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#include "options.h"
#include "includes.h"
#include "dbutil.h"
#include "crypto_desc.h"
#include "ecc.h"
#include "ecdsa.h"
#include "signkey.h"
#ifdef DROPBEAR_ECDSA
int signkey_is_ecdsa(enum signkey_type type)
{
return type == DROPBEAR_SIGNKEY_ECDSA_NISTP256
|| type == DROPBEAR_SIGNKEY_ECDSA_NISTP384
|| type == DROPBEAR_SIGNKEY_ECDSA_NISTP521;
}
enum signkey_type ecdsa_signkey_type(ecc_key * key) {
#ifdef DROPBEAR_ECC_256
if (key->dp == ecc_curve_nistp256.dp) {
return DROPBEAR_SIGNKEY_ECDSA_NISTP256;
}
#endif
#ifdef DROPBEAR_ECC_384
if (key->dp == ecc_curve_nistp384.dp) {
return DROPBEAR_SIGNKEY_ECDSA_NISTP384;
}
#endif
#ifdef DROPBEAR_ECC_521
if (key->dp == ecc_curve_nistp521.dp) {
return DROPBEAR_SIGNKEY_ECDSA_NISTP521;
}
#endif
return DROPBEAR_SIGNKEY_NONE;
}
ecc_key *gen_ecdsa_priv_key(unsigned int bit_size) {
const ltc_ecc_set_type *dp = NULL; /* curve domain parameters */
ecc_key *new_key = NULL;
switch (bit_size) {
#ifdef DROPBEAR_ECC_256
case 256:
dp = ecc_curve_nistp256.dp;
break;
#endif
#ifdef DROPBEAR_ECC_384
case 384:
dp = ecc_curve_nistp384.dp;
break;
#endif
#ifdef DROPBEAR_ECC_521
case 521:
dp = ecc_curve_nistp521.dp;
break;
#endif
}
if (!dp) {
dropbear_exit("Key size %d isn't valid. Try "
#ifdef DROPBEAR_ECC_256
"256 "
#endif
#ifdef DROPBEAR_ECC_384
"384 "
#endif
#ifdef DROPBEAR_ECC_521
"521 "
#endif
, bit_size);
}
new_key = m_malloc(sizeof(*new_key));
if (ecc_make_key_ex(NULL, dropbear_ltc_prng, new_key, dp) != CRYPT_OK) {
dropbear_exit("ECC error");
}
return new_key;
}
ecc_key *buf_get_ecdsa_pub_key(buffer* buf) {
unsigned char *key_ident = NULL, *identifier = NULL;
unsigned int key_ident_len, identifier_len;
buffer *q_buf = NULL;
struct dropbear_ecc_curve **curve;
ecc_key *new_key = NULL;
/* string "ecdsa-sha2-[identifier]" */
key_ident = buf_getstring(buf, &key_ident_len);
/* string "[identifier]" */
identifier = buf_getstring(buf, &identifier_len);
if (key_ident_len != identifier_len + strlen("ecdsa-sha2-")) {
TRACE(("Bad identifier lengths"))
goto out;
}
if (memcmp(&key_ident[strlen("ecdsa-sha2-")], identifier, identifier_len) != 0) {
TRACE(("mismatching identifiers"))
goto out;
}
for (curve = dropbear_ecc_curves; *curve; curve++) {
if (memcmp(identifier, (char*)(*curve)->name, strlen((char*)(*curve)->name)) == 0) {
break;
}
}
if (!*curve) {
TRACE(("couldn't match ecc curve"))
goto out;
}
/* string Q */
q_buf = buf_getstringbuf(buf);
new_key = buf_get_ecc_raw_pubkey(q_buf, *curve);
out:
m_free(key_ident);
m_free(identifier);
if (q_buf) {
buf_free(q_buf);
q_buf = NULL;
}
TRACE(("leave buf_get_ecdsa_pub_key"))
return new_key;
}
ecc_key *buf_get_ecdsa_priv_key(buffer *buf) {
ecc_key *new_key = NULL;
TRACE(("enter buf_get_ecdsa_priv_key"))
new_key = buf_get_ecdsa_pub_key(buf);
if (!new_key) {
return NULL;
}
if (buf_getmpint(buf, new_key->k) != DROPBEAR_SUCCESS) {
ecc_free(new_key);
return NULL;
}
return new_key;
}
void buf_put_ecdsa_pub_key(buffer *buf, ecc_key *key) {
struct dropbear_ecc_curve *curve = NULL;
unsigned char key_ident[30];
curve = curve_for_dp(key->dp);
snprintf((char*)key_ident, sizeof(key_ident), "ecdsa-sha2-%s", curve->name);
buf_putstring(buf, key_ident, strlen(key_ident));
buf_putstring(buf, curve->name, strlen(curve->name));
buf_put_ecc_raw_pubkey_string(buf, key);
}
void buf_put_ecdsa_priv_key(buffer *buf, ecc_key *key) {
buf_put_ecdsa_pub_key(buf, key);
buf_putmpint(buf, key->k);
}
void buf_put_ecdsa_sign(buffer *buf, ecc_key *key, buffer *data_buf) {
/* Based on libtomcrypt's ecc_sign_hash but without the asn1 */
int err = DROPBEAR_FAILURE;
struct dropbear_ecc_curve *curve = NULL;
hash_state hs;
unsigned char hash[64];
void *e = NULL, *p = NULL, *s = NULL, *r;
unsigned char key_ident[30];
buffer *sigbuf = NULL;
TRACE(("buf_put_ecdsa_sign"))
curve = curve_for_dp(key->dp);
if (ltc_init_multi(&r, &s, &p, &e, NULL) != CRYPT_OK) {
goto out;
}
curve->hash_desc->init(&hs);
curve->hash_desc->process(&hs, data_buf->data, data_buf->len);
curve->hash_desc->done(&hs, hash);
if (ltc_mp.unsigned_read(e, hash, curve->hash_desc->hashsize) != CRYPT_OK) {
goto out;
}
if (ltc_mp.read_radix(p, (char *)key->dp->order, 16) != CRYPT_OK) {
goto out;
}
for (;;) {
ecc_key R_key; /* ephemeral key */
if (ecc_make_key_ex(NULL, dropbear_ltc_prng, &R_key, key->dp) != CRYPT_OK) {
goto out;
}
if (ltc_mp.mpdiv(R_key.pubkey.x, p, NULL, r) != CRYPT_OK) {
goto out;
}
if (ltc_mp.compare_d(r, 0) == LTC_MP_EQ) {
/* try again */
ecc_free(&R_key);
continue;
}
/* k = 1/k */
if (ltc_mp.invmod(R_key.k, p, R_key.k) != CRYPT_OK) {
goto out;
}
/* s = xr */
if (ltc_mp.mulmod(key->k, r, p, s) != CRYPT_OK) {
goto out;
}
/* s = e + xr */
if (ltc_mp.add(e, s, s) != CRYPT_OK) {
goto out;
}
if (ltc_mp.mpdiv(s, p, NULL, s) != CRYPT_OK) {
goto out;
}
/* s = (e + xr)/k */
if (ltc_mp.mulmod(s, R_key.k, p, s) != CRYPT_OK) {
goto out;
}
ecc_free(&R_key);
if (ltc_mp.compare_d(s, 0) != LTC_MP_EQ) {
break;
}
}
snprintf((char*)key_ident, sizeof(key_ident), "ecdsa-sha2-%s", curve->name);
buf_putstring(buf, key_ident, strlen(key_ident));
/* enough for nistp521 */
sigbuf = buf_new(200);
buf_putmpint(sigbuf, (mp_int*)r);
buf_putmpint(sigbuf, (mp_int*)s);
buf_putbufstring(buf, sigbuf);
err = DROPBEAR_SUCCESS;
out:
if (r && s && p && e) {
ltc_deinit_multi(r, s, p, e, NULL);
}
if (sigbuf) {
buf_free(sigbuf);
}
if (err == DROPBEAR_FAILURE) {
dropbear_exit("ECC error");
}
}
/* returns values in s and r
returns DROPBEAR_SUCCESS or DROPBEAR_FAILURE */
static int buf_get_ecdsa_verify_params(buffer *buf,
void *r, void* s) {
int ret = DROPBEAR_FAILURE;
unsigned int sig_len;
unsigned int sig_pos;
sig_len = buf_getint(buf);
sig_pos = buf->pos;
if (buf_getmpint(buf, r) != DROPBEAR_SUCCESS) {
goto out;
}
if (buf_getmpint(buf, s) != DROPBEAR_SUCCESS) {
goto out;
}
if (buf->pos - sig_pos != sig_len) {
goto out;
}
ret = DROPBEAR_SUCCESS;
out:
return ret;
}
int buf_ecdsa_verify(buffer *buf, ecc_key *key, buffer *data_buf) {
/* Based on libtomcrypt's ecc_verify_hash but without the asn1 */
int ret = DROPBEAR_FAILURE;
hash_state hs;
struct dropbear_ecc_curve *curve = NULL;
unsigned char hash[64];
ecc_point *mG = NULL, *mQ = NULL;
void *r = NULL, *s = NULL, *v = NULL, *w = NULL, *u1 = NULL, *u2 = NULL,
*e = NULL, *p = NULL, *m = NULL;
void *mp = NULL;
/* verify
*
* w = s^-1 mod n
* u1 = xw
* u2 = rw
* X = u1*G + u2*Q
* v = X_x1 mod n
* accept if v == r
*/
TRACE(("buf_ecdsa_verify"))
curve = curve_for_dp(key->dp);
mG = ltc_ecc_new_point();
mQ = ltc_ecc_new_point();
if (ltc_init_multi(&r, &s, &v, &w, &u1, &u2, &p, &e, &m, NULL) != CRYPT_OK
|| !mG
|| !mQ) {
dropbear_exit("ECC error");
}
if (buf_get_ecdsa_verify_params(buf, r, s) != DROPBEAR_SUCCESS) {
goto out;
}
curve->hash_desc->init(&hs);
curve->hash_desc->process(&hs, data_buf->data, data_buf->len);
curve->hash_desc->done(&hs, hash);
if (ltc_mp.unsigned_read(e, hash, curve->hash_desc->hashsize) != CRYPT_OK) {
goto out;
}
/* get the order */
if (ltc_mp.read_radix(p, (char *)key->dp->order, 16) != CRYPT_OK) {
goto out;
}
/* get the modulus */
if (ltc_mp.read_radix(m, (char *)key->dp->prime, 16) != CRYPT_OK) {
goto out;
}
/* check for zero */
if (ltc_mp.compare_d(r, 0) == LTC_MP_EQ
|| ltc_mp.compare_d(s, 0) == LTC_MP_EQ
|| ltc_mp.compare(r, p) != LTC_MP_LT
|| ltc_mp.compare(s, p) != LTC_MP_LT) {
goto out;
}
/* w = s^-1 mod n */
if (ltc_mp.invmod(s, p, w) != CRYPT_OK) {
goto out;
}
/* u1 = ew */
if (ltc_mp.mulmod(e, w, p, u1) != CRYPT_OK) {
goto out;
}
/* u2 = rw */
if (ltc_mp.mulmod(r, w, p, u2) != CRYPT_OK) {
goto out;
}
/* find mG and mQ */
if (ltc_mp.read_radix(mG->x, (char *)key->dp->Gx, 16) != CRYPT_OK) {
goto out;
}
if (ltc_mp.read_radix(mG->y, (char *)key->dp->Gy, 16) != CRYPT_OK) {
goto out;
}
if (ltc_mp.set_int(mG->z, 1) != CRYPT_OK) {
goto out;
}
if (ltc_mp.copy(key->pubkey.x, mQ->x) != CRYPT_OK
|| ltc_mp.copy(key->pubkey.y, mQ->y) != CRYPT_OK
|| ltc_mp.copy(key->pubkey.z, mQ->z) != CRYPT_OK) {
goto out;
}
/* compute u1*mG + u2*mQ = mG */
if (ltc_mp.ecc_mul2add == NULL) {
if (ltc_mp.ecc_ptmul(u1, mG, mG, m, 0) != CRYPT_OK) {
goto out;
}
if (ltc_mp.ecc_ptmul(u2, mQ, mQ, m, 0) != CRYPT_OK) {
goto out;
}
/* find the montgomery mp */
if (ltc_mp.montgomery_setup(m, &mp) != CRYPT_OK) {
goto out;
}
/* add them */
if (ltc_mp.ecc_ptadd(mQ, mG, mG, m, mp) != CRYPT_OK) {
goto out;
}
/* reduce */
if (ltc_mp.ecc_map(mG, m, mp) != CRYPT_OK) {
goto out;
}
} else {
/* use Shamir's trick to compute u1*mG + u2*mQ using half of the doubles */
if (ltc_mp.ecc_mul2add(mG, u1, mQ, u2, mG, m) != CRYPT_OK) {
goto out;
}
}
/* v = X_x1 mod n */
if (ltc_mp.mpdiv(mG->x, p, NULL, v) != CRYPT_OK) {
goto out;
}
/* does v == r */
if (ltc_mp.compare(v, r) == LTC_MP_EQ) {
ret = DROPBEAR_SUCCESS;
}
out:
ltc_ecc_del_point(mG);
ltc_ecc_del_point(mQ);
mp_clear_multi(r, s, v, w, u1, u2, p, e, m, NULL);
if (mp != NULL) {
ltc_mp.montgomery_deinit(mp);
}
return ret;
}
#endif /* DROPBEAR_ECDSA */
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