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
promptpass(char * user,char * passwd)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
plugin_init(void)124 void plugin_init(void)
125 {
126 add_options(options);
127 pap_passwd_hook = promptpass;
128 }
129