1 /*
   2  * passprompt.c - pppd plugin to invoke an external PAP password prompter
   3  *
   4  * Copyright 1999 Paul Mackerras, Alan Curry.
   5  *
   6  *  This program is free software; you can redistribute it and/or
   7  *  modify it under the terms of the GNU General Public License
   8  *  as published by the Free Software Foundation; either version
   9  *  2 of the License, or (at your option) any later version.
  10  */
  11 
  12 /*
  13  * Copyright (c) 2018, Joyent, Inc.
  14  */
  15 
  16 #include <errno.h>
  17 #include <unistd.h>
  18 #include <fcntl.h>
  19 #include <sys/wait.h>
  20 #include <syslog.h>
  21 #include "pppd.h"
  22 
  23 static char promptprog[PATH_MAX+1];
  24 
  25 static option_t options[] = {
  26     { "promptprog", o_string, promptprog,
  27       "External PAP password prompting program",
  28       OPT_STATIC, NULL, PATH_MAX },
  29     { NULL }
  30 };
  31 
  32 static int promptpass(char *user, char *passwd)
  33 {
  34     int p[2];
  35     pid_t kid;
  36     int readgood, wstat;
  37     int red;
  38 
  39     if (promptprog[0] == 0 || access(promptprog, X_OK) < 0)
  40         return -1;      /* sorry, can't help */
  41 
  42     /* This occurs when we're probed for the ability to supply a password */
  43     if (user != NULL && passwd == NULL)
  44         return 1;
  45 
  46     if (pipe(p)) {
  47         warn("Can't make a pipe for %s", promptprog);
  48         return 0;
  49     }
  50     if ((kid = fork()) == (pid_t) -1) {
  51         warn("Can't fork to run %s", promptprog);
  52         (void) close(p[0]);
  53         (void) close(p[1]);
  54         return 0;
  55     }
  56     if (kid == (pid_t)0) {
  57         /* we are the child, exec the program */
  58         char *argv[5], fdstr[32];
  59 
  60         sys_close();
  61         closelog();
  62         if (detached && p[1] <= 2) {
  63             (void) dup2(p[1], 3);
  64             p[1] = 3;
  65         }
  66         (void) close(p[0]);
  67         if (detached) {
  68             red = open("/etc/ppp/prompt-errors", O_WRONLY | O_APPEND | O_CREAT,
  69                 0600);
  70             (void) dup2(red, 1);
  71             (void) dup2(red, 2);
  72         }
  73         (void) seteuid(getuid());
  74         (void) setegid(getgid());
  75         argv[0] = promptprog;
  76         argv[1] = user == NULL ? "" : user;
  77         argv[2] = remote_name;
  78         (void) slprintf(fdstr, sizeof (fdstr), "%d", p[1]);
  79         argv[3] = fdstr;
  80         argv[4] = NULL;
  81         (void) execv(*argv, argv);
  82         _exit(127);
  83     }
  84 
  85     /* we are the parent, read the password from the pipe */
  86     (void) close(p[1]);
  87     readgood = 0;
  88     do {
  89         red = read(p[0], passwd + readgood, MAXSECRETLEN-1 - readgood);
  90         if (red == 0)
  91             break;
  92         if (red < 0) {
  93             if (errno == EINTR)
  94                 continue;
  95             error("Can't read secret from %s: %m", promptprog);
  96             readgood = -1;
  97             break;
  98         }
  99         readgood += red;
 100     } while (readgood < MAXSECRETLEN - 1);
 101     passwd[readgood] = 0;
 102     (void) close(p[0]);
 103 
 104     /* now wait for child to exit */
 105     while (waitpid(kid, &wstat, 0) < 0) {
 106         if (errno != EINTR) {
 107             warn("error waiting for %s: %m", promptprog);
 108             break;
 109         }
 110     }
 111 
 112     if (readgood < 0)
 113         return 0;
 114     if (readgood > 0 && passwd[--readgood] == '\n')
 115         passwd[readgood] = '\0';
 116     if (!WIFEXITED(wstat))
 117         warn("%s terminated abnormally", promptprog);
 118     if (WEXITSTATUS(wstat) != 0)
 119         warn("%s exited with code %d", promptprog, WEXITSTATUS(wstat));
 120 
 121     return 1;
 122 }
 123 
 124 void plugin_init(void)
 125 {
 126     add_options(options);
 127     pap_passwd_hook = promptpass;
 128 }