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;
  62   struct timeval *timeout_val_p = NULL;
  63   tcflag_t lflag;
  64   fd_set readfds;
  65
  66   if (timeout != NULL) {
  67     timeout_val.tv_sec = timeout->tv_sec;
  68     timeout_val.tv_usec = timeout->tv_nsec / 1000;
  69     timeout_val_p = &timeout_val;
  70   }
  71
  72   if (msg != NULL) {
  73     /* Write out the prompt. */
  74     (void) fputs(msg, stderr); fflush(stderr);
  75   }
  76
  77   /* Get the current terminal attributes. */
  78   (void) tcgetattr(STDIN_FILENO, &term);
  79   /* Save the lflag value. */
  80   lflag = term.c_lflag;
  81   /* Enable canonical mode.  We're only interested in line buffering. */
  82   term.c_lflag |= ICANON;
  83   /* Disable terminal signals. */
  84   term.c_lflag &= ~ISIG;
  85   /* Set the terminal attributes. */
  86   (void) tcsetattr(STDIN_FILENO, TCSAFLUSH, &term);
  87   /* Discard all unread input characters. */
  88   (void) tcflush(STDIN_FILENO, TCIFLUSH);
  89
  90   /* Initialize file descriptor set. */
  91   FD_ZERO(&readfds);
  92   FD_SET(STDIN_FILENO, &readfds);
  93
  94   errno = 0;
  95
  96   /* Wait until a string was entered. */
  97   if (select(STDIN_FILENO+1, &readfds, NULL, NULL, timeout_val_p) != 1) {
  98     if (errno)
  99       perror("vlock-auth: select() on stdin failed");
 100     else
 101       fprintf(stderr, "timeout!\n");
 102
 103     result = NULL;
 104     goto out;
 105   }
 106
 107   /* Read the string from stdin.  At most buffer length - 1 bytes, to
 108    * leave room for the terminating zero byte. */
 109   if ((len = read(STDIN_FILENO, buffer, sizeof buffer - 1)) < 0) {
 110     result = NULL;
 111     goto out;
 112   }
 113
 114   /* Terminate the string. */
 115   buffer[len] = '\0';
 116
 117   /* Strip trailing newline characters. */
 118   for (len = strlen(buffer); len > 0; --len) {
 119     if (buffer[len-1] != '\r' && buffer[len-1] != '\n')
 120       break;
 121   }
 122
 123   /* Terminate the string, again. */
 124   buffer[len] = '\0';
 125
 126   /* Copy the string. */
 127   result = strdup(buffer);
 128
 129   /* Clear our buffer. */
 130   memset(buffer, 0, sizeof buffer);
 131
 132 out:
 133   /* Restore original terminal attributes. */
 134   term.c_lflag = lflag;
 135   (void) tcsetattr(STDIN_FILENO, TCSAFLUSH, &term);
 136
 137   return result;
 138 }
 139
 140 char *prompt_echo_off(const char *msg, const struct timespec *timeout) {
 141   struct termios term;
 142   tcflag_t lflag;
 143   char *result;
 144
 145   (void) tcgetattr(STDIN_FILENO, &term);
 146   lflag = term.c_lflag;
 147   term.c_lflag &= ~ECHO;
 148   (void) tcsetattr(STDIN_FILENO, TCSAFLUSH, &term);
 149
 150   result = prompt(msg, timeout);
 151
 152   term.c_lflag = lflag;
 153   (void) tcsetattr(STDIN_FILENO, TCSAFLUSH, &term);
 154
 155   if (result != NULL)
 156     fputc('\n', stderr);
 157
 158   return result;
 159 }