From d2c641eb5b516783adfe2a236bc18412cd89af71 Mon Sep 17 00:00:00 2001 From: Jonas Gunz Date: Sat, 30 Nov 2019 16:05:41 +0100 Subject: asdf --- src/dns.c | 31 +++++++++++++++++++++ src/dns.h | 63 ++++++++++++++++++++++++++++++++++++++++++ src/main.c | 92 ++++++++++++++++++++++++++++++++++---------------------------- 3 files changed, 145 insertions(+), 41 deletions(-) (limited to 'src') diff --git a/src/dns.c b/src/dns.c index 7c94c8a..2d3ac75 100644 --- a/src/dns.c +++ b/src/dns.c @@ -1,5 +1,36 @@ #include "dns.h" +int dns_parse_packet ( char* _buffer, int _bufflen, struct dns_message* _msg ) +{ + if ( !_buffer || !_bufflen || !_msg ) + return 1; //Invalid input + + if ( _bufflen < 12 ) + return 1; //Too short to contain a DNS header + + //TODO test + _msg->header.id = *( (uint16_t*) _buffer ); + _msg->header.QR = ( 0x80 & *( (uint8_t*) (_buffer + 2)) ) >> 7; + _msg->header.OPCODE = (0x78 & *( (uint8_t*) (_buffer + 2))) >> 3; + _msg->header.AA = (0x04 & *( (uint8_t*) (_buffer + 2))) >> 2; + _msg->header.TC = (0x02 & *( (uint8_t*) (_buffer + 2))) >> 1; + _msg->header.RD = (0x01 & *( (uint8_t*) (_buffer + 2))); + _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->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)); + + 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); + + return 1; +} + int fqdn_to_qname( char* _source, int _sourcelen, char* _sink ,int _sinklen ) { int i; diff --git a/src/dns.h b/src/dns.h index 5d8096e..8cba804 100644 --- a/src/dns.h +++ b/src/dns.h @@ -2,6 +2,69 @@ #include +//TODO remove +#include + +struct dns_header; + +struct dns_question; + +struct dns_answer; + +/** + * DNS Message struct + * */ +struct dns_message; + +struct dns_header { + uint16_t id; + + uint8_t QR; //Query:0 Reply:1 + uint8_t OPCODE; //Query:0 Iquery:1 Status:2 + uint8_t AA; //Authorative answer + uint8_t TC; //Truncation + uint8_t RD; //Recursion Desired + uint8_t RA; //Recursion Available + uint8_t Z; //Unused + uint8_t RCODE; //Response Code + + uint16_t question_count; + uint16_t answer_count; + uint16_t authorative_count; + uint16_t additional_count; +}; + +struct dns_question { + char* qname; + 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; + char* rdata; +}; + +struct dns_message { + struct dns_header header; + + int qcount; + struct dns_question* question; + + int acount; + struct dns_answer* answer; +}; + +/** + * Parse the packet in _buffer and populate the dns_message struct + * returns: 0 on success, !=0 on failure + * */ +int dns_parse_packet ( char* _buffer, int _bufflen, struct dns_message* _msg ); + /** * Convert a null terminated string containing a * fqdn (eg server.example.com) to the binary format used by DNS records diff --git a/src/main.c b/src/main.c index 9d3e214..92ca391 100644 --- a/src/main.c +++ b/src/main.c @@ -19,39 +19,21 @@ #define UDP_BUFFER_LEN 512 -struct dns_message { - //Header - uint16_t id; - - uint8_t QR; //Query:0 Reply:1 - uint8_t OPCODE; //Query:0 Iquery:1 Status:2 - uint8_t AA; //Authorative answer - uint8_t TC; //Truncation - uint8_t RD; //Recursion Desired - uint8_t RA; //Recursion Available - uint8_t RCODE; //Response Code - - uint16_t question_count; - uint16_t answer_count; - uint16_t authorative_count; - uint16_t additional_count; - - //Question - //Answer - }; - +//main server socket int sock_server; -int dns_parse_packet ( int _socket, +int handle_connection ( int _socket, struct sockaddr_in *sockaddr_client, socklen_t sockaddr_client_len, - char* buffer, - int bufflen ); + char* _buffer, + int _bufflen ); void signal_term ( ); void signal_term_child ( ); +void signal_child ( ); + int test_main( int argc, char* argv[] ) { @@ -60,7 +42,7 @@ int test_main( int argc, char in[128]; char out[128]; - strncpy ( in, "aaa.aaaaa.aa\0", 127); + strncpy ( in, "sub.domain.example.com\0", 127); printf("%s\n", in); @@ -74,6 +56,15 @@ int test_main( int argc, for(int i = 0; i < written; i++) printf(" %x ", out[i]); + written = qname_to_fqdn (out,128,in,128); + + if (written < 0) { + printf("invalid qname\n"); + return 1; + } + + printf("%s\n", in); + printf("\n\n"); return 0; } @@ -89,11 +80,14 @@ int main( int argc, signal ( SIGTERM, signal_term ); signal ( SIGINT, signal_term ); + //Avoid zombie processes + signal (SIGCHLD, SIG_IGN); + log_init_stdout ( _LOG_DEBUG ); sock_server = socket ( AF_INET, SOCK_DGRAM, 0 ); if ( sock_server == -1 ) { - PRINT_ERRNO(); + LOGPRINTF(_LOG_ERROR, "socket() failed"); return errno; } @@ -102,7 +96,7 @@ int main( int argc, sock_server_addr.sin_port = htons( 53 ); ret = inet_aton ( "0.0.0.0", & sock_server_addr.sin_addr ); if( ret == 0 ) { //Error on 0, no errno! - LOGPRINTF(_LOG_NOTE, "inet_aton(): Invalid IP\n" ); + LOGPRINTF(_LOG_NOTE, "inet_aton(): Invalid bind IP\n" ); return 1; } @@ -110,7 +104,7 @@ int main( int argc, (struct sockaddr*) &sock_server_addr, sizeof(struct sockaddr_in) ); if ( ret == -1 ) { - PRINT_ERRNO(); + LOGPRINTF(_LOG_ERROR, "bind() failed"); return errno; } @@ -118,6 +112,7 @@ int main( int argc, { struct sockaddr_in sock_client_addr; socklen_t sock_client_addr_len; + pid_t pid; sock_client_addr_len = sizeof ( struct sockaddr_in ); memset ( &sock_client_addr, '\0', sock_client_addr_len ); @@ -133,18 +128,18 @@ int main( int argc, return errno; } - LOGPRINTF(_LOG_NOTE, "Connection"); + LOGPRINTF(_LOG_DEBUG, "UDP Packet size %i", ret); - if ( dns_parse_packet ( sock_server, + if ( (pid = handle_connection (sock_server, &sock_client_addr, sock_client_addr_len, recv_buffer, - ret ) ) { - LOGPRINTF(_LOG_ERROR, "dns_parse_packet()"); + ret ) ) ) { + LOGPRINTF(_LOG_ERROR, "handle_connection() failed"); return errno; } else { - LOGPRINTF ( _LOG_DEBUG, "forked\n" ); + LOGPRINTF ( _LOG_DEBUG, "forked " ); } } @@ -153,11 +148,11 @@ int main( int argc, return 0; } -int dns_parse_packet ( int _socket, +int handle_connection ( int _socket, struct sockaddr_in *sockaddr_client, socklen_t sockaddr_client_len, - char* buffer, - int bufflen ) + char* _buffer, + int _bufflen ) { pid_t pid = fork(); @@ -165,13 +160,27 @@ int dns_parse_packet ( int _socket, return 0; else if ( pid < 0 ) return errno; + + //Change signal handler. signal_term shuts down entire socket on TERM + signal ( SIGTERM, signal_term_child ); - signal ( SIGTERM, signal_term_child); + //echo request + sendto (_socket, _buffer, _bufflen, 0, (struct sockaddr*) sockaddr_client, sockaddr_client_len); - struct dns_message msg; + //Testing recieved question + //TODO remove + char out[128]; + qname_to_fqdn((_buffer+12), _bufflen-12, out, 128); + printf("%s\n", out); - msg.id = *( (uint16_t*) buffer ); - msg.QR = 0x80 & *( (uint8_t*) (buffer + 2)); + + struct dns_message msg; + + if (dns_parse_packet (_buffer, _bufflen, &msg) ) { + LOGPRINTF (_LOG_DEBUG, "Malformed packet recieved. parsing failed"); + close ( _socket ); + exit( 1 ); + } exit ( 0 ); } @@ -179,7 +188,8 @@ int dns_parse_packet ( int _socket, void signal_term ( ) { printf( "Recieved Signal. Terminating active connections and closing socket\n" ); - kill ( 0, SIGTERM ); //terminate all child processes + //terminate all children >:) + kill ( 0, SIGTERM ); shutdown ( sock_server, SHUT_RDWR ); close ( sock_server ); -- cgit v1.2.3