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
is_valid_hostname(const char * host)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
name_from_null(struct address buf[static2],const char * name,int family,int flags)26 static int name_from_null(struct address buf[static 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
name_from_numeric(struct address buf[static1],const char * name,int family)44 static int name_from_numeric(struct address buf[static 1], const char *name, int family)
45 {
46 return __lookup_ipliteral(buf, name, family);
47 }
48
name_from_hosts(struct address buf[static MAXADDRS],char canon[static256],const char * name,int family)49 static int name_from_hosts(struct address buf[static MAXADDRS], char canon[static 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
dns_parse_callback(void * c,int rr,const void * data,int len,const void * packet,int plen)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
name_from_dns(struct address buf[static MAXADDRS],char canon[static256],const char * name,int family,const struct resolvconf * conf)143 static int name_from_dns(struct address buf[static MAXADDRS], char canon[static 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
name_from_dns_search(struct address buf[static MAXADDRS],char canon[static256],const char * name,int family)190 static int name_from_dns_search(struct address buf[static MAXADDRS], char canon[static 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
policyof(const struct in6_addr * a)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
labelof(const struct in6_addr * a)269 static int labelof(const struct in6_addr *a)
270 {
271 return policyof(a)->label;
272 }
273
scopeof(const struct in6_addr * a)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
prefixmatch(const struct in6_addr * s,const struct in6_addr * d)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
addrcmp(const void * _a,const void * _b)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
__lookup_name(struct address buf[static MAXADDRS],char canon[static256],const char * name,int family,int flags)308 int __lookup_name(struct address buf[static MAXADDRS], char canon[static 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 }
438