/* Put the DIGEST into an DER encoded container and return it in R_VAL. */
static int
encode_md_for_card (const unsigned char *digest, size_t digestlen, int algo,
unsigned char **r_val, size_t *r_len)
{
unsigned char *frame;
unsigned char asn[100];
size_t asnlen;
*r_val = NULL;
*r_len = 0;
asnlen = DIM(asn);
if (!algo || gcry_md_test_algo (algo))
return gpg_error (GPG_ERR_DIGEST_ALGO);
if (gcry_md_algo_info (algo, GCRYCTL_GET_ASNOID, asn, &asnlen))
{
log_error ("no object identifier for algo %d\n", algo);
return gpg_error (GPG_ERR_INTERNAL);
}
frame = xtrymalloc (asnlen + digestlen);
if (!frame)
return out_of_core ();
memcpy (frame, asn, asnlen);
memcpy (frame+asnlen, digest, digestlen);
if (DBG_CRYPTO)
log_printhex ("encoded hash:", frame, asnlen+digestlen);
*r_val = frame;
*r_len = asnlen+digestlen;
return 0;
}
static int rsa_pkcs1_encode_sig(gcry_mpi_t *r_result, size_t size,
const uint8_t *hash, int algo)
{
uint8_t asn[100];
uint8_t frame[4096/8];
size_t asnlen = sizeof(asn);
size_t hashlen = gcry_md_get_algo_dlen(algo);
if (gcry_md_algo_info(algo, GCRYCTL_GET_ASNOID, asn, &asnlen))
return VLC_EGENERIC;
if (!hashlen || hashlen + asnlen + 4 > size)
return VLC_EGENERIC;
frame[0] = 0;
frame[1] = 1; /* block type */
int pad = size - hashlen - asnlen - 3 ;
memset (&frame[2], 0xff, pad );
frame[2+pad] = 0;
memcpy(&frame[3+pad], asn, asnlen);
memcpy(&frame[3+pad+asnlen], hash, hashlen);
if (gcry_mpi_scan(r_result, GCRYMPI_FMT_USG, frame, size, &size))
return VLC_EGENERIC;
return VLC_SUCCESS;
}
static void
run_selftest (int algo)
{
gpg_error_t err;
size_t n;
n = 1;
err = gcry_md_algo_info (algo, GCRYCTL_SELFTEST, NULL, &n);
if (err && gpg_err_code (err) != GPG_ERR_NOT_IMPLEMENTED)
fail ("extended selftest for %s (%d) failed: %s",
gcry_md_algo_name (algo), algo, gpg_strerror (err));
else if (err && verbose)
show ("extended selftest for %s (%d) not implemented",
gcry_md_algo_name (algo), algo);
else if (verbose)
show ("extended selftest for %s (%d) passed",
gcry_md_algo_name (algo), algo);
}
static int
do_encode_md (gcry_md_hd_t md, int algo, int pkalgo, unsigned int nbits,
gcry_sexp_t pkey, gcry_mpi_t *r_val)
{
int n;
size_t nframe;
unsigned char *frame;
if (pkalgo == GCRY_PK_DSA || pkalgo == GCRY_PK_ECDSA)
{
unsigned int qbits;
if ( pkalgo == GCRY_PK_ECDSA )
qbits = gcry_pk_get_nbits (pkey);
else
qbits = get_dsa_qbits (pkey);
if ( (qbits%8) )
{
log_error(_("DSA requires the hash length to be a"
" multiple of 8 bits\n"));
return gpg_error (GPG_ERR_INTERNAL);
}
/* Don't allow any Q smaller than 160 bits. We don't want
someone to issue signatures from a key with a 16-bit Q or
something like that, which would look correct but allow
trivial forgeries. Yes, I know this rules out using MD5 with
DSA. ;) */
if (qbits < 160)
{
log_error (_("%s key uses an unsafe (%u bit) hash\n"),
gcry_pk_algo_name (pkalgo), qbits);
return gpg_error (GPG_ERR_INTERNAL);
}
/* Check if we're too short. Too long is safe as we'll
automatically left-truncate. */
nframe = gcry_md_get_algo_dlen (algo);
if (nframe < qbits/8)
{
log_error (_("a %u bit hash is not valid for a %u bit %s key\n"),
(unsigned int)nframe*8,
gcry_pk_get_nbits (pkey),
gcry_pk_algo_name (pkalgo));
/* FIXME: we need to check the requirements for ECDSA. */
if (nframe < 20 || pkalgo == GCRY_PK_DSA )
return gpg_error (GPG_ERR_INTERNAL);
}
frame = xtrymalloc (nframe);
if (!frame)
return out_of_core ();
memcpy (frame, gcry_md_read (md, algo), nframe);
n = nframe;
/* Truncate. */
if (n > qbits/8)
n = qbits/8;
}
else
{
int i;
unsigned char asn[100];
size_t asnlen;
size_t len;
nframe = (nbits+7) / 8;
asnlen = DIM(asn);
if (!algo || gcry_md_test_algo (algo))
return gpg_error (GPG_ERR_DIGEST_ALGO);
if (gcry_md_algo_info (algo, GCRYCTL_GET_ASNOID, asn, &asnlen))
{
log_error ("no object identifier for algo %d\n", algo);
return gpg_error (GPG_ERR_INTERNAL);
}
len = gcry_md_get_algo_dlen (algo);
if ( len + asnlen + 4 > nframe )
{
log_error ("can't encode a %d bit MD into a %d bits frame\n",
(int)(len*8), (int)nbits);
return gpg_error (GPG_ERR_INTERNAL);
}
/* We encode the MD in this way:
*
* 0 A PAD(n bytes) 0 ASN(asnlen bytes) MD(len bytes)
*
* PAD consists of FF bytes.
*/
frame = xtrymalloc (nframe);
if (!frame)
return out_of_core ();
n = 0;
frame[n++] = 0;
frame[n++] = 1; /* block type */
i = nframe - len - asnlen -3 ;
assert ( i > 1 );
memset ( frame+n, 0xff, i ); n += i;
frame[n++] = 0;
memcpy ( frame+n, asn, asnlen ); n += asnlen;
memcpy ( frame+n, gcry_md_read(md, algo), len ); n += len;
assert ( n == nframe );
}
if (DBG_CRYPTO)
{
int j;
log_debug ("encoded hash:");
for (j=0; j < nframe; j++)
log_printf (" %02X", frame[j]);
log_printf ("\n");
}
gcry_mpi_scan (r_val, GCRYMPI_FMT_USG, frame, n, &nframe);
xfree (frame);
return 0;
}
