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tls: make x25519 key generation code more similar to P256

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function                                             old     new   delta
curve_x25519_compute_pubkey_and_premaster              -      74     +74
tls_handshake                                       2146    2072     -74
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(add/remove: 1/0 grow/shrink: 0/1 up/down: 74/-74)              Total: 0 bytes

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
This commit is contained in:
Denys Vlasenko
2021-04-26 13:46:36 +02:00
parent f18a1fd6f3
commit 6b69ab68b4
4 changed files with 51 additions and 44 deletions
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61
networking/tls.c
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@ -1534,7 +1534,7 @@ static void send_client_hello_and_alloc_hsd(tls_state_t *tls, const char *sni)
0x00,0x0a, //extension_type: "supported_groups"
0x00,0x06, //ext len
0x00,0x04, //list len
0x00,0x17, //curve_secp256r1
0x00,0x17, //curve_secp256r1 (aka P256)
//0x00,0x18, //curve_secp384r1
//0x00,0x19, //curve_secp521r1
0x00,0x1d, //curve_x25519 (RFC 7748)
@ -1890,7 +1890,7 @@ static void process_server_key(tls_state_t *tls, int len)
tls->flags |= GOT_EC_CURVE_X25519;
memcpy(tls->hsd->ecc_pub_key32, keybuf, 32);
break;
case _0x03001741: //curve_secp256r1
case _0x03001741: //curve_secp256r1 (aka P256)
/* P256 point can be transmitted odd- or even-compressed
* (first byte is 3 or 2) or uncompressed (4).
*/
@ -1967,46 +1967,35 @@ static void send_client_key_exchange(tls_state_t *tls)
record->key[1] = len & 0xff;
len += 2;
premaster_size = RSA_PREMASTER_SIZE;
} else /* ECDHE */
if (tls->flags & GOT_EC_CURVE_X25519) {
/* ECDHE, curve x25519 */
static const uint8_t basepoint9[CURVE25519_KEYSIZE] ALIGN8 = {9};
uint8_t privkey[CURVE25519_KEYSIZE]; //[32]
if (!(tls->flags & GOT_EC_KEY))
bb_simple_error_msg_and_die("server did not provide EC key");
/* Generate random private key, see RFC 7748 */
tls_get_random(privkey, sizeof(privkey));
privkey[0] &= 0xf8;
privkey[CURVE25519_KEYSIZE-1] = ((privkey[CURVE25519_KEYSIZE-1] & 0x7f) | 0x40);
/* Compute public key */
curve25519(record->key + 1, privkey, basepoint9);
/* Compute premaster using peer's public key */
dbg("computing x25519_premaster\n");
curve25519(premaster, privkey, tls->hsd->ecc_pub_key32);
len = CURVE25519_KEYSIZE;
record->key[0] = len;
len++;
premaster_size = CURVE25519_KEYSIZE;
} else {
/* ECDHE, curve P256 */
/* ECDHE */
if (!(tls->flags & GOT_EC_KEY))
bb_simple_error_msg_and_die("server did not provide EC key");
dbg("computing P256_premaster\n");
curve_P256_compute_pubkey_and_premaster(
record->key + 2, premaster,
/*point:*/ tls->hsd->ecc_pub_key32
);
premaster_size = P256_KEYSIZE;
len = 1 + P256_KEYSIZE * 2;
if (tls->flags & GOT_EC_CURVE_X25519) {
/* ECDHE, curve x25519 */
dbg("computing x25519_premaster\n");
curve_x25519_compute_pubkey_and_premaster(
record->key + 1, premaster,
/*point:*/ tls->hsd->ecc_pub_key32
);
len = CURVE25519_KEYSIZE;
//record->key[0] = len;
//len++;
//premaster_size = CURVE25519_KEYSIZE;
} else {
/* ECDHE, curve P256 */
dbg("computing P256_premaster\n");
curve_P256_compute_pubkey_and_premaster(
record->key + 2, premaster,
/*point:*/ tls->hsd->ecc_pub_key32
);
record->key[1] = 4; /* "uncompressed point" */
len = 1 + P256_KEYSIZE * 2;
}
record->key[0] = len;
record->key[1] = 4;
len++;
premaster_size = P256_KEYSIZE; // = CURVE25519_KEYSIZE = 32
}
record->type = HANDSHAKE_CLIENT_KEY_EXCHANGE;