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1 | /* -*-c-*- |
2 | * |
7481fc9c |
3 | * $Id: privconn.c,v 1.3 2004/04/08 01:36:25 mdw Exp $ |
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4 | * |
5 | * Making privileged connections |
6 | * |
7 | * (c) 2003 Straylight/Edgeware |
8 | */ |
9 | |
10 | /*----- Licensing notice --------------------------------------------------* |
11 | * |
12 | * This file is part of the `fw' port forwarder. |
13 | * |
14 | * `fw' is free software; you can redistribute it and/or modify |
15 | * it under the terms of the GNU General Public License as published by |
16 | * the Free Software Foundation; either version 2 of the License, or |
17 | * (at your option) any later version. |
18 | * |
19 | * `fw' is distributed in the hope that it will be useful, |
20 | * but WITHOUT ANY WARRANTY; without even the implied warranty of |
21 | * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the |
22 | * GNU General Public License for more details. |
23 | * |
24 | * You should have received a copy of the GNU General Public License |
25 | * along with `fw'; if not, write to the Free Software Foundation, |
26 | * Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA. |
27 | */ |
28 | |
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29 | /*----- Header files ------------------------------------------------------*/ |
30 | |
31 | #include <assert.h> |
32 | #include <errno.h> |
33 | #include <signal.h> |
34 | #include <string.h> |
35 | |
36 | #include <sys/types.h> |
37 | #include <unistd.h> |
38 | |
39 | #include <sys/socket.h> |
40 | #include <arpa/inet.h> |
41 | #include <netinet/in.h> |
42 | |
43 | #include <mLib/conn.h> |
44 | #include <mLib/darray.h> |
45 | #include <mLib/fdflags.h> |
46 | #include <mLib/fdpass.h> |
47 | #include <mLib/report.h> |
48 | #include <mLib/sel.h> |
49 | |
50 | #include "privconn.h" |
51 | |
52 | /*----- Data structures ---------------------------------------------------*/ |
53 | |
54 | typedef struct connrec { |
55 | struct in_addr peer; |
56 | unsigned port; |
57 | } connrec; |
58 | |
59 | typedef struct connrq { |
60 | int i; |
61 | struct in_addr bind; |
62 | } connrq; |
63 | |
64 | DA_DECL(connrec_v, connrec); |
65 | |
66 | /*----- Static variables --------------------------------------------------*/ |
67 | |
68 | static connrec_v cv = DA_INIT; |
69 | static conn *qhead = 0, **qtail = &qhead; |
70 | static int kidfd = -1; |
71 | static sel_file sf; |
72 | |
73 | /*----- Main code ---------------------------------------------------------*/ |
74 | |
75 | /* --- @doconn@ --- * |
76 | * |
77 | * Arguments: @const connrq *rq@ = index of connection record |
78 | * |
79 | * Returns: Connected file descriptor, or @-1@. |
80 | * |
81 | * Use: Main privileged connection thing. |
82 | */ |
83 | |
84 | static int doconn(const connrq *rq) |
85 | { |
86 | struct sockaddr_in sin_bind; |
87 | struct sockaddr_in sin_peer; |
88 | int fd; |
89 | int i; |
90 | connrec *c; |
91 | |
92 | /* --- Check the argument --- */ |
93 | |
94 | if (rq->i < 0 || rq->i >= DA_LEN(&cv)) { |
95 | errno = EINVAL; |
96 | goto fail_0; |
97 | } |
98 | c = &DA(&cv)[rq->i]; |
99 | |
100 | /* --- Make a new socket --- */ |
101 | |
102 | if ((fd = socket(PF_INET, SOCK_STREAM, 0)) < 0) |
103 | goto fail_0; |
104 | |
105 | /* --- Bind it to a low-numbered port --- */ |
106 | |
107 | memset(&sin_bind, 0, sizeof(sin_bind)); |
108 | sin_bind.sin_family = AF_INET; |
109 | sin_bind.sin_addr = rq->bind; |
110 | for (i = 1023; i >= 512; i--) { |
111 | sin_bind.sin_port = htons(i); |
112 | if (!bind(fd, (struct sockaddr *)&sin_bind, sizeof(sin_bind))) |
113 | goto bound; |
114 | if (errno != EADDRINUSE) |
115 | goto fail_1; |
116 | } |
117 | goto fail_1; |
118 | |
119 | /* --- Connect to the peer --- * |
120 | * |
121 | * We can find out whether it's connected later, so there's no need to |
122 | * distinguish these cases. |
123 | */ |
124 | |
125 | bound: |
126 | memset(&sin_peer, 0, sizeof(sin_peer)); |
127 | sin_peer.sin_family = AF_INET; |
128 | sin_peer.sin_addr = c->peer; |
129 | sin_peer.sin_port = c->port; |
130 | fdflags(fd, O_NONBLOCK, O_NONBLOCK, 0, 0); |
131 | if (connect(fd, (struct sockaddr *)&sin_peer, sizeof(sin_peer)) < 0 && |
132 | errno != EINPROGRESS) |
133 | goto fail_1; |
134 | return (fd); |
135 | |
136 | /* --- Tidy up on errors --- */ |
137 | |
138 | fail_1: |
139 | close(fd); |
140 | fail_0: |
141 | return (-1); |
142 | } |
143 | |
144 | /* --- @dochild@ --- * |
145 | * |
146 | * Arguments: @int fd@ = my file descriptor |
147 | * |
148 | * Returns: Never. |
149 | * |
150 | * Use: Child process for making privileged connections, separated |
151 | * from main process after initialization. |
152 | */ |
153 | |
154 | static void dochild(int fd) |
155 | { |
156 | int i; |
157 | connrq rq; |
158 | int nfd; |
159 | ssize_t sz; |
160 | #if defined(_SC_OPEN_MAX) |
161 | int maxfd = sysconf(_SC_OPEN_MAX); |
162 | #elif defined(OPEN_MAX) |
163 | int maxfd = OPEN_MAX; |
164 | #else |
165 | int maxfd = -1; |
166 | #endif |
167 | struct sigaction sa; |
168 | struct sigaction sa_dfl; |
169 | |
170 | /* --- Clear out unnecessary file descriptors --- */ |
171 | |
172 | if (maxfd < 0) |
173 | maxfd = 256; |
174 | for (i = 3; i < maxfd; i++) |
175 | if (i != fd) close(i); |
176 | |
177 | /* --- Close off signal handlers --- */ |
178 | |
179 | sa_dfl.sa_handler = SIG_DFL; |
180 | sigemptyset(&sa_dfl.sa_mask); |
181 | sa_dfl.sa_flags = 0; |
182 | for (i = 0; i < 256; i++) { |
183 | if (sigaction(i, 0, &sa)) |
184 | break; |
185 | if (sa.sa_handler != SIG_DFL && sa.sa_handler != SIG_IGN) |
186 | sigaction(i, &sa_dfl, 0); |
187 | } |
188 | |
189 | /* --- Main loop --- */ |
190 | |
191 | for (;;) { |
192 | sz = read(fd, &rq, sizeof(rq)); |
193 | if (!sz) |
194 | break; |
195 | if (sz < 0) |
196 | die(1, "read error in privconn child: %s", strerror(errno)); |
197 | if ((nfd = doconn(&rq)) < 0) |
198 | goto err; |
199 | i = 0; |
200 | sz = fdpass_send(fd, nfd, &i, sizeof(i)); |
201 | if (sz < 0) |
202 | goto err; |
203 | if (sz < sizeof(i)) |
204 | die(1, "short write in privconn child"); |
205 | continue; |
206 | |
207 | err: |
208 | if (write(fd, &errno, sizeof(errno)) < 0) |
209 | die(1, "write error in privconn child: %s", strerror(errno)); |
210 | } |
211 | _exit(0); |
212 | } |
213 | |
214 | /* --- @dorecvfd@ --- * |
215 | * |
216 | * Arguments: @int fd@ = file descriptor (@== kidfd@) |
217 | * @unsigned mode@ = what's happening (@== SEL_READ@) |
218 | * @void *p@ = uninteresting (@== 0@) |
219 | * |
220 | * Returns: --- |
221 | * |
222 | * Use: Receives a file descriptor from the privileged part. |
223 | */ |
224 | |
225 | void dorecvfd(int fd, unsigned mode, void *p) |
226 | { |
227 | conn *c, *cc; |
228 | ssize_t n; |
229 | int e; |
230 | |
231 | n = fdpass_recv(kidfd, &fd, &e, sizeof(e)); |
232 | if (!n) |
233 | goto close; |
234 | assert(qhead); |
235 | c = qhead; |
236 | qhead = (conn *)c->writer.next; |
237 | if (!qhead) qtail = &qhead; |
238 | if (n < 0 || (errno = e) != 0) |
239 | goto fail; |
240 | if (fd == -1) { |
241 | errno = EIO; |
242 | goto fail; |
243 | } |
244 | conn_fd(c, c->writer.s, fd, c->func, c->p); |
245 | return; |
246 | |
247 | fail: |
248 | c->func(-1, c->p); |
249 | return; |
250 | |
251 | close: |
252 | close(kidfd); |
253 | kidfd = 0; |
254 | errno = EIO; |
255 | sel_rmfile(&sf); |
256 | for (c = qhead; c; c = cc) { |
257 | cc = (conn *)c->writer.next; |
258 | c->func(-1, c->p); |
259 | } |
260 | qhead = 0; |
261 | qtail = &qhead; |
262 | return; |
263 | } |
264 | |
265 | /* --- @privconn_split@ --- * |
266 | * |
267 | * Arguments: @sel_state *s@ = select state |
268 | * |
269 | * Returns: --- |
270 | * |
271 | * Use: Splits off the privileged binding code into a separate |
272 | * process. |
273 | */ |
274 | |
275 | void privconn_split(sel_state *s) |
276 | { |
277 | pid_t kid; |
278 | int fd[2]; |
279 | |
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280 | if (kidfd != -1 || DA_LEN(&cv) == 0) |
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281 | return; |
282 | if (socketpair(PF_UNIX, SOCK_STREAM, 0, fd) < 0) |
283 | die(1, "couldn't create privconn socketpair: %s", strerror(errno)); |
284 | kidfd = fd[0]; |
285 | if ((kid = fork()) < 0) |
286 | die(1, "couldn't fork privconn child: %s", strerror(errno)); |
287 | if (!kid) { |
288 | close(kidfd); |
289 | dochild(fd[1]); |
290 | _exit(127); |
291 | } |
292 | close(fd[1]); |
293 | fdflags(kidfd, 0, 0, FD_CLOEXEC, FD_CLOEXEC); |
294 | sel_initfile(s, &sf, kidfd, SEL_READ, dorecvfd, 0); |
295 | sel_addfile(&sf); |
296 | } |
297 | |
298 | /* --- @privconn_adddest@ --- * |
299 | * |
300 | * Arguments: @struct in_addr peer@ = address to connect to |
301 | * @unsigned port@ = port to connect to |
302 | * |
303 | * Returns: Index for this destination address, or @-1@ if not |
304 | * available. |
305 | * |
306 | * Use: Adds a valid destination for a privileged connection. |
307 | */ |
308 | |
309 | int privconn_adddest(struct in_addr peer, unsigned port) |
310 | { |
311 | int i; |
312 | struct connrec *c; |
313 | |
314 | if (kidfd != -1) |
315 | return (-1); |
316 | for (i = 0; i < DA_LEN(&cv); i++) { |
317 | c = &DA(&cv)[i]; |
318 | if (peer.s_addr == c->peer.s_addr && port == c->port) |
319 | return (i); |
320 | } |
321 | DA_ENSURE(&cv, 1); |
322 | DA_EXTEND(&cv, 1); |
323 | c = &DA(&cv)[i]; |
324 | c->peer = peer; |
325 | c->port = port; |
326 | return (i); |
327 | } |
328 | |
329 | /* --- @privconn_connect@ --- * |
330 | * |
331 | * Arguments: @conn *c@ = connection structure to fill in |
332 | * @sel_state *s@ = pointer to select state to attach to |
333 | * @int i@ = address index to connect to |
334 | * @struct in_addr bind@ = address to bind to |
335 | * @void (*func)(int, void *)@ = function to call on connect |
336 | * @void *p@ = argument for the function |
337 | * |
338 | * Returns: Zero on success, @-1@ on failure. |
339 | * |
340 | * Use: Sets up a privileged connection job. |
341 | */ |
342 | |
343 | int privconn_connect(conn *c, sel_state *s, int i, struct in_addr bind, |
344 | void (*func)(int, void *), void *p) |
345 | { |
346 | int fd; |
347 | connrq rq; |
348 | ssize_t n; |
349 | |
350 | rq.i = i; |
351 | rq.bind = bind; |
352 | if (kidfd == -1) { |
353 | if ((fd = doconn(&rq)) < 0) |
354 | return (-1); |
355 | conn_fd(c, s, fd, func, p); |
356 | return (0); |
357 | } |
358 | |
359 | n = write(kidfd, &rq, sizeof(rq)); |
360 | if (n < 0) |
361 | return (-1); |
362 | c->writer.fd = -1; |
363 | c->writer.s = s; |
364 | c->writer.next = 0; |
365 | c->func = func; |
366 | c->p = p; |
367 | *qtail = c; |
368 | qtail = (conn **)&c->writer.next; |
369 | return (0); |
370 | } |
371 | |
372 | /*----- That's all, folks -------------------------------------------------*/ |