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gpg: Add X448 support.

Browse Source 
* common/openpgp-oid.c (oidtable): Add X448.
(oid_x448,openpgp_oidbuf_is_x448,openpgp_oid_is_x448): New.
* common/util.h (openpgp_oid_is_x448): New.
* g10/ecdh.c (gen_k): Add handling of opaque MPI and support
endianness.
(pk_ecdh_generate_ephemeral_key): X448 requires opaque MPI.
* g10/keygen.c (gen_ecc): Add support for X448.
(ask_algo, parse_key_parameter_part): Likewise.

Signed-off-by: NIIBE Yutaka <gniibe@fsij.org>
This commit is contained in:
NIIBE Yutaka 2020-06-09 14:56:50 +09:00
parent f5bc945554
commit e9760eb9e7
4 changed files with 70 additions and 2 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

28
common/openpgp-oid.c
View File

@ -48,6 +48,7 @@ static struct {
{ "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, "x448", PUBKEY_ALGO_ECDH },
{ "NIST P-256", "1.2.840.10045.3.1.7", 256, "nistp256" },
{ "NIST P-384", "1.3.132.0.34", 384, "nistp384" },
@ -71,6 +72,9 @@ static const char oid_ed25519[] =
static const char oid_cv25519[] =
{ 0x0a, 0x2b, 0x06, 0x01, 0x04, 0x01, 0x97, 0x55, 0x01, 0x05, 0x01 };
/* The OID for X448 in OpenPGP format. */
static const char oid_x448[] = { 0x03, 0x2b, 0x65, 0x6f };
/* 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
@ -334,6 +338,15 @@ openpgp_oidbuf_is_cv25519 (const void *buf, size_t len)
}
/* Return true if (BUF,LEN) represents the OID for X448. */
static int
openpgp_oidbuf_is_x448 (const void *buf, size_t len)
{
return (buf && len == DIM (oid_x448)
&& !memcmp (buf, oid_x448, DIM (oid_x448)));
}
/* Return true if the MPI A represents the OID for Curve25519. */
int
openpgp_oid_is_cv25519 (gcry_mpi_t a)
@ -349,6 +362,21 @@ openpgp_oid_is_cv25519 (gcry_mpi_t a)
}
/* Return true if the MPI A represents the OID for X448. */
int
openpgp_oid_is_x448 (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_x448 (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

1
common/util.h
View File

@ -238,6 +238,7 @@ int openpgp_oidbuf_is_ed25519 (const void *buf, size_t len);
int openpgp_oid_is_ed25519 (gcry_mpi_t a);
int openpgp_oidbuf_is_cv25519 (const void *buf, size_t len);
int openpgp_oid_is_cv25519 (gcry_mpi_t a);
int openpgp_oid_is_x448 (gcry_mpi_t a);
const char *openpgp_curve_to_oid (const char *name,
unsigned int *r_nbits, int *r_algo);
const char *openpgp_oid_to_curve (const char *oid, int canon);

29
g10/ecdh.c
View File

@ -422,10 +422,27 @@ pk_ecdh_encrypt_with_shared_point (gcry_mpi_t shared_mpi,
static gcry_mpi_t
gen_k (unsigned nbits)
gen_k (unsigned nbits, int little_endian, int is_opaque)
{
gcry_mpi_t k;
if (is_opaque)
{
unsigned char *p;
size_t nbytes = (nbits+7)/8;
p = gcry_random_bytes_secure (nbytes, GCRY_STRONG_RANDOM);
if ((nbits % 8))
{
if (little_endian)
p[nbytes-1] &= ((1 << (nbits % 8)) - 1);
else
p[0] &= ((1 << (nbits % 8)) - 1);
}
k = gcry_mpi_set_opaque (NULL, p, nbits);
return k;
}
k = gcry_mpi_snew (nbits);
if (DBG_CRYPTO)
log_debug ("choosing a random k of %u bits\n", nbits);
@ -453,13 +470,21 @@ pk_ecdh_generate_ephemeral_key (gcry_mpi_t *pkey, gcry_mpi_t *r_k)
{
unsigned int nbits;
gcry_mpi_t k;
int is_little_endian = 0;
int require_opaque = 0;
if (openpgp_oid_is_x448 (pkey[0]))
{
is_little_endian = 1;
require_opaque = 1;
}
*r_k = NULL;
nbits = pubkey_nbits (PUBKEY_ALGO_ECDH, pkey);
if (!nbits)
return gpg_error (GPG_ERR_TOO_SHORT);
k = gen_k (nbits);
k = gen_k (nbits, is_little_endian, require_opaque);
if (!k)
BUG ();

14
g10/keygen.c
View File

@ -1748,6 +1748,8 @@ gen_ecc (int algo, const char *curve, kbnode_t pub_root,
curve = "Curve25519";
else if (!ascii_strcasecmp (curve, "ed25519"))
curve = "Ed25519";
else if (!ascii_strcasecmp (curve, "x448"))
curve = "X448";
/* Note that we use the "comp" flag with EdDSA to request the use of
a 0x40 compression prefix octet. */
@ -1765,6 +1767,13 @@ gen_ecc (int algo, const char *curve, kbnode_t pub_root,
(((keygen_flags & KEYGEN_FLAG_TRANSIENT_KEY)
&& (keygen_flags & KEYGEN_FLAG_NO_PROTECTION))?
" transient-key" : ""));
else if (algo == PUBKEY_ALGO_ECDH && !strcmp (curve, "X448"))
keyparms = xtryasprintf
("(genkey(ecc(curve %zu:%s)(flags comp%s)))",
strlen (curve), curve,
(((keygen_flags & KEYGEN_FLAG_TRANSIENT_KEY)
&& (keygen_flags & KEYGEN_FLAG_NO_PROTECTION))?
" transient-key" : ""));
else
keyparms = xtryasprintf
("(genkey(ecc(curve %zu:%s)(flags nocomp%s)))",
@ -2319,6 +2328,8 @@ ask_algo (ctrl_t ctrl, int addmode, int *r_subkey_algo, unsigned int *r_usage,
kpi->algo = PUBKEY_ALGO_EDDSA;
else if (!strcmp (algostr, "cv25519"))
kpi->algo = PUBKEY_ALGO_ECDH;
else if (!strcmp (algostr, "x448"))
kpi->algo = PUBKEY_ALGO_ECDH;
else if ((kpi->usage & GCRY_PK_USAGE_ENCR))
kpi->algo = PUBKEY_ALGO_ECDH;
else
@ -3472,6 +3483,8 @@ parse_key_parameter_part (ctrl_t ctrl,
algo = PUBKEY_ALGO_EDDSA;
else if (!strcmp (algostr, "cv25519"))
algo = PUBKEY_ALGO_ECDH;
else if (!strcmp (algostr, "x448"))
algo = PUBKEY_ALGO_ECDH;
else if ((kpi->usage & GCRY_PK_USAGE_ENCR))
algo = PUBKEY_ALGO_ECDH;
else
@ -3599,6 +3612,7 @@ parse_key_parameter_part (ctrl_t ctrl,
* elg2048 := Elgamal with 2048 bit.
* ed25519 := EDDSA using curve Ed25519.
* cv25519 := ECDH using curve Curve25519.
* x448 := ECDH using curve X448.
* nistp256:= ECDSA or ECDH using curve NIST P-256
*
* All strings with an unknown prefix are considered an elliptic