mirror of https://github.com/oxen-io/lokinet
dns client and server
Ryan Tharp
6 years ago
parent
0750befddc
commit
e5c1caf5b3
@ -0,0 +1,440 @@
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#include <signal.h>
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#include <getopt.h>
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#include <stdio.h> /* fprintf, printf */
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#include <sys/types.h>
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#include <sys/socket.h>
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#include <netdb.h> /* getaddrinfo, getnameinfo */
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#include <stdlib.h> /* exit */
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#include <string.h> /* memset */
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#include <netinet/in.h>
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#include <arpa/inet.h>
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#include <string>
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#include "net.hpp"
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#include "logger.hpp"
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bool done = false;
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void
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handle_signal(int sig)
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{
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printf("got SIGINT\n");
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done = true;
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}
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#define BUF_SIZE 512
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struct query {
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uint16_t length;
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char * url;
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unsigned char request[BUF_SIZE];
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uint16_t reqType;
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};
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#define SERVER "8.8.8.8"
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#define PORT 53
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struct sockaddr *resolveHost(char *url) {
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struct query dnsQuery;
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dnsQuery.length = 12;
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dnsQuery.url = url;
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dnsQuery.reqType = 0x01;
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// dnsQuery.request = { 0xDB, 0x42, 0x01, 0x00, 0x00, 0x01, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00 };
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dnsQuery.request[ 0] = 0xDB;
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dnsQuery.request[ 1] = 0x42;
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dnsQuery.request[ 2] = 0x01;
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dnsQuery.request[ 3] = 0x00;
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dnsQuery.request[ 4] = 0x00;
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dnsQuery.request[ 5] = 0x01;
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dnsQuery.request[ 6] = 0x00;
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dnsQuery.request[ 7] = 0x00;
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dnsQuery.request[ 8] = 0x00;
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dnsQuery.request[ 9] = 0x00;
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dnsQuery.request[10] = 0x00;
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dnsQuery.request[11] = 0x00;
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char * word;
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unsigned int i;
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llarp::LogDebug("Asking DNS server %s about %s\n", SERVER, url);
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dnsQuery.url = strdup(url);
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dnsQuery.reqType = 0x01;
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word = strtok(url, ".");
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while (word) {
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llarp::LogDebug("parsing hostname: \"%s\" is %zu characters\n", word, strlen(word));
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dnsQuery.request[dnsQuery.length++] = strlen(word);
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for (i = 0; i < strlen(word); i++) {
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dnsQuery.request[dnsQuery.length++] = word[i];
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}
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word = strtok(NULL, ".");
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}
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dnsQuery.request[dnsQuery.length++] = 0x00; // End of the host name
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dnsQuery.request[dnsQuery.length++] = 0x00; // 0x0001 - Query is a Type A query (host address)
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dnsQuery.request[dnsQuery.length++] = dnsQuery.reqType;
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dnsQuery.request[dnsQuery.length++] = 0x00; // 0x0001 - Query is class IN (Internet address)
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dnsQuery.request[dnsQuery.length++] = 0x01;
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struct sockaddr_in addr;
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//int socket;
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ssize_t ret;
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int rcode;
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socklen_t size;
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int ip = 0;
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int length;
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unsigned char buffer[BUF_SIZE];
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//unsigned char tempBuf[3];
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uint16_t QDCOUNT; //No. of items in Question Section
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uint16_t ANCOUNT; //No. of items in Answer Section
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uint16_t NSCOUNT; //No. of items in Authority Section
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uint16_t ARCOUNT; //No. of items in Additional Section
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uint16_t QCLASS; //Specifies the class of the query
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uint16_t ATYPE; //Specifies the meaning of the data in the RDATA field
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uint16_t ACLASS; //Specifies the class of the data in the RDATA field
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uint32_t TTL; //The number of seconds the results can be cached
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uint16_t RDLENGTH; //The length of the RDATA field
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uint16_t MSGID;
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int sockfd;
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sockfd = socket(AF_INET, SOCK_DGRAM, 0);
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if (sockfd < 0) {
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llarp::LogWarn("Error creating socket!\n");
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return nullptr;
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}
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//socket = sockfd;
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memset(&addr, 0, sizeof(addr));
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addr.sin_family = AF_INET;
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addr.sin_addr.s_addr = inet_addr(SERVER);
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addr.sin_port = htons(PORT);
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size = sizeof(addr);
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//hexdump("sending packet", &dnsQuery.request, dnsQuery.length);
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ret = sendto(sockfd, dnsQuery.request, dnsQuery.length, 0, (struct sockaddr*)&addr, size);
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if (ret < 0) {
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llarp::LogWarn("Error Sending Request");
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return nullptr;
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}
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//printf("Sent\n");
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memset(&buffer, 0, BUF_SIZE);
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ret = recvfrom(sockfd, buffer, BUF_SIZE, 0, (struct sockaddr*)&addr, &size);
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if (ret < 0) {
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llarp::LogWarn("Error Receiving Response");
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return nullptr;
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}
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//hexdump("received packet", &buffer, ret);
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close(sockfd);
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rcode = (buffer[3] & 0x0F);
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//tempBuf[0] = buffer[4];
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//tempBuf[1] = buffer[5];
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//tempBuf[2] = '\0';
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//printf("%0x %0x %0x %0x\n", buffer[4], buffer[5], tempBuf[0], tempBuf[1]);
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//QDCOUNT = (uint16_t) strtol(tempBuf, NULL, 16);
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QDCOUNT = (uint16_t) buffer[4] * 0x100 + buffer[5];
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llarp::LogDebug("entries in question section: %u\n", QDCOUNT);
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ANCOUNT = (uint16_t) buffer[6] * 0x100 + buffer[7];
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llarp::LogDebug("records in answer section: %u\n", ANCOUNT);
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NSCOUNT = (uint16_t) buffer[8] * 0x100 + buffer[9];
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llarp::LogDebug("name server resource record count: %u\n", NSCOUNT);
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ARCOUNT = (uint16_t) buffer[10] * 0x100 + buffer[11];
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llarp::LogDebug("additional records count: %u\n", ARCOUNT);
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llarp::LogDebug("query type: %u\n", dnsQuery.reqType);
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QCLASS = (uint16_t) dnsQuery.request[dnsQuery.length - 2] * 0x100 + dnsQuery.request[dnsQuery.length - 1];
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llarp::LogDebug("query class: %u\n", QCLASS);
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length = dnsQuery.length + 1; // to skip 0xc00c
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ATYPE = (uint16_t) buffer[length + 1] * 0x100 + buffer[length + 2];
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llarp::LogDebug("answer type: %u\n", ATYPE);
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ACLASS = (uint16_t) buffer[length + 3] * 0x100 + buffer[length + 4];
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llarp::LogDebug("answer class: %u\n", ACLASS);
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TTL = (uint32_t) buffer[length + 5] * 0x1000000 + buffer[length + 6] * 0x10000 + buffer[length + 7] * 0x100 + buffer[length + 8];
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llarp::LogDebug("seconds to cache: %u\n", TTL);
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RDLENGTH = (uint16_t) buffer[length + 9] * 0x100 + buffer[length + 10];
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llarp::LogDebug("bytes in answer: %u\n", RDLENGTH);
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MSGID = (uint16_t) buffer[0] * 0x100 + buffer[1];
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llarp::LogDebug("answer msg id: %u\n", MSGID);
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if (rcode == 2) {
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llarp::LogWarn("nameserver %s returned SERVFAIL:\n", SERVER);
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llarp::LogWarn(" the name server was unable to process this query due to a\n problem with the name server.\n");
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return nullptr;
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} else if (rcode == 3) {
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llarp::LogWarn("nameserver %s returned NXDOMAIN for %s:\n", SERVER, dnsQuery.url);
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llarp::LogWarn(" the domain name referenced in the query does not exist\n");
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return nullptr;
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}
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/* search for and print IPv4 addresses */
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if (dnsQuery.reqType == 0x01) {
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llarp::LogDebug("DNS server's answer is: (type#=%u):", ATYPE);
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//printf("IPv4 address(es) for %s:\n", dnsQuery.url);
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for (i = 0 ; i < ret ; i++) {
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if (buffer[i] == 0xC0 && buffer[i+3] == 0x01) {
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ip++; i += 12; /* ! += buf[i+1]; */
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llarp::LogDebug(" %u.%u.%u.%u\n", buffer[i], buffer[i+1], buffer[i+2], buffer[i+3]);
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struct sockaddr *g_addr = new sockaddr;
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g_addr->sa_family = AF_INET;
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g_addr->sa_len = sizeof(in_addr);
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struct in_addr *addr = &((struct sockaddr_in *)g_addr)->sin_addr;
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unsigned char * ip;
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//have ip point to s_addr
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ip = (unsigned char *) &(addr->s_addr);
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ip[0]=buffer[i + 0];
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ip[1]=buffer[i + 1];
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ip[2]=buffer[i + 2];
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ip[3]=buffer[i + 3];
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return g_addr;
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}
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}
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if (!ip) {
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llarp::LogWarn(" No IPv4 address found in the DNS response!\n");
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return nullptr;
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}
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}
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return nullptr;
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}
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int get16bits(const char*& buffer) throw ()
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{
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int value = static_cast<unsigned char> (buffer[0]);
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value = value << 8;
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value += static_cast<unsigned char> (buffer[1]);
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buffer += 2;
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return value;
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}
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void put16bits(char*& buffer, uint value) throw ()
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{
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buffer[0] = (value & 0xFF00) >> 8;
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buffer[1] = value & 0xFF;
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buffer += 2;
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}
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void put32bits(char*& buffer, unsigned long value) throw ()
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{
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buffer[0] = (value & 0xFF000000) >> 24;
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buffer[1] = (value & 0xFF0000) >> 16;
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buffer[2] = (value & 0xFF00) >> 16;
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buffer[3] = (value & 0xFF) >> 16;
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buffer += 4;
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}
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struct dns_msg
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{
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uint id;
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uint qr;
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uint opcode;
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uint aa;
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uint tc;
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uint rd;
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uint ra;
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uint rcode;
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uint qdCount;
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uint anCount;
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uint nsCount;
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uint arCount;
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};
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dns_msg *decode_hdr(const char *buffer)
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{
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dns_msg *hdr = new dns_msg;
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hdr->id = get16bits(buffer);
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uint fields = get16bits(buffer);
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hdr->qr = fields & 0x8000;
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hdr->opcode = fields & 0x7800;
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hdr->aa = fields & 0x0400;
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hdr->tc = fields & 0x0200;
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hdr->rd = fields & 0x0100;
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hdr->ra = fields & 0x8000;
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hdr->qdCount = get16bits(buffer);
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hdr->anCount = get16bits(buffer);
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hdr->nsCount = get16bits(buffer);
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hdr->arCount = get16bits(buffer);
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return hdr;
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}
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void code_domain(char*& buffer, const std::string& domain) throw()
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{
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int start(0), end; // indexes
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llarp::LogInfo("domain [", domain, "]");
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while ((end = domain.find('.', start)) != std::string::npos)
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{
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*buffer++ = end - start; // label length octet
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for (int i=start; i<end; i++)
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{
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*buffer++ = domain[i]; // label octets
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llarp::LogInfo("Writing ", domain[i], " at ", i);
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}
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start = end + 1; // Skip '.'
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}
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llarp::LogInfo("start ", start, " domain size ", domain.size());
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*buffer++ = domain.size() - start; // last label length octet
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for (int i=start; i<domain.size(); i++)
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{
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*buffer++ = domain[i]; // last label octets
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llarp::LogInfo("Writing ", domain[i], " at ", i);
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}
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*buffer++ = 0;
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}
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struct dns_response
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{
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std::string m_name;
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uint m_type;
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uint m_class;
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unsigned long m_ttl;
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uint m_rdLength;
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std::string m_rdata;
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};
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int
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main(int argc, char *argv[])
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{
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int code = 1;
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llarp::LogInfo("Starting up server");
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struct sockaddr_in m_address;
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int m_sockfd;
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m_sockfd = socket(AF_INET, SOCK_DGRAM, 0);
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m_address.sin_family = AF_INET;
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m_address.sin_addr.s_addr = INADDR_ANY;
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m_address.sin_port = htons(1053);
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int rbind = bind(m_sockfd, (struct sockaddr *) & m_address,
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sizeof (struct sockaddr_in));
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if (rbind != 0) {
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llarp::LogError("Could not bind: ", strerror(errno));
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return 0;
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}
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const size_t BUFFER_SIZE = 1024;
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const size_t HDR_OFFSET = 12;
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char buffer[BUFFER_SIZE]; // 1024 is buffer size
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struct sockaddr_in clientAddress;
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socklen_t addrLen = sizeof (struct sockaddr_in);
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signal(SIGINT, handle_signal);
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while(!done)
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{
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// sigint quits after next packet
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int nbytes = recvfrom(m_sockfd, buffer, BUFFER_SIZE, 0,
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(struct sockaddr *) &clientAddress, &addrLen);
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llarp::LogInfo("Received Bytes ", nbytes);
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const char* p_buffer = buffer;
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dns_msg *msg = decode_hdr(p_buffer);
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//llarp::LogInfo("DNS_MSG size", sizeof(dns_msg));
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p_buffer += HDR_OFFSET;
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std::string m_qName = "";
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int length = *p_buffer++;
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//llarp::LogInfo("qNamLen", length);
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while (length != 0) {
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for (int i = 0; i < length; i++) {
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char c = *p_buffer++;
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m_qName.append(1, c);
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}
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length = *p_buffer++;
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if (length != 0) m_qName.append(1,'.');
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}
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uint m_qType = get16bits(p_buffer);
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uint m_qClass = get16bits(p_buffer);
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llarp::LogInfo("qName ", m_qName);
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llarp::LogInfo("qType ", m_qType);
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llarp::LogInfo("qClass ", m_qClass);
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std::string copy(m_qName);
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sockaddr *hostRes = resolveHost((char *)copy.c_str());
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if (!hostRes)
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{
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exit(0);
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}
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llarp::Addr anIp(*hostRes);
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llarp::LogInfo("DNS got ", anIp);
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/*
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m_query.decode(buffer, nbytes);
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m_query.asString();
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m_resolver.process(m_query, m_response);
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m_response.asString();
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*/
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memset(buffer, 0, BUFFER_SIZE);
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char* write_buffer = buffer;
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char* bufferBegin = buffer;
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// build header
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put16bits(write_buffer, msg->id);
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int fields = (1 << 15); // QR => message type, 1 = response
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fields += (0 << 14); // I think opcode is always 0
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fields += 3; // response code (3 => not found, 0 = Ok)
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put16bits(write_buffer, fields);
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put16bits(write_buffer, 1); // QD (number of questions)
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put16bits(write_buffer, 1); // AN (number of answers)
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put16bits(write_buffer, 0); // NS (number of auth RRs)
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put16bits(write_buffer, 0); // AR (number of Additional RRs)
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write_buffer += HDR_OFFSET;
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// code question
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llarp::LogInfo("qName2 ", m_qName);
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printf("at0 [%d]\n", write_buffer);
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// 0123456789
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// 3bob3com1\0
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code_domain(write_buffer, m_qName);
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printf("at1 [%d]\n", write_buffer);
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put16bits(write_buffer, m_qType);
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put16bits(write_buffer, m_qClass);
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printf("at3 [%d]\n", write_buffer);
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// code answer
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std::string resp_str(inet_ntoa(*anIp.addr4()));
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code_domain(write_buffer, "");
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put16bits(write_buffer, m_qType);
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put16bits(write_buffer, m_qClass);
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put32bits(write_buffer, 0); // ttl
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put16bits(write_buffer, 1); // rdLength
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uint out_bytes = write_buffer - bufferBegin;
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llarp::LogInfo("Sending ", out_bytes, " bytes");
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//nbytes = m_response.code(buffer);
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sendto(m_sockfd, buffer, out_bytes, 0, (struct sockaddr *) &clientAddress, addrLen);
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}
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/*
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std::string host("www.google.com");
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sockaddr *hostRes = resolveHost((char *)host.c_str());
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if (!hostRes)
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{
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exit(0);
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}
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llarp::Addr anIp(*hostRes);
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llarp::LogInfo("DNS got ", anIp);
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*/
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return code;
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}
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