putty/unix/pty.c

785 строки
19 KiB
C

/*
* 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
#define _XOPEN_SOURCE_EXTENDED
#define _GNU_SOURCE
#include <features.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <signal.h>
#include <fcntl.h>
#include <termios.h>
#include <grp.h>
#include <utmp.h>
#include <pwd.h>
#include <time.h>
#include <sys/types.h>
#include <sys/wait.h>
#include <sys/ioctl.h>
#include <errno.h>
#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_stamped_utmp = 0;
static int pty_child_pid;
static int pty_utmp_helper_pid, pty_utmp_helper_pipe;
static int pty_term_width, pty_term_height;
static int pty_child_dead, pty_finished;
static int pty_exit_code;
#ifndef OMIT_UTMP
static struct utmp utmp_entry;
#endif
char **pty_argv;
int use_pty_argv = TRUE;
static void pty_close(void);
static void setup_utmp(char *ttyname, char *location)
{
#ifndef OMIT_UTMP
#ifdef HAVE_LASTLOG
struct lastlog lastlog_entry;
FILE *lastlog;
#endif
struct passwd *pw;
FILE *wtmp;
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));
time(&utmp_entry.ut_time);
#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;
#endif
}
static void cleanup_utmp(void)
{
#ifndef OMIT_UTMP
FILE *wtmp;
if (!pty_stamped_utmp)
return;
utmp_entry.ut_type = DEAD_PROCESS;
memset(utmp_entry.ut_user, 0, lenof(utmp_entry.ut_user));
time(&utmp_entry.ut_time);
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);
}
static void fatal_sig_handler(int signum)
{
putty_signal(signum, SIG_DFL);
cleanup_utmp();
setuid(getuid());
raise(signum);
}
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)
{
pid_t pid;
int pipefd[2];
/* 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. */
{
int gid = getgid(), uid = getuid();
#ifndef HAVE_NO_SETRESUID
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));
}
}
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 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);
}
/*
* 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;
}
}
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);
setpgrp();
close(open(pty_name, O_WRONLY, 0));
setpgrp();
/* 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);
}
/*
* SIGINT and SIGQUIT may have been set to ignored by our
* parent, particularly by things like sh -c 'pterm &' and
* some window managers. Reverse this for our child process.
*/
putty_signal(SIGINT, SIG_DFL);
putty_signal(SIGQUIT, SIG_DFL);
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;
}
if (pty_utmp_helper_pipe >= 0) {
close(pty_utmp_helper_pipe); /* this causes utmp to be cleaned up */
pty_utmp_helper_pipe = -1;
}
}
/*
* 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;
}
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,
1
};