Add a new utility class Dynamically_Loaded_Library which wraps around

the system dynamic linker (if any). Currently it only supports dlopen,
and is only enabled on Linux. It will almost certainly work on BSDs
and Solaris as well, though, and should be easy to extend to support
Win32-style dynamic loading.

Also add a new engine, Dynamically_Loaded_Engine, which loads up a new
Engine object from a shared library/DLL.

3 files changed, 185 insertions, 0 deletions

diff --git a/src/engine/dyn_engine/dyn_engine.cpp b/src/engine/dyn_engine/dyn_engine.cpp
new file mode 100644
index 000000000..2dc76d7d6
--- /dev/null
+++ b/src/engine/dyn_engine/dyn_engine.cpp
@@ -0,0 +1,67 @@
+/**
+* Dynamically Loaded Engine
+* (C) 2010 Jack Lloyd
+*
+* Distributed under the terms of the Botan license
+*/
+
+#include <botan/dyn_engine.h>
+#include <botan/internal/dyn_load.h>
+
+namespace Botan {
+
+namespace {
+
+extern "C" {
+   typedef Engine* (*creator_function)(void);
+   typedef void (*destructor_function)(Engine*);
+}
+
+}
+
+Dynamically_Loaded_Engine::Dynamically_Loaded_Engine(
+   const std::string& library_path) :
+   engine(0)
+   {
+   lib = new Dynamically_Loaded_Library(library_path);
+
+   try
+      {
+      creator_function creator = lib->resolve<creator_function>("create_engine");
+
+      engine = creator();
+
+      if(!engine)
+         throw std::runtime_error("Creator function in " + library_path + " failed");
+      }
+   catch(...)
+      {
+      delete lib;
+      lib = 0;
+      throw;
+      }
+   }
+
+Dynamically_Loaded_Engine::~Dynamically_Loaded_Engine()
+   {
+   if(lib && engine)
+      {
+      try
+         {
+         destructor_function destroy =
+            lib->resolve<destructor_function>("destroy_engine");
+         destroy(engine);
+         }
+      catch(...)
+         {
+         delete lib;
+         lib = 0;
+         throw;
+         }
+      }
+
+   if(lib)
+      delete lib;
+   }
+
+}
diff --git a/src/engine/dyn_engine/dyn_engine.h b/src/engine/dyn_engine/dyn_engine.h
new file mode 100644
index 000000000..46752f5a9
--- /dev/null
+++ b/src/engine/dyn_engine/dyn_engine.h
@@ -0,0 +1,100 @@
+/**
+* Dynamically Loaded Engine
+* (C) 2010 Jack Lloyd
+*
+* Distributed under the terms of the Botan license
+*/
+
+#include <botan/engine.h>
+
+namespace Botan {
+
+/**
+* Dynamically_Loaded_Engine just proxies the requests to the underlying
+* Engine object, and handles load/unload details
+*/
+class BOTAN_DLL Dynamically_Loaded_Engine : public Engine
+   {
+   public:
+      /**
+      * @param lib_path full pathname to DLL to load
+      */
+      Dynamically_Loaded_Engine(const std::string& lib_path);
+
+      ~Dynamically_Loaded_Engine();
+
+      std::string provider_name() const { return engine->provider_name(); }
+
+      BlockCipher* find_block_cipher(const SCAN_Name& algo_spec,
+                                     Algorithm_Factory& af) const
+         {
+         return engine->find_block_cipher(algo_spec, af);
+         }
+
+      StreamCipher* find_stream_cipher(const SCAN_Name& algo_spec,
+                                       Algorithm_Factory& af) const
+         {
+         return engine->find_stream_cipher(algo_spec, af);
+         }
+
+      HashFunction* find_hash(const SCAN_Name& algo_spec,
+                              Algorithm_Factory& af) const
+         {
+         return engine->find_hash(algo_spec, af);
+         }
+
+      MessageAuthenticationCode* find_mac(const SCAN_Name& algo_spec,
+                                          Algorithm_Factory& af) const
+         {
+         return engine->find_mac(algo_spec, af);
+         }
+
+      Modular_Exponentiator* mod_exp(const BigInt& n,
+                                     Power_Mod::Usage_Hints hints) const
+         {
+         return engine->mod_exp(n, hints);
+         }
+
+      Keyed_Filter* get_cipher(const std::string& algo_spec,
+                               Cipher_Dir dir,
+                               Algorithm_Factory& af)
+         {
+         return engine->get_cipher(algo_spec, dir, af);
+         }
+
+      PK_Ops::Key_Agreement*
+         get_key_agreement_op(const Private_Key& key) const
+         {
+         return engine->get_key_agreement_op(key);
+         }
+
+      PK_Ops::Signature*
+         get_signature_op(const Private_Key& key) const
+         {
+         return engine->get_signature_op(key);
+         }
+
+      PK_Ops::Verification*
+         get_verify_op(const Public_Key& key) const
+         {
+         return engine->get_verify_op(key);
+         }
+
+      PK_Ops::Encryption*
+         get_encryption_op(const Public_Key& key) const
+         {
+         return engine->get_encryption_op(key);
+         }
+
+      PK_Ops::Decryption*
+         get_decryption_op(const Private_Key& key) const
+         {
+         return engine->get_decryption_op(key);
+         }
+
+   private:
+      class Dynamically_Loaded_Library* lib;
+      Engine* engine;
+   };
+
+}
diff --git a/src/engine/dyn_engine/info.txt b/src/engine/dyn_engine/info.txt
new file mode 100644
index 000000000..469583522
--- /dev/null
+++ b/src/engine/dyn_engine/info.txt
@@ -0,0 +1,18 @@
+define DYNAMICALLY_LOADED_ENGINE
+
+<header:public>
+dyn_engine.h
+</header:public>
+
+<source>
+dyn_engine.cpp
+</source>
+
+<requires>
+engine
+dyn_load
+</requires>
+
+<libs>
+linux -> dl
+</libs>