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