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Make sk-ecdsa call buf_ecdsa_verify

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This reduces code duplication, the SK code just handles the
different message format.
This commit is contained in:
Matt Johnston 2022-01-22 14:45:19 +08:00
parent 2634c4586b
commit cc481a646d
3 changed files with 11 additions and 141 deletions
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2
ecdsa.c
View File

@ -254,7 +254,7 @@ out:
/* returns values in s and r
returns DROPBEAR_SUCCESS or DROPBEAR_FAILURE */
int buf_get_ecdsa_verify_params(buffer *buf,
static int buf_get_ecdsa_verify_params(buffer *buf,
void *r, void* s) {
int ret = DROPBEAR_FAILURE;
unsigned int sig_len;

2
ecdsa.h
View File

@ -26,8 +26,6 @@ void buf_put_ecdsa_pub_key(buffer *buf, ecc_key *key);
void buf_put_ecdsa_priv_key(buffer *buf, ecc_key *key);
enum signkey_type ecdsa_signkey_type(const ecc_key * key);
int buf_get_ecdsa_verify_params(buffer *buf, void *r, void* s);
void buf_put_ecdsa_sign(buffer *buf, const ecc_key *key, const buffer *data_buf);
int buf_ecdsa_verify(buffer *buf, const ecc_key *key, const buffer *data_buf);
/* Returns 1 on success */

148
sk-ecdsa.c
View File

@ -8,47 +8,22 @@
#include "sk-ecdsa.h"
int buf_sk_ecdsa_verify(buffer *buf, const ecc_key *key, const buffer *data_buf, const char* app, unsigned int applen) {
/* 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];
unsigned char subhash[SHA256_HASH_SIZE];
buffer *sk_buffer = NULL;
buffer *sk_buffer = NULL, *sig_buffer = NULL;
unsigned char flags;
unsigned int counter;
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
*/
int ret;
TRACE(("buf_sk_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;
}
/* from https://github.com/openssh/openssh-portable/blob/master/PROTOCOL.u2f */
/* ecdsa signature to verify (r, s) */
sig_buffer = buf_getbuf(buf);
flags = buf_getbyte (buf);
counter = buf_getint (buf);
/* create the message to be signed */
sk_buffer = buf_new (2*SHA256_HASH_SIZE+5);
sha256_init (&hs);
sha256_process (&hs, app, applen);
@ -61,114 +36,11 @@ int buf_sk_ecdsa_verify(buffer *buf, const ecc_key *key, const buffer *data_buf,
sha256_done (&hs, subhash);
buf_putbytes (sk_buffer, subhash, sizeof (subhash));
curve->hash_desc->init(&hs);
curve->hash_desc->process(&hs, sk_buffer->data, sk_buffer->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);
ltc_deinit_multi(r, s, v, w, u1, u2, p, e, m, NULL);
if (mp != NULL) {
ltc_mp.montgomery_deinit(mp);
}
if (sk_buffer) {
ret = buf_ecdsa_verify(sig_buffer, key, sk_buffer);
buf_free(sk_buffer);
}
buf_free(sig_buffer);
TRACE(("leave buf_sk_ecdsa_verify, ret=%d", ret))
return ret;
}