1 /* vi: set sw=4 ts=4: */
2 /*
3 * Fake identd server.
4 *
5 * Copyright (C) 2007 Denys Vlasenko
6 *
7 * Licensed under GPLv2, see file LICENSE in this source tree.
8 */
9 //config:config FAKEIDENTD
10 //config: bool "fakeidentd (8.7 kb)"
11 //config: default y
12 //config: select FEATURE_SYSLOG
13 //config: help
14 //config: fakeidentd listens on the ident port and returns a predefined
15 //config: fake value on any query.
16
17 //applet:IF_FAKEIDENTD(APPLET(fakeidentd, BB_DIR_USR_SBIN, BB_SUID_DROP))
18
19 //kbuild:lib-$(CONFIG_FAKEIDENTD) += isrv_identd.o isrv.o
20
21 //usage:#define fakeidentd_trivial_usage
22 //usage: "[-fiw] [-b ADDR] [STRING]"
23 //usage:#define fakeidentd_full_usage "\n\n"
24 //usage: "Provide fake ident (auth) service\n"
25 //usage: "\n -f Run in foreground"
26 //usage: "\n -i Inetd mode"
27 //usage: "\n -w Inetd 'wait' mode"
28 //usage: "\n -b ADDR Bind to specified address"
29 //usage: "\n STRING Ident answer string (default: nobody)"
30
31 #include "libbb.h"
32 #include "common_bufsiz.h"
33 #include <syslog.h>
34 #include "isrv.h"
35
36 enum { TIMEOUT = 20 };
37
38 typedef struct identd_buf_t {
39 int pos;
40 char buf[64 - sizeof(int)];
41 } identd_buf_t;
42
43 #define bogouser bb_common_bufsiz1
44
new_peer(isrv_state_t * state,int fd)45 static int new_peer(isrv_state_t *state, int fd)
46 {
47 int peer;
48 identd_buf_t *buf = xzalloc(sizeof(*buf));
49
50 peer = isrv_register_peer(state, buf);
51 if (peer < 0)
52 return 0; /* failure */
53 if (isrv_register_fd(state, peer, fd) < 0)
54 return peer; /* failure, unregister peer */
55
56 ndelay_on(fd);
57 isrv_want_rd(state, fd);
58 return 0;
59 }
60
do_rd(int fd,void ** paramp)61 static int do_rd(int fd, void **paramp)
62 {
63 identd_buf_t *buf = *paramp;
64 char *cur, *p;
65 int sz;
66
67 cur = buf->buf + buf->pos;
68
69 sz = safe_read(fd, cur, sizeof(buf->buf) - 1 - buf->pos);
70
71 if (sz < 0) {
72 if (errno != EAGAIN)
73 goto term;
74 return 0; /* "session is ok" */
75 }
76
77 buf->pos += sz;
78 buf->buf[buf->pos] = '\0';
79 p = strpbrk(cur, "\r\n");
80 if (p)
81 *p = '\0';
82 if (!p && sz)
83 return 0; /* "session is ok" */
84
85 /* Terminate session. If we are in server mode, then
86 * fd is still in nonblocking mode - we never block here */
87 if (fd == 0)
88 fd++; /* inetd mode? then write to fd 1 */
89 fdprintf(fd, "%s : USERID : UNIX : %s\r\n", buf->buf, bogouser);
90 /*
91 * Why bother if we are going to close fd now anyway?
92 * if (server)
93 * ndelay_off(fd);
94 */
95 term:
96 free(buf);
97 return 1; /* "terminate" */
98 }
99
do_timeout(void ** paramp UNUSED_PARAM)100 static int do_timeout(void **paramp UNUSED_PARAM)
101 {
102 return 1; /* terminate session */
103 }
104
inetd_mode(void)105 static void inetd_mode(void)
106 {
107 identd_buf_t *buf = xzalloc(sizeof(*buf));
108 /* buf->pos = 0; - xzalloc did it */
109 do
110 alarm(TIMEOUT);
111 /* Note: we do NOT want nonblocking I/O here! */
112 while (do_rd(0, (void*)&buf) == 0);
113 }
114
115 int fakeidentd_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
fakeidentd_main(int argc UNUSED_PARAM,char ** argv)116 int fakeidentd_main(int argc UNUSED_PARAM, char **argv)
117 {
118 enum {
119 OPT_foreground = 0x1,
120 OPT_inetd = 0x2,
121 OPT_inetdwait = 0x4,
122 OPT_fiw = 0x7,
123 OPT_bindaddr = 0x8,
124 };
125
126 const char *bind_address = NULL;
127 unsigned opt;
128 int fd;
129
130 setup_common_bufsiz();
131
132 opt = getopt32(argv, "fiwb:", &bind_address);
133 strcpy(bogouser, "nobody");
134 if (argv[optind])
135 strncpy(bogouser, argv[optind], COMMON_BUFSIZE - 1);
136
137 /* Daemonize if no -f and no -i and no -w */
138 if (!(opt & OPT_fiw))
139 bb_daemonize_or_rexec(0, argv);
140
141 /* Where to log in inetd modes? "Classic" inetd
142 * probably has its stderr /dev/null'ed (we need log to syslog?),
143 * but daemontools-like utilities usually expect that children
144 * log to stderr. I like daemontools more. Go their way.
145 * (Or maybe we need yet another option "log to syslog") */
146 if (!(opt & OPT_fiw) /* || (opt & OPT_syslog) */) {
147 openlog(applet_name, LOG_PID, LOG_DAEMON);
148 logmode = LOGMODE_SYSLOG;
149 }
150
151 if (opt & OPT_inetd) {
152 inetd_mode();
153 return 0;
154 }
155
156 /* Ignore closed connections when writing */
157 signal(SIGPIPE, SIG_IGN);
158
159 fd = 0;
160 if (!(opt & OPT_inetdwait)) {
161 fd = create_and_bind_stream_or_die(bind_address,
162 bb_lookup_std_port("identd", "tcp", 113));
163 xlisten(fd, 5);
164 }
165
166 isrv_run(fd, new_peer, do_rd, /*do_wr:*/ NULL, do_timeout,
167 TIMEOUT, (opt & OPT_inetdwait) ? TIMEOUT : 0);
168 return 0;
169 }
170