adafruit-mirror/arduino-esp32
1
0
Fork 0
Code Issues Pull requests Projects Releases Packages Wiki Activity

Proper EDNS handling and cleaner NOERROR response in DNSSERVER (#11411)

Browse source 
* Proper EDNS handling and cleaner NOERROR response

* fix:  library.properties

reverting version number update - as it is done automatically

* ci(pre-commit): Apply automatic fixes

* Spelling Corrected  and minor clarification in comments

* Removing commented out code fragments

* ci(pre-commit): Apply automatic fixes

* fix(pr): Fix typo

---------

Co-authored-by: pre-commit-ci-lite[bot] <117423508+pre-commit-ci-lite[bot]@users.noreply.github.com>
Co-authored-by: Me No Dev <me-no-dev@users.noreply.github.com>
This commit is contained in:
Olaf 2025-06-20 11:52:21 +02:00 committed by GitHub
parent 016077e245
commit 23c6abc1ac
No known key found for this signature in database
GPG key ID: B5690EEEBB952194
2 changed files with 104 additions and 4 deletions
Show stats Download patch file Download diff file Expand all files Collapse all files

86
libraries/DNSServer/src/DNSServer.cpp
View file

@ -111,16 +111,22 @@ void DNSServer::_handleUDP(AsyncUDPPacket &pkt) {
// will reply with IP only to "*" or if domain matches without www. subdomain
if (dnsHeader.OPCode == DNS_OPCODE_QUERY && requestIncludesOnlyOneQuestion(dnsHeader)
&& (_domainName.isEmpty() || getDomainNameWithoutWwwPrefix(static_cast<const unsigned char *>(dnsQuestion.QName), dnsQuestion.QNameLength) == _domainName)) {
replyWithIP(pkt, dnsHeader, dnsQuestion);
// Qtype = A (1) or ANY (255): send an A record otherwise an empty response
if (ntohs(dnsQuestion.QType) == 1 || ntohs(dnsQuestion.QType) == 255) {
replyWithIP(pkt, dnsHeader, dnsQuestion);
} else {
replyWithNoAnsw(pkt, dnsHeader, dnsQuestion);
}
return;
}
// otherwise reply with custom code
replyWithCustomCode(pkt, dnsHeader);
}
bool DNSServer::requestIncludesOnlyOneQuestion(DNSHeader &dnsHeader) {
return ntohs(dnsHeader.QDCount) == 1 && dnsHeader.ANCount == 0 && dnsHeader.NSCount == 0 && dnsHeader.ARCount == 0;
dnsHeader.ARCount = 0; // We assume that if ARCount !=0 there is a EDNS OPT packet, just ignore
return ntohs(dnsHeader.QDCount) == 1 && dnsHeader.ANCount == 0 && dnsHeader.NSCount == 0;
}
String DNSServer::getDomainNameWithoutWwwPrefix(const unsigned char *start, size_t len) {
@ -139,7 +145,6 @@ String DNSServer::getDomainNameWithoutWwwPrefix(const unsigned char *start, size
void DNSServer::replyWithIP(AsyncUDPPacket &req, DNSHeader &dnsHeader, DNSQuestion &dnsQuestion) {
AsyncUDPMessage rpl;
// Change the type of message to a response and set the number of answers equal to
// the number of questions in the header
dnsHeader.QR = DNS_QR_RESPONSE;
@ -187,3 +192,76 @@ void DNSServer::replyWithCustomCode(AsyncUDPPacket &req, DNSHeader &dnsHeader) {
rpl.write(reinterpret_cast<const uint8_t *>(&dnsHeader), sizeof(DNSHeader));
_udp.sendTo(rpl, req.remoteIP(), req.remotePort());
}
void DNSServer::replyWithNoAnsw(AsyncUDPPacket &req, DNSHeader &dnsHeader, DNSQuestion &dnsQuestion) {
dnsHeader.QR = DNS_QR_RESPONSE;
dnsHeader.ANCount = 0;
dnsHeader.NSCount = htons(1);
AsyncUDPMessage rpl;
rpl.write(reinterpret_cast<const uint8_t *>(&dnsHeader), sizeof(DNSHeader));
// Write the question
rpl.write(dnsQuestion.QName, dnsQuestion.QNameLength);
rpl.write((uint8_t *)&dnsQuestion.QType, 2);
rpl.write((uint8_t *)&dnsQuestion.QClass, 2);
// An empty answer contains an authority section with a SOA,
// We take the name of the query as the root of the zone for which the SOA is generated
// and use a value of DNS_MINIMAL_TTL seconds in order to minimize negative caching
// Write the authority section:
// The SOA RR's ownername is set equal to the query name, and we use made up names for
// the MNAME and RNAME - it doesn't really matter from a protocol perspective - as for
// a no such QTYPE answer only the timing fields are used.
// a protocol perspective - it
// Use DNS name compression : instead of repeating the name in this RNAME occurrence,
// set the two MSB of the byte corresponding normally to the length to 1. The following
// 14 bits must be used to specify the offset of the domain name in the message
// (<255 here so the first byte has the 6 LSB at 0)
rpl.write((uint8_t)0xC0);
rpl.write((uint8_t)DNS_OFFSET_DOMAIN_NAME);
// DNS type A : host address, DNS class IN for INternet, returning an IPv4 address
uint16_t answerType = htons(DNS_TYPE_SOA), answerClass = htons(DNS_CLASS_IN);
uint32_t Serial = htonl(DNS_SOA_SERIAL); // Date type serial based on the date this piece of code was written
uint32_t Refresh = htonl(DNS_SOA_REFRESH); // These timers don't matter, we don't serve zone transfers
uint32_t Retry = htonl(DNS_SOA_RETRY);
uint32_t Expire = htonl(DNS_SOA_EXPIRE);
uint32_t MinTTL = htonl(DNS_MINIMAL_TTL); // See RFC2308 section 5
char MLabel[] = DNS_SOA_MNAME_LABEL;
char RLabel[] = DNS_SOA_RNAME_LABEL;
char PostFixLabel[] = DNS_SOA_POSTFIX_LABEL;
// 4 accounts for len fields and for both rname
// and lname and their postfix labels and there are 5 32 bit fields
uint16_t RdataLength = htons((uint16_t)(strlen(MLabel) + strlen(RLabel) + 2 * strlen(PostFixLabel) + 4 + 5 * sizeof(Serial)));
rpl.write((unsigned char *)&answerType, 2);
rpl.write((unsigned char *)&answerClass, 2);
rpl.write((unsigned char *)&MinTTL, 4); // DNS Time To Live
rpl.write((unsigned char *)&RdataLength, 2);
rpl.write((uint8_t)strlen(MLabel));
rpl.write((unsigned char *)&MLabel, strlen(MLabel));
rpl.write((unsigned char *)&PostFixLabel, strlen(PostFixLabel));
rpl.write((uint8_t)0);
// rpl.write((uint8_t)0xC0);
// rpl.write((uint8_t)DNS_OFFSET_DOMAIN_NAME);
rpl.write((uint8_t)strlen(RLabel));
rpl.write((unsigned char *)&RLabel, strlen(RLabel));
rpl.write((unsigned char *)&PostFixLabel, strlen(PostFixLabel));
rpl.write((uint8_t)0);
rpl.write((unsigned char *)&Serial, 4);
rpl.write((unsigned char *)&Refresh, 4);
rpl.write((unsigned char *)&Retry, 4);
rpl.write((unsigned char *)&Expire, 4);
rpl.write((unsigned char *)&MinTTL, 4);
_udp.sendTo(rpl, req.remoteIP(), req.remotePort());
}

22
libraries/DNSServer/src/DNSServer.h
View file

@ -9,6 +9,26 @@
#define DNS_OFFSET_DOMAIN_NAME DNS_HEADER_SIZE // Offset in bytes to reach the domain name labels in the DNS message
#define DNS_DEFAULT_PORT 53
#define DNS_SOA_MNAME_LABEL "ns"
#define DNS_SOA_RNAME_LABEL "esp32"
// The POSTFIX_LABEL will be concatenated to the RName and MName Label label
// do not use a multilabel name here. "local" is a good choice as it is reserved for
// local use by IANA
// The postfix label is defined as an array of characters that follows the
// definition of RFC1035 3.1
// for instance, a postfix of example.com would be defined as:
// #define DNS_SOA_POSTFIX_LABEL {'\7', 'e', 'x', 'a', 'm', 'p', 'l', 'e', '\3', 'c', 'o', 'm', '\0'}
#define DNS_SOA_POSTFIX_LABEL \
{ '\5', 'l', 'o', 'c', 'a', 'l', '\0' }
// From the following values only the MINIMAL_TTL has relevance
// in the context of client-server protocol interactions.
// The other values are arbitrary chosen as they are only relevant for
// in a zone-transfer scenario.
#define DNS_SOA_SERIAL 2025052900 // Arbitrary serial (format: YYYYMMDDnn)
#define DNS_SOA_REFRESH 100000 // Arbitrary (seconds)
#define DNS_SOA_RETRY 10000 // Arbitrary (seconds)
#define DNS_SOA_EXPIRE 1000000 // Arbitrary (seconds)
#define DNS_MINIMAL_TTL 5 // Time to live for negative answers RFC2308
enum class DNSReplyCode : uint16_t {
NoError = 0,
FormError = 1,
@ -179,5 +199,7 @@ private:
inline bool requestIncludesOnlyOneQuestion(DNSHeader &dnsHeader);
void replyWithIP(AsyncUDPPacket &req, DNSHeader &dnsHeader, DNSQuestion &dnsQuestion);
inline void replyWithCustomCode(AsyncUDPPacket &req, DNSHeader &dnsHeader);
inline void replyWithNoAnsw(AsyncUDPPacket &req, DNSHeader &dnsHeader, DNSQuestion &dnsQuestion);
void _handleUDP(AsyncUDPPacket &pkt);
};