From 1ea0f9f2109c12057c5fddc67ae3929928a3d7b1 Mon Sep 17 00:00:00 2001
From: Pierre Ossman <ossman@cendio.se>
Date: Mon, 4 Jan 2021 13:04:26 +0100
Subject: [PATCH] Handle unsolicited clipboard transfers

The extended clipboard protocol has the ability for the peer to request
things to be sent automatically, without a request message. Make sure we
honor such settings.
---
 common/rfb/CConnection.cxx  | 31 +++++++++++++++++++++++++++----
 common/rfb/CConnection.h    |  1 +
 common/rfb/ClientParams.cxx | 12 ++++++++++++
 common/rfb/ClientParams.h   |  1 +
 common/rfb/SConnection.cxx  | 37 +++++++++++++++++++++++++++++++------
 common/rfb/SConnection.h    |  1 +
 common/rfb/ServerParams.cxx | 12 ++++++++++++
 common/rfb/ServerParams.h   |  1 +
 8 files changed, 86 insertions(+), 10 deletions(-)

diff --git a/common/rfb/CConnection.cxx b/common/rfb/CConnection.cxx
index bdde3253..538d90a8 100644
--- a/common/rfb/CConnection.cxx
+++ b/common/rfb/CConnection.cxx
@@ -578,13 +578,25 @@ void CConnection::requestClipboard()
 void CConnection::announceClipboard(bool available)
 {
   hasLocalClipboard = available;
+  unsolicitedClipboardAttempt = false;
+
+  // Attempt an unsolicited transfer?
+  if (available &&
+      (server.clipboardSize(rfb::clipboardUTF8) > 0) &&
+      (server.clipboardFlags() & rfb::clipboardProvide)) {
+    vlog.debug("Attempting unsolicited clipboard transfer...");
+    unsolicitedClipboardAttempt = true;
+    handleClipboardRequest();
+    return;
+  }
 
-  if (server.clipboardFlags() & rfb::clipboardNotify)
+  if (server.clipboardFlags() & rfb::clipboardNotify) {
     writer()->writeClipboardNotify(available ? rfb::clipboardUTF8 : 0);
-  else {
-    if (available)
-      handleClipboardRequest();
+    return;
   }
+
+  if (available)
+    handleClipboardRequest();
 }
 
 void CConnection::sendClipboardData(const char* data)
@@ -593,6 +605,17 @@ void CConnection::sendClipboardData(const char* data)
     CharArray filtered(convertCRLF(data));
     size_t sizes[1] = { strlen(filtered.buf) + 1 };
     const rdr::U8* data[1] = { (const rdr::U8*)filtered.buf };
+
+    if (unsolicitedClipboardAttempt) {
+      unsolicitedClipboardAttempt = false;
+      if (sizes[0] > server.clipboardSize(rfb::clipboardUTF8)) {
+        vlog.debug("Clipboard was too large for unsolicited clipboard transfer");
+        if (server.clipboardFlags() & rfb::clipboardNotify)
+          writer()->writeClipboardNotify(rfb::clipboardUTF8);
+        return;
+      }
+    }
+
     writer()->writeClipboardProvide(rfb::clipboardUTF8, sizes, data);
   } else {
     CharArray latin1(utf8ToLatin1(data));
diff --git a/common/rfb/CConnection.h b/common/rfb/CConnection.h
index f01d5d36..ca76f530 100644
--- a/common/rfb/CConnection.h
+++ b/common/rfb/CConnection.h
@@ -287,6 +287,7 @@ namespace rfb {
 
     char* serverClipboard;
     bool hasLocalClipboard;
+    bool unsolicitedClipboardAttempt;
   };
 }
 #endif
diff --git a/common/rfb/ClientParams.cxx b/common/rfb/ClientParams.cxx
index 987abe32..6f075a24 100644
--- a/common/rfb/ClientParams.cxx
+++ b/common/rfb/ClientParams.cxx
@@ -143,6 +143,18 @@ void ClientParams::setLEDState(unsigned int state)
   ledState_ = state;
 }
 
+rdr::U32 ClientParams::clipboardSize(unsigned int format) const
+{
+  int i;
+
+  for (i = 0;i < 16;i++) {
+    if (((unsigned)1 << i) == format)
+      return clipSizes[i];
+  }
+
+  throw Exception("Invalid clipboard format 0x%x", format);
+}
+
 void ClientParams::setClipboardCaps(rdr::U32 flags, const rdr::U32* lengths)
 {
   int i, num;
diff --git a/common/rfb/ClientParams.h b/common/rfb/ClientParams.h
index aab3d644..3894ef2d 100644
--- a/common/rfb/ClientParams.h
+++ b/common/rfb/ClientParams.h
@@ -85,6 +85,7 @@ namespace rfb {
     void setLEDState(unsigned int state);
 
     rdr::U32 clipboardFlags() const { return clipFlags; }
+    rdr::U32 clipboardSize(unsigned int format) const;
     void setClipboardCaps(rdr::U32 flags, const rdr::U32* lengths);
 
     // Wrappers to check for functionality rather than specific
diff --git a/common/rfb/SConnection.cxx b/common/rfb/SConnection.cxx
index 4869199a..1b5f513e 100644
--- a/common/rfb/SConnection.cxx
+++ b/common/rfb/SConnection.cxx
@@ -54,7 +54,8 @@ SConnection::SConnection()
     is(0), os(0), reader_(0), writer_(0),
     ssecurity(0), state_(RFBSTATE_UNINITIALISED),
     preferredEncoding(encodingRaw),
-    clientClipboard(NULL), hasLocalClipboard(false)
+    clientClipboard(NULL), hasLocalClipboard(false),
+    unsolicitedClipboardAttempt(false)
 {
   defaultMajorVersion = 3;
   defaultMinorVersion = 8;
@@ -503,14 +504,27 @@ void SConnection::requestClipboard()
 void SConnection::announceClipboard(bool available)
 {
   hasLocalClipboard = available;
+  unsolicitedClipboardAttempt = false;
 
-  if (client.supportsEncoding(pseudoEncodingExtendedClipboard) &&
-      (client.clipboardFlags() & rfb::clipboardNotify))
-    writer()->writeClipboardNotify(available ? rfb::clipboardUTF8 : 0);
-  else {
-    if (available)
+  if (client.supportsEncoding(pseudoEncodingExtendedClipboard)) {
+    // Attempt an unsolicited transfer?
+    if (available &&
+        (client.clipboardSize(rfb::clipboardUTF8) > 0) &&
+        (client.clipboardFlags() & rfb::clipboardProvide)) {
+      vlog.debug("Attempting unsolicited clipboard transfer...");
+      unsolicitedClipboardAttempt = true;
       handleClipboardRequest();
+      return;
+    }
+
+    if (client.clipboardFlags() & rfb::clipboardNotify) {
+      writer()->writeClipboardNotify(available ? rfb::clipboardUTF8 : 0);
+      return;
+    }
   }
+
+  if (available)
+    handleClipboardRequest();
 }
 
 void SConnection::sendClipboardData(const char* data)
@@ -520,6 +534,17 @@ void SConnection::sendClipboardData(const char* data)
     CharArray filtered(convertCRLF(data));
     size_t sizes[1] = { strlen(filtered.buf) + 1 };
     const rdr::U8* data[1] = { (const rdr::U8*)filtered.buf };
+
+    if (unsolicitedClipboardAttempt) {
+      unsolicitedClipboardAttempt = false;
+      if (sizes[0] > client.clipboardSize(rfb::clipboardUTF8)) {
+        vlog.debug("Clipboard was too large for unsolicited clipboard transfer");
+        if (client.clipboardFlags() & rfb::clipboardNotify)
+          writer()->writeClipboardNotify(rfb::clipboardUTF8);
+        return;
+      }
+    }
+
     writer()->writeClipboardProvide(rfb::clipboardUTF8, sizes, data);
   } else {
     CharArray latin1(utf8ToLatin1(data));
diff --git a/common/rfb/SConnection.h b/common/rfb/SConnection.h
index db3ab08c..1119c7c9 100644
--- a/common/rfb/SConnection.h
+++ b/common/rfb/SConnection.h
@@ -255,6 +255,7 @@ namespace rfb {
 
     char* clientClipboard;
     bool hasLocalClipboard;
+    bool unsolicitedClipboardAttempt;
   };
 }
 #endif
diff --git a/common/rfb/ServerParams.cxx b/common/rfb/ServerParams.cxx
index a2e3aa83..a9a96b6e 100644
--- a/common/rfb/ServerParams.cxx
+++ b/common/rfb/ServerParams.cxx
@@ -87,6 +87,18 @@ void ServerParams::setLEDState(unsigned int state)
   ledState_ = state;
 }
 
+rdr::U32 ServerParams::clipboardSize(unsigned int format) const
+{
+  int i;
+
+  for (i = 0;i < 16;i++) {
+    if (((unsigned)1 << i) == format)
+      return clipSizes[i];
+  }
+
+  throw Exception("Invalid clipboard format 0x%x", format);
+}
+
 void ServerParams::setClipboardCaps(rdr::U32 flags, const rdr::U32* lengths)
 {
   int i, num;
diff --git a/common/rfb/ServerParams.h b/common/rfb/ServerParams.h
index c84f6252..ce0c722f 100644
--- a/common/rfb/ServerParams.h
+++ b/common/rfb/ServerParams.h
@@ -70,6 +70,7 @@ namespace rfb {
     void setLEDState(unsigned int state);
 
     rdr::U32 clipboardFlags() const { return clipFlags; }
+    rdr::U32 clipboardSize(unsigned int format) const;
     void setClipboardCaps(rdr::U32 flags, const rdr::U32* lengths);
 
     bool supportsQEMUKeyEvent;
-- 
2.39.5