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|
/* cipher-siv.c - SIV implementation (RFC 5297)
* Copyright (C) 2021 Jussi Kivilinna <jussi.kivilinna@iki.fi>
*
* 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/>.
*/
#include <config.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <errno.h>
#include "g10lib.h"
#include "cipher.h"
#include "bufhelp.h"
#include "./cipher-internal.h"
static inline void
s2v_double (unsigned char *d)
{
u64 hi, lo, mask;
hi = buf_get_be64(d + 0);
lo = buf_get_be64(d + 8);
mask = -(hi >> 63);
hi = (hi << 1) ^ (lo >> 63);
lo = (lo << 1) ^ (mask & 0x87);
buf_put_be64(d + 0, hi);
buf_put_be64(d + 8, lo);
}
static void
s2v_pad (unsigned char *out, const byte *in, size_t inlen)
{
static const unsigned char padding[GCRY_SIV_BLOCK_LEN] = { 0x80 };
gcry_assert(inlen < GCRY_SIV_BLOCK_LEN);
buf_cpy (out, in, inlen);
buf_cpy (out + inlen, padding, GCRY_SIV_BLOCK_LEN - inlen);
}
gcry_err_code_t
_gcry_cipher_siv_setkey (gcry_cipher_hd_t c,
const unsigned char *ctrkey, size_t ctrkeylen)
{
static const unsigned char zero[GCRY_SIV_BLOCK_LEN] = { 0 };
gcry_err_code_t err;
if (c->spec->blocksize != GCRY_SIV_BLOCK_LEN)
return GPG_ERR_CIPHER_ALGO;
c->u_mode.siv.aad_count = 0;
c->u_mode.siv.dec_tag_set = 0;
c->marks.tag = 0;
c->marks.iv = 0;
/* Set CTR mode key. */
err = c->spec->setkey (c->u_mode.siv.ctr_context, ctrkey, ctrkeylen,
&c->bulk);
if (err != 0)
return err;
/* Initialize S2V. */
memset (&c->u_mode.siv.s2v_cmac, 0, sizeof(c->u_mode.siv.s2v_cmac));
err = _gcry_cmac_generate_subkeys (c, &c->u_mode.siv.s2v_cmac);
if (err != 0)
return err;
err = _gcry_cmac_write (c, &c->u_mode.siv.s2v_cmac, zero, GCRY_SIV_BLOCK_LEN);
if (err != 0)
return err;
err = _gcry_cmac_final (c, &c->u_mode.siv.s2v_cmac);
if (err != 0)
return err;
memcpy (c->u_mode.siv.s2v_zero_block, c->u_mode.siv.s2v_cmac.u_iv.iv,
GCRY_SIV_BLOCK_LEN);
memcpy (c->u_mode.siv.s2v_d, c->u_mode.siv.s2v_zero_block,
GCRY_SIV_BLOCK_LEN);
return 0;
}
gcry_err_code_t
_gcry_cipher_siv_authenticate (gcry_cipher_hd_t c,
const byte *aadbuf, size_t aadbuflen)
{
gcry_err_code_t err;
if (c->spec->blocksize != GCRY_SIV_BLOCK_LEN)
return GPG_ERR_CIPHER_ALGO;
if (c->marks.tag)
return GPG_ERR_INV_STATE;
if (c->marks.iv)
return GPG_ERR_INV_STATE;
if (c->u_mode.siv.aad_count >= 126)
return GPG_ERR_INV_STATE; /* Too many AD vector components. */
c->u_mode.siv.aad_count++;
_gcry_cmac_reset (&c->u_mode.siv.s2v_cmac);
err = _gcry_cmac_write (c, &c->u_mode.siv.s2v_cmac, aadbuf, aadbuflen);
if (err != 0)
return err;
err = _gcry_cmac_final (c, &c->u_mode.siv.s2v_cmac);
if (err != 0)
return err;
s2v_double (c->u_mode.siv.s2v_d);
cipher_block_xor_1 (c->u_mode.siv.s2v_d, c->u_mode.siv.s2v_cmac.u_iv.iv,
GCRY_SIV_BLOCK_LEN);
return 0;
}
gcry_err_code_t
_gcry_cipher_siv_set_nonce (gcry_cipher_hd_t c, const byte *nonce,
size_t noncelen)
{
gcry_err_code_t err;
err = _gcry_cipher_siv_authenticate (c, nonce, noncelen);
if (err)
return err;
/* Nonce is the last AD before plaintext. */
c->marks.iv = 1;
return 0;
}
static gcry_err_code_t
s2v_plaintext (gcry_cipher_hd_t c, const byte *plain, size_t plainlen)
{
gcry_err_code_t err;
if (c->u_mode.siv.aad_count >= 127)
return GPG_ERR_INV_STATE; /* Too many AD vector components. */
_gcry_cmac_reset (&c->u_mode.siv.s2v_cmac);
if (plainlen >= GCRY_SIV_BLOCK_LEN)
{
err = _gcry_cmac_write (c, &c->u_mode.siv.s2v_cmac, plain,
plainlen - GCRY_SIV_BLOCK_LEN);
if (err)
return err;
cipher_block_xor_1 (c->u_mode.siv.s2v_d,
plain + plainlen - GCRY_SIV_BLOCK_LEN,
GCRY_SIV_BLOCK_LEN);
err = _gcry_cmac_write (c, &c->u_mode.siv.s2v_cmac, c->u_mode.siv.s2v_d,
GCRY_SIV_BLOCK_LEN);
if (err)
return err;
}
else
{
unsigned char pad_sn[GCRY_SIV_BLOCK_LEN];
s2v_double (c->u_mode.siv.s2v_d);
s2v_pad (pad_sn, plain, plainlen);
cipher_block_xor_1 (pad_sn, c->u_mode.siv.s2v_d, GCRY_SIV_BLOCK_LEN);
err = _gcry_cmac_write (c, &c->u_mode.siv.s2v_cmac, pad_sn,
GCRY_SIV_BLOCK_LEN);
wipememory (pad_sn, sizeof(pad_sn));
if (err)
return err;
}
c->u_mode.siv.aad_count++;
return _gcry_cmac_final (c, &c->u_mode.siv.s2v_cmac);
}
gcry_err_code_t
_gcry_cipher_siv_encrypt (gcry_cipher_hd_t c,
byte *outbuf, size_t outbuflen,
const byte *inbuf, size_t inbuflen)
{
gcry_err_code_t err;
u64 q_lo;
if (c->spec->blocksize != GCRY_SIV_BLOCK_LEN)
return GPG_ERR_CIPHER_ALGO;
if (outbuflen < inbuflen)
return GPG_ERR_BUFFER_TOO_SHORT;
if (c->marks.tag)
return GPG_ERR_INV_STATE;
if (c->u_mode.siv.dec_tag_set)
return GPG_ERR_INV_STATE;
/* Pass plaintext to S2V. */
err = s2v_plaintext (c, inbuf, inbuflen);
if (err != 0)
return err;
/* Clear 31th and 63th bits. */
memcpy (c->u_ctr.ctr, c->u_mode.siv.s2v_cmac.u_iv.iv, GCRY_SIV_BLOCK_LEN);
q_lo = buf_get_be64(c->u_ctr.ctr + 8);
q_lo &= ~((u64)1 << 31);
q_lo &= ~((u64)1 << 63);
buf_put_be64(c->u_ctr.ctr + 8, q_lo);
/* Encrypt plaintext. */
err = _gcry_cipher_ctr_encrypt_ctx(c, outbuf, outbuflen, inbuf, inbuflen,
c->u_mode.siv.ctr_context);
if (err != 0)
return err;
c->marks.tag = 1;
return 0;
}
gcry_err_code_t
_gcry_cipher_siv_set_decryption_tag (gcry_cipher_hd_t c,
const byte *tag, size_t taglen)
{
if (taglen != GCRY_SIV_BLOCK_LEN)
return GPG_ERR_INV_ARG;
if (c->spec->blocksize != GCRY_SIV_BLOCK_LEN)
return GPG_ERR_CIPHER_ALGO;
if (c->marks.tag)
return GPG_ERR_INV_STATE;
memcpy (&c->u_mode.siv.dec_tag, tag, GCRY_SIV_BLOCK_LEN);
c->u_mode.siv.dec_tag_set = 1;
return 0;
}
gcry_err_code_t
_gcry_cipher_siv_decrypt (gcry_cipher_hd_t c,
byte *outbuf, size_t outbuflen,
const byte *inbuf, size_t inbuflen)
{
gcry_err_code_t err;
u64 q_lo;
if (c->spec->blocksize != GCRY_SIV_BLOCK_LEN)
return GPG_ERR_CIPHER_ALGO;
if (outbuflen < inbuflen)
return GPG_ERR_BUFFER_TOO_SHORT;
if (c->marks.tag)
return GPG_ERR_INV_STATE;
if (!c->u_mode.siv.dec_tag_set)
return GPG_ERR_INV_STATE;
/* Clear 31th and 63th bits. */
memcpy (c->u_ctr.ctr, c->u_mode.siv.dec_tag, GCRY_SIV_BLOCK_LEN);
q_lo = buf_get_be64(c->u_ctr.ctr + 8);
q_lo &= ~((u64)1 << 31);
q_lo &= ~((u64)1 << 63);
buf_put_be64(c->u_ctr.ctr + 8, q_lo);
/* Decrypt ciphertext. */
err = _gcry_cipher_ctr_encrypt_ctx(c, outbuf, outbuflen, inbuf, inbuflen,
c->u_mode.siv.ctr_context);
if (err != 0)
return err;
/* Pass plaintext to S2V. */
err = s2v_plaintext (c, outbuf, inbuflen);
if (err != 0)
return err;
c->marks.tag = 1;
if (!buf_eq_const(c->u_mode.siv.s2v_cmac.u_iv.iv, c->u_mode.siv.dec_tag,
GCRY_SIV_BLOCK_LEN))
{
wipememory (outbuf, inbuflen);
return GPG_ERR_CHECKSUM;
}
return 0;
}
gcry_err_code_t
_gcry_cipher_siv_get_tag (gcry_cipher_hd_t c, unsigned char *outbuf,
size_t outbuflen)
{
gcry_err_code_t err;
if (c->spec->blocksize != GCRY_SIV_BLOCK_LEN)
return GPG_ERR_CIPHER_ALGO;
if (c->u_mode.siv.dec_tag_set)
return GPG_ERR_INV_STATE;
if (!c->marks.tag)
{
/* Finalize SIV with zero-length plaintext. */
err = s2v_plaintext (c, NULL, 0);
if (err != 0)
return err;
c->marks.tag = 1;
}
if (outbuflen > GCRY_SIV_BLOCK_LEN)
outbuflen = GCRY_SIV_BLOCK_LEN;
/* We already checked that OUTBUF is large enough to hold
* the result or has valid truncated length. */
memcpy (outbuf, c->u_mode.siv.s2v_cmac.u_iv.iv, outbuflen);
return 0;
}
gcry_err_code_t
_gcry_cipher_siv_check_tag (gcry_cipher_hd_t c, const unsigned char *intag,
size_t taglen)
{
gcry_err_code_t err;
size_t n;
if (c->spec->blocksize != GCRY_SIV_BLOCK_LEN)
return GPG_ERR_CIPHER_ALGO;
if (!c->marks.tag)
{
/* Finalize SIV with zero-length plaintext. */
err = s2v_plaintext (c, NULL, 0);
if (err != 0)
return err;
c->marks.tag = 1;
}
n = GCRY_SIV_BLOCK_LEN;
if (taglen < n)
n = taglen;
if (!buf_eq_const(c->u_mode.siv.s2v_cmac.u_iv.iv, intag, n)
|| GCRY_SIV_BLOCK_LEN != taglen)
{
return GPG_ERR_CHECKSUM;
}
return 0;
}
|
