/* NICTA Public Software Licence Version 1.0 Copyright © 2004 National ICT Australia Ltd All rights reserved. By this licence, National ICT Australia Ltd (NICTA) grants permission, free of charge, to any person who obtains a copy of this software and any associated documentation files ("the Software") to use and deal with the Software in source code and binary forms without restriction, with or without modification, and to permit persons to whom the Software is furnished to do so, provided that the following conditions are met: - Redistributions of source code must retain the above copyright notice, this list of conditions and the following disclaimers. - Redistributions in binary form must reproduce the above copyright notice, this list of conditions and the following disclaimers in the documentation and/or other materials provided with the distribution. - The name of NICTA may not be used to endorse or promote products derived from this Software without specific prior written permission. EXCEPT AS EXPRESSLY STATED IN THIS LICENCE AND TO THE FULL EXTENT PERMITTED BY APPLICABLE LAW, THE SOFTWARE IS PROVIDED "AS-IS" AND NICTA MAKES NO REPRESENTATIONS, WARRANTIES OR CONDITIONS OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING, WITHOUT LIMITATION, ANY REPRESENTATIONS, WARRANTIES OR CONDITIONS REGARDING THE CONTENTS OR ACCURACY OF THE SOFTWARE, OR OF TITLE, MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE, NONINFRINGEMENT, THE ABSENCE OF LATENT OR OTHER DEFECTS, OR THE PRESENCE OR ABSENCE OF ERRORS, WHETHER OR NOT DISCOVERABLE. TO THE FULL EXTENT PERMITTED BY APPLICABLE LAW, IN NO EVENT WILL NICTA BE LIABLE ON ANY LEGAL THEORY (INCLUDING, WITHOUT LIMITATION, NEGLIGENCE) FOR ANY LOSS OR DAMAGE WHATSOEVER, INCLUDING (WITHOUT LIMITATION) LOSS OF PRODUCTION OR OPERATION TIME, LOSS, DAMAGE OR CORRUPTION OF DATA OR RECORDS; OR LOSS OF ANTICIPATED SAVINGS, OPPORTUNITY, REVENUE, PROFIT OR GOODWILL, OR OTHER ECONOMIC LOSS; OR ANY SPECIAL, INCIDENTAL, INDIRECT, CONSEQUENTIAL, PUNITIVE OR EXEMPLARY DAMAGES ARISING OUT OF OR IN CONNECTION WITH THIS LICENCE, THE SOFTWARE OR THE USE OF THE SOFTWARE, EVEN IF NICTA HAS BEEN ADVISED OF THE POSSIBILITY OF SUCH DAMAGES. If applicable legislation implies warranties or conditions, or imposes obligations or liability on NICTA in respect of the Software that cannot be wholly or partly excluded, restricted or modified, NICTA's liability is limited, to the full extent permitted by the applicable legislation, at its option, to: a. in the case of goods, any one or more of the following: i. the replacement of the goods or the supply of equivalent goods; ii. the repair of the goods; iii. the payment of the cost of replacing the goods or of acquiring equivalent goods; iv. the payment of the cost of having the goods repaired; or b. in the case of services: i. the supplying of the services again; or ii. the payment of the cost of having the services supplied again. */ /* NSSwitch Implementation of mDNS interface. Andrew White (Andrew.White@nicta.com.au) May 2004 */ #include #include #include #include #include #include #include #include #include #include #include #include #define BIND_8_COMPAT 1 #include #include //---------- // Public functions /* Count the number of dots in a name string. */ int count_dots (const char * name); /* Test whether a domain name is local. Returns 1 if name ends with ".local" or ".local." 0 otherwise */ int islocal (const char * name); /* Format an address structure as a string appropriate for DNS reverse (PTR) lookup, based on address type. Parameters prefixlen Prefix length, in bits. When formatting, this will be rounded up to the nearest appropriate size. If -1, assume maximum. buf Output buffer. Must be long enough to hold largest possible output. Returns Pointer to (first character of) output buffer, or NULL on error. */ char * format_reverse_addr (int af, const void * addr, int prefixlen, char * buf); /* Format an address structure as a string appropriate for DNS reverse (PTR) lookup for AF_INET. Output is in .in-addr.arpa domain. Parameters prefixlen Prefix length, in bits. When formatting, this will be rounded up to the nearest byte (8). If -1, assume 32. buf Output buffer. Must be long enough to hold largest possible output. For AF_INET, this is 29 characters (including null). Returns Pointer to (first character of) output buffer, or NULL on error. */ char * format_reverse_addr_in ( const struct in_addr * addr, int prefixlen, char * buf ); #define DNS_PTR_AF_INET_SIZE 29 /* Format an address structure as a string appropriate for DNS reverse (PTR) lookup for AF_INET6. Output is in .ip6.arpa domain. Parameters prefixlen Prefix length, in bits. When formatting, this will be rounded up to the nearest nibble (4). If -1, assume 128. buf Output buffer. Must be long enough to hold largest possible output. For AF_INET6, this is 72 characters (including null). Returns Pointer to (first character of) output buffer, or NULL on error. */ char * format_reverse_addr_in6 ( const struct in6_addr * addr, int prefixlen, char * buf ); #define DNS_PTR_AF_INET6_SIZE 72 /* Compare whether the given dns name has the given domain suffix. A single leading '.' on the name or leading or trailing '.' on the domain is ignored for the purposes of the comparison. Multiple leading or trailing '.'s are an error. Other DNS syntax errors are not checked for. The comparison is case insensitive. Returns 1 on success (match) 0 on failure (no match) < 0 on error */ int cmp_dns_suffix (const char * name, const char * domain); enum { CMP_DNS_SUFFIX_SUCCESS = 1, CMP_DNS_SUFFIX_FAILURE = 0, CMP_DNS_SUFFIX_BAD_NAME = 1, CMP_DNS_SUFFIX_BAD_DOMAIN = -2 }; typedef int ns_type_t; typedef int ns_class_t; /* Convert a DNS resource record (RR) code to an address family (AF) code. Parameters rrtype resource record type (from nameser.h) Returns Appropriate AF code (from socket.h), or AF_UNSPEC if an appropriate mapping couldn't be determined */ int rr_to_af (ns_type_t rrtype); /* Convert an address family (AF) code to a DNS resource record (RR) code. Parameters int address family code (from socket.h) Returns Appropriate RR code (from nameser.h), or ns_t_invalid if an appropriate mapping couldn't be determined */ ns_type_t af_to_rr (int af); /* Convert a string to an address family (case insensitive). Returns Matching AF code, or AF_UNSPEC if no match found. */ int str_to_af (const char * str); /* Convert a string to an ns_class_t (case insensitive). Returns Matching ns_class_t, or ns_c_invalid if no match found. */ ns_class_t str_to_ns_class (const char * str); /* Convert a string to an ns_type_t (case insensitive). Returns Matching ns_type_t, or ns_t_invalid if no match found. */ ns_type_t str_to_ns_type (const char * str); /* Convert an address family code to a string. Returns String representation of AF, or NULL if address family unrecognised or invalid. */ const char * af_to_str (int in); /* Convert an ns_class_t code to a string. Returns String representation of ns_class_t, or NULL if ns_class_t unrecognised or invalid. */ const char * ns_class_to_str (ns_class_t in); /* Convert an ns_type_t code to a string. Returns String representation of ns_type_t, or NULL if ns_type_t unrecognised or invalid. */ const char * ns_type_to_str (ns_type_t in); /* Convert DNS rdata in label format (RFC1034, RFC1035) to a name. On error, partial data is written to name (as much as was successfully processed) and an error code is returned. Errors include a name too long for the buffer and a pointer in the label (which cannot be resolved). Parameters rdata Rdata formatted as series of labels. rdlen Length of rdata buffer. name Buffer to store fully qualified result in. By RFC1034 section 3.1, a 255 character buffer (256 characters including null) is long enough for any legal name. name_len Number of characters available in name buffer, not including trailing null. Returns Length of name buffer (not including trailing null). < 0 on error. A return of 0 implies the empty domain. */ int dns_rdata_to_name (const char * rdata, int rdlen, char * name, int name_len); enum { DNS_RDATA_TO_NAME_BAD_FORMAT = -1, // Format is broken. Usually because we ran out of data // (according to rdata) before the labels said we should. DNS_RDATA_TO_NAME_TOO_LONG = -2, // The converted rdata is longer than the name buffer. DNS_RDATA_TO_NAME_PTR = -3, // The rdata contains a pointer. }; #define DNS_LABEL_MAXLEN 63 // Maximum length of a single DNS label #define DNS_NAME_MAXLEN 256 // Maximum length of a DNS name //---------- // Public types typedef int errcode_t; // Used for 0 = success, non-zero = error code functions //---------- // Public functions /* Test whether a domain name is in a domain covered by nss_mdns. The name is assumed to be fully qualified (trailing dot optional); unqualified names will be processed but may return unusual results if the unqualified prefix happens to match a domain suffix. Returns 1 success 0 failure -1 error, check errno */ int config_is_mdns_suffix (const char * name); /* Loads all relevant data from configuration file. Other code should rarely need to call this function, since all other public configuration functions do so implicitly. Once loaded, configuration info doesn't change. Returns 0 configuration ready non-zero configuration error code */ errcode_t init_config (); #define ENTNAME hostent #define DATABASE "hosts" #include // For nss_status #include // For hostent #include // For size_t typedef enum nss_status nss_status; typedef struct hostent hostent; /* gethostbyname implementation name: name to look up result_buf: resulting entry buf: auxillary buffer buflen: length of auxillary buffer errnop: pointer to errno h_errnop: pointer to h_errno */ nss_status _nss_mdns_gethostbyname_r ( const char *name, hostent * result_buf, char *buf, size_t buflen, int *errnop, int *h_errnop ); /* gethostbyname2 implementation name: name to look up af: address family result_buf: resulting entry buf: auxillary buffer buflen: length of auxillary buffer errnop: pointer to errno h_errnop: pointer to h_errno */ nss_status _nss_mdns_gethostbyname2_r ( const char *name, int af, hostent * result_buf, char *buf, size_t buflen, int *errnop, int *h_errnop ); /* gethostbyaddr implementation addr: address structure to look up len: length of address structure af: address family result_buf: resulting entry buf: auxillary buffer buflen: length of auxillary buffer errnop: pointer to errno h_errnop: pointer to h_errno */ nss_status _nss_mdns_gethostbyaddr_r ( const void *addr, socklen_t len, int af, hostent * result_buf, char *buf, size_t buflen, int *errnop, int *h_errnop ); //---------- // Types and Constants const int MDNS_VERBOSE = 0; // This enables verbose syslog messages // If zero, only "imporant" messages will appear in syslog #define k_hostname_maxlen 256 // As per RFC1034 and RFC1035 #define k_aliases_max 15 #define k_addrs_max 15 typedef struct buf_header { char hostname [k_hostname_maxlen + 1]; char * aliases [k_aliases_max + 1]; char * addrs [k_addrs_max + 1]; } buf_header_t; typedef struct result_map { int done; nss_status status; hostent * hostent; buf_header_t * header; int aliases_count; int addrs_count; char * buffer; int addr_idx; // Index for addresses - grow from low end // Index points to first empty space int alias_idx; // Index for aliases - grow from high end // Index points to lowest entry int r_errno; int r_h_errno; } result_map_t; static const struct timeval k_select_time = { 0, 500000 }; // 0 seconds, 500 milliseconds //---------- // Local prototypes static nss_status mdns_gethostbyname2 ( const char *name, int af, hostent * result_buf, char *buf, size_t buflen, int *errnop, int *h_errnop ); /* Lookup name using mDNS server */ static nss_status mdns_lookup_name ( const char * fullname, int af, result_map_t * result ); /* Lookup address using mDNS server */ static nss_status mdns_lookup_addr ( const void * addr, socklen_t len, int af, const char * addr_str, result_map_t * result ); /* Handle incoming MDNS events */ static nss_status handle_events (DNSServiceRef sdref, result_map_t * result, const char * str); // Callback for mdns_lookup operations //DNSServiceQueryRecordReply mdns_lookup_callback; typedef void mdns_lookup_callback_t ( DNSServiceRef sdref, DNSServiceFlags flags, uint32_t interface_index, DNSServiceErrorType error_code, const char *fullname, uint16_t rrtype, uint16_t rrclass, uint16_t rdlen, const void *rdata, uint32_t ttl, void *context ); mdns_lookup_callback_t mdns_lookup_callback; static int init_result ( result_map_t * result, hostent * result_buf, char * buf, size_t buflen ); static int callback_body_ptr ( const char * fullname, result_map_t * result, int rdlen, const void * rdata ); static void * add_address_to_buffer (result_map_t * result, const void * data, int len); static char * add_alias_to_buffer (result_map_t * result, const char * data, int len); static char * add_hostname_len (result_map_t * result, const char * fullname, int len); static char * add_hostname_or_alias (result_map_t * result, const char * data, int len); static void * contains_address (result_map_t * result, const void * data, int len); static char * contains_alias (result_map_t * result, const char * data); static const char * is_applicable_name ( result_map_t * result, const char * name, char * lookup_name ); static const char * is_applicable_addr ( result_map_t * result, const void * addr, int af, char * addr_str ); // Error code functions static nss_status set_err (result_map_t * result, nss_status status, int err, int herr); static nss_status set_err_notfound (result_map_t * result); static nss_status set_err_bad_hostname (result_map_t * result); static nss_status set_err_buf_too_small (result_map_t * result); static nss_status set_err_internal_resource_full (result_map_t * result); static nss_status set_err_system (result_map_t * result); static nss_status set_err_mdns_failed (result_map_t * result); static nss_status set_err_success (result_map_t * result); //---------- // Global variables //---------- // NSS functions nss_status _nss_mdns_gethostbyname_r ( const char *name, hostent * result_buf, char *buf, size_t buflen, int *errnop, int *h_errnop ) { if (MDNS_VERBOSE) syslog (LOG_DEBUG, "mdns: Called nss_mdns_gethostbyname with %s", name ); return mdns_gethostbyname2 ( name, AF_INET, result_buf, buf, buflen, errnop, h_errnop ); } nss_status _nss_mdns_gethostbyname2_r ( const char *name, int af, hostent * result_buf, char *buf, size_t buflen, int *errnop, int *h_errnop ) { if (MDNS_VERBOSE) syslog (LOG_DEBUG, "mdns: Called nss_mdns_gethostbyname2 with %s", name ); return mdns_gethostbyname2 ( name, af, result_buf, buf, buflen, errnop, h_errnop ); } nss_status _nss_mdns_gethostbyaddr_r ( const void *addr, socklen_t len, int af, hostent * result_buf, char *buf, size_t buflen, int *errnop, int *h_errnop ) { char addr_str [NI_MAXHOST + 1]; result_map_t result; int err_status; if (inet_ntop (af, addr, addr_str, NI_MAXHOST) == NULL) { const char * family = af_to_str (af); if (family == NULL) { family = "Unknown"; } syslog (LOG_WARNING, "mdns: Couldn't covert address, family %d (%s) in nss_mdns_gethostbyaddr: %s", af, family, strerror (errno) ); // This address family never applicable to us, so return NOT_FOUND *errnop = ENOENT; *h_errnop = HOST_NOT_FOUND; return NSS_STATUS_NOTFOUND; } if (MDNS_VERBOSE) { syslog (LOG_DEBUG, "mdns: Called nss_mdns_gethostbyaddr with %s", addr_str ); } // Initialise result err_status = init_result (&result, result_buf, buf, buflen); if (err_status) { *errnop = err_status; *h_errnop = NETDB_INTERNAL; return NSS_STATUS_TRYAGAIN; } if (is_applicable_addr (&result, addr, af, addr_str)) { nss_status rv; rv = mdns_lookup_addr (addr, len, af, addr_str, &result); if (rv == NSS_STATUS_SUCCESS) { return rv; } } // Return current error status (defaults to NOT_FOUND) *errnop = result.r_errno; *h_errnop = result.r_h_errno; return result.status; } //---------- // Local functions nss_status mdns_gethostbyname2 ( const char *name, int af, hostent * result_buf, char *buf, size_t buflen, int *errnop, int *h_errnop ) { char lookup_name [k_hostname_maxlen + 1]; result_map_t result; int err_status; // Initialise result err_status = init_result (&result, result_buf, buf, buflen); if (err_status) { *errnop = err_status; *h_errnop = NETDB_INTERNAL; return NSS_STATUS_TRYAGAIN; } if (is_applicable_name (&result, name, lookup_name)) { // Try using mdns nss_status rv; if (MDNS_VERBOSE) syslog (LOG_DEBUG, "mdns: Local name: %s", name ); rv = mdns_lookup_name (name, af, &result); if (rv == NSS_STATUS_SUCCESS) { return rv; } } // Return current error status (defaults to NOT_FOUND) *errnop = result.r_errno; *h_errnop = result.r_h_errno; return result.status; } /* Lookup a fully qualified hostname using the default record type for the specified address family. Parameters fullname Fully qualified hostname. If not fully qualified the code will still 'work', but the lookup is unlikely to succeed. af Either AF_INET or AF_INET6. Other families are not supported. result Initialised 'result' data structure. */ static nss_status mdns_lookup_name ( const char * fullname, int af, result_map_t * result ) { // Lookup using mDNS. DNSServiceErrorType errcode; DNSServiceRef sdref; ns_type_t rrtype; nss_status status; if (MDNS_VERBOSE) syslog (LOG_DEBUG, "mdns: Attempting lookup of %s", fullname ); switch (af) { case AF_INET: rrtype = kDNSServiceType_A; result->hostent->h_length = 4; // Length of an A record break; case AF_INET6: rrtype = kDNSServiceType_AAAA; result->hostent->h_length = 16; // Length of an AAAA record break; default: syslog (LOG_WARNING, "mdns: Unsupported address family %d", af ); return set_err_bad_hostname (result); } result->hostent->h_addrtype = af; errcode = DNSServiceQueryRecord ( &sdref, kDNSServiceFlagsForceMulticast, // force multicast query kDNSServiceInterfaceIndexAny, // all interfaces fullname, // full name to query for rrtype, // resource record type kDNSServiceClass_IN, // internet class records mdns_lookup_callback, // callback result // Context - result buffer ); if (errcode) { syslog (LOG_WARNING, "mdns: Failed to initialise lookup, error %d", errcode ); return set_err_mdns_failed (result); } status = handle_events (sdref, result, fullname); DNSServiceRefDeallocate (sdref); return status; } /* Reverse (PTR) lookup for the specified address. Parameters addr Either a struct in_addr or a struct in6_addr addr_len size of the address af Either AF_INET or AF_INET6. Other families are not supported. Must match addr addr_str Address in format suitable for PTR lookup. AF_INET: a.b.c.d -> d.c.b.a.in-addr.arpa AF_INET6: reverse nibble format, x.x.x...x.ip6.arpa result Initialised 'result' data structure. */ static nss_status mdns_lookup_addr ( const void * addr, socklen_t addr_len, int af, const char * addr_str, result_map_t * result ) { DNSServiceErrorType errcode; DNSServiceRef sdref; nss_status status; if (MDNS_VERBOSE) syslog (LOG_DEBUG, "mdns: Attempting lookup of %s", addr_str ); result->hostent->h_addrtype = af; result->hostent->h_length = addr_len; // Query address becomes "address" in result. if (! add_address_to_buffer (result, addr, addr_len)) { return result->status; } result->hostent->h_name [0] = 0; errcode = DNSServiceQueryRecord ( &sdref, kDNSServiceFlagsForceMulticast, // force multicast query kDNSServiceInterfaceIndexAny, // all interfaces addr_str, // address string to query for kDNSServiceType_PTR, // pointer RRs kDNSServiceClass_IN, // internet class records mdns_lookup_callback, // callback result // Context - result buffer ); if (errcode) { syslog (LOG_WARNING, "mdns: Failed to initialise mdns lookup, error %d", errcode ); return set_err_mdns_failed (result); } status = handle_events (sdref, result, addr_str); DNSServiceRefDeallocate (sdref); return status; } /* Wait on result of callback, and process it when it arrives. Parameters sdref dns-sd reference result Initialised 'result' data structure. str lookup string, used for status/error reporting. */ static nss_status handle_events (DNSServiceRef sdref, result_map_t * result, const char * str) { int dns_sd_fd = DNSServiceRefSockFD(sdref); int nfds = dns_sd_fd + 1; fd_set readfds; struct timeval tv; int select_result; while (! result->done) { FD_ZERO(&readfds); FD_SET(dns_sd_fd, &readfds); tv = k_select_time; select_result = select (nfds, &readfds, (fd_set*)NULL, (fd_set*)NULL, &tv); if (select_result > 0) { if (FD_ISSET(dns_sd_fd, &readfds)) { if (MDNS_VERBOSE) syslog (LOG_DEBUG, "mdns: Reply received for %s", str ); DNSServiceProcessResult(sdref); } else { syslog (LOG_WARNING, "mdns: Unexpected return from select on lookup of %s", str ); } } else { // Terminate loop due to timer expiry if (MDNS_VERBOSE) syslog (LOG_DEBUG, "mdns: %s not found - timer expired", str ); set_err_notfound (result); break; } } return result->status; } /* Examine incoming data and add to relevant fields in result structure. This routine is called from DNSServiceProcessResult where appropriate. */ void mdns_lookup_callback ( DNSServiceRef sdref, DNSServiceFlags flags, uint32_t interface_index, DNSServiceErrorType error_code, const char *fullname, uint16_t rrtype, uint16_t rrclass, uint16_t rdlen, const void *rdata, uint32_t ttl, void *context ) { // A single record is received result_map_t * result = (result_map_t *) context; (void)sdref; // Unused (void)interface_index; // Unused (void)ttl; // Unused if (! (flags & kDNSServiceFlagsMoreComing) ) { result->done = 1; } if (error_code == kDNSServiceErr_NoError) { ns_type_t expected_rr_type = af_to_rr (result->hostent->h_addrtype); // Idiot check class if (rrclass != C_IN) { syslog (LOG_WARNING, "mdns: Received bad RR class: expected %d (%s)," " got %d (%s), RR type %d (%s)", C_IN, ns_class_to_str (C_IN), rrclass, ns_class_to_str (rrclass), rrtype, ns_type_to_str (rrtype) ); return; } // If a PTR if (rrtype == kDNSServiceType_PTR) { if (callback_body_ptr (fullname, result, rdlen, rdata) < 0) return; } else if (rrtype == expected_rr_type) { if (! add_hostname_or_alias ( result, fullname, strlen (fullname) ) ) { result->done = 1; return; // Abort on error } if (! add_address_to_buffer (result, rdata, rdlen) ) { result->done = 1; return; // Abort on error } } else { syslog (LOG_WARNING, "mdns: Received bad RR type: expected %d (%s)," " got %d (%s)", expected_rr_type, ns_type_to_str (expected_rr_type), rrtype, ns_type_to_str (rrtype) ); return; } if (result->status != NSS_STATUS_SUCCESS) set_err_success (result); } else { // For now, dump message to syslog and continue syslog (LOG_WARNING, "mdns: callback returned error %d", error_code ); } } static int callback_body_ptr ( const char * fullname, result_map_t * result, int rdlen, const void * rdata ) { char result_name [k_hostname_maxlen + 1]; int rv; // Fullname should be .in-addr.arpa or equivalent, which we're // not interested in. Ignore it. rv = dns_rdata_to_name (rdata, rdlen, result_name, k_hostname_maxlen); if (rv < 0) { const char * errmsg; switch (rv) { case DNS_RDATA_TO_NAME_BAD_FORMAT: errmsg = "mdns: PTR '%s' result badly formatted ('%s...')"; break; case DNS_RDATA_TO_NAME_TOO_LONG: errmsg = "mdns: PTR '%s' result too long ('%s...')"; break; case DNS_RDATA_TO_NAME_PTR: errmsg = "mdns: PTR '%s' result contained pointer ('%s...')"; break; default: errmsg = "mdns: PTR '%s' result conversion failed ('%s...')"; } syslog (LOG_WARNING, errmsg, fullname, result_name ); return -1; } if (MDNS_VERBOSE) { syslog (LOG_DEBUG, "mdns: PTR '%s' resolved to '%s'", fullname, result_name ); } // Data should be a hostname if (! add_hostname_or_alias ( result, result_name, rv ) ) { result->done = 1; return -1; } return 0; } /* Add an address to the buffer. Parameter result Result structure to write to data Incoming address data buffer Must be 'int' aligned len Length of data buffer (in bytes) Must match data alignment Result Pointer to start of newly written data, or NULL on error. If address already exists in buffer, returns pointer to that instead. */ static void * add_address_to_buffer (result_map_t * result, const void * data, int len) { int new_addr; void * start; void * temp; if ((temp = contains_address (result, data, len))) { return temp; } if (result->addrs_count >= k_addrs_max) { // Not enough addr slots set_err_internal_resource_full (result); syslog (LOG_ERR, "mdns: Internal address buffer full; increase size" ); return NULL; } // Idiot check if (len != result->hostent->h_length) { syslog (LOG_WARNING, "mdns: Unexpected rdata length for address. Expected %d, got %d", result->hostent->h_length, len ); // XXX And continue for now. } new_addr = result->addr_idx + len; if (new_addr > result->alias_idx) { // Not enough room set_err_buf_too_small (result); if (MDNS_VERBOSE) syslog (LOG_DEBUG, "mdns: Ran out of buffer when adding address %d", result->addrs_count + 1 ); return NULL; } start = result->buffer + result->addr_idx; memcpy (start, data, len); result->addr_idx = new_addr; result->header->addrs [result->addrs_count] = start; result->addrs_count ++; result->header->addrs [result->addrs_count] = NULL; return start; } static void * contains_address (result_map_t * result, const void * data, int len) { int i; // Idiot check if (len != result->hostent->h_length) { syslog (LOG_WARNING, "mdns: Unexpected rdata length for address. Expected %d, got %d", result->hostent->h_length, len ); // XXX And continue for now. } for (i = 0; result->header->addrs [i]; i++) { if (memcmp (result->header->addrs [i], data, len) == 0) { return result->header->addrs [i]; } } return NULL; } /* Add an alias to the buffer. Parameter result Result structure to write to data Incoming alias (null terminated) len Length of data buffer (in bytes), including trailing null Result Pointer to start of newly written data, or NULL on error If alias already exists in buffer, returns pointer to that instead. */ static char * add_alias_to_buffer (result_map_t * result, const char * data, int len) { int new_alias; char * start; char * temp; if ((temp = contains_alias (result, data))) { return temp; } if (result->aliases_count >= k_aliases_max) { // Not enough alias slots set_err_internal_resource_full (result); syslog (LOG_ERR, "mdns: Internal alias buffer full; increase size" ); return NULL; } new_alias = result->alias_idx - len; if (new_alias < result->addr_idx) { // Not enough room set_err_buf_too_small (result); if (MDNS_VERBOSE) syslog (LOG_DEBUG, "mdns: Ran out of buffer when adding alias %d", result->aliases_count + 1 ); return NULL; } start = result->buffer + new_alias; memcpy (start, data, len); result->alias_idx = new_alias; result->header->aliases [result->aliases_count] = start; result->aliases_count ++; result->header->aliases [result->aliases_count] = NULL; return start; } static char * contains_alias (result_map_t * result, const char * alias) { int i; for (i = 0; result->header->aliases [i]; i++) { if (strcmp (result->header->aliases [i], alias) == 0) { return result->header->aliases [i]; } } return NULL; } /* Add fully qualified hostname to result. Parameter result Result structure to write to fullname Fully qualified hostname Result Pointer to start of hostname buffer, or NULL on error (usually hostname too long) */ static char * add_hostname_len (result_map_t * result, const char * fullname, int len) { if (len >= k_hostname_maxlen) { set_err_bad_hostname (result); syslog (LOG_WARNING, "mdns: Hostname too long '%.*s': len %d, max %d", len, fullname, len, k_hostname_maxlen ); return NULL; } result->hostent->h_name = strcpy (result->header->hostname, fullname); return result->header->hostname; } /* Add fully qualified name as hostname or alias. If hostname is not fully qualified this is not an error, but the data returned may be not what the application wanted. Parameter result Result structure to write to data Incoming alias (null terminated) len Length of data buffer (in bytes), including trailing null Result Pointer to start of newly written data, or NULL on error If alias or hostname already exists, returns pointer to that instead. */ static char * add_hostname_or_alias (result_map_t * result, const char * data, int len) { char * hostname = result->hostent->h_name; if (*hostname) { if (strcmp (hostname, data) == 0) { return hostname; } else { return add_alias_to_buffer (result, data, len); } } else { return add_hostname_len (result, data, len); } } static int init_result ( result_map_t * result, hostent * result_buf, char * buf, size_t buflen ) { if (buflen < sizeof (buf_header_t)) { return ERANGE; } result->hostent = result_buf; result->header = (buf_header_t *) buf; result->header->hostname[0] = 0; result->aliases_count = 0; result->header->aliases[0] = NULL; result->addrs_count = 0; result->header->addrs[0] = NULL; result->buffer = buf + sizeof (buf_header_t); result->addr_idx = 0; result->alias_idx = buflen - sizeof (buf_header_t); result->done = 0; set_err_notfound (result); // Point hostent to the right buffers result->hostent->h_name = result->header->hostname; result->hostent->h_aliases = result->header->aliases; result->hostent->h_addr_list = result->header->addrs; return 0; } /* Set the status in the result. Parameters result Result structure to update status New nss_status value err New errno value herr New h_errno value Returns New status value */ static nss_status set_err (result_map_t * result, nss_status status, int err, int herr) { result->status = status; result->r_errno = err; result->r_h_errno = herr; return status; } static nss_status set_err_notfound (result_map_t * result) { return set_err (result, NSS_STATUS_NOTFOUND, ENOENT, HOST_NOT_FOUND); } static nss_status set_err_bad_hostname (result_map_t * result) { return set_err (result, NSS_STATUS_TRYAGAIN, ENOENT, NO_RECOVERY); } static nss_status set_err_buf_too_small (result_map_t * result) { return set_err (result, NSS_STATUS_TRYAGAIN, ERANGE, NETDB_INTERNAL); } static nss_status set_err_internal_resource_full (result_map_t * result) { return set_err (result, NSS_STATUS_RETURN, ERANGE, NO_RECOVERY); } static nss_status set_err_system (result_map_t * result) { return set_err (result, NSS_STATUS_UNAVAIL, errno, NETDB_INTERNAL); } static nss_status set_err_mdns_failed (result_map_t * result) { return set_err (result, NSS_STATUS_TRYAGAIN, EAGAIN, TRY_AGAIN); } static nss_status set_err_success (result_map_t * result) { result->status = NSS_STATUS_SUCCESS; return result->status; } /* Test whether name is applicable for mdns to process, and if so copy into lookup_name buffer (if non-NULL). Returns Pointer to name to lookup up, if applicable, or NULL otherwise. */ static const char * is_applicable_name ( result_map_t * result, const char * name, char * lookup_name ) { int match = config_is_mdns_suffix (name); if (match > 0) { if (lookup_name) { strncpy (lookup_name, name, k_hostname_maxlen + 1); return lookup_name; } else { return name; } } else { if (match < 0) { set_err_system (result); } return NULL; } } /* Test whether address is applicable for mdns to process, and if so copy into addr_str buffer as an address suitable for ptr lookup. Returns Pointer to name to lookup up, if applicable, or NULL otherwise. */ static const char * is_applicable_addr ( result_map_t * result, const void * addr, int af, char * addr_str ) { int match; if (! format_reverse_addr (af, addr, -1, addr_str)) { if (MDNS_VERBOSE) syslog (LOG_DEBUG, "mdns: Failed to create reverse address" ); return NULL; } if (MDNS_VERBOSE) syslog (LOG_DEBUG, "mdns: Reverse address: %s", addr_str ); match = config_is_mdns_suffix (addr_str); if (match > 0) { return addr_str; } else { if (match < 0) { set_err_system (result); } return NULL; } } //---------- // Types and Constants const char * k_conf_file = "/etc/nss_mdns.conf"; #define CONF_LINE_SIZE 1024 const char k_comment_char = '#'; const char * k_keyword_domain = "domain"; const char * k_default_domains [] = { "local", "254.169.in-addr.arpa", "8.e.f.ip6.int", "8.e.f.ip6.arpa", "9.e.f.ip6.int", "9.e.f.ip6.arpa", "a.e.f.ip6.int", "a.e.f.ip6.arpa", "b.e.f.ip6.int", "b.e.f.ip6.arpa", NULL // Always null terminated }; // Linked list of domains typedef struct domain_entry { char * domain; struct domain_entry * next; } domain_entry_t; // Config typedef struct { domain_entry_t * domains; } config_t; const config_t k_empty_config = { NULL }; // Context - tracks position in config file, used for error reporting typedef struct { const char * filename; int linenum; } config_file_context_t; //---------- // Local prototypes static errcode_t load_config (config_t * conf); static errcode_t process_config_line ( config_t * conf, char * line, config_file_context_t * context ); static char * get_next_word (char * input, char **next); static errcode_t default_config (config_t * conf); static errcode_t add_domain (config_t * conf, const char * domain); static int contains_domain (const config_t * conf, const char * domain); static int contains_domain_suffix (const config_t * conf, const char * addr); //---------- // Global variables static config_t * g_config = NULL; // Configuration info pthread_mutex_t g_config_mutex = #ifdef PTHREAD_ERRORCHECK_MUTEX_INITIALIZER_NP PTHREAD_ERRORCHECK_MUTEX_INITIALIZER_NP; #else PTHREAD_MUTEX_INITIALIZER; #endif //---------- // Configuration functions /* Initialise the configuration from the config file. Returns 0 success non-zero error code on failure */ errcode_t init_config () { if (g_config) { /* Safe to test outside mutex. If non-zero, initialisation is complete and g_config can be safely used read-only. If zero, then we do proper mutex testing before initialisation. */ return 0; } else { int errcode = -1; int presult; config_t * temp_config; // Acquire mutex presult = pthread_mutex_lock (&g_config_mutex); if (presult) { syslog (LOG_ERR, "mdns: Fatal mutex lock error in nss_mdns:init_config, %s:%d: %d: %s", __FILE__, __LINE__, presult, strerror (presult) ); return presult; } // Test again now we have mutex, in case initialisation occurred while // we were waiting if (! g_config) { temp_config = (config_t *) malloc (sizeof (config_t)); if (temp_config) { // Note: This code will leak memory if initialisation fails // repeatedly. This should only happen in the case of a memory // error, so I'm not sure if it's a meaningful problem. - AW *temp_config = k_empty_config; errcode = load_config (temp_config); if (! errcode) { g_config = temp_config; } } else { syslog (LOG_ERR, "mdns: Can't allocate memory in nss_mdns:init_config, %s:%d", __FILE__, __LINE__ ); errcode = errno; } } presult = pthread_mutex_unlock (&g_config_mutex); if (presult) { syslog (LOG_ERR, "mdns: Fatal mutex unlock error in nss_mdns:init_config, %s:%d: %d: %s", __FILE__, __LINE__, presult, strerror (presult) ); errcode = presult; } return errcode; } } int config_is_mdns_suffix (const char * name) { int errcode = init_config (); if (! errcode) { return contains_domain_suffix (g_config, name); } else { errno = errcode; return -1; } } //---------- // Local functions static errcode_t load_config (config_t * conf) { FILE * cf; char line [CONF_LINE_SIZE]; config_file_context_t context; context.filename = k_conf_file; context.linenum = 0; cf = fopen (context.filename, "r"); if (! cf) { syslog (LOG_INFO, "mdns: Couldn't open nss_mdns configuration file %s, using default.", context.filename ); return default_config (conf); } while (fgets (line, CONF_LINE_SIZE, cf)) { int errcode; context.linenum++; errcode = process_config_line (conf, line, &context); if (errcode) { // Critical error, give up fclose(cf); return errcode; } } fclose (cf); return 0; } /* Parse a line of the configuration file. For each keyword recognised, perform appropriate handling. If the keyword is not recognised, print a message to syslog and continue. Returns 0 success, or recoverable config file error non-zero serious system error, processing aborted */ static errcode_t process_config_line ( config_t * conf, char * line, config_file_context_t * context ) { char * curr = line; char * word; word = get_next_word (curr, &curr); if (! word || word [0] == k_comment_char) { // Nothing interesting on this line return 0; } if (strcmp (word, k_keyword_domain) == 0) { word = get_next_word (curr, &curr); if (word) { int errcode = add_domain (conf, word); if (errcode) { // something badly wrong, bail return errcode; } if (get_next_word (curr, NULL)) { syslog (LOG_WARNING, "%s, line %d: ignored extra text found after domain", context->filename, context->linenum ); } } else { syslog (LOG_WARNING, "%s, line %d: no domain specified", context->filename, context->linenum ); } } else { syslog (LOG_WARNING, "%s, line %d: unknown keyword %s - skipping", context->filename, context->linenum, word ); } return 0; } /* Get next word (whitespace separated) from input string. A null character is written into the first whitespace character following the word. Parameters input Input string. This string is modified by get_next_word. next If non-NULL and the result is non-NULL, a pointer to the character following the end of the word (after the null) is written to 'next'. If no word is found, the original value is unchanged. If the word extended to the end of the string, 'next' points to the trailling NULL. It is safe to pass 'str' as 'input' and '&str' as 'next'. Returns Pointer to the first non-whitespace character (and thus word) found. if no word is found, returns NULL. */ static char * get_next_word (char * input, char **next) { char * curr = input; char * result; while (isspace (*curr)) { curr ++; } if (*curr == 0) { return NULL; } result = curr; while (*curr && ! isspace (*curr)) { curr++; } if (*curr) { *curr = 0; if (next) { *next = curr+1; } } else { if (next) { *next = curr; } } return result; } static errcode_t default_config (config_t * conf) { int i; for (i = 0; k_default_domains [i]; i++) { int errcode = add_domain (conf, k_default_domains [i]); if (errcode) { // Something has gone (badly) wrong - let's bail return errcode; } } return 0; } static errcode_t add_domain (config_t * conf, const char * domain) { if (! contains_domain (conf, domain)) { domain_entry_t * d = (domain_entry_t *) malloc (sizeof (domain_entry_t)); if (! d) { syslog (LOG_ERR, "mdns: Can't allocate memory in nss_mdns:init_config, %s:%d", __FILE__, __LINE__ ); return ENOMEM; } d->domain = strdup (domain); if (! d->domain) { syslog (LOG_ERR, "mdns: Can't allocate memory in nss_mdns:init_config, %s:%d", __FILE__, __LINE__ ); free (d); return ENOMEM; } d->next = conf->domains; conf->domains = d; } return 0; } static int contains_domain (const config_t * conf, const char * domain) { const domain_entry_t * curr = conf->domains; while (curr != NULL) { if (strcasecmp (curr->domain, domain) == 0) { return 1; } curr = curr->next; } return 0; } static int contains_domain_suffix (const config_t * conf, const char * addr) { const domain_entry_t * curr = conf->domains; while (curr != NULL) { if (cmp_dns_suffix (addr, curr->domain) > 0) { return 1; } curr = curr->next; } return 0; } //---------- // Types and Constants static const char * k_local_suffix = "local"; static const char k_dns_separator = '.'; static const int k_label_maxlen = DNS_LABEL_MAXLEN; // Label entries longer than this are actually pointers. typedef struct { int value; const char * name; const char * comment; } table_entry_t; static const table_entry_t k_table_af [] = { { AF_UNSPEC, NULL, NULL }, { AF_LOCAL, "LOCAL", NULL }, { AF_UNIX, "UNIX", NULL }, { AF_INET, "INET", NULL }, { AF_INET6, "INET6", NULL } }; static const int k_table_af_size = sizeof (k_table_af) / sizeof (* k_table_af); static const char * k_table_ns_class [] = { NULL, "IN" }; static const int k_table_ns_class_size = sizeof (k_table_ns_class) / sizeof (* k_table_ns_class); static const char * k_table_ns_type [] = { NULL, "A", "NS", "MD", "MF", "CNAME", "SOA", "MB", "MG", "MR", "NULL", "WKS", "PTR", "HINFO", "MINFO", "MX", "TXT", "RP", "AFSDB", "X25", "ISDN", "RT", "NSAP", NULL, "SIG", "KEY", "PX", "GPOS", "AAAA", "LOC", "NXT", "EID", "NIMLOC", "SRV", "ATMA", "NAPTR", "KX", "CERT", "A6", "DNAME", "SINK", "OPT" }; static const int k_table_ns_type_size = sizeof (k_table_ns_type) / sizeof (* k_table_ns_type); //---------- // Local prototypes static int simple_table_index (const char * table [], int size, const char * str); static int table_index_name (const table_entry_t table [], int size, const char * str); static int table_index_value (const table_entry_t table [], int size, int n); //---------- // Global variables //---------- // Util functions int count_dots (const char * name) { int count = 0; int i; for (i = 0; name[i]; i++) { if (name [i] == k_dns_separator) count++; } return count; } int islocal (const char * name) { return cmp_dns_suffix (name, k_local_suffix) > 0; } int rr_to_af (ns_type_t rrtype) { switch (rrtype) { case kDNSServiceType_A: return AF_INET; case kDNSServiceType_AAAA: return AF_INET6; default: return AF_UNSPEC; } } ns_type_t af_to_rr (int af) { switch (af) { case AF_INET: return kDNSServiceType_A; case AF_INET6: return kDNSServiceType_AAAA; default: //return ns_t_invalid; return 0; } } int str_to_af (const char * str) { int result = table_index_name (k_table_af, k_table_af_size, str); if (result < 0) result = 0; return k_table_af [result].value; } ns_class_t str_to_ns_class (const char * str) { return (ns_class_t) simple_table_index (k_table_ns_class, k_table_ns_class_size, str); } ns_type_t str_to_ns_type (const char * str) { return (ns_type_t) simple_table_index (k_table_ns_type, k_table_ns_type_size, str); } const char * af_to_str (int in) { int result = table_index_value (k_table_af, k_table_af_size, in); if (result < 0) result = 0; return k_table_af [result].name; } const char * ns_class_to_str (ns_class_t in) { if (in < k_table_ns_class_size) return k_table_ns_class [in]; else return NULL; } const char * ns_type_to_str (ns_type_t in) { if (in < k_table_ns_type_size) return k_table_ns_type [in]; else return NULL; } char * format_reverse_addr_in ( const struct in_addr * addr, int prefixlen, char * buf ) { char * curr = buf; int i; const uint8_t * in_addr_a = (uint8_t *) addr; if (prefixlen > 32) return NULL; if (prefixlen < 0) prefixlen = 32; i = (prefixlen + 7) / 8; // divide prefixlen into bytes, rounding up while (i > 0) { i--; curr += sprintf (curr, "%d.", in_addr_a [i]); } sprintf (curr, "in-addr.arpa"); return buf; } char * format_reverse_addr_in6 ( const struct in6_addr * addr, int prefixlen, char * buf ) { char * curr = buf; int i; const uint8_t * in_addr_a = (uint8_t *) addr; if (prefixlen > 128) return NULL; if (prefixlen < 0) prefixlen = 128; i = (prefixlen + 3) / 4; // divide prefixlen into nibbles, rounding up // Special handling for first if (i % 2) { curr += sprintf (curr, "%d.", (in_addr_a [i/2] >> 4) & 0x0F); } i >>= 1; // Convert i to bytes (divide by 2) while (i > 0) { uint8_t val; i--; val = in_addr_a [i]; curr += sprintf (curr, "%x.%x.", val & 0x0F, (val >> 4) & 0x0F); } sprintf (curr, "ip6.arpa"); return buf; } char * format_reverse_addr ( int af, const void * addr, int prefixlen, char * buf ) { switch (af) { case AF_INET: return format_reverse_addr_in ( (struct in_addr *) addr, prefixlen, buf ); break; case AF_INET6: return format_reverse_addr_in6 ( (struct in6_addr *) addr, prefixlen, buf ); break; default: return NULL; } } int cmp_dns_suffix (const char * name, const char * domain) { const char * nametail; const char * domaintail; // Idiot checks if (*name == 0 || *name == k_dns_separator) { // Name can't be empty or start with separator return CMP_DNS_SUFFIX_BAD_NAME; } if (*domain == 0) { return CMP_DNS_SUFFIX_SUCCESS; // trivially true } if (*domain == k_dns_separator) { // drop leading separator from domain domain++; if (*domain == k_dns_separator) { return CMP_DNS_SUFFIX_BAD_DOMAIN; } } // Find ends of strings for (nametail = name; *nametail; nametail++) ; for (domaintail = domain; *domaintail; domaintail++) ; // Shuffle back to last real character, and drop any trailing '.' // while we're at it. nametail --; if (*nametail == k_dns_separator) { nametail --; if (*nametail == k_dns_separator) { return CMP_DNS_SUFFIX_BAD_NAME; } } domaintail --; if (*domaintail == k_dns_separator) { domaintail --; if (*domaintail == k_dns_separator) { return CMP_DNS_SUFFIX_BAD_DOMAIN; } } // Compare. while ( nametail >= name && domaintail >= domain && tolower(*nametail) == tolower(*domaintail)) { nametail--; domaintail--; } /* A successful finish will be one of the following: (leading and trailing . ignored) name : domain2.domain1 domain: domain2.domain1 ^ name : domain3.domain2.domain1 domain: domain2.domain1 ^ */ if ( domaintail < domain && (nametail < name || *nametail == k_dns_separator) ) { return CMP_DNS_SUFFIX_SUCCESS; } else { return CMP_DNS_SUFFIX_FAILURE; } } int dns_rdata_to_name (const char * rdata, int rdlen, char * name, int name_len) { int i = 0; // Index into 'name' const char * rdata_curr = rdata; if (rdlen == 0) return DNS_RDATA_TO_NAME_BAD_FORMAT; /* In RDATA, a DNS name is stored as a series of labels. Each label consists of a length octet (max value 63) followed by the data for that label. The series is terminated with a length 0 octet. A length octet beginning with bits 11 is a pointer to somewhere else in the payload, but we don't support these since we don't have access to the entire payload. See RFC1034 section 3.1 and RFC1035 section 3.1. */ while (1) { int term_len = *rdata_curr; rdata_curr++; if (term_len == 0) { break; // 0 length record terminates label } else if (term_len > k_label_maxlen) { name [i] = 0; return DNS_RDATA_TO_NAME_PTR; } else if (rdata_curr + term_len > rdata + rdlen) { name [i] = 0; return DNS_RDATA_TO_NAME_BAD_FORMAT; } if (name_len < i + term_len + 1) // +1 is separator { name [i] = 0; return DNS_RDATA_TO_NAME_TOO_LONG; } memcpy (name + i, rdata_curr, term_len); i += term_len; rdata_curr += term_len; name [i] = k_dns_separator; i++; } name [i] = 0; return i; } //---------- // Local functions /* Find the index of an string entry in a table. A case insenitive match is performed. If no entry is found, 0 is returned. Parameters table Lookup table Table entries may be NULL. NULL entries will never match. size number of entries in table str lookup string Result index of first matching entry, or 0 if no matches */ static int simple_table_index (const char * table [], int size, const char * str) { int i; for (i = 0; i < size; i++) { if ( table [i] && (strcasecmp (table [i], str) == 0) ) { return i; } } return 0; } /* Find the index of a name in a table. Parameters table array of table_entry_t records. The name field is compared (ignoring case) to the input string. size number of entries in table str lookup string Result index of first matching entry, or -1 if no matches */ static int table_index_name (const table_entry_t table [], int size, const char * str) { int i; for (i = 0; i < size; i++) { if ( table [i].name && (strcasecmp (table [i].name, str) == 0) ) { return i; } } return -1; } /* Find the index of a value a table. Parameters table array of table_entry_t records. The value field is compared to the input value size number of entries in table n lookup value Result index of first matching entry, or -1 if no matches */ static int table_index_value (const table_entry_t table [], int size, int n) { int i; for (i = 0; i < size; i++) { if (table [i].value == n) { return i; } } return -1; }