ee599f55 |
1 | /* -*-c-*- |
ee599f55 |
2 | * |
3 | * Making privileged connections |
4 | * |
5 | * (c) 2003 Straylight/Edgeware |
6 | */ |
7 | |
206212ca |
8 | /*----- Licensing notice --------------------------------------------------* |
ee599f55 |
9 | * |
9155ea97 |
10 | * This file is part of the `fwd' port forwarder. |
ee599f55 |
11 | * |
9155ea97 |
12 | * `fwd' is free software; you can redistribute it and/or modify |
ee599f55 |
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. |
206212ca |
16 | * |
9155ea97 |
17 | * `fwd' is distributed in the hope that it will be useful, |
ee599f55 |
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. |
206212ca |
21 | * |
ee599f55 |
22 | * You should have received a copy of the GNU General Public License |
9155ea97 |
23 | * along with `fwd'; if not, write to the Free Software Foundation, |
ee599f55 |
24 | * Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA. |
25 | */ |
26 | |
9155ea97 |
27 | #include "fwd.h" |
ee599f55 |
28 | |
29 | /*----- Data structures ---------------------------------------------------*/ |
30 | |
31 | typedef struct connrec { |
32 | struct in_addr peer; |
33 | unsigned port; |
34 | } connrec; |
35 | |
36 | typedef struct connrq { |
37 | int i; |
38 | struct in_addr bind; |
39 | } connrq; |
40 | |
41 | DA_DECL(connrec_v, connrec); |
42 | |
43 | /*----- Static variables --------------------------------------------------*/ |
44 | |
45 | static connrec_v cv = DA_INIT; |
46 | static conn *qhead = 0, **qtail = &qhead; |
47 | static int kidfd = -1; |
48 | static sel_file sf; |
49 | |
50 | /*----- Main code ---------------------------------------------------------*/ |
51 | |
52 | /* --- @doconn@ --- * |
53 | * |
54 | * Arguments: @const connrq *rq@ = index of connection record |
55 | * |
56 | * Returns: Connected file descriptor, or @-1@. |
57 | * |
58 | * Use: Main privileged connection thing. |
59 | */ |
60 | |
61 | static int doconn(const connrq *rq) |
62 | { |
63 | struct sockaddr_in sin_bind; |
64 | struct sockaddr_in sin_peer; |
65 | int fd; |
66 | int i; |
67 | connrec *c; |
68 | |
69 | /* --- Check the argument --- */ |
70 | |
71 | if (rq->i < 0 || rq->i >= DA_LEN(&cv)) { |
72 | errno = EINVAL; |
73 | goto fail_0; |
74 | } |
75 | c = &DA(&cv)[rq->i]; |
76 | |
77 | /* --- Make a new socket --- */ |
78 | |
79 | if ((fd = socket(PF_INET, SOCK_STREAM, 0)) < 0) |
80 | goto fail_0; |
81 | |
82 | /* --- Bind it to a low-numbered port --- */ |
83 | |
84 | memset(&sin_bind, 0, sizeof(sin_bind)); |
85 | sin_bind.sin_family = AF_INET; |
86 | sin_bind.sin_addr = rq->bind; |
87 | for (i = 1023; i >= 512; i--) { |
88 | sin_bind.sin_port = htons(i); |
89 | if (!bind(fd, (struct sockaddr *)&sin_bind, sizeof(sin_bind))) |
90 | goto bound; |
91 | if (errno != EADDRINUSE) |
92 | goto fail_1; |
93 | } |
94 | goto fail_1; |
95 | |
96 | /* --- Connect to the peer --- * |
97 | * |
98 | * We can find out whether it's connected later, so there's no need to |
99 | * distinguish these cases. |
100 | */ |
101 | |
102 | bound: |
103 | memset(&sin_peer, 0, sizeof(sin_peer)); |
104 | sin_peer.sin_family = AF_INET; |
105 | sin_peer.sin_addr = c->peer; |
106 | sin_peer.sin_port = c->port; |
107 | fdflags(fd, O_NONBLOCK, O_NONBLOCK, 0, 0); |
108 | if (connect(fd, (struct sockaddr *)&sin_peer, sizeof(sin_peer)) < 0 && |
109 | errno != EINPROGRESS) |
110 | goto fail_1; |
111 | return (fd); |
112 | |
113 | /* --- Tidy up on errors --- */ |
114 | |
115 | fail_1: |
116 | close(fd); |
117 | fail_0: |
118 | return (-1); |
119 | } |
120 | |
121 | /* --- @dochild@ --- * |
122 | * |
123 | * Arguments: @int fd@ = my file descriptor |
124 | * |
125 | * Returns: Never. |
126 | * |
127 | * Use: Child process for making privileged connections, separated |
128 | * from main process after initialization. |
129 | */ |
130 | |
131 | static void dochild(int fd) |
132 | { |
133 | int i; |
134 | connrq rq; |
135 | int nfd; |
136 | ssize_t sz; |
137 | #if defined(_SC_OPEN_MAX) |
138 | int maxfd = sysconf(_SC_OPEN_MAX); |
139 | #elif defined(OPEN_MAX) |
140 | int maxfd = OPEN_MAX; |
141 | #else |
142 | int maxfd = -1; |
143 | #endif |
144 | struct sigaction sa; |
145 | struct sigaction sa_dfl; |
146 | |
147 | /* --- Clear out unnecessary file descriptors --- */ |
148 | |
149 | if (maxfd < 0) |
150 | maxfd = 256; |
151 | for (i = 3; i < maxfd; i++) |
152 | if (i != fd) close(i); |
153 | |
154 | /* --- Close off signal handlers --- */ |
155 | |
156 | sa_dfl.sa_handler = SIG_DFL; |
157 | sigemptyset(&sa_dfl.sa_mask); |
158 | sa_dfl.sa_flags = 0; |
159 | for (i = 0; i < 256; i++) { |
160 | if (sigaction(i, 0, &sa)) |
161 | break; |
162 | if (sa.sa_handler != SIG_DFL && sa.sa_handler != SIG_IGN) |
163 | sigaction(i, &sa_dfl, 0); |
164 | } |
165 | |
166 | /* --- Main loop --- */ |
167 | |
168 | for (;;) { |
169 | sz = read(fd, &rq, sizeof(rq)); |
170 | if (!sz) |
171 | break; |
172 | if (sz < 0) |
173 | die(1, "read error in privconn child: %s", strerror(errno)); |
174 | if ((nfd = doconn(&rq)) < 0) |
175 | goto err; |
176 | i = 0; |
177 | sz = fdpass_send(fd, nfd, &i, sizeof(i)); |
178 | if (sz < 0) |
179 | goto err; |
180 | if (sz < sizeof(i)) |
181 | die(1, "short write in privconn child"); |
182 | continue; |
183 | |
184 | err: |
185 | if (write(fd, &errno, sizeof(errno)) < 0) |
186 | die(1, "write error in privconn child: %s", strerror(errno)); |
187 | } |
188 | _exit(0); |
189 | } |
190 | |
191 | /* --- @dorecvfd@ --- * |
192 | * |
193 | * Arguments: @int fd@ = file descriptor (@== kidfd@) |
194 | * @unsigned mode@ = what's happening (@== SEL_READ@) |
195 | * @void *p@ = uninteresting (@== 0@) |
196 | * |
197 | * Returns: --- |
198 | * |
199 | * Use: Receives a file descriptor from the privileged part. |
200 | */ |
201 | |
202 | void dorecvfd(int fd, unsigned mode, void *p) |
203 | { |
204 | conn *c, *cc; |
205 | ssize_t n; |
206 | int e; |
207 | |
208 | n = fdpass_recv(kidfd, &fd, &e, sizeof(e)); |
209 | if (!n) |
210 | goto close; |
211 | assert(qhead); |
212 | c = qhead; |
213 | qhead = (conn *)c->writer.next; |
214 | if (!qhead) qtail = &qhead; |
215 | if (n < 0 || (errno = e) != 0) |
216 | goto fail; |
217 | if (fd == -1) { |
218 | errno = EIO; |
219 | goto fail; |
220 | } |
221 | conn_fd(c, c->writer.s, fd, c->func, c->p); |
222 | return; |
223 | |
224 | fail: |
225 | c->func(-1, c->p); |
226 | return; |
227 | |
228 | close: |
229 | close(kidfd); |
230 | kidfd = 0; |
231 | errno = EIO; |
232 | sel_rmfile(&sf); |
233 | for (c = qhead; c; c = cc) { |
234 | cc = (conn *)c->writer.next; |
235 | c->func(-1, c->p); |
236 | } |
237 | qhead = 0; |
238 | qtail = &qhead; |
239 | return; |
240 | } |
241 | |
242 | /* --- @privconn_split@ --- * |
243 | * |
244 | * Arguments: @sel_state *s@ = select state |
245 | * |
246 | * Returns: --- |
247 | * |
248 | * Use: Splits off the privileged binding code into a separate |
249 | * process. |
250 | */ |
251 | |
252 | void privconn_split(sel_state *s) |
253 | { |
254 | pid_t kid; |
255 | int fd[2]; |
256 | |
092f3088 |
257 | if (kidfd != -1 || DA_LEN(&cv) == 0) |
ee599f55 |
258 | return; |
259 | if (socketpair(PF_UNIX, SOCK_STREAM, 0, fd) < 0) |
260 | die(1, "couldn't create privconn socketpair: %s", strerror(errno)); |
261 | kidfd = fd[0]; |
262 | if ((kid = fork()) < 0) |
263 | die(1, "couldn't fork privconn child: %s", strerror(errno)); |
264 | if (!kid) { |
265 | close(kidfd); |
266 | dochild(fd[1]); |
267 | _exit(127); |
268 | } |
269 | close(fd[1]); |
270 | fdflags(kidfd, 0, 0, FD_CLOEXEC, FD_CLOEXEC); |
271 | sel_initfile(s, &sf, kidfd, SEL_READ, dorecvfd, 0); |
272 | sel_addfile(&sf); |
273 | } |
274 | |
275 | /* --- @privconn_adddest@ --- * |
276 | * |
277 | * Arguments: @struct in_addr peer@ = address to connect to |
278 | * @unsigned port@ = port to connect to |
279 | * |
280 | * Returns: Index for this destination address, or @-1@ if not |
281 | * available. |
282 | * |
283 | * Use: Adds a valid destination for a privileged connection. |
284 | */ |
285 | |
286 | int privconn_adddest(struct in_addr peer, unsigned port) |
287 | { |
288 | int i; |
289 | struct connrec *c; |
290 | |
291 | if (kidfd != -1) |
292 | return (-1); |
293 | for (i = 0; i < DA_LEN(&cv); i++) { |
294 | c = &DA(&cv)[i]; |
295 | if (peer.s_addr == c->peer.s_addr && port == c->port) |
296 | return (i); |
297 | } |
298 | DA_ENSURE(&cv, 1); |
299 | DA_EXTEND(&cv, 1); |
300 | c = &DA(&cv)[i]; |
301 | c->peer = peer; |
302 | c->port = port; |
303 | return (i); |
304 | } |
305 | |
306 | /* --- @privconn_connect@ --- * |
307 | * |
308 | * Arguments: @conn *c@ = connection structure to fill in |
309 | * @sel_state *s@ = pointer to select state to attach to |
310 | * @int i@ = address index to connect to |
311 | * @struct in_addr bind@ = address to bind to |
312 | * @void (*func)(int, void *)@ = function to call on connect |
313 | * @void *p@ = argument for the function |
314 | * |
315 | * Returns: Zero on success, @-1@ on failure. |
316 | * |
317 | * Use: Sets up a privileged connection job. |
318 | */ |
319 | |
320 | int privconn_connect(conn *c, sel_state *s, int i, struct in_addr bind, |
321 | void (*func)(int, void *), void *p) |
322 | { |
323 | int fd; |
324 | connrq rq; |
325 | ssize_t n; |
326 | |
327 | rq.i = i; |
328 | rq.bind = bind; |
329 | if (kidfd == -1) { |
330 | if ((fd = doconn(&rq)) < 0) |
331 | return (-1); |
332 | conn_fd(c, s, fd, func, p); |
333 | return (0); |
334 | } |
335 | |
336 | n = write(kidfd, &rq, sizeof(rq)); |
337 | if (n < 0) |
338 | return (-1); |
339 | c->writer.fd = -1; |
340 | c->writer.s = s; |
341 | c->writer.next = 0; |
342 | c->func = func; |
343 | c->p = p; |
344 | *qtail = c; |
345 | qtail = (conn **)&c->writer.next; |
346 | return (0); |
347 | } |
348 | |
349 | /*----- That's all, folks -------------------------------------------------*/ |