/* * Copyright (c) 2009-2011 Todd C. Miller * * Permission to use, copy, modify, and distribute this software for any * purpose with or without fee is hereby granted, provided that the above * copyright notice and this permission notice appear in all copies. * * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE. */ #include #include #include #ifdef HAVE_SYS_SYSMACROS_H # include #endif #include #include #include #include #ifdef HAVE_SYS_SELECT_H # include #endif /* HAVE_SYS_SELECT_H */ #include #ifdef STDC_HEADERS # include # include #else # ifdef HAVE_STDLIB_H # include # endif #endif /* STDC_HEADERS */ #ifdef HAVE_STRING_H # if defined(HAVE_MEMORY_H) && !defined(STDC_HEADERS) # include # endif # include #endif /* HAVE_STRING_H */ #ifdef HAVE_STRINGS_H # include #endif /* HAVE_STRINGS_H */ #ifdef HAVE_UNISTD_H # include #endif /* HAVE_UNISTD_H */ #if TIME_WITH_SYS_TIME # include #endif #include #include #include #include #include "sudo.h" #include "sudo_exec.h" #include "sudo_plugin.h" #include "sudo_plugin_int.h" #define SFD_STDIN 0 #define SFD_STDOUT 1 #define SFD_STDERR 2 #define SFD_MASTER 3 #define SFD_SLAVE 4 #define SFD_USERTTY 5 #define TERM_COOKED 0 #define TERM_RAW 1 /* Compatibility with older tty systems. */ #if !defined(TIOCGWINSZ) && defined(TIOCGSIZE) # define TIOCGWINSZ TIOCGSIZE # define TIOCSWINSZ TIOCSSIZE # define winsize ttysize #endif struct io_buffer { struct io_buffer *next; int len; /* buffer length (how much produced) */ int off; /* write position (how much already consumed) */ int rfd; /* reader (producer) */ int wfd; /* writer (consumer) */ bool (*action)(const char *buf, unsigned int len); char buf[16 * 1024]; }; static char slavename[PATH_MAX]; static bool foreground, pipeline, tty_initialized; static int io_fds[6] = { -1, -1, -1, -1, -1, -1}; static int ttymode = TERM_COOKED; static pid_t ppgrp, cmnd_pgrp; static sigset_t ttyblock; static struct io_buffer *iobufs; static void flush_output(void); static int exec_monitor(struct command_details *details, int backchannel); static void exec_pty(struct command_details *detail, int *errfd); static void sigwinch(int s); static void sync_ttysize(int src, int dst); static void deliver_signal(pid_t pid, int signo, bool from_parent); static int safe_close(int fd); static void check_foreground(void); /* * Cleanup hook for error()/errorx() */ void cleanup(int gotsignal) { debug_decl(cleanup, SUDO_DEBUG_EXEC); if (!tq_empty(&io_plugins) && io_fds[SFD_USERTTY] != -1) { check_foreground(); if (foreground) term_restore(io_fds[SFD_USERTTY], 0); } #ifdef HAVE_SELINUX selinux_restore_tty(); #endif utmp_logout(slavename, 0); /* XXX - only if CD_SET_UTMP */ debug_return; } /* * Generic handler for signals recieved by the monitor process. * The other end of signal_pipe is checked in the monitor event loop. */ #ifdef SA_SIGINFO void mon_handler(int s, siginfo_t *info, void *context) { unsigned char signo = (unsigned char)s; /* * If the signal came from the command we ran, just ignore * it since we don't want the command to indirectly kill itself. * This can happen with, e.g. BSD-derived versions of reboot * that call kill(-1, SIGTERM) to kill all other processes. */ if (info != NULL && info->si_code == SI_USER && info->si_pid == cmnd_pid) return; /* * The pipe is non-blocking, if we overflow the kernel's pipe * buffer we drop the signal. This is not a problem in practice. */ ignore_result(write(signal_pipe[1], &signo, sizeof(signo))); } #else void mon_handler(int s) { unsigned char signo = (unsigned char)s; /* * The pipe is non-blocking, if we overflow the kernel's pipe * buffer we drop the signal. This is not a problem in practice. */ ignore_result(write(signal_pipe[1], &signo, sizeof(signo))); } #endif /* * Allocate a pty if /dev/tty is a tty. * Fills in io_fds[SFD_USERTTY], io_fds[SFD_MASTER], io_fds[SFD_SLAVE] * and slavename globals. */ void pty_setup(uid_t uid, const char *tty, const char *utmp_user) { debug_decl(pty_setup, SUDO_DEBUG_EXEC); io_fds[SFD_USERTTY] = open(_PATH_TTY, O_RDWR|O_NOCTTY, 0); if (io_fds[SFD_USERTTY] != -1) { if (!get_pty(&io_fds[SFD_MASTER], &io_fds[SFD_SLAVE], slavename, sizeof(slavename), uid)) error(1, _("unable to allocate pty")); /* Add entry to utmp/utmpx? */ if (utmp_user != NULL) utmp_login(tty, slavename, io_fds[SFD_SLAVE], utmp_user); } debug_return; } /* Call I/O plugin tty input log method. */ static bool log_ttyin(const char *buf, unsigned int n) { struct plugin_container *plugin; sigset_t omask; bool rval = true; debug_decl(log_ttyin, SUDO_DEBUG_EXEC); sigprocmask(SIG_BLOCK, &ttyblock, &omask); tq_foreach_fwd(&io_plugins, plugin) { if (plugin->u.io->log_ttyin) { if (!plugin->u.io->log_ttyin(buf, n)) { rval = false; break; } } } sigprocmask(SIG_SETMASK, &omask, NULL); debug_return_bool(rval); } /* Call I/O plugin stdin log method. */ static bool log_stdin(const char *buf, unsigned int n) { struct plugin_container *plugin; sigset_t omask; bool rval = true; debug_decl(log_stdin, SUDO_DEBUG_EXEC); sigprocmask(SIG_BLOCK, &ttyblock, &omask); tq_foreach_fwd(&io_plugins, plugin) { if (plugin->u.io->log_stdin) { if (!plugin->u.io->log_stdin(buf, n)) { rval = false; break; } } } sigprocmask(SIG_SETMASK, &omask, NULL); debug_return_bool(rval); } /* Call I/O plugin tty output log method. */ static bool log_ttyout(const char *buf, unsigned int n) { struct plugin_container *plugin; sigset_t omask; bool rval = true; debug_decl(log_ttyout, SUDO_DEBUG_EXEC); sigprocmask(SIG_BLOCK, &ttyblock, &omask); tq_foreach_fwd(&io_plugins, plugin) { if (plugin->u.io->log_ttyout) { if (!plugin->u.io->log_ttyout(buf, n)) { rval = false; break; } } } sigprocmask(SIG_SETMASK, &omask, NULL); debug_return_bool(rval); } /* Call I/O plugin stdout log method. */ static bool log_stdout(const char *buf, unsigned int n) { struct plugin_container *plugin; sigset_t omask; bool rval = true; debug_decl(log_stdout, SUDO_DEBUG_EXEC); sigprocmask(SIG_BLOCK, &ttyblock, &omask); tq_foreach_fwd(&io_plugins, plugin) { if (plugin->u.io->log_stdout) { if (!plugin->u.io->log_stdout(buf, n)) { rval = false; break; } } } sigprocmask(SIG_SETMASK, &omask, NULL); debug_return_bool(rval); } /* Call I/O plugin stderr log method. */ static bool log_stderr(const char *buf, unsigned int n) { struct plugin_container *plugin; sigset_t omask; bool rval = true; debug_decl(log_stderr, SUDO_DEBUG_EXEC); sigprocmask(SIG_BLOCK, &ttyblock, &omask); tq_foreach_fwd(&io_plugins, plugin) { if (plugin->u.io->log_stderr) { if (!plugin->u.io->log_stderr(buf, n)) { rval = false; break; } } } sigprocmask(SIG_SETMASK, &omask, NULL); debug_return_bool(rval); } /* * Check whether we are running in the foregroup. * Updates the foreground global and does lazy init of the * the pty slave as needed. */ static void check_foreground(void) { debug_decl(check_foreground, SUDO_DEBUG_EXEC); if (io_fds[SFD_USERTTY] != -1) { foreground = tcgetpgrp(io_fds[SFD_USERTTY]) == ppgrp; if (foreground && !tty_initialized) { if (term_copy(io_fds[SFD_USERTTY], io_fds[SFD_SLAVE])) { tty_initialized = true; sync_ttysize(io_fds[SFD_USERTTY], io_fds[SFD_SLAVE]); } } } debug_return; } /* * Suspend sudo if the underlying command is suspended. * Returns SIGCONT_FG if the command should be resumed in the * foreground or SIGCONT_BG if it is a background process. */ int suspend_parent(int signo) { char signame[SIG2STR_MAX]; sigaction_t sa, osa; int n, oldmode = ttymode, rval = 0; debug_decl(suspend_parent, SUDO_DEBUG_EXEC); switch (signo) { case SIGTTOU: case SIGTTIN: /* * If we are the foreground process, just resume the command. * Otherwise, re-send the signal with the handler disabled. */ if (!foreground) check_foreground(); if (foreground) { if (ttymode != TERM_RAW) { do { n = term_raw(io_fds[SFD_USERTTY], 0); } while (!n && errno == EINTR); ttymode = TERM_RAW; } rval = SIGCONT_FG; /* resume command in foreground */ break; } ttymode = TERM_RAW; /* FALLTHROUGH */ case SIGSTOP: case SIGTSTP: /* Flush any remaining output before suspending. */ flush_output(); /* Restore original tty mode before suspending. */ if (oldmode != TERM_COOKED) { do { n = term_restore(io_fds[SFD_USERTTY], 0); } while (!n && errno == EINTR); } if (sig2str(signo, signame) == -1) snprintf(signame, sizeof(signame), "%d", signo); /* Suspend self and continue command when we resume. */ zero_bytes(&sa, sizeof(sa)); sigemptyset(&sa.sa_mask); sa.sa_flags = SA_INTERRUPT; /* do not restart syscalls */ sa.sa_handler = SIG_DFL; sigaction(signo, &sa, &osa); sudo_debug_printf(SUDO_DEBUG_INFO, "kill parent SIG%s", signame); if (killpg(ppgrp, signo) != 0) warning("killpg(%d, SIG%s)", (int)ppgrp, signame); /* Check foreground/background status on resume. */ check_foreground(); /* * Only modify term if we are foreground process and either * the old tty mode was not cooked or command got SIGTT{IN,OU} */ sudo_debug_printf(SUDO_DEBUG_INFO, "parent is in %s, ttymode %d -> %d", foreground ? "foreground" : "background", oldmode, ttymode); if (ttymode != TERM_COOKED) { if (foreground) { /* Set raw mode. */ do { n = term_raw(io_fds[SFD_USERTTY], 0); } while (!n && errno == EINTR); } else { /* Background process, no access to tty. */ ttymode = TERM_COOKED; } } sigaction(signo, &osa, NULL); rval = ttymode == TERM_RAW ? SIGCONT_FG : SIGCONT_BG; break; } debug_return_int(rval); } /* * Kill command with increasing urgency. */ void terminate_command(pid_t pid, bool use_pgrp) { debug_decl(terminate_command, SUDO_DEBUG_EXEC); /* * Note that SIGCHLD will interrupt the sleep() */ if (use_pgrp) { sudo_debug_printf(SUDO_DEBUG_INFO, "killpg %d SIGHUP", (int)pid); killpg(pid, SIGHUP); sudo_debug_printf(SUDO_DEBUG_INFO, "killpg %d SIGTERM", (int)pid); killpg(pid, SIGTERM); sleep(2); sudo_debug_printf(SUDO_DEBUG_INFO, "killpg %d SIGKILL", (int)pid); killpg(pid, SIGKILL); } else { sudo_debug_printf(SUDO_DEBUG_INFO, "kill %d SIGHUP", (int)pid); kill(pid, SIGHUP); sudo_debug_printf(SUDO_DEBUG_INFO, "kill %d SIGTERM", (int)pid); kill(pid, SIGTERM); sleep(2); sudo_debug_printf(SUDO_DEBUG_INFO, "kill %d SIGKILL", (int)pid); kill(pid, SIGKILL); } debug_return; } static struct io_buffer * io_buf_new(int rfd, int wfd, bool (*action)(const char *, unsigned int), struct io_buffer *head) { struct io_buffer *iob; debug_decl(io_buf_new, SUDO_DEBUG_EXEC); iob = ecalloc(1, sizeof(*iob)); iob->rfd = rfd; iob->wfd = wfd; iob->action = action; iob->next = head; debug_return_ptr(iob); } /* * Read/write iobufs depending on fdsr and fdsw. * Returns the number of errors. */ int perform_io(fd_set *fdsr, fd_set *fdsw, struct command_status *cstat) { struct io_buffer *iob; int n, errors = 0; debug_decl(perform_io, SUDO_DEBUG_EXEC); for (iob = iobufs; iob; iob = iob->next) { if (iob->rfd != -1 && FD_ISSET(iob->rfd, fdsr)) { do { n = read(iob->rfd, iob->buf + iob->len, sizeof(iob->buf) - iob->len); } while (n == -1 && errno == EINTR); switch (n) { case -1: if (errno != EAGAIN) { /* treat read error as fatal and close the fd */ sudo_debug_printf(SUDO_DEBUG_ERROR, "error reading fd %d: %s", iob->rfd, strerror(errno)); safe_close(iob->rfd); iob->rfd = -1; } break; case 0: /* got EOF or pty has gone away */ sudo_debug_printf(SUDO_DEBUG_INFO, "read EOF from fd %d", iob->rfd); safe_close(iob->rfd); iob->rfd = -1; break; default: sudo_debug_printf(SUDO_DEBUG_INFO, "read %d bytes from fd %d", n, iob->rfd); if (!iob->action(iob->buf + iob->len, n)) terminate_command(cmnd_pid, true); iob->len += n; break; } } if (iob->wfd != -1 && FD_ISSET(iob->wfd, fdsw)) { do { n = write(iob->wfd, iob->buf + iob->off, iob->len - iob->off); } while (n == -1 && errno == EINTR); if (n == -1) { if (errno == EPIPE || errno == ENXIO || errno == EIO || errno == EBADF) { sudo_debug_printf(SUDO_DEBUG_INFO, "unable to write %d bytes to fd %d", iob->len - iob->off, iob->wfd); /* other end of pipe closed or pty revoked */ if (iob->rfd != -1) { safe_close(iob->rfd); iob->rfd = -1; } safe_close(iob->wfd); iob->wfd = -1; continue; } if (errno != EAGAIN) { errors++; sudo_debug_printf(SUDO_DEBUG_ERROR, "error writing fd %d: %s", iob->wfd, strerror(errno)); } } else { sudo_debug_printf(SUDO_DEBUG_INFO, "wrote %d bytes to fd %d", n, iob->wfd); iob->off += n; } } } if (errors && cstat != NULL) { cstat->type = CMD_ERRNO; cstat->val = errno; } debug_return_int(errors); } /* * Fork a monitor process which runs the actual command as its own child * process with std{in,out,err} hooked up to the pty or pipes as appropriate. * Returns the child pid. */ int fork_pty(struct command_details *details, int sv[], int *maxfd, sigset_t *omask) { struct command_status cstat; struct io_buffer *iob; int io_pipe[3][2], n; sigaction_t sa; sigset_t mask; pid_t child; debug_decl(fork_pty, SUDO_DEBUG_EXEC); ppgrp = getpgrp(); /* parent's pgrp, so child can signal us */ zero_bytes(&sa, sizeof(sa)); sigemptyset(&sa.sa_mask); if (io_fds[SFD_USERTTY] != -1) { sa.sa_flags = SA_RESTART; sa.sa_handler = sigwinch; sigaction(SIGWINCH, &sa, NULL); } /* So we can block tty-generated signals */ sigemptyset(&ttyblock); sigaddset(&ttyblock, SIGINT); sigaddset(&ttyblock, SIGQUIT); sigaddset(&ttyblock, SIGTSTP); sigaddset(&ttyblock, SIGTTIN); sigaddset(&ttyblock, SIGTTOU); /* * Setup stdin/stdout/stderr for child, to be duped after forking. * In background mode there is no stdin. */ if (!ISSET(details->flags, CD_BACKGROUND)) io_fds[SFD_STDIN] = io_fds[SFD_SLAVE]; io_fds[SFD_STDOUT] = io_fds[SFD_SLAVE]; io_fds[SFD_STDERR] = io_fds[SFD_SLAVE]; if (io_fds[SFD_USERTTY] != -1) { /* Read from /dev/tty, write to pty master */ if (!ISSET(details->flags, CD_BACKGROUND)) { iobufs = io_buf_new(io_fds[SFD_USERTTY], io_fds[SFD_MASTER], log_ttyin, iobufs); } /* Read from pty master, write to /dev/tty */ iobufs = io_buf_new(io_fds[SFD_MASTER], io_fds[SFD_USERTTY], log_ttyout, iobufs); /* Are we the foreground process? */ foreground = tcgetpgrp(io_fds[SFD_USERTTY]) == ppgrp; } /* * If either stdin, stdout or stderr is not a tty we use a pipe * to interpose ourselves instead of duping the pty fd. */ memset(io_pipe, 0, sizeof(io_pipe)); if (io_fds[SFD_STDIN] == -1 || !isatty(STDIN_FILENO)) { sudo_debug_printf(SUDO_DEBUG_INFO, "stdin not a tty, creating a pipe"); pipeline = true; if (pipe(io_pipe[STDIN_FILENO]) != 0) error(1, _("unable to create pipe")); iobufs = io_buf_new(STDIN_FILENO, io_pipe[STDIN_FILENO][1], log_stdin, iobufs); io_fds[SFD_STDIN] = io_pipe[STDIN_FILENO][0]; } if (io_fds[SFD_STDOUT] == -1 || !isatty(STDOUT_FILENO)) { sudo_debug_printf(SUDO_DEBUG_INFO, "stdout not a tty, creating a pipe"); pipeline = true; if (pipe(io_pipe[STDOUT_FILENO]) != 0) error(1, _("unable to create pipe")); iobufs = io_buf_new(io_pipe[STDOUT_FILENO][0], STDOUT_FILENO, log_stdout, iobufs); io_fds[SFD_STDOUT] = io_pipe[STDOUT_FILENO][1]; } if (io_fds[SFD_STDERR] == -1 || !isatty(STDERR_FILENO)) { sudo_debug_printf(SUDO_DEBUG_INFO, "stderr not a tty, creating a pipe"); if (pipe(io_pipe[STDERR_FILENO]) != 0) error(1, _("unable to create pipe")); iobufs = io_buf_new(io_pipe[STDERR_FILENO][0], STDERR_FILENO, log_stderr, iobufs); io_fds[SFD_STDERR] = io_pipe[STDERR_FILENO][1]; } /* Job control signals to relay from parent to child. */ sa.sa_flags = SA_INTERRUPT; /* do not restart syscalls */ #ifdef SA_SIGINFO sa.sa_flags |= SA_SIGINFO; sa.sa_sigaction = handler; #else sa.sa_handler = handler; #endif sigaction(SIGTSTP, &sa, NULL); /* We don't want to receive SIGTTIN/SIGTTOU, getting EIO is preferable. */ sa.sa_handler = SIG_IGN; sigaction(SIGTTIN, &sa, NULL); sigaction(SIGTTOU, &sa, NULL); if (foreground) { /* Copy terminal attrs from user tty -> pty slave. */ if (term_copy(io_fds[SFD_USERTTY], io_fds[SFD_SLAVE])) { tty_initialized = true; sync_ttysize(io_fds[SFD_USERTTY], io_fds[SFD_SLAVE]); } /* Start out in raw mode if we are not part of a pipeline. */ if (!pipeline) { ttymode = TERM_RAW; do { n = term_raw(io_fds[SFD_USERTTY], 0); } while (!n && errno == EINTR); if (!n) error(1, _("unable to set terminal to raw mode")); } } /* * The policy plugin's session init must be run before we fork * or certain pam modules won't be able to track their state. */ if (policy_init_session(details) != true) errorx(1, _("policy plugin failed session initialization")); /* * Block some signals until cmnd_pid is set in the parent to avoid a * race between exec of the command and receipt of a fatal signal from it. */ sigemptyset(&mask); sigaddset(&mask, SIGTERM); sigaddset(&mask, SIGHUP); sigaddset(&mask, SIGINT); sigaddset(&mask, SIGQUIT); sigprocmask(SIG_BLOCK, &mask, omask); child = sudo_debug_fork(); switch (child) { case -1: error(1, _("unable to fork")); break; case 0: /* child */ close(sv[0]); close(signal_pipe[0]); close(signal_pipe[1]); fcntl(sv[1], F_SETFD, FD_CLOEXEC); sigprocmask(SIG_SETMASK, omask, NULL); if (exec_setup(details, slavename, io_fds[SFD_SLAVE]) == true) { /* Close the other end of the stdin/stdout/stderr pipes and exec. */ if (io_pipe[STDIN_FILENO][1]) close(io_pipe[STDIN_FILENO][1]); if (io_pipe[STDOUT_FILENO][0]) close(io_pipe[STDOUT_FILENO][0]); if (io_pipe[STDERR_FILENO][0]) close(io_pipe[STDERR_FILENO][0]); exec_monitor(details, sv[1]); } cstat.type = CMD_ERRNO; cstat.val = errno; ignore_result(send(sv[1], &cstat, sizeof(cstat), 0)); _exit(1); } /* Close the other end of the stdin/stdout/stderr pipes. */ if (io_pipe[STDIN_FILENO][0]) close(io_pipe[STDIN_FILENO][0]); if (io_pipe[STDOUT_FILENO][1]) close(io_pipe[STDOUT_FILENO][1]); if (io_pipe[STDERR_FILENO][1]) close(io_pipe[STDERR_FILENO][1]); for (iob = iobufs; iob; iob = iob->next) { /* Determine maxfd */ if (iob->rfd > *maxfd) *maxfd = iob->rfd; if (iob->wfd > *maxfd) *maxfd = iob->wfd; /* Set non-blocking mode. */ n = fcntl(iob->rfd, F_GETFL, 0); if (n != -1 && !ISSET(n, O_NONBLOCK)) (void) fcntl(iob->rfd, F_SETFL, n | O_NONBLOCK); n = fcntl(iob->wfd, F_GETFL, 0); if (n != -1 && !ISSET(n, O_NONBLOCK)) (void) fcntl(iob->wfd, F_SETFL, n | O_NONBLOCK); } debug_return_int(child); } void pty_close(struct command_status *cstat) { int n; debug_decl(pty_close, SUDO_DEBUG_EXEC); /* Flush any remaining output (the plugin already got it) */ if (io_fds[SFD_USERTTY] != -1) { n = fcntl(io_fds[SFD_USERTTY], F_GETFL, 0); if (n != -1 && ISSET(n, O_NONBLOCK)) { CLR(n, O_NONBLOCK); (void) fcntl(io_fds[SFD_USERTTY], F_SETFL, n); } } flush_output(); if (io_fds[SFD_USERTTY] != -1) { check_foreground(); if (foreground) { do { n = term_restore(io_fds[SFD_USERTTY], 0); } while (!n && errno == EINTR); } } /* If child was signalled, write the reason to stdout like the shell. */ if (cstat->type == CMD_WSTATUS && WIFSIGNALED(cstat->val)) { int signo = WTERMSIG(cstat->val); if (signo && signo != SIGINT && signo != SIGPIPE) { const char *reason = strsignal(signo); n = io_fds[SFD_USERTTY] != -1 ? io_fds[SFD_USERTTY] : STDOUT_FILENO; if (write(n, reason, strlen(reason)) != -1) { if (WCOREDUMP(cstat->val)) { ignore_result(write(n, " (core dumped)", 14)); } ignore_result(write(n, "\n", 1)); } } } utmp_logout(slavename, cstat->type == CMD_WSTATUS ? cstat->val : 0); /* XXX - only if CD_SET_UTMP */ debug_return; } /* * Fill in fdsr and fdsw based on the io buffers list. * Called prior to select(). */ void fd_set_iobs(fd_set *fdsr, fd_set *fdsw) { struct io_buffer *iob; debug_decl(fd_set_iobs, SUDO_DEBUG_EXEC); for (iob = iobufs; iob; iob = iob->next) { if (iob->rfd == -1 && iob->wfd == -1) continue; if (iob->off == iob->len) { iob->off = iob->len = 0; /* Forward the EOF from reader to writer. */ if (iob->rfd == -1) { safe_close(iob->wfd); iob->wfd = -1; } } /* Don't read/write /dev/tty if we are not in the foreground. */ if (iob->rfd != -1 && (ttymode == TERM_RAW || iob->rfd != io_fds[SFD_USERTTY])) { if (iob->len != sizeof(iob->buf)) FD_SET(iob->rfd, fdsr); } if (iob->wfd != -1 && (foreground || iob->wfd != io_fds[SFD_USERTTY])) { if (iob->len > iob->off) FD_SET(iob->wfd, fdsw); } } debug_return; } static void deliver_signal(pid_t pid, int signo, bool from_parent) { char signame[SIG2STR_MAX]; int status; debug_decl(deliver_signal, SUDO_DEBUG_EXEC); if (sig2str(signo, signame) == -1) snprintf(signame, sizeof(signame), "%d", signo); /* Handle signal from parent. */ sudo_debug_printf(SUDO_DEBUG_INFO, "received SIG%s%s", signame, from_parent ? " from parent" : ""); switch (signo) { case SIGALRM: terminate_command(pid, true); break; case SIGCONT_FG: /* Continue in foreground, grant it controlling tty. */ do { status = tcsetpgrp(io_fds[SFD_SLAVE], cmnd_pgrp); } while (status == -1 && errno == EINTR); killpg(pid, SIGCONT); break; case SIGCONT_BG: /* Continue in background, I take controlling tty. */ do { status = tcsetpgrp(io_fds[SFD_SLAVE], getpid()); } while (status == -1 && errno == EINTR); killpg(pid, SIGCONT); break; case SIGKILL: _exit(1); /* XXX */ /* NOTREACHED */ default: /* Relay signal to command. */ killpg(pid, signo); break; } debug_return; } /* * Send status to parent over socketpair. * Return value is the same as send(2). */ static int send_status(int fd, struct command_status *cstat) { int n = -1; debug_decl(send_status, SUDO_DEBUG_EXEC); if (cstat->type != CMD_INVALID) { sudo_debug_printf(SUDO_DEBUG_INFO, "sending status message to parent: [%d, %d]", cstat->type, cstat->val); do { n = send(fd, cstat, sizeof(*cstat), 0); } while (n == -1 && errno == EINTR); if (n != sizeof(*cstat)) { sudo_debug_printf(SUDO_DEBUG_ERROR, "unable to send status to parent: %s", strerror(errno)); } cstat->type = CMD_INVALID; /* prevent re-sending */ } debug_return_int(n); } /* * Wait for command status after receiving SIGCHLD. * If the command was stopped, the status is send back to the parent. * Otherwise, cstat is filled in but not sent. * Returns true if command is still alive, else false. */ static bool handle_sigchld(int backchannel, struct command_status *cstat) { bool alive = true; int status; pid_t pid; debug_decl(handle_sigchld, SUDO_DEBUG_EXEC); /* read command status */ do { pid = waitpid(cmnd_pid, &status, WUNTRACED|WNOHANG); } while (pid == -1 && errno == EINTR); if (pid == cmnd_pid) { if (cstat->type != CMD_ERRNO) { char signame[SIG2STR_MAX]; cstat->type = CMD_WSTATUS; cstat->val = status; if (WIFSTOPPED(status)) { if (sig2str(WSTOPSIG(status), signame) == -1) snprintf(signame, sizeof(signame), "%d", WSTOPSIG(status)); sudo_debug_printf(SUDO_DEBUG_INFO, "command stopped, SIG%s", signame); do { cmnd_pgrp = tcgetpgrp(io_fds[SFD_SLAVE]); } while (cmnd_pgrp == -1 && errno == EINTR); if (send_status(backchannel, cstat) == -1) return alive; /* XXX */ } else if (WIFSIGNALED(status)) { if (sig2str(WTERMSIG(status), signame) == -1) snprintf(signame, sizeof(signame), "%d", WTERMSIG(status)); sudo_debug_printf(SUDO_DEBUG_INFO, "command killed, SIG%s", signame); } else { sudo_debug_printf(SUDO_DEBUG_INFO, "command exited: %d", WEXITSTATUS(status)); } } if (!WIFSTOPPED(status)) alive = false; } debug_return_bool(alive); } /* * Monitor process that creates a new session with the controlling tty, * resets signal handlers and forks a child to call exec_pty(). * Waits for status changes from the command and relays them to the * parent and relays signals from the parent to the command. * Returns an error if fork(2) fails, else calls _exit(2). */ static int exec_monitor(struct command_details *details, int backchannel) { struct command_status cstat; struct timeval tv; fd_set *fdsr; sigaction_t sa; int errpipe[2], maxfd, n, status; bool alive = true; unsigned char signo; debug_decl(exec_monitor, SUDO_DEBUG_EXEC); /* Close unused fds. */ if (io_fds[SFD_MASTER] != -1) close(io_fds[SFD_MASTER]); if (io_fds[SFD_USERTTY] != -1) close(io_fds[SFD_USERTTY]); /* * We use a pipe to atomically handle signal notification within * the select() loop. */ if (pipe_nonblock(signal_pipe) != 0) error(1, _("unable to create pipe")); /* Reset SIGWINCH and SIGALRM. */ zero_bytes(&sa, sizeof(sa)); sigemptyset(&sa.sa_mask); sa.sa_flags = SA_RESTART; sa.sa_handler = SIG_DFL; sigaction(SIGWINCH, &sa, NULL); sigaction(SIGALRM, &sa, NULL); /* Ignore any SIGTTIN or SIGTTOU we get. */ sa.sa_handler = SIG_IGN; sigaction(SIGTTIN, &sa, NULL); sigaction(SIGTTOU, &sa, NULL); /* Note: HP-UX select() will not be interrupted if SA_RESTART set */ sa.sa_flags = SA_INTERRUPT; #ifdef SA_SIGINFO sa.sa_flags |= SA_SIGINFO; sa.sa_sigaction = mon_handler; #else sa.sa_handler = mon_handler; #endif sigaction(SIGCHLD, &sa, NULL); /* Catch common signals so we can cleanup properly. */ sa.sa_flags = SA_RESTART; #ifdef SA_SIGINFO sa.sa_flags |= SA_SIGINFO; sa.sa_sigaction = mon_handler; #else sa.sa_handler = mon_handler; #endif sigaction(SIGHUP, &sa, NULL); sigaction(SIGINT, &sa, NULL); sigaction(SIGQUIT, &sa, NULL); sigaction(SIGTERM, &sa, NULL); sigaction(SIGTSTP, &sa, NULL); sigaction(SIGUSR1, &sa, NULL); sigaction(SIGUSR2, &sa, NULL); /* * Start a new session with the parent as the session leader * and the slave pty as the controlling terminal. * This allows us to be notified when the command has been suspended. */ if (setsid() == -1) { warning("setsid"); goto bad; } if (io_fds[SFD_SLAVE] != -1) { #ifdef TIOCSCTTY if (ioctl(io_fds[SFD_SLAVE], TIOCSCTTY, NULL) != 0) error(1, _("unable to set controlling tty")); #else /* Set controlling tty by reopening slave. */ if ((n = open(slavename, O_RDWR)) >= 0) close(n); #endif } /* * If stdin/stdout is not a tty, start command in the background * since it might be part of a pipeline that reads from /dev/tty. * In this case, we rely on the command receiving SIGTTOU or SIGTTIN * when it needs access to the controlling tty. */ if (pipeline) foreground = false; /* Start command and wait for it to stop or exit */ if (pipe(errpipe) == -1) error(1, _("unable to create pipe")); cmnd_pid = sudo_debug_fork(); if (cmnd_pid == -1) { warning(_("unable to fork")); goto bad; } if (cmnd_pid == 0) { /* We pass errno back to our parent via pipe on exec failure. */ close(backchannel); close(signal_pipe[0]); close(signal_pipe[1]); close(errpipe[0]); fcntl(errpipe[1], F_SETFD, FD_CLOEXEC); restore_signals(); /* setup tty and exec command */ exec_pty(details, &errpipe[1]); cstat.type = CMD_ERRNO; cstat.val = errno; ignore_result(write(errpipe[1], &cstat, sizeof(cstat))); _exit(1); } close(errpipe[1]); /* Send the command's pid to main sudo process. */ cstat.type = CMD_PID; cstat.val = cmnd_pid; ignore_result(send(backchannel, &cstat, sizeof(cstat), 0)); /* If any of stdin/stdout/stderr are pipes, close them in parent. */ if (io_fds[SFD_STDIN] != io_fds[SFD_SLAVE]) close(io_fds[SFD_STDIN]); if (io_fds[SFD_STDOUT] != io_fds[SFD_SLAVE]) close(io_fds[SFD_STDOUT]); if (io_fds[SFD_STDERR] != io_fds[SFD_SLAVE]) close(io_fds[SFD_STDERR]); /* * Put command in its own process group. If we are starting the command * in the foreground, assign its pgrp to the tty. */ cmnd_pgrp = cmnd_pid; setpgid(cmnd_pid, cmnd_pgrp); if (foreground) { do { status = tcsetpgrp(io_fds[SFD_SLAVE], cmnd_pgrp); } while (status == -1 && errno == EINTR); } /* Wait for errno on pipe, signal on backchannel or for SIGCHLD */ maxfd = MAX(MAX(errpipe[0], signal_pipe[0]), backchannel); fdsr = ecalloc(howmany(maxfd + 1, NFDBITS), sizeof(fd_mask)); memset(&cstat, 0, sizeof(cstat)); tv.tv_sec = 0; tv.tv_usec = 0; for (;;) { /* Check for signal on backchannel or errno on errpipe. */ FD_SET(backchannel, fdsr); FD_SET(signal_pipe[0], fdsr); if (errpipe[0] != -1) FD_SET(errpipe[0], fdsr); maxfd = MAX(MAX(errpipe[0], signal_pipe[0]), backchannel); /* If command exited we just poll, there may be data on errpipe. */ n = select(maxfd + 1, fdsr, NULL, NULL, alive ? NULL : &tv); if (n <= 0) { if (n == 0) goto done; if (errno == EINTR || errno == ENOMEM) continue; warning("monitor: %s", _("select failed")); break; } if (FD_ISSET(signal_pipe[0], fdsr)) { n = read(signal_pipe[0], &signo, sizeof(signo)); if (n == -1) { if (errno == EINTR || errno == EAGAIN) continue; warning(_("error reading from signal pipe")); goto done; } /* * Handle SIGCHLD specially and deliver other signals * directly to the command. */ if (signo == SIGCHLD) { if (!handle_sigchld(backchannel, &cstat)) alive = false; } else { deliver_signal(cmnd_pid, signo, false); } continue; } if (errpipe[0] != -1 && FD_ISSET(errpipe[0], fdsr)) { /* read errno or EOF from command pipe */ n = read(errpipe[0], &cstat, sizeof(cstat)); if (n == -1) { if (errno == EINTR) continue; warning(_("error reading from pipe")); goto done; } /* Got errno or EOF, either way we are done with errpipe. */ FD_CLR(errpipe[0], fdsr); close(errpipe[0]); errpipe[0] = -1; } if (FD_ISSET(backchannel, fdsr)) { struct command_status cstmp; /* read command from backchannel, should be a signal */ n = recv(backchannel, &cstmp, sizeof(cstmp), 0); if (n == -1) { if (errno == EINTR) continue; warning(_("error reading from socketpair")); goto done; } if (cstmp.type != CMD_SIGNO) { warningx(_("unexpected reply type on backchannel: %d"), cstmp.type); continue; } deliver_signal(cmnd_pid, cstmp.val, true); } } done: if (alive) { /* XXX An error occurred, should send an error back. */ kill(cmnd_pid, SIGKILL); } else { /* Send parent status. */ send_status(backchannel, &cstat); } sudo_debug_exit_int(__func__, __FILE__, __LINE__, sudo_debug_subsys, 1); _exit(1); bad: debug_return_int(errno); } /* * Flush any output buffered in iobufs or readable from the fds. * Does not read from /dev/tty. */ static void flush_output(void) { struct io_buffer *iob; struct timeval tv; fd_set *fdsr, *fdsw; int nready, nwriters, maxfd = -1; debug_decl(flush_output, SUDO_DEBUG_EXEC); /* Determine maxfd */ for (iob = iobufs; iob; iob = iob->next) { if (iob->rfd > maxfd) maxfd = iob->rfd; if (iob->wfd > maxfd) maxfd = iob->wfd; } if (maxfd == -1) debug_return; fdsr = emalloc2(howmany(maxfd + 1, NFDBITS), sizeof(fd_mask)); fdsw = emalloc2(howmany(maxfd + 1, NFDBITS), sizeof(fd_mask)); for (;;) { memset(fdsw, 0, howmany(maxfd + 1, NFDBITS) * sizeof(fd_mask)); memset(fdsr, 0, howmany(maxfd + 1, NFDBITS) * sizeof(fd_mask)); nwriters = 0; for (iob = iobufs; iob; iob = iob->next) { /* Don't read from /dev/tty while flushing. */ if (io_fds[SFD_USERTTY] != -1 && iob->rfd == io_fds[SFD_USERTTY]) continue; if (iob->rfd == -1 && iob->wfd == -1) continue; if (iob->off == iob->len) { iob->off = iob->len = 0; /* Forward the EOF from reader to writer. */ if (iob->rfd == -1) { safe_close(iob->wfd); iob->wfd = -1; } } if (iob->rfd != -1) { if (iob->len != sizeof(iob->buf)) FD_SET(iob->rfd, fdsr); } if (iob->wfd != -1) { if (iob->len > iob->off) { nwriters++; FD_SET(iob->wfd, fdsw); } } } /* Don't sleep in select if there are no buffers that need writing. */ tv.tv_sec = 0; tv.tv_usec = 0; nready = select(maxfd + 1, fdsr, fdsw, NULL, nwriters ? NULL : &tv); if (nready <= 0) { if (nready == 0) break; /* all I/O flushed */ if (errno == EINTR || errno == ENOMEM) continue; warning(_("select failed")); } if (perform_io(fdsr, fdsw, NULL) != 0 || nready == -1) break; } efree(fdsr); efree(fdsw); debug_return; } /* * Sets up std{in,out,err} and executes the actual command. * Returns only if execve() fails. */ static void exec_pty(struct command_details *details, int *errfd) { pid_t self = getpid(); debug_decl(exec_pty, SUDO_DEBUG_EXEC); /* Set command process group here too to avoid a race. */ setpgid(0, self); /* Wire up standard fds, note that stdout/stderr may be pipes. */ if (dup2(io_fds[SFD_STDIN], STDIN_FILENO) == -1 || dup2(io_fds[SFD_STDOUT], STDOUT_FILENO) == -1 || dup2(io_fds[SFD_STDERR], STDERR_FILENO) == -1) error(1, "dup2"); /* Wait for parent to grant us the tty if we are foreground. */ if (foreground) { while (tcgetpgrp(io_fds[SFD_SLAVE]) != self) ; /* spin */ } /* We have guaranteed that the slave fd is > 2 */ if (io_fds[SFD_SLAVE] != -1) close(io_fds[SFD_SLAVE]); if (io_fds[SFD_STDIN] != io_fds[SFD_SLAVE]) close(io_fds[SFD_STDIN]); if (io_fds[SFD_STDOUT] != io_fds[SFD_SLAVE]) close(io_fds[SFD_STDOUT]); if (io_fds[SFD_STDERR] != io_fds[SFD_SLAVE]) close(io_fds[SFD_STDERR]); sudo_debug_execve(SUDO_DEBUG_INFO, details->command, details->argv, details->envp); if (details->closefrom >= 0) { int maxfd = details->closefrom; dup2(*errfd, maxfd); (void)fcntl(maxfd, F_SETFD, FD_CLOEXEC); *errfd = maxfd++; if (sudo_debug_fd_set(maxfd) != -1) maxfd++; closefrom(maxfd); } #ifdef HAVE_SELINUX if (ISSET(details->flags, CD_RBAC_ENABLED)) { selinux_execve(details->command, details->argv, details->envp, ISSET(details->flags, CD_NOEXEC)); } else #endif { sudo_execve(details->command, details->argv, details->envp, ISSET(details->flags, CD_NOEXEC)); } sudo_debug_printf(SUDO_DEBUG_ERROR, "unable to exec %s: %s", details->command, strerror(errno)); debug_return; } /* * Propagates tty size change signals to pty being used by the command. */ static void sync_ttysize(int src, int dst) { #ifdef TIOCGWINSZ struct winsize wsize; pid_t pgrp; debug_decl(sync_ttysize, SUDO_DEBUG_EXEC); if (ioctl(src, TIOCGWINSZ, &wsize) == 0) { ioctl(dst, TIOCSWINSZ, &wsize); if ((pgrp = tcgetpgrp(dst)) != -1) killpg(pgrp, SIGWINCH); } debug_return; #endif } /* * Handler for SIGWINCH in parent. */ static void sigwinch(int s) { int serrno = errno; sync_ttysize(io_fds[SFD_USERTTY], io_fds[SFD_SLAVE]); errno = serrno; } /* * Only close the fd if it is not /dev/tty or std{in,out,err}. * Return value is the same as send(2). */ static int safe_close(int fd) { debug_decl(safe_close, SUDO_DEBUG_EXEC); /* Avoid closing /dev/tty or std{in,out,err}. */ if (fd < 3 || fd == io_fds[SFD_USERTTY]) { errno = EINVAL; debug_return_int(-1); } debug_return_int(close(fd)); }