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gcm.c 14.21 KiB
/* gcm.h
*
* Galois counter mode, specified by NIST,
* http://csrc.nist.gov/publications/nistpubs/800-38D/SP-800-38D.pdf
*
* See also the gcm paper at
* http://www.cryptobarn.com/papers/gcm-spec.pdf.
*/
/* NOTE: Tentative interface, subject to change. No effort will be
made to avoid incompatible changes. */
/* nettle, low-level cryptographics library
*
* Copyright (C) 2011 Niels Möller
* Copyright (C) 2011 Katholieke Universiteit Leuven
*
* Contributed by Nikos Mavrogiannopoulos
*
* The nettle library 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.
*
* The nettle library 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 the nettle library; see the file COPYING.LIB. If not, write to
* the Free Software Foundation, Inc., 59 Temple Place - Suite 330, Boston,
* MA 02111-1307, USA.
*/
#if HAVE_CONFIG_H
# include "config.h"
#endif
#include <assert.h>
#include <stdlib.h>
#include <string.h>
#include "gcm.h"
#include "memxor.h"
#include "nettle-internal.h"
#include "macros.h"
#define GHASH_POLYNOMIAL 0xE1UL
static void
gcm_gf_add (union gcm_block *r, const union gcm_block *x, const union gcm_block *y)
{
r->w[0] = x->w[0] ^ y->w[0];
r->w[1] = x->w[1] ^ y->w[1];
#if SIZEOF_LONG == 4
r->w[2] = x->w[2] ^ y->w[2];
r->w[3] = x->w[3] ^ y->w[3];
#endif
}
/* Multiplication by 010...0; a big-endian shift right. If the bit
shifted out is one, the defining polynomial is added to cancel it
out. r == x is allowed. */
static void
gcm_gf_shift (union gcm_block *r, const union gcm_block *x)
{
long mask;
/* Shift uses big-endian representation. */
#if WORDS_BIGENDIAN
# if SIZEOF_LONG == 4
mask = - (x->w[3] & 1);
r->w[3] = (x->w[3] >> 1) | ((x->w[2] & 1) << 31);
r->w[2] = (x->w[2] >> 1) | ((x->w[1] & 1) << 31);
r->w[1] = (x->w[1] >> 1) | ((x->w[0] & 1) << 31);
r->w[0] = (x->w[0] >> 1) ^ (mask & (GHASH_POLYNOMIAL << 24));
# elif SIZEOF_LONG == 8
mask = - (x->w[1] & 1);
r->w[1] = (x->w[1] >> 1) | ((x->w[0] & 1) << 63);
r->w[0] = (x->w[0] >> 1) ^ (mask & (GHASH_POLYNOMIAL << 56));
# else
# error Unsupported word size. */
#endif
#else /* ! WORDS_BIGENDIAN */
# if SIZEOF_LONG == 4
#define RSHIFT_WORD(x) \
((((x) & 0xfefefefeUL) >> 1) \
| (((x) & 0x00010101) << 15))
mask = - ((x->w[3] >> 24) & 1);
r->w[3] = RSHIFT_WORD(x->w[3]) | ((x->w[2] >> 17) & 0x80);
r->w[2] = RSHIFT_WORD(x->w[2]) | ((x->w[1] >> 17) & 0x80);
r->w[1] = RSHIFT_WORD(x->w[1]) | ((x->w[0] >> 17) & 0x80);
r->w[0] = RSHIFT_WORD(x->w[0]) ^ (mask & GHASH_POLYNOMIAL);
# elif SIZEOF_LONG == 8
#define RSHIFT_WORD(x) \
((((x) & 0xfefefefefefefefeUL) >> 1) \
| (((x) & 0x0001010101010101UL) << 15))
mask = - ((x->w[1] >> 56) & 1);
r->w[1] = RSHIFT_WORD(x->w[1]) | ((x->w[0] >> 49) & 0x80);
r->w[0] = RSHIFT_WORD(x->w[0]) ^ (mask & GHASH_POLYNOMIAL);
# else
# error Unsupported word size. */
# endif
# undef RSHIFT_WORD
#endif /* ! WORDS_BIGENDIAN */
}
#if GCM_TABLE_BITS == 0
/* Sets x <- x * y mod r, using the plain bitwise algorithm from the
specification. y may be shorter than a full block, missing bytes
are assumed zero. */
static void
gcm_gf_mul (union gcm_block *x, const union gcm_block *y)
{
union gcm_block V;
union gcm_block Z;
unsigned i;
memcpy(V.b, x, sizeof(V));
memset(Z.b, 0, sizeof(Z));
for (i = 0; i < GCM_BLOCK_SIZE; i++)
{
uint8_t b = y->b[i];
unsigned j;
for (j = 0; j < 8; j++, b <<= 1)
{
if (b & 0x80)
gcm_gf_add(&Z, &Z, &V);
gcm_gf_shift(&V, &V);
}
}
memcpy (x->b, Z.b, sizeof(Z));
}
#else /* GCM_TABLE_BITS != 0 */
# if WORDS_BIGENDIAN
# define W(left,right) (0x##left##right)
# else
# define W(left,right) (0x##right##left)
# endif
# if GCM_TABLE_BITS == 4
static const uint16_t
shift_table[0x10] = {
W(00,00),W(1c,20),W(38,40),W(24,60),W(70,80),W(6c,a0),W(48,c0),W(54,e0),
W(e1,00),W(fd,20),W(d9,40),W(c5,60),W(91,80),W(8d,a0),W(a9,c0),W(b5,e0),
};
static void
gcm_gf_shift_4(union gcm_block *x)
{
unsigned long *w = x->w;
unsigned long reduce;
/* Shift uses big-endian representation. */
#if WORDS_BIGENDIAN
# if SIZEOF_LONG == 4
reduce = shift_table[w[3] & 0xf];
w[3] = (w[3] >> 4) | ((w[2] & 0xf) << 28);
w[2] = (w[2] >> 4) | ((w[1] & 0xf) << 28);
w[1] = (w[1] >> 4) | ((w[0] & 0xf) << 28);
w[0] = (w[0] >> 4) ^ (reduce << 16);
# elif SIZEOF_LONG == 8
reduce = shift_table[w[1] & 0xf];
w[1] = (w[1] >> 4) | ((w[0] & 0xf) << 60);
w[0] = (w[0] >> 4) ^ (reduce << 48);
# else
# error Unsupported word size. */
#endif
#else /* ! WORDS_BIGENDIAN */
# if SIZEOF_LONG == 4
#define RSHIFT_WORD(x) \
((((x) & 0xf0f0f0f0UL) >> 4) \
| (((x) & 0x000f0f0f) << 12))
reduce = shift_table[(w[3] >> 24) & 0xf];
w[3] = RSHIFT_WORD(w[3]) | ((w[2] >> 20) & 0xf0);
w[2] = RSHIFT_WORD(w[2]) | ((w[1] >> 20) & 0xf0);
w[1] = RSHIFT_WORD(w[1]) | ((w[0] >> 20) & 0xf0);
w[0] = RSHIFT_WORD(w[0]) ^ reduce;
# elif SIZEOF_LONG == 8
#define RSHIFT_WORD(x) \
((((x) & 0xf0f0f0f0f0f0f0f0UL) >> 4) \
| (((x) & 0x000f0f0f0f0f0f0fUL) << 12))
reduce = shift_table[(w[1] >> 56) & 0xf];
w[1] = RSHIFT_WORD(w[1]) | ((w[0] >> 52) & 0xf0);
w[0] = RSHIFT_WORD(w[0]) ^ reduce;
# else
# error Unsupported word size. */
# endif
# undef RSHIFT_WORD
#endif /* ! WORDS_BIGENDIAN */
}
static void
gcm_gf_mul (union gcm_block *x, const union gcm_block *table)
{
union gcm_block Z;
unsigned i;
memset(Z.b, 0, sizeof(Z));
for (i = GCM_BLOCK_SIZE; i-- > 0;)
{
uint8_t b = x->b[i];
gcm_gf_shift_4(&Z);
gcm_gf_add(&Z, &Z, &table[b & 0xf]);
gcm_gf_shift_4(&Z);
gcm_gf_add(&Z, &Z, &table[b >> 4]);
}
memcpy (x->b, Z.b, sizeof(Z));
}
# elif GCM_TABLE_BITS == 8
static const uint16_t
shift_table[0x100] = {
W(00,00),W(01,c2),W(03,84),W(02,46),W(07,08),W(06,ca),W(04,8c),W(05,4e),
W(0e,10),W(0f,d2),W(0d,94),W(0c,56),W(09,18),W(08,da),W(0a,9c),W(0b,5e),
W(1c,20),W(1d,e2),W(1f,a4),W(1e,66),W(1b,28),W(1a,ea),W(18,ac),W(19,6e),
W(12,30),W(13,f2),W(11,b4),W(10,76),W(15,38),W(14,fa),W(16,bc),W(17,7e),
W(38,40),W(39,82),W(3b,c4),W(3a,06),W(3f,48),W(3e,8a),W(3c,cc),W(3d,0e),
W(36,50),W(37,92),W(35,d4),W(34,16),W(31,58),W(30,9a),W(32,dc),W(33,1e),
W(24,60),W(25,a2),W(27,e4),W(26,26),W(23,68),W(22,aa),W(20,ec),W(21,2e),
W(2a,70),W(2b,b2),W(29,f4),W(28,36),W(2d,78),W(2c,ba),W(2e,fc),W(2f,3e),
W(70,80),W(71,42),W(73,04),W(72,c6),W(77,88),W(76,4a),W(74,0c),W(75,ce),
W(7e,90),W(7f,52),W(7d,14),W(7c,d6),W(79,98),W(78,5a),W(7a,1c),W(7b,de),
W(6c,a0),W(6d,62),W(6f,24),W(6e,e6),W(6b,a8),W(6a,6a),W(68,2c),W(69,ee),
W(62,b0),W(63,72),W(61,34),W(60,f6),W(65,b8),W(64,7a),W(66,3c),W(67,fe),
W(48,c0),W(49,02),W(4b,44),W(4a,86),W(4f,c8),W(4e,0a),W(4c,4c),W(4d,8e),
W(46,d0),W(47,12),W(45,54),W(44,96),W(41,d8),W(40,1a),W(42,5c),W(43,9e),
W(54,e0),W(55,22),W(57,64),W(56,a6),W(53,e8),W(52,2a),W(50,6c),W(51,ae),
W(5a,f0),W(5b,32),W(59,74),W(58,b6),W(5d,f8),W(5c,3a),W(5e,7c),W(5f,be),
W(e1,00),W(e0,c2),W(e2,84),W(e3,46),W(e6,08),W(e7,ca),W(e5,8c),W(e4,4e),
W(ef,10),W(ee,d2),W(ec,94),W(ed,56),W(e8,18),W(e9,da),W(eb,9c),W(ea,5e),
W(fd,20),W(fc,e2),W(fe,a4),W(ff,66),W(fa,28),W(fb,ea),W(f9,ac),W(f8,6e),
W(f3,30),W(f2,f2),W(f0,b4),W(f1,76),W(f4,38),W(f5,fa),W(f7,bc),W(f6,7e),
W(d9,40),W(d8,82),W(da,c4),W(db,06),W(de,48),W(df,8a),W(dd,cc),W(dc,0e),
W(d7,50),W(d6,92),W(d4,d4),W(d5,16),W(d0,58),W(d1,9a),W(d3,dc),W(d2,1e),
W(c5,60),W(c4,a2),W(c6,e4),W(c7,26),W(c2,68),W(c3,aa),W(c1,ec),W(c0,2e),
W(cb,70),W(ca,b2),W(c8,f4),W(c9,36),W(cc,78),W(cd,ba),W(cf,fc),W(ce,3e),
W(91,80),W(90,42),W(92,04),W(93,c6),W(96,88),W(97,4a),W(95,0c),W(94,ce),
W(9f,90),W(9e,52),W(9c,14),W(9d,d6),W(98,98),W(99,5a),W(9b,1c),W(9a,de),
W(8d,a0),W(8c,62),W(8e,24),W(8f,e6),W(8a,a8),W(8b,6a),W(89,2c),W(88,ee),
W(83,b0),W(82,72),W(80,34),W(81,f6),W(84,b8),W(85,7a),W(87,3c),W(86,fe),
W(a9,c0),W(a8,02),W(aa,44),W(ab,86),W(ae,c8),W(af,0a),W(ad,4c),W(ac,8e),
W(a7,d0),W(a6,12),W(a4,54),W(a5,96),W(a0,d8),W(a1,1a),W(a3,5c),W(a2,9e),
W(b5,e0),W(b4,22),W(b6,64),W(b7,a6),W(b2,e8),W(b3,2a),W(b1,6c),W(b0,ae),
W(bb,f0),W(ba,32),W(b8,74),W(b9,b6),W(bc,f8),W(bd,3a),W(bf,7c),W(be,be),
};
static void
gcm_gf_shift_8(union gcm_block *x)
{
unsigned long *w = x->w;
unsigned long reduce;
/* Shift uses big-endian representation. */
#if WORDS_BIGENDIAN
# if SIZEOF_LONG == 4
reduce = shift_table[w[3] & 0xff];
w[3] = (w[3] >> 8) | ((w[2] & 0xff) << 24);
w[2] = (w[2] >> 8) | ((w[1] & 0xff) << 24);
w[1] = (w[1] >> 8) | ((w[0] & 0xff) << 24);
w[0] = (w[0] >> 8) ^ (reduce << 16);
# elif SIZEOF_LONG == 8
reduce = shift_table[w[1] & 0xff];
w[1] = (w[1] >> 8) | ((w[0] & 0xff) << 56);
w[0] = (w[0] >> 8) ^ (reduce << 48);
# else
# error Unsupported word size. */
#endif
#else /* ! WORDS_BIGENDIAN */
# if SIZEOF_LONG == 4
reduce = shift_table[(w[3] >> 24) & 0xff];
w[3] = (w[3] << 8) | (w[2] >> 24);
w[2] = (w[2] << 8) | (w[1] >> 24);
w[1] = (w[1] << 8) | (w[0] >> 24);
w[0] = (w[0] << 8) ^ reduce;
# elif SIZEOF_LONG == 8
reduce = shift_table[(w[1] >> 56) & 0xff];
w[1] = (w[1] << 8) | (w[0] >> 56);
w[0] = (w[0] << 8) ^ reduce;
# else
# error Unsupported word size. */
# endif
#endif /* ! WORDS_BIGENDIAN */
}
static void
gcm_gf_mul (union gcm_block *x, const union gcm_block *table)
{
union gcm_block Z;
unsigned i;
memcpy(Z.b, table[x->b[GCM_BLOCK_SIZE-1]].b, GCM_BLOCK_SIZE);
for (i = GCM_BLOCK_SIZE-2; i > 0; i--)
{
gcm_gf_shift_8(&Z);
gcm_gf_add(&Z, &Z, &table[x->b[i]]);
}
gcm_gf_shift_8(&Z);
gcm_gf_add(x, &Z, &table[x->b[0]]);
}
# else /* GCM_TABLE_BITS != 8 */
# error Unsupported table size.
# endif /* GCM_TABLE_BITS != 8 */
#undef W
#endif /* GCM_TABLE_BITS */
/* Increment the rightmost 32 bits. */
#define INC32(block) INCREMENT(4, (block.b) + GCM_BLOCK_SIZE - 4)
/* Initialization of GCM.
* @ctx: The context of GCM
* @cipher: The context of the underlying block cipher
* @f: The underlying cipher encryption function
*/
void
gcm_set_key(struct gcm_key *key,
void *cipher, nettle_crypt_func f)
{
/* Middle element if GCM_TABLE_BITS > 0, otherwise the first
element */
unsigned i = (1<<GCM_TABLE_BITS)/2;
/* H */
memset(key->h[0].b, 0, GCM_BLOCK_SIZE);
f (cipher, GCM_BLOCK_SIZE, key->h[i].b, key->h[0].b);
#if GCM_TABLE_BITS
/* Algorithm 3 from the gcm paper. First do powers of two, then do
the rest by adding. */
while (i /= 2)
gcm_gf_shift(&key->h[i], &key->h[2*i]);
for (i = 2; i < 1<<GCM_TABLE_BITS; i *= 2)
{
unsigned j;
for (j = 1; j < i; j++)
gcm_gf_add(&key->h[i+j], &key->h[i],&key->h[j]);
}
#endif
}
/*
* @length: The size of the iv (fixed for now to GCM_NONCE_SIZE)
* @iv: The iv
*/
void
gcm_set_iv(struct gcm_ctx *ctx, unsigned length, const uint8_t* iv)
{
/* FIXME: remove the iv size limitation */
assert (length == GCM_IV_SIZE);
memcpy (ctx->iv.b, iv, GCM_BLOCK_SIZE - 4);
ctx->iv.b[GCM_BLOCK_SIZE - 4] = 0;
ctx->iv.b[GCM_BLOCK_SIZE - 3] = 0;
ctx->iv.b[GCM_BLOCK_SIZE - 2] = 0;
ctx->iv.b[GCM_BLOCK_SIZE - 1] = 1;
memcpy (ctx->ctr.b, ctx->iv.b, GCM_BLOCK_SIZE);
INC32 (ctx->ctr);
/* Reset the rest of the message-dependent state. */
memset(ctx->x.b, 0, sizeof(ctx->x));
ctx->auth_size = ctx->data_size = 0;
}
static void
gcm_hash(const struct gcm_key *key, union gcm_block *x,
unsigned length, const uint8_t *data)
{
for (; length >= GCM_BLOCK_SIZE;
length -= GCM_BLOCK_SIZE, data += GCM_BLOCK_SIZE)
{
memxor (x->b, data, GCM_BLOCK_SIZE);
gcm_gf_mul (x, key->h);
}
if (length > 0)
{
memxor (x->b, data, length);
gcm_gf_mul (x, key->h);
}
}
void
gcm_auth(struct gcm_ctx *ctx, const struct gcm_key *key,
unsigned length, const uint8_t *data)
{
assert(ctx->auth_size % GCM_BLOCK_SIZE == 0);
assert(ctx->data_size % GCM_BLOCK_SIZE == 0);
gcm_hash(key, &ctx->x, length, data);
ctx->auth_size += length;
}
static void
gcm_crypt(struct gcm_ctx *ctx, void *cipher, nettle_crypt_func *f,
unsigned length, uint8_t *dst, const uint8_t *src)
{
uint8_t buffer[GCM_BLOCK_SIZE];
if (src != dst)
{
for (; length >= GCM_BLOCK_SIZE;
(length -= GCM_BLOCK_SIZE,
src += GCM_BLOCK_SIZE, dst += GCM_BLOCK_SIZE))
{
f (cipher, GCM_BLOCK_SIZE, dst, ctx->ctr.b);
memxor (dst, src, GCM_BLOCK_SIZE);
INC32 (ctx->ctr);
}
}
else
{
for (; length >= GCM_BLOCK_SIZE;
(length -= GCM_BLOCK_SIZE,
src += GCM_BLOCK_SIZE, dst += GCM_BLOCK_SIZE))
{
f (cipher, GCM_BLOCK_SIZE, buffer, ctx->ctr.b);
memxor3 (dst, src, buffer, GCM_BLOCK_SIZE);
INC32 (ctx->ctr);
}
}
if (length > 0)
{
/* A final partial block */
f (cipher, GCM_BLOCK_SIZE, buffer, ctx->ctr.b);
memxor3 (dst, src, buffer, length);
INC32 (ctx->ctr);
}
}
void
gcm_encrypt (struct gcm_ctx *ctx, const struct gcm_key *key,
void *cipher, nettle_crypt_func *f,
unsigned length, uint8_t *dst, const uint8_t *src)
{
assert(ctx->data_size % GCM_BLOCK_SIZE == 0);
gcm_crypt(ctx, cipher, f, length, dst, src);
gcm_hash(key, &ctx->x, length, dst);
ctx->data_size += length;
}
void
gcm_decrypt(struct gcm_ctx *ctx, const struct gcm_key *key,
void *cipher, nettle_crypt_func *f,
unsigned length, uint8_t *dst, const uint8_t *src)
{
assert(ctx->data_size % GCM_BLOCK_SIZE == 0);
gcm_hash(key, &ctx->x, length, src);
gcm_crypt(ctx, cipher, f, length, dst, src);
ctx->data_size += length;
}
void
gcm_digest(struct gcm_ctx *ctx, const struct gcm_key *key,
void *cipher, nettle_crypt_func *f,
unsigned length, uint8_t *digest)
{
uint8_t buffer[GCM_BLOCK_SIZE];
assert (length <= GCM_BLOCK_SIZE);
ctx->data_size *= 8;
ctx->auth_size *= 8;
WRITE_UINT64 (buffer, ctx->auth_size);
WRITE_UINT64 (buffer + 8, ctx->data_size);
gcm_hash(key, &ctx->x, GCM_BLOCK_SIZE, buffer);
f (cipher, GCM_BLOCK_SIZE, buffer, ctx->iv.b);
memxor3 (digest, ctx->x.b, buffer, length);
return;
}