dec(const uint8_t *in, uint8_t *out,
uint8_t in_out_calculated_tag_and_scratch[16 * 8],
const uint8_t htable[16 * 6],
const struct aead_aes_gcm_siv_asm_ctx *key,
size_t in_len);
// aes256gcmsiv_dec acts like |aes128gcmsiv_dec|, but for AES-256.
extern void aes256gcmsiv_dec(const uint8_t *in, uint8_t *out,
uint8_t in_out_calculated_tag_and_scratch[16 * 8],
const uint8_t htable[16 * 6],
const struct aead_aes_gcm_siv_asm_ctx *key,
size_t in_len);
// aes128gcmsiv_kdf performs the AES-GCM-SIV KDF given the expanded key from
// |key_schedule| and the nonce in |nonce|. Note that, while only 12 bytes of
// the nonce are used, 16 bytes are read and so the value must be
// right-padded.
extern void aes128gcmsiv_kdf(const uint8_t nonce[16],
uint64_t out_key_material[8],
const uint8_t *key_schedule);
// aes256gcmsiv_kdf acts like |aes128gcmsiv_kdf|, but for AES-256.
extern void aes256gcmsiv_kdf(const uint8_t nonce[16],
uint64_t out_key_material[12],
const uint8_t *key_schedule);
// aes128gcmsiv_aes_ks_enc_x1 performs a key expansion of the AES-128 key in
// |key|, writes the expanded key to |out_expanded_key| and encrypts a single
// block from |in| to |out|.
extern void aes128gcmsiv_aes_ks_enc_x1(const uint8_t in[16], uint8_t out[16],
uint8_t out_expanded_key[16 * 15],
const uint64_t key[2]);
// aes256gcmsiv_aes_ks_enc_x1 acts like |aes128gcmsiv_aes_ks_enc_x1|, but for
// AES-256.
extern void aes256gcmsiv_aes_ks_enc_x1(const uint8_t in[16], uint8_t out[16],
uint8_t out_expanded_key[16 * 15],
const uint64_t key[4]);
// aes128gcmsiv_ecb_enc_block encrypts a single block from |in| to |out| using
// the expanded key in |expanded_key|.
extern void aes128gcmsiv_ecb_enc_block(
const uint8_t in[16], uint8_t out[16],
const struct aead_aes_gcm_siv_asm_ctx *expanded_key);
// aes256gcmsiv_ecb_enc_block acts like |aes128gcmsiv_ecb_enc_block|, but for
// AES-256.
extern void aes256gcmsiv_ecb_enc_block(
const uint8_t in[16], uint8_t out[16],
const struct aead_aes_gcm_siv_asm_ctx *expanded_key);
// aes128gcmsiv_enc_msg_x4 encrypts |in_len| bytes from |in| to |out| using the
// expanded key from |key|. (The value of |in_len| must be a multiple of 16.)
// The |in| and |out| buffers may be equal but must not otherwise overlap. The
// initial counter is constructed from the given |tag| as required by
// AES-GCM-SIV.
extern void aes128gcmsiv_enc_msg_x4(const uint8_t *in, uint8_t *out,
const uint8_t *tag,
const struct aead_aes_gcm_siv_asm_ctx *key,
size_t in_len);
// aes256gcmsiv_enc_msg_x4 acts like |aes128gcmsiv_enc_msg_x4|, but for
// AES-256.
extern void aes256gcmsiv_enc_msg_x4(const uint8_t *in, uint8_t *out,
const uint8_t *tag,
const struct aead_aes_gcm_siv_asm_ctx *key,
size_t in_len);
// aes128gcmsiv_enc_msg_x8 acts like |aes128gcmsiv_enc_msg_x4|, but is
// optimised for longer messages.
extern void aes128gcmsiv_enc_msg_x8(const uint8_t *in, uint8_t *out,
const uint8_t *tag,
const struct aead_aes_gcm_siv_asm_ctx *key,
size_t in_len);
// aes256gcmsiv_enc_msg_x8 acts like |aes256gcmsiv_enc_msg_x4|, but is
// optimised for longer messages.
extern void aes256gcmsiv_enc_msg_x8(const uint8_t *in, uint8_t *out,
const uint8_t *tag,
const struct aead_aes_gcm_siv_asm_ctx *key,
size_t in_len);
// gcm_siv_asm_polyval evaluates POLYVAL at |auth_key| on the given plaintext
// and AD. The result is written to |out_tag|.
static void gcm_siv_asm_polyval(uint8_t out_tag[16], const uint8_t *in,
size_t in_len, const uint8_t *ad, size_t ad_len,
const uint8_t auth_key[16],
const uint8_t nonce[12]) {
OPENSSL_memset(out_tag, 0, 16);
const size_t ad_blocks = ad_len / 16;
const size_t in_blocks = in_len / 16;
int htable_init = 0;
alignas(16) uint8_t htable[16*8];
if (ad_blocks > 8 || in_blocks > 8) {
htable_init = 1;
aesgcmsiv_htable_init(htable, auth_key);
}
if (htable_init) {
aesgcmsiv_htable_polyval(htable, ad, ad_len & ~15, out_tag);
} else {
aesgcmsiv_polyval_horner(out_tag, auth_key, ad, ad_blocks);
}
uint8_t scratch[16];
if (ad_len & 15) {
OPENSSL_memset(scratch, 0, sizeof(scratch));
OPENSSL_memcpy(scratch, &ad[ad_len & ~15], ad_len & 15);
aesgcmsiv_polyval_horner(out_tag, auth_key, scratch, 1);
}
if (htable_init) {
aesgcmsiv_htable_polyval(htable, in, in_len & ~15, out_tag);
} else {
aesgcmsiv_polyval_horner(out_tag, auth_key, in, in_blocks);
}
if (in_len & 15) {
OPENSSL_memset(scratch, 0, sizeof(scratch));
OPENSSL_memcpy(scratch, &in[in_len & ~15], in_len & 15);
aesgcmsiv_polyval_horner(out_tag, auth_key, scratch, 1);
}
uint8_t length_block[16];
CRYPTO_store_u64_le(length_block, ad_len * 8);
CRYPTO_store_u64_le(length_block + 8, in_len * 8);
aesgcmsiv_polyval_horner(out_tag, auth_key, length_block, 1);
for (size_t i = 0; i < 12; i++) {
out_tag[i] ^= nonce[i];
}
out_tag[15] &= 0x7f;
}
// aead_aes_gcm_siv_asm_crypt_last_block handles the encryption/decryption
// (same thing in CTR mode) of the final block of a plaintext/ciphertext. It
// writes |in_len| & 15 bytes to |out| + |in_len|, based on an initial counter
// derived from |tag|.
static void aead_aes_gcm_siv_asm_crypt_last_block(
int is_128_bit, uint8_t *out, const uint8_t *in, size_t in_len,
const uint8_t tag[16],
const struct aead_aes_gcm_siv_asm_ctx *enc_key_expanded) {
alignas(16) uint8_t counter[16];
OPENSSL_memcpy(&counter, tag, sizeof(counter));
counter[15] |= 0x80;
CRYPTO_store_u32_le(counter, CRYPTO_load_u32_le(counter) + in_len / 16);
if (is_128_bit) {
aes128gcmsiv_ecb_enc_block(counter, counter, enc_key_expanded);
} else {
aes256gcmsiv_ecb_enc_block(counter, counter, enc_key_expanded);
}
const size_t last_bytes_offset = in_len & ~15;
const size_t last_bytes_len = in_len & 15;
uint8_t *last_bytes_out = &out[last_bytes_offset];
const uint8_t *last_bytes_in = &in[last_bytes_offset];
for (size_t i = 0; i < last_bytes_len; i++) {
last_bytes_out[i] = last_bytes_in[i] ^ counter[i];
}
}
// aead_aes_gcm_siv_kdf calculates the record encryption and authentication
// keys given the |nonce|.
static void aead_aes_gcm_siv_kdf(
int is_128_bit, const struct aead_aes_gcm_siv_asm_ctx *gcm_siv_ctx,
uint64_t out_record_auth_key[2], uint64_t out_record_enc_key[4],
const uint8_t nonce[12]) {
alignas(16) uint8_t padded_nonce[16];
OPENSSL_memcpy(padded_nonce, nonce, 12);
alignas(16) uint64_t key_material[12];
if (is_128_bit) {
aes128gcmsiv_kdf(padded_nonce, key_material, &gcm_siv_ctx->key[0]);
out_record_enc_key[0] = key_material[4];
out_record_enc_key[1] = key_material[6];
} else {
aes256gcmsiv_kdf(padded_nonce, key_material, &gcm_siv_ctx->key[0]);
out_record_enc_key[0] = key_material[4];
out_record_enc_key[1] = key_material[6];
out_record_enc_key[2] = key_material[8];
out_record_enc_key[3] = key_material[10];
}
out_record_auth_key[0] = key_material[0];
out_record_auth_key[1] = key_material[2];
}
static int aead_aes_gcm_siv_asm_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_aes_gcm_siv_asm_ctx *gcm_siv_ctx = asm_ctx_from_ctx(ctx);
const uint64_t in_len_64 = in_len;
const uint64_t ad_len_64 = ad_len;
if (in_len_64 > (UINT64_C(1) << 36) ||
ad_len_64 >= (UINT64_C(1) << 61)) {
OPENSSL_PUT_ERROR(CIPHER, CIPHER_R_TOO_LARGE);
return 0;
}
if (max_out_tag_len < EVP_AEAD_AES_GCM_SIV_TAG_LEN) {
OPENSSL_PUT_ERROR(CIPHER, CIPHER_R_BUFFER_TOO_SMALL);
return 0;
}
if (nonce_len != EVP_AEAD_AES_GCM_SIV_NONCE_LEN) {
OPENSSL_PUT_ERROR(CIPHER, CIPHER_R_UNSUPPORTED_NONCE_SIZE);
return 0;
}
alignas(16) uint64_t record_auth_key[2];
alignas(16) uint64_t record_enc_key[4];
aead_aes_gcm_siv_kdf(gcm_siv_ctx->is_128_bit, gcm_siv_ctx, record_auth_key,
record_enc_key, nonce);
alignas(16) uint8_t tag[16] = {0};
gcm_siv_asm_polyval(tag, in, in_len, ad, ad_len,
(const uint8_t *)record_auth_key, nonce);
struct aead_aes_gcm_siv_asm_ctx enc_key_expanded;
if (gcm_siv_ctx->is_128_bit) {
aes128gcmsiv_aes_ks_enc_x1(tag, tag, &enc_key_expanded.key[0],
record_enc_key);
if (in_len < 128) {
aes128gcmsiv_enc_msg_x4(in, out, tag, &enc_key_expanded, in_len & ~15);
} else {
aes128gcmsiv_enc_msg_x8(in, out, tag, &enc_key_expanded, in_len & ~15);
}
} else {
aes256gcmsiv_aes_ks_enc_x1(tag, tag, &enc_key_expanded.key[0],
record_enc_key);
if (in_len < 128) {
aes256gcmsiv_enc_msg_x4(in, out, tag, &enc_key_expanded, in_len & ~15);
} else {
aes256gcmsiv_enc_msg_x8(in, out, tag, &enc_key_expanded, in_len & ~15);
}
}
if (in_len & 15) {
aead_aes_gcm_siv_asm_crypt_last_block(gcm_siv_ctx->is_128_bit, out, in,
in_len, tag, &enc_key_expanded);
}
OPENSSL_memcpy(out_tag, tag, sizeof(tag));
*out_tag_len = EVP_AEAD_AES_GCM_SIV_TAG_LEN;
return 1;
}
static int aead_aes_gcm_siv_asm_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 uint64_t ad_len_64 = ad_len;
if (ad_len_64 >= (UINT64_C(1) << 61)) {
OPENSSL_PUT_ERROR(CIPHER, CIPHER_R_TOO_LARGE);
return 0;
}
const uint64_t in_len_64 = in_len;
if (in_len_64 > UINT64_C(1) << 36 ||
in_tag_len != EVP_AEAD_AES_GCM_SIV_TAG_LEN) {
OPENSSL_PUT_ERROR(CIPHER, CIPHER_R_BAD_DECRYPT);
return 0;
}
if (nonce_len != EVP_AEAD_AES_GCM_SIV_NONCE_LEN) {
OPENSSL_PUT_ERROR(CIPHER, CIPHER_R_UNSUPPORTED_NONCE_SIZE);
return 0;
}
const struct aead_aes_gcm_siv_asm_ctx *gcm_siv_ctx = asm_ctx_from_ctx(ctx);
alignas(16) uint64_t record_auth_key[2];
alignas(16) uint64_t record_enc_key[4];
aead_aes_gcm_siv_kdf(gcm_siv_ctx->is_128_bit, gcm_siv_ctx, record_auth_key,
record_enc_key, nonce);
struct aead_aes_gcm_siv_asm_ctx expanded_key;
if (gcm_siv_ctx->is_128_bit) {
aes128gcmsiv_aes_ks((const uint8_t *) record_enc_key, &expanded_key.key[0]);
} else {
aes256gcmsiv_aes_ks((const uint8_t *) record_enc_key, &expanded_key.key[0]);
}
// calculated_tag is 16*8 bytes, rather than 16 bytes, because
// aes[128|256]gcmsiv_dec uses the extra as scratch space.
alignas(16) uint8_t calculated_tag[16 * 8] = {0};
OPENSSL_memset(calculated_tag, 0, EVP_AEAD_AES_GCM_SIV_TAG_LEN);
const size_t ad_blocks = ad_len / 16;
aesgcmsiv_polyval_horner(calculated_tag, (const uint8_t *)record_auth_key, ad,
ad_blocks);
uint8_t scratch[16];
if (ad_len & 15) {
OPENSSL_memset(scratch, 0, sizeof(scratch));
OPENSSL_memcpy(scratch, &ad[ad_len & ~15], ad_len & 15);
aesgcmsiv_polyval_horner(calculated_tag, (const uint8_t *)record_auth_key,
scratch, 1);
}
alignas(16) uint8_t htable[16 * 6];
aesgcmsiv_htable6_init(htable, (const uint8_t *)record_auth_key);
// aes[128|256]gcmsiv_dec needs access to the claimed tag. So it's put into
// its scratch space.
memcpy(calculated_tag + 16, in_tag, EVP_AEAD_AES_GCM_SIV_TAG_LEN);
if (gcm_siv_ctx->is_128_bit) {
aes128gcmsiv_dec(in, out, calculated_tag, htable, &expanded_key, in_len);
} else {
aes256gcmsiv_dec(in, out, calculated_tag, htable, &expanded_key, in_len);
}
if (in_len & 15) {
aead_aes_gcm_siv_asm_crypt_last_block(gcm_siv_ctx->is_128_bit, out, in,
in_len, in_tag, &expanded_key);
OPENSSL_memset(scratch, 0, sizeof(scratch));
OPENSSL_memcpy(scratch, out + (in_len & ~15), in_len & 15);
aesgcmsiv_polyval_horner(calculated_tag, (const uint8_t *)record_auth_key,
scratch, 1);
}
uint8_t length_block[16];
CRYPTO_store_u64_le(length_block, ad_len * 8);
CRYPTO_store_u64_le(length_block + 8, in_len * 8);
aesgcmsiv_polyval_horner(calculated_tag, (const uint8_t *)record_auth_key,
length_block, 1);
for (size_t i = 0; i < 12; i++) {
calculated_tag[i] ^= nonce[i];
}
calculated_tag[15] &= 0x7f;
if (gcm_siv_ctx->is_128_bit) {
aes128gcmsiv_ecb_enc_block(calculated_tag, calculated_tag, &expanded_key);
} else {
aes256gcmsiv_ecb_enc_block(calculated_tag, calculated_tag, &expanded_key);
}
if (CRYPTO_memcmp(calculated_tag, in_tag, EVP_AEAD_AES_GCM_SIV_TAG_LEN) !=
0) {
OPENSSL_PUT_ERROR(CIPHER, CIPHER_R_BAD_DECRYPT);
return 0;
}
return 1;
}
static const EVP_AEAD aead_aes_128_gcm_siv_asm = {
16, // key length
EVP_AEAD_AES_GCM_SIV_NONCE_LEN, // nonce length
EVP_AEAD_AES_GCM_SIV_TAG_LEN, // overhead
EVP_AEAD_AES_GCM_SIV_TAG_LEN, // max tag length
0, // seal_scatter_supports_extra_in
aead_aes_gcm_siv_asm_init,
NULL /* init_with_direction */,
aead_aes_gcm_siv_asm_cleanup,
NULL /* open */,
aead_aes_gcm_siv_asm_seal_scatter,
aead_aes_gcm_siv_asm_open_gather,
NULL /* get_iv */,
NULL /* tag_len */,
};
static const EVP_AEAD aead_aes_256_gcm_siv_asm = {
32, // key length
EVP_AEAD_AES_GCM_SIV_NONCE_LEN, // nonce length
EVP_AEAD_AES_GCM_SIV_TAG_LEN, // overhead
EVP_AEAD_AES_GCM_SIV_TAG_LEN, // max tag length
0, // seal_scatter_supports_extra_in
aead_aes_gcm_siv_asm_init,
NULL /* init_with_direction */,
aead_aes_gcm_siv_asm_cleanup,
NULL /* open */,
aead_aes_gcm_siv_asm_seal_scatter,
aead_aes_gcm_siv_asm_open_gather,
NULL /* get_iv */,
NULL /* tag_len */,
};
#endif // X86_64 && !NO_ASM && !WINDOWS
struct aead_aes_gcm_siv_ctx {
union {
double align;
AES_KEY ks;
} ks;
block128_f kgk_block;
unsigned is_256:1;
};
static_assert(sizeof(((EVP_AEAD_CTX *)NULL)->state) >=
sizeof(struct aead_aes_gcm_siv_ctx),
"AEAD state is too small");
static_assert(alignof(union evp_aead_ctx_st_state) >=
alignof(struct aead_aes_gcm_siv_ctx),
"AEAD state has insufficient alignment");
static int aead_aes_gcm_siv_init(EVP_AEAD_CTX *ctx, const uint8_t *key,
size_t key_len, size_t tag_len) {
const size_t key_bits = key_len * 8;
if (key_bits != 128 && key_bits != 256) {
OPENSSL_PUT_ERROR(CIPHER, CIPHER_R_BAD_KEY_LENGTH);
return 0; // EVP_AEAD_CTX_init should catch this.
}
if (tag_len == EVP_AEAD_DEFAULT_TAG_LENGTH) {
tag_len = EVP_AEAD_AES_GCM_SIV_TAG_LEN;
}
if (tag_len != EVP_AEAD_AES_GCM_SIV_TAG_LEN) {
OPENSSL_PUT_ERROR(CIPHER, CIPHER_R_TAG_TOO_LARGE);
return 0;
}
struct aead_aes_gcm_siv_ctx *gcm_siv_ctx =
(struct aead_aes_gcm_siv_ctx *)&ctx->state;
OPENSSL_memset(gcm_siv_ctx, 0, sizeof(struct aead_aes_gcm_siv_ctx));
aes_ctr_set_key(&gcm_siv_ctx->ks.ks, NULL, &gcm_siv_ctx->kgk_block, key,
key_len);
gcm_siv_ctx->is_256 = (key_len == 32);
ctx->tag_len = tag_len;
return 1;
}
static void aead_aes_gcm_siv_cleanup(EVP_AEAD_CTX *ctx) {}
// gcm_siv_crypt encrypts (or decrypts—it's the same thing) |in_len| bytes from
// |in| to |out|, using the block function |enc_block| with |key| in counter
// mode, starting at |initial_counter|. This differs from the traditional
// counter mode code in that the counter is handled little-endian, only the
// first four bytes are used and the GCM-SIV tweak to the final byte is
// applied. The |in| and |out| pointers may be equal but otherwise must not
// alias.
static void gcm_siv_crypt(uint8_t *out, const uint8_t *in, size_t in_len,
const uint8_t initial_counter[AES_BLOCK_SIZE],
block128_f enc_block, const AES_KEY *key) {
uint8_t counter[16];
OPENSSL_memcpy(counter, initial_counter, AES_BLOCK_SIZE);
counter[15] |= 0x80;
for (size_t done = 0; done < in_len;) {
uint8_t keystream[AES_BLOCK_SIZE];
enc_block(counter, keystream, key);
CRYPTO_store_u32_le(counter, CRYPTO_load_u32_le(counter) + 1);
size_t todo = AES_BLOCK_SIZE;
if (in_len - done < todo) {
todo = in_len - done;
}
for (size_t i = 0; i < todo; i++) {
out[done + i] = keystream[i] ^ in[done + i];
}
done += todo;
}
}
// gcm_siv_polyval evaluates POLYVAL at |auth_key| on the given plaintext and
// AD. The result is written to |out_tag|.
static void gcm_siv_polyval(
uint8_t out_tag[16], const uint8_t *in, size_t in_len, const uint8_t *ad,
size_t ad_len, const uint8_t auth_key[16],
const uint8_t nonce[EVP_AEAD_AES_GCM_SIV_NONCE_LEN]) {
struct polyval_ctx polyval_ctx;
CRYPTO_POLYVAL_init(&polyval_ctx, auth_key);
CRYPTO_POLYVAL_update_blocks(&polyval_ctx, ad, ad_len & ~15);
uint8_t scratch[16];
if (ad_len & 15) {
OPENSSL_memset(scratch, 0, sizeof(scratch));
OPENSSL_memcpy(scratch, &ad[ad_len & ~15], ad_len & 15);
CRYPTO_POLYVAL_update_blocks(&polyval_ctx, scratch, sizeof(scratch));
}
CRYPTO_POLYVAL_update_blocks(&polyval_ctx, in, in_len & ~15);
if (in_len & 15) {
OPENSSL_memset(scratch, 0, sizeof(scratch));
OPENSSL_memcpy(scratch, &in[in_len & ~15], in_len & 15);
CRYPTO_POLYVAL_update_blocks(&polyval_ctx, scratch, sizeof(scratch));
}
uint8_t length_block[16];
CRYPTO_store_u64_le(length_block, ((uint64_t) ad_len) * 8);
CRYPTO_store_u64_le(length_block + 8, ((uint64_t) in_len) * 8);
CRYPTO_POLYVAL_update_blocks(&polyval_ctx, length_block,
sizeof(length_block));
CRYPTO_POLYVAL_finish(&polyval_ctx, out_tag);
for (size_t i = 0; i < EVP_AEAD_AES_GCM_SIV_NONCE_LEN; i++) {
out_tag[i] ^= nonce[i];
}
out_tag[15] &= 0x7f;
}
// gcm_siv_record_keys contains the keys used for a specific GCM-SIV record.
struct gcm_siv_record_keys {
uint8_t auth_key[16];
union {
double align;
AES_KEY ks;
} enc_key;
block128_f enc_block;
};
// gcm_siv_keys calculates the keys for a specific GCM-SIV record with the
// given nonce and writes them to |*out_keys|.
static void gcm_siv_keys(
const struct aead_aes_gcm_siv_ctx *gcm_siv_ctx,
struct gcm_siv_record_keys *out_keys,
const uint8_t nonce[EVP_AEAD_AES_GCM_SIV_NONCE_LEN]) {
const AES_KEY *const key = &gcm_siv_ctx->ks.ks;
uint8_t key_material[(128 /* POLYVAL key */ + 256 /* max AES key */) / 8];
const size_t blocks_needed = gcm_siv_ctx->is_256 ? 6 : 4;
uint8_t counter[AES_BLOCK_SIZE];
OPENSSL_memset(counter, 0, AES_BLOCK_SIZE - EVP_AEAD_AES_GCM_SIV_NONCE_LEN);
OPENSSL_memcpy(counter + AES_BLOCK_SIZE - EVP_AEAD_AES_GCM_SIV_NONCE_LEN,
nonce, EVP_AEAD_AES_GCM_SIV_NONCE_LEN);
for (size_t i = 0; i < blocks_needed; i++) {
counter[0] = i;
uint8_t ciphertext[AES_BLOCK_SIZE];
gcm_siv_ctx->kgk_block(counter, ciphertext, key);
OPENSSL_memcpy(&key_material[i * 8], ciphertext, 8);
}
OPENSSL_memcpy(out_keys->auth_key, key_material, 16);
// Note the |ctr128_f| function uses a big-endian couner, while AES-GCM-SIV
// uses a little-endian counter. We ignore the return value and only use
// |block128_f|. This has a significant performance cost for the fallback
// bitsliced AES implementations (bsaes and aes_nohw).
//
// We currently do not consider AES-GCM-SIV to be performance-sensitive on
// client hardware. If this changes, we can write little-endian |ctr128_f|
// functions.
aes_ctr_set_key(&out_keys->enc_key.ks, NULL, &out_keys->enc_block,
key_material + 16, gcm_siv_ctx->is_256 ? 32 : 16);
}
static int aead_aes_gcm_siv_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_aes_gcm_siv_ctx *gcm_siv_ctx =
(struct aead_aes_gcm_siv_ctx *)&ctx->state;
const uint64_t in_len_64 = in_len;
const uint64_t ad_len_64 = ad_len;
if (in_len + EVP_AEAD_AES_GCM_SIV_TAG_LEN < in_len ||
in_len_64 > (UINT64_C(1) << 36) ||
ad_len_64 >= (UINT64_C(1) << 61)) {
OPENSSL_PUT_ERROR(CIPHER, CIPHER_R_TOO_LARGE);
return 0;
}
if (max_out_tag_len < EVP_AEAD_AES_GCM_SIV_TAG_LEN) {
OPENSSL_PUT_ERROR(CIPHER, CIPHER_R_BUFFER_TOO_SMALL);
return 0;
}
if (nonce_len != EVP_AEAD_AES_GCM_SIV_NONCE_LEN) {
OPENSSL_PUT_ERROR(CIPHER, CIPHER_R_UNSUPPORTED_NONCE_SIZE);
return 0;
}
struct gcm_siv_record_keys keys;
gcm_siv_keys(gcm_siv_ctx, &keys, nonce);
uint8_t tag[16];
gcm_siv_polyval(tag, in, in_len, ad, ad_len, keys.auth_key, nonce);
keys.enc_block(tag, tag, &keys.enc_key.ks);
gcm_siv_crypt(out, in, in_len, tag, keys.enc_block, &keys.enc_key.ks);
OPENSSL_memcpy(out_tag, tag, EVP_AEAD_AES_GCM_SIV_TAG_LEN);
*out_tag_len = EVP_AEAD_AES_GCM_SIV_TAG_LEN;
return 1;
}
static int aead_aes_gcm_siv_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 uint64_t ad_len_64 = ad_len;
if (ad_len_64 >= (UINT64_C(1) << 61)) {
OPENSSL_PUT_ERROR(CIPHER, CIPHER_R_TOO_LARGE);
return 0;
}
const uint64_t in_len_64 = in_len;
if (in_tag_len != EVP_AEAD_AES_GCM_SIV_TAG_LEN ||
in_len_64 > (UINT64_C(1) << 36) + AES_BLOCK_SIZE) {
OPENSSL_PUT_ERROR(CIPHER, CIPHER_R_BAD_DECRYPT);
return 0;
}
if (nonce_len != EVP_AEAD_AES_GCM_SIV_NONCE_LEN) {
OPENSSL_PUT_ERROR(CIPHER, CIPHER_R_UNSUPPORTED_NONCE_SIZE);
return 0;
}
const struct aead_aes_gcm_siv_ctx *gcm_siv_ctx =
(struct aead_aes_gcm_siv_ctx *)&ctx->state;
struct gcm_siv_record_keys keys;
gcm_siv_keys(gcm_siv_ctx, &keys, nonce);
gcm_siv_crypt(out, in, in_len, in_tag, keys.enc_block, &keys.enc_key.ks);
uint8_t expected_tag[EVP_AEAD_AES_GCM_SIV_TAG_LEN];
gcm_siv_polyval(expected_tag, out, in_len, ad, ad_len, keys.auth_key, nonce);
keys.enc_block(expected_tag, expected_tag, &keys.enc_key.ks);
if (CRYPTO_memcmp(expected_tag, in_tag, sizeof(expected_tag)) != 0) {
OPENSSL_PUT_ERROR(CIPHER, CIPHER_R_BAD_DECRYPT);
return 0;
}
return 1;
}
static const EVP_AEAD aead_aes_128_gcm_siv = {
16, // key length
EVP_AEAD_AES_GCM_SIV_NONCE_LEN, // nonce length
EVP_AEAD_AES_GCM_SIV_TAG_LEN, // overhead
EVP_AEAD_AES_GCM_SIV_TAG_LEN, // max tag length
0, // seal_scatter_supports_extra_in
aead_aes_gcm_siv_init,
NULL /* init_with_direction */,
aead_aes_gcm_siv_cleanup,
NULL /* open */,
aead_aes_gcm_siv_seal_scatter,
aead_aes_gcm_siv_open_gather,
NULL /* get_iv */,
NULL /* tag_len */,
};
static const EVP_AEAD aead_aes_256_gcm_siv = {
32, // key length
EVP_AEAD_AES_GCM_SIV_NONCE_LEN, // nonce length
EVP_AEAD_AES_GCM_SIV_TAG_LEN, // overhead
EVP_AEAD_AES_GCM_SIV_TAG_LEN, // max tag length
0, // seal_scatter_supports_extra_in
aead_aes_gcm_siv_init,
NULL /* init_with_direction */,
aead_aes_gcm_siv_cleanup,
NULL /* open */,
aead_aes_gcm_siv_seal_scatter,
aead_aes_gcm_siv_open_gather,
NULL /* get_iv */,
NULL /* tag_len */,
};
#if defined(AES_GCM_SIV_ASM)
const EVP_AEAD *EVP_aead_aes_128_gcm_siv(void) {
if (CRYPTO_is_AVX_capable() && CRYPTO_is_AESNI_capable()) {
return &aead_aes_128_gcm_siv_asm;
}
return &aead_aes_128_gcm_siv;
}
const EVP_AEAD *EVP_aead_aes_256_gcm_siv(void) {
if (CRYPTO_is_AVX_capable() && CRYPTO_is_AESNI_capable()) {
return &aead_aes_256_gcm_siv_asm;
}
return &aead_aes_256_gcm_siv;
}
#else
const EVP_AEAD *EVP_aead_aes_128_gcm_siv(void) {
return &aead_aes_128_gcm_siv;
}
const EVP_AEAD *EVP_aead_aes_256_gcm_siv(void) {
return &aead_aes_256_gcm_siv;
}
#endif // AES_GCM_SIV_ASM