binding.cc

#include <node.h>
#include <node_buffer.h>
#include <nan.h>
#include <pcap/pcap.h>
#include <stdlib.h>
#include <string.h>

#ifdef _MSC_VER
# include "windows_polyfills.h"
#else
# include <arpa/inet.h>
# include <sys/ioctl.h>
#endif

#if __linux__
# include <dlfcn.h>
  // Without immediate mode some architectures (e.g. Linux with TPACKET_V3)
  // will buffer replies and potentially cause a *long* delay in packet
  // reception

  // pcap_set_immediate_mode is new as of libpcap 1.5.1, so we check for
  // this new method dynamically ...
  typedef void* (*set_immediate_fn)(pcap_t *p, int immediate);
  void* _pcap_lib_handle = dlopen("libpcap.so", RTLD_LAZY);
  set_immediate_fn set_immediate_mode =
    (set_immediate_fn)(dlsym(_pcap_lib_handle, "pcap_set_immediate_mode"));
#endif

using namespace node;
using namespace v8;

static Nan::Persistent<FunctionTemplate> constructor;
static Nan::Persistent<String> emit_symbol;
static Nan::Persistent<String> packet_symbol;

void SetAddrStringHelper(const char* key,
                         sockaddr *addr,
                         Local<Object> Address) {
  if (key && addr) {
    char dst_addr[INET6_ADDRSTRLEN + 1] = {0};
    char* src = 0;
    socklen_t size = 0;
    if (addr->sa_family == AF_INET) {
      struct sockaddr_in* saddr = (struct sockaddr_in*) addr;
      src = (char*) &(saddr->sin_addr);
      size = INET_ADDRSTRLEN;
    } else {
      struct sockaddr_in6* saddr6 = (struct sockaddr_in6*) addr;
      src = (char*) &(saddr6->sin6_addr);
      size = INET6_ADDRSTRLEN;
    }
    const char* address = inet_ntop(addr->sa_family, src, dst_addr, size);
    if (address == nullptr) {
      Nan::Set(Address,
               Nan::New<String>(key).ToLocalChecked(),
               Nan::Undefined()).FromJust();
    } else {
      Nan::Set(Address,
               Nan::New<String>(key).ToLocalChecked(),
               Nan::New<String>(address).ToLocalChecked()).FromJust();
    }
  }
}

class Pcap : public Nan::ObjectWrap {
  public:
    Nan::Persistent<Function> Emit;
    Nan::AsyncResource async_res;
    bool closing;
    bool handling_packets;
#ifdef _WIN32
    HANDLE wait;
    uv_async_t async;
#else
    uv_poll_t poll_handle;
    int fd;
#endif
    pcap_t *pcap_handle;

    char *buffer_data;
    size_t buffer_length;

    Pcap() : async_res("cap:packet") {
      pcap_handle = nullptr;
      buffer_data = nullptr;
      buffer_length = 0;
      closing = false;
      handling_packets = false;
#ifdef _WIN32
      wait = nullptr;
#endif
    }

    ~Pcap() {
      close();
      Emit.Reset();
    }

    bool close() {
      if (pcap_handle && !closing) {
#ifdef _WIN32
        if (wait) {
          UnregisterWait(wait);
          wait = nullptr;
        }
        uv_close((uv_handle_t*)&async, cb_close);
#else
        uv_poll_stop(&poll_handle);
#endif
        closing = true;
        cleanup();
        return true;
      }
      return false;
    }

    void cleanup() {
      if (pcap_handle && !handling_packets) {
        pcap_close(pcap_handle);
        pcap_handle = nullptr;
        buffer_data = nullptr;
        buffer_length = 0;
        Unref();
      }
    }

    static void EmitPacket(u_char* user,
                           const struct pcap_pkthdr* pkt_hdr,
                           const u_char* pkt_data) {
      Nan::HandleScope scope;
      Pcap *obj = (Pcap*) user;

      size_t copy_len = pkt_hdr->caplen;
      bool truncated = false;
      if (copy_len > obj->buffer_length) {
        copy_len = obj->buffer_length;
        truncated = true;
      }
      memcpy(obj->buffer_data, pkt_data, copy_len);

      Local<Value> emit_argv[3] = {
        Nan::New<String>(packet_symbol),
        Nan::New<Number>(copy_len),
        Nan::New<Boolean>(truncated)
      };
      obj->async_res.runInAsyncScope(
        Nan::New<Object>(obj->persistent()),
        Nan::New<Function>(obj->Emit),
        3,
        emit_argv
      );
    }

#ifdef _WIN32
# if NAUV_UVVERSION < 0x000b17
    static void cb_packets(uv_async_t* handle, int status) {
      assert(status == 0);
# else
    static void cb_packets(uv_async_t* handle) {
# endif
      Pcap *obj = (Pcap*)handle->data;
      int packet_count;

      if (obj->closing)
        return obj->cleanup();

      obj->handling_packets = true;

      do {
        packet_count = pcap_dispatch(obj->pcap_handle,
                                     1,
                                     Pcap::EmitPacket,
                                     (u_char*)obj);
      } while (packet_count > 0 && !obj->closing);

      obj->handling_packets = false;
      if (obj->closing)
        obj->cleanup();
    }
    static void CALLBACK OnPacket(void* data, BOOLEAN didTimeout) {
      assert(!didTimeout);
      uv_async_t* async = (uv_async_t*)data;
      int r = uv_async_send(async);
      assert(r == 0);
    }
    static void cb_close(uv_handle_t* handle) {
    }
#else
    static void cb_packets(uv_poll_t* handle, int status, int events) {
      assert(status == 0);
      Pcap *obj = (Pcap*)handle->data;
      int packet_count;

      if (obj->closing)
        return obj->cleanup();

      if (events & UV_READABLE) {
        obj->handling_packets = true;

        do {
          packet_count = pcap_dispatch(obj->pcap_handle,
                                       1,
                                       Pcap::EmitPacket,
                                       (u_char*)obj);
        } while (packet_count > 0 && !obj->closing);

        obj->handling_packets = false;
        if (obj->closing)
          obj->cleanup();
      }
    }
#endif

    static NAN_METHOD(New) {
      if (!info.IsConstructCall())
        return Nan::ThrowError("Use `new` to create instances of this object");

      Pcap *obj = new Pcap();
      obj->Wrap(info.This());

      obj->Emit.Reset(Local<Function>::Cast(
        Nan::Get(Nan::New<Object>(obj->persistent()),
                 Nan::New<String>(emit_symbol)).ToLocalChecked()
      ));

      info.GetReturnValue().Set(info.This());
    }

    static NAN_METHOD(Send) {
      Pcap *obj = Nan::ObjectWrap::Unwrap<Pcap>(info.This());
      size_t buffer_size = 0;

      if (info.Length() == 0)
        return Nan::ThrowTypeError("the first parameter must be a buffer");

      if (!Buffer::HasInstance(info[0]))
        return Nan::ThrowTypeError("first parameter must be a buffer");

      if (info.Length() >= 2) {
        if (!info[1]->IsUint32())
          return Nan::ThrowTypeError("length must be a positive integer");

        buffer_size = Nan::To<uint32_t>(info[1]).FromJust();
      }

#if NODE_MAJOR_VERSION == 0 && NODE_MINOR_VERSION < 10
      Local<Object> buffer_obj = info[0]->ToObject();
#else
      Local<Value> buffer_obj = info[0];
#endif
      if (info.Length() == 1)
        buffer_size = Buffer::Length(buffer_obj);
      else {
        if (buffer_size > Buffer::Length(buffer_obj)) {
          return Nan::ThrowTypeError(
            "size must be smaller or equal to buffer length"
          );
        }
      }

      if (pcap_sendpacket(obj->pcap_handle,
                          (const u_char*)(Buffer::Data(buffer_obj)),
                          (int)buffer_size) == -1) {
        return Nan::ThrowError(pcap_geterr(obj->pcap_handle));
      }

      return;
    }

    static NAN_METHOD(Open) {
      Pcap *obj = Nan::ObjectWrap::Unwrap<Pcap>(info.This());

      if (obj->pcap_handle)
        obj->close();

      if (info.Length() < 4)
        return Nan::ThrowTypeError("Expecting 4 arguments");

      if (!info[0]->IsString())
        return Nan::ThrowTypeError("device must be a string");

      if (!info[1]->IsString())
        return Nan::ThrowTypeError("filter must be a string");

      if (!info[2]->IsUint32())
        return Nan::ThrowTypeError("bufSize must be a positive integer");

      if (!Buffer::HasInstance(info[3]))
        return Nan::ThrowTypeError("buffer must be a Buffer");
        

      Nan::Utf8String device(info[0]);
      Nan::Utf8String filter(info[1]);
      int buffer_size = Nan::To<int32_t>(info[2]).FromJust();
#if NODE_MAJOR_VERSION == 0 && NODE_MINOR_VERSION < 10
      Local<Object> buffer_obj = info[3]->ToObject();
#else
      Local<Value> buffer_obj = info[3];
#endif
      struct bpf_program fp;
      bpf_u_int32 mask;
      bpf_u_int32 net;
      char errbuf[PCAP_ERRBUF_SIZE];

      obj->buffer_data = Buffer::Data(buffer_obj);
      obj->buffer_length = Buffer::Length(buffer_obj);

      if (pcap_lookupnet((char*)*device,
                         &net,
                         &mask,
                         errbuf) == -1) {
        net = 0;
        mask = 0;
        fprintf(stderr, "Warning: %s - This may not actually work\n", errbuf);
      }

      obj->pcap_handle = pcap_create((char*)*device, errbuf);

      if (obj->pcap_handle == nullptr)
        return Nan::ThrowError(errbuf);

      // 64KB is the max IPv4 packet size
      if (pcap_set_snaplen(obj->pcap_handle, 65535) != 0)
        return Nan::ThrowError("Unable to set snaplen");

      // Always use promiscuous mode
      if (pcap_set_promisc(obj->pcap_handle, 1) != 0)
        return Nan::ThrowError("Unable to set promiscuous mode");

      // Try to set buffer size. Sometimes the OS has a lower limit that it will
      // silently enforce.
      if (pcap_set_buffer_size(obj->pcap_handle, buffer_size) != 0)
        return Nan::ThrowError("Unable to set buffer size");

      // Set "timeout" on read, even though we are also setting nonblock below.
      // On Linux this is required.
      if (pcap_set_timeout(obj->pcap_handle, 1000) != 0)
        return Nan::ThrowError("Unable to set read timeout");

#if __linux__
      if (set_immediate_mode != nullptr)
        set_immediate_mode(obj->pcap_handle, 1);
#endif

      if (pcap_activate(obj->pcap_handle) != 0)
        return Nan::ThrowError(pcap_geterr(obj->pcap_handle));

      if (pcap_setnonblock(obj->pcap_handle, 1, errbuf) == -1)
        return Nan::ThrowError(errbuf);

      if (filter.length() != 0) {
        if (pcap_compile(obj->pcap_handle, &fp, (char*)*filter, 1, net) == -1)
          return Nan::ThrowError(pcap_geterr(obj->pcap_handle));

        if (pcap_setfilter(obj->pcap_handle, &fp) == -1)
          return Nan::ThrowError(pcap_geterr(obj->pcap_handle));

        pcap_freecode(&fp);
      }

#if defined(__APPLE_CC__) || defined(__APPLE__)
      // Work around buffering bug in BPF on OSX 10.6 as of May 19, 2010
      // This may result in dropped packets under load because it disables the
      // (broken) buffer
      // http://seclists.org/tcpdump/2010/q1/110
      #include <net/bpf.h>
      int fd = pcap_get_selectable_fd(obj->pcap_handle);
      int v = 1;
      ioctl(fd, BIOCIMMEDIATE, &v);
      // TODO - check return value
#endif

      int link_type = pcap_datalink(obj->pcap_handle);

      Local<Value> ret;
      switch (link_type) {
        case DLT_NULL:
          ret = Nan::New<String>("NULL").ToLocalChecked();
          break;
        case DLT_EN10MB: // most wifi interfaces pretend to be "ethernet"
          ret =  Nan::New<String>("ETHERNET").ToLocalChecked();
          break;
        case DLT_IEEE802_11_RADIO: // 802.11 "monitor mode"
          ret = Nan::New<String>("IEEE802_11_RADIO").ToLocalChecked();
          break;
        case DLT_LINUX_SLL: // "Linux cooked-mode capture"
          ret = Nan::New<String>("LINKTYPE_LINUX_SLL").ToLocalChecked();
          break;
        case DLT_RAW: // "raw IP"
          ret = Nan::New<String>("RAW").ToLocalChecked();
          break;
        default:
          snprintf(errbuf, PCAP_ERRBUF_SIZE, "Unknown linktype %d", link_type);
          ret = Nan::New<String>(errbuf).ToLocalChecked();
          break;
      }

      int r;
#ifdef _WIN32
      r = uv_async_init(uv_default_loop(),
                        &obj->async,
                        (uv_async_cb)cb_packets);
      assert(r == 0);
      obj->async.data = obj;
      r = RegisterWaitForSingleObject(
        &obj->wait,
        pcap_getevent(obj->pcap_handle),
        OnPacket,
        &obj->async,
        INFINITE,
        WT_EXECUTEINWAITTHREAD
      );
      if (!r) {
        char *errmsg = nullptr;
        FormatMessage(FORMAT_MESSAGE_ALLOCATE_BUFFER
                      | FORMAT_MESSAGE_FROM_SYSTEM
                      | FORMAT_MESSAGE_IGNORE_INSERTS,
                      nullptr,
                      GetLastError(),
                      MAKELANGID(LANG_NEUTRAL, SUBLANG_DEFAULT),
                      (LPTSTR)&errmsg,
                      0,
                      nullptr);
        return Nan::ThrowError(errmsg);
      }
#else
      obj->fd = pcap_get_selectable_fd(obj->pcap_handle);
      r = uv_poll_init(uv_default_loop(), &obj->poll_handle, obj->fd);
      assert(r == 0);
      r = uv_poll_start(&obj->poll_handle, UV_READABLE, cb_packets);
      assert(r == 0);
      obj->poll_handle.data = obj;
#endif

      obj->Ref();
      info.GetReturnValue().Set(ret);
    }

#ifdef _WIN32
    static NAN_METHOD(WIN_SetMin) {
      Pcap *obj = Nan::ObjectWrap::Unwrap<Pcap>(info.This());

      if (info.Length() < 1)
        return Nan::ThrowTypeError("missing min bytes value");

      if (!info[0]->IsUint32())
        return Nan::ThrowTypeError("min bytes must be a positive number");

      if (obj->pcap_handle == nullptr)
        return Nan::ThrowError("Not currently capturing/open");

      if (pcap_setmintocopy(obj->pcap_handle,
                            Nan::To<uint32_t>(info[0]).FromJust()) != 0) {
        return Nan::ThrowError("Unable to set min bytes");
      }

      return;
    }
#endif

    static NAN_METHOD(Close) {
      Pcap *obj = Nan::ObjectWrap::Unwrap<Pcap>(info.This());

      info.GetReturnValue().Set(Nan::New<Boolean>(obj->close()));
    }

    static void Initialize(Local<Object> target) {
      Nan::HandleScope scope;

      Local<FunctionTemplate> tpl = Nan::New<FunctionTemplate>(New);

      constructor.Reset(tpl);
      tpl->InstanceTemplate()->SetInternalFieldCount(1);
      tpl->SetClassName(Nan::New<String>("Cap").ToLocalChecked());

      Nan::SetPrototypeMethod(tpl, "send", Send);
      Nan::SetPrototypeMethod(tpl, "open", Open);
      Nan::SetPrototypeMethod(tpl, "close", Close);
#ifdef _WIN32
      Nan::SetPrototypeMethod(tpl, "setMinBytes", WIN_SetMin);
#endif

      emit_symbol.Reset(Nan::New<String>("emit").ToLocalChecked());
      packet_symbol.Reset(Nan::New<String>("packet").ToLocalChecked());

      Nan::Set(target,
               Nan::New<String>("Cap").ToLocalChecked(),
               Nan::GetFunction(tpl).ToLocalChecked()).FromJust();
    }
};

static NAN_METHOD(ListDevices) {
  char errbuf[PCAP_ERRBUF_SIZE];
  pcap_if_t *alldevs = nullptr, *cur_dev;
  pcap_addr_t *cur_addr;
  int i, j, af;

  Local<Object> Dev;
  Local<Object> Address;
  Local<Array> DevsArray;
  Local<Array> AddrArray;

  if (pcap_findalldevs(&alldevs, errbuf) == -1)
    return Nan::ThrowError(errbuf);

  DevsArray = Nan::New<Array>();

  for (i = 0, cur_dev = alldevs;
       cur_dev != nullptr;
       cur_dev = cur_dev->next, ++i) {
    Dev = Nan::New<Object>();
    AddrArray = Nan::New<Array>();

    Nan::Set(Dev,
             Nan::New<String>("name").ToLocalChecked(),
             Nan::New<String>(cur_dev->name).ToLocalChecked());
    if (cur_dev->description != nullptr) {
      Nan::Set(Dev,
               Nan::New<String>("description").ToLocalChecked(),
               Nan::New<String>(cur_dev->description).ToLocalChecked());
    }

    for (j = 0, cur_addr = cur_dev->addresses;
         cur_addr != nullptr;
         cur_addr = cur_addr->next) {
      if (cur_addr->addr) {
        af = cur_addr->addr->sa_family;
        if (af == AF_INET || af == AF_INET6) {
          Address = Nan::New<Object>();
          SetAddrStringHelper("addr", cur_addr->addr, Address);
          SetAddrStringHelper("netmask", cur_addr->netmask, Address);
          SetAddrStringHelper("broadaddr", cur_addr->broadaddr, Address);
          SetAddrStringHelper("dstaddr", cur_addr->dstaddr, Address);
          Nan::Set(AddrArray, j++, Address);
        }
      }
    }

    Nan::Set(Dev, Nan::New<String>("addresses").ToLocalChecked(), AddrArray);

    if (cur_dev->flags & PCAP_IF_LOOPBACK) {
      Nan::Set(Dev,
               Nan::New<String>("flags").ToLocalChecked(),
               Nan::New<String>("PCAP_IF_LOOPBACK").ToLocalChecked());
    }

    Nan::Set(DevsArray, i, Dev);
  }

  if (alldevs)
    pcap_freealldevs(alldevs);

  info.GetReturnValue().Set(DevsArray);
}

static NAN_METHOD(FindDevice) {
  Local<Value> ret;
  char errbuf[PCAP_ERRBUF_SIZE];
  char name4[INET_ADDRSTRLEN];
  char name6[INET6_ADDRSTRLEN];
  char *ip = nullptr;
  pcap_if_t *alldevs = nullptr, *dev;
  pcap_addr_t *addr;
  bool found = false;

  if (pcap_findalldevs(&alldevs, errbuf) == -1)
    return Nan::ThrowError(errbuf);

  if (info.Length() > 0) { 
    if (!info[0]->IsString())
      return Nan::ThrowTypeError("Expected string for IP");
    Nan::Utf8String ipstr(info[0]);
    ip = (char*)malloc(strlen(*ipstr) + 1);
    strcpy(ip, *ipstr);
  }

  for (dev = alldevs; dev != nullptr; dev = dev->next) {
    if (dev->addresses != nullptr) {
      for (addr = dev->addresses; addr != nullptr; addr = addr->next) {
        if (addr->addr->sa_family == AF_INET
            || addr->addr->sa_family == AF_INET6) {
          if (ip) {
            if (addr->addr->sa_family == AF_INET) {
              inet_ntop(AF_INET,
                        (char*)&(((struct sockaddr_in*)(addr->addr))->sin_addr),
                        name4, INET_ADDRSTRLEN);
              if (strcmp(ip, name4) != 0)
                continue;
            } else if (addr->addr->sa_family == AF_INET6) {
              inet_ntop(AF_INET6,
                        (char*)&(
                          ((struct sockaddr_in6*)(addr->addr))->sin6_addr
                        ),
                        name6, INET6_ADDRSTRLEN);
              if (strcmp(ip, name6) != 0)
                continue;
            }
          }
          ret = Nan::New<String>(dev->name).ToLocalChecked();
          found = true;
          break;
        }
      }
      if (found)
        break;
    }
  }

  if (alldevs)
    pcap_freealldevs(alldevs);

  if (ip)
    free(ip);

  info.GetReturnValue().Set(ret);
}

extern "C" {
  void init(Local<Object> target) {
    Nan::HandleScope scope;
    Pcap::Initialize(target);
    Nan::Set(target,
             Nan::New<String>("findDevice").ToLocalChecked(),
             Nan::GetFunction(Nan::New<FunctionTemplate>(FindDevice))
               .ToLocalChecked()).FromJust();
    Nan::Set(target,
             Nan::New<String>("deviceList").ToLocalChecked(),
             Nan::GetFunction(Nan::New<FunctionTemplate>(ListDevices))
               .ToLocalChecked()).FromJust();
  }

  NODE_MODULE(cap, init);
}