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;
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_NONAME;
83 continue;
84 }
85
86 /* Extract first name as canonical name */
87 for (; *p && isspace(*p); p++);
88 for (z=p; *z && !isspace(*z); z++);
89 *z = 0;
90 if (is_valid_hostname(p)) memcpy(canon, p, z-p+1);
91 }
92 __fclose_ca(f);
93 return cnt ? cnt : badfam;
94 }
95
96 struct dpc_ctx {
97 struct address *addrs;
98 char *canon;
99 int cnt;
100 };
101
102 #define RR_A 1
103 #define RR_CNAME 5
104 #define RR_AAAA 28
105
dns_parse_callback(void * c,int rr,const void * data,int len,const void * packet)106 static int dns_parse_callback(void *c, int rr, const void *data, int len, const void *packet)
107 {
108 char tmp[256];
109 struct dpc_ctx *ctx = c;
110 if (ctx->cnt >= MAXADDRS) return -1;
111 switch (rr) {
112 case RR_A:
113 if (len != 4) return -1;
114 ctx->addrs[ctx->cnt].family = AF_INET;
115 ctx->addrs[ctx->cnt].scopeid = 0;
116 memcpy(ctx->addrs[ctx->cnt++].addr, data, 4);
117 break;
118 case RR_AAAA:
119 if (len != 16) return -1;
120 ctx->addrs[ctx->cnt].family = AF_INET6;
121 ctx->addrs[ctx->cnt].scopeid = 0;
122 memcpy(ctx->addrs[ctx->cnt++].addr, data, 16);
123 break;
124 case RR_CNAME:
125 if (__dn_expand(packet, (const unsigned char *)packet + 512,
126 data, tmp, sizeof tmp) > 0 && is_valid_hostname(tmp))
127 strcpy(ctx->canon, tmp);
128 break;
129 }
130 return 0;
131 }
132
name_from_dns(struct address buf[static MAXADDRS],char canon[static256],const char * name,int family,const struct resolvconf * conf)133 static int name_from_dns(struct address buf[static MAXADDRS], char canon[static 256], const char *name, int family, const struct resolvconf *conf)
134 {
135 unsigned char qbuf[2][280], abuf[2][512];
136 const unsigned char *qp[2] = { qbuf[0], qbuf[1] };
137 unsigned char *ap[2] = { abuf[0], abuf[1] };
138 int qlens[2], alens[2];
139 int i, nq = 0;
140 struct dpc_ctx ctx = { .addrs = buf, .canon = canon };
141 static const struct { int af; int rr; } afrr[2] = {
142 { .af = AF_INET6, .rr = RR_A },
143 { .af = AF_INET, .rr = RR_AAAA },
144 };
145
146 for (i=0; i<2; i++) {
147 if (family != afrr[i].af) {
148 qlens[nq] = __res_mkquery(0, name, 1, afrr[i].rr,
149 0, 0, 0, qbuf[nq], sizeof *qbuf);
150 if (qlens[nq] == -1)
151 return EAI_NONAME;
152 nq++;
153 }
154 }
155
156 if (__res_msend_rc(nq, qp, qlens, ap, alens, sizeof *abuf, conf) < 0)
157 return EAI_SYSTEM;
158
159 for (i=0; i<nq; i++)
160 __dns_parse(abuf[i], alens[i], dns_parse_callback, &ctx);
161
162 if (ctx.cnt) return ctx.cnt;
163 if (alens[0] < 4 || (abuf[0][3] & 15) == 2) return EAI_AGAIN;
164 if ((abuf[0][3] & 15) == 0) return EAI_NONAME;
165 if ((abuf[0][3] & 15) == 3) return 0;
166 return EAI_FAIL;
167 }
168
name_from_dns_search(struct address buf[static MAXADDRS],char canon[static256],const char * name,int family)169 static int name_from_dns_search(struct address buf[static MAXADDRS], char canon[static 256], const char *name, int family)
170 {
171 char search[256];
172 struct resolvconf conf;
173 size_t l, dots;
174 char *p, *z;
175
176 if (__get_resolv_conf(&conf, search, sizeof search) < 0) return -1;
177
178 /* Count dots, suppress search when >=ndots or name ends in
179 * a dot, which is an explicit request for global scope. */
180 for (dots=l=0; name[l]; l++) if (name[l]=='.') dots++;
181 if (dots >= conf.ndots || name[l-1]=='.') *search = 0;
182
183 /* Strip final dot for canon, fail if multiple trailing dots. */
184 if (name[l-1]=='.') l--;
185 if (!l || name[l-1]=='.') return EAI_NONAME;
186
187 /* This can never happen; the caller already checked length. */
188 if (l >= 256) return EAI_NONAME;
189
190 /* Name with search domain appended is setup in canon[]. This both
191 * provides the desired default canonical name (if the requested
192 * name is not a CNAME record) and serves as a buffer for passing
193 * the full requested name to name_from_dns. */
194 memcpy(canon, name, l);
195 canon[l] = '.';
196
197 for (p=search; *p; p=z) {
198 for (; isspace(*p); p++);
199 for (z=p; *z && !isspace(*z); z++);
200 if (z==p) break;
201 if (z-p < 256 - l - 1) {
202 memcpy(canon+l+1, p, z-p);
203 canon[z-p+1+l] = 0;
204 int cnt = name_from_dns(buf, canon, canon, family, &conf);
205 if (cnt) return cnt;
206 }
207 }
208
209 canon[l] = 0;
210 return name_from_dns(buf, canon, name, family, &conf);
211 }
212
213 static const struct policy {
214 unsigned char addr[16];
215 unsigned char len, mask;
216 unsigned char prec, label;
217 } defpolicy[] = {
218 { "\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\1", 15, 0xff, 50, 0 },
219 { "\0\0\0\0\0\0\0\0\0\0\xff\xff", 11, 0xff, 35, 4 },
220 { "\x20\2", 1, 0xff, 30, 2 },
221 { "\x20\1", 3, 0xff, 5, 5 },
222 { "\xfc", 0, 0xfe, 3, 13 },
223 #if 0
224 /* These are deprecated and/or returned to the address
225 * pool, so despite the RFC, treating them as special
226 * is probably wrong. */
227 { "", 11, 0xff, 1, 3 },
228 { "\xfe\xc0", 1, 0xc0, 1, 11 },
229 { "\x3f\xfe", 1, 0xff, 1, 12 },
230 #endif
231 /* Last rule must match all addresses to stop loop. */
232 { "", 0, 0, 40, 1 },
233 };
234
policyof(const struct in6_addr * a)235 static const struct policy *policyof(const struct in6_addr *a)
236 {
237 int i;
238 for (i=0; ; i++) {
239 if (memcmp(a->s6_addr, defpolicy[i].addr, defpolicy[i].len))
240 continue;
241 if ((a->s6_addr[defpolicy[i].len] & defpolicy[i].mask)
242 != defpolicy[i].addr[defpolicy[i].len])
243 continue;
244 return defpolicy+i;
245 }
246 }
247
labelof(const struct in6_addr * a)248 static int labelof(const struct in6_addr *a)
249 {
250 return policyof(a)->label;
251 }
252
scopeof(const struct in6_addr * a)253 static int scopeof(const struct in6_addr *a)
254 {
255 if (IN6_IS_ADDR_MULTICAST(a)) return a->s6_addr[1] & 15;
256 if (IN6_IS_ADDR_LINKLOCAL(a)) return 2;
257 if (IN6_IS_ADDR_LOOPBACK(a)) return 2;
258 if (IN6_IS_ADDR_SITELOCAL(a)) return 5;
259 return 14;
260 }
261
prefixmatch(const struct in6_addr * s,const struct in6_addr * d)262 static int prefixmatch(const struct in6_addr *s, const struct in6_addr *d)
263 {
264 /* FIXME: The common prefix length should be limited to no greater
265 * than the nominal length of the prefix portion of the source
266 * address. However the definition of the source prefix length is
267 * not clear and thus this limiting is not yet implemented. */
268 unsigned i;
269 for (i=0; i<128 && !((s->s6_addr[i/8]^d->s6_addr[i/8])&(128>>(i%8))); i++);
270 return i;
271 }
272
273 #define DAS_USABLE 0x40000000
274 #define DAS_MATCHINGSCOPE 0x20000000
275 #define DAS_MATCHINGLABEL 0x10000000
276 #define DAS_PREC_SHIFT 20
277 #define DAS_SCOPE_SHIFT 16
278 #define DAS_PREFIX_SHIFT 8
279 #define DAS_ORDER_SHIFT 0
280
addrcmp(const void * _a,const void * _b)281 static int addrcmp(const void *_a, const void *_b)
282 {
283 const struct address *a = _a, *b = _b;
284 return b->sortkey - a->sortkey;
285 }
286
__lookup_name(struct address buf[static MAXADDRS],char canon[static256],const char * name,int family,int flags)287 int __lookup_name(struct address buf[static MAXADDRS], char canon[static 256], const char *name, int family, int flags)
288 {
289 int cnt = 0, i, j;
290
291 *canon = 0;
292 if (name) {
293 /* reject empty name and check len so it fits into temp bufs */
294 size_t l = strnlen(name, 255);
295 if (l-1 >= 254)
296 return EAI_NONAME;
297 memcpy(canon, name, l+1);
298 }
299
300 /* Procedurally, a request for v6 addresses with the v4-mapped
301 * flag set is like a request for unspecified family, followed
302 * by filtering of the results. */
303 if (flags & AI_V4MAPPED) {
304 if (family == AF_INET6) family = AF_UNSPEC;
305 else flags -= AI_V4MAPPED;
306 }
307
308 /* Try each backend until there's at least one result. */
309 cnt = name_from_null(buf, name, family, flags);
310 if (!cnt) cnt = name_from_numeric(buf, name, family);
311 if (!cnt && !(flags & AI_NUMERICHOST)) {
312 cnt = name_from_hosts(buf, canon, name, family);
313 if (!cnt) cnt = name_from_dns_search(buf, canon, name, family);
314 }
315 if (cnt<=0) return cnt ? cnt : EAI_NONAME;
316
317 /* Filter/transform results for v4-mapped lookup, if requested. */
318 if (flags & AI_V4MAPPED) {
319 if (!(flags & AI_ALL)) {
320 /* If any v6 results exist, remove v4 results. */
321 for (i=0; i<cnt && buf[i].family != AF_INET6; i++);
322 if (i<cnt) {
323 for (j=0; i<cnt; i++) {
324 if (buf[i].family == AF_INET6)
325 buf[j++] = buf[i];
326 }
327 cnt = i = j;
328 }
329 }
330 /* Translate any remaining v4 results to v6 */
331 for (i=0; i<cnt; i++) {
332 if (buf[i].family != AF_INET) continue;
333 memcpy(buf[i].addr+12, buf[i].addr, 4);
334 memcpy(buf[i].addr, "\0\0\0\0\0\0\0\0\0\0\xff\xff", 12);
335 buf[i].family = AF_INET6;
336 }
337 }
338
339 /* No further processing is needed if there are fewer than 2
340 * results or if there are only IPv4 results. */
341 if (cnt<2 || family==AF_INET) return cnt;
342 for (i=0; i<cnt; i++) if (buf[i].family != AF_INET) break;
343 if (i==cnt) return cnt;
344
345 int cs;
346 pthread_setcancelstate(PTHREAD_CANCEL_DISABLE, &cs);
347
348 /* The following implements a subset of RFC 3484/6724 destination
349 * address selection by generating a single 31-bit sort key for
350 * each address. Rules 3, 4, and 7 are omitted for having
351 * excessive runtime and code size cost and dubious benefit.
352 * So far the label/precedence table cannot be customized. */
353 for (i=0; i<cnt; i++) {
354 int family = buf[i].family;
355 int key = 0;
356 struct sockaddr_in6 sa6 = { 0 }, da6 = {
357 .sin6_family = AF_INET6,
358 .sin6_scope_id = buf[i].scopeid,
359 .sin6_port = 65535
360 };
361 struct sockaddr_in sa4 = { 0 }, da4 = {
362 .sin_family = AF_INET,
363 .sin_port = 65535
364 };
365 void *sa, *da;
366 socklen_t salen, dalen;
367 if (family == AF_INET6) {
368 memcpy(da6.sin6_addr.s6_addr, buf[i].addr, 16);
369 da = &da6; dalen = sizeof da6;
370 sa = &sa6; salen = sizeof sa6;
371 } else {
372 memcpy(sa6.sin6_addr.s6_addr,
373 "\0\0\0\0\0\0\0\0\0\0\xff\xff", 12);
374 memcpy(da6.sin6_addr.s6_addr+12, buf[i].addr, 4);
375 memcpy(da6.sin6_addr.s6_addr,
376 "\0\0\0\0\0\0\0\0\0\0\xff\xff", 12);
377 memcpy(da6.sin6_addr.s6_addr+12, buf[i].addr, 4);
378 memcpy(&da4.sin_addr, buf[i].addr, 4);
379 da = &da4; dalen = sizeof da4;
380 sa = &sa4; salen = sizeof sa4;
381 }
382 const struct policy *dpolicy = policyof(&da6.sin6_addr);
383 int dscope = scopeof(&da6.sin6_addr);
384 int dlabel = dpolicy->label;
385 int dprec = dpolicy->prec;
386 int prefixlen = 0;
387 int fd = socket(family, SOCK_DGRAM|SOCK_CLOEXEC, IPPROTO_UDP);
388 if (fd >= 0) {
389 if (!connect(fd, da, dalen)) {
390 key |= DAS_USABLE;
391 if (!getsockname(fd, sa, &salen)) {
392 if (family == AF_INET) memcpy(
393 sa6.sin6_addr.s6_addr+12,
394 &sa4.sin_addr, 4);
395 if (dscope == scopeof(&sa6.sin6_addr))
396 key |= DAS_MATCHINGSCOPE;
397 if (dlabel == labelof(&sa6.sin6_addr))
398 key |= DAS_MATCHINGLABEL;
399 prefixlen = prefixmatch(&sa6.sin6_addr,
400 &da6.sin6_addr);
401 }
402 }
403 close(fd);
404 }
405 key |= dprec << DAS_PREC_SHIFT;
406 key |= (15-dscope) << DAS_SCOPE_SHIFT;
407 key |= prefixlen << DAS_PREFIX_SHIFT;
408 key |= (MAXADDRS-i) << DAS_ORDER_SHIFT;
409 buf[i].sortkey = key;
410 }
411 qsort(buf, cnt, sizeof *buf, addrcmp);
412
413 pthread_setcancelstate(cs, 0);
414
415 return cnt;
416 }
417