GUACAMOLE-249: Dynamically wrap channel entry points (FreeRDP will refuse to associate the same entry point with multiple channels).

src/protocols/rdp/.gitignore

@@ -4,5 +4,6 @@ _generated_runner.c
 test_rdp
 
 # Autogenerated sources
+_generated_channel_entry_wrappers.c
 _generated_keymaps.c
 

src/protocols/rdp/Makefile.am

@@ -34,6 +34,7 @@ SUBDIRS = . tests
 #
 
 nodist_libguac_client_rdp_la_SOURCES =  \
+    _generated_channel_entry_wrappers.c \
     _generated_keymaps.c
 
 libguac_client_rdp_la_SOURCES =   \
@@ -200,11 +201,16 @@ libguac_client_rdp_la_LIBADD  += @COMMON_SSH_LTLIB@
 endif
 
 #
-# Autogenerate keymaps
+# Autogenerated keymaps and channel wrapper functions
 #
 
-CLEANFILES = _generated_keymaps.c
+CLEANFILES =                            \
-BUILT_SOURCES = _generated_keymaps.c
+    _generated_channel_entry_wrappers.c \
+    _generated_keymaps.c
+
+BUILT_SOURCES =                         \
+    _generated_channel_entry_wrappers.c \
+    _generated_keymaps.c
 
 rdp_keymaps =                   \
     $(srcdir)/keymaps/base.keymap         \
@@ -224,9 +230,13 @@ rdp_keymaps =                   \
     $(srcdir)/keymaps/tr_tr_qwerty.keymap
 
 _generated_keymaps.c: $(rdp_keymaps)
-	$(srcdir)/keymaps/generate.pl $(rdp_keymaps)
+	$(AM_V_GEN) $(srcdir)/keymaps/generate.pl $(rdp_keymaps)
+
+_generated_channel_entry_wrappers.c: $(srcdir)/channels.h $(srcdir)/generate-entry-wrappers.pl
+	$(AM_V_GEN) $(srcdir)/generate-entry-wrappers.pl $(srcdir)/channels.h
 
 EXTRA_DIST =                   \
     $(rdp_keymaps)             \
+    generate-entry-wrappers.pl \
     keymaps/generate.pl
 

src/protocols/rdp/channels.c

@@ -18,12 +18,53 @@
  */
 
 #include "config.h"
+#include "channels.h"
 #include "rdp.h"
 
 #include <freerdp/channels/channels.h>
 #include <freerdp/freerdp.h>
 #include <guacamole/client.h>
 
+int guac_rdp_wrapped_entry_ex_count = 0;
+
+int guac_rdp_wrapped_entry_count = 0;
+
+PVIRTUALCHANNELENTRYEX guac_rdp_wrapped_entry_ex[GUAC_RDP_MAX_CHANNELS] = { NULL };
+
+PVIRTUALCHANNELENTRY guac_rdp_wrapped_entry[GUAC_RDP_MAX_CHANNELS] = { NULL };
+
+PVIRTUALCHANNELENTRYEX guac_rdp_plugin_wrap_entry_ex(PVIRTUALCHANNELENTRYEX entry_ex) {
+
+    /* Do not wrap if there is insufficient space to store the wrapped
+     * function */
+    if (guac_rdp_wrapped_entry_ex_count == GUAC_RDP_MAX_CHANNELS)
+        return entry_ex;
+
+    /* Generate wrapped version of provided entry point */
+    PVIRTUALCHANNELENTRYEX wrapper = guac_rdp_entry_ex_wrappers[guac_rdp_wrapped_entry_ex_count];
+    guac_rdp_wrapped_entry_ex[guac_rdp_wrapped_entry_ex_count] = entry_ex;
+    guac_rdp_wrapped_entry_ex_count++;
+
+    return wrapper;
+
+}
+
+PVIRTUALCHANNELENTRY guac_rdp_plugin_wrap_entry(PVIRTUALCHANNELENTRY entry) {
+
+    /* Do not wrap if there is insufficient space to store the wrapped
+     * function */
+    if (guac_rdp_wrapped_entry_count == GUAC_RDP_MAX_CHANNELS)
+        return entry;
+
+    /* Generate wrapped version of provided entry point */
+    PVIRTUALCHANNELENTRY wrapper = guac_rdp_entry_wrappers[guac_rdp_wrapped_entry_count];
+    guac_rdp_wrapped_entry[guac_rdp_wrapped_entry_count] = entry;
+    guac_rdp_wrapped_entry_count++;
+
+    return wrapper;
+
+}
+
 int guac_freerdp_channels_load_plugin(rdpChannels* channels,
         rdpSettings* settings, const char* name, void* data) {
 
@@ -31,15 +72,19 @@ int guac_freerdp_channels_load_plugin(rdpChannels* channels,
     PVIRTUALCHANNELENTRYEX entry_ex = (PVIRTUALCHANNELENTRYEX) (void*) freerdp_load_channel_addin_entry(name,
             NULL, NULL, FREERDP_ADDIN_CHANNEL_STATIC | FREERDP_ADDIN_CHANNEL_ENTRYEX);
 
-    if (entry_ex != NULL)
+    if (entry_ex != NULL) {
+        entry_ex = guac_rdp_plugin_wrap_entry_ex(entry_ex);
         return freerdp_channels_client_load_ex(channels, settings, entry_ex, data);
+    }
 
     /* Lacking the "ex" entry point, attempt to load using the non-ex version */
     PVIRTUALCHANNELENTRY entry = freerdp_load_channel_addin_entry(name,
             NULL, NULL, FREERDP_ADDIN_CHANNEL_STATIC);
 
-    if (entry != NULL)
+    if (entry != NULL) {
+        entry = guac_rdp_plugin_wrap_entry(entry);
         return freerdp_channels_client_load(channels, settings, entry, data);
+    }
 
     /* The plugin does not exist / cannot be loaded */
     return 1;

src/protocols/rdp/channels.h

@@ -25,6 +25,22 @@
 #include <freerdp/channels/channels.h>
 #include <freerdp/freerdp.h>
 
+/**
+ * The maximum number of static channels supported by Guacamole's RDP support.
+ * This value should be given a value which is at least the value of FreeRDP's
+ * CHANNEL_MAX_COUNT.
+ *
+ * NOTE: The value of this macro must be specified statically (not as a
+ * reference to CHANNEL_MAX_COUNT), as its value is extracted and used by the
+ * entry point wrapper code generator (generate-entry-wrappers.pl).
+ */
+#define GUAC_RDP_MAX_CHANNELS 64
+
+/* Validate GUAC_RDP_MAX_CHANNELS is sane at compile time */
+#if GUAC_RDP_MAX_CHANNELS < CHANNEL_MAX_COUNT
+#error "GUAC_RDP_MAX_CHANNELS must not be less than CHANNEL_MAX_COUNT"
+#endif
+
 /**
  * Loads the FreeRDP plugin having the given name. This function is a drop-in
  * replacement for freerdp_channels_load_plugin() which additionally loads
@@ -105,5 +121,83 @@ int guac_freerdp_channels_load_plugin(rdpChannels* channels,
 void guac_freerdp_dynamic_channel_collection_add(rdpSettings* settings,
         const char* name, ...);
 
+/**
+ * The number of wrapped channel entry points currently stored within
+ * guac_rdp_wrapped_entry_ex.
+ */
+extern int guac_rdp_wrapped_entry_ex_count;
+
+/**
+ * All currently wrapped entry points that use the PVIRTUALCHANNELENTRYEX
+ * variant.
+ */
+extern PVIRTUALCHANNELENTRYEX guac_rdp_wrapped_entry_ex[GUAC_RDP_MAX_CHANNELS];
+
+/**
+ * Lookup table of wrapper functions for PVIRTUALCHANNELENTRYEX entry points.
+ * Each function within this array is generated at compile time by the entry
+ * point wrapper code generator (generate-entry-wrappers.pl) and automatically
+ * invokes the corresponding wrapped entry point stored within
+ * guac_rdp_wrapped_entry_ex.
+ */
+extern PVIRTUALCHANNELENTRYEX guac_rdp_entry_ex_wrappers[GUAC_RDP_MAX_CHANNELS];
+
+/**
+ * Wraps the provided entry point function, returning a different entry point
+ * which simply invokes the original. As long as this function is not invoked
+ * more than GUAC_RDP_MAX_CHANNELS times, each returned entry point will be
+ * unique, even if the provided entry point is not. As FreeRDP will refuse to
+ * load a plugin if its entry point is already loaded, this allows a single
+ * FreeRDP plugin to be loaded multiple times.
+ *
+ * @param entry_ex
+ *     The entry point function to wrap.
+ *
+ * @return
+ *     A wrapped version of the provided entry point, or the unwrapped entry
+ *     point if there is insufficient space remaining within
+ *     guac_rdp_entry_ex_wrappers to wrap the entry point.
+ */
+PVIRTUALCHANNELENTRYEX guac_rdp_plugin_wrap_entry_ex(PVIRTUALCHANNELENTRYEX entry_ex);
+
+/**
+ * The number of wrapped channel entry points currently stored within
+ * guac_rdp_wrapped_entry.
+ */
+extern int guac_rdp_wrapped_entry_count;
+
+/**
+ * All currently wrapped entry points that use the PVIRTUALCHANNELENTRY
+ * variant.
+ */
+extern PVIRTUALCHANNELENTRY guac_rdp_wrapped_entry[GUAC_RDP_MAX_CHANNELS];
+
+/**
+ * Lookup table of wrapper functions for PVIRTUALCHANNELENTRY entry points.
+ * Each function within this array is generated at compile time by the entry
+ * point wrapper code generator (generate-entry-wrappers.pl) and automatically
+ * invokes the corresponding wrapped entry point stored within
+ * guac_rdp_wrapped_entry.
+ */
+extern PVIRTUALCHANNELENTRY guac_rdp_entry_wrappers[GUAC_RDP_MAX_CHANNELS];
+
+/**
+ * Wraps the provided entry point function, returning a different entry point
+ * which simply invokes the original. As long as this function is not invoked
+ * more than GUAC_RDP_MAX_CHANNELS times, each returned entry point will be
+ * unique, even if the provided entry point is not. As FreeRDP will refuse to
+ * load a plugin if its entry point is already loaded, this allows a single
+ * FreeRDP plugin to be loaded multiple times.
+ *
+ * @param entry
+ *     The entry point function to wrap.
+ *
+ * @return
+ *     A wrapped version of the provided entry point, or the unwrapped entry
+ *     point if there is insufficient space remaining within
+ *     guac_rdp_entry_wrappers to wrap the entry point.
+ */
+PVIRTUALCHANNELENTRY guac_rdp_plugin_wrap_entry(PVIRTUALCHANNELENTRY entry);
+
 #endif
 

src/protocols/rdp/generate-entry-wrappers.pl

@@ -0,0 +1,77 @@
+#!/usr/bin/env perl
+#
+# Licensed to the Apache Software Foundation (ASF) under one
+# or more contributor license agreements.  See the NOTICE file
+# distributed with this work for additional information
+# regarding copyright ownership.  The ASF licenses this file
+# to you under the Apache License, Version 2.0 (the
+# "License"); you may not use this file except in compliance
+# with the License.  You may obtain a copy of the License at
+#
+#   http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing,
+# software distributed under the License is distributed on an
+# "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+# KIND, either express or implied.  See the License for the
+# specific language governing permissions and limitations
+# under the License.
+#
+
+#
+# generate-entry-wrappers.pl
+#
+# Generates C source which defines wrapper functions for FreeRDP plugin entry
+# points, allowing multiple instances of the same plugin to be loaded despite
+# otherwise always having the same entry point.
+#
+# The resulting source is stored within "_generated_channel_entry_wrappers.c".
+#
+
+use strict;
+
+##
+## The maximum number of static channels supported by Guacamole's RDP support.
+##
+my $GUAC_RDP_MAX_CHANNELS;
+
+# Extract value of GUAC_RDP_MAX_CHANNELS macro from provided source
+while (<>) {
+    if ((my $value) = m/^\s*#define\s+GUAC_RDP_MAX_CHANNELS\s+(\d+)\s*$/) {
+        $GUAC_RDP_MAX_CHANNELS = $value;
+    }
+}
+
+open OUTPUT, ">", "_generated_channel_entry_wrappers.c";
+
+# Generate required headers
+print OUTPUT <<"EOF";
+#include "channels.h"
+#include <freerdp/channels/channels.h>
+#include <freerdp/freerdp.h>
+EOF
+
+# Generate wrapper definitions for PVIRTUALCHANNELENTRYEX entry point variant
+print OUTPUT <<"EOF" for (1..$GUAC_RDP_MAX_CHANNELS);
+static BOOL guac_rdp_plugin_entry_ex_wrapper$_(PCHANNEL_ENTRY_POINTS_EX entry_points_ex, PVOID init_handle) {
+    return guac_rdp_wrapped_entry_ex[$_ - 1](entry_points_ex, init_handle);
+}
+EOF
+
+# Generate wrapper definitions for PVIRTUALCHANNELENTRY entry point variant
+print OUTPUT <<"EOF" for (1..$GUAC_RDP_MAX_CHANNELS);
+static BOOL guac_rdp_plugin_entry_wrapper$_(PCHANNEL_ENTRY_POINTS entry_points) {
+    return guac_rdp_wrapped_entry[$_ - 1](entry_points);
+}
+EOF
+
+# Populate lookup table of PVIRTUALCHANNELENTRYEX wrapper functions
+print OUTPUT "PVIRTUALCHANNELENTRYEX guac_rdp_entry_ex_wrappers[$GUAC_RDP_MAX_CHANNELS] = {\n";
+print OUTPUT "    guac_rdp_plugin_entry_ex_wrapper$_,\n" for (1..$GUAC_RDP_MAX_CHANNELS);
+print OUTPUT "};\n";
+
+# Populate lookup table of PVIRTUALCHANNELENTRY wrapper functions
+print OUTPUT "PVIRTUALCHANNELENTRY guac_rdp_entry_wrappers[$GUAC_RDP_MAX_CHANNELS] = {\n";
+print OUTPUT "    guac_rdp_plugin_entry_wrapper$_,\n" for (1..$GUAC_RDP_MAX_CHANNELS);
+print OUTPUT "};\n";
+