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gnupg/common/openpgp-oid.c

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/* 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 <https://www.gnu.org/licenses/>.
*/
#include <config.h>
#include <stdlib.h>
#include <errno.h>
#include <ctype.h>
#include <assert.h>
#include "util.h"
#include "openpgpdefs.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; /* Nominal bit length of the curve. */
const char *alias; /* NULL or alternative name of the curve. */
int pubkey_algo; /* Required OpenPGP algo or 0 for ECDSA/ECDH. */
} oidtable[] = {
{ "Curve25519", "1.3.6.1.4.1.3029.1.5.1", 255, "cv25519", PUBKEY_ALGO_ECDH },
{ "Ed25519", "1.3.6.1.4.1.11591.15.1", 255, "ed25519", PUBKEY_ALGO_EDDSA },
{ "X448", "1.3.101.111", 448, "cv448", PUBKEY_ALGO_ECDH },
{ "Ed448", "1.3.101.113", 456, "ed448", PUBKEY_ALGO_EDDSA },
{ "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 };
/* The OID for Curve25519 in OpenPGP format. */
static const char oid_cv25519[] =
{ 0x0a, 0x2b, 0x06, 0x01, 0x04, 0x01, 0x97, 0x55, 0x01, 0x05, 0x01 };
/* The OID for X448 in OpenPGP format. */
/*
* Here, we have a little semantic discrepancy. X448 is the name of
* the ECDH computation and the OID is assigned to the algorithm in
* RFC 8410. Note that this OID is not the one which is assigned to
* the curve itself (originally in 8410). Nevertheless, we use "X448"
* for the curve in libgcrypt.
*/
static const char oid_cv448[] = { 0x03, 0x2b, 0x65, 0x6f };
/* The OID for Ed448 in OpenPGP format. */
static const char oid_ed448[] = { 0x03, 0x2b, 0x65, 0x71 };
/* A table to store keyalgo strings like "rsa2048 or "ed25519" so that
* we do not need to allocate them. This is currently a simple array
* but may eventually be changed to a fast data structure. Noet that
* unknown algorithms are stored with (NBITS,CURVE) set to (0,NULL). */
struct keyalgo_string_s
{
enum gcry_pk_algos algo; /* Mandatory. */
unsigned int nbits; /* Size for classical algos. */
char *curve; /* Curvename (OID) or NULL. */
char *name; /* Allocated name. */
};
static struct keyalgo_string_s *keyalgo_strings; /* The table. */
static size_t keyalgo_strings_size; /* Allocated size. */
static size_t keyalgo_strings_used; /* Used size. */
/* 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 caught 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 representation of the OID in the buffer
* (BUF,LEN). In case of an error NULL is returned and ERRNO is set.
* As per OpenPGP spec the first byte of the buffer is the length of
* the rest; the function performs a consistency check. */
char *
openpgp_oidbuf_to_str (const unsigned char *buf, size_t len)
{
char *string, *p;
int n = 0;
unsigned long val, valmask;
valmask = (unsigned long)0xfe << (8 * (sizeof (valmask) - 1));
/* The first bytes gives the length; check consistency. */
if (!len || buf[0] != len -1)
{
gpg_err_set_errno (EINVAL);
return NULL;
}
/* Skip length byte. */
len--;
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 octet */
string = p = xtrymalloc (len*(1+3)+2+1);
if (!string)
return NULL;
if (!len)
{
*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 < len )
{
if ( (val & valmask) )
goto badoid; /* Overflow. */
val <<= 7;
val |= buf[n] & 0x7f;
}
if (val < 80)
goto badoid;
val -= 80;
sprintf (p, "2.%lu", val);
p += strlen (p);
}
for (n++; n < len; n++)
{
val = buf[n] & 0x7f;
while ( (buf[n]&0x80) && ++n < len )
{
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 a malloced string representation 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;
unsigned int lengthi;
if (!a
|| !gcry_mpi_get_flag (a, GCRYMPI_FLAG_OPAQUE)
|| !(buf = gcry_mpi_get_opaque (a, &lengthi)))
{
gpg_err_set_errno (EINVAL);
return NULL;
}
return openpgp_oidbuf_to_str (buf, (lengthi+7)/8);
}
/* Return true if (BUF,LEN) represents the OID for Ed25519. */
int
openpgp_oidbuf_is_ed25519 (const void *buf, size_t len)
{
return (buf && len == DIM (oid_ed25519)
&& !memcmp (buf, oid_ed25519, DIM (oid_ed25519)));
}
/* 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;
if (!a || !gcry_mpi_get_flag (a, GCRYMPI_FLAG_OPAQUE))
return 0;
buf = gcry_mpi_get_opaque (a, &nbits);
return openpgp_oidbuf_is_ed25519 (buf, (nbits+7)/8);
}
/* Return true if (BUF,LEN) represents the OID for Curve25519. */
int
openpgp_oidbuf_is_cv25519 (const void *buf, size_t len)
{
return (buf && len == DIM (oid_cv25519)
&& !memcmp (buf, oid_cv25519, DIM (oid_cv25519)));
}
/* Return true if (BUF,LEN) represents the OID for Ed448. */
static int
openpgp_oidbuf_is_ed448 (const void *buf, size_t len)
{
return (buf && len == DIM (oid_ed448)
&& !memcmp (buf, oid_ed448, DIM (oid_ed448)));
}
/* Return true if (BUF,LEN) represents the OID for X448. */
static int
openpgp_oidbuf_is_cv448 (const void *buf, size_t len)
{
return (buf && len == DIM (oid_cv448)
&& !memcmp (buf, oid_cv448, DIM (oid_cv448)));
}
/* Return true if the MPI A represents the OID for Curve25519. */
int
openpgp_oid_is_cv25519 (gcry_mpi_t a)
{
const unsigned char *buf;
unsigned int nbits;
if (!a || !gcry_mpi_get_flag (a, GCRYMPI_FLAG_OPAQUE))
return 0;
buf = gcry_mpi_get_opaque (a, &nbits);
return openpgp_oidbuf_is_cv25519 (buf, (nbits+7)/8);
}
/* Return true if the MPI A represents the OID for Ed448. */
int
openpgp_oid_is_ed448 (gcry_mpi_t a)
{
const unsigned char *buf;
unsigned int nbits;
if (!a || !gcry_mpi_get_flag (a, GCRYMPI_FLAG_OPAQUE))
return 0;
buf = gcry_mpi_get_opaque (a, &nbits);
return openpgp_oidbuf_is_ed448 (buf, (nbits+7)/8);
}
/* Return true if the MPI A represents the OID for X448. */
int
openpgp_oid_is_cv448 (gcry_mpi_t a)
{
const unsigned char *buf;
unsigned int nbits;
if (!a || !gcry_mpi_get_flag (a, GCRYMPI_FLAG_OPAQUE))
return 0;
buf = gcry_mpi_get_opaque (a, &nbits);
return openpgp_oidbuf_is_cv448 (buf, (nbits+7)/8);
}
/* 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. If R_ALGO is not NULL and a specific ECC algorithm is
required for this curve its OpenPGP algorithm number is stored
there; otherwise 0 is stored which indicates that ECDSA or ECDH can
be used. */
const char *
openpgp_curve_to_oid (const char *name, unsigned int *r_nbits, int *r_algo)
{
int i;
unsigned int nbits = 0;
const char *oidstr = NULL;
int algo = 0;
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;
algo = oidtable[i].pubkey_algo;
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;
algo = oidtable[i].pubkey_algo;
break;
}
}
}
if (r_nbits)
*r_nbits = nbits;
if (r_algo)
*r_algo = algo;
return oidstr;
}
/* Map an OpenPGP OID to the Libgcrypt curve name. Returns NULL for
* unknown curve names. Unless CANON is set we prefer an alias name
* here which is more suitable for printing. */
const char *
openpgp_oid_to_curve (const char *oidstr, int canon)
{
int i;
if (!oidstr)
return NULL;
for (i=0; oidtable[i].name; i++)
if (!strcmp (oidtable[i].oidstr, oidstr))
return !canon && oidtable[i].alias? oidtable[i].alias : oidtable[i].name;
return NULL;
}
/* Map an OpenPGP OID, name or alias to the Libgcrypt curve name.
* Returns NULL for unknown curve names. Unless CANON is set we
* prefer an alias name here which is more suitable for printing. */
const char *
openpgp_oid_or_name_to_curve (const char *oidname, int canon)
{
int i;
if (!oidname)
return NULL;
for (i=0; oidtable[i].name; i++)
if (!strcmp (oidtable[i].oidstr, oidname)
|| !strcmp (oidtable[i].name, oidname)
|| (oidtable[i].alias &&!strcmp (oidtable[i].alias, oidname)))
return !canon && oidtable[i].alias? oidtable[i].alias : oidtable[i].name;
return NULL;
}
/* Return true if the curve with NAME is supported. */
static int
curve_supported_p (const char *name)
{
int result = 0;
gcry_sexp_t keyparms;
if (!gcry_sexp_build (&keyparms, NULL, "(public-key(ecc(curve %s)))", name))
{
result = !!gcry_pk_get_curve (keyparms, 0, NULL);
gcry_sexp_release (keyparms);
}
return result;
}
/* Enumerate available and supported OpenPGP curves. The caller needs
to set the integer variable at ITERP to zero and keep on calling
this function until NULL is returned. */
const char *
openpgp_enum_curves (int *iterp)
{
int idx = *iterp;
while (idx >= 0 && idx < DIM (oidtable) && oidtable[idx].name)
{
if (curve_supported_p (oidtable[idx].name))
{
*iterp = idx + 1;
return oidtable[idx].alias? oidtable[idx].alias : oidtable[idx].name;
}
idx++;
}
*iterp = idx;
return NULL;
}
/* Return the Libgcrypt name for the gpg curve NAME if supported. If
* R_ALGO is not NULL the required OpenPGP public key algo or 0 is
* stored at that address. If R_NBITS is not NULL the nominal bitsize
* of the curves is stored there. NULL is returned if the curve is
* not supported. */
const char *
openpgp_is_curve_supported (const char *name, int *r_algo,
unsigned int *r_nbits)
{
int idx;
if (r_algo)
*r_algo = 0;
if (r_nbits)
*r_nbits = 0;
for (idx = 0; idx < DIM (oidtable) && oidtable[idx].name; idx++)
{
if ((!strcmp (name, oidtable[idx].name)
|| (oidtable[idx].alias && !strcmp (name, (oidtable[idx].alias))))
&& curve_supported_p (oidtable[idx].name))
{
if (r_algo)
*r_algo = oidtable[idx].pubkey_algo;
if (r_nbits)
*r_nbits = oidtable[idx].nbits;
return oidtable[idx].name;
}
}
return NULL;
}
/* Map a Gcrypt public key algorithm number to the used by OpenPGP.
* Returns 0 for unknown gcry algorithm. */
pubkey_algo_t
map_gcry_pk_to_openpgp (enum gcry_pk_algos algo)
{
switch (algo)
{
case GCRY_PK_EDDSA: return PUBKEY_ALGO_EDDSA;
case GCRY_PK_ECDSA: return PUBKEY_ALGO_ECDSA;
case GCRY_PK_ECDH: return PUBKEY_ALGO_ECDH;
default: return algo < 110 ? (pubkey_algo_t)algo : 0;
}
}
/* Map an OpenPGP public key algorithm number to the one used by
* Libgcrypt. Returns 0 for unknown gcry algorithm. */
enum gcry_pk_algos
map_openpgp_pk_to_gcry (pubkey_algo_t algo)
{
switch (algo)
{
case PUBKEY_ALGO_EDDSA: return GCRY_PK_EDDSA;
case PUBKEY_ALGO_ECDSA: return GCRY_PK_ECDSA;
case PUBKEY_ALGO_ECDH: return GCRY_PK_ECDH;
default: return algo < 110 ? (enum gcry_pk_algos)algo : 0;
}
}
/* Return a string describing the public key algorithm and the
* keysize. For elliptic curves the function prints the name of the
* curve because the keysize is a property of the curve. ALGO is the
* Gcrypt algorithm number, CURVE is either NULL or gives the OID of
* the curve, NBITS is either 0 or the size for algorithms like RSA.
* The returned string is taken from permanent table. Examples
* for the output are:
*
* "rsa3072" - RSA with 3072 bit
* "elg1024" - Elgamal with 1024 bit
* "ed25519" - ECC using the curve Ed25519.
* "E_1.2.3.4" - ECC using the unsupported curve with OID "1.2.3.4".
* "E_1.3.6.1.4.1.11591.2.12242973" - ECC with a bogus OID.
* "unknown_N" - Unknown OpenPGP algorithm N.
* If N is > 110 this is a gcrypt algo.
*/
const char *
get_keyalgo_string (enum gcry_pk_algos algo,
unsigned int nbits, const char *curve)
{
const char *prefix;
int i;
char *name, *curvebuf;
switch (algo)
{
case GCRY_PK_RSA: prefix = "rsa"; break;
case GCRY_PK_ELG: prefix = "elg"; break;
case GCRY_PK_DSA: prefix = "dsa"; break;
case GCRY_PK_ECC:
case GCRY_PK_ECDH:
case GCRY_PK_ECDSA:
case GCRY_PK_EDDSA: prefix = ""; break;
default: prefix = NULL; break;
}
if (prefix && *prefix && nbits)
{
for (i=0; i < keyalgo_strings_used; i++)
{
if (keyalgo_strings[i].algo == algo
&& keyalgo_strings[i].nbits
&& keyalgo_strings[i].nbits == nbits)
return keyalgo_strings[i].name;
}
/* Not yet in the table - add it. */
name = xasprintf ("%s%u", prefix, nbits);
nbits = nbits? nbits : 1; /* No nbits - oops - use 1 instead. */
curvebuf = NULL;
}
else if (prefix && !*prefix)
{
const char *curvename;
for (i=0; i < keyalgo_strings_used; i++)
{
if (keyalgo_strings[i].algo == algo
&& keyalgo_strings[i].curve && curve
&& !strcmp (keyalgo_strings[i].curve, curve))
return keyalgo_strings[i].name;
}
/* Not yet in the table - add it. */
curvename = openpgp_oid_or_name_to_curve (curve, 0);
if (curvename)
name = xasprintf ("%s", curvename);
else if (curve)
name = xasprintf ("E_%s", curve);
else
name = xasprintf ("E_error");
nbits = 0;
curvebuf = curve? xstrdup (curve) : NULL;
}
else
{
for (i=0; i < keyalgo_strings_used; i++)
{
if (keyalgo_strings[i].algo == algo
&& !keyalgo_strings[i].nbits
&& !keyalgo_strings[i].curve)
return keyalgo_strings[i].name;
}
/* Not yet in the table - add it. */
name = xasprintf ("unknown_%u", (unsigned int)algo);
nbits = 0;
curvebuf = NULL;
}
/* Store a new entry. This is a loop because of a possible nPth
* thread switch during xrealloc. */
while (keyalgo_strings_used >= keyalgo_strings_size)
{
keyalgo_strings_size += 10;
if (keyalgo_strings_size > 1024*1024)
log_fatal ("%s: table getting too large - possible DoS\n", __func__);
keyalgo_strings = xrealloc (keyalgo_strings, (keyalgo_strings_size
* sizeof *keyalgo_strings));
}
keyalgo_strings[keyalgo_strings_used].algo = algo;
keyalgo_strings[keyalgo_strings_used].nbits = nbits;
keyalgo_strings[keyalgo_strings_used].curve = curvebuf;
keyalgo_strings[keyalgo_strings_used].name = name;
keyalgo_strings_used++;
return name; /* Note that this is in the table. */
}
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