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 "prompt.h"
  53
  54 #define PROMPT_BUFFER_SIZE 512
  55
  56 /* Prompt with the given string for a single line of input.  The read string is
  57  * returned in a new buffer that should be freed by the caller.  If reading
  58  * fails or the timeout (if given) occurs NULL is retured. */
  59 char *prompt(const char *msg, const struct timespec *timeout)
  60 {
  61   char buffer[PROMPT_BUFFER_SIZE];
  62   char *result = NULL;
  63   ssize_t len;
  64   struct termios term;
  65   struct timeval *timeout_val = NULL;
  66   tcflag_t lflag;
  67   fd_set readfds;
  68
  69   /* copy timeout */
  70   if (timeout != NULL) {
  71     timeout_val = malloc(sizeof *timeout_val);
  72
  73     if (timeout_val == NULL)
  74       return NULL;
  75
  76     timeout_val->tv_sec = timeout->tv_sec;
  77     timeout_val->tv_usec = timeout->tv_nsec / 1000;
  78   }
  79
  80   if (msg != NULL) {
  81     /* Write out the prompt. */
  82     (void) fputs(msg, stderr);
  83     fflush(stderr);
  84   }
  85
  86   /* Get the current terminal attributes. */
  87   (void) tcgetattr(STDIN_FILENO, &term);
  88   /* Save the lflag value. */
  89   lflag = term.c_lflag;
  90   /* Enable canonical mode.  We're only interested in line buffering. */
  91   term.c_lflag |= ICANON;
  92   /* Disable terminal signals. */
  93   term.c_lflag &= ~ISIG;
  94   /* Set the terminal attributes. */
  95   (void) tcsetattr(STDIN_FILENO, TCSAFLUSH, &term);
  96   /* Discard all unread input characters. */
  97   (void) tcflush(STDIN_FILENO, TCIFLUSH);
  98
  99   /* Initialize file descriptor set. */
 100   FD_ZERO(&readfds);
 101   FD_SET(STDIN_FILENO, &readfds);
 102
 103
 104 before_select:
 105   /* Reset errno. */
 106   errno = 0;
 107
 108   /* Wait until a string was entered. */
 109   if (select(STDIN_FILENO + 1, &readfds, NULL, NULL, timeout_val) != 1) {
 110     switch (errno) {
 111       case 0:
 112         fprintf(stderr, "timeout!\n");
 113         goto out;
 114       case EINTR:
 115         /* A signal was caught. Restart. */
 116         goto before_select;
 117       default:
 118         perror("vlock-auth: select() on stdin failed");
 119         goto out;
 120     }
 121   }
 122
 123   /* Read the string from stdin.  At most buffer length - 1 bytes, to
 124    * leave room for the terminating zero byte. */
 125   if ((len = read(STDIN_FILENO, buffer, sizeof buffer - 1)) < 0)
 126     goto out;
 127
 128   /* Terminate the string. */
 129   buffer[len] = '\0';
 130
 131   /* Strip trailing newline characters. */
 132   for (len = strlen(buffer); len > 0; --len)
 133     if (buffer[len - 1] != '\r' && buffer[len - 1] != '\n')
 134       break;
 135
 136   /* Terminate the string, again. */
 137   buffer[len] = '\0';
 138
 139   /* Copy the string.  Success and error paths are the same. */
 140   result = strdup(buffer);
 141
 142   /* Clear our buffer. */
 143   memset(buffer, 0, sizeof buffer);
 144
 145 out:
 146   free(timeout_val);
 147
 148   /* Restore original terminal attributes. */
 149   term.c_lflag = lflag;
 150   (void) tcsetattr(STDIN_FILENO, TCSAFLUSH, &term);
 151
 152   return result;
 153 }
 154
 155 /* Same as prompt except that the characters entered are not echoed. */
 156 char *prompt_echo_off(const char *msg, const struct timespec *timeout)
 157 {
 158   struct termios term;
 159   tcflag_t lflag;
 160   char *result;
 161
 162   (void) tcgetattr(STDIN_FILENO, &term);
 163   lflag = term.c_lflag;
 164   term.c_lflag &= ~ECHO;
 165   (void) tcsetattr(STDIN_FILENO, TCSAFLUSH, &term);
 166
 167   result = prompt(msg, timeout);
 168
 169   term.c_lflag = lflag;
 170   (void) tcsetattr(STDIN_FILENO, TCSAFLUSH, &term);
 171
 172   if (result != NULL)
 173     fputc('\n', stderr);
 174
 175   return result;
 176 }
 177
 178 /* Read a single character from the stdin.  If the timeout is reached
 179  * 0 is returned. */
 180 char read_character(struct timespec *timeout)
 181 {
 182   char c = 0;
 183   struct timeval *timeout_val = NULL;
 184   fd_set readfds;
 185
 186   if (timeout != NULL) {
 187     timeout_val = calloc(sizeof *timeout_val, 1);
 188
 189     if (timeout_val != NULL) {
 190       timeout_val->tv_sec = timeout->tv_sec;
 191       timeout_val->tv_usec = timeout->tv_nsec / 1000;
 192     }
 193   }
 194
 195   /* Initialize file descriptor set. */
 196   FD_ZERO(&readfds);
 197   FD_SET(STDIN_FILENO, &readfds);
 198
 199   /* Wait for a character. */
 200   if (select(STDIN_FILENO + 1, &readfds, NULL, NULL, timeout_val) != 1)
 201     goto out;
 202
 203   /* Read the character. */
 204   (void) read(STDIN_FILENO, &c, 1);
 205
 206 out:
 207   free(timeout_val);
 208   return c;
 209 }
 210
 211 /* Wait for any of the characters in the given character set to be read from
 212  * stdin.  If charset is NULL wait for any character.  Returns 0 when the
 213  * timeout occurs. */
 214 char wait_for_character(const char *charset, struct timespec *timeout)
 215 {
 216   struct termios term;
 217   tcflag_t lflag;
 218   char c;
 219
 220   /* switch off line buffering */
 221   (void) tcgetattr(STDIN_FILENO, &term);
 222   lflag = term.c_lflag;
 223   term.c_lflag &= ~ICANON;
 224   (void) tcsetattr(STDIN_FILENO, TCSANOW, &term);
 225
 226   for (;;) {
 227     c = read_character(timeout);
 228
 229     if (c == 0 || charset == NULL)
 230       break;
 231     else if (strchr(charset, c) != NULL)
 232       break;
 233   }
 234
 235   /* restore line buffering */
 236   term.c_lflag = lflag;
 237   (void) tcsetattr(STDIN_FILENO, TCSANOW, &term);
 238
 239   return c;
 240 }
 241