From d3f3ee16d8adaef681afed67f236e3bb14e7cdc0 Mon Sep 17 00:00:00 2001
From: Joel Grunbaum <joelgrun@gmail.com>
Date: Wed, 21 Oct 2020 13:05:26 +0000
Subject: [PATCH] change artifact name and added penalty for failed connections
---
dns.c | 134 +++++++++++++++++++++++++++++---------------
1 files changed, 87 insertions(+), 47 deletions(-)
diff --git a/dns.c b/dns.c
index af08c44..ad58873 100644
--- a/dns.c
+++ b/dns.c
@@ -5,10 +5,14 @@
#include <arpa/inet.h>
//#include <netint/in.h>
//#include <netdb.h>
-#include <sys/time.h>
+//#include <sys/time.h>
+#include <time.h>
#include <unistd.h>
#include "dns.h"
+void change_to_DNS_name_format(unsigned char* dns, unsigned char* host);
+char* read_name(unsigned char* reader, unsigned char* buffer, int* count);
+
// DNS code copied from
// https://gist.github.com/fffaraz/9d9170b57791c28ccda9255b48315168
@@ -26,7 +30,7 @@
unsigned char ad :1; //authenticated data
unsigned char z :1; //reserved for future use
unsigned char ra :1; //recursion available
- unsigned short q_count; //number of question entries
+ unsigned short q_count; //number of question entrise
unsigned short ans_count; //number of answer entries
unsigned short auth_count; //number of authority entries
unsigned short add_count; //number of resource entries
@@ -60,26 +64,30 @@
/* Pointers to record components */
struct RES_RECORD
{
- unsigned char* name;
- struct R_DATA* resource;
- unsigned char* rdata;
+ char* name;
+ struct R_DATA resource;
+ char* rdata;
};
-void resolve(char* hostname, char* dns_ip, int query_type, int read)
+// Test server dns_ip as IPv4 string for hostname
+// Writes received packet to buf, which is supplied and returns time for request
+struct timespec resolve(unsigned char* buf, char* hostname, char* dns_ip, int query_type)
{
- int s, i, j;
- struct sockaddr_in dest, a;
- unsigned char buf[65536], *qname, *reader;
- struct DNS_HEADER* dns = NULL;
- struct QUESTION* qinfo = NULL;
+ int s, i;
+ struct sockaddr_in dest;
+ unsigned char *qname;
+ struct DNS_HEADER* dns = (struct DNS_HEADER*)buf;
+ struct QUESTION* qinfo;
+ struct timespec start, end, total, timeout;
+ timeout.tv_nsec=0; timeout.tv_sec=1;
s = socket(AF_INET, SOCK_DGRAM, IPPROTO_UDP);
+ setsockopt(s, SOL_SOCKET, SO_RCVTIMEO, &timeout, sizeof(struct timespec)); //use a 1 second timeout for receiving, should be more than enough and anything more is really bad
dest.sin_family = AF_INET;
dest.sin_port = htons(53);
dest.sin_addr.s_addr = inet_addr(dns_ip);
//dns packet header
- dns = (struct DNS_HEADER*)&buf;
dns->id = (unsigned short) htons(getpid());
dns->qr = 0; //make query
dns->opcode = 0; //standard query
@@ -105,118 +113,149 @@
//send request
// return less than 0 is a fail
+ clock_gettime(CLOCK_MONOTONIC, &start);
sendto(s,(char*)buf, sizeof(struct DNS_HEADER)+strlen((const char*)qname)+1+sizeof(struct QUESTION), 0, (struct sockaddr*)&dest, sizeof(dest));
//receive response
//negative return is a fail
i = sizeof(dest);
- recvfrom(s, (char*)buf, 65536, 0, (struct sockaddr*)&dest, (socklen_t*)&i);
+ i = recvfrom(s, (char*)buf, 65536, 0, (struct sockaddr*)&dest, (socklen_t*)&i);
+ clock_gettime(CLOCK_MONOTONIC, &end);
- //read response
- if (read) {
- print_packet(buf);
- }
- return;
+ // Make sure packet was returned
+ if (i == -1)
+ total.tv_nsec = -1;
+ else
+ total.tv_sec = end.tv_sec - start.tv_sec;
+ if ((end.tv_nsec - start.tv_nsec) < 0)
+ total.tv_nsec = start.tv_nsec - end.tv_nsec;
+ else
+ total.tv_nsec = end.tv_nsec - start.tv_nsec;
+ close(s);
+ return total;
}
+// Print dns packet content, not terribly reliable but works for testing resolve with A requests
void print_packet(unsigned char* buf)
{
struct RES_RECORD answers[20], auth[20], addit[20];
struct DNS_HEADER *dns;
struct sockaddr_in a;
- char* qname = buf+sizeof(struct DNS_HEADER), *reader;
+ unsigned char* qname = buf+sizeof(struct DNS_HEADER), *reader;
int stop, i, j;
dns = (struct DNS_HEADER*)buf;
reader = &buf[sizeof(struct DNS_HEADER)+strlen((const char*)qname)+1+sizeof(struct QUESTION)];
printf("Response contains %d Qs, %d ans, %d auth serv, %d add reconds\n", ntohs(dns->q_count), ntohs(dns->ans_count), ntohs(dns->auth_count), ntohs(dns->add_count));
stop = 0;
+
+ //read answers
for (i = 0; i < ntohs(dns->ans_count); i++) {
answers[i].name = read_name(reader, buf, &stop);
reader = reader + stop;
- answers[i].resource = (struct R_DATA*)reader;
+ memcpy(&(answers[i].resource), reader, sizeof(struct R_DATA));
reader = reader+sizeof(struct R_DATA);
-
- if (ntohs(answers[i].resource->type) == T_A) { //IPv4 address
- answers[i].rdata = (unsigned char*)malloc(ntohs(answers[i].resource->data_len));
- for (j = 0; j < ntohs(answers[i].resource->data_len); j++) {
+
+ if (ntohs(answers[i].resource.type) == T_A) { //IPv4 address
+ answers[i].rdata = (char*)malloc(ntohs(answers[i].resource.data_len));
+ for (j = 0; j < ntohs(answers[i].resource.data_len); j++) {
answers[i].rdata[j] = reader[j];
}
- answers[i].rdata[ntohs(answers[i].resource->data_len)] = '\0';
- reader = reader + ntohs(answers[i].resource->data_len);
+ answers[i].rdata[ntohs(answers[i].resource.data_len)] = '\0';
+ reader = reader + ntohs(answers[i].resource.data_len);
} else {
answers[i].rdata = read_name(reader, buf, &stop);
reader = reader + stop;
}
}
-
+
//read authorities
for (i = 0; i < ntohs(dns->auth_count); i++) {
auth[i].name = read_name(reader, buf, &stop);
reader += stop;
- auth[i].resource = (struct R_DATA*)reader;
+ memcpy(&(auth[i].resource), reader, sizeof(struct R_DATA));
reader += sizeof(struct R_DATA);
auth[i].rdata = read_name(reader, buf, &stop);
reader += stop;
}
-
+
//read additional
for (i = 0; i < ntohs(dns->add_count); i++) {
addit[i].name = read_name(reader, buf, &stop);
reader += stop;
- addit[i].resource = (struct R_DATA*)reader;
+ memcpy(&(addit[i].resource), reader, sizeof(struct R_DATA));
reader += sizeof(struct R_DATA);
- if (ntohs(addit[i].resource->type) == 1) {
- addit[i].rdata = malloc(ntohs(addit[i].resource->data_len));
- for (j = 0; j < ntohs(addit[i].resource->data_len); j++)
+ if (ntohs(addit[i].resource.type) == 1) {
+ addit[i].rdata = malloc(ntohs(addit[i].resource.data_len));
+ for (j = 0; j < ntohs(addit[i].resource.data_len); j++)
addit[i].rdata[j] = reader[j];
-
- addit[i].rdata[ntohs(addit[i].resource->data_len)] = '\0';
- reader += ntohs(addit[i].resource->data_len);
+ addit[i].rdata[ntohs(addit[i].resource.data_len)] = '\0';
+ reader += ntohs(addit[i].resource.data_len);
} else {
addit[i].rdata = read_name(reader, buf, &stop);
reader += stop;
}
}
-
+
//print answers
printf("ans recs: %d\n", ntohs(dns->ans_count));
for (i = 0; i < ntohs(dns->ans_count); i++) {
printf("name: %s ", answers[i].name);
- if (ntohs(answers[i].resource->type) == T_A) { //IPv4
+ if (ntohs(answers[i].resource.type) == T_A) { //IPv4
long* p;
p = (long*)answers[i].rdata;
a.sin_addr.s_addr=(*p);
printf("has IPv4 addresss: %s", inet_ntoa(a.sin_addr));
- } else if (ntohs(answers[i].resource->type) == T_CNAME) { //CNAME
+ } else if (ntohs(answers[i].resource.type) == T_CNAME) { //CNAME
printf("has alias: %s", answers[i].rdata);
}
+ free(answers[i].name);
+ free(answers[i].rdata);
putc('\n', stdout);
}
//print authorities
printf("Auth recs: %d\n", ntohs(dns->auth_count));
for (i = 0; i < ntohs(dns->auth_count); i++) {
- printf("name: %s ", addit[i].name);
- if (ntohs(addit[i].resource->type) == 1) {
+ printf("name: %s ", auth[i].name);
+ if (ntohs(auth[i].resource.type) == 1) {
long* p;
- p = (long*)addit[i].rdata;
+ p = (long*)auth[i].rdata;
a.sin_addr.s_addr = *p;
printf("has IPv4 address: %s", inet_ntoa(a.sin_addr));
}
+ free(answers[i].name);
+ free(auth[i].rdata);
+ putc('\n', stdout);
+ }
+
+ printf("Addit recs: %d\n", ntohs(dns->add_count));
+ for (i = 0; i < ntohs(dns->add_count); i++) {
+ printf("name; %s", addit[i].name);
+ if (ntohs(auth[i].resource.type) == 1) {
+ long *p;
+ p = (long*)addit[i].rdata;
+ a.sin_addr.s_addr = *p;
+ printf("has IPv4 address: %s", inet_ntoa(a.sin_addr));
+ } else {
+ printf("has %s", addit[i].rdata);
+ }
+ free(answers[i].name);
+ free(addit[i].rdata);
putc('\n', stdout);
}
}
-
+// convert from dot format to dns format
+// eg google.com to 6google3com
void change_to_DNS_name_format(unsigned char* dns, unsigned char* host)
{
int lock = 0;
char h[300];
- strcpy(h, host);
+ strcpy(h, (char*)host);
strcat((char*)h,".");
- for (int i = 0; i < strlen((char*)h); i++) {
+ for (int i = 0; i < strlen(h); i++) {
if (h[i] == '.') {
*dns++ = i-lock;
for (;lock<i;lock++) {
@@ -228,13 +267,14 @@
*dns++ = '\0';
}
+// Convert from dns to dot format
char* read_name(unsigned char* reader, unsigned char* buffer, int* count)
{
- unsigned char* name;
+ char* name;
unsigned int p=0, jumped=0, offset;
int i, j;
*count = 1;
- name = (unsigned char*)malloc(256);
+ name = (char*)malloc(256);
name[0]='\0';
while (*reader != 0) {
--
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