How can I intercept/rewrite Windows ODBC calls?

Question

I'm looking to modify ODBC calls either directly before hitting the ODBC stack or between the ODBC stack and the dll driver for the connection I am using. For instance, if the application does a SELECT, I want to be able to modify it be SELECT_ALL How can I do that?

Answer 1

The ODBC setup information points to the driver DLL. You could replace that with your own DLL that has the ODBC entrypoints. Simply make all the ones you don't care about be simple calls to the "real" DLL. The execute and prepare entrypoints could modify the given statement before passing it on to the driver DLL.

For example, if using a User DSN, you might replace the value in HKCU\Software\ODBC.ini\datasourcename\Driver with your own shim DLL.

After a bit of googling, I am not finding an obvious empty shell project that would be an ideal starting point. The API reference has details about the API. In general, though, you shouldn't really need information from there. You just need to pass the parameters for each API to the actuall driver DLL. The function prototypes could be extracted from sql.h and sqlext.h.

An alternative method that might be easier than writing a shim DLL would be to hook just the execute and prepare functions (probably just SQLExecDirect and SQLPrepare). This article is the first hit I saw on doing that.