static int
input_kex_c25519_init(int type, u_int32_t seq, struct ssh *ssh)
{
struct kex *kex = ssh->kex;
struct sshkey *server_host_private, *server_host_public;
struct sshbuf *shared_secret = NULL;
u_char *server_host_key_blob = NULL, *signature = NULL;
u_char server_key[CURVE25519_SIZE];
u_char *client_pubkey = NULL;
u_char server_pubkey[CURVE25519_SIZE];
u_char hash[SSH_DIGEST_MAX_LENGTH];
size_t slen, pklen, sbloblen, hashlen;
int r;
/* generate private key */
kexc25519_keygen(server_key, server_pubkey);
#ifdef DEBUG_KEXECDH
dump_digest("server private key:", server_key, sizeof(server_key));
#endif
if (kex->load_host_public_key == NULL ||
kex->load_host_private_key == NULL) {
r = SSH_ERR_INVALID_ARGUMENT;
goto out;
}
server_host_public = kex->load_host_public_key(kex->hostkey_type,
kex->hostkey_nid, ssh);
server_host_private = kex->load_host_private_key(kex->hostkey_type,
kex->hostkey_nid, ssh);
if (server_host_public == NULL) {
r = SSH_ERR_NO_HOSTKEY_LOADED;
goto out;
}
if ((r = sshpkt_get_string(ssh, &client_pubkey, &pklen)) != 0 ||
(r = sshpkt_get_end(ssh)) != 0)
goto out;
if (pklen != CURVE25519_SIZE) {
r = SSH_ERR_SIGNATURE_INVALID;
goto out;
}
#ifdef DEBUG_KEXECDH
dump_digest("client public key:", client_pubkey, CURVE25519_SIZE);
#endif
if ((shared_secret = sshbuf_new()) == NULL) {
r = SSH_ERR_ALLOC_FAIL;
goto out;
}
if ((r = kexc25519_shared_key(server_key, client_pubkey,
shared_secret)) < 0)
goto out;
/* calc H */
if ((r = sshkey_to_blob(server_host_public, &server_host_key_blob,
&sbloblen)) != 0)
goto out;
hashlen = sizeof(hash);
if ((r = kex_c25519_hash(
kex->hash_alg,
kex->client_version_string,
kex->server_version_string,
sshbuf_ptr(kex->peer), sshbuf_len(kex->peer),
sshbuf_ptr(kex->my), sshbuf_len(kex->my),
server_host_key_blob, sbloblen,
client_pubkey,
server_pubkey,
sshbuf_ptr(shared_secret), sshbuf_len(shared_secret),
hash, &hashlen)) < 0)
goto out;
/* save session id := H */
if (kex->session_id == NULL) {
kex->session_id_len = hashlen;
kex->session_id = malloc(kex->session_id_len);
if (kex->session_id == NULL) {
r = SSH_ERR_ALLOC_FAIL;
goto out;
}
memcpy(kex->session_id, hash, kex->session_id_len);
}
/* sign H */
if ((r = kex->sign(server_host_private, server_host_public, &signature,
&slen, hash, hashlen, kex->hostkey_alg, ssh->compat)) < 0)
goto out;
/* send server hostkey, ECDH pubkey 'Q_S' and signed H */
if ((r = sshpkt_start(ssh, SSH2_MSG_KEX_ECDH_REPLY)) != 0 ||
(r = sshpkt_put_string(ssh, server_host_key_blob, sbloblen)) != 0 ||
(r = sshpkt_put_string(ssh, server_pubkey, sizeof(server_pubkey))) != 0 ||
(r = sshpkt_put_string(ssh, signature, slen)) != 0 ||
(r = sshpkt_send(ssh)) != 0)
goto out;
if ((r = kex_derive_keys(ssh, hash, hashlen, shared_secret)) == 0)
r = kex_send_newkeys(ssh);
out:
explicit_bzero(hash, sizeof(hash));
explicit_bzero(server_key, sizeof(server_key));
free(server_host_key_blob);
free(signature);
free(client_pubkey);
sshbuf_free(shared_secret);
return r;
}
static int
input_kex_c25519_reply(int type, u_int32_t seq, struct ssh *ssh)
{
struct kex *kex = ssh->kex;
struct sshkey *server_host_key = NULL;
struct sshbuf *shared_secret = NULL;
u_char *server_pubkey = NULL;
u_char *server_host_key_blob = NULL, *signature = NULL;
u_char *hash;
size_t slen, pklen, sbloblen, hashlen;
int r;
if (kex->verify_host_key == NULL) {
r = SSH_ERR_INVALID_ARGUMENT;
goto out;
}
/* hostkey */
if ((r = sshpkt_get_string(ssh, &server_host_key_blob,
&sbloblen)) != 0 ||
(r = sshkey_from_blob(server_host_key_blob, sbloblen,
&server_host_key)) != 0)
goto out;
if (server_host_key->type != kex->hostkey_type) {
r = SSH_ERR_KEY_TYPE_MISMATCH;
goto out;
}
if (kex->verify_host_key(server_host_key, ssh) == -1) {
r = SSH_ERR_SIGNATURE_INVALID;
goto out;
}
/* Q_S, server public key */
/* signed H */
if ((r = sshpkt_get_string(ssh, &server_pubkey, &pklen)) != 0 ||
(r = sshpkt_get_string(ssh, &signature, &slen)) != 0 ||
(r = sshpkt_get_end(ssh)) != 0)
goto out;
if (pklen != CURVE25519_SIZE) {
r = SSH_ERR_SIGNATURE_INVALID;
goto out;
}
#ifdef DEBUG_KEXECDH
dump_digest("server public key:", server_pubkey, CURVE25519_SIZE);
#endif
if ((shared_secret = sshbuf_new()) == NULL) {
r = SSH_ERR_ALLOC_FAIL;
goto out;
}
if ((r = kexc25519_shared_key(kex->c25519_client_key, server_pubkey,
shared_secret)) < 0)
goto out;
/* calc and verify H */
if ((r = kex_c25519_hash(
kex->hash_alg,
kex->client_version_string,
kex->server_version_string,
sshbuf_ptr(kex->my), sshbuf_len(kex->my),
sshbuf_ptr(kex->peer), sshbuf_len(kex->peer),
server_host_key_blob, sbloblen,
kex->c25519_client_pubkey,
server_pubkey,
sshbuf_ptr(shared_secret), sshbuf_len(shared_secret),
&hash, &hashlen)) < 0)
goto out;
if ((r = sshkey_verify(server_host_key, signature, slen, hash, hashlen,
ssh->compat)) != 0)
goto out;
/* save session id */
if (kex->session_id == NULL) {
kex->session_id_len = hashlen;
kex->session_id = malloc(kex->session_id_len);
if (kex->session_id == NULL) {
r = SSH_ERR_ALLOC_FAIL;
goto out;
}
memcpy(kex->session_id, hash, kex->session_id_len);
}
if ((r = kex_derive_keys(ssh, hash, hashlen, sshbuf_ptr(shared_secret),
sshbuf_len(shared_secret))) == 0)
r = kex_send_newkeys(ssh);
r = 0;
out:
explicit_bzero(kex->c25519_client_key, sizeof(kex->c25519_client_key));
free(server_host_key_blob);
free(server_pubkey);
free(signature);
sshkey_free(server_host_key);
sshbuf_free(shared_secret);
return r;
}
