Hi Adam, On Tue, 2017-03-07 at 13:39 +0100, Adam Šulc wrote: > I work on ABRT improvement in order to increase security related to core > backtrace generating using elfutils library. > Here is a short description of my problem: > > Goal is to not call base code in elfutils and gdb functions under root. > If you are more interested you can read more there: > https://github.com/abrt/abrt/issues/890 > > We need root for opening /proc files only. > First, we open these files under root, > then we drop capabilities & privileges and finally, we generate > core_backtrace.
If you drop priviliges to the uid of the process then you should still be able to open /proc files for that process/user. That seems the simplest solution. > We have one problem, that we need to pass the opened /proc file to this > function: > dwfl_linux_proc_report (Dwfl *dwfl, pid_t pid) > Because this function opens the /proc file itself, thus it is hard coded > and we cannot pass our /proc file pointer: > https://github.com/abrt/satyr/blob/master/lib/core_unwind_elfutils.c#L251 > So we dont know how to pass the opened file to this function. > > Do you have any idea how to pass the open file descriptor into the > function? Or what is the best way how to achieve this? See the function right after dwfl_linux_proc_report in libdwfl.h: /* Call dwfl_report_module for each file mapped into the address space of PID. Returns zero on success, -1 if dwfl_report_module failed, or an errno code if opening the proc files failed. */ extern int dwfl_linux_proc_report (Dwfl *dwfl, pid_t pid); /* Similar, but reads an input stream in the format of Linux /proc/PID/maps files giving module layout, not the file for a live process. */ extern int dwfl_linux_proc_maps_report (Dwfl *dwfl, FILE *); It does slightly less because it doesn't know the running process pid, but might do enough for your use case. But I think just dropping privileges to the uid of the process is easier. Cheers, Mark
