3.7 is also affected in bionic:
$ hardening-check /usr/bin/python3.7
/usr/bin/python3.7:
Position Independent Executable: no, normal executable!
Stack protected: yes
Fortify Source functions: yes (some protected functions found)
Read-only relocations: yes
Immediate binding: no, not found!
** Also affects: python3.7 (Ubuntu)
Importance: Undecided
Status: New
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https://bugs.launchpad.net/bugs/1452115
Title:
Python interpreter binary is not compiled as PIE
Status in Python:
New
Status in python2.7 package in Ubuntu:
Fix Released
Status in python3.4 package in Ubuntu:
Fix Released
Status in python3.6 package in Ubuntu:
Confirmed
Status in python3.7 package in Ubuntu:
New
Status in python3.8 package in Ubuntu:
Confirmed
Status in python3.8 package in Debian:
New
Bug description:
The python2.7 binary (installed at /usr/bin/python2.7; package version
2.7.6-8) is not compiled as a position independent executable (PIE).
It appears that the python compilation process is somewhat arcane and
the hardening wrapper probably doesn't do the trick for it.
This is incredibly dangerous as it means that any vulnerability within
a native module (e.g. ctypes-based), or within python itself will
expose an incredibly large amount of known memory contents at known
addresses (including a large number of dangerous instruction
groupings). This enables ROP-based (https://en.wikipedia.org/wiki
/Return-oriented_programming) to abuse the interpreter itself to
bypass non-executable page protections.
I have put together an example vulnerable C shared object (with a buffer
overflow) accessed via python through the ctypes interface as an example. This
uses a single ROP "gadget" on top of using the known PLT location for system(3)
(https://en.wikipedia.org/wiki/Return-to-libc_attack) to call "id". The example
code is accessible at:
- https://gist.github.com/ChaosData/ae6076cb1c3cc7b0a367
I'm not exactly familiar enough with the python build process to say
where exactly an -fPIE needs to be injected into a script/makefile,
but I feel that given the perceived general preference for ctypes-
based modules over python written ones, as the native code
implementations tend to be more performant, this feels like a large
security hole within the system. Given the nature of this "issue," I'm
not 100% sure of where it is best reported, but from what I can tell,
this conflicts with the Ubuntu hardening features and is definitely
exploitable should a native module contain a sufficiently exploitable
vulnerability that allows for control of the instruction register.
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