readpass.c

   1 /*
   2  * Copyright (c) 2001 Markus Friedl.  All rights reserved.
   3  *
   4  * Redistribution and use in source and binary forms, with or without
   5  * modification, are permitted provided that the following conditions
   6  * are met:
   7  * 1. Redistributions of source code must retain the above copyright
   8  *    notice, this list of conditions and the following disclaimer.
   9  * 2. Redistributions in binary form must reproduce the above copyright
  10  *    notice, this list of conditions and the following disclaimer in the
  11  *    documentation and/or other materials provided with the distribution.
  12  *
  13  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
  14  * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
  15  * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
  16  * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
  17  * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
  18  * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
  19  * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
  20  * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
  21  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
  22  * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  23  */
  24
  25 #include "includes.h"
  26 RCSID("$OpenBSD: readpass.c,v 1.31 2004/10/29 22:53:56 djm Exp $");
  27
  28 #include "xmalloc.h"
  29 #include "misc.h"
  30 #include "pathnames.h"
  31 #include "log.h"
  32 #include "ssh.h"
  33
  34 static char *
  35 ssh_askpass(char *askpass, const char *msg)
  36 {
  37         pid_t pid;
  38         size_t len;
  39         char *pass;
  40         int p[2], status, ret;
  41         char buf[1024];
  42
  43         if (fflush(stdout) != 0)
  44                 error("ssh_askpass: fflush: %s", strerror(errno));
  45         if (askpass == NULL)
  46                 fatal("internal error: askpass undefined");
  47         if (pipe(p) < 0) {
  48                 error("ssh_askpass: pipe: %s", strerror(errno));
  49                 return NULL;
  50         }
  51         if ((pid = fork()) < 0) {
  52                 error("ssh_askpass: fork: %s", strerror(errno));
  53                 return NULL;
  54         }
  55         if (pid == 0) {
  56                 seteuid(getuid());
  57                 setuid(getuid());
  58                 close(p[0]);
  59                 if (dup2(p[1], STDOUT_FILENO) < 0)
  60                         fatal("ssh_askpass: dup2: %s", strerror(errno));
  61                 execlp(askpass, askpass, msg, (char *) 0);
  62                 fatal("ssh_askpass: exec(%s): %s", askpass, strerror(errno));
  63         }
  64         close(p[1]);
  65
  66         len = ret = 0;
  67         do {
  68                 ret = read(p[0], buf + len, sizeof(buf) - 1 - len);
  69                 if (ret == -1 && errno == EINTR)
  70                         continue;
  71                 if (ret <= 0)
  72                         break;
  73                 len += ret;
  74         } while (sizeof(buf) - 1 - len > 0);
  75         buf[len] = '\0';
  76
  77         close(p[0]);
  78         while (waitpid(pid, &status, 0) < 0)
  79                 if (errno != EINTR)
  80                         break;
  81
  82         if (!WIFEXITED(status) || WEXITSTATUS(status) != 0) {
  83                 memset(buf, 0, sizeof(buf));
  84                 return NULL;
  85         }
  86
  87         buf[strcspn(buf, "\r\n")] = '\0';
  88         pass = xstrdup(buf);
  89         memset(buf, 0, sizeof(buf));
  90         return pass;
  91 }
  92
  93 /*
  94  * Reads a passphrase from /dev/tty with echo turned off/on.  Returns the
  95  * passphrase (allocated with xmalloc).  Exits if EOF is encountered. If
  96  * RP_ALLOW_STDIN is set, the passphrase will be read from stdin if no
  97  * tty is available
  98  */
  99 char *
 100 read_passphrase(const char *prompt, int flags)
 101 {
 102         char *askpass = NULL, *ret, buf[1024];
 103         int rppflags, use_askpass = 0, ttyfd;
 104
 105         rppflags = (flags & RP_ECHO) ? RPP_ECHO_ON : RPP_ECHO_OFF;
 106         if (flags & RP_USE_ASKPASS)
 107                 use_askpass = 1;
 108         else if (flags & RP_ALLOW_STDIN) {
 109                 if (!isatty(STDIN_FILENO))
 110                         use_askpass = 1;
 111         } else {
 112                 rppflags |= RPP_REQUIRE_TTY;
 113                 ttyfd = open(_PATH_TTY, O_RDWR);
 114                 if (ttyfd >= 0)
 115                         close(ttyfd);
 116                 else
 117                         use_askpass = 1;
 118         }
 119
 120         if ((flags & RP_USE_ASKPASS) && getenv("DISPLAY") == NULL)
 121                 return (flags & RP_ALLOW_EOF) ? NULL : xstrdup("");
 122
 123         if (use_askpass && getenv("DISPLAY")) {
 124                 if (getenv(SSH_ASKPASS_ENV))
 125                         askpass = getenv(SSH_ASKPASS_ENV);
 126                 else
 127                         askpass = _PATH_SSH_ASKPASS_DEFAULT;
 128                 if ((ret = ssh_askpass(askpass, prompt)) == NULL)
 129                         if (!(flags & RP_ALLOW_EOF))
 130                                 return xstrdup("");
 131                 return ret;
 132         }
 133
 134         if (readpassphrase(prompt, buf, sizeof buf, rppflags) == NULL) {
 135                 if (flags & RP_ALLOW_EOF)
 136                         return NULL;
 137                 return xstrdup("");
 138         }
 139
 140         ret = xstrdup(buf);
 141         memset(buf, 'x', sizeof buf);
 142         return ret;
 143 }
 144
 145 int
 146 ask_permission(const char *fmt, ...)
 147 {
 148         va_list args;
 149         char *p, prompt[1024];
 150         int allowed = 0;
 151
 152         va_start(args, fmt);
 153         vsnprintf(prompt, sizeof(prompt), fmt, args);
 154         va_end(args);
 155
 156         p = read_passphrase(prompt, RP_USE_ASKPASS|RP_ALLOW_EOF);
 157         if (p != NULL) {
 158                 /*
 159                  * Accept empty responses and responses consisting
 160                  * of the word "yes" as affirmative.
 161                  */
 162                 if (*p == '\0' || *p == '\n' ||
 163                     strcasecmp(p, "yes") == 0)
 164                         allowed = 1;
 165                 xfree(p);
 166         }
 167
 168         return (allowed);
 169 }