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
17char pppd_version[] = VERSION;
18
19static char promptprog[PATH_MAX+1];
20
21static option_t options[] = {
22    { "promptprog", o_string, promptprog,
23      "External PAP password prompting program",
24      OPT_STATIC, NULL, PATH_MAX },
25    { NULL }
26};
27
28static int promptpass(char *user, char *passwd)
29{
30    int p[2];
31    pid_t kid;
32    int readgood, wstat;
33    size_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[4], 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	    error("Can't read secret from %s: %m", promptprog);
78	    readgood = -1;
79	    break;
80	}
81	readgood += red;
82    } while (readgood < MAXSECRETLEN - 1);
83    passwd[readgood] = 0;
84    close(p[0]);
85
86    /* now wait for child to exit */
87    while (waitpid(kid, &wstat, 0) < 0) {
88	if (errno != EINTR) {
89	    warn("error waiting for %s: %m", promptprog);
90	    break;
91	}
92    }
93
94    if (readgood < 0)
95	return 0;
96    if (!WIFEXITED(wstat))
97	warn("%s terminated abnormally", promptprog);
98    if (WEXITSTATUS(wstat))
99	warn("%s exited with code %d", promptprog, WEXITSTATUS(status));
100
101    return 1;
102}
103
104void plugin_init(void)
105{
106    add_options(options);
107    pap_passwd_hook = promptpass;
108}
109