From c4c207a85e3dc20f9bcd6370d4d6f99f173a989d Mon Sep 17 00:00:00 2001 From: Me No Dev Date: Mon, 1 Aug 2016 06:48:23 +0300 Subject: [PATCH] Optimize MDNS to prevent overflow and endless loop (#2333) * Optimize MDNS to prevent overflow and endless loop * Handle better non-esp services * leave debug off * better name resolution for external devices * strip name length (did not show in IDE) --- libraries/ESP8266mDNS/ESP8266mDNS.cpp | 62 +++++++++++++++++++++------ 1 file changed, 48 insertions(+), 14 deletions(-) diff --git a/libraries/ESP8266mDNS/ESP8266mDNS.cpp b/libraries/ESP8266mDNS/ESP8266mDNS.cpp index 72924071ac..4da5df8173 100644 --- a/libraries/ESP8266mDNS/ESP8266mDNS.cpp +++ b/libraries/ESP8266mDNS/ESP8266mDNS.cpp @@ -493,11 +493,11 @@ void MDNSResponder::_parsePacket(){ return; } - int numAnswers = packetHeader[3]; + int numAnswers = packetHeader[3] + packetHeader[5]; // Assume that the PTR answer always comes first and that it is always accompanied by a TXT, SRV, AAAA (optional) and A answer in the same packet. if (numAnswers < 4) { #ifdef MDNS_DEBUG_RX - Serial.println("Expected a packet with 4 answers, returning"); + Serial.printf("Expected a packet with 4 or more answers, got %u\n", numAnswers); #endif _conn->flush(); return; @@ -510,11 +510,14 @@ void MDNSResponder::_parsePacket(){ bool serviceMatch = false; MDNSAnswer *answer; uint8_t partsCollected = 0; + uint8_t stringsRead = 0; + + answerHostName[0] = '\0'; // Clear answer list if (_newQuery) { - int numAnswers = _getNumAnswers(); - for (int n = numAnswers - 1; n >= 0; n--) { + int oldAnswers = _getNumAnswers(); + for (int n = oldAnswers - 1; n >= 0; n--) { answer = _getAnswerFromIdx(n); os_free(answer->hostname); os_free(answer); @@ -526,21 +529,29 @@ void MDNSResponder::_parsePacket(){ while (numAnswers--) { // Read name + stringsRead = 0; do { tmp8 = _conn_read8(); if (tmp8 & 0xC0) { // Compressed pointer (not supported) tmp8 = _conn_read8(); break; } - if (tmp8 == 0x00) { // Énd of name + if (tmp8 == 0x00) { // End of name break; } + if(stringsRead > 3){ +#ifdef MDNS_DEBUG_RX + Serial.println("failed to read the response name"); +#endif + _conn->flush(); + return; + } _conn_readS(serviceName, tmp8); serviceName[tmp8] = '\0'; #ifdef MDNS_DEBUG_RX Serial.printf(" %d ", tmp8); for (int n = 0; n < tmp8; n++) { - Serial.printf("%02x ", serviceName[n]); + Serial.printf("%c", serviceName[n]); } Serial.println(); #endif @@ -552,6 +563,7 @@ void MDNSResponder::_parsePacket(){ #endif } } + stringsRead++; } while (true); uint16_t answerType = _conn_read16(); // Read type @@ -559,6 +571,18 @@ void MDNSResponder::_parsePacket(){ uint32_t answerTtl = _conn_read32(); // Read ttl uint16_t answerRdlength = _conn_read16(); // Read rdlength + if(answerRdlength > 255){ + if(answerType == MDNS_TYPE_TXT && answerRdlength < 1460){ + while(--answerRdlength) _conn->read(); + } else { +#ifdef MDNS_DEBUG_RX + Serial.printf("Data len too long! %u\n", answerRdlength); +#endif + _conn->flush(); + return; + } + } + #ifdef MDNS_DEBUG_RX Serial.printf("type: %04x rdlength: %d\n", answerType, answerRdlength); #endif @@ -566,9 +590,14 @@ void MDNSResponder::_parsePacket(){ if (answerType == MDNS_TYPE_PTR) { partsCollected |= 0x01; _conn_readS(hostName, answerRdlength); // Read rdata + if(hostName[answerRdlength-2] & 0xc0){ + memcpy(answerHostName, hostName+1, answerRdlength-3); + answerHostName[answerRdlength-3] = '\0'; + } #ifdef MDNS_DEBUG_RX + Serial.printf("PTR %d ", answerRdlength); for (int n = 0; n < answerRdlength; n++) { - Serial.printf("%02x ", hostName[n]); + Serial.printf("%c", hostName[n]); } Serial.println(); #endif @@ -578,8 +607,9 @@ void MDNSResponder::_parsePacket(){ partsCollected |= 0x02; _conn_readS(hostName, answerRdlength); // Read rdata #ifdef MDNS_DEBUG_RX + Serial.printf("TXT %d ", answerRdlength); for (int n = 0; n < answerRdlength; n++) { - Serial.printf("%02x ", hostName[n]); + Serial.printf("%c", hostName[n]); } Serial.println(); #endif @@ -594,14 +624,16 @@ void MDNSResponder::_parsePacket(){ // Read hostname tmp8 = _conn_read8(); if (tmp8 & 0xC0) { // Compressed pointer (not supported) +#ifdef MDNS_DEBUG_RX Serial.println("Skipping compressed pointer"); +#endif tmp8 = _conn_read8(); } else { _conn_readS(answerHostName, tmp8); answerHostName[tmp8] = '\0'; #ifdef MDNS_DEBUG_RX - Serial.printf(" %d ", tmp8); + Serial.printf("SRV %d ", tmp8); for (int n = 0; n < tmp8; n++) { Serial.printf("%02x ", answerHostName[n]); } @@ -621,7 +653,7 @@ void MDNSResponder::_parsePacket(){ } else { #ifdef MDNS_DEBUG_RX - Serial.printf("Ignoring unsupported type %d\n", tmp8); + Serial.printf("Ignoring unsupported type %02x\n", tmp8); #endif for (int n = 0; n < answerRdlength; n++) (void)_conn_read8(); @@ -654,6 +686,8 @@ void MDNSResponder::_parsePacket(){ } answer->hostname = (char *)os_malloc(strlen(answerHostName) + 1); os_strcpy(answer->hostname, answerHostName); + _conn->flush(); + return; } } @@ -663,7 +697,7 @@ void MDNSResponder::_parsePacket(){ // PARSE REQUEST NAME - hostNameLen = _conn_read8(); + hostNameLen = _conn_read8() % 255; _conn_readS(hostName, hostNameLen); hostName[hostNameLen] = '\0'; @@ -685,7 +719,7 @@ void MDNSResponder::_parsePacket(){ } if(!serviceParsed){ - serviceNameLen = _conn_read8(); + serviceNameLen = _conn_read8() % 255; _conn_readS(serviceName, serviceNameLen); serviceName[serviceNameLen] = '\0'; @@ -718,7 +752,7 @@ void MDNSResponder::_parsePacket(){ } if(!protoParsed){ - protoNameLen = _conn_read8(); + protoNameLen = _conn_read8() % 255; _conn_readS(protoName, protoNameLen); protoName[protoNameLen] = '\0'; if(protoNameLen == 4 && protoName[0] == '_'){ @@ -740,7 +774,7 @@ void MDNSResponder::_parsePacket(){ if(!localParsed){ char localName[32]; - uint8_t localNameLen = _conn_read8(); + uint8_t localNameLen = _conn_read8() % 31; _conn_readS(localName, localNameLen); localName[localNameLen] = '\0'; tmp = _conn_read8();