lokinet/llarp/dnsd.cpp
2018-10-06 12:04:52 -05:00

500 lines
16 KiB
C++

#include <llarp/dnsd.hpp>
#include <llarp/net.hpp>
extern dns_tracker dns_udp_tracker;
#ifdef _WIN32
#define wmin(x, y) (((x) < (y)) ? (x) : (y))
#define MIN wmin
#endif
ssize_t
raw_sendto_dns_hook_func(void *sock, const struct sockaddr *from,
const void *buffer, size_t length)
{
int *fd = (int *)sock;
// how do we get to these??
socklen_t addrLen = sizeof(struct sockaddr_in);
return sendto(*fd, (const char *)buffer, length, 0, from, addrLen);
}
ssize_t
llarp_sendto_dns_hook_func(void *sock, const struct sockaddr *from,
const void *buffer, size_t length)
{
struct llarp_udp_io *udp = (struct llarp_udp_io *)sock;
if(!udp)
{
llarp::LogWarn("couldnt cast to udp");
return 0;
}
// llarp::LogInfo("hook sending ", udp, " bytes: ", length);
// udp seems ok
// this call isn't calling the function...
// llarp::ev_io * evio = static_cast< llarp::ev_io * >(udp->impl);
// printf("ev_io[%x]\n", evio);
return llarp_ev_udp_sendto(udp, from, buffer, length);
}
void
write404_dnss_response(const struct sockaddr *from,
dnsd_question_request *request)
{
const size_t BUFFER_SIZE = 1024 + (request->question.name.size() * 2);
char buf[BUFFER_SIZE];
memset(buf, 0, BUFFER_SIZE);
char *write_buffer = buf;
char *bufferBegin = buf;
// build header
put16bits(write_buffer, request->id);
int fields = (1 << 15); // QR => message type, 1 = response
fields += (0 << 14); // I think opcode is always 0
fields += 3; // response code (3 => not found, 0 = Ok)
put16bits(write_buffer, fields);
put16bits(write_buffer, 1); // QD (number of questions)
put16bits(write_buffer, 1); // AN (number of answers)
put16bits(write_buffer, 0); // NS (number of auth RRs)
put16bits(write_buffer, 0); // AR (number of Additional RRs)
// code question
code_domain(write_buffer, request->question.name);
put16bits(write_buffer, request->question.type);
put16bits(write_buffer, request->question.qClass);
// code answer
code_domain(write_buffer, request->question.name); // com, type=6, ttl=0
put16bits(write_buffer, request->question.type);
put16bits(write_buffer, request->question.qClass);
put32bits(write_buffer, 1); // ttl
put16bits(write_buffer, 1); // rdLength
*write_buffer++ = 0; // write a null byte
uint out_bytes = write_buffer - bufferBegin;
llarp::LogDebug("Sending 404, ", out_bytes, " bytes");
// struct llarp_udp_io *udp = (struct llarp_udp_io *)request->user;
request->sendto_hook(request->user, from, buf, out_bytes);
}
void
writecname_dnss_response(std::string cname, const struct sockaddr *from,
dnsd_question_request *request)
{
const size_t BUFFER_SIZE = 1024 + (request->question.name.size() * 2);
char buf[BUFFER_SIZE]; // heh, another UNIX compiler extension: VLAs in C++
memset(buf, 0, BUFFER_SIZE);
char *write_buffer = buf;
char *bufferBegin = buf;
// build header
put16bits(write_buffer, request->id);
int fields = (1 << 15); // QR => message type, 1 = response
fields += (0 << 14); // I think opcode is always 0
fields += 0; // response code (3 => not found, 0 = Ok)
// fields |= 1UL << 7; // RA recursion available
// fields |= 1UL << 8; // RD recursion desired
// fields |= 1UL << 9; // 9 is truncate, forces TCP
put16bits(write_buffer, fields);
put16bits(write_buffer, 1); // QD (number of questions)
put16bits(write_buffer, 1); // AN (number of answers)
put16bits(write_buffer, 1); // NS (number of auth RRs)
put16bits(write_buffer, 1); // AR (number of Additional RRs)
// code question
code_domain(write_buffer, request->question.name);
put16bits(write_buffer, request->question.type);
put16bits(write_buffer, request->question.qClass);
// code answer
code_domain(write_buffer, request->question.name); // com, type=6, ttl=0
put16bits(write_buffer, 5); // cname
put16bits(write_buffer, request->question.qClass);
put32bits(write_buffer, 1); // ttl
put16bits(write_buffer, cname.length() + 2); // rdLength
code_domain(write_buffer, cname); // com, type=6, ttl=0
// location of cname
//*write_buffer++ = ip[0];
//*write_buffer++ = ip[1];
// write auth RR
code_domain(write_buffer, cname); // com, type=6, ttl=0
put16bits(write_buffer, 2); // NS
put16bits(write_buffer, request->question.qClass);
put32bits(write_buffer, 1); // ttl
std::string local("ns1.loki");
put16bits(write_buffer, local.length() + 2); // rdLength
code_domain(write_buffer, local); // com, type=6, ttl=0
// write addl RR
code_domain(write_buffer, local); // com, type=6, ttl=0
put16bits(write_buffer, 1); // A
put16bits(write_buffer, request->question.qClass);
put32bits(write_buffer, 1); // ttl
put16bits(write_buffer, 4); // rdLength
*write_buffer++ = 127;
*write_buffer++ = 0;
*write_buffer++ = 0;
*write_buffer++ = 1;
uint out_bytes = write_buffer - bufferBegin;
llarp::LogDebug("Sending cname, ", out_bytes, " bytes");
// struct llarp_udp_io *udp = (struct llarp_udp_io *)request->user;
request->sendto_hook(request->user, from, buf, out_bytes);
}
void
writesend_dnss_revresponse(std::string reverse, const struct sockaddr *from,
dnsd_question_request *request)
{
const size_t BUFFER_SIZE = 1024 + (request->question.name.size() * 2);
char buf[BUFFER_SIZE];
memset(buf, 0, BUFFER_SIZE);
char *write_buffer = buf;
char *bufferBegin = buf;
// build header
put16bits(write_buffer, request->id);
int fields = (1 << 15); // QR => message type, 1 = response
fields += (0 << 14); // I think opcode is always 0
fields += 0; // response code (3 => not found, 0 = Ok)
put16bits(write_buffer, fields);
put16bits(write_buffer, 1); // QD (number of questions)
put16bits(write_buffer, 1); // AN (number of answers)
put16bits(write_buffer, 0); // NS (number of auth RRs)
put16bits(write_buffer, 0); // AR (number of Additional RRs)
// code question
code_domain(write_buffer, request->question.name);
put16bits(write_buffer, request->question.type);
put16bits(write_buffer, request->question.qClass);
// code answer
code_domain(write_buffer, request->question.name); // com, type=6, ttl=0
put16bits(write_buffer, request->question.type);
put16bits(write_buffer, request->question.qClass);
put32bits(write_buffer, 1); // ttl
put16bits(write_buffer, reverse.length() + 2); // rdLength
code_domain(write_buffer, reverse);
uint out_bytes = write_buffer - bufferBegin;
llarp::LogDebug("Sending reverse: ", reverse, " ", out_bytes, " bytes");
// struct llarp_udp_io *udp = (struct llarp_udp_io *)request->user;
request->sendto_hook(request->user, from, buf, out_bytes);
}
// FIXME: we need an DNS answer not a sockaddr
// otherwise ttl, type and class can't be relayed correctly
void
writesend_dnss_response(struct sockaddr *hostRes, const struct sockaddr *from,
dnsd_question_request *request)
{
// llarp::Addr test(*from);
// llarp::LogInfo("from ", test);
if(!hostRes)
{
llarp::LogWarn("Failed to resolve ", request->question.name);
write404_dnss_response(from, request);
return;
}
const size_t BUFFER_SIZE = 1024 + (request->question.name.size() * 2);
char buf[BUFFER_SIZE];
memset(buf, 0, BUFFER_SIZE);
char *write_buffer = buf;
char *bufferBegin = buf;
// build header
put16bits(write_buffer, request->id);
int fields = (1 << 15); // QR => message type, 1 = response
fields += (0 << 14); // I think opcode is always 0
fields += 0; // response code (3 => not found, 0 = Ok)
put16bits(write_buffer, fields);
put16bits(write_buffer, 1); // QD (number of questions)
put16bits(write_buffer, 1); // AN (number of answers)
put16bits(write_buffer, 0); // NS (number of auth RRs)
put16bits(write_buffer, 0); // AR (number of Additional RRs)
// code question
code_domain(write_buffer, request->question.name);
put16bits(write_buffer, request->question.type);
put16bits(write_buffer, request->question.qClass);
// code answer
llarp::LogDebug("Sending question name: ", request->question.name);
code_domain(write_buffer, request->question.name); // com, type=6, ttl=0
put16bits(write_buffer, request->question.type);
put16bits(write_buffer, request->question.qClass);
put32bits(write_buffer, 1); // ttl
// has to be a string of 4 bytes
struct sockaddr_in *sin = (struct sockaddr_in *)hostRes;
unsigned char *ip = (unsigned char *)&sin->sin_addr.s_addr;
put16bits(write_buffer, 4); // rdLength
llarp::LogDebug("Sending ip: ", std::to_string(ip[0]), '.',
std::to_string(ip[1]), '.', std::to_string(ip[2]), '.',
std::to_string(ip[3]));
*write_buffer++ = ip[0];
*write_buffer++ = ip[1];
*write_buffer++ = ip[2];
*write_buffer++ = ip[3];
uint out_bytes = write_buffer - bufferBegin;
llarp::LogDebug("Sending found, ", out_bytes, " bytes");
// struct llarp_udp_io *udp = (struct llarp_udp_io *)request->user;
request->sendto_hook(request->user, from, buf, out_bytes);
}
void
handle_dnsc_result(dnsc_answer_request *client_request)
{
dnsd_question_request *server_request =
(dnsd_question_request *)client_request->user;
if(!server_request)
{
llarp::LogError("Couldn't map client requser user to a server request");
return;
}
// llarp::LogDebug("handle_dnsc_result - client request question type",
// std::to_string(client_request->question.type));
if(client_request->question.type == 12)
{
writesend_dnss_revresponse(client_request->revDNS, server_request->from,
server_request);
}
else
{
writesend_dnss_response(
client_request->found ? client_request->result.getSockAddr() : nullptr,
server_request->from, server_request);
}
llarp_host_resolved(client_request);
}
// our generic version
void
handle_recvfrom(const char *buffer, ssize_t nbytes, const struct sockaddr *from,
dnsd_question_request *request)
{
const size_t HDR_OFFSET = 12;
const char *p_buffer = buffer;
int rcode = (buffer[3] & 0x0F);
llarp::LogDebug("dnsd rcode ", rcode);
dns_msg_header *msg = decode_hdr(p_buffer);
p_buffer += HDR_OFFSET;
request->id = msg->id;
std::string m_qName = "";
int length = *p_buffer++;
while(length != 0)
{
for(int i = 0; i < length; i++)
{
char c = *p_buffer++;
m_qName.append(1, c);
}
length = *p_buffer++;
if(length != 0)
m_qName.append(1, '.');
}
request->question.name = m_qName;
request->question.type = get16bits(p_buffer);
request->question.qClass = get16bits(p_buffer);
llarp::LogDebug("qName ", request->question.name);
llarp::LogDebug("qType ", request->question.type);
llarp::LogDebug("qClass ", request->question.qClass);
/*
llarp::Addr test(*request->from);
llarp::LogInfo("DNS request from ", test);
llarp::Addr test2(from);
llarp::LogInfo("DNS request from ", test2);
*/
sockaddr *fromCopy =
new sockaddr(*from); // make our own sockaddr that won't get cleaned up
if(!request)
{
llarp::LogError("request is not configured");
return;
}
if(!request->context)
{
llarp::LogError("request context is not configured");
return;
}
if(request->context->intercept)
{
// llarp::Addr test(*from);
// llarp::LogInfo("from ", test);
dnsd_query_hook_response *intercept =
request->context->intercept(request->question.name, fromCopy, request);
// if(!forward_dns_request(m_qName))
if(intercept != nullptr)
{
llarp::LogDebug("hook returned a response");
if(intercept->dontSendResponse)
{
llarp::LogDebug("HOOKED: Not sending a response");
return;
}
if(intercept->dontLookUp == true && intercept->returnThis)
{
llarp::LogDebug("HOOKED: sending an immediate override");
// told that hook will handle overrides
writesend_dnss_response(intercept->returnThis, fromCopy, request);
return;
}
}
}
// FIXME: check request and context's client
if(!request->context)
{
llarp::LogError("dnsd request context was not a dnsd context");
writesend_dnss_response(nullptr, fromCopy, request);
return;
}
/*
struct dns_tracker *tracker = (struct dns_tracker *)request->context->tracker;
if (!tracker)
{
llarp::LogError("dnsd request context tracker was not a dns_tracker");
sockaddr *fromCopy = new sockaddr(*from);
writesend_dnss_response(nullptr, fromCopy, request);
return;
}
dnsd_context *dnsd = tracker->dnsd;
if (!dnsd)
{
llarp::LogError("tracker dnsd was not a dnsd context");
sockaddr *fromCopy = new sockaddr(*from);
writesend_dnss_response(nullptr, fromCopy, request);
return;
}
*/
if(request->llarp)
{
// make async request
llarp_resolve_host(&request->context->client, m_qName.c_str(),
&handle_dnsc_result, (void *)request);
}
else
{
// make raw/sync request
raw_resolve_host(&request->context->client, m_qName.c_str(),
&handle_dnsc_result, (void *)request);
}
}
void
llarp_handle_dnsd_recvfrom(struct llarp_udp_io *udp,
const struct sockaddr *saddr, const void *buf,
ssize_t sz)
{
if(!dns_udp_tracker.dnsd)
{
llarp::LogError("No tracker set in dnsd context");
return;
}
// create new request
dnsd_question_request *llarp_dns_request = new dnsd_question_request;
llarp_dns_request->context = dns_udp_tracker.dnsd; // set context
llarp_dns_request->from =
new sockaddr(*saddr); // make a copy of the sockaddr
llarp_dns_request->user = (void *)udp;
llarp_dns_request->llarp = true;
llarp_dns_request->sendto_hook =
&llarp_sendto_dns_hook_func; // set sock hook
// llarp::LogInfo("Server request's UDP ", llarp_dns_request->user);
handle_recvfrom((char *)buf, sz, llarp_dns_request->from, llarp_dns_request);
}
void
raw_handle_recvfrom(int *sockfd, const struct sockaddr *saddr, const void *buf,
ssize_t sz)
{
if(!dns_udp_tracker.dnsd)
{
llarp::LogError("No tracker set in dnsd context");
return;
}
dnsd_question_request *llarp_dns_request = new dnsd_question_request;
llarp_dns_request->context = dns_udp_tracker.dnsd; // set context
llarp_dns_request->from =
new sockaddr(*saddr); // make a copy of the sockaddr
llarp_dns_request->user = (void *)sockfd;
llarp_dns_request->llarp = false;
llarp_dns_request->sendto_hook = &raw_sendto_dns_hook_func;
handle_recvfrom((char *)buf, sz, llarp_dns_request->from, llarp_dns_request);
}
bool
llarp_dnsd_init(struct dnsd_context *const dnsd,
struct llarp_logic *const logic,
struct llarp_ev_loop *const netloop,
const llarp::Addr &dnsd_sockaddr,
const llarp::Addr &dnsc_sockaddr)
{
// struct sockaddr_in bindaddr;
/*
llarp::Addr dnsd_addr;
bool ifRes = GetIFAddr(std::string(dnsd_ifname), dnsd_addr, AF_INET);
if (!ifRes)
{
llarp::LogError("Couldn't init dns server, can't resolve interface: ",
dnsd_ifname); return false;
}
llarp::LogInfo("DNSd interface ip ", dnsd_addr);
*/
/*
bindaddr.sin_addr.s_addr = inet_addr("127.0.0.1"); // network byte
bindaddr.sin_family = AF_INET;
bindaddr.sin_port = htons(dnsd_port);
*/
dnsd->udp.user = &dns_udp_tracker;
dnsd->udp.recvfrom = &llarp_handle_dns_recvfrom;
dnsd->udp.tick = nullptr;
dns_udp_tracker.dnsd = dnsd;
dnsd->tracker = &dns_udp_tracker; // register global tracker with context
dnsd->intercept = nullptr; // set default intercepter
// set up fresh socket
dnsd->client.udp = new llarp_udp_io;
dnsd->client.udp->user = &dns_udp_tracker;
dnsd->client.udp->recvfrom = &llarp_handle_dns_recvfrom;
dnsd->client.udp->tick = nullptr;
// configure dns client
// llarp::LogInfo("DNSd setting relay to ", dnsc_sockaddr);
if(!llarp_dnsc_init(&dnsd->client, logic, netloop, dnsc_sockaddr))
{
llarp::LogError("Couldnt init dns client");
return false;
}
if(netloop)
{
llarp::LogInfo("DNSd binding to ", dnsd_sockaddr);
return llarp_ev_add_udp(netloop, &dnsd->udp,
(const sockaddr *)dnsd_sockaddr)
!= -1;
}
else
{
return true;
}
}