/* The original version of this module was written by Adam Langley; for * a history of modifications, check out the subversion logs. * * When editing this module, try to keep it re-mergeable by Adam. Don't * reformat the whitespace, add Tor dependencies, or so on. * * TODO: * - Replace all externally visible magic numbers with #defined constants. * - Write documentation for APIs of all external functions. */ /* Async DNS Library * Adam Langley * Public Domain code * * This software is Public Domain. To view a copy of the public domain dedication, * visit http://creativecommons.org/licenses/publicdomain/ or send a letter to * Creative Commons, 559 Nathan Abbott Way, Stanford, California 94305, USA. * * I ask and expect, but do not require, that all derivative works contain an * attribution similar to: * Parts developed by Adam Langley * * You may wish to replace the word "Parts" with something else depending on * the amount of original code. * * (Derivative works does not include programs which link against, run or include * the source verbatim in their source distributions) * * Version: 0.1b */ #include "eventdns_tor.h" #include /* #define NDEBUG */ #ifndef DNS_USE_CPU_CLOCK_FOR_ID #ifndef DNS_USE_GETTIMEOFDAY_FOR_ID #ifndef DNS_USE_OPENSSL_FOR_ID #error Must configure at least one id generation method. #error Please see the documentation. #endif #endif #endif /* #define _POSIX_C_SOURCE 200507 */ #define _GNU_SOURCE #ifdef DNS_USE_CPU_CLOCK_FOR_ID #ifdef DNS_USE_OPENSSL_FOR_ID #error Multiple id options selected #endif #ifdef DNS_USE_GETTIMEOFDAY_FOR_ID #error Multiple id options selected #endif #include #endif #ifdef DNS_USE_OPENSSL_FOR_ID #ifdef DNS_USE_GETTIMEOFDAY_FOR_ID #error Multiple id options selected #endif #include #endif #include #ifdef HAVE_FCNTL_H #include #endif #ifdef HAVE_SYS_TIME_H #include #endif #ifdef HAVE_STDINT_H #include #endif #include #include #include #include #ifdef HAVE_UNISTD_H #include #endif #ifdef HAVE_LIMITS_H #include #endif #include #include #include #include #include "eventdns.h" #ifdef WIN32 #include #include #include #else #include #include #include #endif #ifdef HAVE_NETINET_IN6_H #include #endif #ifdef WIN32 typedef int socklen_t; #endif #define EVDNS_LOG_DEBUG 0 #define EVDNS_LOG_WARN 1 #ifndef HOST_NAME_MAX #define HOST_NAME_MAX 255 #endif #ifndef NDEBUG #include #endif /* for debugging possible memory leaks. */ #define mm_malloc(x) tor_malloc(x) #define mm_realloc(x,y) tor_realloc((x),(y)) #define mm_free(x) tor_free(x) #define mm_strdup(x) tor_strdup(x) #define _mm_free(x) _tor_free(x) #undef MIN #define MIN(a,b) ((a)<(b)?(a):(b)) #if 0 #ifdef __USE_ISOC99B /* libevent doesn't work without this */ typedef uint8_t u_char; typedef unsigned int uint; #endif #endif #include #define u64 uint64_t #define u32 uint32_t #define u16 uint16_t #define u8 uint8_t #define MAX_ADDRS 4 /* maximum number of addresses from a single packet */ /* which we bother recording */ #define TYPE_A EVDNS_TYPE_A #define TYPE_CNAME 5 #define TYPE_PTR EVDNS_TYPE_PTR #define TYPE_AAAA EVDNS_TYPE_AAAA #define CLASS_INET EVDNS_CLASS_INET #define CLEAR(x) do { memset((x), 0xF0, sizeof(*(x))); } while(0) struct evdns_request { u8 *request; /* the dns packet data */ unsigned int request_len; int reissue_count; int tx_count; /* the number of times that this packet has been sent */ unsigned int request_type; /* TYPE_PTR or TYPE_A */ void *user_pointer; /* the pointer given to us for this request */ evdns_callback_type user_callback; struct nameserver *ns; /* the server which we last sent it */ /* elements used by the searching code */ int search_index; struct search_state *search_state; char *search_origname; /* needs to be mm_free()ed */ int search_flags; /* these objects are kept in a circular list */ struct evdns_request *next, *prev; u16 timeout_event_deleted; /**< Debugging: where was timeout_event * deleted? 0 for "it's added." */ struct event timeout_event; u16 trans_id; /* the transaction id */ char request_appended; /* true if the request pointer is data which follows this struct */ char transmit_me; /* needs to be transmitted */ }; #ifndef HAVE_STRUCT_IN6_ADDR struct in6_addr { u8 s6_addr[16]; }; #endif struct reply { unsigned int type; unsigned int have_answer; union { struct { u32 addrcount; u32 addresses[MAX_ADDRS]; } a; struct { u32 addrcount; struct in6_addr addresses[MAX_ADDRS]; } aaaa; struct { char name[HOST_NAME_MAX]; } ptr; } data; }; struct nameserver { int socket; /* a connected UDP socket */ struct sockaddr_storage address; int failed_times; /* number of times which we have given this server a chance */ int timedout; /* number of times in a row a request has timed out */ struct event event; /* these objects are kept in a circular list */ struct nameserver *next, *prev; u16 timeout_event_deleted; /**< Debugging: where was timeout_event * deleted? 0 for "it's added." */ struct event timeout_event; /* used to keep the timeout for */ /* when we next probe this server. */ /* Valid if state == 0 */ char state; /* zero if we think that this server is down */ char choked; /* true if we have an EAGAIN from this server's socket */ char write_waiting; /* true if we are waiting for EV_WRITE events */ }; static struct evdns_request *req_head = NULL, *req_waiting_head = NULL; static struct nameserver *server_head = NULL; /* Represents a local port where we're listening for DNS requests. Right now, */ /* only UDP is supported. */ struct evdns_server_port { int socket; /* socket we use to read queries and write replies. */ int refcnt; /* reference count. */ char choked; /* Are we currently blocked from writing? */ char closing; /* Are we trying to close this port, pending writes? */ evdns_request_callback_fn_type user_callback; /* Fn to handle requests */ void *user_data; /* Opaque pointer passed to user_callback */ struct event event; /* Read/write event */ /* circular list of replies that we want to write. */ struct server_request *pending_replies; }; /* Represents part of a reply being built. (That is, a single RR.) */ struct server_reply_item { struct server_reply_item *next; /* next item in sequence. */ char *name; /* name part of the RR */ u16 type : 16; /* The RR type */ u16 class : 16; /* The RR class (usually CLASS_INET) */ u32 ttl; /* The RR TTL */ char is_name; /* True iff data is a label */ u16 datalen; /* Length of data; -1 if data is a label */ void *data; /* The contents of the RR */ }; /* Represents a request that we've received as a DNS server, and holds */ /* the components of the reply as we're constructing it. */ struct server_request { /* Pointers to the next and previous entries on the list of replies */ /* that we're waiting to write. Only set if we have tried to respond */ /* and gotten EAGAIN. */ struct server_request *next_pending; struct server_request *prev_pending; u16 trans_id; /* Transaction id. */ struct evdns_server_port *port; /* Which port received this request on? */ struct sockaddr_storage addr; /* Where to send the response */ socklen_t addrlen; /* length of addr */ int n_answer; /* how many answer RRs have been set? */ int n_authority; /* how many authority RRs have been set? */ int n_additional; /* how many additional RRs have been set? */ struct server_reply_item *answer; /* linked list of answer RRs */ struct server_reply_item *authority; /* linked list of authority RRs */ struct server_reply_item *additional; /* linked list of additional RRs */ /* Constructed response. Only set once we're ready to send a reply. */ /* Once this is set, the RR fields are cleared, and no more should be set. */ char *response; size_t response_len; /* Caller-visible fields: flags, questions. */ struct evdns_server_request base; }; /* helper macro */ #define OFFSET_OF(st, member) ((off_t) (((char*)&((st*)0)->member)-(char*)0)) /* Given a pointer to an evdns_server_request, get the corresponding */ /* server_request. */ #define TO_SERVER_REQUEST(base_ptr) \ ((struct server_request*) \ (((char*)(base_ptr) - OFFSET_OF(struct server_request, base)))) /* The number of good nameservers that we have */ static int global_good_nameservers = 0; /* inflight requests are contained in the req_head list */ /* and are actually going out across the network */ static int global_requests_inflight = 0; /* requests which aren't inflight are in the waiting list */ /* and are counted here */ static int global_requests_waiting = 0; static int global_max_requests_inflight = 64; static struct timeval global_timeout = {5, 0}; /* 5 seconds */ static int global_max_reissues = 1; /* a reissue occurs when we get some errors from the server */ static int global_max_retransmits = 3; /* number of times we'll retransmit a request which timed out */ /* number of timeouts in a row before we consider this server to be down */ static int global_max_nameserver_timeout = 3; /* true iff we should use the 0x20 hack. */ static int global_randomize_case = 1; /* These are the timeout values for nameservers. If we find a nameserver is down */ /* we try to probe it at intervals as given below. Values are in seconds. */ static const struct timeval global_nameserver_timeouts[] = {{10, 0}, {60, 0}, {300, 0}, {900, 0}, {3600, 0}}; static const int global_nameserver_timeouts_length = (int)(sizeof(global_nameserver_timeouts)/sizeof(struct timeval)); static struct nameserver *nameserver_pick(void); static void evdns_request_insert(struct evdns_request *req, struct evdns_request **head); static void nameserver_ready_callback(int fd, short events, void *arg); static int evdns_transmit(void); static int evdns_request_transmit(struct evdns_request *req); static void nameserver_send_probe(struct nameserver *const ns); static void search_request_finished(struct evdns_request *const); static int search_try_next(struct evdns_request *const req); static int search_request_new(int type, const char *const name, int flags, evdns_callback_type user_callback, void *user_arg); static void evdns_requests_pump_waiting_queue(void); static u16 transaction_id_pick(void); static struct evdns_request *request_new(int type, const char *name, int flags, evdns_callback_type callback, void *ptr); static void request_submit(struct evdns_request *req); static int server_request_free(struct server_request *req); static void server_request_free_answers(struct server_request *req); static void server_port_free(struct evdns_server_port *port); static void server_port_ready_callback(int fd, short events, void *arg); static int strtoint(const char *const str); #ifdef WIN32 static int last_error(int sock) { int optval, optvallen=sizeof(optval); int err = WSAGetLastError(); if (err == WSAEWOULDBLOCK && sock >= 0) { if (getsockopt(sock, SOL_SOCKET, SO_ERROR, (void*)&optval, &optvallen)) return err; if (optval) return optval; } return err; } static int error_is_eagain(int err) { return err == EAGAIN || err == WSAEWOULDBLOCK; } #define inet_aton(c, addr) tor_inet_aton((c), (addr)) #define CLOSE_SOCKET(x) closesocket(x) #else #define last_error(sock) (errno) #define error_is_eagain(err) ((err) == EAGAIN) #define CLOSE_SOCKET(x) close(x) #endif #define ISSPACE(c) TOR_ISSPACE(c) #define ISDIGIT(c) TOR_ISDIGIT(c) #define ISALPHA(c) TOR_ISALPHA(c) #define TOLOWER(c) TOR_TOLOWER(c) #define TOUPPER(c) TOR_TOUPPER(c) #ifndef NDEBUG static const char * debug_ntoa(u32 address) { static char buf[32]; u32 a = ntohl(address); snprintf(buf, sizeof(buf), "%d.%d.%d.%d", (int)(u8)((a>>24)&0xff), (int)(u8)((a>>16)&0xff), (int)(u8)((a>>8 )&0xff), (int)(u8)((a )&0xff)); return buf; } static const char * debug_ntop(const struct sockaddr *sa) { if (sa->sa_family == AF_INET) { struct sockaddr_in *sin = (struct sockaddr_in *) sa; return debug_ntoa(sin->sin_addr.s_addr); } if (sa->sa_family == AF_INET6) { /* Tor-specific. In libevent, add more check code. */ static char buf[128]; struct sockaddr_in6 *sin = (struct sockaddr_in6 *) sa; tor_inet_ntop(AF_INET6, &sin->sin6_addr, buf, sizeof(buf)); return buf; } return ""; } #endif static evdns_debug_log_fn_type evdns_log_fn = NULL; void evdns_set_log_fn(evdns_debug_log_fn_type fn) { evdns_log_fn = fn; } #ifdef __GNUC__ #define EVDNS_LOG_CHECK __attribute__ ((format(printf, 2, 3))) #else #define EVDNS_LOG_CHECK #endif static void _evdns_log(int warn, const char *fmt, ...) EVDNS_LOG_CHECK; static void _evdns_log(int warn, const char *fmt, ...) { va_list args; static char buf[512]; if (!evdns_log_fn) return; va_start(args,fmt); #ifdef WIN32 _vsnprintf(buf, sizeof(buf), fmt, args); #else vsnprintf(buf, sizeof(buf), fmt, args); #endif buf[sizeof(buf)-1] = '\0'; evdns_log_fn(warn, buf); va_end(args); } #define log _evdns_log static int sockaddr_eq(const struct sockaddr *sa1, const struct sockaddr *sa2, int include_port) { if (sa1->sa_family != sa2->sa_family) return 0; if (sa1->sa_family == AF_INET) { const struct sockaddr_in *sin1, *sin2; sin1 = (const struct sockaddr_in *)sa1; sin2 = (const struct sockaddr_in *)sa2; if (sin1->sin_addr.s_addr != sin2->sin_addr.s_addr) return 0; else if (include_port && sin1->sin_port != sin2->sin_port) return 0; else return 1; } #ifdef AF_INET6 if (sa1->sa_family == AF_INET6) { const struct sockaddr_in6 *sin1, *sin2; sin1 = (const struct sockaddr_in6 *)sa1; sin2 = (const struct sockaddr_in6 *)sa2; if (memcmp(sin1->sin6_addr.s6_addr, sin2->sin6_addr.s6_addr, 16)) return 0; else if (include_port && sin1->sin6_port != sin2->sin6_port) return 0; else return 1; } #endif return 1; } /* for debugging bug 929. XXXX022 */ static int _add_timeout_event(u16 *lineno, struct event *ev, struct timeval *to) { *lineno = 0; return evtimer_add(ev, to); } #define add_timeout_event(s, to) \ (_add_timeout_event(&(s)->timeout_event_deleted, &(s)->timeout_event, (to))) /* for debugging bug 929. XXXX022 */ static int _del_timeout_event(u16 *lineno, struct event *ev, int line) { if (*lineno) { log(EVDNS_LOG_DEBUG, "Duplicate timeout event_del from line %d: first call " "was at %d.", line, (int)*lineno); return 0; } else { *lineno = (u16)line; return event_del(ev); } } #define del_timeout_event(s) \ (_del_timeout_event(&(s)->timeout_event_deleted, &(s)->timeout_event, \ __LINE__)) /* For debugging bug 929/957. XXXX022 */ static int _del_timeout_event_if_set(u16 *lineno, struct event *ev, int line) { if (*lineno == 0) { log(EVDNS_LOG_DEBUG, "Event that I thought was non-added as of line %d " "was actually added on line %d", line, (int)*lineno); *lineno = line; return event_del(ev); } return 0; } #define del_timeout_event_if_set(s) \ _del_timeout_event_if_set(&(s)->timeout_event_deleted, \ &(s)->timeout_event, \ __LINE__) /* This walks the list of inflight requests to find the */ /* one with a matching transaction id. Returns NULL on */ /* failure */ static struct evdns_request * request_find_from_trans_id(u16 trans_id) { struct evdns_request *req = req_head, *const started_at = req_head; if (req) { do { if (req->trans_id == trans_id) return req; req = req->next; } while (req != started_at); } return NULL; } /* a libevent callback function which is called when a nameserver */ /* has gone down and we want to test if it has came back to life yet */ static void nameserver_prod_callback(int fd, short events, void *arg) { struct nameserver *const ns = (struct nameserver *) arg; (void)fd; (void)events; nameserver_send_probe(ns); } /* a libevent callback which is called when a nameserver probe (to see if */ /* it has come back to life) times out. We increment the count of failed_times */ /* and wait longer to send the next probe packet. */ static void nameserver_probe_failed(struct nameserver *const ns) { const struct timeval * timeout; del_timeout_event(ns); CLEAR(&ns->timeout_event); if (ns->state == 1) { /* This can happen if the nameserver acts in a way which makes us mark */ /* it as bad and then starts sending good replies. */ return; } timeout = &global_nameserver_timeouts[MIN(ns->failed_times, global_nameserver_timeouts_length - 1)]; ns->failed_times++; del_timeout_event_if_set(ns); evtimer_set(&ns->timeout_event, nameserver_prod_callback, ns); if (add_timeout_event(ns, (struct timeval *) timeout) < 0) { log(EVDNS_LOG_WARN, "Error from libevent when adding timer event for %s", debug_ntop((struct sockaddr *)&ns->address)); /* ???? Do more? */ } } /* called when a nameserver has been deemed to have failed. For example, too */ /* many packets have timed out etc */ static void nameserver_failed(struct nameserver *const ns, const char *msg) { struct evdns_request *req, *started_at; /* if this nameserver has already been marked as failed */ /* then don't do anything */ if (!ns->state) return; log(EVDNS_LOG_WARN, "Nameserver %s has failed: %s", debug_ntop((struct sockaddr *)&ns->address), msg); global_good_nameservers--; assert(global_good_nameservers >= 0); if (global_good_nameservers == 0) { log(EVDNS_LOG_WARN, "All nameservers have failed"); } ns->state = 0; ns->failed_times = 1; del_timeout_event_if_set(ns); evtimer_set(&ns->timeout_event, nameserver_prod_callback, ns); if (add_timeout_event(ns, (struct timeval *) &global_nameserver_timeouts[0]) < 0) { log(EVDNS_LOG_WARN, "Error from libevent when adding timer event for %s", debug_ntop((struct sockaddr *)&ns->address)); /* ???? Do more? */ } /* walk the list of inflight requests to see if any can be reassigned to */ /* a different server. Requests in the waiting queue don't have a */ /* nameserver assigned yet */ /* if we don't have *any* good nameservers then there's no point */ /* trying to reassign requests to one */ if (!global_good_nameservers) return; req = req_head; started_at = req_head; if (req) { do { if (req->tx_count == 0 && req->ns == ns) { /* still waiting to go out, can be moved */ /* to another server */ req->ns = nameserver_pick(); } req = req->next; } while (req != started_at); } } static void nameserver_up(struct nameserver *const ns) { if (ns->state) return; log(EVDNS_LOG_WARN, "Nameserver %s is back up", debug_ntop((struct sockaddr *)&ns->address)); del_timeout_event(ns); CLEAR(&ns->timeout_event); ns->state = 1; ns->failed_times = 0; ns->timedout = 0; global_good_nameservers++; } static void request_trans_id_set(struct evdns_request *const req, const u16 trans_id) { req->trans_id = trans_id; *((u16 *) req->request) = htons(trans_id); } /* Called to remove a request from a list and dealloc it. */ /* head is a pointer to the head of the list it should be */ /* removed from or NULL if the request isn't in a list. */ static void request_finished(struct evdns_request *const req, struct evdns_request **head) { if (head) { if (req->next == req) { /* only item in the list */ *head = NULL; } else { req->next->prev = req->prev; req->prev->next = req->next; if (*head == req) *head = req->next; } } log(EVDNS_LOG_DEBUG, "Removing timeout for request %lx", (unsigned long) req); del_timeout_event(req); CLEAR(&req->timeout_event); search_request_finished(req); global_requests_inflight--; if (!req->request_appended) { /* need to free the request data on it's own */ mm_free(req->request); } else { /* the request data is appended onto the header */ /* so everything gets mm_free()ed when we: */ } CLEAR(req); _mm_free(req); evdns_requests_pump_waiting_queue(); } /* This is called when a server returns a funny error code. */ /* We try the request again with another server. */ /* */ /* return: */ /* 0 ok */ /* 1 failed/reissue is pointless */ static int request_reissue(struct evdns_request *req) { const struct nameserver *const last_ns = req->ns; /* the last nameserver should have been marked as failing */ /* by the caller of this function, therefore pick will try */ /* not to return it */ req->ns = nameserver_pick(); if (req->ns == last_ns) { /* ... but pick did return it */ /* not a lot of point in trying again with the */ /* same server */ return 1; } req->reissue_count++; req->tx_count = 0; req->transmit_me = 1; return 0; } /* this function looks for space on the inflight queue and promotes */ /* requests from the waiting queue if it can. */ static void evdns_requests_pump_waiting_queue(void) { while (global_requests_inflight < global_max_requests_inflight && global_requests_waiting) { struct evdns_request *req; /* move a request from the waiting queue to the inflight queue */ assert(req_waiting_head); if (req_waiting_head->next == req_waiting_head) { /* only one item in the queue */ req = req_waiting_head; req_waiting_head = NULL; } else { req = req_waiting_head; req->next->prev = req->prev; req->prev->next = req->next; req_waiting_head = req->next; } global_requests_waiting--; global_requests_inflight++; req->ns = nameserver_pick(); request_trans_id_set(req, transaction_id_pick()); evdns_request_insert(req, &req_head); evdns_request_transmit(req); evdns_transmit(); } } static void reply_callback(struct evdns_request *const req, u32 ttl, u32 err, struct reply *reply) { switch (req->request_type) { case TYPE_A: if (reply) req->user_callback(DNS_ERR_NONE, DNS_IPv4_A, reply->data.a.addrcount, ttl, reply->data.a.addresses, req->user_pointer); else req->user_callback(err, 0, 0, 0, NULL, req->user_pointer); return; case TYPE_PTR: if (reply) { char *name = reply->data.ptr.name; req->user_callback(DNS_ERR_NONE, DNS_PTR, 1, ttl, &name, req->user_pointer); } else { req->user_callback(err, 0, 0, 0, NULL, req->user_pointer); } return; case TYPE_AAAA: if (reply) req->user_callback(DNS_ERR_NONE, DNS_IPv6_AAAA, reply->data.aaaa.addrcount, ttl, reply->data.aaaa.addresses, req->user_pointer); else req->user_callback(err, 0, 0, 0, NULL, req->user_pointer); return; } assert(0); } /* this processes a parsed reply packet */ static void reply_handle(struct evdns_request *const req, u16 flags, u32 ttl, struct reply *reply) { int error; static const int error_codes[] = {DNS_ERR_FORMAT, DNS_ERR_SERVERFAILED, DNS_ERR_NOTEXIST, DNS_ERR_NOTIMPL, DNS_ERR_REFUSED}; if (flags & 0x020f || !reply || !reply->have_answer) { /* there was an error */ if (flags & 0x0200) { error = DNS_ERR_TRUNCATED; } else { u16 error_code = (flags & 0x000f) - 1; if (error_code > 4) { error = DNS_ERR_UNKNOWN; } else { error = error_codes[error_code]; } } switch(error) { case DNS_ERR_NOTIMPL: case DNS_ERR_REFUSED: /* we regard these errors as marking a bad nameserver */ if (req->reissue_count < global_max_reissues) { char msg[64]; snprintf(msg, sizeof(msg), "Bad response %d (%s)", error, evdns_err_to_string(error)); nameserver_failed(req->ns, msg); if (!request_reissue(req)) return; } break; case DNS_ERR_SERVERFAILED: /* rcode 2 (servfailed) sometimes means "we are broken" and * sometimes (with some binds) means "that request was very * confusing." Treat this as a timeout, not a failure. */ /*XXXX refactor the parts of */ log(EVDNS_LOG_DEBUG, "Got a SERVERFAILED from nameserver %s; " "will allow the request to time out.", debug_ntop((struct sockaddr *)&req->ns->address)); break; default: /* we got a good reply from the nameserver */ nameserver_up(req->ns); } if (req->search_state && req->request_type != TYPE_PTR) { /* if we have a list of domains to search in, try the next one */ if (!search_try_next(req)) { /* a new request was issued so this request is finished and */ /* the user callback will be made when that request (or a */ /* child of it) finishes. */ request_finished(req, &req_head); return; } } /* all else failed. Pass the failure up */ reply_callback(req, 0, error, NULL); request_finished(req, &req_head); } else { /* all ok, tell the user */ reply_callback(req, ttl, 0, reply); nameserver_up(req->ns); request_finished(req, &req_head); } } static INLINE int name_parse(u8 *packet, int length, int *idx, char *name_out, size_t name_out_len) { int name_end = -1; int j = *idx; int ptr_count = 0; #define GET32(x) do { if (j + 4 > length) goto err; memcpy(&_t32, packet + j, 4); j += 4; x = ntohl(_t32); } while(0) #define GET16(x) do { if (j + 2 > length) goto err; memcpy(&_t, packet + j, 2); j += 2; x = ntohs(_t); } while(0) #define GET8(x) do { if (j >= length) goto err; x = packet[j++]; } while(0) char *cp = name_out; const char *const end = name_out + name_out_len; /* Normally, names are a series of length prefixed strings terminated */ /* with a length of 0 (the lengths are u8's < 63). */ /* However, the length can start with a pair of 1 bits and that */ /* means that the next 14 bits are a pointer within the current */ /* packet. */ for(;;) { u8 label_len; if (j >= length) return -1; GET8(label_len); if (!label_len) break; if (label_len & 0xc0) { u8 ptr_low; GET8(ptr_low); if (name_end < 0) name_end = j; j = (((int)label_len & 0x3f) << 8) + ptr_low; /* Make sure that the target offset is in-bounds. */ if (j < 0 || j >= length) return -1; /* If we've jumped more times than there are characters in the * message, we must have a loop. */ if (++ptr_count > length) return -1; continue; } if (label_len > 63) return -1; if (cp != name_out) { if (cp + 1 >= end) return -1; *cp++ = '.'; } if (cp + label_len >= end) return -1; memcpy(cp, packet + j, label_len); cp += label_len; j += label_len; } if (cp >= end) return -1; *cp = '\0'; if (name_end < 0) *idx = j; else *idx = name_end; return 0; err: return -1; } /* parses a raw reply from a nameserver. */ static int reply_parse(u8 *packet, int length) { int j = 0; /* index into packet */ int k; u16 _t; /* used by the macros */ u32 _t32; /* used by the macros */ char tmp_name[256], cmp_name[256]; /* used by the macros */ u16 trans_id, questions, answers, authority, additional, datalength; u16 flags = 0; u32 ttl, ttl_r = 0xffffffff; struct reply reply; struct evdns_request *req = NULL; unsigned int i; int name_matches = 0; GET16(trans_id); GET16(flags); GET16(questions); GET16(answers); GET16(authority); GET16(additional); (void) authority; /* suppress "unused variable" warnings. */ (void) additional; /* suppress "unused variable" warnings. */ req = request_find_from_trans_id(trans_id); /* if no request, can't do anything. */ if (!req) return -1; memset(&reply, 0, sizeof(reply)); /* If it's not an answer, it doesn't go with any of our requests. */ if (!(flags & 0x8000)) return -1; /* must be an answer */ if (flags & 0x020f) { /* there was an error */ goto err; } /* if (!answers) return; */ /* must have an answer of some form */ /* This macro skips a name in the DNS reply. */ #define GET_NAME \ do { tmp_name[0] = '\0'; \ if (name_parse(packet, length, &j, tmp_name, sizeof(tmp_name))<0)\ goto err; \ } while(0) #define TEST_NAME \ do { tmp_name[0] = '\0'; \ cmp_name[0] = '\0'; \ k = j; \ if (name_parse(packet, length, &j, tmp_name, sizeof(tmp_name))<0)\ goto err; \ if (name_parse(req->request, req->request_len, &k, cmp_name, sizeof(cmp_name))<0) \ goto err; \ if (global_randomize_case) { \ if (strcmp(tmp_name, cmp_name) == 0) \ name_matches = 1; /* we ignore mismatching names */ \ } else { \ if (strcasecmp(tmp_name, cmp_name) == 0) \ name_matches = 1; \ } \ } while(0) reply.type = req->request_type; /* skip over each question in the reply */ for (i = 0; i < questions; ++i) { /* the question looks like * */ TEST_NAME; j += 4; if (j >= length) goto err; } if (!name_matches) goto err; /* now we have the answer section which looks like * */ for (i = 0; i < answers; ++i) { u16 type, class; GET_NAME; GET16(type); GET16(class); GET32(ttl); GET16(datalength); if (type == TYPE_A && class == CLASS_INET) { int addrcount, addrtocopy; if (req->request_type != TYPE_A) { j += datalength; continue; } if ((datalength & 3) != 0) /* not an even number of As. */ goto err; addrcount = datalength >> 2; addrtocopy = MIN(MAX_ADDRS - reply.data.a.addrcount, (unsigned)addrcount); ttl_r = MIN(ttl_r, ttl); /* we only bother with the first four addresses. */ if (j + 4*addrtocopy > length) goto err; memcpy(&reply.data.a.addresses[reply.data.a.addrcount], packet + j, 4*addrtocopy); reply.data.a.addrcount += addrtocopy; reply.have_answer = 1; if (reply.data.a.addrcount == MAX_ADDRS) break; j += 4*addrtocopy; } else if (type == TYPE_PTR && class == CLASS_INET) { if (req->request_type != TYPE_PTR) { j += datalength; continue; } GET_NAME; strlcpy(reply.data.ptr.name, tmp_name, sizeof(reply.data.ptr.name)); ttl_r = MIN(ttl_r, ttl); reply.have_answer = 1; break; } else if (type == TYPE_AAAA && class == CLASS_INET) { int addrcount, addrtocopy; if (req->request_type != TYPE_AAAA) { j += datalength; continue; } if ((datalength & 15) != 0) /* not an even number of AAAAs. */ goto err; addrcount = datalength >> 4; /* each address is 16 bytes long */ addrtocopy = MIN(MAX_ADDRS - reply.data.aaaa.addrcount, (unsigned)addrcount); ttl_r = MIN(ttl_r, ttl); /* we only bother with the first four addresses. */ if (j + 16*addrtocopy > length) goto err; memcpy(&reply.data.aaaa.addresses[reply.data.aaaa.addrcount], packet + j, 16*addrtocopy); reply.data.aaaa.addrcount += addrtocopy; reply.have_answer = 1; if (reply.data.aaaa.addrcount == MAX_ADDRS) break; j += 16*addrtocopy; } else { /* skip over any other type of resource */ j += datalength; } } reply_handle(req, flags, ttl_r, &reply); return 0; err: if (req) reply_handle(req, flags, 0, NULL); return -1; } /* Parse a raw request (packet,length) sent to a nameserver port (port) from */ /* a DNS client (addr,addrlen), and if it's well-formed, call the corresponding */ /* callback. */ static int request_parse(u8 *packet, ssize_t length, struct evdns_server_port *port, struct sockaddr *addr, socklen_t addrlen) { int j = 0; /* index into packet */ u16 _t; /* used by the macros */ char tmp_name[256]; /* used by the macros */ int i; u16 trans_id, flags, questions, answers, authority, additional; struct server_request *server_req = NULL; /* Get the header fields */ GET16(trans_id); GET16(flags); GET16(questions); GET16(answers); GET16(authority); GET16(additional); if (flags & 0x8000) return -1; /* Must not be an answer. */ flags &= 0x0110; /* Only RD and CD get preserved. */ if (length > INT_MAX) return -1; server_req = mm_malloc(sizeof(struct server_request)); if (server_req == NULL) return -1; memset(server_req, 0, sizeof(struct server_request)); server_req->trans_id = trans_id; memcpy(&server_req->addr, addr, addrlen); server_req->addrlen = addrlen; server_req->base.flags = flags; server_req->base.nquestions = 0; server_req->base.questions = mm_malloc(sizeof(struct evdns_server_question *) * questions); if (server_req->base.questions == NULL) goto err; for (i = 0; i < questions; ++i) { u16 type, class; struct evdns_server_question *q; size_t namelen; if (name_parse(packet, (int)length, &j, tmp_name, sizeof(tmp_name))<0) goto err; GET16(type); GET16(class); namelen = strlen(tmp_name); q = mm_malloc(sizeof(struct evdns_server_question) + namelen); if (!q) goto err; q->type = type; q->dns_question_class = class; memcpy(q->name, tmp_name, namelen+1); server_req->base.questions[server_req->base.nquestions++] = q; } /* Ignore answers, authority, and additional. */ server_req->port = port; port->refcnt++; /* Only standard queries are supported. */ if (flags & 0x7800) { evdns_server_request_respond(&(server_req->base), DNS_ERR_NOTIMPL); return -1; } port->user_callback(&(server_req->base), port->user_data); return 0; err: if (server_req) { if (server_req->base.questions) { for (i = 0; i < server_req->base.nquestions; ++i) mm_free(server_req->base.questions[i]); mm_free(server_req->base.questions); } CLEAR(server_req); mm_free(server_req); } return -1; #undef SKIP_NAME #undef GET32 #undef GET16 #undef GET8 } static uint16_t default_transaction_id_fn(void) { u16 trans_id; #ifdef DNS_USE_CPU_CLOCK_FOR_ID struct timespec ts; #ifdef CLOCK_MONOTONIC if (clock_gettime(CLOCK_MONOTONIC, &ts) == -1) #else if (clock_gettime(CLOCK_REALTIME, &ts) == -1) #endif event_err(1, "clock_gettime"); trans_id = ts.tv_nsec & 0xffff; #endif #ifdef DNS_USE_GETTIMEOFDAY_FOR_ID struct timeval tv; gettimeofday(&tv, NULL); trans_id = tv.tv_usec & 0xffff; #endif #ifdef DNS_USE_OPENSSL_FOR_ID if (RAND_pseudo_bytes((u8 *) &trans_id, 2) == -1) { /* in the case that the RAND call fails we back */ /* down to using gettimeofday. */ /* struct timeval tv; gettimeofday(&tv, NULL); trans_id = tv.tv_usec & 0xffff; */ abort(); } #endif return (unsigned short) trans_id; } static uint16_t (*trans_id_function)(void) = default_transaction_id_fn; static void default_random_bytes_fn(char *buf, size_t n) { unsigned i; for (i = 0; i < n; i += 2) { u16 tid = trans_id_function(); buf[i] = (tid >> 8) & 0xff; if (i+1trans_id == trans_id) break; req = req->next; } while (req != started_at); } /* we didn't find it, so this is a good id */ if (req == started_at) return trans_id; } } /* choose a namesever to use. This function will try to ignore */ /* nameservers which we think are down and load balance across the rest */ /* by updating the server_head global each time. */ static struct nameserver * nameserver_pick(void) { struct nameserver *started_at = server_head, *picked; if (!server_head) return NULL; /* if we don't have any good nameservers then there's no */ /* point in trying to find one. */ if (!global_good_nameservers) { server_head = server_head->next; return server_head; } /* remember that nameservers are in a circular list */ for (;;) { if (server_head->state) { /* we think this server is currently good */ picked = server_head; server_head = server_head->next; return picked; } server_head = server_head->next; if (server_head == started_at) { /* all the nameservers seem to be down */ /* so we just return this one and hope for the */ /* best */ assert(global_good_nameservers == 0); picked = server_head; server_head = server_head->next; return picked; } } } /* this is called when a namesever socket is ready for reading */ static void nameserver_read(struct nameserver *ns) { struct sockaddr_storage ss; struct sockaddr *sa = (struct sockaddr *) &ss; socklen_t addrlen = sizeof(ss); u8 packet[1500]; for (;;) { const int r = (int)recvfrom(ns->socket, packet, (socklen_t)sizeof(packet), 0, sa, &addrlen); if (r < 0) { int err = last_error(ns->socket); if (error_is_eagain(err)) return; nameserver_failed(ns, tor_socket_strerror(err)); return; } /* XXX Match port too? */ if (!sockaddr_eq(sa, (struct sockaddr*)&ns->address, 0)) { log(EVDNS_LOG_WARN, "Address mismatch on received DNS packet. Address was %s", debug_ntop(sa)); return; } ns->timedout = 0; reply_parse(packet, r); } } /* Read a packet from a DNS client on a server port s, parse it, and */ /* act accordingly. */ static void server_port_read(struct evdns_server_port *s) { u8 packet[1500]; struct sockaddr_storage addr; socklen_t addrlen; ssize_t r; for (;;) { addrlen = (socklen_t)sizeof(struct sockaddr_storage); r = recvfrom(s->socket, packet, sizeof(packet), 0, (struct sockaddr*) &addr, &addrlen); if (r < 0) { int err = last_error(s->socket); if (error_is_eagain(err)) return; log(EVDNS_LOG_WARN, "Error %s (%d) while reading request.", tor_socket_strerror(err), err); return; } request_parse(packet, r, s, (struct sockaddr*) &addr, addrlen); } } /* Try to write all pending replies on a given DNS server port. */ static void server_port_flush(struct evdns_server_port *port) { while (port->pending_replies) { struct server_request *req = port->pending_replies; ssize_t r = sendto(port->socket, req->response, req->response_len, 0, (struct sockaddr*) &req->addr, (socklen_t)req->addrlen); if (r < 0) { int err = last_error(port->socket); if (error_is_eagain(err)) return; log(EVDNS_LOG_WARN, "Error %s (%d) while writing response to port; dropping", tor_socket_strerror(err), err); } if (server_request_free(req)) { /* we released the last reference to req->port. */ return; } } /* We have no more pending requests; stop listening for 'writeable' events. */ (void) event_del(&port->event); CLEAR(&port->event); event_set(&port->event, port->socket, EV_READ | EV_PERSIST, server_port_ready_callback, port); if (event_add(&port->event, NULL) < 0) { log(EVDNS_LOG_WARN, "Error from libevent when adding event for DNS server."); /* ???? Do more? */ } } /* set if we are waiting for the ability to write to this server. */ /* if waiting is true then we ask libevent for EV_WRITE events, otherwise */ /* we stop these events. */ static void nameserver_write_waiting(struct nameserver *ns, char waiting) { if (ns->write_waiting == waiting) return; ns->write_waiting = waiting; (void) event_del(&ns->event); CLEAR(&ns->event); event_set(&ns->event, ns->socket, EV_READ | (waiting ? EV_WRITE : 0) | EV_PERSIST, nameserver_ready_callback, ns); if (event_add(&ns->event, NULL) < 0) { log(EVDNS_LOG_WARN, "Error from libevent when adding event for %s", debug_ntop((struct sockaddr *)&ns->address)); /* ???? Do more? */ } } /* a callback function. Called by libevent when the kernel says that */ /* a nameserver socket is ready for writing or reading */ static void nameserver_ready_callback(int fd, short events, void *arg) { struct nameserver *ns = (struct nameserver *) arg; (void)fd; if (events & EV_WRITE) { ns->choked = 0; if (!evdns_transmit()) { nameserver_write_waiting(ns, 0); } } if (events & EV_READ) { nameserver_read(ns); } } /* a callback function. Called by libevent when the kernel says that */ /* a server socket is ready for writing or reading. */ static void server_port_ready_callback(int fd, short events, void *arg) { struct evdns_server_port *port = (struct evdns_server_port *) arg; (void) fd; if (events & EV_WRITE) { port->choked = 0; server_port_flush(port); } if (events & EV_READ) { server_port_read(port); } } /* This is an inefficient representation; only use it via the dnslabel_table_* * functions, so that is can be safely replaced with something smarter later. */ #define MAX_LABELS 128 /* Structures used to implement name compression */ struct dnslabel_entry { char *v; off_t pos; }; struct dnslabel_table { int n_labels; /* number of current entries */ /* map from name to position in message */ struct dnslabel_entry labels[MAX_LABELS]; }; /* Initialize dnslabel_table. */ static void dnslabel_table_init(struct dnslabel_table *table) { table->n_labels = 0; } /* Free all storage held by table, but not the table itself. */ static void dnslabel_clear(struct dnslabel_table *table) { int i; for (i = 0; i < table->n_labels; ++i) mm_free(table->labels[i].v); table->n_labels = 0; } /* return the position of the label in the current message, or -1 if the label */ /* hasn't been used yet. */ static int dnslabel_table_get_pos(const struct dnslabel_table *table, const char *label) { int i; for (i = 0; i < table->n_labels; ++i) { if (!strcmp(label, table->labels[i].v)) { off_t pos = table->labels[i].pos; if (pos > 65535) return -1; return (int)pos; } } return -1; } /* remember that we've used the label at position pos */ static int dnslabel_table_add(struct dnslabel_table *table, const char *label, off_t pos) { char *v; int p; if (table->n_labels == MAX_LABELS) return (-1); v = mm_strdup(label); if (v == NULL) return (-1); p = table->n_labels++; table->labels[p].v = v; table->labels[p].pos = pos; return (0); } /* Converts a string to a length-prefixed set of DNS labels, starting */ /* at buf[j]. name and buf must not overlap. name_len should be the length */ /* of name. table is optional, and is used for compression. */ /* */ /* Input: abc.def */ /* Output: <3>abc<3>def<0> */ /* */ /* Returns the first index after the encoded name, or negative on error. */ /* -1 label was > 63 bytes */ /* -2 name too long to fit in buffer. */ /* */ static off_t dnsname_to_labels(u8 *const buf, size_t buf_len, off_t j, const char *name, const size_t name_len, struct dnslabel_table *table) { const char *end = name + name_len; int ref = 0; u16 _t; #define APPEND16(x) do { \ if (j + 2 > (off_t)buf_len) \ goto overflow; \ _t = htons(x); \ memcpy(buf + j, &_t, 2); \ j += 2; \ } while (0) #define APPEND32(x) do { \ if (j + 4 > (off_t)buf_len) \ goto overflow; \ _t32 = htonl(x); \ memcpy(buf + j, &_t32, 4); \ j += 4; \ } while (0) if (name_len > 255) return -2; for (;;) { const char *const start = name; if (table && (ref = dnslabel_table_get_pos(table, name)) >= 0) { APPEND16(ref | 0xc000); return j; } name = strchr(name, '.'); if (!name) { const size_t label_len = end - start; if (label_len > 63) return -1; if ((size_t)(j+label_len+1) > buf_len) return -2; if (table) dnslabel_table_add(table, start, j); buf[j++] = (uint8_t)label_len; memcpy(buf + j, start, label_len); j += end - start; break; } else { /* append length of the label. */ const size_t label_len = name - start; if (label_len > 63) return -1; if ((size_t)(j+label_len+1) > buf_len) return -2; if (table) dnslabel_table_add(table, start, j); buf[j++] = (uint8_t)label_len; memcpy(buf + j, start, name - start); j += name - start; /* hop over the '.' */ name++; } } /* the labels must be terminated by a 0. */ /* It's possible that the name ended in a . */ /* in which case the zero is already there */ if (!j || buf[j-1]) buf[j++] = 0; return j; overflow: return (-2); } /* Finds the length of a dns request for a DNS name of the given */ /* length. The actual request may be smaller than the value returned */ /* here */ static size_t evdns_request_len(const size_t name_len) { return 96 + /* length of the DNS standard header */ name_len + 2 + 4; /* space for the resource type */ } /* build a dns request packet into buf. buf should be at least as long */ /* as evdns_request_len told you it should be. */ /* */ /* Returns the amount of space used. Negative on error. */ static int evdns_request_data_build(const char *const name, const size_t name_len, const u16 trans_id, const u16 type, const u16 class, u8 *const buf, size_t buf_len) { off_t j = 0; /* current offset into buf */ u16 _t; /* used by the macros */ APPEND16(trans_id); APPEND16(0x0100); /* standard query, recusion needed */ APPEND16(1); /* one question */ APPEND16(0); /* no answers */ APPEND16(0); /* no authority */ APPEND16(0); /* no additional */ j = dnsname_to_labels(buf, buf_len, j, name, name_len, NULL); if (j < 0) { return (int)j; } APPEND16(type); APPEND16(class); return (int)j; overflow: return (-1); } /* exported function */ struct evdns_server_port * evdns_add_server_port(int socket, int is_tcp, evdns_request_callback_fn_type cb, void *user_data) { struct evdns_server_port *port; if (!(port = mm_malloc(sizeof(struct evdns_server_port)))) return NULL; memset(port, 0, sizeof(struct evdns_server_port)); assert(!is_tcp); /* TCP sockets not yet implemented */ port->socket = socket; port->refcnt = 1; port->choked = 0; port->closing = 0; port->user_callback = cb; port->user_data = user_data; port->pending_replies = NULL; event_set(&port->event, port->socket, EV_READ | EV_PERSIST, server_port_ready_callback, port); if (event_add(&port->event, NULL)<0) { mm_free(port); return NULL; } return port; } /* exported function */ void evdns_close_server_port(struct evdns_server_port *port) { port->closing = 1; if (--port->refcnt == 0) server_port_free(port); } /* exported function */ int evdns_server_request_add_reply(struct evdns_server_request *_req, int section, const char *name, int type, int class, int ttl, int datalen, int is_name, const char *data) { struct server_request *req = TO_SERVER_REQUEST(_req); struct server_reply_item **itemp, *item; int *countp; if (req->response) /* have we already answered? */ return (-1); switch (section) { case EVDNS_ANSWER_SECTION: itemp = &req->answer; countp = &req->n_answer; break; case EVDNS_AUTHORITY_SECTION: itemp = &req->authority; countp = &req->n_authority; break; case EVDNS_ADDITIONAL_SECTION: itemp = &req->additional; countp = &req->n_additional; break; default: return (-1); } while (*itemp) { itemp = &((*itemp)->next); } item = mm_malloc(sizeof(struct server_reply_item)); if (!item) return -1; CLEAR(item); item->next = NULL; if (!(item->name = mm_strdup(name))) { CLEAR(item); mm_free(item); return -1; } item->type = type; item->class = class; item->ttl = ttl; item->is_name = is_name != 0; item->datalen = 0; item->data = NULL; if (data) { if (item->is_name) { if (!(item->data = mm_strdup(data))) { mm_free(item->name); CLEAR(item); mm_free(item); return -1; } item->datalen = (u16)-1; } else { if (!(item->data = mm_malloc(datalen))) { mm_free(item->name); CLEAR(item); mm_free(item); return -1; } item->datalen = datalen; memcpy(item->data, data, datalen); } } *itemp = item; ++(*countp); return 0; } /* exported function */ int evdns_server_request_add_a_reply(struct evdns_server_request *req, const char *name, int n, void *addrs, int ttl) { return evdns_server_request_add_reply( req, EVDNS_ANSWER_SECTION, name, TYPE_A, CLASS_INET, ttl, n*4, 0, addrs); } /* exported function */ int evdns_server_request_add_aaaa_reply(struct evdns_server_request *req, const char *name, int n, void *addrs, int ttl) { return evdns_server_request_add_reply( req, EVDNS_ANSWER_SECTION, name, TYPE_AAAA, CLASS_INET, ttl, n*16, 0, addrs); } /* exported function */ int evdns_server_request_add_ptr_reply(struct evdns_server_request *req, struct in_addr *in, const char *inaddr_name, const char *hostname, int ttl) { u32 a; char buf[32]; assert(in || inaddr_name); assert(!(in && inaddr_name)); if (in) { a = ntohl(in->s_addr); snprintf(buf, sizeof(buf), "%d.%d.%d.%d.in-addr.arpa", (int)(u8)((a )&0xff), (int)(u8)((a>>8 )&0xff), (int)(u8)((a>>16)&0xff), (int)(u8)((a>>24)&0xff)); inaddr_name = buf; } return evdns_server_request_add_reply( req, EVDNS_ANSWER_SECTION, inaddr_name, TYPE_PTR, CLASS_INET, ttl, -1, 1, hostname); } /* exported function */ int evdns_server_request_add_cname_reply(struct evdns_server_request *req, const char *name, const char *cname, int ttl) { return evdns_server_request_add_reply( req, EVDNS_ANSWER_SECTION, name, TYPE_CNAME, CLASS_INET, ttl, -1, 1, cname); } static int evdns_server_request_format_response(struct server_request *req, int err) { unsigned char buf[1500]; size_t buf_len = sizeof(buf); off_t j = 0, r; u16 _t; u32 _t32; int i; u16 flags; struct dnslabel_table table; if (err < 0 || err > 15) return -1; /* Set response bit and error code; copy OPCODE and RD fields from * question; copy RA and AA if set by caller. */ flags = req->base.flags; flags |= (0x8000 | err); dnslabel_table_init(&table); APPEND16(req->trans_id); APPEND16(flags); APPEND16(req->base.nquestions); APPEND16(req->n_answer); APPEND16(req->n_authority); APPEND16(req->n_additional); /* Add questions. */ for (i=0; i < req->base.nquestions; ++i) { const char *s = req->base.questions[i]->name; j = dnsname_to_labels(buf, buf_len, j, s, strlen(s), &table); if (j < 0) { dnslabel_clear(&table); return (int) j; } APPEND16(req->base.questions[i]->type); APPEND16(req->base.questions[i]->dns_question_class); } /* Add answer, authority, and additional sections. */ for (i=0; i<3; ++i) { struct server_reply_item *item; if (i==0) item = req->answer; else if (i==1) item = req->authority; else item = req->additional; while (item) { r = dnsname_to_labels(buf, buf_len, j, item->name, strlen(item->name), &table); if (r < 0) goto overflow; j = r; APPEND16(item->type); APPEND16(item->class); APPEND32(item->ttl); if (item->is_name) { off_t len_idx = j, name_start; j += 2; name_start = j; r = dnsname_to_labels(buf, buf_len, j, item->data, strlen(item->data), &table); if (r < 0) goto overflow; j = r; _t = htons( (j-name_start) ); memcpy(buf+len_idx, &_t, 2); } else { APPEND16(item->datalen); if (j+item->datalen > (off_t)buf_len) goto overflow; memcpy(buf+j, item->data, item->datalen); j += item->datalen; } item = item->next; } } if (j > 512) { overflow: j = 512; buf[2] |= 0x02; /* set the truncated bit. */ } req->response_len = (size_t)j; if (!(req->response = mm_malloc(req->response_len))) { server_request_free_answers(req); dnslabel_clear(&table); return (-1); } memcpy(req->response, buf, req->response_len); server_request_free_answers(req); dnslabel_clear(&table); return (0); } /* exported function */ int evdns_server_request_respond(struct evdns_server_request *_req, int err) { struct server_request *req = TO_SERVER_REQUEST(_req); struct evdns_server_port *port = req->port; ssize_t r; if (!req->response) { if ((r = evdns_server_request_format_response(req, err))<0) return (int)r; } r = sendto(port->socket, req->response, req->response_len, 0, (struct sockaddr*) &req->addr, req->addrlen); if (r<0) { int err = last_error(port->socket); if (! error_is_eagain(err)) return -1; if (port->pending_replies) { req->prev_pending = port->pending_replies->prev_pending; req->next_pending = port->pending_replies; req->prev_pending->next_pending = req->next_pending->prev_pending = req; } else { req->prev_pending = req->next_pending = req; port->pending_replies = req; port->choked = 1; (void) event_del(&port->event); CLEAR(&port->event); event_set(&port->event, port->socket, (port->closing?0:EV_READ) | EV_WRITE | EV_PERSIST, server_port_ready_callback, port); if (event_add(&port->event, NULL) < 0) { log(EVDNS_LOG_WARN, "Error from libevent when adding event for DNS server"); } } return 1; } if (server_request_free(req)) return 0; if (port->pending_replies) server_port_flush(port); return 0; } /* Free all storage held by RRs in req. */ static void server_request_free_answers(struct server_request *req) { struct server_reply_item *victim, *next, **list; int i; for (i = 0; i < 3; ++i) { if (i==0) list = &req->answer; else if (i==1) list = &req->authority; else list = &req->additional; victim = *list; while (victim) { next = victim->next; mm_free(victim->name); if (victim->data) mm_free(victim->data); mm_free(victim); victim = next; } *list = NULL; } } /* Free all storage held by req, and remove links to it. */ /* return true iff we just wound up freeing the server_port. */ static int server_request_free(struct server_request *req) { int i, rc=1; if (req->base.questions) { for (i = 0; i < req->base.nquestions; ++i) mm_free(req->base.questions[i]); mm_free(req->base.questions); } if (req->port) { if (req->port->pending_replies == req) { if (req->next_pending) req->port->pending_replies = req->next_pending; else req->port->pending_replies = NULL; } rc = --req->port->refcnt; } if (req->response) { mm_free(req->response); } server_request_free_answers(req); if (req->next_pending && req->next_pending != req) { req->next_pending->prev_pending = req->prev_pending; req->prev_pending->next_pending = req->next_pending; } if (rc == 0) { server_port_free(req->port); CLEAR(req); mm_free(req); return (1); } CLEAR(req); mm_free(req); return (0); } /* Free all storage held by an evdns_server_port. Only called when the * reference count is down to 0. */ static void server_port_free(struct evdns_server_port *port) { assert(port); assert(!port->refcnt); assert(!port->pending_replies); if (port->socket > 0) { CLOSE_SOCKET(port->socket); port->socket = -1; } (void) event_del(&port->event); CLEAR(&port->event); CLEAR(port); mm_free(port); } /* exported function */ int evdns_server_request_drop(struct evdns_server_request *_req) { struct server_request *req = TO_SERVER_REQUEST(_req); server_request_free(req); return 0; } /* exported function */ int evdns_server_request_get_requesting_addr(struct evdns_server_request *_req, struct sockaddr *sa, int addr_len) { struct server_request *req = TO_SERVER_REQUEST(_req); if (addr_len < (int)req->addrlen) return -1; memcpy(sa, &(req->addr), req->addrlen); return req->addrlen; } #undef APPEND16 #undef APPEND32 /* this is a libevent callback function which is called when a request */ /* has timed out. */ static void evdns_request_timeout_callback(int fd, short events, void *arg) { struct evdns_request *const req = (struct evdns_request *) arg; (void) fd; (void) events; log(EVDNS_LOG_DEBUG, "Request %lx timed out", (unsigned long) arg); req->ns->timedout++; if (req->ns->timedout > global_max_nameserver_timeout) { req->ns->timedout = 0; nameserver_failed(req->ns, "request timed out."); } if (req->tx_count >= global_max_retransmits) { /* this request has failed */ reply_callback(req, 0, DNS_ERR_TIMEOUT, NULL); request_finished(req, &req_head); } else { /* retransmit it */ /* Stop waiting for the timeout. No need to do this in * request_finished; that one already deletes the timeout event. * XXXX021 port this change to libevent. */ del_timeout_event(req); CLEAR(&req->timeout_event); evdns_request_transmit(req); } } /* try to send a request to a given server. */ /* */ /* return: */ /* 0 ok */ /* 1 temporary failure */ /* 2 other failure */ static int evdns_request_transmit_to(struct evdns_request *req, struct nameserver *server) { const ssize_t r = send(server->socket, req->request, req->request_len, 0); if (r < 0) { int err = last_error(server->socket); if (error_is_eagain(err)) return 1; nameserver_failed(req->ns, tor_socket_strerror(err)); return 2; } else if (r != (ssize_t)req->request_len) { return 1; /* short write */ } else { return 0; } } /* try to send a request, updating the fields of the request */ /* as needed */ /* */ /* return: */ /* 0 ok */ /* 1 failed */ static int evdns_request_transmit(struct evdns_request *req) { int retcode = 0, r; /* if we fail to send this packet then this flag marks it */ /* for evdns_transmit */ req->transmit_me = 1; if (req->trans_id == 0xffff) abort(); if (req->ns->choked) { /* don't bother trying to write to a socket */ /* which we have had EAGAIN from */ return 1; } r = evdns_request_transmit_to(req, req->ns); switch (r) { case 1: /* temp failure */ req->ns->choked = 1; nameserver_write_waiting(req->ns, 1); return 1; case 2: /* failed to transmit the request entirely. */ retcode = 1; /* fall through: we'll set a timeout, which will time out, * and make us retransmit the request anyway. */ default: /* transmitted; we need to check for timeout. */ log(EVDNS_LOG_DEBUG, "Setting timeout for request %lx", (unsigned long) req); del_timeout_event_if_set(req); evtimer_set(&req->timeout_event, evdns_request_timeout_callback, req); if (add_timeout_event(req, &global_timeout) < 0) { log(EVDNS_LOG_WARN, "Error from libevent when adding timer for request %lx", (unsigned long) req); /* ???? Do more? */ } req->tx_count++; req->transmit_me = 0; return retcode; } } static void nameserver_probe_callback(int result, char type, int count, int ttl, void *addresses, void *arg) { struct sockaddr *addr = arg; struct nameserver *server; (void) type; (void) count; (void) ttl; (void) addresses; for (server = server_head; server; server = server->next) { if (sockaddr_eq(addr, (struct sockaddr*) &server->address, 1)) { if (result == DNS_ERR_NONE || result == DNS_ERR_NOTEXIST) { /* this is a good reply */ nameserver_up(server); } else { nameserver_probe_failed(server); } } if (server->next == server_head) break; } mm_free(addr); } static void nameserver_send_probe(struct nameserver *const ns) { struct evdns_request *req; struct sockaddr_storage *addr; /* here we need to send a probe to a given nameserver */ /* in the hope that it is up now. */ /* We identify the nameserver by its address, in case it is removed before * our probe comes back. */ addr = mm_malloc(sizeof(struct sockaddr_storage)); memcpy(addr, &ns->address, sizeof(struct sockaddr_storage)); log(EVDNS_LOG_DEBUG, "Sending probe to %s", debug_ntop((struct sockaddr *)&ns->address)); req = request_new(TYPE_A, "www.google.com", DNS_QUERY_NO_SEARCH, nameserver_probe_callback, addr); if (!req) { mm_free(addr); return; } /* we force this into the inflight queue no matter what */ request_trans_id_set(req, transaction_id_pick()); req->ns = ns; request_submit(req); } /* returns: */ /* 0 didn't try to transmit anything */ /* 1 tried to transmit something */ static int evdns_transmit(void) { char did_try_to_transmit = 0; if (req_head) { struct evdns_request *const started_at = req_head, *req = req_head; /* first transmit all the requests which are currently waiting */ do { if (req->transmit_me) { did_try_to_transmit = 1; evdns_request_transmit(req); } req = req->next; } while (req != started_at); } return did_try_to_transmit; } /* exported function */ int evdns_count_nameservers(void) { const struct nameserver *server = server_head; int n = 0; if (!server) return 0; do { ++n; server = server->next; } while (server != server_head); return n; } /* exported function */ int evdns_clear_nameservers_and_suspend(void) { struct nameserver *server = server_head, *started_at = server_head; struct evdns_request *req = req_head, *req_started_at = req_head; if (!server) return 0; while (1) { struct nameserver *next = server->next; (void) event_del(&server->event); CLEAR(&server->event); del_timeout_event(server); CLEAR(&server->timeout_event); if (server->socket >= 0) CLOSE_SOCKET(server->socket); CLEAR(server); mm_free(server); if (next == started_at) break; server = next; } server_head = NULL; global_good_nameservers = 0; while (req) { struct evdns_request *next = req->next; req->tx_count = req->reissue_count = 0; req->ns = NULL; /* ???? What to do about searches? */ del_timeout_event(req); CLEAR(&req->timeout_event); req->trans_id = 0; req->transmit_me = 0; global_requests_waiting++; evdns_request_insert(req, &req_waiting_head); /* We want to insert these suspended elements at the front of * the waiting queue, since they were pending before any of * the waiting entries were added. This is a circular list, * so we can just shift the start back by one.*/ req_waiting_head = req_waiting_head->prev; if (next == req_started_at) break; req = next; } req_head = NULL; global_requests_inflight = 0; return 0; } static struct sockaddr_storage global_bind_address; static socklen_t global_bind_addrlen = 0; static int global_bind_addr_is_set = 0; void evdns_set_default_outgoing_bind_address(const struct sockaddr *addr, socklen_t addrlen) { memset(&global_bind_address, 0, sizeof(global_bind_address)); if (addr) { assert(addrlen <= (socklen_t)sizeof(global_bind_address)); memcpy(&global_bind_address, addr, addrlen); global_bind_addrlen = addrlen; global_bind_addr_is_set = 1; } else { global_bind_addr_is_set = 0; } } /* exported function */ int evdns_resume(void) { evdns_requests_pump_waiting_queue(); return 0; } static int _evdns_nameserver_add_impl(const struct sockaddr *address, socklen_t addrlen) { /* first check to see if we already have this nameserver */ const struct nameserver *server = server_head, *const started_at = server_head; struct nameserver *ns; int err = 0; if (server) { do { if (sockaddr_eq(address, (struct sockaddr *)&server->address, 1)) { log(EVDNS_LOG_DEBUG, "Duplicate nameserver."); return 3; } server = server->next; } while (server != started_at); } if (addrlen > (int)sizeof(ns->address)) { log(EVDNS_LOG_DEBUG, "Addrlen %d too long.", (int)addrlen); return 2; } ns = (struct nameserver *) mm_malloc(sizeof(struct nameserver)); if (!ns) return -1; memset(ns, 0, sizeof(struct nameserver)); ns->timeout_event_deleted = __LINE__; ns->socket = socket(PF_INET, SOCK_DGRAM, 0); if (ns->socket < 0) { err = 1; goto out1; } #ifdef WIN32 { u_long nonblocking = 1; ioctlsocket(ns->socket, FIONBIO, &nonblocking); } #else fcntl(ns->socket, F_SETFL, O_NONBLOCK); #endif if (global_bind_addr_is_set) { if (bind(ns->socket, (struct sockaddr *)&global_bind_address, global_bind_addrlen) < 0) { log(EVDNS_LOG_DEBUG, "Couldn't bind to outgoing address."); err = 2; goto out2; } } if (connect(ns->socket, address, addrlen) != 0) { log(EVDNS_LOG_DEBUG, "Couldn't open socket to nameserver."); err = 2; goto out2; } memcpy(&ns->address, address, addrlen); ns->state = 1; event_set(&ns->event, ns->socket, EV_READ | EV_PERSIST, nameserver_ready_callback, ns); if (event_add(&ns->event, NULL) < 0) { log(EVDNS_LOG_DEBUG, "Couldn't add event for nameserver."); err = 2; goto out2; } log(EVDNS_LOG_DEBUG, "Added nameserver %s", debug_ntop(address)); /* insert this nameserver into the list of them */ if (!server_head) { ns->next = ns->prev = ns; server_head = ns; } else { ns->next = server_head->next; ns->prev = server_head; server_head->next = ns; if (server_head->prev == server_head) { server_head->prev = ns; } } global_good_nameservers++; return 0; out2: CLOSE_SOCKET(ns->socket); out1: CLEAR(ns); mm_free(ns); log(EVDNS_LOG_WARN, "Unable to add nameserver %s: error %d", debug_ntop(address), err); return err; } /* exported function */ int evdns_nameserver_add(uint32_t address) { struct sockaddr_in sin; memset(&sin, 0, sizeof(sin)); sin.sin_family = AF_INET; #ifdef HAVE_STRUCT_SOCKADDR_IN_SIN_LEN sin.sin_len = sizeof(sin); #endif sin.sin_addr.s_addr = htonl(address); sin.sin_port = 53; return _evdns_nameserver_add_impl((struct sockaddr*) &sin, sizeof(sin)); } /* exported function */ int evdns_nameserver_ip_add(const char *ip_as_string) { int port; char buf[128]; const char *cp, *addr_part, *port_part; int is_ipv6; /* recognized formats are: * [ipv6]:port * ipv6 * [ipv6] * ipv4:port * ipv4 */ log(EVDNS_LOG_DEBUG, "Trying to add nameserver <%s>", ip_as_string); cp = strchr(ip_as_string, ':'); if (*ip_as_string == '[') { size_t len; if (!(cp = strchr(ip_as_string, ']'))) { log(EVDNS_LOG_DEBUG, "Nameserver missing closing ]"); return 4; } len = cp-(ip_as_string + 1); if (len > sizeof(buf)-1) { log(EVDNS_LOG_DEBUG, "[Nameserver] does not fit in buffer."); return 4; } memcpy(buf, ip_as_string+1, len); buf[len] = '\0'; addr_part = buf; if (cp[1] == ':') port_part = cp+2; else port_part = NULL; is_ipv6 = 1; } else if (cp && strchr(cp+1, ':')) { is_ipv6 = 1; addr_part = ip_as_string; port_part = NULL; } else if (cp) { is_ipv6 = 0; if (cp - ip_as_string > (int)sizeof(buf)-1) { log(EVDNS_LOG_DEBUG, "Nameserver does not fit in buffer."); return 4; } memcpy(buf, ip_as_string, cp-ip_as_string); buf[cp-ip_as_string] = '\0'; addr_part = buf; port_part = cp+1; } else { addr_part = ip_as_string; port_part = NULL; is_ipv6 = 0; } if (port_part == NULL) { port = 53; } else { port = strtoint(port_part); if (port <= 0 || port > 65535) { log(EVDNS_LOG_DEBUG, "Nameserver port <%s> out of range", port_part); return 4; } } /* Tor-only. needs a more general fix. */ assert(addr_part); if (is_ipv6) { struct sockaddr_in6 sin6; memset(&sin6, 0, sizeof(sin6)); #ifdef HAVE_STRUCT_SOCKADDR_IN6_SIN6_LEN sin6.sin6_len = sizeof(sin6); #endif sin6.sin6_family = AF_INET6; sin6.sin6_port = htons(port); if (1 != tor_inet_pton(AF_INET6, addr_part, &sin6.sin6_addr)) { log(EVDNS_LOG_DEBUG, "inet_pton(%s) failed", addr_part); return 4; } return _evdns_nameserver_add_impl((struct sockaddr*)&sin6, sizeof(sin6)); } else { struct sockaddr_in sin; memset(&sin, 0, sizeof(sin)); #ifdef HAVE_STRUCT_SOCKADDR_IN_SIN_LEN sin.sin_len = sizeof(sin); #endif sin.sin_family = AF_INET; sin.sin_port = htons(port); if (!inet_aton(addr_part, &sin.sin_addr)) { log(EVDNS_LOG_DEBUG, "inet_pton(%s) failed", addr_part); return 4; } return _evdns_nameserver_add_impl((struct sockaddr*)&sin, sizeof(sin)); } } int evdns_nameserver_sockaddr_add(const struct sockaddr *sa, socklen_t len) { return _evdns_nameserver_add_impl(sa, len); } /* insert into the tail of the queue */ static void evdns_request_insert(struct evdns_request *req, struct evdns_request **head) { if (!*head) { *head = req; req->next = req->prev = req; return; } req->prev = (*head)->prev; req->prev->next = req; req->next = *head; (*head)->prev = req; } static int string_num_dots(const char *s) { int count = 0; while ((s = strchr(s, '.'))) { s++; count++; } return count; } static struct evdns_request * request_new(int type, const char *name, int flags, evdns_callback_type callback, void *user_ptr) { const char issuing_now = (global_requests_inflight < global_max_requests_inflight) ? 1 : 0; const size_t name_len = strlen(name); const size_t request_max_len = evdns_request_len(name_len); const u16 trans_id = issuing_now ? transaction_id_pick() : 0xffff; /* the request data is alloced in a single block with the header */ struct evdns_request *const req = (struct evdns_request *) mm_malloc(sizeof(struct evdns_request) + request_max_len); char namebuf[256]; int rlen; (void) flags; if (!req) return NULL; if (name_len >= sizeof(namebuf)) { _mm_free(req); return NULL; } memset(req, 0, sizeof(struct evdns_request)); req->timeout_event_deleted = __LINE__; if (global_randomize_case) { unsigned i; char randbits[32]; strlcpy(namebuf, name, sizeof(namebuf)); rand_bytes_function(randbits, (name_len+7)/8); for (i = 0; i < name_len; ++i) { if (ISALPHA(namebuf[i])) { if ((randbits[i >> 3] & (1<<(i%7)))) namebuf[i] = TOLOWER(namebuf[i]); else namebuf[i] = TOUPPER(namebuf[i]); } } name = namebuf; } /* request data lives just after the header */ req->request = ((u8 *) req) + sizeof(struct evdns_request); /* denotes that the request data shouldn't be mm_free()ed */ req->request_appended = 1; rlen = evdns_request_data_build(name, name_len, trans_id, type, CLASS_INET, req->request, request_max_len); if (rlen < 0) goto err1; req->request_len = rlen; req->trans_id = trans_id; req->tx_count = 0; req->request_type = type; req->user_pointer = user_ptr; req->user_callback = callback; req->ns = issuing_now ? nameserver_pick() : NULL; req->next = req->prev = NULL; return req; err1: CLEAR(req); _mm_free(req); return NULL; } static void request_submit(struct evdns_request *const req) { if (req->ns) { /* if it has a nameserver assigned then this is going */ /* straight into the inflight queue */ evdns_request_insert(req, &req_head); global_requests_inflight++; evdns_request_transmit(req); } else { evdns_request_insert(req, &req_waiting_head); global_requests_waiting++; } } /* exported function */ int evdns_resolve_ipv4(const char *name, int flags, evdns_callback_type callback, void *ptr) { log(EVDNS_LOG_DEBUG, "Resolve requested for %s", name); if (flags & DNS_QUERY_NO_SEARCH) { struct evdns_request *const req = request_new(TYPE_A, name, flags, callback, ptr); if (req == NULL) return (1); request_submit(req); return (0); } else { return (search_request_new(TYPE_A, name, flags, callback, ptr)); } } /* exported function */ int evdns_resolve_ipv6(const char *name, int flags, evdns_callback_type callback, void *ptr) { log(EVDNS_LOG_DEBUG, "Resolve requested for %s", name); if (flags & DNS_QUERY_NO_SEARCH) { struct evdns_request *const req = request_new(TYPE_AAAA, name, flags, callback, ptr); if (req == NULL) return (1); request_submit(req); return (0); } else { return (search_request_new(TYPE_AAAA, name, flags, callback, ptr)); } } int evdns_resolve_reverse(const struct in_addr *in, int flags, evdns_callback_type callback, void *ptr) { char buf[32]; struct evdns_request *req; u32 a; assert(in); a = ntohl(in->s_addr); snprintf(buf, sizeof(buf), "%d.%d.%d.%d.in-addr.arpa", (int)(u8)((a )&0xff), (int)(u8)((a>>8 )&0xff), (int)(u8)((a>>16)&0xff), (int)(u8)((a>>24)&0xff)); log(EVDNS_LOG_DEBUG, "Resolve requested for %s (reverse)", buf); req = request_new(TYPE_PTR, buf, flags, callback, ptr); if (!req) return 1; request_submit(req); return 0; } int evdns_resolve_reverse_ipv6(const struct in6_addr *in, int flags, evdns_callback_type callback, void *ptr) { /* 32 nybbles, 32 periods, "ip6.arpa", NUL. */ char buf[73]; char *cp; struct evdns_request *req; int i; assert(in); cp = buf; for (i=15; i >= 0; --i) { u8 byte = in->s6_addr[i]; *cp++ = "0123456789abcdef"[byte & 0x0f]; *cp++ = '.'; *cp++ = "0123456789abcdef"[byte >> 4]; *cp++ = '.'; } assert(cp + strlen("ip6.arpa") < buf+sizeof(buf)); memcpy(cp, "ip6.arpa", strlen("ip6.arpa")+1); log(EVDNS_LOG_DEBUG, "Resolve requested for %s (reverse)", buf); req = request_new(TYPE_PTR, buf, flags, callback, ptr); if (!req) return 1; request_submit(req); return 0; } /*/////////////////////////////////////////////////////////////////// */ /* Search support */ /* */ /* the libc resolver has support for searching a number of domains */ /* to find a name. If nothing else then it takes the single domain */ /* from the gethostname() call. */ /* */ /* It can also be configured via the domain and search options in a */ /* resolv.conf. */ /* */ /* The ndots option controls how many dots it takes for the resolver */ /* to decide that a name is non-local and so try a raw lookup first. */ struct search_domain { size_t len; struct search_domain *next; /* the text string is appended to this structure */ }; struct search_state { int refcount; int ndots; int num_domains; struct search_domain *head; }; static struct search_state *global_search_state = NULL; static void search_state_decref(struct search_state *const state) { if (!state) return; state->refcount--; if (!state->refcount) { struct search_domain *next, *dom; for (dom = state->head; dom; dom = next) { next = dom->next; CLEAR(dom); _mm_free(dom); } CLEAR(state); _mm_free(state); } } static struct search_state * search_state_new(void) { struct search_state *state = (struct search_state *) mm_malloc(sizeof(struct search_state)); if (!state) return NULL; memset(state, 0, sizeof(struct search_state)); state->refcount = 1; state->ndots = 1; return state; } static void search_postfix_clear(void) { search_state_decref(global_search_state); global_search_state = search_state_new(); } /* exported function */ void evdns_search_clear(void) { search_postfix_clear(); } static void search_postfix_add(const char *domain) { size_t domain_len; struct search_domain *sdomain; while (domain[0] == '.') domain++; domain_len = strlen(domain); if (!global_search_state) global_search_state = search_state_new(); if (!global_search_state) return; global_search_state->num_domains++; sdomain = (struct search_domain *) mm_malloc(sizeof(struct search_domain) + domain_len); if (!sdomain) return; memcpy( ((u8 *) sdomain) + sizeof(struct search_domain), domain, domain_len); sdomain->next = global_search_state->head; sdomain->len = domain_len; global_search_state->head = sdomain; } /* reverse the order of members in the postfix list. This is needed because, */ /* when parsing resolv.conf we push elements in the wrong order */ static void search_reverse(void) { struct search_domain *cur, *prev = NULL, *next; cur = global_search_state->head; while (cur) { next = cur->next; cur->next = prev; prev = cur; cur = next; } global_search_state->head = prev; } /* exported function */ void evdns_search_add(const char *domain) { search_postfix_add(domain); } /* exported function */ void evdns_search_ndots_set(const int ndots) { if (!global_search_state) global_search_state = search_state_new(); if (!global_search_state) return; global_search_state->ndots = ndots; } static void search_set_from_hostname(void) { char hostname[HOST_NAME_MAX + 1], *domainname; search_postfix_clear(); if (gethostname(hostname, sizeof(hostname))) return; domainname = strchr(hostname, '.'); if (!domainname) return; search_postfix_add(domainname); } /* warning: returns malloced string */ static char * search_make_new(const struct search_state *const state, int n, const char *const base_name) { const size_t base_len = strlen(base_name); const char need_to_append_dot = base_name[base_len - 1] == '.' ? 0 : 1; struct search_domain *dom; for (dom = state->head; dom; dom = dom->next) { if (!n--) { /* this is the postfix we want */ /* the actual postfix string is kept at the end of the structure */ const u8 *const postfix = ((u8 *) dom) + sizeof(struct search_domain); const size_t postfix_len = dom->len; char *const newname = (char *) mm_malloc(base_len + need_to_append_dot + postfix_len + 1); if (!newname) return NULL; memcpy(newname, base_name, base_len); if (need_to_append_dot) newname[base_len] = '.'; memcpy(newname + base_len + need_to_append_dot, postfix, postfix_len); newname[base_len + need_to_append_dot + postfix_len] = 0; return newname; } } /* we ran off the end of the list and still didn't find the requested string */ abort(); return NULL; /* unreachable; stops warnings in some compilers. */ } static int search_request_new(int type, const char *const name, int flags, evdns_callback_type user_callback, void *user_arg) { assert(type == TYPE_A || type == TYPE_AAAA); if ( ((flags & DNS_QUERY_NO_SEARCH) == 0) && global_search_state && global_search_state->num_domains) { /* we have some domains to search */ struct evdns_request *req; if (string_num_dots(name) >= global_search_state->ndots) { req = request_new(type, name, flags, user_callback, user_arg); if (!req) return 1; req->search_index = -1; } else { char *const new_name = search_make_new(global_search_state, 0, name); if (!new_name) return 1; req = request_new(type, new_name, flags, user_callback, user_arg); _mm_free(new_name); if (!req) return 1; req->search_index = 0; } req->search_origname = mm_strdup(name); req->search_state = global_search_state; req->search_flags = flags; global_search_state->refcount++; request_submit(req); return 0; } else { struct evdns_request *const req = request_new(type, name, flags, user_callback, user_arg); if (!req) return 1; request_submit(req); return 0; } } /* this is called when a request has failed to find a name. We need to check */ /* if it is part of a search and, if so, try the next name in the list */ /* returns: */ /* 0 another request has been submitted */ /* 1 no more requests needed */ static int search_try_next(struct evdns_request *const req) { if (req->search_state) { /* it is part of a search */ char *new_name; struct evdns_request *newreq; req->search_index++; if (req->search_index >= req->search_state->num_domains) { /* no more postfixes to try, however we may need to try */ /* this name without a postfix */ if (string_num_dots(req->search_origname) < req->search_state->ndots) { /* yep, we need to try it raw */ struct evdns_request *const newreq = request_new(req->request_type, req->search_origname, req->search_flags, req->user_callback, req->user_pointer); log(EVDNS_LOG_DEBUG, "Search: trying raw query %s", req->search_origname); if (newreq) { request_submit(newreq); return 0; } } return 1; } new_name = search_make_new(req->search_state, req->search_index, req->search_origname); if (!new_name) return 1; log(EVDNS_LOG_DEBUG, "Search: now trying %s (%d)", new_name, req->search_index); newreq = request_new(req->request_type, new_name, req->search_flags, req->user_callback, req->user_pointer); mm_free(new_name); if (!newreq) return 1; newreq->search_origname = req->search_origname; req->search_origname = NULL; newreq->search_state = req->search_state; newreq->search_flags = req->search_flags; newreq->search_index = req->search_index; newreq->search_state->refcount++; request_submit(newreq); return 0; } return 1; } static void search_request_finished(struct evdns_request *const req) { if (req->search_state) { search_state_decref(req->search_state); req->search_state = NULL; } if (req->search_origname) { mm_free(req->search_origname); req->search_origname = NULL; } } /*/////////////////////////////////////////////////////////////////// */ /* Parsing resolv.conf files */ static void evdns_resolv_set_defaults(int flags) { /* if the file isn't found then we assume a local resolver */ if (flags & DNS_OPTION_SEARCH) search_set_from_hostname(); if (flags & DNS_OPTION_NAMESERVERS) evdns_nameserver_ip_add("127.0.0.1"); } #ifndef HAVE_STRTOK_R static char * strtok_r(char *s, const char *delim, char **state) { (void)state; return strtok(s, delim); } #endif /* helper version of atoi which returns -1 on error */ static int strtoint(const char *const str) { char *endptr; const long r = strtol(str, &endptr, 10); if (*endptr || r > INT_MAX) return -1; return (int)r; } /* helper version of atoi that returns -1 on error and clips to bounds. */ static int strtoint_clipped(const char *const str, int min, int max) { int r = strtoint(str); if (r == -1) return r; else if (rmax) return max; else return r; } /* exported function */ int evdns_set_option(const char *option, const char *val, int flags) { if (!strncmp(option, "ndots:", 6)) { const int ndots = strtoint(val); if (ndots == -1) return -1; if (!(flags & DNS_OPTION_SEARCH)) return 0; log(EVDNS_LOG_DEBUG, "Setting ndots to %d", ndots); if (!global_search_state) global_search_state = search_state_new(); if (!global_search_state) return -1; global_search_state->ndots = ndots; } else if (!strncmp(option, "timeout:", 8)) { const int timeout = strtoint(val); if (timeout == -1) return -1; if (!(flags & DNS_OPTION_MISC)) return 0; log(EVDNS_LOG_DEBUG, "Setting timeout to %d", timeout); global_timeout.tv_sec = timeout; } else if (!strncmp(option, "max-timeouts:", 12)) { const int maxtimeout = strtoint_clipped(val, 1, 255); if (maxtimeout == -1) return -1; if (!(flags & DNS_OPTION_MISC)) return 0; log(EVDNS_LOG_DEBUG, "Setting maximum allowed timeouts to %d", maxtimeout); global_max_nameserver_timeout = maxtimeout; } else if (!strncmp(option, "max-inflight:", 13)) { const int maxinflight = strtoint_clipped(val, 1, 65000); if (maxinflight == -1) return -1; if (!(flags & DNS_OPTION_MISC)) return 0; log(EVDNS_LOG_DEBUG, "Setting maximum inflight requests to %d", maxinflight); global_max_requests_inflight = maxinflight; } else if (!strncmp(option, "attempts:", 9)) { int retries = strtoint(val); if (retries == -1) return -1; if (retries > 255) retries = 255; if (!(flags & DNS_OPTION_MISC)) return 0; log(EVDNS_LOG_DEBUG, "Setting retries to %d", retries); global_max_retransmits = retries; } else if (!strncmp(option, "randomize-case:", 15)) { int randcase = strtoint(val); if (!(flags & DNS_OPTION_MISC)) return 0; log(EVDNS_LOG_DEBUG, "Setting randomize_case to %d", randcase); global_randomize_case = randcase; } return 0; } static void resolv_conf_parse_line(char *const start, int flags) { char *strtok_state; static const char *const delims = " \t"; #define NEXT_TOKEN strtok_r(NULL, delims, &strtok_state) char *const first_token = strtok_r(start, delims, &strtok_state); if (!first_token) return; if (!strcmp(first_token, "nameserver") && (flags & DNS_OPTION_NAMESERVERS)) { const char *const nameserver = NEXT_TOKEN; evdns_nameserver_ip_add(nameserver); } else if (!strcmp(first_token, "domain") && (flags & DNS_OPTION_SEARCH)) { const char *const domain = NEXT_TOKEN; if (domain) { search_postfix_clear(); search_postfix_add(domain); } } else if (!strcmp(first_token, "search") && (flags & DNS_OPTION_SEARCH)) { const char *domain; search_postfix_clear(); while ((domain = NEXT_TOKEN)) { search_postfix_add(domain); } search_reverse(); } else if (!strcmp(first_token, "options")) { const char *option; while ((option = NEXT_TOKEN)) { const char *val = strchr(option, ':'); evdns_set_option(option, val ? val+1 : "", flags); } } #undef NEXT_TOKEN } /* exported function */ /* returns: */ /* 0 no errors */ /* 1 failed to open file */ /* 2 failed to stat file */ /* 3 file too large */ /* 4 out of memory */ /* 5 short read from file */ int evdns_resolv_conf_parse(int flags, const char *const filename) { struct stat st; int fd, n, r; u8 *resolv; char *start; int err = 0; log(EVDNS_LOG_DEBUG, "Parsing resolv.conf file %s", filename); fd = open(filename, O_RDONLY); if (fd < 0) { evdns_resolv_set_defaults(flags); return 1; } if (fstat(fd, &st)) { err = 2; goto out1; } if (!st.st_size) { evdns_resolv_set_defaults(flags); err = (flags & DNS_OPTION_NAMESERVERS) ? 6 : 0; goto out1; } if (st.st_size > 65535) { err = 3; goto out1; } /* no resolv.conf should be any bigger */ resolv = (u8 *) mm_malloc((size_t)st.st_size + 1); if (!resolv) { err = 4; goto out1; } n = 0; while ((r = (int)read(fd, resolv+n, (size_t)st.st_size-n)) > 0) { n += r; if (n == st.st_size) break; assert(n < st.st_size); } if (r < 0) { err = 5; goto out2; } resolv[n] = 0; /* we malloced an extra byte; this should be fine. */ start = (char *) resolv; for (;;) { char *const newline = strchr(start, '\n'); if (!newline) { resolv_conf_parse_line(start, flags); break; } else { *newline = 0; resolv_conf_parse_line(start, flags); start = newline + 1; } } if (!server_head && (flags & DNS_OPTION_NAMESERVERS)) { /* no nameservers were configured. */ evdns_nameserver_ip_add("127.0.0.1"); err = 6; } if (flags & DNS_OPTION_SEARCH && (!global_search_state || global_search_state->num_domains == 0)) { search_set_from_hostname(); } out2: mm_free(resolv); out1: close(fd); return err; } #ifdef WIN32 /* Add multiple nameservers from a space-or-comma-separated list. */ static int evdns_nameserver_ip_add_line(const char *ips) { const char *addr; char *buf; int r; while (*ips) { while (ISSPACE(*ips) || *ips == ',' || *ips == '\t') ++ips; addr = ips; while (ISDIGIT(*ips) || *ips == '.' || *ips == ':' || *ips == '[' || *ips == ']') ++ips; buf = mm_malloc(ips-addr+1); if (!buf) return 4; memcpy(buf, addr, ips-addr); buf[ips-addr] = '\0'; r = evdns_nameserver_ip_add(buf); mm_free(buf); if (r) return r; } return 0; } typedef DWORD(WINAPI *GetNetworkParams_fn_t)(FIXED_INFO *, DWORD*); /* Use the windows GetNetworkParams interface in iphlpapi.dll to */ /* figure out what our nameservers are. */ static int load_nameservers_with_getnetworkparams(void) { /* Based on MSDN examples and inspection of c-ares code. */ FIXED_INFO *fixed; HMODULE handle = 0; ULONG size = sizeof(FIXED_INFO); void *buf = NULL; int status = 0, r, added_any; IP_ADDR_STRING *ns; GetNetworkParams_fn_t fn; /* XXXX Possibly, we should hardcode the location of this DLL. */ if (!(handle = LoadLibrary("iphlpapi.dll"))) { log(EVDNS_LOG_WARN, "Could not open iphlpapi.dll"); /* right now status = 0, doesn't that mean "good" - mikec */ status = -1; goto done; } if (!(fn = (GetNetworkParams_fn_t) GetProcAddress(handle, "GetNetworkParams"))) { log(EVDNS_LOG_WARN, "Could not get address of function."); /* same as above */ status = -1; goto done; } buf = mm_malloc(size); if (!buf) { status = 4; goto done; } fixed = buf; r = fn(fixed, &size); if (r != ERROR_SUCCESS && r != ERROR_BUFFER_OVERFLOW) { status = -1; goto done; } if (r != ERROR_SUCCESS) { mm_free(buf); buf = mm_malloc(size); if (!buf) { status = 4; goto done; } fixed = buf; r = fn(fixed, &size); if (r != ERROR_SUCCESS) { log(EVDNS_LOG_DEBUG, "fn() failed."); status = -1; goto done; } } assert(fixed); added_any = 0; ns = &(fixed->DnsServerList); while (ns) { r = evdns_nameserver_ip_add_line(ns->IpAddress.String); if (r) { log(EVDNS_LOG_DEBUG,"Could not add nameserver %s to list, " "error: %d; status: %d", (ns->IpAddress.String),(int)GetLastError(), r); status = r; } else { log(EVDNS_LOG_DEBUG,"Successfully added %s as nameserver",ns->IpAddress.String); added_any++; } ns = ns->Next; } if (!added_any) { log(EVDNS_LOG_DEBUG, "No nameservers added."); if (status == 0) status = -1; } else { status = 0; } done: if (buf) mm_free(buf); if (handle) FreeLibrary(handle); return status; } static int config_nameserver_from_reg_key(HKEY key, const char *subkey) { char *buf; DWORD bufsz = 0, type = 0; int status = 0; if (RegQueryValueEx(key, subkey, 0, &type, NULL, &bufsz) != ERROR_MORE_DATA) return -1; if (!(buf = mm_malloc(bufsz))) return -1; if (RegQueryValueEx(key, subkey, 0, &type, (LPBYTE)buf, &bufsz) == ERROR_SUCCESS && bufsz > 1) { status = evdns_nameserver_ip_add_line(buf); } mm_free(buf); return status; } #define SERVICES_KEY "System\\CurrentControlSet\\Services\\" #define WIN_NS_9X_KEY SERVICES_KEY "VxD\\MSTCP" #define WIN_NS_NT_KEY SERVICES_KEY "Tcpip\\Parameters" static int load_nameservers_from_registry(void) { int found = 0; int r; #define TRY(k, name) \ if (!found && config_nameserver_from_reg_key(k,name) == 0) { \ log(EVDNS_LOG_DEBUG,"Found nameservers in %s/%s",#k,name); \ found = 1; \ } else if (!found) { \ log(EVDNS_LOG_DEBUG,"Didn't find nameservers in %s/%s", \ #k,#name); \ } if (((int)GetVersion()) > 0) { /* NT */ HKEY nt_key = 0, interfaces_key = 0; if (RegOpenKeyEx(HKEY_LOCAL_MACHINE, WIN_NS_NT_KEY, 0, KEY_READ, &nt_key) != ERROR_SUCCESS) { log(EVDNS_LOG_DEBUG,"Couldn't open nt key, %d",(int)GetLastError()); return -1; } r = RegOpenKeyEx(nt_key, "Interfaces", 0, KEY_QUERY_VALUE|KEY_ENUMERATE_SUB_KEYS, &interfaces_key); if (r != ERROR_SUCCESS) { log(EVDNS_LOG_DEBUG,"Couldn't open interfaces key, %d",(int)GetLastError()); return -1; } TRY(nt_key, "NameServer"); TRY(nt_key, "DhcpNameServer"); TRY(interfaces_key, "NameServer"); TRY(interfaces_key, "DhcpNameServer"); RegCloseKey(interfaces_key); RegCloseKey(nt_key); } else { HKEY win_key = 0; if (RegOpenKeyEx(HKEY_LOCAL_MACHINE, WIN_NS_9X_KEY, 0, KEY_READ, &win_key) != ERROR_SUCCESS) { log(EVDNS_LOG_DEBUG, "Couldn't open registry key, %d", (int)GetLastError()); return -1; } TRY(win_key, "NameServer"); RegCloseKey(win_key); } if (found == 0) { log(EVDNS_LOG_WARN,"Didn't find any nameservers."); } return found ? 0 : -1; #undef TRY } int evdns_config_windows_nameservers(void) { if (load_nameservers_with_getnetworkparams() == 0) return 0; return load_nameservers_from_registry(); } #endif int evdns_init(void) { int res = 0; #ifdef WIN32 evdns_config_windows_nameservers(); #else res = evdns_resolv_conf_parse(DNS_OPTIONS_ALL, "/etc/resolv.conf"); #endif return (res); } const char * evdns_err_to_string(int err) { switch (err) { case DNS_ERR_NONE: return "no error"; case DNS_ERR_FORMAT: return "misformatted query"; case DNS_ERR_SERVERFAILED: return "server failed"; case DNS_ERR_NOTEXIST: return "name does not exist"; case DNS_ERR_NOTIMPL: return "query not implemented"; case DNS_ERR_REFUSED: return "refused"; case DNS_ERR_TRUNCATED: return "reply truncated or ill-formed"; case DNS_ERR_UNKNOWN: return "unknown"; case DNS_ERR_TIMEOUT: return "request timed out"; case DNS_ERR_SHUTDOWN: return "dns subsystem shut down"; default: return "[Unknown error code]"; } } void evdns_shutdown(int fail_requests) { struct nameserver *server, *server_next; struct search_domain *dom, *dom_next; while (req_head) { if (fail_requests) reply_callback(req_head, 0, DNS_ERR_SHUTDOWN, NULL); request_finished(req_head, &req_head); } while (req_waiting_head) { if (fail_requests) reply_callback(req_waiting_head, 0, DNS_ERR_SHUTDOWN, NULL); request_finished(req_waiting_head, &req_waiting_head); } global_requests_inflight = global_requests_waiting = 0; for (server = server_head; server; server = server_next) { server_next = server->next; if (server->socket >= 0) CLOSE_SOCKET(server->socket); (void) event_del(&server->event); if (server->state == 0) del_timeout_event(server); CLEAR(server); mm_free(server); if (server_next == server_head) break; } server_head = NULL; global_good_nameservers = 0; if (global_search_state) { for (dom = global_search_state->head; dom; dom = dom_next) { dom_next = dom->next; CLEAR(dom); mm_free(dom); } CLEAR(global_search_state); mm_free(global_search_state); global_search_state = NULL; } evdns_log_fn = NULL; } #ifdef EVDNS_MAIN void main_callback(int result, char type, int count, int ttl, void *addrs, void *orig) { char *n = (char*)orig; int i; for (i = 0; i < count; ++i) { if (type == DNS_IPv4_A) { printf("%s: %s\n", n, debug_ntoa(((u32*)addrs)[i])); } else if (type == DNS_PTR) { printf("%s: %s\n", n, ((char**)addrs)[i]); } } if (!count) { printf("%s: No answer (%d)\n", n, result); } fflush(stdout); } void evdns_server_callback(struct evdns_server_request *req, void *data) { int i, r; (void)data; /* dummy; give 192.168.11.11 as an answer for all A questions, * give foo.bar.example.com as an answer for all PTR questions. */ for (i = 0; i < req->nquestions; ++i) { u32 ans = htonl(0xc0a80b0bUL); if (req->questions[i]->type == EVDNS_TYPE_A && req->questions[i]->dns_question_class == EVDNS_CLASS_INET) { printf(" -- replying for %s (A)\n", req->questions[i]->name); r = evdns_server_request_add_a_reply(req, req->questions[i]->name, 1, &ans, 10); if (r<0) printf("eeep, didn't work.\n"); } else if (req->questions[i]->type == EVDNS_TYPE_PTR && req->questions[i]->dns_question_class == EVDNS_CLASS_INET) { printf(" -- replying for %s (PTR)\n", req->questions[i]->name); r = evdns_server_request_add_ptr_reply(req, NULL, req->questions[i]->name, "foo.bar.example.com", 10); } else { printf(" -- skipping %s [%d %d]\n", req->questions[i]->name, req->questions[i]->type, req->questions[i]->dns_question_class); } } r = evdns_server_request_respond(req, 0); if (r<0) printf("eeek, couldn't send reply.\n"); } void logfn(int is_warn, const char *msg) { (void) is_warn; fprintf(stderr, "%s\n", msg); } int main(int c, char **v) { int idx; int reverse = 0, verbose = 1, servertest = 0; if (c<2) { fprintf(stderr, "syntax: %s [-x] [-v] hostname\n", v[0]); fprintf(stderr, "syntax: %s [-servertest]\n", v[0]); return 1; } idx = 1; while (idx < c && v[idx][0] == '-') { if (!strcmp(v[idx], "-x")) reverse = 1; else if (!strcmp(v[idx], "-v")) verbose = 1; else if (!strcmp(v[idx], "-servertest")) servertest = 1; else fprintf(stderr, "Unknown option %s\n", v[idx]); ++idx; } event_init(); if (verbose) evdns_set_log_fn(logfn); evdns_resolv_conf_parse(DNS_OPTION_NAMESERVERS, "/etc/resolv.conf"); if (servertest) { int sock; struct sockaddr_in my_addr; sock = socket(PF_INET, SOCK_DGRAM, 0); fcntl(sock, F_SETFL, O_NONBLOCK); my_addr.sin_family = AF_INET; my_addr.sin_port = htons(10053); my_addr.sin_addr.s_addr = INADDR_ANY; if (bind(sock, (struct sockaddr*)&my_addr, sizeof(my_addr))<0) { perror("bind"); exit(1); } evdns_add_server_port(sock, 0, evdns_server_callback, NULL); } for (; idx < c; ++idx) { if (reverse) { struct in_addr addr; if (!inet_aton(v[idx], &addr)) { fprintf(stderr, "Skipping non-IP %s\n", v[idx]); continue; } fprintf(stderr, "resolving %s...\n",v[idx]); evdns_resolve_reverse(&addr, 0, main_callback, v[idx]); } else { fprintf(stderr, "resolving (fwd) %s...\n",v[idx]); evdns_resolve_ipv4(v[idx], 0, main_callback, v[idx]); } } fflush(stdout); event_dispatch(); return 0; } #endif /* Local Variables: */ /* tab-width: 4 */ /* c-basic-offset: 4 */ /* indent-tabs-mode: t */ /* End: */