lookup_name.c (12253B)
1 #include <sys/socket.h> 2 #include <netinet/in.h> 3 #include <netdb.h> 4 #include <net/if.h> 5 #include <arpa/inet.h> 6 #include <ctype.h> 7 #include <stdlib.h> 8 #include <string.h> 9 #include <fcntl.h> 10 #include <unistd.h> 11 #include <pthread.h> 12 #include <errno.h> 13 #include <resolv.h> 14 #include "lookup.h" 15 #include "stdio_impl.h" 16 #include "syscall.h" 17 18 static int is_valid_hostname(const char *host) 19 { 20 const unsigned char *s; 21 if (strnlen(host, 255)-1 >= 254 || mbstowcs(0, host, 0) == -1) return 0; 22 for (s=(void *)host; *s>=0x80 || *s=='.' || *s=='-' || isalnum(*s); s++); 23 return !*s; 24 } 25 26 static int name_from_null(struct address buf[2], const char *name, int family, int flags) 27 { 28 int cnt = 0; 29 if (name) return 0; 30 if (flags & AI_PASSIVE) { 31 if (family != AF_INET6) 32 buf[cnt++] = (struct address){ .family = AF_INET }; 33 if (family != AF_INET) 34 buf[cnt++] = (struct address){ .family = AF_INET6 }; 35 } else { 36 if (family != AF_INET6) 37 buf[cnt++] = (struct address){ .family = AF_INET, .addr = { 127,0,0,1 } }; 38 if (family != AF_INET) 39 buf[cnt++] = (struct address){ .family = AF_INET6, .addr = { [15] = 1 } }; 40 } 41 return cnt; 42 } 43 44 static int name_from_numeric(struct address buf[1], const char *name, int family) 45 { 46 return __lookup_ipliteral(buf, name, family); 47 } 48 49 static int name_from_hosts(struct address buf[MAXADDRS], char canon[256], const char *name, int family) 50 { 51 char line[512]; 52 size_t l = strlen(name); 53 int cnt = 0, badfam = 0, have_canon = 0; 54 unsigned char _buf[1032]; 55 FILE _f, *f = __fopen_rb_ca("/etc/hosts", &_f, _buf, sizeof _buf); 56 if (!f) switch (errno) { 57 case ENOENT: 58 case ENOTDIR: 59 case EACCES: 60 return 0; 61 default: 62 return EAI_SYSTEM; 63 } 64 while (fgets(line, sizeof line, f) && cnt < MAXADDRS) { 65 char *p, *z; 66 67 if ((p=strchr(line, '#'))) *p++='\n', *p=0; 68 for(p=line+1; (p=strstr(p, name)) && 69 (!isspace(p[-1]) || !isspace(p[l])); p++); 70 if (!p) continue; 71 72 /* Isolate IP address to parse */ 73 for (p=line; *p && !isspace(*p); p++); 74 *p++ = 0; 75 switch (name_from_numeric(buf+cnt, line, family)) { 76 case 1: 77 cnt++; 78 break; 79 case 0: 80 continue; 81 default: 82 badfam = EAI_NODATA; 83 break; 84 } 85 86 if (have_canon) continue; 87 88 /* Extract first name as canonical name */ 89 for (; *p && isspace(*p); p++); 90 for (z=p; *z && !isspace(*z); z++); 91 *z = 0; 92 if (is_valid_hostname(p)) { 93 have_canon = 1; 94 memcpy(canon, p, z-p+1); 95 } 96 } 97 __fclose_ca(f); 98 return cnt ? cnt : badfam; 99 } 100 101 struct dpc_ctx { 102 struct address *addrs; 103 char *canon; 104 int cnt; 105 int rrtype; 106 }; 107 108 #define RR_A 1 109 #define RR_CNAME 5 110 #define RR_AAAA 28 111 112 #define ABUF_SIZE 4800 113 114 static int dns_parse_callback(void *c, int rr, const void *data, int len, const void *packet, int plen) 115 { 116 char tmp[256]; 117 int family; 118 struct dpc_ctx *ctx = c; 119 if (rr == RR_CNAME) { 120 if (__dn_expand(packet, (const unsigned char *)packet + plen, 121 data, tmp, sizeof tmp) > 0 && is_valid_hostname(tmp)) 122 strcpy(ctx->canon, tmp); 123 return 0; 124 } 125 if (ctx->cnt >= MAXADDRS) return 0; 126 if (rr != ctx->rrtype) return 0; 127 switch (rr) { 128 case RR_A: 129 if (len != 4) return -1; 130 family = AF_INET; 131 break; 132 case RR_AAAA: 133 if (len != 16) return -1; 134 family = AF_INET6; 135 break; 136 } 137 ctx->addrs[ctx->cnt].family = family; 138 ctx->addrs[ctx->cnt].scopeid = 0; 139 memcpy(ctx->addrs[ctx->cnt++].addr, data, len); 140 return 0; 141 } 142 143 static int name_from_dns(struct address buf[MAXADDRS], char canon[256], const char *name, int family, const struct resolvconf *conf) 144 { 145 unsigned char qbuf[2][280], abuf[2][ABUF_SIZE]; 146 const unsigned char *qp[2] = { qbuf[0], qbuf[1] }; 147 unsigned char *ap[2] = { abuf[0], abuf[1] }; 148 int qlens[2], alens[2], qtypes[2]; 149 int i, nq = 0; 150 struct dpc_ctx ctx = { .addrs = buf, .canon = canon }; 151 static const struct { int af; int rr; } afrr[2] = { 152 { .af = AF_INET6, .rr = RR_A }, 153 { .af = AF_INET, .rr = RR_AAAA }, 154 }; 155 156 for (i=0; i<2; i++) { 157 if (family != afrr[i].af) { 158 qlens[nq] = __res_mkquery(0, name, 1, afrr[i].rr, 159 0, 0, 0, qbuf[nq], sizeof *qbuf); 160 if (qlens[nq] == -1) 161 return 0; 162 qtypes[nq] = afrr[i].rr; 163 qbuf[nq][3] = 0; /* don't need AD flag */ 164 /* Ensure query IDs are distinct. */ 165 if (nq && qbuf[nq][0] == qbuf[0][0]) 166 qbuf[nq][0]++; 167 nq++; 168 } 169 } 170 171 if (__res_msend_rc(nq, qp, qlens, ap, alens, sizeof *abuf, conf) < 0) 172 return EAI_SYSTEM; 173 174 for (i=0; i<nq; i++) { 175 if (alens[i] < 4 || (abuf[i][3] & 15) == 2) return EAI_AGAIN; 176 if ((abuf[i][3] & 15) == 3) return 0; 177 if ((abuf[i][3] & 15) != 0) return EAI_FAIL; 178 } 179 180 for (i=nq-1; i>=0; i--) { 181 ctx.rrtype = qtypes[i]; 182 if (alens[i] > sizeof(abuf[i])) alens[i] = sizeof abuf[i]; 183 __dns_parse(abuf[i], alens[i], dns_parse_callback, &ctx); 184 } 185 186 if (ctx.cnt) return ctx.cnt; 187 return EAI_NODATA; 188 } 189 190 static int name_from_dns_search(struct address buf[MAXADDRS], char canon[256], const char *name, int family) 191 { 192 char search[256]; 193 struct resolvconf conf; 194 size_t l, dots; 195 char *p, *z; 196 197 if (__get_resolv_conf(&conf, search, sizeof search) < 0) return -1; 198 199 /* Count dots, suppress search when >=ndots or name ends in 200 * a dot, which is an explicit request for global scope. */ 201 for (dots=l=0; name[l]; l++) if (name[l]=='.') dots++; 202 if (dots >= conf.ndots || name[l-1]=='.') *search = 0; 203 204 /* Strip final dot for canon, fail if multiple trailing dots. */ 205 if (name[l-1]=='.') l--; 206 if (!l || name[l-1]=='.') return EAI_NONAME; 207 208 /* This can never happen; the caller already checked length. */ 209 if (l >= 256) return EAI_NONAME; 210 211 /* Name with search domain appended is setup in canon[]. This both 212 * provides the desired default canonical name (if the requested 213 * name is not a CNAME record) and serves as a buffer for passing 214 * the full requested name to name_from_dns. */ 215 memcpy(canon, name, l); 216 canon[l] = '.'; 217 218 for (p=search; *p; p=z) { 219 for (; isspace(*p); p++); 220 for (z=p; *z && !isspace(*z); z++); 221 if (z==p) break; 222 if (z-p < 256 - l - 1) { 223 memcpy(canon+l+1, p, z-p); 224 canon[z-p+1+l] = 0; 225 int cnt = name_from_dns(buf, canon, canon, family, &conf); 226 if (cnt) return cnt; 227 } 228 } 229 230 canon[l] = 0; 231 return name_from_dns(buf, canon, name, family, &conf); 232 } 233 234 static const struct policy { 235 unsigned char addr[16]; 236 unsigned char len, mask; 237 unsigned char prec, label; 238 } defpolicy[] = { 239 { "\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\1", 15, 0xff, 50, 0 }, 240 { "\0\0\0\0\0\0\0\0\0\0\xff\xff", 11, 0xff, 35, 4 }, 241 { "\x20\2", 1, 0xff, 30, 2 }, 242 { "\x20\1", 3, 0xff, 5, 5 }, 243 { "\xfc", 0, 0xfe, 3, 13 }, 244 #if 0 245 /* These are deprecated and/or returned to the address 246 * pool, so despite the RFC, treating them as special 247 * is probably wrong. */ 248 { "", 11, 0xff, 1, 3 }, 249 { "\xfe\xc0", 1, 0xc0, 1, 11 }, 250 { "\x3f\xfe", 1, 0xff, 1, 12 }, 251 #endif 252 /* Last rule must match all addresses to stop loop. */ 253 { "", 0, 0, 40, 1 }, 254 }; 255 256 static const struct policy *policyof(const struct in6_addr *a) 257 { 258 int i; 259 for (i=0; ; i++) { 260 if (memcmp(a->s6_addr, defpolicy[i].addr, defpolicy[i].len)) 261 continue; 262 if ((a->s6_addr[defpolicy[i].len] & defpolicy[i].mask) 263 != defpolicy[i].addr[defpolicy[i].len]) 264 continue; 265 return defpolicy+i; 266 } 267 } 268 269 static int labelof(const struct in6_addr *a) 270 { 271 return policyof(a)->label; 272 } 273 274 static int scopeof(const struct in6_addr *a) 275 { 276 if (IN6_IS_ADDR_MULTICAST(a)) return a->s6_addr[1] & 15; 277 if (IN6_IS_ADDR_LINKLOCAL(a)) return 2; 278 if (IN6_IS_ADDR_LOOPBACK(a)) return 2; 279 if (IN6_IS_ADDR_SITELOCAL(a)) return 5; 280 return 14; 281 } 282 283 static int prefixmatch(const struct in6_addr *s, const struct in6_addr *d) 284 { 285 /* FIXME: The common prefix length should be limited to no greater 286 * than the nominal length of the prefix portion of the source 287 * address. However the definition of the source prefix length is 288 * not clear and thus this limiting is not yet implemented. */ 289 unsigned i; 290 for (i=0; i<128 && !((s->s6_addr[i/8]^d->s6_addr[i/8])&(128>>(i%8))); i++); 291 return i; 292 } 293 294 #define DAS_USABLE 0x40000000 295 #define DAS_MATCHINGSCOPE 0x20000000 296 #define DAS_MATCHINGLABEL 0x10000000 297 #define DAS_PREC_SHIFT 20 298 #define DAS_SCOPE_SHIFT 16 299 #define DAS_PREFIX_SHIFT 8 300 #define DAS_ORDER_SHIFT 0 301 302 static int addrcmp(const void *_a, const void *_b) 303 { 304 const struct address *a = _a, *b = _b; 305 return b->sortkey - a->sortkey; 306 } 307 308 int __lookup_name(struct address buf[MAXADDRS], char canon[256], const char *name, int family, int flags) 309 { 310 int cnt = 0, i, j; 311 312 *canon = 0; 313 if (name) { 314 /* reject empty name and check len so it fits into temp bufs */ 315 size_t l = strnlen(name, 255); 316 if (l-1 >= 254) 317 return EAI_NONAME; 318 memcpy(canon, name, l+1); 319 } 320 321 /* Procedurally, a request for v6 addresses with the v4-mapped 322 * flag set is like a request for unspecified family, followed 323 * by filtering of the results. */ 324 if (flags & AI_V4MAPPED) { 325 if (family == AF_INET6) family = AF_UNSPEC; 326 else flags -= AI_V4MAPPED; 327 } 328 329 /* Try each backend until there's at least one result. */ 330 cnt = name_from_null(buf, name, family, flags); 331 if (!cnt) cnt = name_from_numeric(buf, name, family); 332 if (!cnt && !(flags & AI_NUMERICHOST)) { 333 cnt = name_from_hosts(buf, canon, name, family); 334 if (!cnt) cnt = name_from_dns_search(buf, canon, name, family); 335 } 336 if (cnt<=0) return cnt ? cnt : EAI_NONAME; 337 338 /* Filter/transform results for v4-mapped lookup, if requested. */ 339 if (flags & AI_V4MAPPED) { 340 if (!(flags & AI_ALL)) { 341 /* If any v6 results exist, remove v4 results. */ 342 for (i=0; i<cnt && buf[i].family != AF_INET6; i++); 343 if (i<cnt) { 344 for (j=0; i<cnt; i++) { 345 if (buf[i].family == AF_INET6) 346 buf[j++] = buf[i]; 347 } 348 cnt = i = j; 349 } 350 } 351 /* Translate any remaining v4 results to v6 */ 352 for (i=0; i<cnt; i++) { 353 if (buf[i].family != AF_INET) continue; 354 memcpy(buf[i].addr+12, buf[i].addr, 4); 355 memcpy(buf[i].addr, "\0\0\0\0\0\0\0\0\0\0\xff\xff", 12); 356 buf[i].family = AF_INET6; 357 } 358 } 359 360 /* No further processing is needed if there are fewer than 2 361 * results or if there are only IPv4 results. */ 362 if (cnt<2 || family==AF_INET) return cnt; 363 for (i=0; i<cnt; i++) if (buf[i].family != AF_INET) break; 364 if (i==cnt) return cnt; 365 366 int cs; 367 pthread_setcancelstate(PTHREAD_CANCEL_DISABLE, &cs); 368 369 /* The following implements a subset of RFC 3484/6724 destination 370 * address selection by generating a single 31-bit sort key for 371 * each address. Rules 3, 4, and 7 are omitted for having 372 * excessive runtime and code size cost and dubious benefit. 373 * So far the label/precedence table cannot be customized. */ 374 for (i=0; i<cnt; i++) { 375 int family = buf[i].family; 376 int key = 0; 377 struct sockaddr_in6 sa6 = { 0 }, da6 = { 378 .sin6_family = AF_INET6, 379 .sin6_scope_id = buf[i].scopeid, 380 .sin6_port = 65535 381 }; 382 struct sockaddr_in sa4 = { 0 }, da4 = { 383 .sin_family = AF_INET, 384 .sin_port = 65535 385 }; 386 void *sa, *da; 387 socklen_t salen, dalen; 388 if (family == AF_INET6) { 389 memcpy(da6.sin6_addr.s6_addr, buf[i].addr, 16); 390 da = &da6; dalen = sizeof da6; 391 sa = &sa6; salen = sizeof sa6; 392 } else { 393 memcpy(sa6.sin6_addr.s6_addr, 394 "\0\0\0\0\0\0\0\0\0\0\xff\xff", 12); 395 memcpy(da6.sin6_addr.s6_addr+12, buf[i].addr, 4); 396 memcpy(da6.sin6_addr.s6_addr, 397 "\0\0\0\0\0\0\0\0\0\0\xff\xff", 12); 398 memcpy(da6.sin6_addr.s6_addr+12, buf[i].addr, 4); 399 memcpy(&da4.sin_addr, buf[i].addr, 4); 400 da = &da4; dalen = sizeof da4; 401 sa = &sa4; salen = sizeof sa4; 402 } 403 const struct policy *dpolicy = policyof(&da6.sin6_addr); 404 int dscope = scopeof(&da6.sin6_addr); 405 int dlabel = dpolicy->label; 406 int dprec = dpolicy->prec; 407 int prefixlen = 0; 408 int fd = socket(family, SOCK_DGRAM|SOCK_CLOEXEC, IPPROTO_UDP); 409 if (fd >= 0) { 410 if (!connect(fd, da, dalen)) { 411 key |= DAS_USABLE; 412 if (!getsockname(fd, sa, &salen)) { 413 if (family == AF_INET) memcpy( 414 sa6.sin6_addr.s6_addr+12, 415 &sa4.sin_addr, 4); 416 if (dscope == scopeof(&sa6.sin6_addr)) 417 key |= DAS_MATCHINGSCOPE; 418 if (dlabel == labelof(&sa6.sin6_addr)) 419 key |= DAS_MATCHINGLABEL; 420 prefixlen = prefixmatch(&sa6.sin6_addr, 421 &da6.sin6_addr); 422 } 423 } 424 close(fd); 425 } 426 key |= dprec << DAS_PREC_SHIFT; 427 key |= (15-dscope) << DAS_SCOPE_SHIFT; 428 key |= prefixlen << DAS_PREFIX_SHIFT; 429 key |= (MAXADDRS-i) << DAS_ORDER_SHIFT; 430 buf[i].sortkey = key; 431 } 432 qsort(buf, cnt, sizeof *buf, addrcmp); 433 434 pthread_setcancelstate(cs, 0); 435 436 return cnt; 437 }