lokinet/llarp/dns_dotlokilookup.cpp

#include <llarp/dns_dotlokilookup.hpp>
#include <llarp/handlers/tun.hpp>
#include <llarp/service/context.hpp>

std::string const default_chars =
    "abcdefghijklmnaoqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ1234567890";

#include <random>

std::string
random_string(size_t len = 15, std::string const &allowed_chars = default_chars)
{
  std::mt19937_64 gen{std::random_device()()};

  std::uniform_int_distribution< size_t > dist{0, allowed_chars.length() - 1};

  std::string ret;

  std::generate_n(std::back_inserter(ret), len,
                  [&] { return allowed_chars[dist(gen)]; });
  return ret;
}

struct check_query_simple_request
{
  const struct sockaddr *from;  // source
  dnsd_question_request *request;
};

std::unordered_map< std::string, struct dnsd_query_hook_response * >
    loki_tld_lookup_cache;

void
llarp_dotlokilookup_checkQuery(void *u, uint64_t orig, uint64_t left)
{
  if(left)
    return;
  // struct check_query_request *request = static_cast< struct
  // check_query_request * >(u);
  struct check_query_simple_request *qr =
      static_cast< struct check_query_simple_request * >(u);
  dotLokiLookup *dll = (dotLokiLookup *)qr->request->context->user;
  if(!dll)
  {
    llarp::LogError("DNSd dotLokiLookup is not configured");
    write404_dnss_response(qr->from, qr->request);
    delete qr;
    return;
  }

  // we do have result
  // if so send that
  // else
  // if we have a free private ip, send that
  llarp::service::Address addr;
  if(!addr.FromString(qr->request->question.name))
  {
    llarp::LogWarn("Could not base32 decode address: ",
                   qr->request->question.name);
    write404_dnss_response(qr->from, qr->request);
    delete qr;
    return;
  }
  // cache hit
  auto itr = loki_tld_lookup_cache.find(addr.ToString());
  if(itr != loki_tld_lookup_cache.end())
  {
    llarp::LogDebug("Found in .loki lookup cache");
    writesend_dnss_response(itr->second->returnThis, qr->from, qr->request);
    delete qr;
    return;
  }

  struct dns_pointer *free_private = dns_iptracker_get_free(dll->ip_tracker);
  if(free_private)
  {
    // in_addr ip_address = ((sockaddr_in *)free_private->hostResult)->sin_addr;

    /*
    llarp::handlers::TunEndpoint *tunEndpoint =
        (llarp::handlers::TunEndpoint *)dll->user;
    if (!tunEndpoint)
    {
      llarp::LogWarn("dotLokiLookup user isnt a tunEndpoint: ", dll->user);
      return;
    }
    bool mapResult = tunEndpoint->MapAddress(addr,
    free_private->hostResult.tohl()); if(!mapResult)
    {
      delete qr;
      return;
    }
    */
    llarp::service::Context *routerHiddenServiceContext =
        (llarp::service::Context *)dll->user;
    if(!routerHiddenServiceContext)
    {
      llarp::LogWarn("dotLokiLookup user isnt a service::Context: ", dll->user);
      write404_dnss_response(qr->from, qr->request);
      delete qr;
      return;
    }
    bool mapResult = routerHiddenServiceContext->MapAddressAll(
        addr, free_private->hostResult);
    if(!mapResult)
    {
      llarp::LogWarn("dotLokiLookup failed to map address");
      write404_dnss_response(qr->from, qr->request);
      delete qr;
      return;
    }

    // make a dnsd_query_hook_response for the cache
    dnsd_query_hook_response *response = new dnsd_query_hook_response;
    response->dontLookUp               = true;
    response->dontSendResponse         = false;
    // llarp::Addr test(*free_private->hostResult.getSockAddr());
    // llarp::LogInfo("IP Test: ", test);
    response->returnThis = free_private->hostResult;
    llarp::LogInfo("Saving ", qr->request->question.name);
    loki_tld_lookup_cache[qr->request->question.name] = response;
    // we can't delete response now...

    // FIXME: flush cache to disk
    // on crash we'll need to bring up all the same IPs we assigned before...
    writesend_dnss_response(response->returnThis, qr->from, qr->request);
    delete qr;
    return;
  }
  // else
  llarp::LogInfo("Sending cname to delay");
  writecname_dnss_response(
      random_string(49, "abcdefghijklmnopqrstuvwxyz") + "bob.loki", qr->from,
      qr->request);
  delete qr;
}

std::vector< std::string >
split(std::string str)
{
  size_t pos = 0;
  std::string token;
  std::string s(str);
  std::vector< std::string > tokens;
  while((pos = s.find(".")) != std::string::npos)
  {
    token = s.substr(0, pos);
    // llarp::LogInfo("token [", token, "]");
    tokens.push_back(token);
    s.erase(0, pos + 1);
  }
  token = s.substr(0, pos);
  tokens.push_back(token);
  // llarp::LogInfo("token [", token, "]");
  return tokens;
}

struct reverse_handler_iter_context
{
  std::string lName;
  const struct sockaddr *from;
  const struct dnsd_question_request *request;
};

bool
ReverseHandlerIter(struct llarp::service::Context::endpoint_iter *endpointCfg)
{
  reverse_handler_iter_context *context =
      (reverse_handler_iter_context *)endpointCfg->user;
  // llarp::LogInfo("context ", context->request->question.name);
  // llarp::LogInfo("Checking ", lName);
  llarp::handlers::TunEndpoint *tunEndpoint =
      (llarp::handlers::TunEndpoint *)endpointCfg->endpoint;
  if(!tunEndpoint)
  {
    llarp::LogError("No tunnel endpoint found");
    return true;  // still continue
  }
  // llarp::LogInfo("for ", tunEndpoint->tunif.ifaddr);
  std::string checkStr(tunEndpoint->tunif.ifaddr);
  std::vector< std::string > tokensSearch = split(context->lName);
  std::vector< std::string > tokensCheck  = split(checkStr);

  // well the tunif is just one ip on a network range...
  // support "b._dns-sd._udp.0.0.200.10.in-addr.arpa"
  size_t searchTokens  = tokensSearch.size();
  std::string searchIp = tokensSearch[searchTokens - 3] + "."
      + tokensSearch[searchTokens - 4] + "." + tokensSearch[searchTokens - 5]
      + "." + tokensSearch[searchTokens - 6];
  std::string checkIp = tokensCheck[0] + "." + tokensCheck[1] + "."
      + tokensCheck[2] + "." + tokensCheck[3];
  llarp::LogDebug(searchIp, " vs ", checkIp);

  llarp::IPRange range = llarp::iprange_ipv4(
      stoi(tokensCheck[0]), stoi(tokensCheck[1]), stoi(tokensCheck[2]),
      stoi(tokensCheck[3]), tunEndpoint->tunif.netmask);  // create range
  // hack atm to work around limitations in ipaddr_ipv4_bits and llarp::IPRange
  llarp::huint32_t searchIPv4_fixed = llarp::ipaddr_ipv4_bits(
      stoi(tokensSearch[searchTokens - 6]),
      stoi(tokensSearch[searchTokens - 5]),
      stoi(tokensSearch[searchTokens - 4]),
      stoi(tokensSearch[searchTokens
                        - 3]));  // create ip (llarp::Addr is untrustworthy atm)
  llarp::huint32_t searchIPv4_search = llarp::ipaddr_ipv4_bits(
      stoi(tokensSearch[searchTokens - 3]),
      stoi(tokensSearch[searchTokens - 4]),
      stoi(tokensSearch[searchTokens - 5]),
      stoi(tokensSearch[searchTokens
                        - 6]));  // create ip (llarp::Addr is untrustworthy atm)

  // bool inRange = range.Contains(searchAddr.xtohl());
  bool inRange = range.Contains(searchIPv4_search);

  llarp::Addr searchAddr(searchIp);
  llarp::Addr checkAddr(checkIp);
  llarp::LogDebug(searchAddr, " vs ", range.ToString(), " = ",
                  inRange ? "inRange" : "not match");

  if(inRange)
  {
    llarp::service::Address addr =
        tunEndpoint->ObtainAddrForIP(searchIPv4_fixed);
    if(addr.IsZero())
    {
      write404_dnss_response(context->from,
                             (dnsd_question_request *)context->request);
    }
    else
    {
      writesend_dnss_revresponse(addr.ToString(), context->from,
                                 (dnsd_question_request *)context->request);
    }
    return false;
  }
  return true;  // we don't do anything with the result yet
}

dnsd_query_hook_response *
llarp_dotlokilookup_handler(std::string name, const struct sockaddr *from,
                            struct dnsd_question_request *const request)
{
  dnsd_query_hook_response *response = new dnsd_query_hook_response;
  response->dontLookUp               = false;
  response->dontSendResponse         = false;
  response->returnThis               = nullptr;
  llarp::LogDebug("Hooked ", name);
  std::string lName = name;
  std::transform(lName.begin(), lName.end(), lName.begin(), ::tolower);
  // llarp::LogDebug("Transformed ", lName);

  // 253.0.200.10.in-addr.arpa
  if(lName.find(".in-addr.arpa") != std::string::npos)
  {
    // llarp::LogDebug("Checking ", lName);
    dotLokiLookup *dll = (dotLokiLookup *)request->context->user;
    llarp::service::Context *routerHiddenServiceContext =
        (llarp::service::Context *)dll->user;
    if(!routerHiddenServiceContext)
    {
      llarp::LogWarn("dotLokiLookup user isnt a service::Context: ", dll->user);
      return response;
    }
    // llarp::LogDebug("Starting rev iter for ", lName);
    // which range?
    // for each tun interface
    struct reverse_handler_iter_context context;
    context.lName   = lName;
    context.from    = from;
    context.request = request;

    struct llarp::service::Context::endpoint_iter i;
    i.user   = &context;
    i.index  = 0;
    i.visit  = &ReverseHandlerIter;
    bool res = routerHiddenServiceContext->iterate(i);
    if(!res)
    {
      llarp::LogInfo("Reverse is ours");
      response->dontSendResponse = true;  // should have already sent it
    }
    else
    {
      llarp::LogInfo("Reverse is not ours");
    }
  }
  else if((lName.length() > 5 && lName.substr(lName.length() - 5, 5) == ".loki")
          || (lName.length() > 6
              && lName.substr(lName.length() - 6, 6) == ".loki."))
  {
    llarp::LogInfo("Detect Loki Lookup for ", lName);
    auto cache_check = loki_tld_lookup_cache.find(lName);
    if(cache_check != loki_tld_lookup_cache.end())
    {
      // was in cache
      llarp::LogInfo("Reused address from LokiLookupCache");
      // FIXME: avoid the response allocation if you could
      delete response;
      return cache_check->second;
    }

    // decode string into HS addr
    llarp::service::Address addr;
    if(!addr.FromString(lName))
    {
      llarp::LogWarn("Could not base32 decode address");
      response->dontLookUp = true;  // will return nullptr which will give a 404
      return response;
    }
    llarp::LogDebug("Base32 decoded address ", addr);

    // start path build early (if you're looking it up, you're probably going to
    // use it)
    // main_router_prefetch(ctx, addr);

    // schedule future response
    check_query_simple_request *qr = new check_query_simple_request;
    qr->from                       = from;
    qr->request                    = request;
    // nslookup on osx is about 5 sec before a retry, 2s on linux
    llarp_logic_call_later(request->context->client.logic,
                           {2000, qr, &llarp_dotlokilookup_checkQuery});

    response->dontSendResponse = true;  // will send it shortly
  }
  return response;
}