Sunday, February 26, 2023

Reverse Engineering Notes - _ITM_deregisterTMCloneTable


what is _ITM_deregisterTMCloneTable?

_ITM_deregisterTMCloneTable is another symbol related to transactional memory support in GCC-compiled programs. It is used to remove a previously registered transactional memory clone table.

Transactional memory is a feature in some CPUs and programming languages that allows a group of memory operations to be performed as a single, atomic transaction. This can make it easier to write concurrent code, as the programmer does not need to worry about race conditions or manually synchronizing access to shared data.

When a program is compiled with transactional memory support, GCC may insert calls to various internal library functions such as _ITM_addUserCommitAction and _ITM_deregisterTMCloneTable to manage the transactional memory operations.

As with _ITM_addUserCommitAction, the presence of _ITM_deregisterTMCloneTable in a program's symbols can be a useful indicator for reverse engineers looking to understand how the program was compiled and how it works. By analyzing the usage of these symbols in the program's code, a reverse engineer may be able to gain insight into how the program handles concurrent access to shared data, and potentially identify bugs or vulnerabilities related to transactional memory usage.

When reverse engineering an application or trying to harden it against attacks, identifying weak library symbols can be useful to find potential vulnerabilities or attack vectors. Radare2 can be used to search for such symbols using the iS command, which lists all weakly referenced symbols in the binary.

To identify and patch weak library symbols, one approach is to replace the weakly referenced symbol with a stronger, explicitly referenced symbol. This can be done using Radare2's patching capabilities, such as the wx command to write new values to memory.

In the case of the _ITM_addUserCommitAction symbol, which is a weakly referenced symbol of type NOTYPE, it may not be immediately clear how it is being used or if it is a potential vulnerability. However, investigating the context in which it is referenced and understanding its purpose in the program may reveal potential issues.

Similarly, the _ITM_deregisterTMCloneTable symbol may also be a potential target for patching or hardening, depending on the specific use case and potential vulnerabilities it may introduce. It is important to carefully analyze the use of all weakly referenced symbols in the binary and assess their potential impact on the security of the program.

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