The Universal Hooker is a tool to intercept execution of programs. It enables the user to intercept calls to API calls inside DLLs, and also arbitrary addresses within the executable file in memory.
Why is it 'Universal'? There are different ways of hooking functions in a program, for example, it can be done by setting software breakpoints (int 3h), hardware breakpoints (cpu regs), or overwriting the prologue of a function to jump to a 'stub', etc. All the methods mentioned required above, specially the latter, require the programmer of the code creating the hook to have certain knowledge of the function it is intercepting. If the code is written in a programming language like C/C++, the code will normally need to be recompiled for every function one wants to intercept, etc.
The Universal Hooker tries to create very simple abstractions that allow a user of the tool to write hooks for different API and non-API functions using an interpreted language (python), without the need to compile anything, and with the possibility of changing the code that gets executed whent the hooked function is called in run-time.
The Universal Hooker builds on the idea that the function handling the hook is the one with the knowledge about the parameters type of the function it is handling. The Universal Hooker only knows the number of parameters of the function, and obtains them from the stack (all DWORDS). The hook handler is the one that will interpret those DWORDS as the types received by the function.
The hook handlers are written in python, what eliminates the need for recompiling the handlers when a modification is required. And also, the hook handlers (executed by the server) are reloaded from disk every time a hook handler is called, this means that one can change the behavior of the hook handler without the need to recompile the code, or having to restart the application being analyzed.
What's new in uhooker v1.3? ===========================
-Several bug fixes, everything should work better than before :)
-Fixed bug with readunicode() API where reading empty multibyte strings, resulted in the plugin freezing for ever.
-Now you can load multiple .CFG files (load one, then load another to hook something else, etc). Previously, you were only allowed to load one .CFG file with breakpoints/handlers definitions. Now you can load as many as you like whenever you want.
-If a .CFG file overlaps previously set hooks, you have the chance to redefine them (for example, you can dinamically change the file/function handling the breakpoint. This adds to the feature present since the first version of uhooker that allows runtime rewriting of the handler's code).
-Errors in the code of the handlers (written in python) are now correctly handled.
-Previously, if you had an error in the code you wrote to handle certain breakpoint, this caused the 'uhooker's python server' to 'crash', and you needed to restart your debugging session all over again.
This scenario was very common, particuarly if you were developing your own handler/script for the first time, or if you were modifying at runtime the code of a handler/script.
Well, no more! :), Now if you have an error (syntax error, identation error, general programming error,etc), the error that your handler has will be displayed on the uhooker's console, and you'll be able to recover from that error. This improvement means:
1-If an error occurs on the code, you don't need to restart the debugger's session (and lose the state of the program, etc.).
2-If you are changing in runtime the code of the handler, and you makee a mistake, you'll see what caused the error, and you can fix the script/handler and move on!.
-and there are probably more things but I didn't write them down and now I dont't remember :).
Comments to Hernan Ochoa (hochoa[at corest.com] and hernan[at gmail.com]).
