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;
  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   /* Reset errno. */
 104   errno = 0;
 105
 106   /* Wait until a string was entered. */
 107   if (select(STDIN_FILENO + 1, &readfds, NULL, NULL, timeout_val) != 1) {
 108     if (errno != 0)
 109       perror("vlock-auth: select() on stdin failed");
 110     else
 111       fprintf(stderr, "timeout!\n");
 112
 113     result = NULL;
 114     goto out;
 115   }
 116
 117   /* Read the string from stdin.  At most buffer length - 1 bytes, to
 118    * leave room for the terminating zero byte. */
 119   if ((len = read(STDIN_FILENO, buffer, sizeof buffer - 1)) < 0) {
 120     result = NULL;
 121     goto out;
 122   }
 123
 124   /* Terminate the string. */
 125   buffer[len] = '\0';
 126
 127   /* Strip trailing newline characters. */
 128   for (len = strlen(buffer); len > 0; --len) {
 129     if (buffer[len - 1] != '\r' && buffer[len - 1] != '\n')
 130       break;
 131   }
 132
 133   /* Terminate the string, again. */
 134   buffer[len] = '\0';
 135
 136   /* Copy the string. */
 137   result = strdup(buffer);
 138
 139   /* Clear our buffer. */
 140   memset(buffer, 0, sizeof buffer);
 141
 142 out:
 143   free(timeout_val);
 144
 145   /* Restore original terminal attributes. */
 146   term.c_lflag = lflag;
 147   (void) tcsetattr(STDIN_FILENO, TCSAFLUSH, &term);
 148
 149   return result;
 150 }
 151
 152 /* Same as prompt except that the characters entered are not echoed. */
 153 char *prompt_echo_off(const char *msg, const struct timespec *timeout)
 154 {
 155   struct termios term;
 156   tcflag_t lflag;
 157   char *result;
 158
 159   (void) tcgetattr(STDIN_FILENO, &term);
 160   lflag = term.c_lflag;
 161   term.c_lflag &= ~ECHO;
 162   (void) tcsetattr(STDIN_FILENO, TCSAFLUSH, &term);
 163
 164   result = prompt(msg, timeout);
 165
 166   term.c_lflag = lflag;
 167   (void) tcsetattr(STDIN_FILENO, TCSAFLUSH, &term);
 168
 169   if (result != NULL)
 170     fputc('\n', stderr);
 171
 172   return result;
 173 }
 174
 175 /* Read a single character from the stdin.  If the timeout is reached
 176  * 0 is returned. */
 177 char read_character(struct timespec *timeout)
 178 {
 179   char c = 0;
 180   struct timeval *timeout_val = NULL;
 181   fd_set readfds;
 182
 183   if (timeout != NULL) {
 184     timeout_val = calloc(sizeof *timeout_val, 1);
 185
 186     if (timeout_val != NULL) {
 187       timeout_val->tv_sec = timeout->tv_sec;
 188       timeout_val->tv_usec = timeout->tv_nsec / 1000;
 189     }
 190   }
 191
 192   /* Initialize file descriptor set. */
 193   FD_ZERO(&readfds);
 194   FD_SET(STDIN_FILENO, &readfds);
 195
 196   /* Wait for a character. */
 197   if (select(STDIN_FILENO + 1, &readfds, NULL, NULL, timeout_val) != 1)
 198     goto out;
 199
 200   /* Read the character. */
 201   (void) read(STDIN_FILENO, &c, 1);
 202
 203 out:
 204   free(timeout_val);
 205   return c;
 206 }
 207
 208 /* Wait for any of the characters in the given character set to be read from
 209  * stdin.  If charset is NULL wait for any character.  Returns 0 when the
 210  * timeout occurs. */
 211 char wait_for_character(const char *charset, struct timespec *timeout)
 212 {
 213   struct termios term;
 214   tcflag_t lflag;
 215   char c;
 216
 217   /* switch off line buffering */
 218   (void) tcgetattr(STDIN_FILENO, &term);
 219   lflag = term.c_lflag;
 220   term.c_lflag &= ~ICANON;
 221   (void) tcsetattr(STDIN_FILENO, TCSANOW, &term);
 222
 223   for (;;) {
 224     c = read_character(timeout);
 225
 226     if (c == 0 || charset == NULL)
 227       break;
 228     else if (strchr(charset, c) != NULL)
 229       break;
 230   }
 231
 232   /* restore line buffering */
 233   term.c_lflag = lflag;
 234   (void) tcsetattr(STDIN_FILENO, TCSANOW, &term);
 235
 236   return c;
 237 }
 238