84f87e82 |
1 | /* |
2 | * Encrypting tunnel for userv-ipif tunnels, actual implementation |
3 | * |
4 | * usage: |
5 | * udptunnel-forwarder <public-local-fd> <private-in-fd> <private-out-fd> |
6 | * <mtu> <keepalive> <timeout> |
7 | * <public-remote-addr> [<public-remote-port>] |
8 | * <encdec-keys-fd> <encdec-keys-write> |
9 | * <mech1> [<mech1-params> ...] |
10 | * <mech2> [<mech2-params> ...] |
11 | * '' |
12 | * |
13 | * Remote addr may '' to mean wait to receive a packet and reply to |
14 | * whereever we get a good packet from first, in which case port |
15 | * should not be specified. |
16 | * |
17 | * <enc-keys-write> is '' to mean read, anything else to mean write. |
18 | * |
19 | * Every must be numeric. There is very little argument checking. |
20 | * |
21 | * Exit status: |
22 | * SIGALARM timed out |
23 | * 0 terminated due to outbound packet stream EOF |
24 | * 4 other error |
25 | * 8 system problem |
26 | * 12 usage error |
27 | * 16 bad trouble |
28 | */ |
29 | |
30 | #include <sys/socket.h> |
31 | #include <netinet/in.h> |
32 | #include <arpa/inet.h> |
33 | #include <sys/utsname.h> |
34 | #include <sys/poll.h> |
35 | |
36 | #include <string.h> |
37 | #include <errno.h> |
38 | #include <assert.h> |
39 | #include <stdlib.h> |
40 | |
41 | #include <unistd.h> |
42 | #include <fcntl.h> |
43 | |
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44 | #include "forwarder.h" |
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45 | |
46 | #define MAXMECHS 10 |
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47 | |
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48 | static size_t buffer_size; |
49 | |
50 | static int public_local_fd, private_in_fd, private_out_fd; |
51 | static int mtu2, keepalive, timeout; |
52 | static int public_remote_specd; |
53 | static struct sockaddr_in public_remote; |
54 | static int encdec_keys_fd, encdec_keys_write; |
55 | static int n_mechs; |
56 | static const struct mechanism *mechs[MAXMECHS]; |
57 | |
58 | static struct mechdata *md_in[MAXMECHS], *md_out[MAXMECHS]; |
59 | static size_t maxprefix, maxsuffix; |
60 | |
61 | static struct buffer buf_in, buf_out; |
62 | static unsigned char *accum_buf; |
63 | static size_t accum_used, accum_avail; |
64 | |
65 | static time_t nextsendka; |
66 | |
67 | |
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68 | void random_key(void *ptr, size_t sz) { |
69 | if (encdec_keys_write) { |
70 | get_random(ptr,sz); |
71 | write_must(encdec_keys_fd,ptr,sz,"write keys datastream"); |
72 | } else { |
73 | read_must(encdec_keys_fd,ptr,sz,"read keys datastream"); |
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74 | } |
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75 | } |
76 | |
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77 | |
78 | static void setnonblock(int fd, int nonblock) { |
79 | int r; |
80 | |
81 | r= fcntl(fd,F_GETFL); |
82 | if (r==-1) sysfail("fcntl F_GETFL"); |
83 | r= fcntl(fd,F_SETFL, nonblock ? r|O_NONBLOCK : r&~O_NONBLOCK); |
84 | if (r==-1) sysfail("fcntl F_SETFL"); |
85 | } |
86 | |
87 | static const struct mechanism *getarg_mech(void) { |
88 | const char *name; |
89 | const struct mechanism *mech, *const *mechlist; |
90 | |
91 | name= getarg_string(); |
92 | |
93 | for (mechlist= mechanismlists; |
94 | *mechlist; |
95 | mechlist++) |
96 | for (mech= *mechlist; mech->name; mech++) |
97 | if (!strcmp(mech->name,name)) return mech; |
98 | |
99 | fprintf(stderr,"%s: unknown mechanism: %s\n",programid,name); |
100 | exit(4); |
101 | } |
102 | |
103 | static void inbound(void) { |
104 | static int any_recvd; |
105 | |
106 | struct sockaddr_in this_saddr; |
107 | int r, i, different, this_saddrlen; |
108 | const char *emsg; |
109 | |
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110 | setnonblock(public_local_fd,1); |
111 | this_saddrlen= sizeof(this_saddr); |
112 | r= recvfrom(public_local_fd, buf_in.base, buffer_size-1, 0, |
113 | &this_saddr, &this_saddrlen); |
114 | if (!r) { diag("empty ciphertext"); return; } |
115 | |
116 | if (r<0) { |
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117 | if (errno != EAGAIN && errno != EINTR) { sysdiag("receive"); sleep(1); } |
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118 | return; |
119 | } |
120 | if (this_saddr.sin_family != AF_INET) { |
121 | fprintf(stderr,"%s: received unknown AF %lu", |
122 | programid, (unsigned long)this_saddr.sin_family); |
123 | return; |
124 | } |
125 | assert(this_saddrlen == sizeof(this_saddr)); |
126 | |
127 | buf_in.size= buffer_size; |
128 | buf_in.start= buf_in.base; |
129 | for (i=n_mechs-1; i>=0; i--) { |
130 | emsg= mechs[i]->decode(md_in[i],&buf_in); |
131 | if (emsg) { |
132 | fprintf(stderr, "%s: bad packet: %s: %s\n", programid, mechs[i]->name, emsg); |
133 | return; |
134 | } |
135 | } |
136 | |
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137 | alarm(timeout); |
138 | |
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139 | different= !public_remote_specd || |
140 | memcmp(&this_saddr,&public_remote,sizeof(this_saddr)); |
141 | |
142 | if (different) { |
143 | |
144 | if (public_remote_specd==2) { |
145 | fprintf(stderr, "%s: packet from unexpected sender %s:%lu", |
146 | programid, inet_ntoa(this_saddr.sin_addr), |
147 | (unsigned long)this_saddr.sin_port); |
148 | return; |
149 | } |
150 | |
151 | fprintf(stderr, "%s: tunnel open with peer %s:%lu", |
152 | programid, inet_ntoa(this_saddr.sin_addr), |
153 | (unsigned long)this_saddr.sin_port); |
154 | nextsendka= now(); |
155 | public_remote_specd= 1; |
156 | memcpy(&public_remote,&this_saddr,sizeof(public_remote)); |
157 | |
158 | } else if (!any_recvd) { |
159 | |
160 | diag("tunnel open"); |
161 | |
162 | } |
163 | |
164 | any_recvd= 1; |
165 | |
166 | buf_in.start[buf_in.size]= 0300; |
167 | *--buf_in.start= 0300; |
168 | buf_in.size+= 2; |
169 | |
170 | setnonblock(private_in_fd,0); |
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171 | write_must(private_in_fd, buf_in.start, buf_in.size, "write down"); |
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172 | } |
173 | |
174 | static void sendpacket(const unsigned char *message, size_t size) { |
175 | int i, r; |
176 | |
177 | buf_out.start= buf_out.base+maxprefix; |
178 | buf_out.size= size; |
179 | memcpy(buf_out.start, message, size); |
180 | |
181 | nextsendka= now() + keepalive; |
182 | |
183 | for (i=0; i<n_mechs; i++) mechs[i]->encode(md_out[i],&buf_out); |
184 | assert(public_remote_specd); |
185 | |
186 | setnonblock(public_local_fd,1); |
187 | for (;;) { |
188 | r= sendto(public_local_fd, buf_out.start, buf_out.size, 0, |
189 | &public_remote, sizeof(public_remote)); |
190 | if (r == buf_out.size) break; |
191 | if (r >= 0) { diag("unexpected short send"); return; } |
192 | if (errno != EINTR) { sysdiag("send"); return; } |
193 | } |
194 | } |
195 | |
196 | static void outbound(void) { |
197 | int r; |
198 | unsigned char *after_eaten, *delim; |
199 | size_t this_packet; |
200 | |
201 | setnonblock(private_out_fd,1); |
202 | |
203 | for (;;) { |
204 | r= read(private_out_fd, accum_buf + accum_used, accum_avail - accum_used); |
205 | if (!r) { diag("outbound datastream closed, quitting"); exit(0); } |
206 | if (r<0) { |
207 | if (errno == EAGAIN) return; |
208 | if (errno == EINTR) continue; |
209 | } |
210 | accum_used += r; |
211 | assert(accum_used<=accum_avail); |
212 | |
213 | after_eaten= accum_buf; |
214 | while ((delim= memchr(after_eaten, 0300, accum_used))) { |
215 | this_packet= delim - after_eaten; |
216 | sendpacket(after_eaten, this_packet); |
217 | accum_used -= this_packet+1; |
218 | after_eaten = delim+1; |
219 | } |
220 | memmove(accum_buf, after_eaten, accum_used); |
221 | |
222 | if (accum_used == accum_avail) { |
223 | diag("missing interpacket delimiter in output datastream"); |
224 | accum_used= 0; |
225 | } |
226 | } |
227 | } |
228 | |
229 | int main(int argc, const char *const *const argv_in) { |
230 | const char *arg; |
231 | struct pollfd pollfds[2]; |
232 | struct utsname uname_result; |
233 | int i, polltimeout, r; |
234 | time_t tnow; |
235 | |
236 | argv= argv_in; |
237 | |
238 | if (uname(&uname_result)) { perror(PROGRAM ": uname failed"); exit(16); } |
239 | sprintf(programid, PROGRAM ": %.*s", SYS_NMLN, uname_result.nodename); |
240 | |
241 | public_local_fd= getarg_ulong(); |
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242 | private_in_fd= getarg_ulong(); |
243 | private_out_fd= getarg_ulong(); |
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244 | mtu2= getarg_ulong() * 2; |
245 | keepalive= getarg_ulong(); |
246 | timeout= getarg_ulong(); |
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247 | |
248 | arg= getarg_string(); |
249 | if (*arg) { |
250 | public_remote_specd= 1; |
251 | arg_assert(inet_aton(arg,&public_remote.sin_addr)); |
252 | public_remote.sin_port= getarg_ulong(); |
253 | } |
254 | |
255 | encdec_keys_fd= getarg_ulong(); |
256 | encdec_keys_write= !!*getarg_string(); |
257 | |
258 | maxprefix= 0; |
259 | for (i=0; i<n_mechs; i++) mechs[i]= getarg_mech(); |
260 | for (i=0; i<n_mechs; i++) mechs[i]->encsetup(&md_in[i], &maxprefix, &maxsuffix); |
261 | for (i=0; i<n_mechs; i++) mechs[i]->decsetup(&md_out[i]); |
262 | |
263 | if (maxprefix<1) maxprefix= 1; |
264 | if (maxsuffix<1) maxsuffix= 1; |
265 | buffer_size= mtu2 + maxprefix + maxsuffix; |
266 | buf_in.base= xmalloc(buffer_size); |
267 | buf_out.base= xmalloc(buffer_size); |
268 | accum_avail= mtu2 + 1; |
269 | accum_buf= xmalloc(accum_avail); |
270 | |
271 | alarm(timeout); |
272 | |
273 | pollfds[0].fd= public_local_fd; |
274 | pollfds[0].events= POLLIN; |
275 | pollfds[1].fd= private_out_fd; |
276 | for (;;) { |
277 | pollfds[1].events= public_remote_specd ? POLLIN : 0; |
278 | pollfds[0].revents= 0; |
279 | pollfds[1].revents= 0; |
280 | |
281 | if (keepalive) { |
282 | tnow= now(); |
283 | if (tnow >= nextsendka) sendpacket("\300",1); |
284 | polltimeout= (nextsendka - tnow)*1000; |
285 | } else { |
286 | polltimeout= -1; |
287 | } |
288 | |
289 | r= poll(pollfds,2,polltimeout); |
290 | if (!r) continue; |
291 | if (r==-1 && errno==EINTR) continue; |
292 | if (r==-1) sysfail("poll"); |
293 | |
294 | if (pollfds[0].revents & POLLIN) inbound(); |
295 | if (pollfds[1].revents & POLLOUT) outbound(); |
296 | } |
297 | } |