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