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-rw-r--r--src/dns.c72
-rw-r--r--src/dns.h61
-rw-r--r--src/main.c53
3 files changed, 138 insertions, 48 deletions
diff --git a/src/dns.c b/src/dns.c
index 6cdae43..b8e4d22 100644
--- a/src/dns.c
+++ b/src/dns.c
@@ -5,8 +5,52 @@
#include "dns.h"
+int dns_construct_header ( struct dns_header* _header, char* _buffer, int _bufflen )
+{
+ if ( !_buffer || !_header || _bufflen < 12 )
+ return -1;
+
+ *((uint16_t*)_buffer) = _header->id; //Since only copied, no flipping necessary
+ _buffer[2] =
+ ((_header->QR & 0x01) << 7) |
+ ((_header->OPCODE & 0x0F) << 3) |
+ ((_header->AA & 0x01) << 2) |
+ ((_header->TC & 0x01) << 1) |
+ ( _header->RD & 0x01);
+ _buffer[3] =
+ ((_header->RA & 0x01) << 7) |
+ ((_header->Z & 0x07) << 4) |
+ ( _header->RCODE & 0x0F);
+ *((uint16_t*)(_buffer + 4 )) = FLIP_BYTES(_header->question_count);
+ *((uint16_t*)(_buffer + 6 )) = FLIP_BYTES(_header->answer_count);
+ *((uint16_t*)(_buffer + 8 )) = FLIP_BYTES(_header->authorative_count);
+ *((uint16_t*)(_buffer + 10)) = FLIP_BYTES(_header->additional_count);
+
+ return 12;
+}
+
+int dns_destroy_struct ( struct dns_message* _msg )
+{
+ if ( !_msg )
+ return -1;
+
+ if ( _msg->question_count > 0 && _msg->question) {
+ free ( _msg->question );
+ _msg->question = NULL;
+ }
+
+ if ( _msg->answer_count > 0 && _msg->answer) {
+ free ( _msg->answer );
+ _msg->answer = NULL;
+ }
+
+ return 0;
+}
+
int dns_parse_packet ( char* _buffer, int _bufflen, struct dns_message* _msg )
{
+ //TODO refactor
+
if ( !_buffer || !_bufflen || !_msg )
return 1; //Invalid input
@@ -23,16 +67,25 @@ int dns_parse_packet ( char* _buffer, int _bufflen, struct dns_message* _msg )
_msg->header.RA = (0x80 & *( (uint8_t*) (_buffer + 3))) >> 7;
_msg->header.Z = (0x70 & *( (uint8_t*) (_buffer + 3))) >> 4;
_msg->header.RCODE = (0x0F & *( (uint8_t*) (_buffer + 3)));
- _msg->header.question_count = (*((uint8_t*) (_buffer + 4 )) << 8) | *((uint8_t*) (_buffer + 5 ));
- _msg->header.answer_count = (*((uint8_t*) (_buffer + 6 )) << 8) | *((uint8_t*) (_buffer + 7 ));
+ _msg->question_count = _msg->header.question_count = (*((uint8_t*) (_buffer + 4 )) << 8) | *((uint8_t*) (_buffer + 5 ));
+ _msg->answer_count = _msg->header.answer_count = (*((uint8_t*) (_buffer + 6 )) << 8) | *((uint8_t*) (_buffer + 7 ));
_msg->header.authorative_count = (*((uint8_t*) (_buffer + 8 )) << 8) | *((uint8_t*) (_buffer + 9 ));
_msg->header.additional_count = (*((uint8_t*) (_buffer + 10)) << 8) | *((uint8_t*) (_buffer + 11));
+
//TODO remove
printf("ANSWER %i\n", _msg->header.answer_count);
printf("QUESTI %i\n", _msg->header.question_count);
printf("AUTHOR %i\n", _msg->header.authorative_count);
printf("ADDITI %i\n", _msg->header.additional_count);
+ //Check for sensible QD, AN, NS and ARCOUNTS before massive memory allocation
+ if( _msg->header.question_count > 4 ||
+ _msg->header.answer_count > 32 ||
+ _msg->header.authorative_count > 32 ||
+ _msg->header.additional_count > 32 ) {
+ return 1;
+ }
+
//Allocate question array
//TODO Only implements question section.
size_t qsize = sizeof(typeof(*(_msg->question))) * _msg->question_count;
@@ -40,6 +93,9 @@ int dns_parse_packet ( char* _buffer, int _bufflen, struct dns_message* _msg )
_msg->question = malloc ( qsize );
memset( _msg->question, 0, qsize );
+ if (!_msg->question) //malloc failed
+ return 1;
+
int ptr = 12; //byte counter
for (int i = 0; i < _msg->question_count; i++) {
int qname_len = qname_check ( (_buffer + ptr), _bufflen - ptr);
@@ -49,12 +105,15 @@ int dns_parse_packet ( char* _buffer, int _bufflen, struct dns_message* _msg )
_msg->question[i].qname = _buffer + ptr;
ptr += qname_len;
- _msg->question[i].qtype = (uint16_t*) (_buffer + ptr);
- ptr += 2;
- _msg->question[i].qclass = (uint16_t*) (_buffer + ptr);
- if( ptr >= _bufflen ) //Out of bounds check
+ if( ptr >= (_bufflen - 4) ) //Out of bounds check
return 1;
+
+ _msg->question[i].qtype = ((uint8_t)*(_buffer + ptr) << 8) | ((uint8_t)*(_buffer + ptr + 1));
+ ptr += 2;
+ _msg->question[i].qclass = ((uint8_t)*(_buffer + ptr) << 8) | ((uint8_t)*(_buffer + ptr + 1));
+ ptr += 2;
+
}
return 0;
@@ -92,7 +151,6 @@ int fqdn_to_qname( char* _source, int _sourcelen, char* _sink ,int _sinklen )
return i+2;
}
-
int qname_to_fqdn( char* _source, int _sourcelen, char* _sink, int _sinklen )
{
if ( !_sourcelen || !_sinklen ) {
diff --git a/src/dns.h b/src/dns.h
index f93480e..fe871e0 100644
--- a/src/dns.h
+++ b/src/dns.h
@@ -12,18 +12,49 @@
//TODO remove
#include <stdio.h>
+//Resource Records
+#define RR_A 1
+#define RR_NS 2
+#define RR_CNAME 5
+#define RR_SOA 6
+#define RR_MX 15
+#define RR_TXT 16
+#define RR_AAAA 28
+#define RR_SRV 33
+
+//Record Classes
+#define CL_IN 1 //Internet
+#define CL_CS 2 //CSNET (Onsolete)
+#define CL_CH 3 //CHAOS
+#define CL_HS 4 //Hesiod
+
+//OPCODES
+#define OP_Q 0 //Query
+#define OP_IQ 1 //Inverse Query
+#define OP_STAT 2 //Status request
+
+//Responsecode
+#define RCODE_NOERR 0
+#define RCODE_FORMAT 1
+#define RCODE_SERVFAIL 2
+#define RCODE_NAMEERR 3
+#define RCODE_NI 4 //Not implemented
+#define RCODE_REFUSED 5
+
+#define FLIP_BYTES(u) (((0x00FF & u) << 8) | ((0xFF00 & u) >> 8))
+
/**
* Data is COPIED
* */
struct dns_header;
/**
- * Data is REFERENCED
+ * QNAME is REFERENCED
* */
struct dns_question;
/**
- * Data is REFERENCED
+ * NAME is REFERENCED
* */
struct dns_answer;
@@ -55,16 +86,16 @@ struct dns_header {
struct dns_question {
const char* qname;
- const uint16_t* qtype;
- uint16_t* qclass;
+ uint16_t qtype;
+ uint16_t qclass;
};
struct dns_answer {
char* name; //in qname format
- uint16_t* type;
- uint16_t* class;
- uint32_t* ttl;
- uint16_t* rdlength;
+ uint16_t type;
+ uint16_t class;
+ uint32_t ttl;
+ uint16_t rdlength;
char* rdata;
};
@@ -78,10 +109,24 @@ struct dns_message {
struct dns_answer* answer;
};
+int dns_construct_header (
+ struct dns_header* _header,
+ char* _buffer,
+ int _bufflen
+ );
+
+/**
+ * Frees all malloced memory
+ * */
+int dns_destroy_struct ( struct dns_message* _msg );
+
/**
* Parse the packet in _buffer and populate the dns_message struct
* Struct may still be written to on failure but contents are invalid
* returns: 0 on success, !=0 on failure
+ *
+ * ONLY WRITES QUESTION SECTION. ALL OTHER ARE IGNORED
+ *
* */
int dns_parse_packet ( char* _buffer, int _bufflen, struct dns_message* _msg );
diff --git a/src/main.c b/src/main.c
index 1e96f33..75574a0 100644
--- a/src/main.c
+++ b/src/main.c
@@ -158,17 +158,11 @@ int main( int argc,
LOGPRINTF(_LOG_DEBUG, "UDP Packet size %i", ret);
- if ( (handle_connection (sock_server,
- &sock_client_addr,
- sock_client_addr_len,
- recv_buffer,
- ret ) ) ) {
- LOGPRINTF(_LOG_ERROR, "handle_connection() failed");
- return errno;
- }
- else {
- LOGPRINTF ( _LOG_DEBUG, "forked " );
- }
+ handle_connection ( sock_server,
+ &sock_client_addr,
+ sock_client_addr_len,
+ recv_buffer,
+ ret );
}
close( sock_server );
@@ -182,35 +176,28 @@ int handle_connection ( int _socket,
char* _buffer,
int _bufflen )
{
- pid_t pid = fork();
-
- if ( pid > 0)
- return 0;
- else if ( pid < 0 )
- return errno;
-
- //Change signal handler. signal_term shuts down entire socket on TERM
- signal ( SIGTERM, signal_term_child );
-
- //echo request
- sendto (_socket, _buffer, _bufflen, 0, (struct sockaddr*) sockaddr_client, sockaddr_client_len);
-
- //Testing recieved question
- //TODO remove
-
struct dns_message msg;
if (dns_parse_packet (_buffer, _bufflen, &msg) ) {
LOGPRINTF (_LOG_DEBUG, "Malformed packet recieved. parsing failed");
- close ( _socket );
- exit( 1 );
+ return 1;
}
- char out[128];
- qname_to_fqdn( msg.question[0].qname, 100, out, 128);
- printf("%s\n", out);
+ if(msg.question_count > 0) {
+ char out[128];
+ qname_to_fqdn( msg.question[0].qname, 100, out, 128);
+ printf("%s %i\n", out, msg.question[0].qtype);
+ }
+
+ dns_destroy_struct ( &msg );
+
+ //Always return NXDOMAIN
+ struct dns_header head = {msg.header.id,1,OP_Q,0,0,0,0,0,RCODE_NAMEERR,0,0,0,0};
+ char ret[20];
+ int retlen = dns_construct_header ( &head, ret, 20 );
+ sendto (_socket, ret, retlen, 0, (struct sockaddr*) sockaddr_client, sockaddr_client_len);
- exit ( 0 );
+ return 0;
}
void signal_term ( ) {
generated by cgit v1.2.3 (git 2.39.1) at 2024-11-22 05:35:44 +0000