xref: /illumos-gate/usr/src/cmd/cmd-inet/usr.bin/pppd/plugins/passprompt.c (revision cbf54fed071131ba3446db06df29807d639650ab)
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