src/prompt.c

   1 /* prompt.c -- prompt routines for vlock,
   2  *             the VT locking program for linux
   3  *
   4  * This program is copyright (C) 2007 Frank Benkstein, and is free
   5  * software which is freely distributable under the terms of the
   6  * GNU General Public License version 2, included as the file COPYING in this
   7  * distribution.  It is NOT public domain software, and any
   8  * redistribution not permitted by the GNU General Public License is
   9  * expressly forbidden without prior written permission from
  10  * the author.
  11  *
  12  *
  13  * The prompt functions (prompt and prompt_echo_off) were
  14  * inspired by/copied from openpam's openpam_ttyconv.c:
  15  *
  16  * Copyright (c) 2002-2003 Networks Associates Technology, Inc.
  17  *
  18  * Redistribution and use in source and binary forms, with or without
  19  * modification, are permitted provided that the following conditions
  20  * are met:
  21  * 1. Redistributions of source code must retain the above copyright
  22  *    notice, this list of conditions and the following disclaimer.
  23  * 2. Redistributions in binary form must reproduce the above copyright
  24  *    notice, this list of conditions and the following disclaimer in the
  25  *    documentation and/or other materials provided with the distribution.
  26  * 3. The name of the author may not be used to endorse or promote
  27  *    products derived from this software without specific prior written
  28  *    permission.
  29  *
  30  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
  31  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  32  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  33  * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
  34  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  35  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  36  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  37  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  38  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  39  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  40  * SUCH DAMAGE.
  41  *
  42  */
  43
  44 #include <stdio.h>
  45 #include <stdlib.h>
  46 #include <string.h>
  47 #include <termios.h>
  48 #include <unistd.h>
  49 #include <sys/select.h>
  50 #include <errno.h>
  51
  52 #include "vlock.h"
  53
  54 #define PROMPT_BUFFER_SIZE 512
  55
  56 char *prompt(const char *msg, const struct timespec *timeout) {
  57   char buffer[PROMPT_BUFFER_SIZE];
  58   char *result;
  59   int len;
  60   struct termios term;
  61   struct timeval *timeout_val = NULL;
  62   tcflag_t lflag;
  63   fd_set readfds;
  64
  65   if (timeout != NULL
  66       && (timeout_val = malloc(sizeof *timeout_val)) != NULL) {
  67     timeout_val->tv_sec = timeout->tv_sec;
  68     timeout_val->tv_usec = timeout->tv_nsec / 1000;
  69   }
  70
  71   if (msg != NULL) {
  72     /* Write out the prompt. */
  73     (void) fputs(msg, stderr); fflush(stderr);
  74   }
  75
  76   /* Get the current terminal attributes. */
  77   (void) tcgetattr(STDIN_FILENO, &term);
  78   /* Save the lflag value. */
  79   lflag = term.c_lflag;
  80   /* Enable canonical mode.  We're only interested in line buffering. */
  81   term.c_lflag |= ICANON;
  82   /* Disable terminal signals. */
  83   term.c_lflag &= ~ISIG;
  84   /* Set the terminal attributes. */
  85   (void) tcsetattr(STDIN_FILENO, TCSAFLUSH, &term);
  86   /* Discard all unread input characters. */
  87   (void) tcflush(STDIN_FILENO, TCIFLUSH);
  88
  89   /* Initialize file descriptor set. */
  90   FD_ZERO(&readfds);
  91   FD_SET(STDIN_FILENO, &readfds);
  92
  93   errno = 0;
  94
  95   /* Wait until a string was entered. */
  96   if (select(STDIN_FILENO+1, &readfds, NULL, NULL, timeout_val) != 1) {
  97     if (errno)
  98       perror("vlock-auth: select() on stdin failed");
  99     else
 100       fprintf(stderr, "timeout!\n");
 101
 102     result = NULL;
 103     goto out;
 104   }
 105
 106   /* Read the string from stdin.  At most buffer length - 1 bytes, to
 107    * leave room for the terminating zero byte. */
 108   if ((len = read(STDIN_FILENO, buffer, sizeof buffer - 1)) < 0) {
 109     result = NULL;
 110     goto out;
 111   }
 112
 113   /* Terminate the string. */
 114   buffer[len] = '\0';
 115
 116   /* Strip trailing newline characters. */
 117   for (len = strlen(buffer); len > 0; --len) {
 118     if (buffer[len-1] != '\r' && buffer[len-1] != '\n')
 119       break;
 120   }
 121
 122   /* Terminate the string, again. */
 123   buffer[len] = '\0';
 124
 125   /* Copy the string. */
 126   result = strdup(buffer);
 127
 128   /* Clear our buffer. */
 129   memset(buffer, 0, sizeof buffer);
 130
 131 out:
 132   free(timeout_val);
 133
 134   /* Restore original terminal attributes. */
 135   term.c_lflag = lflag;
 136   (void) tcsetattr(STDIN_FILENO, TCSAFLUSH, &term);
 137
 138   return result;
 139 }
 140
 141 char *prompt_echo_off(const char *msg, const struct timespec *timeout) {
 142   struct termios term;
 143   tcflag_t lflag;
 144   char *result;
 145
 146   (void) tcgetattr(STDIN_FILENO, &term);
 147   lflag = term.c_lflag;
 148   term.c_lflag &= ~ECHO;
 149   (void) tcsetattr(STDIN_FILENO, TCSAFLUSH, &term);
 150
 151   result = prompt(msg, timeout);
 152
 153   term.c_lflag = lflag;
 154   (void) tcsetattr(STDIN_FILENO, TCSAFLUSH, &term);
 155
 156   if (result != NULL)
 157     fputc('\n', stderr);
 158
 159   return result;
 160 }