webrtc/base/schanneladapter.cc - src - Git at Google

 /*
  *  Copyright 2004 The WebRTC Project Authors. All rights reserved.
  *
  *  Use of this source code is governed by a BSD-style license
  *  that can be found in the LICENSE file in the root of the source
  *  tree. An additional intellectual property rights grant can be found
  *  in the file PATENTS.  All contributing project authors may
  *  be found in the AUTHORS file in the root of the source tree.
  */

 #include "webrtc/base/win32.h"
 #define SECURITY_WIN32
 #include <security.h>
 #include <schannel.h>

 #include <iomanip>
 #include <vector>

 #include "webrtc/base/common.h"
 #include "webrtc/base/logging.h"
 #include "webrtc/base/schanneladapter.h"
 #include "webrtc/base/sec_buffer.h"
 #include "webrtc/base/thread.h"

 namespace rtc {

 /////////////////////////////////////////////////////////////////////////////
 // SChannelAdapter
 /////////////////////////////////////////////////////////////////////////////

 extern const ConstantLabel SECURITY_ERRORS[];

 const ConstantLabel SCHANNEL_BUFFER_TYPES[] = {
   KLABEL(SECBUFFER_EMPTY),              //  0
   KLABEL(SECBUFFER_DATA),               //  1
   KLABEL(SECBUFFER_TOKEN),              //  2
   KLABEL(SECBUFFER_PKG_PARAMS),         //  3
   KLABEL(SECBUFFER_MISSING),            //  4
   KLABEL(SECBUFFER_EXTRA),              //  5
   KLABEL(SECBUFFER_STREAM_TRAILER),     //  6
   KLABEL(SECBUFFER_STREAM_HEADER),      //  7
   KLABEL(SECBUFFER_MECHLIST),           // 11
   KLABEL(SECBUFFER_MECHLIST_SIGNATURE), // 12
   KLABEL(SECBUFFER_TARGET),             // 13
   KLABEL(SECBUFFER_CHANNEL_BINDINGS),   // 14
   LASTLABEL
 };

 void DescribeBuffer(LoggingSeverity severity, const char* prefix,
                     const SecBuffer& sb) {
   LOG_V(severity)
     << prefix
     << "(" << sb.cbBuffer
     << ", " << FindLabel(sb.BufferType & ~SECBUFFER_ATTRMASK,
                           SCHANNEL_BUFFER_TYPES)
     << ", " << sb.pvBuffer << ")";
 }

 void DescribeBuffers(LoggingSeverity severity, const char* prefix,
                      const SecBufferDesc* sbd) {
   if (!LOG_CHECK_LEVEL_V(severity))
     return;
   LOG_V(severity) << prefix << "(";
   for (size_t i=0; i<sbd->cBuffers; ++i) {
     DescribeBuffer(severity, "  ", sbd->pBuffers[i]);
   }
   LOG_V(severity) << ")";
 }

 const ULONG SSL_FLAGS_DEFAULT = ISC_REQ_ALLOCATE_MEMORY
                               | ISC_REQ_CONFIDENTIALITY
                               | ISC_REQ_EXTENDED_ERROR
                               | ISC_REQ_INTEGRITY
                               | ISC_REQ_REPLAY_DETECT
                               | ISC_REQ_SEQUENCE_DETECT
                               | ISC_REQ_STREAM;
                               //| ISC_REQ_USE_SUPPLIED_CREDS;

 typedef std::vector<char> SChannelBuffer;

 struct SChannelAdapter::SSLImpl {
   CredHandle cred;
   CtxtHandle ctx;
   bool cred_init, ctx_init;
   SChannelBuffer inbuf, outbuf, readable;
   SecPkgContext_StreamSizes sizes;

   SSLImpl() : cred_init(false), ctx_init(false) { }
 };

 SChannelAdapter::SChannelAdapter(AsyncSocket* socket)
   : SSLAdapter(socket), state_(SSL_NONE),
     restartable_(false), signal_close_(false), message_pending_(false),
     impl_(new SSLImpl) {
 }

 SChannelAdapter::~SChannelAdapter() {
   Cleanup();
 }

 int
 SChannelAdapter::StartSSL(const char* hostname, bool restartable) {
   if (state_ != SSL_NONE)
     return ERROR_ALREADY_INITIALIZED;

   ssl_host_name_ = hostname;
   restartable_ = restartable;

   if (socket_->GetState() != Socket::CS_CONNECTED) {
     state_ = SSL_WAIT;
     return 0;
   }

   state_ = SSL_CONNECTING;
   if (int err = BeginSSL()) {
     Error("BeginSSL", err, false);
     return err;
   }

   return 0;
 }

 int
 SChannelAdapter::BeginSSL() {
   LOG(LS_VERBOSE) << "BeginSSL: " << ssl_host_name_;
   ASSERT(state_ == SSL_CONNECTING);

   SECURITY_STATUS ret;

   SCHANNEL_CRED sc_cred = { 0 };
   sc_cred.dwVersion = SCHANNEL_CRED_VERSION;
   //sc_cred.dwMinimumCipherStrength = 128; // Note: use system default
   sc_cred.dwFlags = SCH_CRED_NO_DEFAULT_CREDS | SCH_CRED_AUTO_CRED_VALIDATION;

   ret = AcquireCredentialsHandle(NULL, UNISP_NAME, SECPKG_CRED_OUTBOUND, NULL,
                                  &sc_cred, NULL, NULL, &impl_->cred, NULL);
   if (ret != SEC_E_OK) {
     LOG(LS_ERROR) << "AcquireCredentialsHandle error: "
                   << ErrorName(ret, SECURITY_ERRORS);
     return ret;
   }
   impl_->cred_init = true;

   if (LOG_CHECK_LEVEL(LS_VERBOSE)) {
     SecPkgCred_CipherStrengths cipher_strengths = { 0 };
     ret = QueryCredentialsAttributes(&impl_->cred,
                                      SECPKG_ATTR_CIPHER_STRENGTHS,
                                      &cipher_strengths);
     if (SUCCEEDED(ret)) {
       LOG(LS_VERBOSE) << "SChannel cipher strength: "
                   << cipher_strengths.dwMinimumCipherStrength << " - "
                   << cipher_strengths.dwMaximumCipherStrength;
     }

     SecPkgCred_SupportedAlgs supported_algs = { 0 };
     ret = QueryCredentialsAttributes(&impl_->cred,
                                      SECPKG_ATTR_SUPPORTED_ALGS,
                                      &supported_algs);
     if (SUCCEEDED(ret)) {
       LOG(LS_VERBOSE) << "SChannel supported algorithms:";
       for (DWORD i=0; i<supported_algs.cSupportedAlgs; ++i) {
         ALG_ID alg_id = supported_algs.palgSupportedAlgs[i];
         PCCRYPT_OID_INFO oinfo = CryptFindOIDInfo(CRYPT_OID_INFO_ALGID_KEY,
                                                   &alg_id, 0);
         LPCWSTR alg_name = (NULL != oinfo) ? oinfo->pwszName : L"Unknown";
         LOG(LS_VERBOSE) << "  " << ToUtf8(alg_name) << " (" << alg_id << ")";
       }
       CSecBufferBase::FreeSSPI(supported_algs.palgSupportedAlgs);
     }
   }

   ULONG flags = SSL_FLAGS_DEFAULT, ret_flags = 0;
   if (ignore_bad_cert())
     flags |= ISC_REQ_MANUAL_CRED_VALIDATION;

   CSecBufferBundle<2, CSecBufferBase::FreeSSPI> sb_out;
   ret = InitializeSecurityContextA(&impl_->cred, NULL,
                                    const_cast<char*>(ssl_host_name_.c_str()),
                                    flags, 0, 0, NULL, 0,
                                    &impl_->ctx, sb_out.desc(),
                                    &ret_flags, NULL);
   if (SUCCEEDED(ret))
     impl_->ctx_init = true;
   return ProcessContext(ret, NULL, sb_out.desc());
 }

 int
 SChannelAdapter::ContinueSSL() {
   LOG(LS_VERBOSE) << "ContinueSSL";
   ASSERT(state_ == SSL_CONNECTING);

   SECURITY_STATUS ret;

   CSecBufferBundle<2> sb_in;
   sb_in[0].BufferType = SECBUFFER_TOKEN;
   sb_in[0].cbBuffer = static_cast<unsigned long>(impl_->inbuf.size());
   sb_in[0].pvBuffer = &impl_->inbuf[0];
   //DescribeBuffers(LS_VERBOSE, "Input Buffer ", sb_in.desc());

   ULONG flags = SSL_FLAGS_DEFAULT, ret_flags = 0;
   if (ignore_bad_cert())
     flags |= ISC_REQ_MANUAL_CRED_VALIDATION;

   CSecBufferBundle<2, CSecBufferBase::FreeSSPI> sb_out;
   ret = InitializeSecurityContextA(&impl_->cred, &impl_->ctx,
                                    const_cast<char*>(ssl_host_name_.c_str()),
                                    flags, 0, 0, sb_in.desc(), 0,
                                    NULL, sb_out.desc(),
                                    &ret_flags, NULL);
   return ProcessContext(ret, sb_in.desc(), sb_out.desc());
 }

 int
 SChannelAdapter::ProcessContext(long int status, _SecBufferDesc* sbd_in,
                                 _SecBufferDesc* sbd_out) {
   if (status != SEC_E_OK && status != SEC_I_CONTINUE_NEEDED &&
       status != SEC_E_INCOMPLETE_MESSAGE) {
     LOG(LS_ERROR)
       << "InitializeSecurityContext error: "
       << ErrorName(status, SECURITY_ERRORS);
   }
   //if (sbd_in)
   //  DescribeBuffers(LS_VERBOSE, "Input Buffer ", sbd_in);
   //if (sbd_out)
   //  DescribeBuffers(LS_VERBOSE, "Output Buffer ", sbd_out);

   if (status == SEC_E_INCOMPLETE_MESSAGE) {
     // Wait for more input from server.
     return Flush();
   }

   if (FAILED(status)) {
     // We can't continue.  Common errors:
     // SEC_E_CERT_EXPIRED - Typically, this means the computer clock is wrong.
     return status;
   }

   // Note: we check both input and output buffers for SECBUFFER_EXTRA.
   // Experience shows it appearing in the input, but the documentation claims
   // it should appear in the output.
   size_t extra = 0;
   if (sbd_in) {
     for (size_t i=0; i<sbd_in->cBuffers; ++i) {
       SecBuffer& buffer = sbd_in->pBuffers[i];
       if (buffer.BufferType == SECBUFFER_EXTRA) {
         extra += buffer.cbBuffer;
       }
     }
   }
   if (sbd_out) {
     for (size_t i=0; i<sbd_out->cBuffers; ++i) {
       SecBuffer& buffer = sbd_out->pBuffers[i];
       if (buffer.BufferType == SECBUFFER_EXTRA) {
         extra += buffer.cbBuffer;
       } else if (buffer.BufferType == SECBUFFER_TOKEN) {
         impl_->outbuf.insert(impl_->outbuf.end(),
           reinterpret_cast<char*>(buffer.pvBuffer),
           reinterpret_cast<char*>(buffer.pvBuffer) + buffer.cbBuffer);
       }
     }
   }

   if (extra) {
     ASSERT(extra <= impl_->inbuf.size());
     size_t consumed = impl_->inbuf.size() - extra;
     memmove(&impl_->inbuf[0], &impl_->inbuf[consumed], extra);
     impl_->inbuf.resize(extra);
   } else {
     impl_->inbuf.clear();
   }

   if (SEC_I_CONTINUE_NEEDED == status) {
     // Send data to server and wait for response.
     // Note: ContinueSSL will result in a Flush, anyway.
     return impl_->inbuf.empty() ? Flush() : ContinueSSL();
   }

   if (SEC_E_OK == status) {
     LOG(LS_VERBOSE) << "QueryContextAttributes";
     status = QueryContextAttributes(&impl_->ctx, SECPKG_ATTR_STREAM_SIZES,
                                     &impl_->sizes);
     if (FAILED(status)) {
       LOG(LS_ERROR) << "QueryContextAttributes error: "
                     << ErrorName(status, SECURITY_ERRORS);
       return status;
     }

     state_ = SSL_CONNECTED;

     if (int err = DecryptData()) {
       return err;
     } else if (int err = Flush()) {
       return err;
     } else {
       // If we decrypted any data, queue up a notification here
       PostEvent();
       // Signal our connectedness
       AsyncSocketAdapter::OnConnectEvent(this);
     }
     return 0;
   }

   if (SEC_I_INCOMPLETE_CREDENTIALS == status) {
     // We don't support client authentication in schannel.
     return status;
   }

   // We don't expect any other codes
   ASSERT(false);
   return status;
 }

 int
 SChannelAdapter::DecryptData() {
   SChannelBuffer& inbuf = impl_->inbuf;
   SChannelBuffer& readable = impl_->readable;

   while (!inbuf.empty()) {
     CSecBufferBundle<4> in_buf;
     in_buf[0].BufferType = SECBUFFER_DATA;
     in_buf[0].cbBuffer = static_cast<unsigned long>(inbuf.size());
     in_buf[0].pvBuffer = &inbuf[0];

     //DescribeBuffers(LS_VERBOSE, "Decrypt In ", in_buf.desc());
     SECURITY_STATUS status = DecryptMessage(&impl_->ctx, in_buf.desc(), 0, 0);
     //DescribeBuffers(LS_VERBOSE, "Decrypt Out ", in_buf.desc());

     // Note: We are explicitly treating SEC_E_OK, SEC_I_CONTEXT_EXPIRED, and
     // any other successful results as continue.
     if (SUCCEEDED(status)) {
       size_t data_len = 0, extra_len = 0;
       for (size_t i=0; i<in_buf.desc()->cBuffers; ++i) {
         if (in_buf[i].BufferType == SECBUFFER_DATA) {
           data_len += in_buf[i].cbBuffer;
           readable.insert(readable.end(),
             reinterpret_cast<char*>(in_buf[i].pvBuffer),
             reinterpret_cast<char*>(in_buf[i].pvBuffer) + in_buf[i].cbBuffer);
         } else if (in_buf[i].BufferType == SECBUFFER_EXTRA) {
           extra_len += in_buf[i].cbBuffer;
         }
       }
       // There is a bug on Win2K where SEC_I_CONTEXT_EXPIRED is misclassified.
       if ((data_len == 0) && (inbuf[0] == 0x15)) {
         status = SEC_I_CONTEXT_EXPIRED;
       }
       if (extra_len) {
         size_t consumed = inbuf.size() - extra_len;
         memmove(&inbuf[0], &inbuf[consumed], extra_len);
         inbuf.resize(extra_len);
       } else {
         inbuf.clear();
       }
       // TODO: Handle SEC_I_CONTEXT_EXPIRED to do clean shutdown
       if (status != SEC_E_OK) {
         LOG(LS_INFO) << "DecryptMessage returned continuation code: "
                       << ErrorName(status, SECURITY_ERRORS);
       }
       continue;
     }

     if (status == SEC_E_INCOMPLETE_MESSAGE) {
       break;
     } else {
       return status;
     }
   }

   return 0;
 }

 void
 SChannelAdapter::Cleanup() {
   if (impl_->ctx_init)
     DeleteSecurityContext(&impl_->ctx);
   if (impl_->cred_init)
     FreeCredentialsHandle(&impl_->cred);
   delete impl_;
 }

 void
 SChannelAdapter::PostEvent() {
   // Check if there's anything notable to signal
   if (impl_->readable.empty() && !signal_close_)
     return;

   // Only one post in the queue at a time
   if (message_pending_)
     return;

   if (Thread* thread = Thread::Current()) {
     message_pending_ = true;
     thread->Post(this);
   } else {
     LOG(LS_ERROR) << "No thread context available for SChannelAdapter";
     ASSERT(false);
   }
 }

 void
 SChannelAdapter::Error(const char* context, int err, bool signal) {
   LOG(LS_WARNING) << "SChannelAdapter::Error("
                   << context << ", "
                   << ErrorName(err, SECURITY_ERRORS) << ")";
   state_ = SSL_ERROR;
   SetError(err);
   if (signal)
     AsyncSocketAdapter::OnCloseEvent(this, err);
 }

 int
 SChannelAdapter::Read() {
   char buffer[4096];
   SChannelBuffer& inbuf = impl_->inbuf;
   while (true) {
     int ret = AsyncSocketAdapter::Recv(buffer, sizeof(buffer));
     if (ret > 0) {
       inbuf.insert(inbuf.end(), buffer, buffer + ret);
     } else if (GetError() == EWOULDBLOCK) {
       return 0;  // Blocking
     } else {
       return GetError();
     }
   }
 }

 int
 SChannelAdapter::Flush() {
   int result = 0;
   size_t pos = 0;
   SChannelBuffer& outbuf = impl_->outbuf;
   while (pos < outbuf.size()) {
     int sent = AsyncSocketAdapter::Send(&outbuf[pos], outbuf.size() - pos);
     if (sent > 0) {
       pos += sent;
     } else if (GetError() == EWOULDBLOCK) {
       break;  // Blocking
     } else {
       result = GetError();
       break;
     }
   }
   if (int remainder = static_cast<int>(outbuf.size() - pos)) {
     memmove(&outbuf[0], &outbuf[pos], remainder);
     outbuf.resize(remainder);
   } else {
     outbuf.clear();
   }
   return result;
 }

 //
 // AsyncSocket Implementation
 //

 int
 SChannelAdapter::Send(const void* pv, size_t cb) {
   switch (state_) {
   case SSL_NONE:
     return AsyncSocketAdapter::Send(pv, cb);

   case SSL_WAIT:
   case SSL_CONNECTING:
     SetError(EWOULDBLOCK);
     return SOCKET_ERROR;

   case SSL_CONNECTED:
     break;

   case SSL_ERROR:
   default:
     return SOCKET_ERROR;
   }

   size_t written = 0;
   SChannelBuffer& outbuf = impl_->outbuf;
   while (written < cb) {
     const size_t encrypt_len = std::min<size_t>(cb - written,
                                                 impl_->sizes.cbMaximumMessage);

     CSecBufferBundle<4> out_buf;
     out_buf[0].BufferType = SECBUFFER_STREAM_HEADER;
     out_buf[0].cbBuffer = impl_->sizes.cbHeader;
     out_buf[1].BufferType = SECBUFFER_DATA;
     out_buf[1].cbBuffer = static_cast<unsigned long>(encrypt_len);
     out_buf[2].BufferType = SECBUFFER_STREAM_TRAILER;
     out_buf[2].cbBuffer = impl_->sizes.cbTrailer;

     size_t packet_len = out_buf[0].cbBuffer
                       + out_buf[1].cbBuffer
                       + out_buf[2].cbBuffer;

     SChannelBuffer message;
     message.resize(packet_len);
     out_buf[0].pvBuffer = &message[0];
     out_buf[1].pvBuffer = &message[out_buf[0].cbBuffer];
     out_buf[2].pvBuffer = &message[out_buf[0].cbBuffer + out_buf[1].cbBuffer];

     memcpy(out_buf[1].pvBuffer,
            static_cast<const char*>(pv) + written,
            encrypt_len);

     //DescribeBuffers(LS_VERBOSE, "Encrypt In ", out_buf.desc());
     SECURITY_STATUS res = EncryptMessage(&impl_->ctx, 0, out_buf.desc(), 0);
     //DescribeBuffers(LS_VERBOSE, "Encrypt Out ", out_buf.desc());

     if (FAILED(res)) {
       Error("EncryptMessage", res, false);
       return SOCKET_ERROR;
     }

     // We assume that the header and data segments do not change length,
     // or else encrypting the concatenated packet in-place is wrong.
     ASSERT(out_buf[0].cbBuffer == impl_->sizes.cbHeader);
     ASSERT(out_buf[1].cbBuffer == static_cast<unsigned long>(encrypt_len));

     // However, the length of the trailer may change due to padding.
     ASSERT(out_buf[2].cbBuffer <= impl_->sizes.cbTrailer);

     packet_len = out_buf[0].cbBuffer
                + out_buf[1].cbBuffer
                + out_buf[2].cbBuffer;

     written += encrypt_len;
     outbuf.insert(outbuf.end(), &message[0], &message[packet_len-1]+1);
   }

   if (int err = Flush()) {
     state_ = SSL_ERROR;
     SetError(err);
     return SOCKET_ERROR;
   }

   return static_cast<int>(written);
 }

 int
 SChannelAdapter::Recv(void* pv, size_t cb) {
   switch (state_) {
   case SSL_NONE:
     return AsyncSocketAdapter::Recv(pv, cb);

   case SSL_WAIT:
   case SSL_CONNECTING:
     SetError(EWOULDBLOCK);
     return SOCKET_ERROR;

   case SSL_CONNECTED:
     break;

   case SSL_ERROR:
   default:
     return SOCKET_ERROR;
   }

   SChannelBuffer& readable = impl_->readable;
   if (readable.empty()) {
     SetError(EWOULDBLOCK);
     return SOCKET_ERROR;
   }
   size_t read = _min(cb, readable.size());
   memcpy(pv, &readable[0], read);
   if (size_t remaining = readable.size() - read) {
     memmove(&readable[0], &readable[read], remaining);
     readable.resize(remaining);
   } else {
     readable.clear();
   }

   PostEvent();
   return static_cast<int>(read);
 }

 int
 SChannelAdapter::Close() {
   if (!impl_->readable.empty()) {
     LOG(WARNING) << "SChannelAdapter::Close with readable data";
     // Note: this isn't strictly an error, but we're using it temporarily to
     // track bugs.
     //ASSERT(false);
   }
   if (state_ == SSL_CONNECTED) {
     DWORD token = SCHANNEL_SHUTDOWN;
     CSecBufferBundle<1> sb_in;
     sb_in[0].BufferType = SECBUFFER_TOKEN;
     sb_in[0].cbBuffer = sizeof(token);
     sb_in[0].pvBuffer = &token;
     ApplyControlToken(&impl_->ctx, sb_in.desc());
     // TODO: In theory, to do a nice shutdown, we need to begin shutdown
     // negotiation with more calls to InitializeSecurityContext.  Since the
     // socket api doesn't support nice shutdown at this point, we don't bother.
   }
   Cleanup();
   impl_ = new SSLImpl;
   state_ = restartable_ ? SSL_WAIT : SSL_NONE;
   signal_close_ = false;
   message_pending_ = false;
   return AsyncSocketAdapter::Close();
 }

 Socket::ConnState
 SChannelAdapter::GetState() const {
   if (signal_close_)
     return CS_CONNECTED;
   ConnState state = socket_->GetState();
   if ((state == CS_CONNECTED)
       && ((state_ == SSL_WAIT) || (state_ == SSL_CONNECTING)))
     state = CS_CONNECTING;
   return state;
 }

 void
 SChannelAdapter::OnConnectEvent(AsyncSocket* socket) {
   LOG(LS_VERBOSE) << "SChannelAdapter::OnConnectEvent";
   if (state_ != SSL_WAIT) {
     ASSERT(state_ == SSL_NONE);
     AsyncSocketAdapter::OnConnectEvent(socket);
     return;
   }

   state_ = SSL_CONNECTING;
   if (int err = BeginSSL()) {
     Error("BeginSSL", err);
   }
 }

 void
 SChannelAdapter::OnReadEvent(AsyncSocket* socket) {
   if (state_ == SSL_NONE) {
     AsyncSocketAdapter::OnReadEvent(socket);
     return;
   }

   if (int err = Read()) {
     Error("Read", err);
     return;
   }

   if (impl_->inbuf.empty())
     return;

   if (state_ == SSL_CONNECTED) {
     if (int err = DecryptData()) {
       Error("DecryptData", err);
     } else if (!impl_->readable.empty()) {
       AsyncSocketAdapter::OnReadEvent(this);
     }
   } else if (state_ == SSL_CONNECTING) {
     if (int err = ContinueSSL()) {
       Error("ContinueSSL", err);
     }
   }
 }

 void
 SChannelAdapter::OnWriteEvent(AsyncSocket* socket) {
   if (state_ == SSL_NONE) {
     AsyncSocketAdapter::OnWriteEvent(socket);
     return;
   }

   if (int err = Flush()) {
     Error("Flush", err);
     return;
   }

   // See if we have more data to write
   if (!impl_->outbuf.empty())
     return;

   // Buffer is empty, submit notification
   if (state_ == SSL_CONNECTED) {
     AsyncSocketAdapter::OnWriteEvent(socket);
   }
 }

 void
 SChannelAdapter::OnCloseEvent(AsyncSocket* socket, int err) {
   if ((state_ == SSL_NONE) || impl_->readable.empty()) {
     AsyncSocketAdapter::OnCloseEvent(socket, err);
     return;
   }

   // If readable is non-empty, then we have a pending Message
   // that will allow us to signal close (eventually).
   signal_close_ = true;
 }

 void
 SChannelAdapter::OnMessage(Message* pmsg) {
   if (!message_pending_)
     return;  // This occurs when socket is closed

   message_pending_ = false;
   if (!impl_->readable.empty()) {
     AsyncSocketAdapter::OnReadEvent(this);
   } else if (signal_close_) {
     signal_close_ = false;
     AsyncSocketAdapter::OnCloseEvent(this, 0); // TODO: cache this error?
   }
 }

 } // namespace rtc
	/*
	* Copyright 2004 The WebRTC Project Authors. All rights reserved.
	*
	* Use of this source code is governed by a BSD-style license
	* that can be found in the LICENSE file in the root of the source
	* tree. An additional intellectual property rights grant can be found
	* in the file PATENTS. All contributing project authors may
	* be found in the AUTHORS file in the root of the source tree.
	*/

	#include "webrtc/base/win32.h"
	#define SECURITY_WIN32
	#include <security.h>
	#include <schannel.h>

	#include <iomanip>
	#include <vector>

	#include "webrtc/base/common.h"
	#include "webrtc/base/logging.h"
	#include "webrtc/base/schanneladapter.h"
	#include "webrtc/base/sec_buffer.h"
	#include "webrtc/base/thread.h"

	namespace rtc {

	/////////////////////////////////////////////////////////////////////////////
	// SChannelAdapter
	/////////////////////////////////////////////////////////////////////////////

	extern const ConstantLabel SECURITY_ERRORS[];

	const ConstantLabel SCHANNEL_BUFFER_TYPES[] = {
	KLABEL(SECBUFFER_EMPTY), // 0
	KLABEL(SECBUFFER_DATA), // 1
	KLABEL(SECBUFFER_TOKEN), // 2
	KLABEL(SECBUFFER_PKG_PARAMS), // 3
	KLABEL(SECBUFFER_MISSING), // 4
	KLABEL(SECBUFFER_EXTRA), // 5
	KLABEL(SECBUFFER_STREAM_TRAILER), // 6
	KLABEL(SECBUFFER_STREAM_HEADER), // 7
	KLABEL(SECBUFFER_MECHLIST), // 11
	KLABEL(SECBUFFER_MECHLIST_SIGNATURE), // 12
	KLABEL(SECBUFFER_TARGET), // 13
	KLABEL(SECBUFFER_CHANNEL_BINDINGS), // 14
	LASTLABEL
	};

	void DescribeBuffer(LoggingSeverity severity, const char* prefix,
	const SecBuffer& sb) {
	LOG_V(severity)
	<< prefix
	<< "(" << sb.cbBuffer
	<< ", " << FindLabel(sb.BufferType & ~SECBUFFER_ATTRMASK,
	SCHANNEL_BUFFER_TYPES)
	<< ", " << sb.pvBuffer << ")";
	}

	void DescribeBuffers(LoggingSeverity severity, const char* prefix,
	const SecBufferDesc* sbd) {
	if (!LOG_CHECK_LEVEL_V(severity))
	return;
	LOG_V(severity) << prefix << "(";
	for (size_t i=0; i<sbd->cBuffers; ++i) {
	DescribeBuffer(severity, " ", sbd->pBuffers[i]);
	}
	LOG_V(severity) << ")";
	}

	const ULONG SSL_FLAGS_DEFAULT = ISC_REQ_ALLOCATE_MEMORY
	\| ISC_REQ_CONFIDENTIALITY
	\| ISC_REQ_EXTENDED_ERROR
	\| ISC_REQ_INTEGRITY
	\| ISC_REQ_REPLAY_DETECT
	\| ISC_REQ_SEQUENCE_DETECT
	\| ISC_REQ_STREAM;
	//\| ISC_REQ_USE_SUPPLIED_CREDS;

	typedef std::vector<char> SChannelBuffer;

	struct SChannelAdapter::SSLImpl {
	CredHandle cred;
	CtxtHandle ctx;
	bool cred_init, ctx_init;
	SChannelBuffer inbuf, outbuf, readable;
	SecPkgContext_StreamSizes sizes;

	SSLImpl() : cred_init(false), ctx_init(false) { }
	};

	SChannelAdapter::SChannelAdapter(AsyncSocket* socket)
	: SSLAdapter(socket), state_(SSL_NONE),
	restartable_(false), signal_close_(false), message_pending_(false),
	impl_(new SSLImpl) {
	}

	SChannelAdapter::~SChannelAdapter() {
	Cleanup();
	}

	int
	SChannelAdapter::StartSSL(const char* hostname, bool restartable) {
	if (state_ != SSL_NONE)
	return ERROR_ALREADY_INITIALIZED;

	ssl_host_name_ = hostname;
	restartable_ = restartable;

	if (socket_->GetState() != Socket::CS_CONNECTED) {
	state_ = SSL_WAIT;
	return 0;
	}

	state_ = SSL_CONNECTING;
	if (int err = BeginSSL()) {
	Error("BeginSSL", err, false);
	return err;
	}

	return 0;
	}

	int
	SChannelAdapter::BeginSSL() {
	LOG(LS_VERBOSE) << "BeginSSL: " << ssl_host_name_;
	ASSERT(state_ == SSL_CONNECTING);

	SECURITY_STATUS ret;

	SCHANNEL_CRED sc_cred = { 0 };
	sc_cred.dwVersion = SCHANNEL_CRED_VERSION;
	//sc_cred.dwMinimumCipherStrength = 128; // Note: use system default
	sc_cred.dwFlags = SCH_CRED_NO_DEFAULT_CREDS \| SCH_CRED_AUTO_CRED_VALIDATION;

	ret = AcquireCredentialsHandle(NULL, UNISP_NAME, SECPKG_CRED_OUTBOUND, NULL,
	&sc_cred, NULL, NULL, &impl_->cred, NULL);
	if (ret != SEC_E_OK) {
	LOG(LS_ERROR) << "AcquireCredentialsHandle error: "
	<< ErrorName(ret, SECURITY_ERRORS);
	return ret;
	}
	impl_->cred_init = true;

	if (LOG_CHECK_LEVEL(LS_VERBOSE)) {
	SecPkgCred_CipherStrengths cipher_strengths = { 0 };
	ret = QueryCredentialsAttributes(&impl_->cred,
	SECPKG_ATTR_CIPHER_STRENGTHS,
	&cipher_strengths);
	if (SUCCEEDED(ret)) {
	LOG(LS_VERBOSE) << "SChannel cipher strength: "
	<< cipher_strengths.dwMinimumCipherStrength << " - "
	<< cipher_strengths.dwMaximumCipherStrength;
	}

	SecPkgCred_SupportedAlgs supported_algs = { 0 };
	ret = QueryCredentialsAttributes(&impl_->cred,
	SECPKG_ATTR_SUPPORTED_ALGS,
	&supported_algs);
	if (SUCCEEDED(ret)) {
	LOG(LS_VERBOSE) << "SChannel supported algorithms:";
	for (DWORD i=0; i<supported_algs.cSupportedAlgs; ++i) {
	ALG_ID alg_id = supported_algs.palgSupportedAlgs[i];
	PCCRYPT_OID_INFO oinfo = CryptFindOIDInfo(CRYPT_OID_INFO_ALGID_KEY,
	&alg_id, 0);
	LPCWSTR alg_name = (NULL != oinfo) ? oinfo->pwszName : L"Unknown";
	LOG(LS_VERBOSE) << " " << ToUtf8(alg_name) << " (" << alg_id << ")";
	}
	CSecBufferBase::FreeSSPI(supported_algs.palgSupportedAlgs);
	}
	}

	ULONG flags = SSL_FLAGS_DEFAULT, ret_flags = 0;
	if (ignore_bad_cert())
	flags \|= ISC_REQ_MANUAL_CRED_VALIDATION;

	CSecBufferBundle<2, CSecBufferBase::FreeSSPI> sb_out;
	ret = InitializeSecurityContextA(&impl_->cred, NULL,
	const_cast<char*>(ssl_host_name_.c_str()),
	flags, 0, 0, NULL, 0,
	&impl_->ctx, sb_out.desc(),
	&ret_flags, NULL);
	if (SUCCEEDED(ret))
	impl_->ctx_init = true;
	return ProcessContext(ret, NULL, sb_out.desc());
	}

	int
	SChannelAdapter::ContinueSSL() {
	LOG(LS_VERBOSE) << "ContinueSSL";
	ASSERT(state_ == SSL_CONNECTING);

	SECURITY_STATUS ret;

	CSecBufferBundle<2> sb_in;
	sb_in[0].BufferType = SECBUFFER_TOKEN;
	sb_in[0].cbBuffer = static_cast<unsigned long>(impl_->inbuf.size());
	sb_in[0].pvBuffer = &impl_->inbuf[0];
	//DescribeBuffers(LS_VERBOSE, "Input Buffer ", sb_in.desc());

	ULONG flags = SSL_FLAGS_DEFAULT, ret_flags = 0;
	if (ignore_bad_cert())
	flags \|= ISC_REQ_MANUAL_CRED_VALIDATION;

	CSecBufferBundle<2, CSecBufferBase::FreeSSPI> sb_out;
	ret = InitializeSecurityContextA(&impl_->cred, &impl_->ctx,
	const_cast<char*>(ssl_host_name_.c_str()),
	flags, 0, 0, sb_in.desc(), 0,
	NULL, sb_out.desc(),
	&ret_flags, NULL);
	return ProcessContext(ret, sb_in.desc(), sb_out.desc());
	}

	int
	SChannelAdapter::ProcessContext(long int status, _SecBufferDesc* sbd_in,
	_SecBufferDesc* sbd_out) {
	if (status != SEC_E_OK && status != SEC_I_CONTINUE_NEEDED &&
	status != SEC_E_INCOMPLETE_MESSAGE) {
	LOG(LS_ERROR)
	<< "InitializeSecurityContext error: "
	<< ErrorName(status, SECURITY_ERRORS);
	}
	//if (sbd_in)
	// DescribeBuffers(LS_VERBOSE, "Input Buffer ", sbd_in);
	//if (sbd_out)
	// DescribeBuffers(LS_VERBOSE, "Output Buffer ", sbd_out);

	if (status == SEC_E_INCOMPLETE_MESSAGE) {
	// Wait for more input from server.
	return Flush();
	}

	if (FAILED(status)) {
	// We can't continue. Common errors:
	// SEC_E_CERT_EXPIRED - Typically, this means the computer clock is wrong.
	return status;
	}

	// Note: we check both input and output buffers for SECBUFFER_EXTRA.
	// Experience shows it appearing in the input, but the documentation claims
	// it should appear in the output.
	size_t extra = 0;
	if (sbd_in) {
	for (size_t i=0; i<sbd_in->cBuffers; ++i) {
	SecBuffer& buffer = sbd_in->pBuffers[i];
	if (buffer.BufferType == SECBUFFER_EXTRA) {
	extra += buffer.cbBuffer;
	}
	}
	}
	if (sbd_out) {
	for (size_t i=0; i<sbd_out->cBuffers; ++i) {
	SecBuffer& buffer = sbd_out->pBuffers[i];
	if (buffer.BufferType == SECBUFFER_EXTRA) {
	extra += buffer.cbBuffer;
	} else if (buffer.BufferType == SECBUFFER_TOKEN) {
	impl_->outbuf.insert(impl_->outbuf.end(),
	reinterpret_cast<char*>(buffer.pvBuffer),
	reinterpret_cast<char*>(buffer.pvBuffer) + buffer.cbBuffer);
	}
	}
	}

	if (extra) {
	ASSERT(extra <= impl_->inbuf.size());
	size_t consumed = impl_->inbuf.size() - extra;
	memmove(&impl_->inbuf[0], &impl_->inbuf[consumed], extra);
	impl_->inbuf.resize(extra);
	} else {
	impl_->inbuf.clear();
	}

	if (SEC_I_CONTINUE_NEEDED == status) {
	// Send data to server and wait for response.
	// Note: ContinueSSL will result in a Flush, anyway.
	return impl_->inbuf.empty() ? Flush() : ContinueSSL();
	}

	if (SEC_E_OK == status) {
	LOG(LS_VERBOSE) << "QueryContextAttributes";
	status = QueryContextAttributes(&impl_->ctx, SECPKG_ATTR_STREAM_SIZES,
	&impl_->sizes);
	if (FAILED(status)) {
	LOG(LS_ERROR) << "QueryContextAttributes error: "
	<< ErrorName(status, SECURITY_ERRORS);
	return status;
	}

	state_ = SSL_CONNECTED;

	if (int err = DecryptData()) {
	return err;
	} else if (int err = Flush()) {
	return err;
	} else {
	// If we decrypted any data, queue up a notification here
	PostEvent();
	// Signal our connectedness
	AsyncSocketAdapter::OnConnectEvent(this);
	}
	return 0;
	}

	if (SEC_I_INCOMPLETE_CREDENTIALS == status) {
	// We don't support client authentication in schannel.
	return status;
	}

	// We don't expect any other codes
	ASSERT(false);
	return status;
	}

	int
	SChannelAdapter::DecryptData() {
	SChannelBuffer& inbuf = impl_->inbuf;
	SChannelBuffer& readable = impl_->readable;

	while (!inbuf.empty()) {
	CSecBufferBundle<4> in_buf;
	in_buf[0].BufferType = SECBUFFER_DATA;
	in_buf[0].cbBuffer = static_cast<unsigned long>(inbuf.size());
	in_buf[0].pvBuffer = &inbuf[0];

	//DescribeBuffers(LS_VERBOSE, "Decrypt In ", in_buf.desc());
	SECURITY_STATUS status = DecryptMessage(&impl_->ctx, in_buf.desc(), 0, 0);
	//DescribeBuffers(LS_VERBOSE, "Decrypt Out ", in_buf.desc());

	// Note: We are explicitly treating SEC_E_OK, SEC_I_CONTEXT_EXPIRED, and
	// any other successful results as continue.
	if (SUCCEEDED(status)) {
	size_t data_len = 0, extra_len = 0;
	for (size_t i=0; i<in_buf.desc()->cBuffers; ++i) {
	if (in_buf[i].BufferType == SECBUFFER_DATA) {
	data_len += in_buf[i].cbBuffer;
	readable.insert(readable.end(),
	reinterpret_cast<char*>(in_buf[i].pvBuffer),
	reinterpret_cast<char*>(in_buf[i].pvBuffer) + in_buf[i].cbBuffer);
	} else if (in_buf[i].BufferType == SECBUFFER_EXTRA) {
	extra_len += in_buf[i].cbBuffer;
	}
	}
	// There is a bug on Win2K where SEC_I_CONTEXT_EXPIRED is misclassified.
	if ((data_len == 0) && (inbuf[0] == 0x15)) {
	status = SEC_I_CONTEXT_EXPIRED;
	}
	if (extra_len) {
	size_t consumed = inbuf.size() - extra_len;
	memmove(&inbuf[0], &inbuf[consumed], extra_len);
	inbuf.resize(extra_len);
	} else {
	inbuf.clear();
	}
	// TODO: Handle SEC_I_CONTEXT_EXPIRED to do clean shutdown
	if (status != SEC_E_OK) {
	LOG(LS_INFO) << "DecryptMessage returned continuation code: "
	<< ErrorName(status, SECURITY_ERRORS);
	}
	continue;
	}

	if (status == SEC_E_INCOMPLETE_MESSAGE) {
	break;
	} else {
	return status;
	}
	}

	return 0;
	}

	void
	SChannelAdapter::Cleanup() {
	if (impl_->ctx_init)
	DeleteSecurityContext(&impl_->ctx);
	if (impl_->cred_init)
	FreeCredentialsHandle(&impl_->cred);
	delete impl_;
	}

	void
	SChannelAdapter::PostEvent() {
	// Check if there's anything notable to signal
	if (impl_->readable.empty() && !signal_close_)
	return;

	// Only one post in the queue at a time
	if (message_pending_)
	return;

	if (Thread* thread = Thread::Current()) {
	message_pending_ = true;
	thread->Post(this);
	} else {
	LOG(LS_ERROR) << "No thread context available for SChannelAdapter";
	ASSERT(false);
	}
	}

	void
	SChannelAdapter::Error(const char* context, int err, bool signal) {
	LOG(LS_WARNING) << "SChannelAdapter::Error("
	<< context << ", "
	<< ErrorName(err, SECURITY_ERRORS) << ")";
	state_ = SSL_ERROR;
	SetError(err);
	if (signal)
	AsyncSocketAdapter::OnCloseEvent(this, err);
	}

	int
	SChannelAdapter::Read() {
	char buffer[4096];
	SChannelBuffer& inbuf = impl_->inbuf;
	while (true) {
	int ret = AsyncSocketAdapter::Recv(buffer, sizeof(buffer));
	if (ret > 0) {
	inbuf.insert(inbuf.end(), buffer, buffer + ret);
	} else if (GetError() == EWOULDBLOCK) {
	return 0; // Blocking
	} else {
	return GetError();
	}
	}
	}

	int
	SChannelAdapter::Flush() {
	int result = 0;
	size_t pos = 0;
	SChannelBuffer& outbuf = impl_->outbuf;
	while (pos < outbuf.size()) {
	int sent = AsyncSocketAdapter::Send(&outbuf[pos], outbuf.size() - pos);
	if (sent > 0) {
	pos += sent;
	} else if (GetError() == EWOULDBLOCK) {
	break; // Blocking
	} else {
	result = GetError();
	break;
	}
	}
	if (int remainder = static_cast<int>(outbuf.size() - pos)) {
	memmove(&outbuf[0], &outbuf[pos], remainder);
	outbuf.resize(remainder);
	} else {
	outbuf.clear();
	}
	return result;
	}

	//
	// AsyncSocket Implementation
	//

	int
	SChannelAdapter::Send(const void* pv, size_t cb) {
	switch (state_) {
	case SSL_NONE:
	return AsyncSocketAdapter::Send(pv, cb);

	case SSL_WAIT:
	case SSL_CONNECTING:
	SetError(EWOULDBLOCK);
	return SOCKET_ERROR;

	case SSL_CONNECTED:
	break;

	case SSL_ERROR:
	default:
	return SOCKET_ERROR;
	}

	size_t written = 0;
	SChannelBuffer& outbuf = impl_->outbuf;
	while (written < cb) {
	const size_t encrypt_len = std::min<size_t>(cb - written,
	impl_->sizes.cbMaximumMessage);

	CSecBufferBundle<4> out_buf;
	out_buf[0].BufferType = SECBUFFER_STREAM_HEADER;
	out_buf[0].cbBuffer = impl_->sizes.cbHeader;
	out_buf[1].BufferType = SECBUFFER_DATA;
	out_buf[1].cbBuffer = static_cast<unsigned long>(encrypt_len);
	out_buf[2].BufferType = SECBUFFER_STREAM_TRAILER;
	out_buf[2].cbBuffer = impl_->sizes.cbTrailer;

	size_t packet_len = out_buf[0].cbBuffer
	+ out_buf[1].cbBuffer
	+ out_buf[2].cbBuffer;

	SChannelBuffer message;
	message.resize(packet_len);
	out_buf[0].pvBuffer = &message[0];
	out_buf[1].pvBuffer = &message[out_buf[0].cbBuffer];
	out_buf[2].pvBuffer = &message[out_buf[0].cbBuffer + out_buf[1].cbBuffer];

	memcpy(out_buf[1].pvBuffer,
	static_cast<const char*>(pv) + written,
	encrypt_len);

	//DescribeBuffers(LS_VERBOSE, "Encrypt In ", out_buf.desc());
	SECURITY_STATUS res = EncryptMessage(&impl_->ctx, 0, out_buf.desc(), 0);
	//DescribeBuffers(LS_VERBOSE, "Encrypt Out ", out_buf.desc());

	if (FAILED(res)) {
	Error("EncryptMessage", res, false);
	return SOCKET_ERROR;
	}

	// We assume that the header and data segments do not change length,
	// or else encrypting the concatenated packet in-place is wrong.
	ASSERT(out_buf[0].cbBuffer == impl_->sizes.cbHeader);
	ASSERT(out_buf[1].cbBuffer == static_cast<unsigned long>(encrypt_len));

	// However, the length of the trailer may change due to padding.
	ASSERT(out_buf[2].cbBuffer <= impl_->sizes.cbTrailer);

	packet_len = out_buf[0].cbBuffer
	+ out_buf[1].cbBuffer
	+ out_buf[2].cbBuffer;

	written += encrypt_len;
	outbuf.insert(outbuf.end(), &message[0], &message[packet_len-1]+1);
	}

	if (int err = Flush()) {
	state_ = SSL_ERROR;
	SetError(err);
	return SOCKET_ERROR;
	}

	return static_cast<int>(written);
	}

	int
	SChannelAdapter::Recv(void* pv, size_t cb) {
	switch (state_) {
	case SSL_NONE:
	return AsyncSocketAdapter::Recv(pv, cb);

	case SSL_WAIT:
	case SSL_CONNECTING:
	SetError(EWOULDBLOCK);
	return SOCKET_ERROR;

	case SSL_CONNECTED:
	break;

	case SSL_ERROR:
	default:
	return SOCKET_ERROR;
	}

	SChannelBuffer& readable = impl_->readable;
	if (readable.empty()) {
	SetError(EWOULDBLOCK);
	return SOCKET_ERROR;
	}
	size_t read = _min(cb, readable.size());
	memcpy(pv, &readable[0], read);
	if (size_t remaining = readable.size() - read) {
	memmove(&readable[0], &readable[read], remaining);
	readable.resize(remaining);
	} else {
	readable.clear();
	}

	PostEvent();
	return static_cast<int>(read);
	}

	int
	SChannelAdapter::Close() {
	if (!impl_->readable.empty()) {
	LOG(WARNING) << "SChannelAdapter::Close with readable data";
	// Note: this isn't strictly an error, but we're using it temporarily to
	// track bugs.
	//ASSERT(false);
	}
	if (state_ == SSL_CONNECTED) {
	DWORD token = SCHANNEL_SHUTDOWN;
	CSecBufferBundle<1> sb_in;
	sb_in[0].BufferType = SECBUFFER_TOKEN;
	sb_in[0].cbBuffer = sizeof(token);
	sb_in[0].pvBuffer = &token;
	ApplyControlToken(&impl_->ctx, sb_in.desc());
	// TODO: In theory, to do a nice shutdown, we need to begin shutdown
	// negotiation with more calls to InitializeSecurityContext. Since the
	// socket api doesn't support nice shutdown at this point, we don't bother.
	}
	Cleanup();
	impl_ = new SSLImpl;
	state_ = restartable_ ? SSL_WAIT : SSL_NONE;
	signal_close_ = false;
	message_pending_ = false;
	return AsyncSocketAdapter::Close();
	}

	Socket::ConnState
	SChannelAdapter::GetState() const {
	if (signal_close_)
	return CS_CONNECTED;
	ConnState state = socket_->GetState();
	if ((state == CS_CONNECTED)
	&& ((state_ == SSL_WAIT) \|\| (state_ == SSL_CONNECTING)))
	state = CS_CONNECTING;
	return state;
	}

	void
	SChannelAdapter::OnConnectEvent(AsyncSocket* socket) {
	LOG(LS_VERBOSE) << "SChannelAdapter::OnConnectEvent";
	if (state_ != SSL_WAIT) {
	ASSERT(state_ == SSL_NONE);
	AsyncSocketAdapter::OnConnectEvent(socket);
	return;
	}

	state_ = SSL_CONNECTING;
	if (int err = BeginSSL()) {
	Error("BeginSSL", err);
	}
	}

	void
	SChannelAdapter::OnReadEvent(AsyncSocket* socket) {
	if (state_ == SSL_NONE) {
	AsyncSocketAdapter::OnReadEvent(socket);
	return;
	}

	if (int err = Read()) {
	Error("Read", err);
	return;
	}

	if (impl_->inbuf.empty())
	return;

	if (state_ == SSL_CONNECTED) {
	if (int err = DecryptData()) {
	Error("DecryptData", err);
	} else if (!impl_->readable.empty()) {
	AsyncSocketAdapter::OnReadEvent(this);
	}
	} else if (state_ == SSL_CONNECTING) {
	if (int err = ContinueSSL()) {
	Error("ContinueSSL", err);
	}
	}
	}

	void
	SChannelAdapter::OnWriteEvent(AsyncSocket* socket) {
	if (state_ == SSL_NONE) {
	AsyncSocketAdapter::OnWriteEvent(socket);
	return;
	}

	if (int err = Flush()) {
	Error("Flush", err);
	return;
	}

	// See if we have more data to write
	if (!impl_->outbuf.empty())
	return;

	// Buffer is empty, submit notification
	if (state_ == SSL_CONNECTED) {
	AsyncSocketAdapter::OnWriteEvent(socket);
	}
	}

	void
	SChannelAdapter::OnCloseEvent(AsyncSocket* socket, int err) {
	if ((state_ == SSL_NONE) \|\| impl_->readable.empty()) {
	AsyncSocketAdapter::OnCloseEvent(socket, err);
	return;
	}

	// If readable is non-empty, then we have a pending Message
	// that will allow us to signal close (eventually).
	signal_close_ = true;
	}

	void
	SChannelAdapter::OnMessage(Message* pmsg) {
	if (!message_pending_)
	return; // This occurs when socket is closed

	message_pending_ = false;
	if (!impl_->readable.empty()) {
	AsyncSocketAdapter::OnReadEvent(this);
	} else if (signal_close_) {
	signal_close_ = false;
	AsyncSocketAdapter::OnCloseEvent(this, 0); // TODO: cache this error?
	}
	}

	} // namespace rtc