On Mon, Jul 8, 2024 at 2:25 PM Steve Dower <steve.dower@xxxxxxxxxx> wrote: > > On 08/07/2024 22:15, Jeff Xu wrote: > > IIUC: > > CHECK=0, RESTRICT=0: do nothing, current behavior > > CHECK=1, RESTRICT=0: permissive mode - ignore AT_CHECK results. > > CHECK=0, RESTRICT=1: call AT_CHECK, deny if AT_CHECK failed, no exception. > > CHECK=1, RESTRICT=1: call AT_CHECK, deny if AT_CHECK failed, except > > those in the "checked-and-allowed" list. > > I had much the same question for Mickaël while working on this. > > Essentially, "CHECK=0, RESTRICT=1" means to restrict without checking. > In the context of a script or macro interpreter, this just means it will > never interpret any scripts. Non-binary code execution is fully disabled > in any part of the process that respects these bits. > I see, so Mickaël does mean this will block all scripts. I guess, in the context of dynamic linker, this means: no more .so loading, even "dlopen" is called by an app ? But this will make the execve() fail. > "CHECK=1, RESTRICT=1" means to restrict unless AT_CHECK passes. This > case is the allow list (or whatever mechanism is being used to determine > the result of an AT_CHECK check). The actual mechanism isn't the > business of the script interpreter at all, it just has to refuse to > execute anything that doesn't pass the check. So a generic interpreter > can implement a generic mechanism and leave the specifics to whoever > configures the machine. > In the context of dynamic linker. this means: if .so passed the AT_CHECK, ldopen() can still load it. If .so fails the AT_CHECK, ldopen() will fail too. Thanks -Jeff > The other two case are more obvious. "CHECK=0, RESTRICT=0" is the > zero-overhead case, while "CHECK=1, RESTRICT=0" might log, warn, or > otherwise audit the result of the check, but it won't restrict execution. > > Cheers, > Steve
