/**
* int main()
*
* Invokes the backend, waits until it has successfully detached from the I/O ports,
* and then quits.
*/
int main() {
/** Block SIGUSR1, SIGCHLD until we can handle them. */
sigset_t waitset;
sigemptyset(&waitset);
sigaddset(&waitset, SIGUSR1);
sigaddset(&waitset, SIGCHLD);
sigprocmask(SIG_BLOCK, &waitset, NULL);
/** Install signal handlers for those signals. */
struct sigaction actions;
sigemptyset(&actions.sa_mask);
actions.sa_flags = SA_SIGINFO;
actions.sa_sigaction = dummy_signal_action;
sigaction(SIGUSR1, &actions, NULL);
sigaction(SIGCHLD, &actions, NULL);
/** Fork the child */
pid_t childpid = fork();
if(childpid < 0) {
perror("Could not fork() child:");
return 1;
}
if(childpid == 0) {
/* Detach session, setup file descriptors, spawn Racket process. */
if(setsid() < 0) {
perror("Could not detach session:");
return 1;
}
#ifndef NDEBUG
putenv("PLTSTDERR=debug");
#endif
// Prefer build directory if debug build.
if(!IS_INSTALLED() && access(SEASHELL_DEBUG_MAIN, F_OK) != -1) {
char * argv2[] = {SEASHELL_DEBUG_MAIN, "-s", NULL};
execv(SEASHELL_DEBUG_MAIN, argv2);
perror("Could not execv() the Seashell backend:");
return 1;
}
// Main case if not in debug mode (fall through if)
char * argv[] = {SEASHELL_MAIN, "-s", NULL};
execv(SEASHELL_MAIN, argv);
perror("Could not execv() the Seashell backend:");
return 1;
} else {
/* Setup file descriptors, pass key and port, exit. */
while (true) {
siginfo_t info;
int result = sigwaitinfo(&waitset, &info);
if (result < 0) {
if (errno == EINTR) {
continue;
} else {
perror("sigwaitinfo failed with:");
return 1;
}
} else {
/** Wait for the process to quit (successfully) or detach. */
if (info.si_signo == SIGCHLD) {
int status = 0;
result = waitpid(childpid, &status, WCONTINUED | WUNTRACED);
if (result < 0) {
perror("wait failed with:");
return 1;
} else if (WIFEXITED(status)) {
return WEXITSTATUS(status);
}
} else if (info.si_signo == SIGUSR1) {
return 0;
}
}
}
}
}
/**
* seashell_tunnel_connect_password (const char* host, const char* user, const char* password, int* error)
* Connects to the host via SSH on port 22, and launches a Seashell backend instance for that user
* on the host.
*
* Consults /etc/seashell_hosts for host's SSH public keys. If this file does not exist,
* this function will fail for security reasons. /etc/seashell_hosts is a standard
* OpenSSH known_hosts file.
*
* Arguments:
* host - Host to connect to.
* user - User to run as.
* password - User's password.
* error - [optional] denotes error on failure.
* remote_addr - Address to which the remote IP address will
* be written. Reserve 128 bytes.
* family - Address family.
* target - Target to execute.
*
* Returns:
* Handle to connection object on success, NULL otherwise.
* If error is NOT null, error will hold more detailed error information.
*/
struct seashell_connection* seashell_tunnel_connect_password (const char* host,
const char* user,
const char* password,
int* error,
char * remote_addr,
int* family,
char* target) {
struct addrinfo hints;
struct addrinfo *results, *rp;
int sockfd;
int i, e;
struct seashell_connection* result = NULL;
/* Resolve the host's address.
* See getaddrinfo(3) for how this works.
*/
memset(&hints, 0, sizeof(hints));
hints.ai_family = AF_UNSPEC;
hints.ai_socktype = SOCK_STREAM;
hints.ai_flags = 0;
hints.ai_protocol = 0;
e = getaddrinfo(host, "22", &hints, &results);
if (e != 0) {
SET_ERROR(TUNNEL_ERROR_RESOLV);
return NULL;
}
for (rp = results; rp != NULL; rp = rp->ai_next) {
sockfd = socket(rp->ai_family, rp->ai_socktype, rp->ai_protocol);
if (sockfd == -1)
continue;
if (connect(sockfd, rp->ai_addr, rp->ai_addrlen) != -1)
break;
close(sockfd);
}
/* Write address that we're connecting to into
* remote_addr.
*/
if(rp != NULL) {
*family = rp->ai_family;
switch(rp->ai_family) {
case AF_INET:
if(inet_ntop(rp->ai_family, &((struct sockaddr_in *)rp->ai_addr)->sin_addr, remote_addr, 128) == NULL) {
SET_ERROR(TUNNEL_ERROR_RESOLV);
return NULL;
}
break;
case AF_INET6:
if(inet_ntop(rp->ai_family, &((struct sockaddr_in6 *)rp->ai_addr)->sin6_addr, remote_addr, 128) == NULL) {
SET_ERROR(TUNNEL_ERROR_RESOLV);
return NULL;
}
break;
default:
SET_ERROR(TUNNEL_ERROR_RESOLV);
return NULL;
}
}
freeaddrinfo(results);
/* Either rp == NULL, in which case we failed at connecting,
* or sockfd holds our socket.
*/
if (rp == NULL) {
SET_ERROR(TUNNEL_ERROR_CONNECT);
return NULL;
}
/** Set up the session */
LIBSSH2_SESSION* session;
LIBSSH2_CHANNEL* channel;
LIBSSH2_KNOWNHOSTS* hosts;
size_t len;
int type;
session = libssh2_session_init();
if (!session) {
SET_ERROR(TUNNEL_ERROR_SESSION_START);
goto session_teardown;
}
e = libssh2_session_handshake(session, sockfd);
if (e) {
SET_ERROR(TUNNEL_ERROR_SESSION_HANDSHAKE);
goto session_teardown;
}
hosts = libssh2_knownhost_init(session);
if (!hosts) {
SET_ERROR(TUNNEL_ERROR_HOSTS_FILE);
goto session_teardown;
}
if (!IS_INSTALLED() && access(DEBUG_HOSTS_FILE, F_OK) != -1) {
libssh2_knownhost_readfile(hosts, DEBUG_HOSTS_FILE, LIBSSH2_KNOWNHOST_FILE_OPENSSH);
} else {
libssh2_knownhost_readfile(hosts, HOSTS_FILE, LIBSSH2_KNOWNHOST_FILE_OPENSSH);
}
const char* fingerprint = libssh2_session_hostkey(session, &len, &type);
if (!fingerprint || type == LIBSSH2_HOSTKEY_TYPE_UNKNOWN) {
libssh2_knownhost_free(hosts);
SET_ERROR(TUNNEL_ERROR_HOST);
goto session_teardown;
}
struct libssh2_knownhost *hostkey;
/** NOTE: Documentation is buggy. hostkey MUST be passed. */
int check = libssh2_knownhost_check(hosts, host, fingerprint, len,
LIBSSH2_KNOWNHOST_TYPE_PLAIN | LIBSSH2_KNOWNHOST_KEYENC_RAW, &hostkey);
if (check != LIBSSH2_KNOWNHOST_CHECK_MATCH) {
int keytype = 0;
switch (type) {
case LIBSSH2_HOSTKEY_TYPE_RSA:
keytype = LIBSSH2_KNOWNHOST_KEY_SSHRSA;
break;
case LIBSSH2_HOSTKEY_TYPE_DSS:
keytype = LIBSSH2_KNOWNHOST_KEY_SSHRSA;
break;
}
if (keytype) {
libssh2_knownhost_addc(hosts, host, NULL, fingerprint, len,
"Generated from Seashell Tunnel", strlen("Generated from Seashell Tunnel"),
LIBSSH2_KNOWNHOST_TYPE_PLAIN | LIBSSH2_KNOWNHOST_KEYENC_RAW
| (type == LIBSSH2_HOSTKEY_TYPE_RSA ? LIBSSH2_KNOWNHOST_KEY_SSHRSA : LIBSSH2_KNOWNHOST_KEY_SSHDSS),
NULL);
libssh2_knownhost_writefile(hosts, DUMP_FILE, LIBSSH2_KNOWNHOST_FILE_OPENSSH);
fprintf(stderr, "%s: Check SSH key for %s! Keys written to %s\n", user, host, DUMP_FILE);
} else {
fprintf(stderr, "%s: Check SSH key for %s!\n", user, host, DUMP_FILE);
fprintf(stderr, "%s: Keys not written to file - contact Seashell Maintainers to add support for the LibSSH2 key format %d\n", user, type);
}
libssh2_knownhost_free(hosts);
SET_ERROR(TUNNEL_ERROR_HOST);
goto session_teardown;
}
libssh2_knownhost_free(hosts);
FPRINTF_IF_DEBUG(stderr, "%s: Host check passed for %s (fingerprint type %d) - ", user, host, type);
for(i = 0; i < 20; i++) {
FPRINTF_IF_DEBUG(stderr, "%02X ", (unsigned char)fingerprint[i]);
}
FPRINTF_IF_DEBUG(stderr, "\n");
e = libssh2_userauth_password(session, user, password);
if (e) {
FPRINTF_IF_DEBUG(stderr, "%s: Error authenticating: %d\n", user, e);
SET_ERROR(TUNNEL_ERROR_CREDS);
goto session_teardown;
}
channel = libssh2_channel_open_session(session);
if (!channel) {
SET_ERROR(TUNNEL_ERROR_CHANNEL_OPEN);
goto session_teardown;
}
/**
* Ideally we'd have a subsystem configured,
* as I don't see a good way of pulling out of ssh2
* if the target does not exist.
*/
e = libssh2_channel_exec(channel, target);
if (e) {
SET_ERROR(TUNNEL_ERROR_LAUNCH_SEASHELL);
goto channel_teardown;
}
result = malloc(sizeof(struct seashell_connection));
if (!result) {
SET_ERROR(TUNNEL_ERROR_SESSION_START);
goto channel_teardown;
}
result->sockfd = sockfd;
result->session = session;
result->channel = channel;
goto end;
channel_teardown:
libssh2_channel_free(channel);
session_teardown:
libssh2_session_free(session);
close(sockfd);
end:
return result;
}
