diff options
Diffstat (limited to 'src/tgetpass.c')
| -rw-r--r-- | src/tgetpass.c | 456 |
1 files changed, 456 insertions, 0 deletions
diff --git a/src/tgetpass.c b/src/tgetpass.c new file mode 100644 index 0000000..935afac --- /dev/null +++ b/src/tgetpass.c @@ -0,0 +1,456 @@ +/* + * SPDX-License-Identifier: ISC + * + * Copyright (c) 1996, 1998-2005, 2007-2021 + * Todd C. Miller <Todd.Miller@sudo.ws> + * + * 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. + * + * Sponsored in part by the Defense Advanced Research Projects + * Agency (DARPA) and Air Force Research Laboratory, Air Force + * Materiel Command, USAF, under agreement number F39502-99-1-0512. + */ + +/* + * This is an open source non-commercial project. Dear PVS-Studio, please check it. + * PVS-Studio Static Code Analyzer for C, C++ and C#: http://www.viva64.com + */ + +#ifdef __TANDEM +# include <floss.h> +#endif + +#include <config.h> + +#include <sys/wait.h> +#include <stdio.h> +#include <stdlib.h> +#include <string.h> +#include <unistd.h> +#include <errno.h> +#include <signal.h> +#include <fcntl.h> + +#include "sudo.h" +#include "sudo_plugin.h" + +enum tgetpass_errval { + TGP_ERRVAL_NOERROR, + TGP_ERRVAL_TIMEOUT, + TGP_ERRVAL_NOPASSWORD, + TGP_ERRVAL_READERROR +}; + +static volatile sig_atomic_t signo[NSIG]; + +static void tgetpass_handler(int); +static char *getln(int, char *, size_t, bool, enum tgetpass_errval *); +static char *sudo_askpass(const char *, const char *); + +static int +suspend(int sig, struct sudo_conv_callback *callback) +{ + int ret = 0; + debug_decl(suspend, SUDO_DEBUG_CONV); + + if (callback != NULL && SUDO_API_VERSION_GET_MAJOR(callback->version) != SUDO_CONV_CALLBACK_VERSION_MAJOR) { + sudo_debug_printf(SUDO_DEBUG_WARN|SUDO_DEBUG_LINENO, + "callback major version mismatch, expected %u, got %u", + SUDO_CONV_CALLBACK_VERSION_MAJOR, + SUDO_API_VERSION_GET_MAJOR(callback->version)); + callback = NULL; + } + + if (callback != NULL && callback->on_suspend != NULL) { + if (callback->on_suspend(sig, callback->closure) == -1) + ret = -1; + } + kill(getpid(), sig); + if (callback != NULL && callback->on_resume != NULL) { + if (callback->on_resume(sig, callback->closure) == -1) + ret = -1; + } + debug_return_int(ret); +} + +static void +tgetpass_display_error(enum tgetpass_errval errval) +{ + debug_decl(tgetpass_display_error, SUDO_DEBUG_CONV); + + switch (errval) { + case TGP_ERRVAL_NOERROR: + break; + case TGP_ERRVAL_TIMEOUT: + sudo_warnx("%s", U_("timed out reading password")); + break; + case TGP_ERRVAL_NOPASSWORD: + sudo_warnx("%s", U_("no password was provided")); + break; + case TGP_ERRVAL_READERROR: + sudo_warn("%s", U_("unable to read password")); + break; + } + debug_return; +} + +/* + * Like getpass(3) but with timeout and echo flags. + */ +char * +tgetpass(const char *prompt, int timeout, int flags, + struct sudo_conv_callback *callback) +{ + struct sigaction sa, savealrm, saveint, savehup, savequit, saveterm; + struct sigaction savetstp, savettin, savettou; + char *pass; + static const char *askpass; + static char buf[SUDO_CONV_REPL_MAX + 1]; + int i, input, output, save_errno, ttyfd; + bool feedback, need_restart, neednl; + enum tgetpass_errval errval; + debug_decl(tgetpass, SUDO_DEBUG_CONV); + + (void) fflush(stdout); + + if (askpass == NULL) { + askpass = getenv_unhooked("SUDO_ASKPASS"); + if (askpass == NULL || *askpass == '\0') + askpass = sudo_conf_askpass_path(); + } + +restart: + /* Try to open /dev/tty if we are going to be using it for I/O. */ + ttyfd = -1; + if (!ISSET(flags, TGP_STDIN|TGP_ASKPASS)) { + /* If no tty present and we need to disable echo, try askpass. */ + ttyfd = open(_PATH_TTY, O_RDWR); + if (ttyfd == -1 && !ISSET(flags, TGP_ECHO|TGP_NOECHO_TRY)) { + if (askpass == NULL || getenv_unhooked("DISPLAY") == NULL) { + sudo_warnx("%s", + U_("a terminal is required to read the password; either use the -S option to read from standard input or configure an askpass helper")); + debug_return_str(NULL); + } + SET(flags, TGP_ASKPASS); + } + } + + /* If using a helper program to get the password, run it instead. */ + if (ISSET(flags, TGP_ASKPASS)) { + if (askpass == NULL || *askpass == '\0') + sudo_fatalx("%s", + U_("no askpass program specified, try setting SUDO_ASKPASS")); + debug_return_str_masked(sudo_askpass(askpass, prompt)); + } + + /* Reset state. */ + for (i = 0; i < NSIG; i++) + signo[i] = 0; + pass = NULL; + save_errno = 0; + neednl = false; + need_restart = false; + feedback = false; + + /* Use tty for reading/writing if available else use stdin/stderr. */ + if (ttyfd == -1) { + input = STDIN_FILENO; + output = STDERR_FILENO; + /* Don't try to mask password if /dev/tty is not available. */ + CLR(flags, TGP_MASK); + } else { + input = ttyfd; + output = ttyfd; + } + + /* + * If we are using a tty but are not the foreground pgrp this will + * return EINTR. We send ourself SIGTTOU bracketed by callbacks. + */ + if (!ISSET(flags, TGP_ECHO)) { + for (;;) { + if (ISSET(flags, TGP_MASK)) + neednl = feedback = sudo_term_cbreak(input); + else + neednl = sudo_term_noecho(input); + if (neednl || errno != EINTR) + break; + /* Received SIGTTOU, suspend the process. */ + if (suspend(SIGTTOU, callback) == -1) { + if (ttyfd != -1) + (void) close(ttyfd); + debug_return_ptr(NULL); + } + } + } + + /* + * Catch signals that would otherwise cause the user to end + * up with echo turned off in the shell. + */ + memset(&sa, 0, sizeof(sa)); + sigemptyset(&sa.sa_mask); + sa.sa_flags = 0; /* don't restart system calls */ + sa.sa_handler = tgetpass_handler; + (void) sigaction(SIGALRM, &sa, &savealrm); + (void) sigaction(SIGINT, &sa, &saveint); + (void) sigaction(SIGHUP, &sa, &savehup); + (void) sigaction(SIGQUIT, &sa, &savequit); + (void) sigaction(SIGTERM, &sa, &saveterm); + (void) sigaction(SIGTSTP, &sa, &savetstp); + (void) sigaction(SIGTTIN, &sa, &savettin); + (void) sigaction(SIGTTOU, &sa, &savettou); + + if (ISSET(flags, TGP_BELL) && output != STDERR_FILENO) { + /* Ring the bell if requested and there is a tty. */ + if (write(output, "\a", 1) == -1) + goto restore; + } + if (prompt) { + if (write(output, prompt, strlen(prompt)) == -1) + goto restore; + } + + if (timeout > 0) + alarm(timeout); + pass = getln(input, buf, sizeof(buf), feedback, &errval); + alarm(0); + save_errno = errno; + + if (neednl || pass == NULL) { + if (write(output, "\n", 1) == -1) + goto restore; + } + tgetpass_display_error(errval); + +restore: + /* Restore old signal handlers. */ + (void) sigaction(SIGALRM, &savealrm, NULL); + (void) sigaction(SIGINT, &saveint, NULL); + (void) sigaction(SIGHUP, &savehup, NULL); + (void) sigaction(SIGQUIT, &savequit, NULL); + (void) sigaction(SIGTERM, &saveterm, NULL); + (void) sigaction(SIGTSTP, &savetstp, NULL); + (void) sigaction(SIGTTIN, &savettin, NULL); + (void) sigaction(SIGTTOU, &savettou, NULL); + + /* Restore old tty settings. */ + if (!ISSET(flags, TGP_ECHO)) { + /* Restore old tty settings if possible. */ + if (!sudo_term_restore(input, true)) + sudo_warn("%s", U_("unable to restore terminal settings")); + } + if (ttyfd != -1) + (void) close(ttyfd); + + /* + * If we were interrupted by a signal, resend it to ourselves + * now that we have restored the signal handlers. + */ + for (i = 0; i < NSIG; i++) { + if (signo[i]) { + switch (i) { + case SIGALRM: + break; + case SIGTSTP: + case SIGTTIN: + case SIGTTOU: + if (suspend(i, callback) == 0) + need_restart = true; + break; + default: + kill(getpid(), i); + break; + } + } + } + if (need_restart) + goto restart; + + if (save_errno) + errno = save_errno; + + debug_return_str_masked(pass); +} + +/* + * Fork a child and exec sudo-askpass to get the password from the user. + */ +static char * +sudo_askpass(const char *askpass, const char *prompt) +{ + static char buf[SUDO_CONV_REPL_MAX + 1], *pass; + struct sudo_cred *cred = &user_details.cred; + sigset_t chldmask; + enum tgetpass_errval errval; + int pfd[2], status; + pid_t child; + debug_decl(sudo_askpass, SUDO_DEBUG_CONV); + + /* Block SIGCHLD for the duration since we call waitpid() below. */ + sigemptyset(&chldmask); + sigaddset(&chldmask, SIGCHLD); + (void)sigprocmask(SIG_BLOCK, &chldmask, NULL); + + if (pipe2(pfd, O_CLOEXEC) == -1) + sudo_fatal("%s", U_("unable to create pipe")); + + child = sudo_debug_fork(); + if (child == -1) + sudo_fatal("%s", U_("unable to fork")); + + if (child == 0) { + /* child, set stdout to write side of the pipe */ + if (dup3(pfd[1], STDOUT_FILENO, 0) == -1) { + sudo_warn("dup3"); + _exit(255); + } + if (setuid(ROOT_UID) == -1) + sudo_warn("setuid(%d)", ROOT_UID); + /* Close fds before uid change to prevent prlimit sabotage on Linux. */ + closefrom(STDERR_FILENO + 1); + /* Run the askpass program with the user's original resource limits. */ + restore_limits(); + /* But avoid a setuid() failure on Linux due to RLIMIT_NPROC. */ + unlimit_nproc(); + if (setgid(cred->gid)) { + sudo_warn(U_("unable to set gid to %u"), (unsigned int)cred->gid); + _exit(255); + } + if (cred->ngroups != -1) { + if (sudo_setgroups(cred->ngroups, cred->groups) == -1) { + sudo_warn("%s", U_("unable to set supplementary group IDs")); + _exit(255); + } + } + if (setuid(cred->uid)) { + sudo_warn(U_("unable to set uid to %u"), (unsigned int)cred->uid); + _exit(255); + } + restore_nproc(); + execl(askpass, askpass, prompt, (char *)NULL); + sudo_warn(U_("unable to run %s"), askpass); + _exit(255); + } + + /* Get response from child (askpass). */ + (void) close(pfd[1]); + pass = getln(pfd[0], buf, sizeof(buf), 0, &errval); + (void) close(pfd[0]); + + tgetpass_display_error(errval); + + /* Wait for child to exit. */ + for (;;) { + pid_t rv = waitpid(child, &status, 0); + if (rv == -1 && errno != EINTR) + break; + if (rv != -1 && !WIFSTOPPED(status)) + break; + } + + if (pass == NULL) + errno = EINTR; /* make cancel button simulate ^C */ + + /* Unblock SIGCHLD. */ + (void)sigprocmask(SIG_UNBLOCK, &chldmask, NULL); + + debug_return_str_masked(pass); +} + +extern int sudo_term_eof, sudo_term_erase, sudo_term_kill; + +static char * +getln(int fd, char *buf, size_t bufsiz, bool feedback, + enum tgetpass_errval *errval) +{ + size_t left = bufsiz; + ssize_t nr = -1; + char *cp = buf; + char c = '\0'; + debug_decl(getln, SUDO_DEBUG_CONV); + + *errval = TGP_ERRVAL_NOERROR; + + if (left == 0) { + *errval = TGP_ERRVAL_READERROR; + errno = EINVAL; + debug_return_str(NULL); + } + + while (--left) { + nr = read(fd, &c, 1); + if (nr != 1 || c == '\n' || c == '\r') + break; + if (feedback) { + if (c == sudo_term_eof) { + nr = 0; + break; + } else if (c == sudo_term_kill) { + while (cp > buf) { + if (write(fd, "\b \b", 3) == -1) + break; + cp--; + } + cp = buf; + left = bufsiz; + continue; + } else if (c == sudo_term_erase) { + if (cp > buf) { + ignore_result(write(fd, "\b \b", 3)); + cp--; + left++; + } + continue; + } + ignore_result(write(fd, "*", 1)); + } + *cp++ = c; + } + *cp = '\0'; + if (feedback) { + /* erase stars */ + while (cp > buf) { + if (write(fd, "\b \b", 3) == -1) + break; + --cp; + } + } + + switch (nr) { + case -1: + /* Read error */ + if (errno == EINTR) { + if (signo[SIGALRM] == 1) + *errval = TGP_ERRVAL_TIMEOUT; + } else { + *errval = TGP_ERRVAL_READERROR; + } + debug_return_str(NULL); + case 0: + /* EOF is only an error if no bytes were read. */ + if (left == bufsiz - 1) { + *errval = TGP_ERRVAL_NOPASSWORD; + debug_return_str(NULL); + } + FALLTHROUGH; + default: + debug_return_str_masked(buf); + } +} + +static void +tgetpass_handler(int s) +{ + signo[s] = 1; +} |