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