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/* -*- coding: utf-8 -*- */
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* Passprompt - Read a password from the terminal and print it
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* Copyright © 2007-2008 Teddy Hogeborn & Björn Påhlsson
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* This program is free software: you can redistribute it and/or
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* modify it under the terms of the GNU General Public License as
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* published by the Free Software Foundation, either version 3 of the
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* License, or (at your option) any later version.
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* This program is distributed in the hope that it will be useful, but
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* WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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* General Public License for more details.
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* You should have received a copy of the GNU General Public License
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* along with this program. If not, see
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* <http://www.gnu.org/licenses/>.
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* Contact the authors at <https://www.fukt.bsnet.se/~belorn/> and
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* <https://www.fukt.bsnet.se/~teddy/>.
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#define _GNU_SOURCE /* getline() */
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#include <termios.h> /* struct termios, tcsetattr(),
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TCSAFLUSH, tcgetattr(), ECHO */
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#include <unistd.h> /* struct termios, tcsetattr(),
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STDIN_FILENO, TCSAFLUSH,
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#include <signal.h> /* sig_atomic_t, raise(), struct
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sigaction, sigemptyset(),
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sigaction(), sigaddset(), SIGINT,
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SIGQUIT, SIGHUP, SIGTERM */
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#include <stddef.h> /* NULL, size_t, ssize_t */
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#include <sys/types.h> /* ssize_t */
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#include <stdlib.h> /* EXIT_SUCCESS, EXIT_FAILURE,
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#include <stdio.h> /* fprintf(), stderr, getline(),
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stdin, feof(), perror(), fputc(),
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stdout, getopt_long */
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#include <errno.h> /* errno, EINVAL */
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#include <iso646.h> /* or, not */
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#include <stdbool.h> /* bool, false, true */
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#include <string.h> /* strlen, rindex, strncmp, strcmp */
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#include <argp.h> /* struct argp_option, struct
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argp_state, struct argp,
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argp_parse(), error_t,
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ARGP_KEY_ARG, ARGP_KEY_END,
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volatile bool quit_now = false;
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const char *argp_program_version = "password-prompt 1.0";
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const char *argp_program_bug_address = "<mandos@fukt.bsnet.se>";
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static void termination_handler(__attribute__((unused))int signum){
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int main(int argc, char **argv){
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struct termios t_new, t_old;
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int status = EXIT_SUCCESS;
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struct sigaction old_action,
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new_action = { .sa_handler = termination_handler,
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struct argp_option options[] = {
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{ .name = "prefix", .key = 'p',
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.arg = "PREFIX", .flags = 0,
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.doc = "Prefix used before the passprompt", .group = 2 },
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{ .name = "debug", .key = 128,
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.doc = "Debug mode", .group = 3 },
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error_t parse_opt (int key, char *arg, struct argp_state *state) {
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/* Get the INPUT argument from `argp_parse', which we know is a
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pointer to our plugin list pointer. */
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return ARGP_ERR_UNKNOWN;
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struct argp argp = { .options = options, .parser = parse_opt,
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.doc = "Mandos Passprompt -- Provides a passprompt" };
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ret = argp_parse (&argp, argc, argv, 0, 0, NULL);
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if (ret == ARGP_ERR_UNKNOWN){
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fprintf(stderr, "Unknown error while parsing arguments\n");
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fprintf(stderr, "Starting %s\n", argv[0]);
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fprintf(stderr, "Storing current terminal attributes\n");
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if (tcgetattr(STDIN_FILENO, &t_old) != 0){
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sigemptyset(&new_action.sa_mask);
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sigaddset(&new_action.sa_mask, SIGINT);
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sigaddset(&new_action.sa_mask, SIGHUP);
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sigaddset(&new_action.sa_mask, SIGTERM);
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ret = sigaction(SIGINT, NULL, &old_action);
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if (old_action.sa_handler != SIG_IGN){
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ret = sigaction(SIGINT, &new_action, NULL);
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ret = sigaction(SIGHUP, NULL, &old_action);
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if (old_action.sa_handler != SIG_IGN){
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ret = sigaction(SIGHUP, &new_action, NULL);
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ret = sigaction(SIGTERM, NULL, &old_action);
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if (old_action.sa_handler != SIG_IGN){
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ret = sigaction(SIGTERM, &new_action, NULL);
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fprintf(stderr, "Removing echo flag from terminal attributes\n");
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t_new.c_lflag &= ~ECHO;
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if (tcsetattr(STDIN_FILENO, TCSAFLUSH, &t_new) != 0){
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perror("tcsetattr-echo");
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fprintf(stderr, "Waiting for input from stdin \n");
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status = EXIT_FAILURE;
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fprintf(stderr, "%s Password: ", prefix);
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fprintf(stderr, "Password: ");
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ret = getline(&buffer, &n, stdin);
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fprintf(stdout, "%s", buffer);
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status = EXIT_SUCCESS;
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if (errno != EINTR and not feof(stdin)){
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status = EXIT_FAILURE;
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/* if(ret == 0), then the only sensible thing to do is to retry to
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fprintf(stderr, "Restoring terminal attributes\n");
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if (tcsetattr(STDIN_FILENO, TCSAFLUSH, &t_old) != 0){
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perror("tcsetattr+echo");
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fprintf(stderr, "%s is exiting\n", argv[0]);