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| dns.c | ●●●●● patch | view | raw | blame | history | |
| dns.h | ●●●●● patch | view | raw | blame | history | |
| main.c | ●●●●● patch | view | raw | blame | history |
Makefile
New file @@ -0,0 +1,12 @@ CC=gcc OBJ=main.o dns.o DEPS=dns.h CFLAGS=-g default: all %.o: %.c $(DEPS) $(CC) $(CFLAGS) -c -o $@ $< all: $(OBJ) $(CC) $(CFLAGS) $^ dns.c
New file @@ -0,0 +1,269 @@ #include <stdio.h> #include <stdlib.h> #include <string.h> #include <sys/socket.h> #include <arpa/inet.h> //#include <netint/in.h> //#include <netdb.h> #include <sys/time.h> #include <unistd.h> #include "dns.h" // DNS code copied from // https://gist.github.com/fffaraz/9d9170b57791c28ccda9255b48315168 /* DNS header struct */ struct DNS_HEADER { unsigned short id; //ID number unsigned char rd :1; //recursion unsigned char tc :1; //truncated message unsigned char aa :1; //authoritive answer unsigned char opcode :4; //message purpose unsigned char qr :1; //query response unsigned char rcode :4; //response code unsigned char cd :1; //checking disabled 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 ans_count; //number of answer entries unsigned short auth_count; //number of authority entries unsigned short add_count; //number of resource entries }; /* structured for query structure */ struct QUESTION { unsigned short qtype; unsigned short qclass; }; /* Query structure */ struct QUERY { unsigned char* name; struct QUESTION* ques; }; /* Constant sized fields of record structure */ #pragma pack(push, 1) struct R_DATA { unsigned short type; unsigned short _class; unsigned int ttl; unsigned short data_len; }; #pragma pack(pop) /* Pointers to record components */ struct RES_RECORD { unsigned char* name; struct R_DATA* resource; unsigned char* rdata; }; void resolve(char* hostname, char* dns_ip, int query_type, int read) { int s, i, j; struct sockaddr_in dest, a; unsigned char buf[65536], *qname, *reader; struct DNS_HEADER* dns = NULL; struct QUESTION* qinfo = NULL; s = socket(AF_INET, SOCK_DGRAM, IPPROTO_UDP); 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 dns->aa = 0; //not authoritive dns->tc = 0; //not trucated dns->rd = 1; //want recursion dns->ra = 0; //recursion not available dns->z = 0; dns->ad = 0; dns->cd = 0; dns->rcode = 0; dns->q_count = htons(1); //one question dns->ans_count = 0; dns->auth_count = 0; dns->add_count = 0; //dns packet query qname = (unsigned char*)&buf[sizeof(struct DNS_HEADER)]; change_to_DNS_name_format(qname, (unsigned char*)hostname); qinfo = (struct QUESTION*)&buf[sizeof(struct DNS_HEADER) + strlen((const char*)qname) + 1]; qinfo->qtype = htons(query_type); //type of query from argument (A,AAAA,MX,CNAME,NS,...) qinfo->qclass = htons(1); //internet class //send request // return less than 0 is a fail 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); //read response if (read) { print_packet(buf); } return; } 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; 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; 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; 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++) { answers[i].rdata[j] = reader[j]; } 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; 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; 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++) addit[i].rdata[j] = reader[j]; 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 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 printf("has alias: %s", 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) { long* p; p = (long*)addit[i].rdata; a.sin_addr.s_addr = *p; printf("has IPv4 address: %s", inet_ntoa(a.sin_addr)); } putc('\n', stdout); } } void change_to_DNS_name_format(unsigned char* dns, unsigned char* host) { int lock = 0; char h[300]; strcpy(h, host); strcat((char*)h,"."); for (int i = 0; i < strlen((char*)h); i++) { if (h[i] == '.') { *dns++ = i-lock; for (;lock<i;lock++) { *dns++ = h[lock]; } lock++; } } *dns++ = '\0'; } char* read_name(unsigned char* reader, unsigned char* buffer, int* count) { unsigned char* name; unsigned int p=0, jumped=0, offset; int i, j; *count = 1; name = (unsigned char*)malloc(256); name[0]='\0'; while (*reader != 0) { if (*reader >= 192) { offset = (*reader)*256+ *(reader+1) - 49152; reader = buffer+offset-1; jumped=1; } else { name[p++]=*reader; } reader = reader+1; if (jumped == 0) { *count = *count+1; } } name[p] = '\0'; if (jumped == 1) { *count = *count + 1; } //convert from dns format to normal for (i = 0; i < strlen((const char*)name); i++) { p = name[i]; for (j = 0; j < p; j++) { name[i] = name[i+1]; i++; } name[i] = '.'; } name[i-1] = '\0'; return name; } dns.h
New file @@ -0,0 +1,12 @@ // DNS resource records #define T_A 1 // IPv4 address #define T_NS // Name Server #define T_CNAME 5 // Cannonical name #define T_SOA 6 // State of Authority #define T_PTR 12 // Domain name pointer #define T_MX 15 // Mail exchange void resolve(char* hostname, char* dns_ip, int query_type, int read); void print_packet(unsigned char* buf); void change_to_DNS_name_format(unsigned char* dns, unsigned char* host); char* read_name(unsigned char* reader, unsigned char* buffer, int* count); main.c
@@ -1,278 +1,7 @@ #include <stdio.h> #include <stdlib.h> #include <string.h> #include <sys/socket.h> #include <arpa/inet.h> //#include <netint/in.h> //#include <netdb.h> #include <sys/time.h> #include <unistd.h> // DNS code copied from // https://gist.github.com/fffaraz/9d9170b57791c28ccda9255b48315168 // DNS resource records #define T_A 1 // IPv4 address #define T_NS // Name Server #define T_CNAME 5 // Cannonical name #define T_SOA 6 // State of Authority #define T_PTR 12 // Domain name pointer #define T_MX 15 // Mail exchange /* DNS header struct */ struct DNS_HEADER { unsigned short id; //ID number unsigned char rd :1; //recursion unsigned char tc :1; //truncated message unsigned char aa :1; //authoritive answer unsigned char opcode :4; //message purpose unsigned char qr :1; //query response unsigned char rcode :4; //response code unsigned char cd :1; //checking disabled 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 ans_count; //number of answer entries unsigned short auth_count; //number of authority entries unsigned short add_count; //number of resource entries }; /* structured for query structure */ struct QUESTION { unsigned short qtype; unsigned short qclass; }; /* Query structure */ struct QUERY { unsigned char* name; struct QUESTION* ques; }; /* Constant sized fields of record structure */ #pragma pack(push, 1) struct R_DATA { unsigned short type; unsigned short _class; unsigned int ttl; unsigned short data_len; }; #pragma pack(pop) /* Pointers to record components */ struct RES_RECORD { unsigned char* name; struct R_DATA* resource; unsigned char* rdata; }; void resolve(char* hostname, char* dns_ip, int query_type, int read); void change_to_DNS_name_format(unsigned char* dns, unsigned char* host); u_char* read_name(unsigned char* reader, unsigned char* buffer, int* count); #include "dns.h" int main(int argc, char** argv) { resolve("google.com", "1.1.1.1", T_A, 1); return 0; } void resolve(char* hostname, char* dns_ip, int query_type, int read) { int s, i, j; struct sockaddr_in dest, a; unsigned char buf[65536], *qname, *reader; struct DNS_HEADER* dns = NULL; struct QUESTION* qinfo = NULL; s = socket(AF_INET, SOCK_DGRAM, IPPROTO_UDP); 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 dns->aa = 0; //not authoritive dns->tc = 0; //not trucated dns->rd = 1; //want recursion dns->ra = 0; //recursion not available dns->z = 0; dns->ad = 0; dns->cd = 0; dns->rcode = 0; dns->q_count = htons(1); //one question dns->ans_count = 0; dns->auth_count = 0; dns->add_count = 0; //dns packet query qname = (unsigned char*)&buf[sizeof(struct DNS_HEADER)]; change_to_DNS_name_format(qname, (unsigned char*)hostname); qinfo = (struct QUESTION*)&buf[sizeof(struct DNS_HEADER) + strlen((const char*)qname) + 1]; qinfo->qtype = htons(query_type); //type of query from argument (A,AAAA,MX,CNAME,NS,...) qinfo->qclass = htons(1); //internet class //send request // return less than 0 is a fail 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); //read response if (read) { struct RES_RECORD answers[20], auth[20], addit[20]; int stop; 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; 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; 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++) { answers[i].rdata[j] = reader[j]; } 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; 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; 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++) addit[i].rdata[j] = reader[j]; 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 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 printf("has alias: %s", 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) { long* p; p = (long*)addit[i].rdata; a.sin_addr.s_addr = *p; printf("has IPv4 address: %s", inet_ntoa(a.sin_addr)); } putc('\n', stdout); } } return; } void change_to_DNS_name_format(unsigned char* dns, unsigned char* host) { int lock = 0; char h[300]; strcpy(h, host); strcat((char*)h,"."); for (int i = 0; i < strlen((char*)h); i++) { if (h[i] == '.') { *dns++ = i-lock; for (;lock<i;lock++) { *dns++ = h[lock]; } lock++; } } *dns++ = '\0'; } u_char* read_name(unsigned char* reader, unsigned char* buffer, int* count) { unsigned char* name; unsigned int p=0, jumped=0, offset; int i, j; *count = 1; name = (unsigned char*)malloc(256); name[0]='\0'; while (*reader != 0) { if (*reader >= 192) { offset = (*reader)*256+ *(reader+1) - 49152; reader = buffer+offset-1; jumped=1; } else { name[p++]=*reader; } reader = reader+1; if (jumped == 0) { *count = *count+1; } } name[p] = '\0'; if (jumped == 1) { *count = *count + 1; } //convert from dns format to normal for (i = 0; i < strlen((const char*)name); i++) { p = name[i]; for (j = 0; j < p; j++) { name[i] = name[i+1]; i++; } name[i] = '.'; } name[i-1] = '\0'; return name; }
