Hi Florian, On Sun, 2021-10-10 at 16:10 +0200, Florian Weimer wrote: > * Mickaël Salaün: > > > Being able to restrict execution also enables to protect the kernel by > > restricting arbitrary syscalls that an attacker could perform with a > > crafted binary or certain script languages. It also improves multilevel > > isolation by reducing the ability of an attacker to use side channels > > with specific code. These restrictions can natively be enforced for ELF > > binaries (with the noexec mount option) but require this kernel > > extension to properly handle scripts (e.g. Python, Perl). To get a > > consistent execution policy, additional memory restrictions should also > > be enforced (e.g. thanks to SELinux). > > One example I have come across recently is that code which can be > safely loaded as a Perl module is definitely not a no-op as a shell > script: it downloads code and executes it, apparently over an > untrusted network connection and without signature checking. > > Maybe in the IMA world, the expectation is that such ambiguous code > would not be signed in the first place, but general-purpose > distributions are heading in a different direction with > across-the-board signing: Automatically signing code is at least the first step in the right direction of only executing code with known provenance. Perhaps future work would address the code signing granularity. > > Signed RPM Contents > <https://fedoraproject.org/wiki/Changes/Signed_RPM_Contents> > > So I wonder if we need additional context information for a potential > LSM to identify the intended use case. My first thoughts were an enumeration UNSIGNED_DOWNLOADED_CODE or maybe even UNTRUSTED_DOWNLOADED_CODE, but that doesn't seem very helpful. What type of context information were you thinking about? Mimi
