| 1 | /* UDP send/receive module for secnet */ |
| 2 | |
| 3 | /* This module enables sites to communicate by sending UDP |
| 4 | * packets. When an instance of the module is created we can |
| 5 | * optionally bind to a particular local IP address (not implemented |
| 6 | * yet). |
| 7 | * |
| 8 | * Packets are offered to registered receivers in turn. Once one |
| 9 | * accepts it, it isn't offered to any more. */ |
| 10 | |
| 11 | #include "secnet.h" |
| 12 | #include <stdio.h> |
| 13 | #include <unistd.h> |
| 14 | #include <fcntl.h> |
| 15 | #include <string.h> |
| 16 | #include <errno.h> |
| 17 | #include <sys/socket.h> |
| 18 | #include <sys/wait.h> |
| 19 | #include <netinet/in.h> |
| 20 | #include <arpa/inet.h> |
| 21 | #include "util.h" |
| 22 | #include "magic.h" |
| 23 | #include "unaligned.h" |
| 24 | #include "ipaddr.h" |
| 25 | #include "magic.h" |
| 26 | |
| 27 | static beforepoll_fn udp_beforepoll; |
| 28 | static afterpoll_fn udp_afterpoll; |
| 29 | static comm_request_notify_fn request_notify; |
| 30 | static comm_release_notify_fn release_notify; |
| 31 | static comm_sendmsg_fn udp_sendmsg; |
| 32 | |
| 33 | struct notify_list { |
| 34 | comm_notify_fn *fn; |
| 35 | void *state; |
| 36 | struct notify_list *next; |
| 37 | }; |
| 38 | |
| 39 | struct udp { |
| 40 | closure_t cl; |
| 41 | struct comm_if ops; |
| 42 | struct cloc loc; |
| 43 | union iaddr addr; |
| 44 | int fd; |
| 45 | string_t authbind; |
| 46 | struct buffer_if *rbuf; |
| 47 | struct notify_list *notify; |
| 48 | bool_t use_proxy; |
| 49 | union iaddr proxy; |
| 50 | }; |
| 51 | |
| 52 | static const char *addr_to_string(void *commst, const struct comm_addr *ca) { |
| 53 | struct udp *st=commst; |
| 54 | static char sbuf[100]; |
| 55 | |
| 56 | snprintf(sbuf, sizeof(sbuf), "udp:%s-%s", |
| 57 | iaddr_to_string(&st->addr), iaddr_to_string(&ca->ia)); |
| 58 | return sbuf; |
| 59 | } |
| 60 | |
| 61 | static int udp_beforepoll(void *state, struct pollfd *fds, int *nfds_io, |
| 62 | int *timeout_io) |
| 63 | { |
| 64 | struct udp *st=state; |
| 65 | if (*nfds_io<1) { |
| 66 | *nfds_io=1; |
| 67 | return ERANGE; |
| 68 | } |
| 69 | *nfds_io=1; |
| 70 | fds->fd=st->fd; |
| 71 | fds->events=POLLIN; |
| 72 | return 0; |
| 73 | } |
| 74 | |
| 75 | static void udp_afterpoll(void *state, struct pollfd *fds, int nfds) |
| 76 | { |
| 77 | struct udp *st=state; |
| 78 | union iaddr from; |
| 79 | socklen_t fromlen; |
| 80 | struct notify_list *n; |
| 81 | bool_t done; |
| 82 | int rv; |
| 83 | |
| 84 | if (nfds && (fds->revents & POLLIN)) { |
| 85 | do { |
| 86 | fromlen=sizeof(from); |
| 87 | BUF_ASSERT_FREE(st->rbuf); |
| 88 | BUF_ALLOC(st->rbuf,"udp_afterpoll"); |
| 89 | buffer_init(st->rbuf,calculate_max_start_pad()); |
| 90 | rv=recvfrom(st->fd, st->rbuf->start, |
| 91 | buf_remaining_space(st->rbuf), |
| 92 | 0, &from.sa, &fromlen); |
| 93 | if (rv>0) { |
| 94 | st->rbuf->size=rv; |
| 95 | if (st->use_proxy) { |
| 96 | /* Check that the packet came from our poxy server; |
| 97 | we shouldn't be contacted directly by anybody else |
| 98 | (since they can trivially forge source addresses) */ |
| 99 | if (!iaddr_equal(&from,&st->proxy)) { |
| 100 | Message(M_INFO,"udp: received packet that's not " |
| 101 | "from the proxy\n"); |
| 102 | BUF_FREE(st->rbuf); |
| 103 | continue; |
| 104 | } |
| 105 | /* proxy protocol supports ipv4 transport only */ |
| 106 | from.sa.sa_family=AF_INET; |
| 107 | memcpy(&from.sin.sin_addr,buf_unprepend(st->rbuf,4),4); |
| 108 | buf_unprepend(st->rbuf,2); |
| 109 | memcpy(&from.sin.sin_port,buf_unprepend(st->rbuf,2),2); |
| 110 | } |
| 111 | struct comm_addr ca; |
| 112 | ca.comm=&st->ops; |
| 113 | ca.ia=from; |
| 114 | done=False; |
| 115 | for (n=st->notify; n; n=n->next) { |
| 116 | if (n->fn(n->state, st->rbuf, &ca)) { |
| 117 | done=True; |
| 118 | break; |
| 119 | } |
| 120 | } |
| 121 | if (!done) { |
| 122 | uint32_t msgtype; |
| 123 | if (st->rbuf->size>12 /* prevents traffic amplification */ |
| 124 | && ((msgtype=get_uint32(st->rbuf->start+8)) |
| 125 | != LABEL_NAK)) { |
| 126 | uint32_t source,dest; |
| 127 | /* Manufacture and send NAK packet */ |
| 128 | source=get_uint32(st->rbuf->start); /* Us */ |
| 129 | dest=get_uint32(st->rbuf->start+4); /* Them */ |
| 130 | send_nak(&ca,source,dest,msgtype,st->rbuf,"unwanted"); |
| 131 | } |
| 132 | BUF_FREE(st->rbuf); |
| 133 | } |
| 134 | BUF_ASSERT_FREE(st->rbuf); |
| 135 | } else { |
| 136 | BUF_FREE(st->rbuf); |
| 137 | } |
| 138 | } while (rv>=0); |
| 139 | } |
| 140 | } |
| 141 | |
| 142 | static void request_notify(void *commst, void *nst, comm_notify_fn *fn) |
| 143 | { |
| 144 | struct udp *st=commst; |
| 145 | struct notify_list *n; |
| 146 | |
| 147 | n=safe_malloc(sizeof(*n),"request_notify"); |
| 148 | n->fn=fn; |
| 149 | n->state=nst; |
| 150 | n->next=st->notify; |
| 151 | st->notify=n; |
| 152 | } |
| 153 | |
| 154 | static void release_notify(void *commst, void *nst, comm_notify_fn *fn) |
| 155 | { |
| 156 | struct udp *st=commst; |
| 157 | struct notify_list *n, **p, *t; |
| 158 | |
| 159 | /* XXX untested */ |
| 160 | p=&st->notify; |
| 161 | for (n=st->notify; n; ) |
| 162 | { |
| 163 | if (n->state==nst && n->fn==fn) { |
| 164 | t=n; |
| 165 | *p=n->next; |
| 166 | n=n->next; |
| 167 | free(t); |
| 168 | } else { |
| 169 | p=&n->next; |
| 170 | n=n->next; |
| 171 | } |
| 172 | } |
| 173 | } |
| 174 | |
| 175 | static bool_t udp_sendmsg(void *commst, struct buffer_if *buf, |
| 176 | const struct comm_addr *dest) |
| 177 | { |
| 178 | struct udp *st=commst; |
| 179 | uint8_t *sa; |
| 180 | |
| 181 | if (st->use_proxy) { |
| 182 | sa=buf_prepend(buf,8); |
| 183 | if (dest->ia.sa.sa_family != AF_INET) { |
| 184 | Message(M_INFO, |
| 185 | "udp: proxy means dropping outgoing non-IPv4 packet to %s\n", |
| 186 | iaddr_to_string(&dest->ia)); |
| 187 | return False; |
| 188 | } |
| 189 | memcpy(sa,&dest->ia.sin.sin_addr,4); |
| 190 | memset(sa+4,0,4); |
| 191 | memcpy(sa+6,&dest->ia.sin.sin_port,2); |
| 192 | sendto(st->fd,sa,buf->size+8,0,&st->proxy.sa, |
| 193 | iaddr_socklen(&st->proxy)); |
| 194 | buf_unprepend(buf,8); |
| 195 | } else { |
| 196 | sendto(st->fd, buf->start, buf->size, 0, |
| 197 | &dest->ia.sa, iaddr_socklen(&dest->ia)); |
| 198 | } |
| 199 | |
| 200 | return True; |
| 201 | } |
| 202 | |
| 203 | static void udp_phase_hook(void *sst, uint32_t new_phase) |
| 204 | { |
| 205 | struct udp *st=sst; |
| 206 | union iaddr addr; |
| 207 | |
| 208 | st->fd=socket(PF_INET, SOCK_DGRAM, IPPROTO_UDP); |
| 209 | if (st->fd<0) { |
| 210 | fatal_perror("udp (%s:%d): socket",st->loc.file,st->loc.line); |
| 211 | } |
| 212 | if (fcntl(st->fd, F_SETFL, fcntl(st->fd, F_GETFL)|O_NONBLOCK)==-1) { |
| 213 | fatal_perror("udp (%s:%d): fcntl(set O_NONBLOCK)", |
| 214 | st->loc.file,st->loc.line); |
| 215 | } |
| 216 | setcloexec(st->fd); |
| 217 | |
| 218 | addr=st->addr; |
| 219 | if (st->authbind) { |
| 220 | pid_t c; |
| 221 | int status; |
| 222 | |
| 223 | /* XXX this fork() and waitpid() business needs to be hidden |
| 224 | in some system-specific library functions. */ |
| 225 | c=fork(); |
| 226 | if (c==-1) { |
| 227 | fatal_perror("udp_phase_hook: fork() for authbind"); |
| 228 | } |
| 229 | if (c==0) { |
| 230 | char *argv[4], addrstr[9], portstr[5]; |
| 231 | switch (addr.sa.sa_family) { |
| 232 | case AF_INET: |
| 233 | sprintf(addrstr,"%08lX",(long)addr.sin.sin_addr.s_addr); |
| 234 | sprintf(portstr,"%04X",addr.sin.sin_port); |
| 235 | break; |
| 236 | default: |
| 237 | fatal("udp (%s:%d): unsupported address family for authbind", |
| 238 | st->loc.file,st->loc.line); |
| 239 | } |
| 240 | argv[0]=st->authbind; |
| 241 | argv[1]=addrstr; |
| 242 | argv[2]=portstr; |
| 243 | argv[3]=NULL; |
| 244 | dup2(st->fd,0); |
| 245 | execvp(st->authbind,argv); |
| 246 | _exit(255); |
| 247 | } |
| 248 | while (waitpid(c,&status,0)==-1) { |
| 249 | if (errno==EINTR) continue; |
| 250 | fatal_perror("udp (%s:%d): authbind",st->loc.file,st->loc.line); |
| 251 | } |
| 252 | if (WIFSIGNALED(status)) { |
| 253 | fatal("udp (%s:%d): authbind died on signal %d",st->loc.file, |
| 254 | st->loc.line, WTERMSIG(status)); |
| 255 | } |
| 256 | if (WIFEXITED(status) && WEXITSTATUS(status)!=0) { |
| 257 | fatal("udp (%s:%d): authbind died with status %d",st->loc.file, |
| 258 | st->loc.line, WEXITSTATUS(status)); |
| 259 | } |
| 260 | } else { |
| 261 | if (bind(st->fd, &addr.sa, iaddr_socklen(&addr))!=0) { |
| 262 | fatal_perror("udp (%s:%d): bind",st->loc.file,st->loc.line); |
| 263 | } |
| 264 | } |
| 265 | |
| 266 | register_for_poll(st,udp_beforepoll,udp_afterpoll,1,"udp"); |
| 267 | } |
| 268 | |
| 269 | static list_t *udp_apply(closure_t *self, struct cloc loc, dict_t *context, |
| 270 | list_t *args) |
| 271 | { |
| 272 | struct udp *st; |
| 273 | item_t *i,*j; |
| 274 | dict_t *d; |
| 275 | list_t *l; |
| 276 | uint32_t a; |
| 277 | |
| 278 | st=safe_malloc(sizeof(*st),"udp_apply(st)"); |
| 279 | st->loc=loc; |
| 280 | st->cl.description="udp"; |
| 281 | st->cl.type=CL_COMM; |
| 282 | st->cl.apply=NULL; |
| 283 | st->cl.interface=&st->ops; |
| 284 | st->ops.st=st; |
| 285 | st->ops.request_notify=request_notify; |
| 286 | st->ops.release_notify=release_notify; |
| 287 | st->ops.sendmsg=udp_sendmsg; |
| 288 | st->ops.addr_to_string=addr_to_string; |
| 289 | st->use_proxy=False; |
| 290 | |
| 291 | i=list_elem(args,0); |
| 292 | if (!i || i->type!=t_dict) { |
| 293 | cfgfatal(st->loc,"udp","first argument must be a dictionary\n"); |
| 294 | } |
| 295 | d=i->data.dict; |
| 296 | |
| 297 | st->addr.sa.sa_family=AF_INET; |
| 298 | j=dict_find_item(d,"address",False,"udp",st->loc); |
| 299 | st->addr.sin.sin_addr.s_addr=j?string_item_to_ipaddr(j, "udp"):INADDR_ANY; |
| 300 | st->addr.sin.sin_port=dict_read_number(d,"port",True,"udp",st->loc,0); |
| 301 | st->rbuf=find_cl_if(d,"buffer",CL_BUFFER,True,"udp",st->loc); |
| 302 | st->authbind=dict_read_string(d,"authbind",False,"udp",st->loc); |
| 303 | l=dict_lookup(d,"proxy"); |
| 304 | if (l) { |
| 305 | st->use_proxy=True; |
| 306 | st->proxy.sa.sa_family=AF_INET; |
| 307 | i=list_elem(l,0); |
| 308 | if (!i || i->type!=t_string) { |
| 309 | cfgfatal(st->loc,"udp","proxy must supply ""addr"",port\n"); |
| 310 | } |
| 311 | a=string_item_to_ipaddr(i,"proxy"); |
| 312 | st->proxy.sin.sin_addr.s_addr=htonl(a); |
| 313 | i=list_elem(l,1); |
| 314 | if (!i || i->type!=t_number) { |
| 315 | cfgfatal(st->loc,"udp","proxy must supply ""addr"",port\n"); |
| 316 | } |
| 317 | st->proxy.sin.sin_port=htons(i->data.number); |
| 318 | } |
| 319 | |
| 320 | update_max_start_pad(&comm_max_start_pad, st->use_proxy ? 8 : 0); |
| 321 | |
| 322 | add_hook(PHASE_GETRESOURCES,udp_phase_hook,st); |
| 323 | |
| 324 | return new_closure(&st->cl); |
| 325 | } |
| 326 | |
| 327 | void udp_module(dict_t *dict) |
| 328 | { |
| 329 | add_closure(dict,"udp",udp_apply); |
| 330 | } |