symbols_loaded¶

Intro¶

symbols_loaded - a shared object which exports a watched symbol was loaded.

Description¶

An event marking that a shared object, which export symbols configured to be watched, was loaded to current process. This event can help in identifying some shared object usage in the system, or inform on the occasion that a shared object tries to override some symbol of another library.

Configuring the event¶

The event is configured using arguments filtering. For each argument, a filter can be used to configure the operation:

symbols¶

Configure the watched symbols by the event. Specify the full name of the symbol for each symbol. The use is only with the = operator, and wildcards aren't supported.

library_path¶

Whitelist for shared object paths prefixes. The path can be absolute, or just a library name. If only a name is given, then any shared object inside the known libraries directories which starts with the prefix will be whitelisted. The use is only with the != operator, and wildcards aren't supported.

Arguments¶

library_path:const char*[K] - the path of the shared object file loaded.
symbols:const char*const*[U,TOCTOU] - the watched symbols exported by the shared object.

Dependency Events¶

shared_object_loaded¶

The event of shared object loading triggers this event, and supplies the information on the shared object necessary to examine its shared objects.

sched_process_exec¶

Used by tracee to maintain mount NS cache, used in this event to get to processes file system

Example Use Case¶

To catch SO which tries to override the fopen function of libc, we can use the event in the following way:

./dist/tracee -f e=symbols_loaded -f symbols_loaded.args.symbols=fopen symbols_loaded.args.library_path!=libc

Issues¶

Because the event is implemented in user-mode, it needs to open and read files. This means that the event is not very performance efficient (although it uses some optimizations). It also means that until the SO file is opened, it could be altered or removed.

shared_object_loaded, symbols_collision