/* * Copyright (c) 2014 Andreas Schneider * Copyright (c) 2014 Jakub Hrozek * * All rights reserved. * * Redistribution and use in source and binary forms, with or without * modification, are permitted provided that the following conditions * are met: * * 1. Redistributions of source code must retain the above copyright * notice, this list of conditions and the following disclaimer. * * 2. Redistributions in binary form must reproduce the above copyright * notice, this list of conditions and the following disclaimer in the * documentation and/or other materials provided with the distribution. * * 3. Neither the name of the author nor the names of its contributors * may be used to endorse or promote products derived from this software * without specific prior written permission. * * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF * SUCH DAMAGE. */ #include "config.h" #include #include #include #include #include #include #include #include #include #include #include #include /* GCC has printf type attribute check. */ #ifdef HAVE_ATTRIBUTE_PRINTF_FORMAT #define PRINTF_ATTRIBUTE(a,b) __attribute__ ((__format__ (__printf__, a, b))) #else #define PRINTF_ATTRIBUTE(a,b) #endif /* HAVE_ATTRIBUTE_PRINTF_FORMAT */ #ifdef HAVE_DESTRUCTOR_ATTRIBUTE #define DESTRUCTOR_ATTRIBUTE __attribute__ ((destructor)) #else #define DESTRUCTOR_ATTRIBUTE #endif /* HAVE_DESTRUCTOR_ATTRIBUTE */ #ifndef RWRAP_DEFAULT_FAKE_TTL #define RWRAP_DEFAULT_FAKE_TTL 600 #endif /* RWRAP_DEFAULT_FAKE_TTL */ #ifndef HAVE_NS_NAME_COMPRESS #define ns_name_compress dn_comp #endif enum rwrap_dbglvl_e { RWRAP_LOG_ERROR = 0, RWRAP_LOG_WARN, RWRAP_LOG_DEBUG, RWRAP_LOG_TRACE }; #ifdef NDEBUG # define RWRAP_LOG(...) #else /* NDEBUG */ static void rwrap_log(enum rwrap_dbglvl_e dbglvl, const char *func, const char *format, ...) PRINTF_ATTRIBUTE(3, 4); # define RWRAP_LOG(dbglvl, ...) rwrap_log((dbglvl), __func__, __VA_ARGS__) static void rwrap_log(enum rwrap_dbglvl_e dbglvl, const char *func, const char *format, ...) { char buffer[1024]; va_list va; const char *d; unsigned int lvl = 0; int pid = getpid(); d = getenv("RESOLV_WRAPPER_DEBUGLEVEL"); if (d != NULL) { lvl = atoi(d); } va_start(va, format); vsnprintf(buffer, sizeof(buffer), format, va); va_end(va); if (lvl >= dbglvl) { switch (dbglvl) { case RWRAP_LOG_ERROR: fprintf(stderr, "RWRAP_ERROR(%d) - %s: %s\n", pid, func, buffer); break; case RWRAP_LOG_WARN: fprintf(stderr, "RWRAP_WARN(%d) - %s: %s\n", pid, func, buffer); break; case RWRAP_LOG_DEBUG: fprintf(stderr, "RWRAP_DEBUG(%d) - %s: %s\n", pid, func, buffer); break; case RWRAP_LOG_TRACE: fprintf(stderr, "RWRAP_TRACE(%d) - %s: %s\n", pid, func, buffer); break; } } } #endif /* NDEBUG RWRAP_LOG */ #ifndef SAFE_FREE #define SAFE_FREE(x) do { if ((x) != NULL) {free(x); (x)=NULL;} } while(0) #endif #define NEXT_KEY(buf, key) do { \ (key) = (buf) ? strpbrk((buf), " \t") : NULL; \ if ((key) != NULL) { \ (key)[0] = '\0'; \ (key)++; \ } \ while ((key) != NULL \ && (isblank((int)(key)[0]))) { \ (key)++; \ } \ } while(0); #define RWRAP_MAX_RECURSION 5 /* Priority and weight can be omitted from the hosts file, but need to be part * of the output */ #define DFL_SRV_PRIO 1 #define DFL_SRV_WEIGHT 100 struct rwrap_srv_rrdata { uint16_t port; uint16_t prio; uint16_t weight; char hostname[MAXDNAME]; }; struct rwrap_soa_rrdata { uint32_t serial; uint32_t refresh; uint32_t retry; uint32_t expire; uint32_t minimum; char nameserver[MAXDNAME]; char mailbox[MAXDNAME]; }; struct rwrap_fake_rr { union fake_rrdata { struct in_addr a_rec; struct in6_addr aaaa_rec; struct rwrap_srv_rrdata srv_rec; struct rwrap_soa_rrdata soa_rec; char cname_rec[MAXDNAME]; } rrdata; char key[MAXDNAME]; int type; /* ns_t_* */ }; static void rwrap_fake_rr_init(struct rwrap_fake_rr *rr, size_t len) { size_t i; for (i = 0; i < len; i++) { rr[i].type = ns_t_invalid; } } static int rwrap_create_fake_a_rr(const char *key, const char *value, struct rwrap_fake_rr *rr) { int ok; ok = inet_pton(AF_INET, value, &rr->rrdata.a_rec); if (!ok) { RWRAP_LOG(RWRAP_LOG_ERROR, "Failed to convert [%s] to binary\n", value); return -1; } memcpy(rr->key, key, strlen(key) + 1); rr->type = ns_t_a; return 0; } static int rwrap_create_fake_aaaa_rr(const char *key, const char *value, struct rwrap_fake_rr *rr) { int ok; ok = inet_pton(AF_INET6, value, &rr->rrdata.aaaa_rec); if (!ok) { RWRAP_LOG(RWRAP_LOG_ERROR, "Failed to convert [%s] to binary\n", value); return -1; } memcpy(rr->key, key, strlen(key) + 1); rr->type = ns_t_aaaa; return 0; } static int rwrap_create_fake_srv_rr(const char *key, const char *value, struct rwrap_fake_rr *rr) { char *str_prio; char *str_weight; char *str_port; const char *hostname; /* parse the value into priority, weight, port and hostname * and check the validity */ hostname = value; NEXT_KEY(hostname, str_port); NEXT_KEY(str_port, str_prio); NEXT_KEY(str_prio, str_weight); if (str_port == NULL || hostname == NULL) { RWRAP_LOG(RWRAP_LOG_ERROR, "Malformed SRV entry [%s]\n", value); return -1; } if (str_prio) { rr->rrdata.srv_rec.prio = atoi(str_prio); } else { rr->rrdata.srv_rec.prio = DFL_SRV_PRIO; } if (str_weight) { rr->rrdata.srv_rec.weight = atoi(str_weight); } else { rr->rrdata.srv_rec.weight = DFL_SRV_WEIGHT; } rr->rrdata.srv_rec.port = atoi(str_port); memcpy(rr->rrdata.srv_rec.hostname , hostname, strlen(hostname) + 1); memcpy(rr->key, key, strlen(key) + 1); rr->type = ns_t_srv; return 0; } static int rwrap_create_fake_soa_rr(const char *key, const char *value, struct rwrap_fake_rr *rr) { const char *nameserver; char *mailbox; char *str_serial; char *str_refresh; char *str_retry; char *str_expire; char *str_minimum; /* parse the value into nameserver, mailbox, serial, refresh, * retry, expire, minimum and check the validity */ nameserver = value; NEXT_KEY(nameserver, mailbox); NEXT_KEY(mailbox, str_serial); NEXT_KEY(str_serial, str_refresh); NEXT_KEY(str_refresh, str_retry); NEXT_KEY(str_retry, str_expire); NEXT_KEY(str_expire, str_minimum); if (nameserver == NULL || mailbox == NULL || str_serial == NULL || str_refresh == NULL || str_retry == NULL || str_expire == NULL || str_minimum == NULL) { RWRAP_LOG(RWRAP_LOG_ERROR, "Malformed SOA entry [%s]\n", value); return -1; } memcpy(rr->rrdata.soa_rec.nameserver, nameserver, strlen(nameserver)+1); memcpy(rr->rrdata.soa_rec.mailbox, mailbox, strlen(mailbox)+1); rr->rrdata.soa_rec.serial = atoi(str_serial); rr->rrdata.soa_rec.refresh = atoi(str_refresh); rr->rrdata.soa_rec.retry = atoi(str_retry); rr->rrdata.soa_rec.expire = atoi(str_expire); rr->rrdata.soa_rec.minimum = atoi(str_minimum); memcpy(rr->key, key, strlen(key) + 1); rr->type = ns_t_soa; return 0; } static int rwrap_create_fake_cname_rr(const char *key, const char *value, struct rwrap_fake_rr *rr) { memcpy(rr->rrdata.cname_rec , value, strlen(value) + 1); memcpy(rr->key, key, strlen(key) + 1); rr->type = ns_t_cname; return 0; } /* Prepares a fake header with a single response. Advances header_blob */ static ssize_t rwrap_fake_header(uint8_t **header_blob, size_t remaining, size_t ancount, size_t arcount) { uint8_t *hb; HEADER *h; if (remaining < NS_HFIXEDSZ) { RWRAP_LOG(RWRAP_LOG_ERROR, "Buffer too small!\n"); return -1; } hb = *header_blob; memset(hb, 0, NS_HFIXEDSZ); h = (HEADER *) hb; h->id = res_randomid(); /* random query ID */ h->qr = 1; /* response flag */ h->rd = 1; /* recursion desired */ h->ra = 1; /* resursion available */ h->qdcount = htons(1); /* no. of questions */ h->ancount = htons(ancount); /* no. of answers */ h->arcount = htons(arcount); /* no. of add'tl records */ hb += NS_HFIXEDSZ; /* move past the header */ *header_blob = hb; return NS_HFIXEDSZ; } static ssize_t rwrap_fake_question(const char *question, uint16_t type, uint8_t **question_ptr, size_t remaining) { uint8_t *qb = *question_ptr; int n; n = ns_name_compress(question, qb, remaining, NULL, NULL); if (n < 0) { RWRAP_LOG(RWRAP_LOG_ERROR, "Failed to compress [%s]\n", question); return -1; } qb += n; remaining -= n; if (remaining < 2 * sizeof(uint16_t)) { RWRAP_LOG(RWRAP_LOG_ERROR, "Buffer too small!\n"); return -1; } NS_PUT16(type, qb); NS_PUT16(ns_c_in, qb); *question_ptr = qb; return n + 2 * sizeof(uint16_t); } static ssize_t rwrap_fake_rdata_common(uint16_t type, size_t rdata_size, const char *key, size_t remaining, uint8_t **rdata_ptr) { uint8_t *rd = *rdata_ptr; ssize_t written = 0; written = ns_name_compress(key, rd, remaining, NULL, NULL); if (written < 0) { RWRAP_LOG(RWRAP_LOG_ERROR, "Failed to compress [%s]\n", key); return -1; } rd += written; remaining -= written; if (remaining < 3 * sizeof(uint16_t) + sizeof(uint32_t)) { RWRAP_LOG(RWRAP_LOG_ERROR, "Buffer too small\n"); return -1; } NS_PUT16(type, rd); NS_PUT16(ns_c_in, rd); NS_PUT32(RWRAP_DEFAULT_FAKE_TTL, rd); NS_PUT16(rdata_size, rd); if (remaining < rdata_size) { RWRAP_LOG(RWRAP_LOG_ERROR, "Buffer too small\n"); return -1; } *rdata_ptr = rd; return written + 3 * sizeof(uint16_t) + sizeof(uint32_t) + rdata_size; } static ssize_t rwrap_fake_a(struct rwrap_fake_rr *rr, uint8_t *answer_ptr, size_t anslen) { uint8_t *a = answer_ptr; ssize_t resp_size; if (rr == NULL || rr->type != ns_t_a) { RWRAP_LOG(RWRAP_LOG_ERROR, "Malformed record, no or wrong value!\n"); return -1; } RWRAP_LOG(RWRAP_LOG_TRACE, "Adding A RR"); resp_size = rwrap_fake_rdata_common(ns_t_a, sizeof(struct in_addr), rr->key, anslen, &a); if (resp_size < 0) { return -1; } memcpy(a, &rr->rrdata.a_rec, sizeof(struct in_addr)); return resp_size; } static ssize_t rwrap_fake_aaaa(struct rwrap_fake_rr *rr, uint8_t *answer, size_t anslen) { uint8_t *a = answer; ssize_t resp_size; if (rr == NULL || rr->type != ns_t_aaaa) { RWRAP_LOG(RWRAP_LOG_ERROR, "Malformed record, no or wrong value!\n"); return -1; } RWRAP_LOG(RWRAP_LOG_TRACE, "Adding AAAA RR"); resp_size = rwrap_fake_rdata_common(ns_t_aaaa, sizeof(struct in6_addr), rr->key, anslen, &a); if (resp_size < 0) { return -1; } memcpy(a, &rr->rrdata.aaaa_rec, sizeof(struct in6_addr)); return resp_size; } static ssize_t rwrap_fake_srv(struct rwrap_fake_rr *rr, uint8_t *answer, size_t anslen) { uint8_t *a = answer; ssize_t resp_size; size_t rdata_size; unsigned char hostname_compressed[MAXDNAME]; ssize_t compressed_len; if (rr == NULL || rr->type != ns_t_srv) { RWRAP_LOG(RWRAP_LOG_ERROR, "Malformed record, no or wrong value!\n"); return -1; } RWRAP_LOG(RWRAP_LOG_TRACE, "Adding SRV RR"); rdata_size = 3 * sizeof(uint16_t); /* Prepare the data to write */ compressed_len = ns_name_compress(rr->rrdata.srv_rec.hostname, hostname_compressed, MAXDNAME, NULL, NULL); if (compressed_len < 0) { return -1; } rdata_size += compressed_len; resp_size = rwrap_fake_rdata_common(ns_t_srv, rdata_size, rr->key, anslen, &a); if (resp_size < 0) { return -1; } NS_PUT16(rr->rrdata.srv_rec.prio, a); NS_PUT16(rr->rrdata.srv_rec.weight, a); NS_PUT16(rr->rrdata.srv_rec.port, a); memcpy(a, hostname_compressed, compressed_len); return resp_size; } static ssize_t rwrap_fake_soa(struct rwrap_fake_rr *rr, uint8_t *answer, size_t anslen) { uint8_t *a = answer; ssize_t resp_size; size_t rdata_size; unsigned char nameser_compressed[MAXDNAME]; ssize_t compressed_ns_len; unsigned char mailbox_compressed[MAXDNAME]; ssize_t compressed_mb_len; if (rr == NULL || rr->type != ns_t_soa) { RWRAP_LOG(RWRAP_LOG_ERROR, "Malformed record, no or wrong value!\n"); return -1; } RWRAP_LOG(RWRAP_LOG_TRACE, "Adding SOA RR"); rdata_size = 5 * sizeof(uint16_t); compressed_ns_len = ns_name_compress(rr->rrdata.soa_rec.nameserver, nameser_compressed, MAXDNAME, NULL, NULL); if (compressed_ns_len < 0) { return -1; } rdata_size += compressed_ns_len; compressed_mb_len = ns_name_compress(rr->rrdata.soa_rec.mailbox, mailbox_compressed, MAXDNAME, NULL, NULL); if (compressed_mb_len < 0) { return -1; } rdata_size += compressed_mb_len; resp_size = rwrap_fake_rdata_common(ns_t_soa, rdata_size, rr->key, anslen, &a); if (resp_size < 0) { return -1; } memcpy(a, nameser_compressed, compressed_ns_len); a += compressed_ns_len; memcpy(a, mailbox_compressed, compressed_mb_len); a += compressed_mb_len; NS_PUT32(rr->rrdata.soa_rec.serial, a); NS_PUT32(rr->rrdata.soa_rec.refresh, a); NS_PUT32(rr->rrdata.soa_rec.retry, a); NS_PUT32(rr->rrdata.soa_rec.expire, a); NS_PUT32(rr->rrdata.soa_rec.minimum, a); return resp_size; } static ssize_t rwrap_fake_cname(struct rwrap_fake_rr *rr, uint8_t *answer, size_t anslen) { uint8_t *a = answer; ssize_t resp_size; unsigned char hostname_compressed[MAXDNAME]; ssize_t rdata_size; if (rr == NULL || rr->type != ns_t_cname) { RWRAP_LOG(RWRAP_LOG_ERROR, "Malformed record, no or wrong value!\n"); return -1; } RWRAP_LOG(RWRAP_LOG_TRACE, "Adding CNAME RR"); /* Prepare the data to write */ rdata_size = ns_name_compress(rr->rrdata.cname_rec, hostname_compressed, MAXDNAME, NULL, NULL); if (rdata_size < 0) { return -1; } resp_size = rwrap_fake_rdata_common(ns_t_cname, rdata_size, rr->key, anslen, &a); if (resp_size < 0) { return -1; } memcpy(a, hostname_compressed, rdata_size); return resp_size; } #define RESOLV_MATCH(line, name) \ (strncmp(line, name, sizeof(name) - 1) == 0 && \ (line[sizeof(name) - 1] == ' ' || \ line[sizeof(name) - 1] == '\t')) #define TYPE_MATCH(type, ns_type, rec_type, str_type, key, query) \ ((type) == (ns_type) && \ (strncmp((rec_type), (str_type), sizeof(str_type)) == 0) && \ (strcasecmp(key, query)) == 0) static int rwrap_get_record(const char *hostfile, unsigned recursion, const char *query, int type, struct rwrap_fake_rr *rr); static int rwrap_srv_recurse(const char *hostfile, unsigned recursion, const char *query, struct rwrap_fake_rr *rr) { int rc; rc = rwrap_get_record(hostfile, recursion, query, ns_t_a, rr); if (rc == 0) return 0; rc = rwrap_get_record(hostfile, recursion, query, ns_t_aaaa, rr); if (rc == ENOENT) rc = 0; return rc; } static int rwrap_cname_recurse(const char *hostfile, unsigned recursion, const char *query, struct rwrap_fake_rr *rr) { int rc; rc = rwrap_get_record(hostfile, recursion, query, ns_t_a, rr); if (rc == 0) return 0; rc = rwrap_get_record(hostfile, recursion, query, ns_t_aaaa, rr); if (rc == 0) return 0; rc = rwrap_get_record(hostfile, recursion, query, ns_t_cname, rr); if (rc == ENOENT) rc = 0; return rc; } static int rwrap_get_record(const char *hostfile, unsigned recursion, const char *query, int type, struct rwrap_fake_rr *rr) { FILE *fp = NULL; char buf[BUFSIZ]; char *key = NULL; char *value = NULL; int rc = ENOENT; if (recursion >= RWRAP_MAX_RECURSION) { RWRAP_LOG(RWRAP_LOG_ERROR, "Recursed too deep!\n"); return -1; } RWRAP_LOG(RWRAP_LOG_TRACE, "Searching in fake hosts file %s\n", hostfile); fp = fopen(hostfile, "r"); if (fp == NULL) { RWRAP_LOG(RWRAP_LOG_ERROR, "Opening %s failed: %s", hostfile, strerror(errno)); return -1; } while (fgets(buf, sizeof(buf), fp) != NULL) { char *rec_type; char *q; rec_type = buf; key = value = NULL; NEXT_KEY(rec_type, key); NEXT_KEY(key, value); if (key == NULL || value == NULL) { RWRAP_LOG(RWRAP_LOG_WARN, "Malformed line: not enough parts, use \"rec_type key data\n" "For example \"A cwrap.org 10.10.10.10\""); continue; } q = value; while(q[0] != '\n' && q[0] != '\0') { q++; } q[0] = '\0'; if (TYPE_MATCH(type, ns_t_a, rec_type, "A", key, query)) { rc = rwrap_create_fake_a_rr(key, value, rr); break; } else if (TYPE_MATCH(type, ns_t_aaaa, rec_type, "AAAA", key, query)) { rc = rwrap_create_fake_aaaa_rr(key, value, rr); break; } else if (TYPE_MATCH(type, ns_t_srv, rec_type, "SRV", key, query)) { rc = rwrap_create_fake_srv_rr(key, value, rr); if (rc == 0) { rc = rwrap_srv_recurse(hostfile, recursion+1, rr->rrdata.srv_rec.hostname, rr + 1); } break; } else if (TYPE_MATCH(type, ns_t_soa, rec_type, "SOA", key, query)) { rc = rwrap_create_fake_soa_rr(key, value, rr); break; } else if (TYPE_MATCH(type, ns_t_cname, rec_type, "CNAME", key, query)) { rc = rwrap_create_fake_cname_rr(key, value, rr); if (rc == 0) { rc = rwrap_cname_recurse(hostfile, recursion+1, value, rr + 1); } break; } else if (TYPE_MATCH(type, ns_t_a, rec_type, "CNAME", key, query)) { rc = rwrap_create_fake_cname_rr(key, value, rr); if (rc == 0) { rc = rwrap_cname_recurse(hostfile, recursion+1, value, rr + 1); } break; } } if (rc == ENOENT && recursion == 0 && key != NULL) { RWRAP_LOG(RWRAP_LOG_TRACE, "Record for [%s] not found\n", query); memcpy(rr->key, key, strlen(key) + 1); } fclose(fp); return rc; } static ssize_t rwrap_fake_empty(int type, const char *question, uint8_t *answer, size_t anslen) { ssize_t resp_data; size_t remaining = anslen; resp_data = rwrap_fake_header(&answer, remaining, 0, 0); if (resp_data < 0) { return -1; } remaining -= resp_data; resp_data += rwrap_fake_question(question, type, &answer, remaining); if (resp_data < 0) { return -1; } remaining -= resp_data; resp_data += rwrap_fake_rdata_common(type, 0, question, remaining, &answer); if (resp_data < 0) { return -1; } return resp_data; } static inline bool rwrap_known_type(int type) { switch (type) { case ns_t_a: case ns_t_aaaa: case ns_t_srv: case ns_t_soa: case ns_t_cname: return true; } return false; } static int rwrap_ancount(struct rwrap_fake_rr *rrs, int qtype) { int i; int ancount = 0; /* Include all RRs in the stack until the sought type * in the answer section. This is the case i.e. when looking * up an A record but the name points to a CNAME */ for (i = 0; i < RWRAP_MAX_RECURSION; i++) { ancount++; if (rwrap_known_type(rrs[i].type) && rrs[i].type == qtype) { break; } } /* Return 0 records if the sought type wasn't in the stack */ return i < RWRAP_MAX_RECURSION ? ancount : 0; } static int rwrap_arcount(struct rwrap_fake_rr *rrs, int ancount) { int i; int arcount = 0; /* start from index ancount */ for (i = ancount; i < RWRAP_MAX_RECURSION; i++) { if (rwrap_known_type(rrs[i].type)) { arcount++; } } return arcount; } static ssize_t rwrap_add_rr(struct rwrap_fake_rr *rr, uint8_t *answer, size_t anslen) { ssize_t resp_data; switch (rr->type) { case ns_t_a: resp_data = rwrap_fake_a(rr, answer, anslen); break; case ns_t_aaaa: resp_data = rwrap_fake_aaaa(rr, answer, anslen); break; case ns_t_srv: resp_data = rwrap_fake_srv(rr, answer, anslen); break; case ns_t_soa: resp_data = rwrap_fake_soa(rr, answer, anslen); break; case ns_t_cname: resp_data = rwrap_fake_cname(rr, answer, anslen); break; default: return -1; } return resp_data; } static ssize_t rwrap_fake_answer(struct rwrap_fake_rr *rrs, int type, uint8_t *answer, size_t anslen) { ssize_t resp_data; ssize_t rrlen; size_t remaining = anslen; int ancount; int arcount; int i; ancount = rwrap_ancount(rrs, type); arcount = rwrap_arcount(rrs, ancount); RWRAP_LOG(RWRAP_LOG_TRACE, "Got %d answers and %d additional records\n", ancount, arcount); resp_data = rwrap_fake_header(&answer, remaining, ancount, arcount); if (resp_data < 0) { return -1; } remaining -= resp_data; resp_data += rwrap_fake_question(rrs->key, rrs->type, &answer, remaining); if (resp_data < 0) { return -1; } remaining -= resp_data; /* answer */ for (i = 0; i < ancount; i++) { rrlen = rwrap_add_rr(&rrs[i], answer, remaining); if (rrlen < 0) { return -1; } remaining -= rrlen; answer += rrlen; resp_data += rrlen; } /* add authoritative NS here? */ /* additional records */ for (i = ancount; i < ancount + arcount; i++) { rrlen = rwrap_add_rr(&rrs[i], answer, remaining); if (rrlen < 0) { return -1; } remaining -= rrlen; answer += rrlen; resp_data += rrlen; } return resp_data; } /* Reads in a file in the following format: * TYPE RDATA * * Malformed entried are silently skipped. * Allocates answer buffer of size anslen that has to be freed after use. */ static int rwrap_res_fake_hosts(const char *hostfile, const char *query, int type, unsigned char *answer, size_t anslen) { int rc = ENOENT; char *query_name = NULL; size_t qlen = strlen(query); struct rwrap_fake_rr rrs[RWRAP_MAX_RECURSION]; ssize_t resp_size; RWRAP_LOG(RWRAP_LOG_TRACE, "Searching in fake hosts file %s\n", hostfile); if (qlen > 0 && query[qlen-1] == '.') { qlen--; } query_name = strndup(query, qlen); if (query_name == NULL) { return -1; } rwrap_fake_rr_init(rrs, RWRAP_MAX_RECURSION); rc = rwrap_get_record(hostfile, 0, query_name, type, rrs); switch (rc) { case 0: RWRAP_LOG(RWRAP_LOG_TRACE, "Found record for [%s]\n", query_name); resp_size = rwrap_fake_answer(rrs, type, answer, anslen); break; case ENOENT: RWRAP_LOG(RWRAP_LOG_TRACE, "No record for [%s]\n", query_name); resp_size = rwrap_fake_empty(type, rrs->key, answer, anslen); break; default: RWRAP_LOG(RWRAP_LOG_ERROR, "Error searching for [%s]\n", query_name); free(query_name); return -1; } switch (resp_size) { case -1: RWRAP_LOG(RWRAP_LOG_ERROR, "Error faking answer for [%s]\n", query_name); break; default: RWRAP_LOG(RWRAP_LOG_TRACE, "Successfully faked answer for [%s]\n", query_name); break; } free(query_name); return resp_size; } /********************************************************* * RWRAP LOADING LIBC FUNCTIONS *********************************************************/ #include typedef int (*__libc_res_ninit)(struct __res_state *state); typedef int (*__libc___res_ninit)(struct __res_state *state); typedef void (*__libc_res_nclose)(struct __res_state *state); typedef void (*__libc___res_nclose)(struct __res_state *state); typedef int (*__libc_res_nquery)(struct __res_state *state, const char *dname, int class, int type, unsigned char *answer, int anslen); typedef int (*__libc___res_nquery)(struct __res_state *state, const char *dname, int class, int type, unsigned char *answer, int anslen); typedef int (*__libc_res_nsearch)(struct __res_state *state, const char *dname, int class, int type, unsigned char *answer, int anslen); typedef int (*__libc___res_nsearch)(struct __res_state *state, const char *dname, int class, int type, unsigned char *answer, int anslen); #define RWRAP_SYMBOL_ENTRY(i) \ union { \ __libc_##i f; \ void *obj; \ } _libc_##i struct rwrap_libc_symbols { RWRAP_SYMBOL_ENTRY(res_ninit); RWRAP_SYMBOL_ENTRY(__res_ninit); RWRAP_SYMBOL_ENTRY(res_nclose); RWRAP_SYMBOL_ENTRY(__res_nclose); RWRAP_SYMBOL_ENTRY(res_nquery); RWRAP_SYMBOL_ENTRY(__res_nquery); RWRAP_SYMBOL_ENTRY(res_nsearch); RWRAP_SYMBOL_ENTRY(__res_nsearch); }; #undef RWRAP_SYMBOL_ENTRY struct rwrap { struct { void *handle; struct rwrap_libc_symbols symbols; } libc; struct { void *handle; struct rwrap_libc_symbols symbols; } libresolv; bool initialised; bool enabled; char *socket_dir; }; static struct rwrap rwrap; enum rwrap_lib { RWRAP_LIBC, RWRAP_LIBRESOLV }; #ifndef NDEBUG static const char *rwrap_str_lib(enum rwrap_lib lib) { switch (lib) { case RWRAP_LIBC: return "libc"; case RWRAP_LIBRESOLV: return "libresolv"; } /* Compiler would warn us about unhandled enum value if we get here */ return "unknown"; } #endif static void *rwrap_load_lib_handle(enum rwrap_lib lib) { int flags = RTLD_LAZY; void *handle = NULL; int i; #ifdef RTLD_DEEPBIND flags |= RTLD_DEEPBIND; #endif switch (lib) { case RWRAP_LIBRESOLV: #ifdef HAVE_LIBRESOLV handle = rwrap.libresolv.handle; if (handle == NULL) { for (i = 10; i >= 0; i--) { char soname[256] = {0}; snprintf(soname, sizeof(soname), "libresolv.so.%d", i); handle = dlopen(soname, flags); if (handle != NULL) { break; } } rwrap.libresolv.handle = handle; } break; #endif /* FALL TROUGH */ case RWRAP_LIBC: handle = rwrap.libc.handle; #ifdef LIBC_SO if (handle == NULL) { handle = dlopen(LIBC_SO, flags); rwrap.libc.handle = handle; } #endif if (handle == NULL) { for (i = 10; i >= 0; i--) { char soname[256] = {0}; snprintf(soname, sizeof(soname), "libc.so.%d", i); handle = dlopen(soname, flags); if (handle != NULL) { break; } } rwrap.libc.handle = handle; } break; } if (handle == NULL) { #ifdef RTLD_NEXT handle = rwrap.libc.handle = rwrap.libresolv.handle = RTLD_NEXT; #else RWRAP_LOG(RWRAP_LOG_ERROR, "Failed to dlopen library: %s\n", dlerror()); exit(-1); #endif } return handle; } static void *_rwrap_bind_symbol(enum rwrap_lib lib, const char *fn_name) { void *handle; void *func; handle = rwrap_load_lib_handle(lib); func = dlsym(handle, fn_name); if (func == NULL) { RWRAP_LOG(RWRAP_LOG_ERROR, "Failed to find %s: %s\n", fn_name, dlerror()); exit(-1); } RWRAP_LOG(RWRAP_LOG_TRACE, "Loaded %s from %s", fn_name, rwrap_str_lib(lib)); return func; } #define rwrap_bind_symbol_libc(sym_name) \ if (rwrap.libc.symbols._libc_##sym_name.obj == NULL) { \ rwrap.libc.symbols._libc_##sym_name.obj = \ _rwrap_bind_symbol(RWRAP_LIBC, #sym_name); \ } #define rwrap_bind_symbol_libresolv(sym_name) \ if (rwrap.libresolv.symbols._libc_##sym_name.obj == NULL) { \ rwrap.libresolv.symbols._libc_##sym_name.obj = \ _rwrap_bind_symbol(RWRAP_LIBRESOLV, #sym_name); \ } /* * IMPORTANT * * Functions especially from libc need to be loaded individually, you can't load * all at once or gdb will segfault at startup. The same applies to valgrind and * has probably something todo with with the linker. * So we need load each function at the point it is called the first time. */ static int libc_res_ninit(struct __res_state *state) { #if !defined(res_ninit) && defined(HAVE_RES_NINIT) #if defined(HAVE_RES_NINIT_IN_LIBRESOLV) rwrap_bind_symbol_libresolv(res_ninit); return rwrap.libresolv.symbols._libc_res_ninit.f(state); #else /* HAVE_RES_NINIT_IN_LIBRESOLV */ rwrap_bind_symbol_libc(res_ninit); return rwrap.libc.symbols._libc_res_ninit.f(state); #endif /* HAVE_RES_NINIT_IN_LIBRESOLV */ #elif defined(HAVE___RES_NINIT) rwrap_bind_symbol_libc(__res_ninit); return rwrap.libc.symbols._libc___res_ninit.f(state); #else #error "No res_ninit function" #endif } static void libc_res_nclose(struct __res_state *state) { #if !defined(res_close) && defined(HAVE_RES_NCLOSE) #if defined(HAVE_RES_NCLOSE_IN_LIBRESOLV) rwrap_bind_symbol_libresolv(res_nclose); rwrap.libresolv.symbols._libc_res_nclose.f(state); return; #else /* HAVE_RES_NCLOSE_IN_LIBRESOLV */ rwrap_bind_symbol_libc(res_nclose); rwrap.libc.symbols._libc_res_nclose.f(state); return; #endif /* HAVE_RES_NCLOSE_IN_LIBRESOLV */ #elif defined(HAVE___RES_NCLOSE) rwrap_bind_symbol_libc(__res_nclose); rwrap.libc.symbols._libc___res_nclose.f(state); #else #error "No res_nclose function" #endif } static int libc_res_nquery(struct __res_state *state, const char *dname, int class, int type, unsigned char *answer, int anslen) { #if !defined(res_nquery) && defined(HAVE_RES_NQUERY) rwrap_bind_symbol_libresolv(res_nquery); return rwrap.libresolv.symbols._libc_res_nquery.f(state, dname, class, type, answer, anslen); #elif defined(HAVE___RES_NQUERY) rwrap_bind_symbol_libresolv(__res_nquery); return rwrap.libresolv.symbols._libc___res_nquery.f(state, dname, class, type, answer, anslen); #else #error "No res_nquery function" #endif } static int libc_res_nsearch(struct __res_state *state, const char *dname, int class, int type, unsigned char *answer, int anslen) { #if !defined(res_nsearch) && defined(HAVE_RES_NSEARCH) rwrap_bind_symbol_libresolv(res_nsearch); return rwrap.libresolv.symbols._libc_res_nsearch.f(state, dname, class, type, answer, anslen); #elif defined(HAVE___RES_NSEARCH) rwrap_bind_symbol_libresolv(__res_nsearch); return rwrap.libresolv.symbols._libc___res_nsearch.f(state, dname, class, type, answer, anslen); #else #error "No res_nsearch function" #endif } /**************************************************************************** * RES_HELPER ***************************************************************************/ static int rwrap_parse_resolv_conf(struct __res_state *state, const char *resolv_conf) { FILE *fp; char buf[BUFSIZ]; int nserv = 0; fp = fopen(resolv_conf, "r"); if (fp == NULL) { RWRAP_LOG(RWRAP_LOG_ERROR, "Opening %s failed: %s", resolv_conf, strerror(errno)); return -1; } while(fgets(buf, sizeof(buf), fp) != NULL) { char *p; /* Ignore comments */ if (buf[0] == '#' || buf[0] == ';') { continue; } if (RESOLV_MATCH(buf, "nameserver") && nserv < MAXNS) { struct in_addr a; char *q; int ok; p = buf + strlen("nameserver"); /* Skip spaces and tabs */ while(isblank((int)p[0])) { p++; } q = p; while(q[0] != '\n' && q[0] != '\0') { q++; } q[0] = '\0'; ok = inet_pton(AF_INET, p, &a); if (ok) { state->nsaddr_list[state->nscount] = (struct sockaddr_in) { .sin_family = AF_INET, .sin_addr = a, .sin_port = htons(53), .sin_zero = { 0 }, }; state->nscount++; nserv++; } else { #ifdef HAVE_RESOLV_IPV6_NSADDRS /* IPv6 */ struct in6_addr a6; ok = inet_pton(AF_INET6, p, &a6); if (ok) { struct sockaddr_in6 *sa6; sa6 = malloc(sizeof(*sa6)); if (sa6 == NULL) { fclose(fp); return -1; } sa6->sin6_family = AF_INET6; sa6->sin6_port = htons(53); sa6->sin6_flowinfo = 0; sa6->sin6_addr = a6; state->_u._ext.nsaddrs[state->_u._ext.nscount] = sa6; state->_u._ext.nssocks[state->_u._ext.nscount] = -1; state->_u._ext.nsmap[state->_u._ext.nscount] = MAXNS + 1; state->_u._ext.nscount++; nserv++; } else { RWRAP_LOG(RWRAP_LOG_ERROR, "Malformed DNS server"); continue; } #else /* !HAVE_RESOLV_IPV6_NSADDRS */ /* * BSD uses an opaque structure to store the * IPv6 addresses. So we can not simply store * these addresses the same way as above. */ RWRAP_LOG(RWRAP_LOG_WARN, "resolve_wrapper does not support " "IPv6 on this platform"); continue; #endif } continue; } /* TODO: match other keywords */ } if (ferror(fp)) { RWRAP_LOG(RWRAP_LOG_ERROR, "Reading from %s failed", resolv_conf); fclose(fp); return -1; } fclose(fp); return 0; } /**************************************************************************** * RES_NINIT ***************************************************************************/ static int rwrap_res_ninit(struct __res_state *state) { int rc; rc = libc_res_ninit(state); if (rc == 0) { const char *resolv_conf = getenv("RESOLV_WRAPPER_CONF"); if (resolv_conf != NULL) { uint16_t i; (void)i; /* maybe unused */ /* Delete name servers */ state->nscount = 0; memset(state->nsaddr_list, 0, sizeof(state->nsaddr_list)); state->_u._ext.nscount = 0; #ifdef HAVE_RESOLV_IPV6_NSADDRS for (i = 0; i < state->_u._ext.nscount; i++) { SAFE_FREE(state->_u._ext.nsaddrs[i]); } #endif rc = rwrap_parse_resolv_conf(state, resolv_conf); } } return rc; } #if !defined(res_ninit) && defined(HAVE_RES_NINIT) int res_ninit(struct __res_state *state) #elif defined(HAVE___RES_NINIT) int __res_ninit(struct __res_state *state) #endif { return rwrap_res_ninit(state); } /**************************************************************************** * RES_INIT ***************************************************************************/ static struct __res_state rwrap_res_state; static int rwrap_res_init(void) { int rc; rc = rwrap_res_ninit(&rwrap_res_state); return rc; } #if !defined(res_ninit) && defined(HAVE_RES_INIT) int res_init(void) #elif defined(HAVE___RES_INIT) int __res_init(void) #endif { return rwrap_res_init(); } /**************************************************************************** * RES_NCLOSE ***************************************************************************/ static void rwrap_res_nclose(struct __res_state *state) { #ifdef HAVE_RESOLV_IPV6_NSADDRS int i; #endif libc_res_nclose(state); #ifdef HAVE_RESOLV_IPV6_NSADDRS if (state != NULL) { for (i = 0; i < state->_u._ext.nscount; i++) { SAFE_FREE(state->_u._ext.nsaddrs[i]); } } #endif } #if !defined(res_nclose) && defined(HAVE_RES_NCLOSE) void res_nclose(struct __res_state *state) #elif defined(HAVE___RES_NCLOSE) void __res_nclose(struct __res_state *state) #endif { rwrap_res_nclose(state); } /**************************************************************************** * RES_CLOSE ***************************************************************************/ static void rwrap_res_close(void) { rwrap_res_nclose(&rwrap_res_state); } #if defined(HAVE_RES_CLOSE) void res_close(void) #elif defined(HAVE___RES_CLOSE) void __res_close(void) #endif { rwrap_res_close(); } /**************************************************************************** * RES_NQUERY ***************************************************************************/ static int rwrap_res_nquery(struct __res_state *state, const char *dname, int class, int type, unsigned char *answer, int anslen) { int rc; const char *fake_hosts; #ifndef NDEBUG int i; #endif RWRAP_LOG(RWRAP_LOG_TRACE, "Resolve the domain name [%s] - class=%d, type=%d", dname, class, type); #ifndef NDEBUG for (i = 0; i < state->nscount; i++) { char ip[INET6_ADDRSTRLEN]; inet_ntop(AF_INET, &state->nsaddr_list[i].sin_addr, ip, sizeof(ip)); RWRAP_LOG(RWRAP_LOG_TRACE, " nameserver: %s", ip); } #endif fake_hosts = getenv("RESOLV_WRAPPER_HOSTS"); if (fake_hosts != NULL) { rc = rwrap_res_fake_hosts(fake_hosts, dname, type, answer, anslen); } else { rc = libc_res_nquery(state, dname, class, type, answer, anslen); } RWRAP_LOG(RWRAP_LOG_TRACE, "The returned response length is: %d", rc); return rc; } #if !defined(res_nquery) && defined(HAVE_RES_NQUERY) int res_nquery(struct __res_state *state, const char *dname, int class, int type, unsigned char *answer, int anslen) #elif defined(HAVE___RES_NQUERY) int __res_nquery(struct __res_state *state, const char *dname, int class, int type, unsigned char *answer, int anslen) #endif { return rwrap_res_nquery(state, dname, class, type, answer, anslen); } /**************************************************************************** * RES_QUERY ***************************************************************************/ static int rwrap_res_query(const char *dname, int class, int type, unsigned char *answer, int anslen) { int rc; rc = rwrap_res_ninit(&rwrap_res_state); if (rc != 0) { return rc; } rc = rwrap_res_nquery(&rwrap_res_state, dname, class, type, answer, anslen); return rc; } #if !defined(res_query) && defined(HAVE_RES_QUERY) int res_query(const char *dname, int class, int type, unsigned char *answer, int anslen) #elif defined(HAVE___RES_QUERY) int __res_query(const char *dname, int class, int type, unsigned char *answer, int anslen) #endif { return rwrap_res_query(dname, class, type, answer, anslen); } /**************************************************************************** * RES_NSEARCH ***************************************************************************/ static int rwrap_res_nsearch(struct __res_state *state, const char *dname, int class, int type, unsigned char *answer, int anslen) { int rc; const char *fake_hosts; #ifndef NDEBUG int i; #endif RWRAP_LOG(RWRAP_LOG_TRACE, "Resolve the domain name [%s] - class=%d, type=%d", dname, class, type); #ifndef NDEBUG for (i = 0; i < state->nscount; i++) { char ip[INET6_ADDRSTRLEN]; inet_ntop(AF_INET, &state->nsaddr_list[i].sin_addr, ip, sizeof(ip)); RWRAP_LOG(RWRAP_LOG_TRACE, " nameserver: %s", ip); } #endif fake_hosts = getenv("RESOLV_WRAPPER_HOSTS"); if (fake_hosts != NULL) { rc = rwrap_res_fake_hosts(fake_hosts, dname, type, answer, anslen); } else { rc = libc_res_nsearch(state, dname, class, type, answer, anslen); } RWRAP_LOG(RWRAP_LOG_TRACE, "The returned response length is: %d", rc); return rc; } #if !defined(res_nsearch) && defined(HAVE_RES_NSEARCH) int res_nsearch(struct __res_state *state, const char *dname, int class, int type, unsigned char *answer, int anslen) #elif defined(HAVE___RES_NSEARCH) int __res_nsearch(struct __res_state *state, const char *dname, int class, int type, unsigned char *answer, int anslen) #endif { return rwrap_res_nsearch(state, dname, class, type, answer, anslen); } /**************************************************************************** * RES_QUERY ***************************************************************************/ static int rwrap_res_search(const char *dname, int class, int type, unsigned char *answer, int anslen) { int rc; rc = rwrap_res_ninit(&rwrap_res_state); if (rc != 0) { return rc; } rc = rwrap_res_nsearch(&rwrap_res_state, dname, class, type, answer, anslen); return rc; } #if !defined(res_search) && defined(HAVE_RES_SEARCH) int res_search(const char *dname, int class, int type, unsigned char *answer, int anslen) #elif defined(HAVE___RES_SEARCH) int __res_search(const char *dname, int class, int type, unsigned char *answer, int anslen) #endif { return rwrap_res_search(dname, class, type, answer, anslen); }