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gnupg/common/openpgp-oid.c
Werner Koch bf2fc12b83 gpg: Fix export of NIST ECC keys.
* common/openpgp-oid.c (struct oidtable): New.
(openpgp_curve_to_oid): Rewrite and allow OID as input.
(openpgp_oid_to_curve): Make use of the new table.
--

Due to the previous change we now usually store the OID with the
private key and not the name.  Thus during import we do not anymore
need to map the name to an oid but can use the oid directly.  We fix
that by extending openpgp_curve_to_oid to allow an oidstr as input.
2014-09-02 12:10:19 +02:00

348 lines
9.1 KiB
C

/* openpgp-oids.c - OID helper for OpenPGP
* Copyright (C) 2011 Free Software Foundation, Inc.
* Copyright (C) 2013 Werner Koch
*
* This file is part of GnuPG.
*
* This file is free software; you can redistribute it and/or modify
* it under the terms of either
*
* - the GNU Lesser General Public License as published by the Free
* Software Foundation; either version 3 of the License, or (at
* your option) any later version.
*
* or
*
* - the GNU General Public License as published by the Free
* Software Foundation; either version 2 of the License, or (at
* your option) any later version.
*
* or both in parallel, as here.
*
* This file 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 General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program; if not, see <http://www.gnu.org/licenses/>.
*/
#include <config.h>
#include <stdlib.h>
#include <errno.h>
#include <ctype.h>
#include <assert.h>
#include "util.h"
/* A table with all our supported OpenPGP curves. */
static struct {
const char *name; /* Standard name. */
const char *oidstr; /* IETF formatted OID. */
unsigned int nbits; /* Nominla bit length of the curve. */
const char *alias; /* NULL or alternative name of the curve. */
} oidtable[] = {
{ "Ed25519", "1.3.6.1.4.1.11591.15.1", 255, "ed25519" },
{ "NIST P-256", "1.2.840.10045.3.1.7", 256, "nistp256" },
{ "NIST P-384", "1.3.132.0.34", 384, "nistp384" },
{ "NIST P-521", "1.3.132.0.35", 521, "nistp521" },
{ "brainpoolP256r1", "1.3.36.3.3.2.8.1.1.7", 256 },
{ "brainpoolP384r1", "1.3.36.3.3.2.8.1.1.11", 384 },
{ "brainpoolP512r1", "1.3.36.3.3.2.8.1.1.13", 512 },
{ "secp256k1", "1.3.132.0.10", 256 },
{ NULL, NULL, 0}
};
/* The OID for Curve Ed25519 in OpenPGP format. */
static const char oid_ed25519[] =
{ 0x09, 0x2b, 0x06, 0x01, 0x04, 0x01, 0xda, 0x47, 0x0f, 0x01 };
/* Helper for openpgp_oid_from_str. */
static size_t
make_flagged_int (unsigned long value, char *buf, size_t buflen)
{
int more = 0;
int shift;
/* fixme: figure out the number of bits in an ulong and start with
that value as shift (after making it a multiple of 7) a more
straigtforward implementation is to do it in reverse order using
a temporary buffer - saves a lot of compares */
for (more=0, shift=28; shift > 0; shift -= 7)
{
if (more || value >= (1<<shift))
{
buf[buflen++] = 0x80 | (value >> shift);
value -= (value >> shift) << shift;
more = 1;
}
}
buf[buflen++] = value;
return buflen;
}
/* Convert the OID given in dotted decimal form in STRING to an DER
* encoding and store it as an opaque value at R_MPI. The format of
* the DER encoded is not a regular ASN.1 object but the modified
* format as used by OpenPGP for the ECC curve description. On error
* the function returns and error code an NULL is stored at R_BUG.
* Note that scanning STRING stops at the first white space
* character. */
gpg_error_t
openpgp_oid_from_str (const char *string, gcry_mpi_t *r_mpi)
{
unsigned char *buf;
size_t buflen;
unsigned long val1, val;
const char *endp;
int arcno;
*r_mpi = NULL;
if (!string || !*string)
return gpg_error (GPG_ERR_INV_VALUE);
/* We can safely assume that the encoded OID is shorter than the string. */
buf = xtrymalloc (1 + strlen (string) + 2);
if (!buf)
return gpg_error_from_syserror ();
/* Save the first byte for the length. */
buflen = 1;
val1 = 0; /* Avoid compiler warning. */
arcno = 0;
do {
arcno++;
val = strtoul (string, (char**)&endp, 10);
if (!digitp (string) || !(*endp == '.' || !*endp))
{
xfree (buf);
return gpg_error (GPG_ERR_INV_OID_STRING);
}
if (*endp == '.')
string = endp+1;
if (arcno == 1)
{
if (val > 2)
break; /* Not allowed, error catched below. */
val1 = val;
}
else if (arcno == 2)
{ /* Need to combine the first two arcs in one octet. */
if (val1 < 2)
{
if (val > 39)
{
xfree (buf);
return gpg_error (GPG_ERR_INV_OID_STRING);
}
buf[buflen++] = val1*40 + val;
}
else
{
val += 80;
buflen = make_flagged_int (val, buf, buflen);
}
}
else
{
buflen = make_flagged_int (val, buf, buflen);
}
} while (*endp == '.');
if (arcno == 1 || buflen < 2 || buflen > 254 )
{ /* It is not possible to encode only the first arc. */
xfree (buf);
return gpg_error (GPG_ERR_INV_OID_STRING);
}
*buf = buflen - 1;
*r_mpi = gcry_mpi_set_opaque (NULL, buf, buflen * 8);
if (!*r_mpi)
{
xfree (buf);
return gpg_error_from_syserror ();
}
return 0;
}
/* Return a malloced string represenation of the OID in the opaque MPI
A. In case of an error NULL is returned and ERRNO is set. */
char *
openpgp_oid_to_str (gcry_mpi_t a)
{
const unsigned char *buf;
size_t length;
unsigned int lengthi;
char *string, *p;
int n = 0;
unsigned long val, valmask;
valmask = (unsigned long)0xfe << (8 * (sizeof (valmask) - 1));
if (!a || !gcry_mpi_get_flag (a, GCRYMPI_FLAG_OPAQUE))
{
gpg_err_set_errno (EINVAL);
return NULL;
}
buf = gcry_mpi_get_opaque (a, &lengthi);
length = (lengthi+7)/8;
/* The first bytes gives the length; check consistency. */
if (!length || buf[0] != length -1)
{
gpg_err_set_errno (EINVAL);
return NULL;
}
/* Skip length byte. */
length--;
buf++;
/* To calculate the length of the string we can safely assume an
upper limit of 3 decimal characters per byte. Two extra bytes
account for the special first octect */
string = p = xtrymalloc (length*(1+3)+2+1);
if (!string)
return NULL;
if (!buf || !length)
{
*p = 0;
return string;
}
if (buf[0] < 40)
p += sprintf (p, "0.%d", buf[n]);
else if (buf[0] < 80)
p += sprintf (p, "1.%d", buf[n]-40);
else {
val = buf[n] & 0x7f;
while ( (buf[n]&0x80) && ++n < length )
{
if ( (val & valmask) )
goto badoid; /* Overflow. */
val <<= 7;
val |= buf[n] & 0x7f;
}
val -= 80;
sprintf (p, "2.%lu", val);
p += strlen (p);
}
for (n++; n < length; n++)
{
val = buf[n] & 0x7f;
while ( (buf[n]&0x80) && ++n < length )
{
if ( (val & valmask) )
goto badoid; /* Overflow. */
val <<= 7;
val |= buf[n] & 0x7f;
}
sprintf (p, ".%lu", val);
p += strlen (p);
}
*p = 0;
return string;
badoid:
/* Return a special OID (gnu.gnupg.badoid) to indicate the error
case. The OID is broken and thus we return one which can't do
any harm. Formally this does not need to be a bad OID but an OID
with an arc that can't be represented in a 32 bit word is more
than likely corrupt. */
xfree (string);
return xtrystrdup ("1.3.6.1.4.1.11591.2.12242973");
}
/* Return true if A represents the OID for Ed25519. */
int
openpgp_oid_is_ed25519 (gcry_mpi_t a)
{
const unsigned char *buf;
unsigned int nbits;
size_t n;
if (!a || !gcry_mpi_get_flag (a, GCRYMPI_FLAG_OPAQUE))
return 0;
buf = gcry_mpi_get_opaque (a, &nbits);
n = (nbits+7)/8;
return (n == DIM (oid_ed25519)
&& !memcmp (buf, oid_ed25519, DIM (oid_ed25519)));
}
/* Map the Libgcrypt ECC curve NAME to an OID. If R_NBITS is not NULL
store the bit size of the curve there. Returns NULL for unknown
curve names. */
const char *
openpgp_curve_to_oid (const char *name, unsigned int *r_nbits)
{
int i;
unsigned int nbits = 0;
const char *oidstr = NULL;
if (name)
{
for (i=0; oidtable[i].name; i++)
if (!strcmp (oidtable[i].name, name)
|| (oidtable[i].alias && !strcmp (oidtable[i].alias, name)))
{
oidstr = oidtable[i].oidstr;
nbits = oidtable[i].nbits;
break;
}
if (!oidtable[i].name)
{
/* If not found assume the input is already an OID and check
whether we support it. */
for (i=0; oidtable[i].name; i++)
if (!strcmp (name, oidtable[i].oidstr))
{
oidstr = oidtable[i].oidstr;
nbits = oidtable[i].nbits;
break;
}
}
}
if (r_nbits)
*r_nbits = nbits;
return oidstr;
}
/* Map an OpenPGP OID to the Libgcrypt curve NAME. Returns "?" for
unknown curve names. We prefer an alias name here which is more
suitable for printing. */
const char *
openpgp_oid_to_curve (const char *oidstr)
{
int i;
if (!oidstr)
return "";
for (i=0; oidtable[i].name; i++)
if (!strcmp (oidtable[i].oidstr, oidstr))
return oidtable[i].alias? oidtable[i].alias : oidtable[i].name;
return "?";
}