int
kex_send_kexinit(struct ssh *ssh)
{
u_char *cookie;
struct kex *kex = ssh->kex;
int r;
if (kex == NULL)
return SSH_ERR_INTERNAL_ERROR;
if (kex->flags & KEX_INIT_SENT)
return 0;
kex->done = 0;
/* generate a random cookie */
if (sshbuf_len(kex->my) < KEX_COOKIE_LEN)
return SSH_ERR_INVALID_FORMAT;
if ((cookie = sshbuf_mutable_ptr(kex->my)) == NULL)
return SSH_ERR_INTERNAL_ERROR;
arc4random_buf(cookie, KEX_COOKIE_LEN);
if ((r = sshpkt_start(ssh, SSH2_MSG_KEXINIT)) != 0)
return r;
if ((r = sshpkt_put(ssh, sshbuf_ptr(kex->my),
sshbuf_len(kex->my))) != 0)
return r;
if ((r = sshpkt_send(ssh)) != 0)
return r;
debug("SSH2_MSG_KEXINIT sent");
kex->flags |= KEX_INIT_SENT;
return 0;
}
void
ssh_packet_put_raw(struct ssh *ssh, const void *buf, u_int len)
{
int r;
if ((r = sshpkt_put(ssh, buf, len)) != 0)
fatal("%s: %s", __func__, ssh_err(r));
}
/*
* Computes the proper response to a RSA challenge, and sends the response to
* the server.
*/
static void
respond_to_rsa_challenge(struct ssh *ssh, BIGNUM * challenge, RSA * prv)
{
u_char buf[32], response[16];
MD5_CTX md;
int r, len;
/* Decrypt the challenge using the private key. */
/* XXX think about Bleichenbacher, too */
if ((r = rsa_private_decrypt(challenge, challenge, prv)) != 0) {
ssh_packet_disconnect(ssh, "%s: rsa_private_decrypt: %s",
__func__, ssh_err(r));
}
/* Compute the response. */
/* The response is MD5 of decrypted challenge plus session id. */
len = BN_num_bytes(challenge);
if (len <= 0 || (u_int)len > sizeof(buf))
ssh_packet_disconnect(ssh,
"respond_to_rsa_challenge: bad challenge length %d", len);
memset(buf, 0, sizeof(buf));
BN_bn2bin(challenge, buf + sizeof(buf) - len);
MD5_Init(&md);
MD5_Update(&md, buf, 32);
MD5_Update(&md, session_id, 16);
MD5_Final(response, &md);
debug("Sending response to host key RSA challenge.");
/* Send the response back to the server. */
if ((r = sshpkt_start(ssh, SSH_CMSG_AUTH_RSA_RESPONSE)) != 0 ||
(r = sshpkt_put(ssh, &response, sizeof(response))) != 0 ||
(r = sshpkt_send(ssh)) != 0)
fatal("%s: %s", __func__, ssh_err(r));
ssh_packet_write_wait(ssh);
memset(buf, 0, sizeof(buf));
memset(response, 0, sizeof(response));
memset(&md, 0, sizeof(md));
}
/*
* Checks if the user has an authentication agent, and if so, tries to
* authenticate using the agent.
*/
static int
try_agent_authentication(struct ssh *ssh)
{
int r, type, agent_fd, ret = 0;
u_char response[16];
size_t i;
BIGNUM *challenge;
struct ssh_identitylist *idlist = NULL;
/* Get connection to the agent. */
if ((r = ssh_get_authentication_socket(&agent_fd)) != 0) {
if (r != SSH_ERR_AGENT_NOT_PRESENT)
debug("%s: ssh_get_authentication_socket: %s",
__func__, ssh_err(r));
return 0;
}
if ((challenge = BN_new()) == NULL)
fatal("try_agent_authentication: BN_new failed");
/* Loop through identities served by the agent. */
if ((r = ssh_fetch_identitylist(agent_fd, 1, &idlist)) != 0) {
if (r != SSH_ERR_AGENT_NO_IDENTITIES)
debug("%s: ssh_fetch_identitylist: %s",
__func__, ssh_err(r));
goto out;
}
for (i = 0; i < idlist->nkeys; i++) {
/* Try this identity. */
debug("Trying RSA authentication via agent with '%.100s'",
idlist->comments[i]);
/*
* Tell the server that we are willing to authenticate
* using this key.
*/
if ((r = sshpkt_start(ssh, SSH_CMSG_AUTH_RSA)) != 0 ||
(r = sshpkt_put_bignum1(ssh, idlist->keys[i]->rsa->n)) != 0 ||
(r = sshpkt_send(ssh)) != 0)
fatal("%s: %s", __func__, ssh_err(r));
ssh_packet_write_wait(ssh);
/* Wait for server's response. */
type = ssh_packet_read(ssh);
/* The server sends failure if it doesn't like our key or
does not support RSA authentication. */
if (type == SSH_SMSG_FAILURE) {
debug("Server refused our key.");
continue;
}
/* Otherwise it should have sent a challenge. */
if (type != SSH_SMSG_AUTH_RSA_CHALLENGE)
ssh_packet_disconnect(ssh, "Protocol error during RSA "
"authentication: %d", type);
if ((r = sshpkt_get_bignum1(ssh, challenge)) != 0 ||
(r = sshpkt_get_end(ssh)) != 0)
fatal("%s: %s", __func__, ssh_err(r));
debug("Received RSA challenge from server.");
/* Ask the agent to decrypt the challenge. */
if ((r = ssh_decrypt_challenge(agent_fd, idlist->keys[i],
challenge, session_id, response)) != 0) {
/*
* The agent failed to authenticate this identifier
* although it advertised it supports this. Just
* return a wrong value.
*/
logit("Authentication agent failed to decrypt "
"challenge: %s", ssh_err(r));
memset(response, 0, sizeof(response));
}
debug("Sending response to RSA challenge.");
/* Send the decrypted challenge back to the server. */
if ((r = sshpkt_start(ssh, SSH_CMSG_AUTH_RSA_RESPONSE)) != 0 ||
(r = sshpkt_put(ssh, &response, sizeof(response))) != 0 ||
(r = sshpkt_send(ssh)) != 0)
fatal("%s: %s", __func__, ssh_err(r));
ssh_packet_write_wait(ssh);
/* Wait for response from the server. */
type = ssh_packet_read(ssh);
/*
* The server returns success if it accepted the
* authentication.
*/
if (type == SSH_SMSG_SUCCESS) {
debug("RSA authentication accepted by server.");
ret = 1;
break;
} else if (type != SSH_SMSG_FAILURE)
ssh_packet_disconnect(ssh, "Protocol error waiting RSA auth "
"response: %d", type);
}
if (ret != 1)
debug("RSA authentication using agent refused.");
out:
ssh_free_identitylist(idlist);
ssh_close_authentication_socket(agent_fd);
BN_clear_free(challenge);
return ret;
}
static int
server_input_global_request(int type, u_int32_t seq, struct ssh *ssh)
{
char *rtype = NULL;
u_char want_reply;
int r, success = 0, allocated_listen_port = 0;
struct sshbuf *resp = NULL;
if ((r = sshpkt_get_cstring(ssh, &rtype, NULL)) != 0 ||
(r = sshpkt_get_u8(ssh, &want_reply)) != 0)
goto out;
debug("server_input_global_request: rtype %s want_reply %d", rtype, want_reply);
/* -R style forwarding */
if (strcmp(rtype, "tcpip-forward") == 0) {
struct authctxt *authctxt = ssh->authctxt;
struct Forward fwd;
if (authctxt->pw == NULL || !authctxt->valid)
fatal("server_input_global_request: no/invalid user");
memset(&fwd, 0, sizeof(fwd));
if ((r = sshpkt_get_cstring(ssh, &fwd.listen_host, NULL)) != 0 ||
(r = sshpkt_get_u32(ssh, &fwd.listen_port)) != 0)
goto out;
debug("server_input_global_request: tcpip-forward listen %s port %d",
fwd.listen_host, fwd.listen_port);
/* check permissions */
if ((options.allow_tcp_forwarding & FORWARD_REMOTE) == 0 ||
no_port_forwarding_flag ||
(!want_reply && fwd.listen_port == 0) ||
(fwd.listen_port != 0 && fwd.listen_port < IPPORT_RESERVED &&
authctxt->pw->pw_uid != 0)) {
success = 0;
ssh_packet_send_debug(ssh,
"Server has disabled port forwarding.");
} else {
/* Start listening on the port */
success = channel_setup_remote_fwd_listener(ssh, &fwd,
&allocated_listen_port, &options.fwd_opts);
}
free(fwd.listen_host);
if ((resp = sshbuf_new()) == NULL)
fatal("%s: sshbuf_new", __func__);
if (allocated_listen_port != 0 &&
(r = sshbuf_put_u32(resp, allocated_listen_port)) != 0)
fatal("%s: sshbuf_put_u32: %s", __func__, ssh_err(r));
} else if (strcmp(rtype, "cancel-tcpip-forward") == 0) {
struct Forward fwd;
memset(&fwd, 0, sizeof(fwd));
if ((r = sshpkt_get_cstring(ssh, &fwd.listen_host, NULL)) != 0 ||
(r = sshpkt_get_u32(ssh, &fwd.listen_port)) != 0)
goto out;
debug("%s: cancel-tcpip-forward addr %s port %d", __func__,
fwd.listen_host, fwd.listen_port);
success = channel_cancel_rport_listener(&fwd);
free(fwd.listen_host);
} else if (strcmp(rtype, "*****@*****.**") == 0) {
struct Forward fwd;
memset(&fwd, 0, sizeof(fwd));
if ((r = sshpkt_get_cstring(ssh, &fwd.listen_path, NULL)) != 0)
goto out;
debug("server_input_global_request: streamlocal-forward listen path %s",
fwd.listen_path);
/* check permissions */
if ((options.allow_streamlocal_forwarding & FORWARD_REMOTE) == 0
|| no_port_forwarding_flag) {
success = 0;
ssh_packet_send_debug(ssh, "Server has disabled port forwarding.");
} else {
/* Start listening on the socket */
success = channel_setup_remote_fwd_listener(ssh,
&fwd, NULL, &options.fwd_opts);
}
free(fwd.listen_path);
} else if (strcmp(rtype, "*****@*****.**") == 0) {
struct Forward fwd;
memset(&fwd, 0, sizeof(fwd));
if ((r = sshpkt_get_cstring(ssh, &fwd.listen_path, NULL)) != 0)
goto out;
debug("%s: cancel-streamlocal-forward path %s", __func__,
fwd.listen_path);
success = channel_cancel_rport_listener(&fwd);
free(fwd.listen_path);
} else if (strcmp(rtype, "*****@*****.**") == 0) {
no_more_sessions = 1;
success = 1;
} else if (strcmp(rtype, "*****@*****.**") == 0) {
success = server_input_hostkeys_prove(&resp);
}
if (want_reply) {
if ((r = sshpkt_start(ssh, success ?
SSH2_MSG_REQUEST_SUCCESS : SSH2_MSG_REQUEST_FAILURE)) != 0 ||
(success && resp != NULL &&
(r = sshpkt_put(ssh, sshbuf_ptr(resp), sshbuf_len(resp)))
!= 0) ||
(r = sshpkt_send(ssh)) != 0)
goto out;
ssh_packet_write_wait(ssh);
}
r = 0;
out:
free(rtype);
sshbuf_free(resp);
return r;
}
