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openssl/crypto/evp/e_chacha20_poly1305.c
Matt Caswell 2a3d0ee9d5 Prevent over long nonces in ChaCha20-Poly1305 
ChaCha20-Poly1305 is an AEAD cipher, and requires a unique nonce input for
every encryption operation. RFC 7539 specifies that the nonce value (IV)
should be 96 bits (12 bytes). OpenSSL allows a variable nonce length and
front pads the nonce with 0 bytes if it is less than 12 bytes. However it
also incorrectly allows a nonce to be set of up to 16 bytes. In this case
only the last 12 bytes are significant and any additional leading bytes are
ignored.

It is a requirement of using this cipher that nonce values are unique.
Messages encrypted using a reused nonce value are susceptible to serious
confidentiality and integrity attacks. If an application changes the
default nonce length to be longer than 12 bytes and then makes a change to
the leading bytes of the nonce expecting the new value to be a new unique
nonce then such an application could inadvertently encrypt messages with a
reused nonce.

Additionally the ignored bytes in a long nonce are not covered by the
integrity guarantee of this cipher. Any application that relies on the
integrity of these ignored leading bytes of a long nonce may be further
affected.

Any OpenSSL internal use of this cipher, including in SSL/TLS, is safe
because no such use sets such a long nonce value. However user
applications that use this cipher directly and set a non-default nonce
length to be longer than 12 bytes may be vulnerable.

CVE-2019-1543

Fixes #8345

Reviewed-by: Paul Dale <paul.dale@oracle.com>
Reviewed-by: Richard Levitte <levitte@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/8406)
2019-03-06 13:25:09 +00:00

632 lines
20 KiB
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/*
* Copyright 2015-2018 The OpenSSL Project Authors. All Rights Reserved.
*
* Licensed under the Apache License 2.0 (the "License"). You may not use
* this file except in compliance with the License. You can obtain a copy
* in the file LICENSE in the source distribution or at
* https://www.openssl.org/source/license.html
*/
#include <stdio.h>
#include "internal/cryptlib.h"
#ifndef OPENSSL_NO_CHACHA
# include <openssl/evp.h>
# include <openssl/objects.h>
# include "internal/evp_int.h"
# include "evp_locl.h"
# include "internal/chacha.h"
typedef struct {
union {
double align; /* this ensures even sizeof(EVP_CHACHA_KEY)%8==0 */
unsigned int d[CHACHA_KEY_SIZE / 4];
} key;
unsigned int counter[CHACHA_CTR_SIZE / 4];
unsigned char buf[CHACHA_BLK_SIZE];
unsigned int partial_len;
} EVP_CHACHA_KEY;
#define data(ctx) ((EVP_CHACHA_KEY *)(ctx)->cipher_data)
#define CHACHA20_POLY1305_MAX_IVLEN 12
static int chacha_init_key(EVP_CIPHER_CTX *ctx,
const unsigned char user_key[CHACHA_KEY_SIZE],
const unsigned char iv[CHACHA_CTR_SIZE], int enc)
{
EVP_CHACHA_KEY *key = data(ctx);
unsigned int i;
if (user_key)
for (i = 0; i < CHACHA_KEY_SIZE; i+=4) {
key->key.d[i/4] = CHACHA_U8TOU32(user_key+i);
}
if (iv)
for (i = 0; i < CHACHA_CTR_SIZE; i+=4) {
key->counter[i/4] = CHACHA_U8TOU32(iv+i);
}
key->partial_len = 0;
return 1;
}
static int chacha_cipher(EVP_CIPHER_CTX * ctx, unsigned char *out,
const unsigned char *inp, size_t len)
{
EVP_CHACHA_KEY *key = data(ctx);
unsigned int n, rem, ctr32;
if ((n = key->partial_len)) {
while (len && n < CHACHA_BLK_SIZE) {
*out++ = *inp++ ^ key->buf[n++];
len--;
}
key->partial_len = n;
if (len == 0)
return 1;
if (n == CHACHA_BLK_SIZE) {
key->partial_len = 0;
key->counter[0]++;
if (key->counter[0] == 0)
key->counter[1]++;
}
}
rem = (unsigned int)(len % CHACHA_BLK_SIZE);
len -= rem;
ctr32 = key->counter[0];
while (len >= CHACHA_BLK_SIZE) {
size_t blocks = len / CHACHA_BLK_SIZE;
/*
* 1<<28 is just a not-so-small yet not-so-large number...
* Below condition is practically never met, but it has to
* be checked for code correctness.
*/
if (sizeof(size_t)>sizeof(unsigned int) && blocks>(1U<<28))
blocks = (1U<<28);
/*
* As ChaCha20_ctr32 operates on 32-bit counter, caller
* has to handle overflow. 'if' below detects the
* overflow, which is then handled by limiting the
* amount of blocks to the exact overflow point...
*/
ctr32 += (unsigned int)blocks;
if (ctr32 < blocks) {
blocks -= ctr32;
ctr32 = 0;
}
blocks *= CHACHA_BLK_SIZE;
ChaCha20_ctr32(out, inp, blocks, key->key.d, key->counter);
len -= blocks;
inp += blocks;
out += blocks;
key->counter[0] = ctr32;
if (ctr32 == 0) key->counter[1]++;
}
if (rem) {
memset(key->buf, 0, sizeof(key->buf));
ChaCha20_ctr32(key->buf, key->buf, CHACHA_BLK_SIZE,
key->key.d, key->counter);
for (n = 0; n < rem; n++)
out[n] = inp[n] ^ key->buf[n];
key->partial_len = rem;
}
return 1;
}
static const EVP_CIPHER chacha20 = {
NID_chacha20,
1, /* block_size */
CHACHA_KEY_SIZE, /* key_len */
CHACHA_CTR_SIZE, /* iv_len, 128-bit counter in the context */
EVP_CIPH_CUSTOM_IV | EVP_CIPH_ALWAYS_CALL_INIT,
chacha_init_key,
chacha_cipher,
NULL,
sizeof(EVP_CHACHA_KEY),
NULL,
NULL,
NULL,
NULL
};
const EVP_CIPHER *EVP_chacha20(void)
{
return &chacha20;
}
# ifndef OPENSSL_NO_POLY1305
# include "internal/poly1305.h"
typedef struct {
EVP_CHACHA_KEY key;
unsigned int nonce[12/4];
unsigned char tag[POLY1305_BLOCK_SIZE];
unsigned char tls_aad[POLY1305_BLOCK_SIZE];
struct { uint64_t aad, text; } len;
int aad, mac_inited, tag_len, nonce_len;
size_t tls_payload_length;
} EVP_CHACHA_AEAD_CTX;
# define NO_TLS_PAYLOAD_LENGTH ((size_t)-1)
# define aead_data(ctx) ((EVP_CHACHA_AEAD_CTX *)(ctx)->cipher_data)
# define POLY1305_ctx(actx) ((POLY1305 *)(actx + 1))
static int chacha20_poly1305_init_key(EVP_CIPHER_CTX *ctx,
const unsigned char *inkey,
const unsigned char *iv, int enc)
{
EVP_CHACHA_AEAD_CTX *actx = aead_data(ctx);
if (!inkey && !iv)
return 1;
actx->len.aad = 0;
actx->len.text = 0;
actx->aad = 0;
actx->mac_inited = 0;
actx->tls_payload_length = NO_TLS_PAYLOAD_LENGTH;
if (iv != NULL) {
unsigned char temp[CHACHA_CTR_SIZE] = { 0 };
/* pad on the left */
if (actx->nonce_len <= CHACHA_CTR_SIZE)
memcpy(temp + CHACHA_CTR_SIZE - actx->nonce_len, iv,
actx->nonce_len);
chacha_init_key(ctx, inkey, temp, enc);
actx->nonce[0] = actx->key.counter[1];
actx->nonce[1] = actx->key.counter[2];
actx->nonce[2] = actx->key.counter[3];
} else {
chacha_init_key(ctx, inkey, NULL, enc);
}
return 1;
}
# if !defined(OPENSSL_SMALL_FOOTPRINT)
# if defined(POLY1305_ASM) && (defined(__x86_64) || defined(__x86_64__) || \
defined(_M_AMD64) || defined(_M_X64))
# define XOR128_HELPERS
void *xor128_encrypt_n_pad(void *out, const void *inp, void *otp, size_t len);
void *xor128_decrypt_n_pad(void *out, const void *inp, void *otp, size_t len);
static const unsigned char zero[4 * CHACHA_BLK_SIZE] = { 0 };
# else
static const unsigned char zero[2 * CHACHA_BLK_SIZE] = { 0 };
# endif
static int chacha20_poly1305_tls_cipher(EVP_CIPHER_CTX *ctx, unsigned char *out,
const unsigned char *in, size_t len)
{
EVP_CHACHA_AEAD_CTX *actx = aead_data(ctx);
size_t tail, tohash_len, buf_len, plen = actx->tls_payload_length;
unsigned char *buf, *tohash, *ctr, storage[sizeof(zero) + 32];
if (len != plen + POLY1305_BLOCK_SIZE)
return -1;
buf = storage + ((0 - (size_t)storage) & 15); /* align */
ctr = buf + CHACHA_BLK_SIZE;
tohash = buf + CHACHA_BLK_SIZE - POLY1305_BLOCK_SIZE;
# ifdef XOR128_HELPERS
if (plen <= 3 * CHACHA_BLK_SIZE) {
actx->key.counter[0] = 0;
buf_len = (plen + 2 * CHACHA_BLK_SIZE - 1) & (0 - CHACHA_BLK_SIZE);
ChaCha20_ctr32(buf, zero, buf_len, actx->key.key.d,
actx->key.counter);
Poly1305_Init(POLY1305_ctx(actx), buf);
actx->key.partial_len = 0;
memcpy(tohash, actx->tls_aad, POLY1305_BLOCK_SIZE);
tohash_len = POLY1305_BLOCK_SIZE;
actx->len.aad = EVP_AEAD_TLS1_AAD_LEN;
actx->len.text = plen;
if (plen) {
if (ctx->encrypt)
ctr = xor128_encrypt_n_pad(out, in, ctr, plen);
else
ctr = xor128_decrypt_n_pad(out, in, ctr, plen);
in += plen;
out += plen;
tohash_len = (size_t)(ctr - tohash);
}
}
# else
if (plen <= CHACHA_BLK_SIZE) {
size_t i;
actx->key.counter[0] = 0;
ChaCha20_ctr32(buf, zero, (buf_len = 2 * CHACHA_BLK_SIZE),
actx->key.key.d, actx->key.counter);
Poly1305_Init(POLY1305_ctx(actx), buf);
actx->key.partial_len = 0;
memcpy(tohash, actx->tls_aad, POLY1305_BLOCK_SIZE);
tohash_len = POLY1305_BLOCK_SIZE;
actx->len.aad = EVP_AEAD_TLS1_AAD_LEN;
actx->len.text = plen;
if (ctx->encrypt) {
for (i = 0; i < plen; i++) {
out[i] = ctr[i] ^= in[i];
}
} else {
for (i = 0; i < plen; i++) {
unsigned char c = in[i];
out[i] = ctr[i] ^ c;
ctr[i] = c;
}
}
in += i;
out += i;
tail = (0 - i) & (POLY1305_BLOCK_SIZE - 1);
memset(ctr + i, 0, tail);
ctr += i + tail;
tohash_len += i + tail;
}
# endif
else {
actx->key.counter[0] = 0;
ChaCha20_ctr32(buf, zero, (buf_len = CHACHA_BLK_SIZE),
actx->key.key.d, actx->key.counter);
Poly1305_Init(POLY1305_ctx(actx), buf);
actx->key.counter[0] = 1;
actx->key.partial_len = 0;
Poly1305_Update(POLY1305_ctx(actx), actx->tls_aad, POLY1305_BLOCK_SIZE);
tohash = ctr;
tohash_len = 0;
actx->len.aad = EVP_AEAD_TLS1_AAD_LEN;
actx->len.text = plen;
if (ctx->encrypt) {
ChaCha20_ctr32(out, in, plen, actx->key.key.d, actx->key.counter);
Poly1305_Update(POLY1305_ctx(actx), out, plen);
} else {
Poly1305_Update(POLY1305_ctx(actx), in, plen);
ChaCha20_ctr32(out, in, plen, actx->key.key.d, actx->key.counter);
}
in += plen;
out += plen;
tail = (0 - plen) & (POLY1305_BLOCK_SIZE - 1);
Poly1305_Update(POLY1305_ctx(actx), zero, tail);
}
{
const union {
long one;
char little;
} is_endian = { 1 };
if (is_endian.little) {
memcpy(ctr, (unsigned char *)&actx->len, POLY1305_BLOCK_SIZE);
} else {
ctr[0] = (unsigned char)(actx->len.aad);
ctr[1] = (unsigned char)(actx->len.aad>>8);
ctr[2] = (unsigned char)(actx->len.aad>>16);
ctr[3] = (unsigned char)(actx->len.aad>>24);
ctr[4] = (unsigned char)(actx->len.aad>>32);
ctr[5] = (unsigned char)(actx->len.aad>>40);
ctr[6] = (unsigned char)(actx->len.aad>>48);
ctr[7] = (unsigned char)(actx->len.aad>>56);
ctr[8] = (unsigned char)(actx->len.text);
ctr[9] = (unsigned char)(actx->len.text>>8);
ctr[10] = (unsigned char)(actx->len.text>>16);
ctr[11] = (unsigned char)(actx->len.text>>24);
ctr[12] = (unsigned char)(actx->len.text>>32);
ctr[13] = (unsigned char)(actx->len.text>>40);
ctr[14] = (unsigned char)(actx->len.text>>48);
ctr[15] = (unsigned char)(actx->len.text>>56);
}
tohash_len += POLY1305_BLOCK_SIZE;
}
Poly1305_Update(POLY1305_ctx(actx), tohash, tohash_len);
OPENSSL_cleanse(buf, buf_len);
Poly1305_Final(POLY1305_ctx(actx), ctx->encrypt ? actx->tag
: tohash);
actx->tls_payload_length = NO_TLS_PAYLOAD_LENGTH;
if (ctx->encrypt) {
memcpy(out, actx->tag, POLY1305_BLOCK_SIZE);
} else {
if (CRYPTO_memcmp(tohash, in, POLY1305_BLOCK_SIZE)) {
memset(out - (len - POLY1305_BLOCK_SIZE), 0,
len - POLY1305_BLOCK_SIZE);
return -1;
}
}
return len;
}
# else
static const unsigned char zero[CHACHA_BLK_SIZE] = { 0 };
# endif
static int chacha20_poly1305_cipher(EVP_CIPHER_CTX *ctx, unsigned char *out,
const unsigned char *in, size_t len)
{
EVP_CHACHA_AEAD_CTX *actx = aead_data(ctx);
size_t rem, plen = actx->tls_payload_length;
if (!actx->mac_inited) {
# if !defined(OPENSSL_SMALL_FOOTPRINT)
if (plen != NO_TLS_PAYLOAD_LENGTH && out != NULL)
return chacha20_poly1305_tls_cipher(ctx, out, in, len);
# endif
actx->key.counter[0] = 0;
ChaCha20_ctr32(actx->key.buf, zero, CHACHA_BLK_SIZE,
actx->key.key.d, actx->key.counter);
Poly1305_Init(POLY1305_ctx(actx), actx->key.buf);
actx->key.counter[0] = 1;
actx->key.partial_len = 0;
actx->len.aad = actx->len.text = 0;
actx->mac_inited = 1;
if (plen != NO_TLS_PAYLOAD_LENGTH) {
Poly1305_Update(POLY1305_ctx(actx), actx->tls_aad,
EVP_AEAD_TLS1_AAD_LEN);
actx->len.aad = EVP_AEAD_TLS1_AAD_LEN;
actx->aad = 1;
}
}
if (in) { /* aad or text */
if (out == NULL) { /* aad */
Poly1305_Update(POLY1305_ctx(actx), in, len);
actx->len.aad += len;
actx->aad = 1;
return len;
} else { /* plain- or ciphertext */
if (actx->aad) { /* wrap up aad */
if ((rem = (size_t)actx->len.aad % POLY1305_BLOCK_SIZE))
Poly1305_Update(POLY1305_ctx(actx), zero,
POLY1305_BLOCK_SIZE - rem);
actx->aad = 0;
}
actx->tls_payload_length = NO_TLS_PAYLOAD_LENGTH;
if (plen == NO_TLS_PAYLOAD_LENGTH)
plen = len;
else if (len != plen + POLY1305_BLOCK_SIZE)
return -1;
if (ctx->encrypt) { /* plaintext */
chacha_cipher(ctx, out, in, plen);
Poly1305_Update(POLY1305_ctx(actx), out, plen);
in += plen;
out += plen;
actx->len.text += plen;
} else { /* ciphertext */
Poly1305_Update(POLY1305_ctx(actx), in, plen);
chacha_cipher(ctx, out, in, plen);
in += plen;
out += plen;
actx->len.text += plen;
}
}
}
if (in == NULL /* explicit final */
|| plen != len) { /* or tls mode */
const union {
long one;
char little;
} is_endian = { 1 };
unsigned char temp[POLY1305_BLOCK_SIZE];
if (actx->aad) { /* wrap up aad */
if ((rem = (size_t)actx->len.aad % POLY1305_BLOCK_SIZE))
Poly1305_Update(POLY1305_ctx(actx), zero,
POLY1305_BLOCK_SIZE - rem);
actx->aad = 0;
}
if ((rem = (size_t)actx->len.text % POLY1305_BLOCK_SIZE))
Poly1305_Update(POLY1305_ctx(actx), zero,
POLY1305_BLOCK_SIZE - rem);
if (is_endian.little) {
Poly1305_Update(POLY1305_ctx(actx),
(unsigned char *)&actx->len, POLY1305_BLOCK_SIZE);
} else {
temp[0] = (unsigned char)(actx->len.aad);
temp[1] = (unsigned char)(actx->len.aad>>8);
temp[2] = (unsigned char)(actx->len.aad>>16);
temp[3] = (unsigned char)(actx->len.aad>>24);
temp[4] = (unsigned char)(actx->len.aad>>32);
temp[5] = (unsigned char)(actx->len.aad>>40);
temp[6] = (unsigned char)(actx->len.aad>>48);
temp[7] = (unsigned char)(actx->len.aad>>56);
temp[8] = (unsigned char)(actx->len.text);
temp[9] = (unsigned char)(actx->len.text>>8);
temp[10] = (unsigned char)(actx->len.text>>16);
temp[11] = (unsigned char)(actx->len.text>>24);
temp[12] = (unsigned char)(actx->len.text>>32);
temp[13] = (unsigned char)(actx->len.text>>40);
temp[14] = (unsigned char)(actx->len.text>>48);
temp[15] = (unsigned char)(actx->len.text>>56);
Poly1305_Update(POLY1305_ctx(actx), temp, POLY1305_BLOCK_SIZE);
}
Poly1305_Final(POLY1305_ctx(actx), ctx->encrypt ? actx->tag
: temp);
actx->mac_inited = 0;
if (in != NULL && len != plen) { /* tls mode */
if (ctx->encrypt) {
memcpy(out, actx->tag, POLY1305_BLOCK_SIZE);
} else {
if (CRYPTO_memcmp(temp, in, POLY1305_BLOCK_SIZE)) {
memset(out - plen, 0, plen);
return -1;
}
}
}
else if (!ctx->encrypt) {
if (CRYPTO_memcmp(temp, actx->tag, actx->tag_len))
return -1;
}
}
return len;
}
static int chacha20_poly1305_cleanup(EVP_CIPHER_CTX *ctx)
{
EVP_CHACHA_AEAD_CTX *actx = aead_data(ctx);
if (actx)
OPENSSL_cleanse(ctx->cipher_data, sizeof(*actx) + Poly1305_ctx_size());
return 1;
}
static int chacha20_poly1305_ctrl(EVP_CIPHER_CTX *ctx, int type, int arg,
void *ptr)
{
EVP_CHACHA_AEAD_CTX *actx = aead_data(ctx);
switch(type) {
case EVP_CTRL_INIT:
if (actx == NULL)
actx = ctx->cipher_data
= OPENSSL_zalloc(sizeof(*actx) + Poly1305_ctx_size());
if (actx == NULL) {
EVPerr(EVP_F_CHACHA20_POLY1305_CTRL, EVP_R_INITIALIZATION_ERROR);
return 0;
}
actx->len.aad = 0;
actx->len.text = 0;
actx->aad = 0;
actx->mac_inited = 0;
actx->tag_len = 0;
actx->nonce_len = 12;
actx->tls_payload_length = NO_TLS_PAYLOAD_LENGTH;
memset(actx->tls_aad, 0, POLY1305_BLOCK_SIZE);
return 1;
case EVP_CTRL_COPY:
if (actx) {
EVP_CIPHER_CTX *dst = (EVP_CIPHER_CTX *)ptr;
dst->cipher_data =
OPENSSL_memdup(actx, sizeof(*actx) + Poly1305_ctx_size());
if (dst->cipher_data == NULL) {
EVPerr(EVP_F_CHACHA20_POLY1305_CTRL, EVP_R_COPY_ERROR);
return 0;
}
}
return 1;
case EVP_CTRL_AEAD_SET_IVLEN:
if (arg <= 0 || arg > CHACHA20_POLY1305_MAX_IVLEN)
return 0;
actx->nonce_len = arg;
return 1;
case EVP_CTRL_AEAD_SET_IV_FIXED:
if (arg != 12)
return 0;
actx->nonce[0] = actx->key.counter[1]
= CHACHA_U8TOU32((unsigned char *)ptr);
actx->nonce[1] = actx->key.counter[2]
= CHACHA_U8TOU32((unsigned char *)ptr+4);
actx->nonce[2] = actx->key.counter[3]
= CHACHA_U8TOU32((unsigned char *)ptr+8);
return 1;
case EVP_CTRL_AEAD_SET_TAG:
if (arg <= 0 || arg > POLY1305_BLOCK_SIZE)
return 0;
if (ptr != NULL) {
memcpy(actx->tag, ptr, arg);
actx->tag_len = arg;
}
return 1;
case EVP_CTRL_AEAD_GET_TAG:
if (arg <= 0 || arg > POLY1305_BLOCK_SIZE || !ctx->encrypt)
return 0;
memcpy(ptr, actx->tag, arg);
return 1;
case EVP_CTRL_AEAD_TLS1_AAD:
if (arg != EVP_AEAD_TLS1_AAD_LEN)
return 0;
{
unsigned int len;
unsigned char *aad = ptr;
memcpy(actx->tls_aad, ptr, EVP_AEAD_TLS1_AAD_LEN);
len = aad[EVP_AEAD_TLS1_AAD_LEN - 2] << 8 |
aad[EVP_AEAD_TLS1_AAD_LEN - 1];
aad = actx->tls_aad;
if (!ctx->encrypt) {
if (len < POLY1305_BLOCK_SIZE)
return 0;
len -= POLY1305_BLOCK_SIZE; /* discount attached tag */
aad[EVP_AEAD_TLS1_AAD_LEN - 2] = (unsigned char)(len >> 8);
aad[EVP_AEAD_TLS1_AAD_LEN - 1] = (unsigned char)len;
}
actx->tls_payload_length = len;
/*
* merge record sequence number as per RFC7905
*/
actx->key.counter[1] = actx->nonce[0];
actx->key.counter[2] = actx->nonce[1] ^ CHACHA_U8TOU32(aad);
actx->key.counter[3] = actx->nonce[2] ^ CHACHA_U8TOU32(aad+4);
actx->mac_inited = 0;
return POLY1305_BLOCK_SIZE; /* tag length */
}
case EVP_CTRL_AEAD_SET_MAC_KEY:
/* no-op */
return 1;
default:
return -1;
}
}
static EVP_CIPHER chacha20_poly1305 = {
NID_chacha20_poly1305,
1, /* block_size */
CHACHA_KEY_SIZE, /* key_len */
12, /* iv_len, 96-bit nonce in the context */
EVP_CIPH_FLAG_AEAD_CIPHER | EVP_CIPH_CUSTOM_IV |
EVP_CIPH_ALWAYS_CALL_INIT | EVP_CIPH_CTRL_INIT |
EVP_CIPH_CUSTOM_COPY | EVP_CIPH_FLAG_CUSTOM_CIPHER,
chacha20_poly1305_init_key,
chacha20_poly1305_cipher,
chacha20_poly1305_cleanup,
0, /* 0 moves context-specific structure allocation to ctrl */
NULL, /* set_asn1_parameters */
NULL, /* get_asn1_parameters */
chacha20_poly1305_ctrl,
NULL /* app_data */
};
const EVP_CIPHER *EVP_chacha20_poly1305(void)
{
return(&chacha20_poly1305);
}
# endif
#endif
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