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1 | /* -*-c-*- |
2 | * |
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3 | * $Id: privconn.c,v 1.2 2003/11/29 20:43:01 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 | |
29 | /*----- Revision history --------------------------------------------------* |
30 | * |
31 | * $Log: privconn.c,v $ |
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32 | * Revision 1.2 2003/11/29 20:43:01 mdw |
33 | * Don't do priv separation if no priv connections to make. |
34 | * |
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35 | * Revision 1.1 2003/11/29 20:36:07 mdw |
36 | * Privileged outgoing connections. |
37 | * |
38 | */ |
39 | |
40 | /*----- Header files ------------------------------------------------------*/ |
41 | |
42 | #include <assert.h> |
43 | #include <errno.h> |
44 | #include <signal.h> |
45 | #include <string.h> |
46 | |
47 | #include <sys/types.h> |
48 | #include <unistd.h> |
49 | |
50 | #include <sys/socket.h> |
51 | #include <arpa/inet.h> |
52 | #include <netinet/in.h> |
53 | |
54 | #include <mLib/conn.h> |
55 | #include <mLib/darray.h> |
56 | #include <mLib/fdflags.h> |
57 | #include <mLib/fdpass.h> |
58 | #include <mLib/report.h> |
59 | #include <mLib/sel.h> |
60 | |
61 | #include "privconn.h" |
62 | |
63 | /*----- Data structures ---------------------------------------------------*/ |
64 | |
65 | typedef struct connrec { |
66 | struct in_addr peer; |
67 | unsigned port; |
68 | } connrec; |
69 | |
70 | typedef struct connrq { |
71 | int i; |
72 | struct in_addr bind; |
73 | } connrq; |
74 | |
75 | DA_DECL(connrec_v, connrec); |
76 | |
77 | /*----- Static variables --------------------------------------------------*/ |
78 | |
79 | static connrec_v cv = DA_INIT; |
80 | static conn *qhead = 0, **qtail = &qhead; |
81 | static int kidfd = -1; |
82 | static sel_file sf; |
83 | |
84 | /*----- Main code ---------------------------------------------------------*/ |
85 | |
86 | /* --- @doconn@ --- * |
87 | * |
88 | * Arguments: @const connrq *rq@ = index of connection record |
89 | * |
90 | * Returns: Connected file descriptor, or @-1@. |
91 | * |
92 | * Use: Main privileged connection thing. |
93 | */ |
94 | |
95 | static int doconn(const connrq *rq) |
96 | { |
97 | struct sockaddr_in sin_bind; |
98 | struct sockaddr_in sin_peer; |
99 | int fd; |
100 | int i; |
101 | connrec *c; |
102 | |
103 | /* --- Check the argument --- */ |
104 | |
105 | if (rq->i < 0 || rq->i >= DA_LEN(&cv)) { |
106 | errno = EINVAL; |
107 | goto fail_0; |
108 | } |
109 | c = &DA(&cv)[rq->i]; |
110 | |
111 | /* --- Make a new socket --- */ |
112 | |
113 | if ((fd = socket(PF_INET, SOCK_STREAM, 0)) < 0) |
114 | goto fail_0; |
115 | |
116 | /* --- Bind it to a low-numbered port --- */ |
117 | |
118 | memset(&sin_bind, 0, sizeof(sin_bind)); |
119 | sin_bind.sin_family = AF_INET; |
120 | sin_bind.sin_addr = rq->bind; |
121 | for (i = 1023; i >= 512; i--) { |
122 | sin_bind.sin_port = htons(i); |
123 | if (!bind(fd, (struct sockaddr *)&sin_bind, sizeof(sin_bind))) |
124 | goto bound; |
125 | if (errno != EADDRINUSE) |
126 | goto fail_1; |
127 | } |
128 | goto fail_1; |
129 | |
130 | /* --- Connect to the peer --- * |
131 | * |
132 | * We can find out whether it's connected later, so there's no need to |
133 | * distinguish these cases. |
134 | */ |
135 | |
136 | bound: |
137 | memset(&sin_peer, 0, sizeof(sin_peer)); |
138 | sin_peer.sin_family = AF_INET; |
139 | sin_peer.sin_addr = c->peer; |
140 | sin_peer.sin_port = c->port; |
141 | fdflags(fd, O_NONBLOCK, O_NONBLOCK, 0, 0); |
142 | if (connect(fd, (struct sockaddr *)&sin_peer, sizeof(sin_peer)) < 0 && |
143 | errno != EINPROGRESS) |
144 | goto fail_1; |
145 | return (fd); |
146 | |
147 | /* --- Tidy up on errors --- */ |
148 | |
149 | fail_1: |
150 | close(fd); |
151 | fail_0: |
152 | return (-1); |
153 | } |
154 | |
155 | /* --- @dochild@ --- * |
156 | * |
157 | * Arguments: @int fd@ = my file descriptor |
158 | * |
159 | * Returns: Never. |
160 | * |
161 | * Use: Child process for making privileged connections, separated |
162 | * from main process after initialization. |
163 | */ |
164 | |
165 | static void dochild(int fd) |
166 | { |
167 | int i; |
168 | connrq rq; |
169 | int nfd; |
170 | ssize_t sz; |
171 | #if defined(_SC_OPEN_MAX) |
172 | int maxfd = sysconf(_SC_OPEN_MAX); |
173 | #elif defined(OPEN_MAX) |
174 | int maxfd = OPEN_MAX; |
175 | #else |
176 | int maxfd = -1; |
177 | #endif |
178 | struct sigaction sa; |
179 | struct sigaction sa_dfl; |
180 | |
181 | /* --- Clear out unnecessary file descriptors --- */ |
182 | |
183 | if (maxfd < 0) |
184 | maxfd = 256; |
185 | for (i = 3; i < maxfd; i++) |
186 | if (i != fd) close(i); |
187 | |
188 | /* --- Close off signal handlers --- */ |
189 | |
190 | sa_dfl.sa_handler = SIG_DFL; |
191 | sigemptyset(&sa_dfl.sa_mask); |
192 | sa_dfl.sa_flags = 0; |
193 | for (i = 0; i < 256; i++) { |
194 | if (sigaction(i, 0, &sa)) |
195 | break; |
196 | if (sa.sa_handler != SIG_DFL && sa.sa_handler != SIG_IGN) |
197 | sigaction(i, &sa_dfl, 0); |
198 | } |
199 | |
200 | /* --- Main loop --- */ |
201 | |
202 | for (;;) { |
203 | sz = read(fd, &rq, sizeof(rq)); |
204 | if (!sz) |
205 | break; |
206 | if (sz < 0) |
207 | die(1, "read error in privconn child: %s", strerror(errno)); |
208 | if ((nfd = doconn(&rq)) < 0) |
209 | goto err; |
210 | i = 0; |
211 | sz = fdpass_send(fd, nfd, &i, sizeof(i)); |
212 | if (sz < 0) |
213 | goto err; |
214 | if (sz < sizeof(i)) |
215 | die(1, "short write in privconn child"); |
216 | continue; |
217 | |
218 | err: |
219 | if (write(fd, &errno, sizeof(errno)) < 0) |
220 | die(1, "write error in privconn child: %s", strerror(errno)); |
221 | } |
222 | _exit(0); |
223 | } |
224 | |
225 | /* --- @dorecvfd@ --- * |
226 | * |
227 | * Arguments: @int fd@ = file descriptor (@== kidfd@) |
228 | * @unsigned mode@ = what's happening (@== SEL_READ@) |
229 | * @void *p@ = uninteresting (@== 0@) |
230 | * |
231 | * Returns: --- |
232 | * |
233 | * Use: Receives a file descriptor from the privileged part. |
234 | */ |
235 | |
236 | void dorecvfd(int fd, unsigned mode, void *p) |
237 | { |
238 | conn *c, *cc; |
239 | ssize_t n; |
240 | int e; |
241 | |
242 | n = fdpass_recv(kidfd, &fd, &e, sizeof(e)); |
243 | if (!n) |
244 | goto close; |
245 | assert(qhead); |
246 | c = qhead; |
247 | qhead = (conn *)c->writer.next; |
248 | if (!qhead) qtail = &qhead; |
249 | if (n < 0 || (errno = e) != 0) |
250 | goto fail; |
251 | if (fd == -1) { |
252 | errno = EIO; |
253 | goto fail; |
254 | } |
255 | conn_fd(c, c->writer.s, fd, c->func, c->p); |
256 | return; |
257 | |
258 | fail: |
259 | c->func(-1, c->p); |
260 | return; |
261 | |
262 | close: |
263 | close(kidfd); |
264 | kidfd = 0; |
265 | errno = EIO; |
266 | sel_rmfile(&sf); |
267 | for (c = qhead; c; c = cc) { |
268 | cc = (conn *)c->writer.next; |
269 | c->func(-1, c->p); |
270 | } |
271 | qhead = 0; |
272 | qtail = &qhead; |
273 | return; |
274 | } |
275 | |
276 | /* --- @privconn_split@ --- * |
277 | * |
278 | * Arguments: @sel_state *s@ = select state |
279 | * |
280 | * Returns: --- |
281 | * |
282 | * Use: Splits off the privileged binding code into a separate |
283 | * process. |
284 | */ |
285 | |
286 | void privconn_split(sel_state *s) |
287 | { |
288 | pid_t kid; |
289 | int fd[2]; |
290 | |
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291 | if (kidfd != -1 || DA_LEN(&cv) == 0) |
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292 | return; |
293 | if (socketpair(PF_UNIX, SOCK_STREAM, 0, fd) < 0) |
294 | die(1, "couldn't create privconn socketpair: %s", strerror(errno)); |
295 | kidfd = fd[0]; |
296 | if ((kid = fork()) < 0) |
297 | die(1, "couldn't fork privconn child: %s", strerror(errno)); |
298 | if (!kid) { |
299 | close(kidfd); |
300 | dochild(fd[1]); |
301 | _exit(127); |
302 | } |
303 | close(fd[1]); |
304 | fdflags(kidfd, 0, 0, FD_CLOEXEC, FD_CLOEXEC); |
305 | sel_initfile(s, &sf, kidfd, SEL_READ, dorecvfd, 0); |
306 | sel_addfile(&sf); |
307 | } |
308 | |
309 | /* --- @privconn_adddest@ --- * |
310 | * |
311 | * Arguments: @struct in_addr peer@ = address to connect to |
312 | * @unsigned port@ = port to connect to |
313 | * |
314 | * Returns: Index for this destination address, or @-1@ if not |
315 | * available. |
316 | * |
317 | * Use: Adds a valid destination for a privileged connection. |
318 | */ |
319 | |
320 | int privconn_adddest(struct in_addr peer, unsigned port) |
321 | { |
322 | int i; |
323 | struct connrec *c; |
324 | |
325 | if (kidfd != -1) |
326 | return (-1); |
327 | for (i = 0; i < DA_LEN(&cv); i++) { |
328 | c = &DA(&cv)[i]; |
329 | if (peer.s_addr == c->peer.s_addr && port == c->port) |
330 | return (i); |
331 | } |
332 | DA_ENSURE(&cv, 1); |
333 | DA_EXTEND(&cv, 1); |
334 | c = &DA(&cv)[i]; |
335 | c->peer = peer; |
336 | c->port = port; |
337 | return (i); |
338 | } |
339 | |
340 | /* --- @privconn_connect@ --- * |
341 | * |
342 | * Arguments: @conn *c@ = connection structure to fill in |
343 | * @sel_state *s@ = pointer to select state to attach to |
344 | * @int i@ = address index to connect to |
345 | * @struct in_addr bind@ = address to bind to |
346 | * @void (*func)(int, void *)@ = function to call on connect |
347 | * @void *p@ = argument for the function |
348 | * |
349 | * Returns: Zero on success, @-1@ on failure. |
350 | * |
351 | * Use: Sets up a privileged connection job. |
352 | */ |
353 | |
354 | int privconn_connect(conn *c, sel_state *s, int i, struct in_addr bind, |
355 | void (*func)(int, void *), void *p) |
356 | { |
357 | int fd; |
358 | connrq rq; |
359 | ssize_t n; |
360 | |
361 | rq.i = i; |
362 | rq.bind = bind; |
363 | if (kidfd == -1) { |
364 | if ((fd = doconn(&rq)) < 0) |
365 | return (-1); |
366 | conn_fd(c, s, fd, func, p); |
367 | return (0); |
368 | } |
369 | |
370 | n = write(kidfd, &rq, sizeof(rq)); |
371 | if (n < 0) |
372 | return (-1); |
373 | c->writer.fd = -1; |
374 | c->writer.s = s; |
375 | c->writer.next = 0; |
376 | c->func = func; |
377 | c->p = p; |
378 | *qtail = c; |
379 | qtail = (conn **)&c->writer.next; |
380 | return (0); |
381 | } |
382 | |
383 | /*----- That's all, folks -------------------------------------------------*/ |