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readpassphrase.c

/*    $OpenBSD: readpassphrase.c,v 1.21 2008/01/17 16:27:07 millert Exp $     */

/*
 * Copyright (c) 2000-2002, 2007 Todd C. Miller <Todd.Miller@courtesan.com>
 *
 * Permission to use, copy, modify, and distribute this software for any
 * purpose with or without fee is hereby granted, provided that the above
 * copyright notice and this permission notice appear in all copies.
 *
 * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
 * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
 * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
 * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
 * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
 * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
 * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
 *
 * Sponsored in part by the Defense Advanced Research Projects
 * Agency (DARPA) and Air Force Research Laboratory, Air Force
 * Materiel Command, USAF, under agreement number F39502-99-1-0512.
 */

#include <ctype.h>
#include <errno.h>
#include <fcntl.h>
#include <paths.h>
#include <pwd.h>
#include <signal.h>
#include <string.h>
#include <termios.h>
#include <unistd.h>
#include <readpassphrase.h>

static volatile sig_atomic_t signo;

static void handler(int);

char *
readpassphrase(const char *prompt, char *buf, size_t bufsiz, int flags)
{
      ssize_t nr;
      int input, output, save_errno;
      char ch, *p, *end;
      struct termios term, oterm;
      struct sigaction sa, savealrm, saveint, savehup, savequit, saveterm;
      struct sigaction savetstp, savettin, savettou, savepipe;

      /* I suppose we could alloc on demand in this case (XXX). */
      if (bufsiz == 0) {
            errno = EINVAL;
            return(NULL);
      }

restart:
      signo = 0;
      nr = -1;
      save_errno = 0;
      /*
       * Read and write to /dev/tty if available.  If not, read from
       * stdin and write to stderr unless a tty is required.
       */
      if ((flags & RPP_STDIN) ||
          (input = output = open(_PATH_TTY, O_RDWR)) == -1) {
            if (flags & RPP_REQUIRE_TTY) {
                  errno = ENOTTY;
                  return(NULL);
            }
            input = STDIN_FILENO;
            output = STDERR_FILENO;
      }

      /*
       * Catch signals that would otherwise cause the user to end
       * up with echo turned off in the shell.  Don't worry about
       * things like SIGXCPU and SIGVTALRM for now.
       */
      sigemptyset(&sa.sa_mask);
      sa.sa_flags = 0;        /* don't restart system calls */
      sa.sa_handler = handler;
      (void)sigaction(SIGALRM, &sa, &savealrm);
      (void)sigaction(SIGHUP, &sa, &savehup);
      (void)sigaction(SIGINT, &sa, &saveint);
      (void)sigaction(SIGPIPE, &sa, &savepipe);
      (void)sigaction(SIGQUIT, &sa, &savequit);
      (void)sigaction(SIGTERM, &sa, &saveterm);
      (void)sigaction(SIGTSTP, &sa, &savetstp);
      (void)sigaction(SIGTTIN, &sa, &savettin);
      (void)sigaction(SIGTTOU, &sa, &savettou);

      /* Turn off echo if possible. */
      if (input != STDIN_FILENO && tcgetattr(input, &oterm) == 0) {
            memcpy(&term, &oterm, sizeof(term));
            if (!(flags & RPP_ECHO_ON))
                  term.c_lflag &= ~(ECHO | ECHONL);
            if (term.c_cc[VSTATUS] != _POSIX_VDISABLE)
                  term.c_cc[VSTATUS] = _POSIX_VDISABLE;
            (void)tcsetattr(input, TCSAFLUSH|TCSASOFT, &term);
      } else {
            memset(&term, 0, sizeof(term));
            term.c_lflag |= ECHO;
            memset(&oterm, 0, sizeof(oterm));
            oterm.c_lflag |= ECHO;
      }

      /* No I/O if we are already backgrounded. */
      if (signo != SIGTTOU && signo != SIGTTIN) {
            if (!(flags & RPP_STDIN))
                  (void)write(output, prompt, strlen(prompt));
            end = buf + bufsiz - 1;
            p = buf;
            while ((nr = read(input, &ch, 1)) == 1 && ch != '\n' && ch != '\r') {
                  if (p < end) {
                        if ((flags & RPP_SEVENBIT))
                              ch &= 0x7f;
                        if (isalpha(ch)) {
                              if ((flags & RPP_FORCELOWER))
                                    ch = (char)tolower(ch);
                              if ((flags & RPP_FORCEUPPER))
                                    ch = (char)toupper(ch);
                        }
                        *p++ = ch;
                  }
            }
            *p = '\0';
            save_errno = errno;
            if (!(term.c_lflag & ECHO))
                  (void)write(output, "\n", 1);
      }

      /* Restore old terminal settings and signals. */
      if (memcmp(&term, &oterm, sizeof(term)) != 0) {
            while (tcsetattr(input, TCSAFLUSH|TCSASOFT, &oterm) == -1 &&
                errno == EINTR)
                  continue;
      }
      (void)sigaction(SIGALRM, &savealrm, NULL);
      (void)sigaction(SIGHUP, &savehup, NULL);
      (void)sigaction(SIGINT, &saveint, NULL);
      (void)sigaction(SIGQUIT, &savequit, NULL);
      (void)sigaction(SIGPIPE, &savepipe, NULL);
      (void)sigaction(SIGTERM, &saveterm, NULL);
      (void)sigaction(SIGTSTP, &savetstp, NULL);
      (void)sigaction(SIGTTIN, &savettin, NULL);
      (void)sigaction(SIGTTOU, &savettou, NULL);
      if (input != STDIN_FILENO)
            (void)close(input);

      /*
       * If we were interrupted by a signal, resend it to ourselves
       * now that we have restored the signal handlers.
       */
      if (signo) {
            kill(getpid(), signo);
            switch (signo) {
            case SIGTSTP:
            case SIGTTIN:
            case SIGTTOU:
                  goto restart;
            }
      }

      if (save_errno)
            errno = save_errno;
      return(nr == -1 ? NULL : buf);
}

char *
getpass(const char *prompt)
{
      static char buf[_PASSWORD_LEN + 1];

      return(readpassphrase(prompt, buf, sizeof(buf), RPP_ECHO_OFF));
}

static void handler(int s)
{

      signo = s;
}

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