libc/unistd/getpass.c

   1 /* Copyright (C) 1992-1999,2001,2003,2004,2005 Free Software Foundation, Inc.
   2    This file is part of the GNU C Library.
   3
   4    The GNU C Library is free software; you can redistribute it and/or
   5    modify it under the terms of the GNU Lesser General Public
   6    License as published by the Free Software Foundation; either
   7    version 2.1 of the License, or (at your option) any later version.
   8
   9    The GNU C Library is distributed in the hope that it will be useful,
  10    but WITHOUT ANY WARRANTY; without even the implied warranty of
  11    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  12    Lesser General Public License for more details.
  13
  14    You should have received a copy of the GNU Lesser General Public
  15    License along with the GNU C Library; if not, see
  16    <http://www.gnu.org/licenses/>.  */
  17
  18 #include <stdio.h>
  19 #include <string.h>
  20 #include <termios.h>
  21 #include <unistd.h>
  22 #include <malloc.h>
  23
  24 #if defined __USE_BSD || (defined __USE_XOPEN && !defined __USE_XOPEN2K)
  25
  26
  27 /* It is desirable to use this bit on systems that have it.
  28    The only bit of terminal state we want to twiddle is echoing, which is
  29    done in software; there is no need to change the state of the terminal
  30    hardware.  */
  31
  32 #ifndef TCSASOFT
  33 #define TCSASOFT 0
  34 #endif
  35 #define PWD_BUFFER_SIZE 256
  36
  37 char * getpass (const char *prompt)
  38 {
  39   FILE *in, *out;
  40   struct termios s, t;
  41   int tty_changed;
  42   static char *buf = NULL;
  43   int nread;
  44
  45   if (buf == NULL)
  46     buf = (char *)__uc_malloc(PWD_BUFFER_SIZE);
  47
  48   /* Try to write to and read from the terminal if we can.
  49      If we can't open the terminal, use stderr and stdin.  */
  50
  51   out = in = fopen ("/dev/tty", "r+");
  52   if (in == NULL)
  53     {
  54       in = stdin;
  55       out = stderr;
  56     }
  57   else
  58     {
  59       /* Disable buffering for read/write FILE to prevent problems with
  60        * fseek and buffering for read/write auto-transitioning. */
  61       setvbuf(in, NULL, _IONBF, 0);
  62     }
  63
  64   /* Turn echoing off if it is on now.  */
  65
  66   tty_changed = 0;
  67   if (tcgetattr (fileno (in), &t) == 0)
  68     {
  69       /* Save the old one. */
  70       s = t;
  71       /* Tricky, tricky. */
  72       t.c_lflag &= ~(ECHO|ISIG);
  73       tty_changed = (tcsetattr (fileno (in), TCSAFLUSH|TCSASOFT, &t) == 0);
  74     }
  75
  76   /* Write the prompt.  */
  77   fputs(prompt, out);
  78   fflush(out);
  79
  80   /* Read the password.  */
  81   if (!fgets (buf, PWD_BUFFER_SIZE, in))
  82     buf[0] = '\0';
  83   nread = strlen(buf);
  84   if (nread > 0 && buf[nread - 1] == '\n')
  85       /* Remove the newline.  */
  86       buf[nread - 1] = '\0';
  87
  88   if (tty_changed)
  89     {
  90       /* Write the newline that was not echoed.  */
  91       putc('\n', out);
  92       /* Restore the original setting.  */
  93       (void) tcsetattr (fileno (in), TCSAFLUSH|TCSASOFT, &s);
  94     }
  95
  96   if (in != stdin)
  97     /* We opened the terminal; now close it.  */
  98     fclose (in);
  99
 100   return buf;
 101 }
 102 #endif