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 <sys/wait.h>
14 #include <syslog.h>
15 #include "pppd.h"
16
17 char pppd_version[] = VERSION;
18
19 static char promptprog[PATH_MAX+1];
20
21 static option_t options[] = {
22 { "promptprog", o_string, promptprog,
23 "External PAP password prompting program",
24 OPT_STATIC, NULL, PATH_MAX },
25 { NULL }
26 };
27
promptpass(char * user,char * passwd)28 static int promptpass(char *user, char *passwd)
29 {
30 int p[2];
31 pid_t kid;
32 int readgood, wstat;
33 ssize_t red;
34
35 if (promptprog[0] == 0 || access(promptprog, X_OK) < 0)
36 return -1; /* sorry, can't help */
37
38 if (!passwd)
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 close(p[0]);
48 close(p[1]);
49 return 0;
50 }
51 if (!kid) {
52 /* we are the child, exec the program */
53 char *argv[5], fdstr[32];
54 sys_close();
55 closelog();
56 close(p[0]);
57 seteuid(getuid());
58 setegid(getgid());
59 argv[0] = promptprog;
60 argv[1] = user;
61 argv[2] = remote_name;
62 sprintf(fdstr, "%d", p[1]);
63 argv[3] = fdstr;
64 argv[4] = 0;
65 execv(*argv, argv);
66 _exit(127);
67 }
68
69 /* we are the parent, read the password from the pipe */
70 close(p[1]);
71 readgood = 0;
72 do {
73 red = read(p[0], passwd + readgood, MAXSECRETLEN-1 - readgood);
74 if (red == 0)
75 break;
76 if (red < 0) {
77 if (errno == EINTR)
78 continue;
79 error("Can't read secret from %s: %m", promptprog);
80 readgood = -1;
81 break;
82 }
83 readgood += red;
84 } while (readgood < MAXSECRETLEN - 1);
85 close(p[0]);
86
87 /* now wait for child to exit */
88 while (waitpid(kid, &wstat, 0) < 0) {
89 if (errno != EINTR) {
90 warn("error waiting for %s: %m", promptprog);
91 break;
92 }
93 }
94
95 if (readgood < 0)
96 return 0;
97 passwd[readgood] = 0;
98 if (!WIFEXITED(wstat))
99 warn("%s terminated abnormally", promptprog);
100 if (WEXITSTATUS(wstat))
101 warn("%s exited with code %d", promptprog, WEXITSTATUS(status));
102
103 return 1;
104 }
105
plugin_init(void)106 void plugin_init(void)
107 {
108 add_options(options);
109 pap_passwd_hook = promptpass;
110 }
111