/* salsa20.c - Bernstein's Salsa20 cipher
* Copyright (C) 2012 Simon Josefsson, Niels Möller
* Copyright (C) 2013 g10 Code GmbH
*
* This file is part of Libgcrypt.
*
* Libgcrypt is free software; you can redistribute it and/or modify
* it under the terms of the GNU Lesser general Public License as
* published by the Free Software Foundation; either version 2.1 of
* the License, or (at your option) any later version.
*
* Libgcrypt is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU Lesser General Public License for more details.
*
* You should have received a copy of the GNU Lesser General Public
* License along with this program; if not, see <http://www.gnu.org/licenses/>.
*
* For a description of the algorithm, see:
* http://cr.yp.to/snuffle/spec.pdf
* http://cr.yp.to/snuffle/design.pdf
*/
/* The code is based on the code in Nettle
(git commit id 9d2d8ddaee35b91a4e1a32ae77cba04bea3480e7)
which in turn is based on
salsa20-ref.c version 20051118
D. J. Bernstein
Public domain.
*/
#include <config.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include "types.h"
#include "g10lib.h"
#include "cipher.h"
#include "bufhelp.h"
/* USE_AMD64 indicates whether to compile with AMD64 code. */
#undef USE_AMD64
#if defined(__x86_64__) && (defined(HAVE_COMPATIBLE_GCC_AMD64_PLATFORM_AS) || \
defined(HAVE_COMPATIBLE_GCC_WIN64_PLATFORM_AS))
# define USE_AMD64 1
#endif
/* USE_ARM_NEON_ASM indicates whether to enable ARM NEON assembly code. */
#undef USE_ARM_NEON_ASM
#ifdef ENABLE_NEON_SUPPORT
# if defined(HAVE_ARM_ARCH_V6) && defined(__ARMEL__) \
&& defined(HAVE_COMPATIBLE_GCC_ARM_PLATFORM_AS) \
&& defined(HAVE_GCC_INLINE_ASM_NEON)
# define USE_ARM_NEON_ASM 1
# endif
#endif /*ENABLE_NEON_SUPPORT*/
#define SALSA20_MIN_KEY_SIZE 16 /* Bytes. */
#define SALSA20_MAX_KEY_SIZE 32 /* Bytes. */
#define SALSA20_BLOCK_SIZE 64 /* Bytes. */
#define SALSA20_IV_SIZE 8 /* Bytes. */
#define SALSA20_INPUT_LENGTH 16 /* Bytes. */
/* Number of rounds. The standard uses 20 rounds. In any case the
number of rounds must be even. */
#define SALSA20_ROUNDS 20
#define SALSA20R12_ROUNDS 12
struct SALSA20_context_s;
typedef unsigned int (*salsa20_core_t) (u32 *dst, struct SALSA20_context_s *ctx,
unsigned int rounds);
typedef void (* salsa20_keysetup_t)(struct SALSA20_context_s *ctx,
const byte *key, int keylen);
typedef void (* salsa20_ivsetup_t)(struct SALSA20_context_s *ctx,
const byte *iv);
typedef struct SALSA20_context_s
{
/* Indices 1-4 and 11-14 holds the key (two identical copies for the
shorter key size), indices 0, 5, 10, 15 are constant, indices 6, 7
are the IV, and indices 8, 9 are the block counter:
C K K K
K C I I
B B C K
K K K C
*/
u32 input[SALSA20_INPUT_LENGTH];
u32 pad[SALSA20_INPUT_LENGTH];
unsigned int unused; /* bytes in the pad. */
#ifdef USE_ARM_NEON_ASM
int use_neon;
#endif
salsa20_keysetup_t keysetup;
salsa20_ivsetup_t ivsetup;
salsa20_core_t core;
} SALSA20_context_t;
/* The masking of the right shift is needed to allow n == 0 (using
just 32 - n and 64 - n results in undefined behaviour). Most uses
of these macros use a constant and non-zero rotation count. */
#define ROTL32(n,x) (((x)<<(n)) | ((x)>>((-(n)&31))))
#define LE_SWAP32(v) le_bswap32(v)
#define LE_READ_UINT32(p) buf_get_le32(p)
static void salsa20_setiv (void *context, const byte *iv, size_t ivlen);
static const char *selftest (void);
#ifdef USE_AMD64
/* Assembly implementations use SystemV ABI, ABI conversion and additional
* stack to store XMM6-XMM15 needed on Win64. */
#ifdef HAVE_COMPATIBLE_GCC_WIN64_PLATFORM_AS
# define ASM_FUNC_ABI __attribute__((sysv_abi))
# define ASM_EXTRA_STACK (10 * 16)
#else
# define ASM_FUNC_ABI
# define ASM_EXTRA_STACK 0
#endif
/* AMD64 assembly implementations of Salsa20. */
void _gcry_salsa20_amd64_keysetup(u32 *ctxinput, const void *key, int keybits)
ASM_FUNC_ABI;
void _gcry_salsa20_amd64_ivsetup(u32 *ctxinput, const void *iv)
ASM_FUNC_ABI;
unsigned int
_gcry_salsa20_amd64_encrypt_blocks(u32 *ctxinput, const void *src, void *dst,
size_t len, int rounds) ASM_FUNC_ABI;
static void
salsa20_keysetup(SALSA20_context_t *ctx, const byte *key, int keylen)
{
_gcry_salsa20_amd64_keysetup(ctx->input, key, keylen * 8);
}
static void
salsa20_ivsetup(SALSA20_context_t *ctx, const byte *iv)
{
_gcry_salsa20_amd64_ivsetup(ctx->input, iv);
}
static unsigned int
salsa20_core (u32 *dst, SALSA20_context_t *ctx, unsigned int rounds)
{
memset(dst, 0, SALSA20_BLOCK_SIZE);
return _gcry_salsa20_amd64_encrypt_blocks(ctx->input, dst, dst, 1, rounds)
+ ASM_EXTRA_STACK;
}
#else /* USE_AMD64 */
#if 0
# define SALSA20_CORE_DEBUG(i) do { \
unsigned debug_j; \
for (debug_j = 0; debug_j < 16; debug_j++) \
{ \
if (debug_j == 0) \
fprintf(stderr, "%2d:", (i)); \
else if (debug_j % 4 == 0) \
fprintf(stderr, "\n "); \
fprintf(stderr, " %8x", pad[debug_j]); \
} \
fprintf(stderr, "\n"); \
} while (0)
#else
# define SALSA20_CORE_DEBUG(i)
#endif
#define QROUND(x0, x1, x2, x3) \
do { \
x1 ^= ROTL32 ( 7, x0 + x3); \
x2 ^= ROTL32 ( 9, x1 + x0); \
x3 ^= ROTL32 (13, x2 + x1); \
x0 ^= ROTL32 (18, x3 + x2); \
} while(0)
static unsigned int
salsa20_core (u32 *dst, SALSA20_context_t *ctx, unsigned rounds)
{
u32 pad[SALSA20_INPUT_LENGTH], *src = ctx->input;
unsigned int i;
memcpy (pad, src, sizeof(pad));
for (i = 0; i < rounds; i += 2)
{
SALSA20_CORE_DEBUG (i);
QROUND (pad[0], pad[4], pad[8], pad[12]);
QROUND (pad[5], pad[9], pad[13], pad[1] );
QROUND (pad[10], pad[14], pad[2], pad[6] );
QROUND (pad[15], pad[3], pad[7], pad[11]);
SALSA20_CORE_DEBUG (i+1);
QROUND (pad[0], pad[1], pad[2], pad[3] );
QROUND (pad[5], pad[6], pad[7], pad[4] );
QROUND (pad[10], pad[11], pad[8], pad[9] );
QROUND (pad[15], pad[12], pad[13], pad[14]);
}
SALSA20_CORE_DEBUG (i);
for (i = 0; i < SALSA20_INPUT_LENGTH; i++)
{
u32 t = pad[i] + src[i];
dst[i] = LE_SWAP32 (t);
}
/* Update counter. */
if (!++src[8])
src[9]++;
/* burn_stack */
return ( 3*sizeof (void*) \
+ 2*sizeof (void*) \
+ 64 \
+ sizeof (unsigned int) \
+ sizeof (u32) );
}
#undef QROUND
#undef SALSA20_CORE_DEBUG
static void
salsa20_keysetup(SALSA20_context_t *ctx, const byte *key, int keylen)
{
/* These constants are the little endian encoding of the string
"expand 32-byte k". For the 128 bit variant, the "32" in that
string will be fixed up to "16". */
ctx->input[0] = 0x61707865; /* "apxe" */
ctx->input[5] = 0x3320646e; /* "3 dn" */
ctx->input[10] = 0x79622d32; /* "yb-2" */
ctx->input[15] = 0x6b206574; /* "k et" */
ctx->input[1] = LE_READ_UINT32(key + 0);
ctx->input[2] = LE_READ_UINT32(key + 4);
ctx->input[3] = LE_READ_UINT32(key + 8);
ctx->input[4] = LE_READ_UINT32(key + 12);
if (keylen == SALSA20_MAX_KEY_SIZE) /* 256 bits */
{
ctx->input[11] = LE_READ_UINT32(key + 16);
ctx->input[12] = LE_READ_UINT32(key + 20);
ctx->input[13] = LE_READ_UINT32(key + 24);
ctx->input[14] = LE_READ_UINT32(key + 28);
}
else /* 128 bits */
{
ctx->input[11] = ctx->input[1];
ctx->input[12] = ctx->input[2];
ctx->input[13] = ctx->input[3];
ctx->input[14] = ctx->input[4];
ctx->input[5] -= 0x02000000; /* Change to "1 dn". */
ctx->input[10] += 0x00000004; /* Change to "yb-6". */
}
}
static void salsa20_ivsetup(SALSA20_context_t *ctx, const byte *iv)
{
ctx->input[6] = LE_READ_UINT32(iv + 0);
ctx->input[7] = LE_READ_UINT32(iv + 4);
/* Reset the block counter. */
ctx->input[8] = 0;
ctx->input[9] = 0;
}
#endif /*!USE_AMD64*/
#ifdef USE_ARM_NEON_ASM
/* ARM NEON implementation of Salsa20. */
unsigned int
_gcry_arm_neon_salsa20_encrypt(void *c, const void *m, unsigned int nblks,
void *k, unsigned int rounds);
static unsigned int
salsa20_core_neon (u32 *dst, SALSA20_context_t *ctx, unsigned int rounds)
{
return _gcry_arm_neon_salsa20_encrypt(dst, NULL, 1, ctx->input, rounds);
}
static void salsa20_ivsetup_neon(SALSA20_context_t *ctx, const byte *iv)
{
memcpy(ctx->input + 8, iv, 8);
/* Reset the block counter. */
memset(ctx->input + 10, 0, 8);
}
static void
salsa20_keysetup_neon(SALSA20_context_t *ctx, const byte *key, int klen)
{
static const unsigned char sigma32[16] = "expand 32-byte k";
static const unsigned char sigma16[16] = "expand 16-byte k";
if (klen == 16)
{
memcpy (ctx->input, key, 16);
memcpy (ctx->input + 4, key, 16); /* Duplicate 128-bit key. */
memcpy (ctx->input + 12, sigma16, 16);
}
else
{
/* 32-byte key */
memcpy (ctx->input, key, 32);
memcpy (ctx->input + 12, sigma32, 16);
}
}
#endif /*USE_ARM_NEON_ASM*/
static gcry_err_code_t
salsa20_do_setkey (SALSA20_context_t *ctx,
const byte *key, unsigned int keylen)
{
static int initialized;
static const char *selftest_failed;
if (!initialized )
{
initialized = 1;
selftest_failed = selftest ();
if (selftest_failed)
log_error ("SALSA20 selftest failed (%s)\n", selftest_failed );
}
if (selftest_failed)
return GPG_ERR_SELFTEST_FAILED;
if (keylen != SALSA20_MIN_KEY_SIZE
&& keylen != SALSA20_MAX_KEY_SIZE)
return GPG_ERR_INV_KEYLEN;
/* Default ops. */
ctx->keysetup = salsa20_keysetup;
ctx->ivsetup = salsa20_ivsetup;
ctx->core = salsa20_core;
#ifdef USE_ARM_NEON_ASM
ctx->use_neon = (_gcry_get_hw_features () & HWF_ARM_NEON) != 0;
if (ctx->use_neon)
{
/* Use ARM NEON ops instead. */
ctx->keysetup = salsa20_keysetup_neon;
ctx->ivsetup = salsa20_ivsetup_neon;
ctx->core = salsa20_core_neon;
}
#endif
ctx->keysetup (ctx, key, keylen);
/* We default to a zero nonce. */
salsa20_setiv (ctx, NULL, 0);
return 0;
}
static gcry_err_code_t
salsa20_setkey (void *context, const byte *key, unsigned int keylen)
{
SALSA20_context_t *ctx = (SALSA20_context_t *)context;
gcry_err_code_t rc = salsa20_do_setkey (ctx, key, keylen);
_gcry_burn_stack (4 + sizeof (void *) + 4 * sizeof (void *));
return rc;
}
static void
salsa20_setiv (void *context, const byte *iv, size_t ivlen)
{
SALSA20_context_t *ctx = (SALSA20_context_t *)context;
byte tmp[SALSA20_IV_SIZE];
if (iv && ivlen != SALSA20_IV_SIZE)
log_info ("WARNING: salsa20_setiv: bad ivlen=%u\n", (u32)ivlen);
if (!iv || ivlen != SALSA20_IV_SIZE)
memset (tmp, 0, sizeof(tmp));
else
memcpy (tmp, iv, SALSA20_IV_SIZE);
ctx->ivsetup (ctx, tmp);
/* Reset the unused pad bytes counter. */
ctx->unused = 0;
wipememory (tmp, sizeof(tmp));
}
/* Note: This function requires LENGTH > 0. */
static void
salsa20_do_encrypt_stream (SALSA20_context_t *ctx,
byte *outbuf, const byte *inbuf,
size_t length, unsigned rounds)
{
unsigned int nburn, burn = 0;
if (ctx->unused)
{
unsigned char *p = (void*)ctx->pad;
size_t n;
gcry_assert (ctx->unused < SALSA20_BLOCK_SIZE);
n = ctx->unused;
if (n > length)
n = length;
buf_xor (outbuf, inbuf, p + SALSA20_BLOCK_SIZE - ctx->unused, n);
length -= n;
outbuf += n;
inbuf += n;
ctx->unused -= n;
if (!length)
return;
gcry_assert (!ctx->unused);
}
#ifdef USE_AMD64
if (length >= SALSA20_BLOCK_SIZE)
{
size_t nblocks = length / SALSA20_BLOCK_SIZE;
burn = _gcry_salsa20_amd64_encrypt_blocks(ctx->input, inbuf, outbuf,
nblocks, rounds);
burn += ASM_EXTRA_STACK;
length -= SALSA20_BLOCK_SIZE * nblocks;
outbuf += SALSA20_BLOCK_SIZE * nblocks;
inbuf += SALSA20_BLOCK_SIZE * nblocks;
}
#endif
#ifdef USE_ARM_NEON_ASM
if (ctx->use_neon && length >= SALSA20_BLOCK_SIZE)
{
unsigned int nblocks = length / SALSA20_BLOCK_SIZE;
_gcry_arm_neon_salsa20_encrypt (outbuf, inbuf, nblocks, ctx->input,
rounds);
length -= SALSA20_BLOCK_SIZE * nblocks;
outbuf += SALSA20_BLOCK_SIZE * nblocks;
inbuf += SALSA20_BLOCK_SIZE * nblocks;
}
#endif
while (length > 0)
{
/* Create the next pad and bump the block counter. Note that it
is the user's duty to change to another nonce not later than
after 2^70 processed bytes. */
nburn = ctx->core (ctx->pad, ctx, rounds);
burn = nburn > burn ? nburn : burn;
if (length <= SALSA20_BLOCK_SIZE)
{
buf_xor (outbuf, inbuf, ctx->pad, length);
ctx->unused = SALSA20_BLOCK_SIZE - length;
break;
}
buf_xor (outbuf, inbuf, ctx->pad, SALSA20_BLOCK_SIZE);
length -= SALSA20_BLOCK_SIZE;
outbuf += SALSA20_BLOCK_SIZE;
inbuf += SALSA20_BLOCK_SIZE;
}
_gcry_burn_stack (burn);
}
static void
salsa20_encrypt_stream (void *context,
byte *outbuf, const byte *inbuf, size_t length)
{
SALSA20_context_t *ctx = (SALSA20_context_t *)context;
if (length)
salsa20_do_encrypt_stream (ctx, outbuf, inbuf, length, SALSA20_ROUNDS);
}
static void
salsa20r12_encrypt_stream (void *context,
byte *outbuf, const byte *inbuf, size_t length)
{
SALSA20_context_t *ctx = (SALSA20_context_t *)context;
if (length)
salsa20_do_encrypt_stream (ctx, outbuf, inbuf, length, SALSA20R12_ROUNDS);
}
static const char*
selftest (void)
{
byte ctxbuf[sizeof(SALSA20_context_t) + 15];
SALSA20_context_t *ctx;
byte scratch[8+1];
byte buf[256+64+4];
int i;
static byte key_1[] =
{ 0x80, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00 };
static const byte nonce_1[] =
{ 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00 };
static const byte plaintext_1[] =
{ 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00 };
static const byte ciphertext_1[] =
{ 0xE3, 0xBE, 0x8F, 0xDD, 0x8B, 0xEC, 0xA2, 0xE3};
/* 16-byte alignment required for amd64 implementation. */
ctx = (SALSA20_context_t *)((uintptr_t)(ctxbuf + 15) & ~(uintptr_t)15);
salsa20_setkey (ctx, key_1, sizeof key_1);
salsa20_setiv (ctx, nonce_1, sizeof nonce_1);
scratch[8] = 0;
salsa20_encrypt_stream (ctx, scratch, plaintext_1, sizeof plaintext_1);
if (memcmp (scratch, ciphertext_1, sizeof ciphertext_1))
return "Salsa20 encryption test 1 failed.";
if (scratch[8])
return "Salsa20 wrote too much.";
salsa20_setkey( ctx, key_1, sizeof(key_1));
salsa20_setiv (ctx, nonce_1, sizeof nonce_1);
salsa20_encrypt_stream (ctx, scratch, scratch, sizeof plaintext_1);
if (memcmp (scratch, plaintext_1, sizeof plaintext_1))
return "Salsa20 decryption test 1 failed.";
for (i = 0; i < sizeof buf; i++)
buf[i] = i;
salsa20_setkey (ctx, key_1, sizeof key_1);
salsa20_setiv (ctx, nonce_1, sizeof nonce_1);
/*encrypt*/
salsa20_encrypt_stream (ctx, buf, buf, sizeof buf);
/*decrypt*/
salsa20_setkey (ctx, key_1, sizeof key_1);
salsa20_setiv (ctx, nonce_1, sizeof nonce_1);
salsa20_encrypt_stream (ctx, buf, buf, 1);
salsa20_encrypt_stream (ctx, buf+1, buf+1, (sizeof buf)-1-1);
salsa20_encrypt_stream (ctx, buf+(sizeof buf)-1, buf+(sizeof buf)-1, 1);
for (i = 0; i < sizeof buf; i++)
if (buf[i] != (byte)i)
return "Salsa20 encryption test 2 failed.";
return NULL;
}
gcry_cipher_spec_t _gcry_cipher_spec_salsa20 =
{
GCRY_CIPHER_SALSA20,
{0, 0}, /* flags */
"SALSA20", /* name */
NULL, /* aliases */
NULL, /* oids */
1, /* blocksize in bytes. */
SALSA20_MAX_KEY_SIZE*8, /* standard key length in bits. */
sizeof (SALSA20_context_t),
salsa20_setkey,
NULL,
NULL,
salsa20_encrypt_stream,
salsa20_encrypt_stream,
NULL,
NULL,
salsa20_setiv
};
gcry_cipher_spec_t _gcry_cipher_spec_salsa20r12 =
{
GCRY_CIPHER_SALSA20R12,
{0, 0}, /* flags */
"SALSA20R12", /* name */
NULL, /* aliases */
NULL, /* oids */
1, /* blocksize in bytes. */
SALSA20_MAX_KEY_SIZE*8, /* standard key length in bits. */
sizeof (SALSA20_context_t),
salsa20_setkey,
NULL,
NULL,
salsa20r12_encrypt_stream,
salsa20r12_encrypt_stream,
NULL,
NULL,
salsa20_setiv
};