1 #include <stdio.h>
2 #include <stdlib.h>
3 #include <unistd.h>
4 #include <libssh/libssh.h>
5 #include <sys/stat.h>
6 #include <sys/param.h>
7 #include <errno.h>
8 #include <grp.h>
9 #include <pwd.h>
10 #include <unistd.h>
11 #ifdef HAVE_CURSES_H
12 #include <curses.h>
13 #else
14 #include <ncurses.h>
15 #endif
16 #include <term.h>
17 #include <time.h>
18 #include <fcntl.h>
19 #include <sched.h>
20 #include <signal.h>
21 #include "tmate.h"
22
23 static char *cmdline;
24 static char *cmdline_end;
25
26 struct tmate_settings _tmate_settings = {
27 .keys_dir = TMATE_SSH_DEFAULT_KEYS_DIR,
28 .ssh_port = TMATE_SSH_DEFAULT_PORT,
29 .ssh_port_advertized = -1,
30 .websocket_hostname = NULL,
31 .bind_addr = NULL,
32 .websocket_port = TMATE_DEFAULT_WEBSOCKET_PORT,
33 .tmate_host = NULL,
34 .log_level = LOG_INFO,
35 .use_proxy_protocol = false,
36 };
37
38 struct tmate_settings *tmate_settings = &_tmate_settings;
39
40 extern int server_fd;
41 extern void server_send_exit(void);
request_server_termination(void)42 void request_server_termination(void)
43 {
44 if (server_fd) {
45 server_send_exit();
46 } else
47 exit(1);
48 }
49
usage(void)50 static void usage(void)
51 {
52 fprintf(stderr, "usage: tmate-ssh-server [-b ip] [-h hostname] [-k keys_dir] [-p listen_port] [-q ssh_port_advertized] [-w websocket_hostname] [-z websocket_port] [-x] [-v]\n");
53 }
54
get_full_hostname(void)55 static char* get_full_hostname(void)
56 {
57 struct addrinfo hints, *info;
58 char hostname[1024];
59 int gai_result;
60 char *ret;
61
62 if (gethostname(hostname, sizeof(hostname)) < 0)
63 tmate_fatal("cannot get hostname");
64 hostname[1023] = '\0';
65
66 memset(&hints, 0, sizeof hints);
67 hints.ai_family = AF_UNSPEC; /*either IPV4 or IPV6*/
68 hints.ai_socktype = SOCK_STREAM;
69 hints.ai_flags = AI_CANONNAME;
70
71 if ((gai_result = getaddrinfo(hostname, NULL, &hints, &info)) != 0) {
72 tmate_info("cannot lookup hostname: %s", gai_strerror(gai_result));
73 return xstrdup(hostname);
74 }
75
76 ret = xstrdup(info->ai_canonname);
77
78 freeaddrinfo(info);
79 return ret;
80 }
81 #include <langinfo.h>
82 #include <locale.h>
83
setup_locale(void)84 static void setup_locale(void)
85 {
86 const char *s;
87
88 if (setlocale(LC_CTYPE, "en_US.UTF-8") == NULL) {
89 if (setlocale(LC_CTYPE, "") == NULL)
90 tmate_fatal("invalid LC_ALL, LC_CTYPE or LANG");
91 s = nl_langinfo(CODESET);
92 if (strcasecmp(s, "UTF-8") != 0 &&
93 strcasecmp(s, "UTF8") != 0)
94 tmate_fatal("need UTF-8 locale (LC_CTYPE) but have %s", s);
95 }
96
97 setlocale(LC_TIME, "");
98 tzset();
99 }
100
main(int argc,char ** argv,char ** envp)101 int main(int argc, char **argv, char **envp)
102 {
103 int opt;
104
105 while ((opt = getopt(argc, argv, "b:h:k:p:q:w:z:xv")) != -1) {
106 switch (opt) {
107 case 'b':
108 tmate_settings->bind_addr = xstrdup(optarg);
109 break;
110 case 'h':
111 tmate_settings->tmate_host = xstrdup(optarg);
112 break;
113 case 'k':
114 tmate_settings->keys_dir = xstrdup(optarg);
115 break;
116 case 'p':
117 tmate_settings->ssh_port = atoi(optarg);
118 break;
119 case 'q':
120 tmate_settings->ssh_port_advertized = atoi(optarg);
121 break;
122 case 'w':
123 tmate_settings->websocket_hostname = xstrdup(optarg);
124 break;
125 case 'z':
126 tmate_settings->websocket_port = atoi(optarg);
127 break;
128 case 'x':
129 tmate_settings->use_proxy_protocol = true;
130 break;
131 case 'v':
132 tmate_settings->log_level++;
133 break;
134 default:
135 usage();
136 return 1;
137 }
138 }
139
140 init_logging(tmate_settings->log_level);
141
142 setup_locale();
143
144 if (!tmate_settings->tmate_host)
145 tmate_settings->tmate_host = get_full_hostname();
146
147 cmdline = *argv;
148 cmdline_end = *envp;
149
150 tmate_preload_trace_lib();
151 tmate_catch_sigsegv();
152 tmate_init_rand();
153
154 if ((mkdir(TMATE_WORKDIR, 0701) < 0 && errno != EEXIST) ||
155 (mkdir(TMATE_WORKDIR "/sessions", 0703) < 0 && errno != EEXIST) ||
156 (mkdir(TMATE_WORKDIR "/jail", 0700) < 0 && errno != EEXIST))
157 tmate_fatal("Cannot prepare session in " TMATE_WORKDIR);
158
159 /* The websocket server needs to access the /session dir to rename sockets */
160 if ((chmod(TMATE_WORKDIR, 0701) < 0) ||
161 (chmod(TMATE_WORKDIR "/sessions", 0703) < 0) ||
162 (chmod(TMATE_WORKDIR "/jail", 0700) < 0))
163 tmate_fatal("Cannot prepare session in " TMATE_WORKDIR);
164
165 tmate_ssh_server_main(tmate_session,
166 tmate_settings->keys_dir, tmate_settings->bind_addr, tmate_settings->ssh_port);
167 return 0;
168 }
169
get_socket_path(const char * _token)170 char *get_socket_path(const char *_token)
171 {
172 char *path;
173 char *token = xstrdup(_token);
174
175 for (char *c = token; *c; c++) {
176 if (*c == '/' || *c == '.')
177 *c = '=';
178 }
179
180 xasprintf(&path, TMATE_WORKDIR "/sessions/%s", token);
181 free(token);
182 return path;
183 }
184
set_session_token(struct tmate_session * session,const char * token)185 void set_session_token(struct tmate_session *session, const char *token)
186 {
187 session->session_token = xstrdup(token);
188 socket_path = get_socket_path(token);
189
190 xasprintf((char **)&session->obfuscated_session_token, "%.4s...",
191 session->session_token);
192
193 size_t size = cmdline_end - cmdline;
194 memset(cmdline, 0, size);
195 snprintf(cmdline, size-1, "tmate-ssh-server [%s] %s %s",
196 tmate_session->obfuscated_session_token,
197 session->ssh_client.role == TMATE_ROLE_DAEMON ? "(daemon)" : "(pty client)",
198 session->ssh_client.ip_address);
199
200 char *log_prefix;
201 xasprintf(&log_prefix, "[%s] ", session->obfuscated_session_token);
202 set_log_prefix(log_prefix);
203 free(log_prefix);
204 }
205
close_fds_except(int * fd_to_preserve,int num_fds)206 void close_fds_except(int *fd_to_preserve, int num_fds)
207 {
208 int fd, i, preserve;
209
210 for (fd = 0; fd < 1024; fd++) {
211 preserve = 0;
212 for (i = 0; i < num_fds; i++)
213 if (fd_to_preserve[i] == fd)
214 preserve = 1;
215
216 if (!preserve)
217 close(fd);
218 }
219 }
220
get_in_jail(void)221 void get_in_jail(void)
222 {
223 struct passwd *pw;
224 uid_t uid;
225 gid_t gid;
226
227 pw = getpwnam(TMATE_JAIL_USER);
228 if (!pw) {
229 tmate_fatal("Cannot get the /etc/passwd entry for %s",
230 TMATE_JAIL_USER);
231 }
232 uid = pw->pw_uid;
233 gid = pw->pw_gid;
234
235 if (getuid() != 0)
236 tmate_fatal("Need root privileges to create the jail");
237
238 if (chroot(TMATE_WORKDIR "/jail") < 0)
239 tmate_fatal("Cannot chroot()");
240
241 if (chdir("/") < 0)
242 tmate_fatal("Cannot chdir()");
243
244 #ifdef IS_LINUX
245 if (unshare(CLONE_NEWPID | CLONE_NEWIPC | CLONE_NEWNS | CLONE_NEWNET) < 0)
246 tmate_fatal("Cannot create new namespace");
247 #endif
248
249 if (setgroups(1, (gid_t[]){gid}) < 0)
250 tmate_fatal("Cannot setgroups()");
251
252 #if defined(HAVE_SETRESGID)
253 if (setresgid(gid, gid, gid) < 0)
254 tmate_fatal("Cannot setresgid() %d", gid);
255 #elif defined(HAVE_SETREGID)
256 if (setregid(gid, gid) < 0)
257 tmate_fatal("Cannot setregid()");
258 #else
259 if (setgid(gid) < 0)
260 tmate_fatal("Cannot setgid()");
261 #endif
262
263 #if defined(HAVE_SETRESUID)
264 if (setresuid(uid, uid, uid) < 0)
265 tmate_fatal("Cannot setresuid()");
266 #elif defined(HAVE_SETREUID)
267 if (setreuid(uid, uid) < 0)
268 tmate_fatal("Cannot setreuid()");
269 #else
270 if (setuid(uid) < 0)
271 tmate_fatal("Cannot setuid()");
272 #endif
273
274 nice(1);
275
276 tmate_debug("Dropped priviledges to %s (%d,%d), jailed in %s",
277 TMATE_JAIL_USER, uid, gid, TMATE_WORKDIR "/jail");
278 }
279
setup_ncurse(int fd,const char * name)280 void setup_ncurse(int fd, const char *name)
281 {
282 int error;
283 if (setupterm((char *)name, fd, &error) != OK)
284 tmate_fatal("Cannot setup terminal");
285 }
286
287