| 1 | /* -*-c-*- |
| 2 | * |
| 3 | * Discover the owner of a connection (Linux version) |
| 4 | * |
| 5 | * (c) 2012 Straylight/Edgeware |
| 6 | */ |
| 7 | |
| 8 | /*----- Licensing notice --------------------------------------------------* |
| 9 | * |
| 10 | * This file is part of Yet Another Ident Daemon (YAID). |
| 11 | * |
| 12 | * YAID 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 | * YAID 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 YAID; if not, write to the Free Software Foundation, |
| 24 | * Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA. |
| 25 | */ |
| 26 | |
| 27 | /*----- Header files ------------------------------------------------------*/ |
| 28 | |
| 29 | #include "yaid.h" |
| 30 | |
| 31 | #include <linux/netlink.h> |
| 32 | #include <linux/rtnetlink.h> |
| 33 | |
| 34 | /*----- Static variables --------------------------------------------------*/ |
| 35 | |
| 36 | static FILE *natfp; /* File handle for NAT table */ |
| 37 | |
| 38 | /*----- Address-type operations -------------------------------------------*/ |
| 39 | |
| 40 | struct addrops_sys { |
| 41 | const char *procfile; |
| 42 | const char *nfl3name; |
| 43 | int (*parseaddr)(char **, union addr *); |
| 44 | }; |
| 45 | |
| 46 | #define PROCFILE_IPV4 "/proc/net/tcp" |
| 47 | #define NFL3NAME_IPV4 "ipv4" |
| 48 | |
| 49 | static int parseaddr_ipv4(char **pp, union addr *a) |
| 50 | { a->ipv4.s_addr = strtoul(*pp, pp, 16); return (0); } |
| 51 | |
| 52 | #define PROCFILE_IPV6 "/proc/net/tcp6" |
| 53 | #define NFL3NAME_IPV6 "ipv6" |
| 54 | |
| 55 | static int parseaddr_ipv6(char **pp, union addr *a) |
| 56 | { |
| 57 | int i, j; |
| 58 | unsigned long y; |
| 59 | char *p = *pp; |
| 60 | unsigned x; |
| 61 | |
| 62 | /* The format is byteswapped in a really annoying way. */ |
| 63 | for (i = 0; i < 4; i++) { |
| 64 | y = 0; |
| 65 | for (j = 0; j < 8; j++) { |
| 66 | if ('0' <= *p && *p <= '9') x = *p - '0'; |
| 67 | else if ('a' <= *p && *p <= 'f') x = *p - 'a' + 10; |
| 68 | else if ('A' <= *p && *p <= 'F') x = *p - 'A' + 10; |
| 69 | else return (-1); |
| 70 | y = (y << 4) | x; |
| 71 | p++; |
| 72 | } |
| 73 | a->ipv6.s6_addr32[i] = y; |
| 74 | } |
| 75 | *pp = p; |
| 76 | return (0); |
| 77 | } |
| 78 | |
| 79 | #define DEFOPSYS(ty, TY) \ |
| 80 | const struct addrops_sys addrops_sys_##ty = { \ |
| 81 | PROCFILE_##TY, NFL3NAME_##TY, parseaddr_##ty \ |
| 82 | }; |
| 83 | ADDRTYPES(DEFOPSYS) |
| 84 | #undef DEFOPSYS |
| 85 | |
| 86 | /*----- Main code ---------------------------------------------------------*/ |
| 87 | |
| 88 | /* Store in A the default gateway address for the given address family. |
| 89 | * Return zero on success, or nonzero on error. |
| 90 | */ |
| 91 | static int get_default_gw(int af, union addr *a) |
| 92 | { |
| 93 | int fd; |
| 94 | char buf[32768]; |
| 95 | struct nlmsghdr *nlmsg; |
| 96 | struct rtgenmsg *rtgen; |
| 97 | const struct rtattr *rta; |
| 98 | const struct rtmsg *rtm; |
| 99 | ssize_t n, nn; |
| 100 | int rc = -1; |
| 101 | static unsigned long seq = 0x48b4aec4; |
| 102 | |
| 103 | /* Open a netlink socket for interrogating the kernel. */ |
| 104 | if ((fd = socket(AF_NETLINK, SOCK_DGRAM, NETLINK_ROUTE)) < 0) |
| 105 | die(1, "failed to create netlink socket: %s", strerror(errno)); |
| 106 | |
| 107 | /* We want to read the routing table. There doesn't seem to be a good way |
| 108 | * to do this without just crawling through the whole thing. |
| 109 | */ |
| 110 | nlmsg = (struct nlmsghdr *)buf; |
| 111 | assert(NLMSG_SPACE(sizeof(*rtgen)) < sizeof(buf)); |
| 112 | nlmsg->nlmsg_len = NLMSG_LENGTH(sizeof(*rtgen)); |
| 113 | nlmsg->nlmsg_type = RTM_GETROUTE; |
| 114 | nlmsg->nlmsg_flags = NLM_F_REQUEST | NLM_F_ROOT; |
| 115 | nlmsg->nlmsg_seq = ++seq; |
| 116 | nlmsg->nlmsg_pid = 0; |
| 117 | |
| 118 | rtgen = (struct rtgenmsg *)NLMSG_DATA(nlmsg); |
| 119 | rtgen->rtgen_family = af; |
| 120 | |
| 121 | if (write(fd, nlmsg, nlmsg->nlmsg_len) < 0) |
| 122 | die(1, "failed to send RTM_GETROUTE request: %s", strerror(errno)); |
| 123 | |
| 124 | /* Now we try to parse the answer. */ |
| 125 | for (;;) { |
| 126 | |
| 127 | /* Not finished yet, so read another chunk of answer. */ |
| 128 | if ((n = read(fd, buf, sizeof(buf))) < 0) |
| 129 | die(1, "failed to read RTM_GETROUTE response: %s", strerror(errno)); |
| 130 | |
| 131 | /* Start at the beginning of the response. */ |
| 132 | nlmsg = (struct nlmsghdr *)buf; |
| 133 | |
| 134 | /* Make sure this looks plausible. The precise rules don't appear to be |
| 135 | * documented, so it seems advisable to fail messily if my understanding |
| 136 | * is wrong. |
| 137 | */ |
| 138 | if (nlmsg->nlmsg_seq != seq) continue; |
| 139 | assert(nlmsg->nlmsg_flags & NLM_F_MULTI); |
| 140 | |
| 141 | /* Work through all of the individual routes. */ |
| 142 | for (; NLMSG_OK(nlmsg, n); nlmsg = NLMSG_NEXT(nlmsg, n)) { |
| 143 | if (nlmsg->nlmsg_type == NLMSG_DONE) goto done; |
| 144 | if (nlmsg->nlmsg_type != RTM_NEWROUTE) continue; |
| 145 | rtm = (const struct rtmsg *)NLMSG_DATA(nlmsg); |
| 146 | |
| 147 | /* If this record doesn't look interesting then skip it. */ |
| 148 | if (rtm->rtm_family != af || /* wrong address family */ |
| 149 | rtm->rtm_dst_len > 0 || /* specific destination */ |
| 150 | rtm->rtm_src_len > 0 || /* specific source */ |
| 151 | rtm->rtm_type != RTN_UNICAST || /* not for unicast */ |
| 152 | rtm->rtm_scope != RT_SCOPE_UNIVERSE || /* wrong scope */ |
| 153 | rtm->rtm_tos != 0) /* specific type of service */ |
| 154 | continue; |
| 155 | |
| 156 | /* Trundle through the attributes and find the gateway address. */ |
| 157 | for (rta = RTM_RTA(rtm), nn = RTM_PAYLOAD(nlmsg); |
| 158 | RTA_OK(rta, nn); rta = RTA_NEXT(rta, nn)) { |
| 159 | |
| 160 | /* Got one. We're all done. Except that we should carry on reading |
| 161 | * to the end, or something bad will happen. |
| 162 | */ |
| 163 | if (rta->rta_type == RTA_GATEWAY) { |
| 164 | assert(RTA_PAYLOAD(rta) <= sizeof(*a)); |
| 165 | memcpy(a, RTA_DATA(rta), RTA_PAYLOAD(rta)); |
| 166 | rc = 0; |
| 167 | } |
| 168 | } |
| 169 | } |
| 170 | } |
| 171 | |
| 172 | done: |
| 173 | close(fd); |
| 174 | return (rc); |
| 175 | } |
| 176 | |
| 177 | /* Find out who is responsible for the connection described in the query Q. |
| 178 | * Write the answer to Q. Errors are logged and reported via the query |
| 179 | * structure. |
| 180 | */ |
| 181 | void identify(struct query *q) |
| 182 | { |
| 183 | FILE *fp = 0; |
| 184 | dstr d = DSTR_INIT; |
| 185 | char *p, *pp; |
| 186 | struct socket s[4]; |
| 187 | int i; |
| 188 | int gwp = 0; |
| 189 | unsigned fl; |
| 190 | #define F_SADDR 1u |
| 191 | #define F_SPORT 2u |
| 192 | #define F_DADDR 4u |
| 193 | #define F_DPORT 8u |
| 194 | #define F_ALL (F_SADDR | F_SPORT | F_DADDR | F_DPORT) |
| 195 | #define F_ESTAB 16u |
| 196 | uid_t uid; |
| 197 | enum { LOC, REM, ST, UID, NFIELD }; |
| 198 | int f, ff[NFIELD]; |
| 199 | |
| 200 | /* If we have a default gateway, and it matches the remote address then |
| 201 | * this may be a proxy connection from our NAT, so remember this, and don't |
| 202 | * inspect the remote addresses in the TCP tables. |
| 203 | */ |
| 204 | if (!get_default_gw(q->ao->af, &s[0].addr) && |
| 205 | q->ao->addreq(&s[0].addr, &q->s[R].addr)) |
| 206 | gwp = 1; |
| 207 | |
| 208 | /* Open the relevant TCP connection table. */ |
| 209 | if ((fp = fopen(q->ao->sys->procfile, "r")) == 0) { |
| 210 | logmsg(q, LOG_ERR, "failed to open `%s' for reading: %s", |
| 211 | q->ao->sys->procfile, strerror(errno)); |
| 212 | goto err_unk; |
| 213 | } |
| 214 | |
| 215 | /* Initially, PP points into a string containing whitespace-separated |
| 216 | * fields. Point P to the next field, null-terminate it, and advance PP |
| 217 | * so that we can read the next field in the next call. |
| 218 | */ |
| 219 | #define NEXTFIELD do { \ |
| 220 | for (p = pp; isspace((unsigned char)*p); p++); \ |
| 221 | for (pp = p; *pp && !isspace((unsigned char)*pp); pp++); \ |
| 222 | if (*pp) *pp++ = 0; \ |
| 223 | } while (0) |
| 224 | |
| 225 | /* Read the header line from the file. */ |
| 226 | if (dstr_putline(&d, fp) == EOF) { |
| 227 | logmsg(q, LOG_ERR, "failed to read header line from `%s': %s", |
| 228 | q->ao->sys->procfile, |
| 229 | ferror(fp) ? strerror(errno) : "unexpected EOF"); |
| 230 | goto err_unk; |
| 231 | } |
| 232 | |
| 233 | /* Now scan the header line to identify which columns the various |
| 234 | * interesting fields are in. Store these in the map `ff'. Problems: |
| 235 | * `tx_queue rx_queue' and `tr tm->when' are both really single columns in |
| 236 | * disguise; and the remote address column has a different heading |
| 237 | * depending on which address family we're using. Rather than dispatch, |
| 238 | * just recognize both of them. |
| 239 | */ |
| 240 | for (i = 0; i < NFIELD; i++) ff[i] = -1; |
| 241 | pp = d.buf; |
| 242 | for (f = 0;; f++) { |
| 243 | NEXTFIELD; if (!*p) break; |
| 244 | if (strcmp(p, "local_address") == 0) |
| 245 | ff[LOC] = f; |
| 246 | else if (strcmp(p, "rem_address") == 0 || |
| 247 | strcmp(p, "remote_address") == 0) |
| 248 | ff[REM] = f; |
| 249 | else if (strcmp(p, "uid") == 0) |
| 250 | ff[UID] = f; |
| 251 | else if (strcmp(p, "st") == 0) |
| 252 | ff[ST] = f; |
| 253 | else if (strcmp(p, "rx_queue") == 0 || |
| 254 | strcmp(p, "tm->when") == 0) |
| 255 | f--; |
| 256 | } |
| 257 | |
| 258 | /* Make sure that we found all of the fields we actually want. */ |
| 259 | for (i = 0; i < NFIELD; i++) { |
| 260 | if (ff[i] < 0) { |
| 261 | logmsg(q, LOG_ERR, "failed to find required fields in `%s'", |
| 262 | q->ao->sys->procfile); |
| 263 | goto err_unk; |
| 264 | } |
| 265 | } |
| 266 | |
| 267 | /* Work through the lines in the file. */ |
| 268 | for (;;) { |
| 269 | |
| 270 | /* Read a line, and prepare to scan the fields. */ |
| 271 | DRESET(&d); |
| 272 | if (dstr_putline(&d, fp) == EOF) break; |
| 273 | pp = d.buf; |
| 274 | uid = -1; |
| 275 | |
| 276 | /* Work through the fields. If an address field fails to match then we |
| 277 | * skip this record. If the state field isn't 1 (`ESTABLISHED') then |
| 278 | * skip the record. If it's the UID, then remember it: if we get all the |
| 279 | * way to the end then we've won. |
| 280 | */ |
| 281 | for (f = 0;; f++) { |
| 282 | NEXTFIELD; if (!*p) break; |
| 283 | if (f == ff[LOC]) { i = L; goto compare; } |
| 284 | else if (f == ff[REM]) { i = R; goto compare; } |
| 285 | else if (f == ff[UID]) uid = atoi(p); |
| 286 | else if (f == ff[ST]) { |
| 287 | if (strtol(p, 0, 16) != 1) goto next_row; |
| 288 | } |
| 289 | continue; |
| 290 | |
| 291 | compare: |
| 292 | /* Compare an address (in the current field) with the local or remote |
| 293 | * address in the query, as indicated by `i'. The address field looks |
| 294 | * like `ADDR:PORT', where the ADDR is in some mad format which |
| 295 | * `sys->parseaddr' knows how to unpick. If the remote address in the |
| 296 | * query is our gateway then don't check the remote address in the |
| 297 | * field (but do check the port number). |
| 298 | */ |
| 299 | if (q->ao->sys->parseaddr(&p, &s[i].addr)) goto next_row; |
| 300 | if (*p != ':') break; p++; |
| 301 | s[i].port = strtoul(p, 0, 16); |
| 302 | if ((i == R && gwp) ? |
| 303 | q->s[R].port != s[i].port : |
| 304 | !sockeq(q->ao, &q->s[i], &s[i])) |
| 305 | goto next_row; |
| 306 | } |
| 307 | |
| 308 | /* We got to the end, and everything matched. If we found a UID then |
| 309 | * we're done. If the apparent remote address is our gateway then copy |
| 310 | * the true one into the query structure. |
| 311 | */ |
| 312 | if (uid != -1) { |
| 313 | q->resp = R_UID; |
| 314 | q->u.uid = uid; |
| 315 | if (gwp) q->s[R].addr = s[i].addr; |
| 316 | goto done; |
| 317 | } |
| 318 | next_row:; |
| 319 | } |
| 320 | |
| 321 | /* We got to the end of the file and didn't find anything. */ |
| 322 | if (ferror(fp)) { |
| 323 | logmsg(q, LOG_ERR, "failed to read connection table `%s': %s", |
| 324 | q->ao->sys->procfile, strerror(errno)); |
| 325 | goto err_unk; |
| 326 | } |
| 327 | |
| 328 | /* If we opened the NAT table file, and we're using IPv4, then check to see |
| 329 | * whether we should proxy the connection. At least the addresses in this |
| 330 | * file aren't crazy. |
| 331 | */ |
| 332 | if (natfp) { |
| 333 | |
| 334 | /* Start again from the beginning. */ |
| 335 | rewind(natfp); |
| 336 | |
| 337 | /* Read a line at a time. */ |
| 338 | for (;;) { |
| 339 | |
| 340 | /* Read the line. */ |
| 341 | DRESET(&d); |
| 342 | if (dstr_putline(&d, natfp) == EOF) break; |
| 343 | pp = d.buf; |
| 344 | |
| 345 | /* Check that this is for the right protocol. */ |
| 346 | NEXTFIELD; if (!*p) break; |
| 347 | if (strcmp(p, q->ao->sys->nfl3name)) continue; |
| 348 | NEXTFIELD; if (!*p) break; |
| 349 | NEXTFIELD; if (!*p) break; |
| 350 | if (strcmp(p, "tcp") != 0) continue; |
| 351 | |
| 352 | /* Parse the other fields. Each line has two src/dst pairs, for the |
| 353 | * outgoing and incoming directions. Depending on exactly what kind of |
| 354 | * NAT is in use, either the outgoing source or the incoming |
| 355 | * destination might be the client we're after. Collect all of the |
| 356 | * addresses and sort out the mess later. |
| 357 | */ |
| 358 | i = 0; |
| 359 | fl = 0; |
| 360 | for (;;) { |
| 361 | NEXTFIELD; if (!*p) break; |
| 362 | if (strcmp(p, "ESTABLISHED") == 0) |
| 363 | fl |= F_ESTAB; |
| 364 | else if (strncmp(p, "src=", 4) == 0) { |
| 365 | inet_pton(q->ao->af, p + 4, &s[i].addr); |
| 366 | fl |= F_SADDR; |
| 367 | } else if (strncmp(p, "dst=", 4) == 0) { |
| 368 | inet_pton(q->ao->af, p + 4, &s[i + 1].addr); |
| 369 | fl |= F_DADDR; |
| 370 | } else if (strncmp(p, "sport=", 6) == 0) { |
| 371 | s[i].port = atoi(p + 6); |
| 372 | fl |= F_SPORT; |
| 373 | } else if (strncmp(p, "dport=", 6) == 0) { |
| 374 | s[i + 1].port = atoi(p + 6); |
| 375 | fl |= F_DPORT; |
| 376 | } |
| 377 | if ((fl & F_ALL) == F_ALL) { |
| 378 | fl &= ~F_ALL; |
| 379 | if (i < 4) i += 2; |
| 380 | else break; |
| 381 | } |
| 382 | } |
| 383 | |
| 384 | #ifdef notdef |
| 385 | { |
| 386 | /* Print the record we found. */ |
| 387 | dstr dd = DSTR_INIT; |
| 388 | dstr_putf(&dd, "%sestab ", (fl & F_ESTAB) ? " " : "!"); |
| 389 | dputsock(&dd, q->ao, &s[0]); |
| 390 | dstr_puts(&dd, "<->"); |
| 391 | dputsock(&dd, q->ao, &s[1]); |
| 392 | dstr_puts(&dd, " | "); |
| 393 | dputsock(&dd, q->ao, &s[2]); |
| 394 | dstr_puts(&dd, "<->"); |
| 395 | dputsock(&dd, q->ao, &s[3]); |
| 396 | printf("parsed: %s\n", dd.buf); |
| 397 | dstr_destroy(&dd); |
| 398 | } |
| 399 | #endif |
| 400 | |
| 401 | /* If the connection isn't ESTABLISHED then skip it. */ |
| 402 | if (!(fl & F_ESTAB)) continue; |
| 403 | |
| 404 | /* Now we try to piece together what's going on. One of these |
| 405 | * addresses will be us. So let's just try to find it. |
| 406 | */ |
| 407 | for (i = 0; i < 4; i++) |
| 408 | if (sockeq(q->ao, &s[i], &q->s[L])) goto found_local; |
| 409 | continue; |
| 410 | |
| 411 | found_local: |
| 412 | /* So address `i' is us. In that case, we expect the other address in |
| 413 | * the same direction, and the same address in the opposite direction, |
| 414 | * to match each other and be the remote address in the query. |
| 415 | */ |
| 416 | if (!sockeq(q->ao, &s[i^1], &s[i^2]) || |
| 417 | !sockeq(q->ao, &s[i^1], &q->s[R])) |
| 418 | continue; |
| 419 | |
| 420 | /* We win. The remaining address must be the client host. We should |
| 421 | * proxy this query. |
| 422 | */ |
| 423 | q->resp = R_NAT; |
| 424 | q->u.nat = s[i^3]; |
| 425 | goto done; |
| 426 | } |
| 427 | |
| 428 | /* Reached the end of the NAT file. */ |
| 429 | if (ferror(natfp)) { |
| 430 | logmsg(q, LOG_ERR, "failed to read `/proc/net/nf_conntrack': %s", |
| 431 | strerror(errno)); |
| 432 | goto err_unk; |
| 433 | } |
| 434 | } |
| 435 | |
| 436 | #undef NEXTFIELD |
| 437 | |
| 438 | /* We didn't find a match anywhere. How unfortunate. */ |
| 439 | logmsg(q, LOG_NOTICE, "connection not found"); |
| 440 | q->resp = R_ERROR; |
| 441 | q->u.error = E_NOUSER; |
| 442 | goto done; |
| 443 | |
| 444 | err_unk: |
| 445 | /* Something went wrong and the protocol can't express what. We should |
| 446 | * have logged what the problem actually was. |
| 447 | */ |
| 448 | q->resp = R_ERROR; |
| 449 | q->u.error = E_UNKNOWN; |
| 450 | |
| 451 | done: |
| 452 | /* All done. */ |
| 453 | dstr_destroy(&d); |
| 454 | if (fp) fclose(fp); |
| 455 | } |
| 456 | |
| 457 | /* Initialize the system-specific code. */ |
| 458 | void init_sys(void) |
| 459 | { |
| 460 | if ((natfp = fopen("/proc/net/nf_conntrack", "r")) == 0 && |
| 461 | errno != ENOENT) { |
| 462 | die(1, "failed to open `/proc/net/nf_conntrack' for reading: %s", |
| 463 | strerror(errno)); |
| 464 | } |
| 465 | } |
| 466 | |
| 467 | /*----- That's all, folks -------------------------------------------------*/ |