/* * Pseudo-tty backend for pterm. * * Unlike the other backends, data for this one is not neatly * encapsulated into a data structure, because it wouldn't make * sense to do so - the utmp stuff has to be done before a backend * is initialised, and starting a second pterm from the same * process would therefore be infeasible because privileges would * already have been dropped. Hence, I haven't bothered to keep the * data dynamically allocated: instead, the backend handle is just * a null pointer and ignored everywhere. */ #define _XOPEN_SOURCE 600 #define _XOPEN_SOURCE_EXTENDED #define _GNU_SOURCE #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include "putty.h" #ifndef FALSE #define FALSE 0 #endif #ifndef TRUE #define TRUE 1 #endif #ifndef UTMP_FILE #define UTMP_FILE "/var/run/utmp" #endif #ifndef WTMP_FILE #define WTMP_FILE "/var/log/wtmp" #endif #ifndef LASTLOG_FILE #ifdef _PATH_LASTLOG #define LASTLOG_FILE _PATH_LASTLOG #else #define LASTLOG_FILE "/var/log/lastlog" #endif #endif /* * Set up a default for vaguely sane systems. The idea is that if * OMIT_UTMP is not defined, then at least one of the symbols which * enable particular forms of utmp processing should be, if only so * that a link error can warn you that you should have defined * OMIT_UTMP if you didn't want any. Currently HAVE_PUTUTLINE is * the only such symbol. */ #ifndef OMIT_UTMP #if !defined HAVE_PUTUTLINE #define HAVE_PUTUTLINE #endif #endif static Config pty_cfg; static int pty_master_fd; static void *pty_frontend; static char pty_name[FILENAME_MAX]; static int pty_signal_pipe[2]; static int pty_child_pid; static int pty_term_width, pty_term_height; static int pty_child_dead, pty_finished; static int pty_exit_code; char **pty_argv; int use_pty_argv = TRUE; static void pty_close(void); #ifndef OMIT_UTMP static int pty_utmp_helper_pid, pty_utmp_helper_pipe; static int pty_stamped_utmp = 0; static struct utmp utmp_entry; static void setup_utmp(char *ttyname, char *location) { #ifdef HAVE_LASTLOG struct lastlog lastlog_entry; FILE *lastlog; #endif struct passwd *pw; FILE *wtmp; time_t uttime; pw = getpwuid(getuid()); memset(&utmp_entry, 0, sizeof(utmp_entry)); utmp_entry.ut_type = USER_PROCESS; utmp_entry.ut_pid = getpid(); strncpy(utmp_entry.ut_line, ttyname+5, lenof(utmp_entry.ut_line)); strncpy(utmp_entry.ut_id, ttyname+8, lenof(utmp_entry.ut_id)); strncpy(utmp_entry.ut_user, pw->pw_name, lenof(utmp_entry.ut_user)); strncpy(utmp_entry.ut_host, location, lenof(utmp_entry.ut_host)); /* Apparently there are some architectures where (struct utmp).ut_time * is not essentially time_t (e.g. Linux amd64). Hence the temporary. */ time(&uttime); utmp_entry.ut_time = uttime; /* may truncate */ #if defined HAVE_PUTUTLINE utmpname(UTMP_FILE); setutent(); pututline(&utmp_entry); endutent(); #endif if ((wtmp = fopen(WTMP_FILE, "a")) != NULL) { fwrite(&utmp_entry, 1, sizeof(utmp_entry), wtmp); fclose(wtmp); } #ifdef HAVE_LASTLOG memset(&lastlog_entry, 0, sizeof(lastlog_entry)); strncpy(lastlog_entry.ll_line, ttyname+5, lenof(lastlog_entry.ll_line)); strncpy(lastlog_entry.ll_host, location, lenof(lastlog_entry.ll_host)); time(&lastlog_entry.ll_time); if ((lastlog = fopen(LASTLOG_FILE, "r+")) != NULL) { fseek(lastlog, sizeof(lastlog_entry) * getuid(), SEEK_SET); fwrite(&lastlog_entry, 1, sizeof(lastlog_entry), lastlog); fclose(lastlog); } #endif pty_stamped_utmp = 1; } static void cleanup_utmp(void) { FILE *wtmp; time_t uttime; if (!pty_stamped_utmp) return; utmp_entry.ut_type = DEAD_PROCESS; memset(utmp_entry.ut_user, 0, lenof(utmp_entry.ut_user)); time(&uttime); utmp_entry.ut_time = uttime; if ((wtmp = fopen(WTMP_FILE, "a")) != NULL) { fwrite(&utmp_entry, 1, sizeof(utmp_entry), wtmp); fclose(wtmp); } memset(utmp_entry.ut_line, 0, lenof(utmp_entry.ut_line)); utmp_entry.ut_time = 0; #if defined HAVE_PUTUTLINE utmpname(UTMP_FILE); setutent(); pututline(&utmp_entry); endutent(); #endif pty_stamped_utmp = 0; /* ensure we never double-cleanup */ } #endif static void sigchld_handler(int signum) { write(pty_signal_pipe[1], "x", 1); } #ifndef OMIT_UTMP static void fatal_sig_handler(int signum) { putty_signal(signum, SIG_DFL); cleanup_utmp(); setuid(getuid()); raise(signum); } #endif static void pty_open_master(void) { #ifdef BSD_PTYS const char chars1[] = "pqrstuvwxyz"; const char chars2[] = "0123456789abcdef"; const char *p1, *p2; char master_name[20]; struct group *gp; for (p1 = chars1; *p1; p1++) for (p2 = chars2; *p2; p2++) { sprintf(master_name, "/dev/pty%c%c", *p1, *p2); pty_master_fd = open(master_name, O_RDWR); if (pty_master_fd >= 0) { if (geteuid() == 0 || access(master_name, R_OK | W_OK) == 0) goto got_one; close(pty_master_fd); } } /* If we get here, we couldn't get a tty at all. */ fprintf(stderr, "pterm: unable to open a pseudo-terminal device\n"); exit(1); got_one: strcpy(pty_name, master_name); pty_name[5] = 't'; /* /dev/ptyXX -> /dev/ttyXX */ /* We need to chown/chmod the /dev/ttyXX device. */ gp = getgrnam("tty"); chown(pty_name, getuid(), gp ? gp->gr_gid : -1); chmod(pty_name, 0600); #else pty_master_fd = open("/dev/ptmx", O_RDWR); if (pty_master_fd < 0) { perror("/dev/ptmx: open"); exit(1); } if (grantpt(pty_master_fd) < 0) { perror("grantpt"); exit(1); } if (unlockpt(pty_master_fd) < 0) { perror("unlockpt"); exit(1); } pty_name[FILENAME_MAX-1] = '\0'; strncpy(pty_name, ptsname(pty_master_fd), FILENAME_MAX-1); #endif } /* * Pre-initialisation. This is here to get around the fact that GTK * doesn't like being run in setuid/setgid programs (probably * sensibly). So before we initialise GTK - and therefore before we * even process the command line - we check to see if we're running * set[ug]id. If so, we open our pty master _now_, chown it as * necessary, and drop privileges. We can always close it again * later. If we're potentially going to be doing utmp as well, we * also fork off a utmp helper process and communicate with it by * means of a pipe; the utmp helper will keep privileges in order * to clean up utmp when we exit (i.e. when its end of our pipe * closes). */ void pty_pre_init(void) { #ifndef OMIT_UTMP pid_t pid; int pipefd[2]; #endif /* set the child signal handler straight away; it needs to be set * before we ever fork. */ putty_signal(SIGCHLD, sigchld_handler); pty_master_fd = -1; if (geteuid() != getuid() || getegid() != getgid()) { pty_open_master(); } #ifndef OMIT_UTMP /* * Fork off the utmp helper. */ if (pipe(pipefd) < 0) { perror("pterm: pipe"); exit(1); } pid = fork(); if (pid < 0) { perror("pterm: fork"); exit(1); } else if (pid == 0) { char display[128], buffer[128]; int dlen, ret; close(pipefd[1]); /* * Now sit here until we receive a display name from the * other end of the pipe, and then stamp utmp. Unstamp utmp * again, and exit, when the pipe closes. */ dlen = 0; while (1) { ret = read(pipefd[0], buffer, lenof(buffer)); if (ret <= 0) { cleanup_utmp(); _exit(0); } else if (!pty_stamped_utmp) { if (dlen < lenof(display)) memcpy(display+dlen, buffer, min(ret, lenof(display)-dlen)); if (buffer[ret-1] == '\0') { /* * Now we have a display name. NUL-terminate * it, and stamp utmp. */ display[lenof(display)-1] = '\0'; /* * Trap as many fatal signals as we can in the * hope of having the best possible chance to * clean up utmp before termination. We are * unfortunately unprotected against SIGKILL, * but that's life. */ putty_signal(SIGHUP, fatal_sig_handler); putty_signal(SIGINT, fatal_sig_handler); putty_signal(SIGQUIT, fatal_sig_handler); putty_signal(SIGILL, fatal_sig_handler); putty_signal(SIGABRT, fatal_sig_handler); putty_signal(SIGFPE, fatal_sig_handler); putty_signal(SIGPIPE, fatal_sig_handler); putty_signal(SIGALRM, fatal_sig_handler); putty_signal(SIGTERM, fatal_sig_handler); putty_signal(SIGSEGV, fatal_sig_handler); putty_signal(SIGUSR1, fatal_sig_handler); putty_signal(SIGUSR2, fatal_sig_handler); #ifdef SIGBUS putty_signal(SIGBUS, fatal_sig_handler); #endif #ifdef SIGPOLL putty_signal(SIGPOLL, fatal_sig_handler); #endif #ifdef SIGPROF putty_signal(SIGPROF, fatal_sig_handler); #endif #ifdef SIGSYS putty_signal(SIGSYS, fatal_sig_handler); #endif #ifdef SIGTRAP putty_signal(SIGTRAP, fatal_sig_handler); #endif #ifdef SIGVTALRM putty_signal(SIGVTALRM, fatal_sig_handler); #endif #ifdef SIGXCPU putty_signal(SIGXCPU, fatal_sig_handler); #endif #ifdef SIGXFSZ putty_signal(SIGXFSZ, fatal_sig_handler); #endif #ifdef SIGIO putty_signal(SIGIO, fatal_sig_handler); #endif setup_utmp(pty_name, display); } } } } else { close(pipefd[0]); pty_utmp_helper_pid = pid; pty_utmp_helper_pipe = pipefd[1]; } #endif /* Drop privs. */ { #ifndef HAVE_NO_SETRESUID int gid = getgid(), uid = getuid(); int setresgid(gid_t, gid_t, gid_t); int setresuid(uid_t, uid_t, uid_t); setresgid(gid, gid, gid); setresuid(uid, uid, uid); #else setgid(getgid()); setuid(getuid()); #endif } } int pty_select_result(int fd, int event) { char buf[4096]; int ret; int finished = FALSE; if (fd == pty_master_fd && event == 1) { ret = read(pty_master_fd, buf, sizeof(buf)); /* * Clean termination condition is that either ret == 0, or ret * < 0 and errno == EIO. Not sure why the latter, but it seems * to happen. Boo. */ if (ret == 0 || (ret < 0 && errno == EIO)) { /* * We assume a clean exit if the pty has closed but the * actual child process hasn't. The only way I can * imagine this happening is if it detaches itself from * the pty and goes daemonic - in which case the * expected usage model would precisely _not_ be for * the pterm window to hang around! */ finished = TRUE; if (!pty_child_dead) pty_exit_code = 0; } else if (ret < 0) { perror("read pty master"); exit(1); } else if (ret > 0) { from_backend(pty_frontend, 0, buf, ret); } } else if (fd == pty_signal_pipe[0]) { pid_t pid; int status; char c[1]; read(pty_signal_pipe[0], c, 1); /* ignore its value; it'll be `x' */ do { pid = waitpid(-1, &status, WNOHANG); if (pid == pty_child_pid && (WIFEXITED(status) || WIFSIGNALED(status))) { /* * The primary child process died. We could keep * the terminal open for remaining subprocesses to * output to, but conventional wisdom seems to feel * that that's the Wrong Thing for an xterm-alike, * so we bail out now (though we don't necessarily * _close_ the window, depending on the state of * Close On Exit). This would be easy enough to * change or make configurable if necessary. */ pty_exit_code = status; pty_child_dead = TRUE; finished = TRUE; } } while(pid > 0); } if (finished && !pty_finished) { uxsel_del(pty_master_fd); pty_close(); pty_master_fd = -1; pty_finished = TRUE; /* * This is a slight layering-violation sort of hack: only * if we're not closing on exit (COE is set to Never, or to * Only On Clean and it wasn't a clean exit) do we output a * `terminated' message. */ if (pty_cfg.close_on_exit == FORCE_OFF || (pty_cfg.close_on_exit == AUTO && pty_exit_code != 0)) { char message[512]; if (WIFEXITED(pty_exit_code)) sprintf(message, "\r\n[pterm: process terminated with exit" " code %d]\r\n", WEXITSTATUS(pty_exit_code)); else if (WIFSIGNALED(pty_exit_code)) #ifdef HAVE_NO_STRSIGNAL sprintf(message, "\r\n[pterm: process terminated on signal" " %d]\r\n", WTERMSIG(pty_exit_code)); #else sprintf(message, "\r\n[pterm: process terminated on signal" " %d (%.400s)]\r\n", WTERMSIG(pty_exit_code), strsignal(WTERMSIG(pty_exit_code))); #endif from_backend(pty_frontend, 0, message, strlen(message)); } notify_remote_exit(pty_frontend); } return !finished; } static void pty_uxsel_setup(void) { uxsel_set(pty_master_fd, 1, pty_select_result); uxsel_set(pty_signal_pipe[0], 1, pty_select_result); } /* * Called to set up the pty. * * Returns an error message, or NULL on success. * * Also places the canonical host name into `realhost'. It must be * freed by the caller. */ static const char *pty_init(void *frontend, void **backend_handle, Config *cfg, char *host, int port, char **realhost, int nodelay, int keepalive) { int slavefd; pid_t pid, pgrp; long windowid; pty_frontend = frontend; *backend_handle = NULL; /* we can't sensibly use this, sadly */ pty_cfg = *cfg; /* structure copy */ pty_term_width = cfg->width; pty_term_height = cfg->height; if (pty_master_fd < 0) pty_open_master(); /* * Set the backspace character to be whichever of ^H and ^? is * specified by bksp_is_delete. */ { struct termios attrs; tcgetattr(pty_master_fd, &attrs); attrs.c_cc[VERASE] = cfg->bksp_is_delete ? '\177' : '\010'; tcsetattr(pty_master_fd, TCSANOW, &attrs); } #ifndef OMIT_UTMP /* * Stamp utmp (that is, tell the utmp helper process to do so), * or not. */ if (!cfg->stamp_utmp) { close(pty_utmp_helper_pipe); /* just let the child process die */ pty_utmp_helper_pipe = -1; } else { char *location = get_x_display(pty_frontend); int len = strlen(location)+1, pos = 0; /* +1 to include NUL */ while (pos < len) { int ret = write(pty_utmp_helper_pipe, location+pos, len - pos); if (ret < 0) { perror("pterm: writing to utmp helper process"); close(pty_utmp_helper_pipe); /* arrgh, just give up */ pty_utmp_helper_pipe = -1; break; } pos += ret; } } #endif windowid = get_windowid(pty_frontend); /* * Fork and execute the command. */ pid = fork(); if (pid < 0) { perror("fork"); exit(1); } if (pid == 0) { int i; /* * We are the child. */ slavefd = open(pty_name, O_RDWR); if (slavefd < 0) { perror("slave pty: open"); _exit(1); } close(pty_master_fd); fcntl(slavefd, F_SETFD, 0); /* don't close on exec */ dup2(slavefd, 0); dup2(slavefd, 1); dup2(slavefd, 2); setsid(); ioctl(slavefd, TIOCSCTTY, 1); pgrp = getpid(); tcsetpgrp(slavefd, pgrp); setpgid(pgrp, pgrp); close(open(pty_name, O_WRONLY, 0)); setpgid(pgrp, pgrp); /* Close everything _else_, for tidiness. */ for (i = 3; i < 1024; i++) close(i); { char term_env_var[10 + sizeof(cfg->termtype)]; sprintf(term_env_var, "TERM=%s", cfg->termtype); putenv(term_env_var); } { char windowid_env_var[40]; sprintf(windowid_env_var, "WINDOWID=%ld", windowid); putenv(windowid_env_var); } { char *e = cfg->environmt; char *var, *varend, *val, *varval; while (*e) { var = e; while (*e && *e != '\t') e++; varend = e; if (*e == '\t') e++; val = e; while (*e) e++; e++; varval = dupprintf("%.*s=%s", varend-var, var, val); putenv(varval); /* * We must not free varval, since putenv links it * into the environment _in place_. Weird, but * there we go. Memory usage will be rationalised * as soon as we exec anyway. */ } } /* * SIGINT and SIGQUIT may have been set to ignored by our * parent, particularly by things like sh -c 'pterm &' and * some window managers. SIGCHLD, meanwhile, was blocked * during pt_main() startup. Reverse all this for our child * process. */ putty_signal(SIGINT, SIG_DFL); putty_signal(SIGQUIT, SIG_DFL); block_signal(SIGCHLD, 0); if (pty_argv) execvp(pty_argv[0], pty_argv); else { char *shell = getenv("SHELL"); char *shellname; if (cfg->login_shell) { char *p = strrchr(shell, '/'); shellname = snewn(2+strlen(shell), char); p = p ? p+1 : shell; sprintf(shellname, "-%s", p); } else shellname = shell; execl(getenv("SHELL"), shellname, NULL); } /* * If we're here, exec has gone badly foom. */ perror("exec"); _exit(127); } else { pty_child_pid = pid; pty_child_dead = FALSE; pty_finished = FALSE; } if (pipe(pty_signal_pipe) < 0) { perror("pipe"); exit(1); } pty_uxsel_setup(); return NULL; } static void pty_reconfig(void *handle, Config *cfg) { /* * We don't have much need to reconfigure this backend, but * unfortunately we do need to pick up the setting of Close On * Exit so we know whether to give a `terminated' message. */ pty_cfg = *cfg; /* structure copy */ } /* * Stub routine (never called in pterm). */ static void pty_free(void *handle) { } /* * Called to send data down the pty. */ static int pty_send(void *handle, char *buf, int len) { if (pty_master_fd < 0) return 0; /* ignore all writes if fd closed */ while (len > 0) { int ret = write(pty_master_fd, buf, len); if (ret < 0) { perror("write pty master"); exit(1); } buf += ret; len -= ret; } return 0; } static void pty_close(void) { if (pty_master_fd >= 0) { close(pty_master_fd); pty_master_fd = -1; } #ifndef OMIT_UTMP if (pty_utmp_helper_pipe >= 0) { close(pty_utmp_helper_pipe); /* this causes utmp to be cleaned up */ pty_utmp_helper_pipe = -1; } #endif } /* * Called to query the current socket sendability status. */ static int pty_sendbuffer(void *handle) { return 0; } /* * Called to set the size of the window */ static void pty_size(void *handle, int width, int height) { struct winsize size; pty_term_width = width; pty_term_height = height; size.ws_row = (unsigned short)pty_term_height; size.ws_col = (unsigned short)pty_term_width; size.ws_xpixel = (unsigned short) pty_term_width * font_dimension(pty_frontend, 0); size.ws_ypixel = (unsigned short) pty_term_height * font_dimension(pty_frontend, 1); ioctl(pty_master_fd, TIOCSWINSZ, (void *)&size); return; } /* * Send special codes. */ static void pty_special(void *handle, Telnet_Special code) { /* Do nothing! */ return; } /* * Return a list of the special codes that make sense in this * protocol. */ static const struct telnet_special *pty_get_specials(void *handle) { /* * Hmm. When I get round to having this actually usable, it * might be quite nice to have the ability to deliver a few * well chosen signals to the child process - SIGINT, SIGTERM, * SIGKILL at least. */ return NULL; } static Socket pty_socket(void *handle) { return NULL; /* shouldn't ever be needed */ } static int pty_sendok(void *handle) { return 1; } static void pty_unthrottle(void *handle, int backlog) { /* do nothing */ } static int pty_ldisc(void *handle, int option) { return 0; /* neither editing nor echoing */ } static void pty_provide_ldisc(void *handle, void *ldisc) { /* This is a stub. */ } static void pty_provide_logctx(void *handle, void *logctx) { /* This is a stub. */ } static int pty_exitcode(void *handle) { if (!pty_finished) return -1; /* not dead yet */ else return pty_exit_code; } static int pty_cfg_info(void *handle) { return 0; } Backend pty_backend = { pty_init, pty_free, pty_reconfig, pty_send, pty_sendbuffer, pty_size, pty_special, pty_get_specials, pty_socket, pty_exitcode, pty_sendok, pty_ldisc, pty_provide_ldisc, pty_provide_logctx, pty_unthrottle, pty_cfg_info, 1 };