On Thu, 2020-09-10 at 19:21 +0200, Mickaël Salaün wrote: > On 10/09/2020 19:04, Matthew Wilcox wrote: > > On Thu, Sep 10, 2020 at 06:46:09PM +0200, Mickaël Salaün wrote: > >> This ninth patch series rework the previous AT_INTERPRETED and O_MAYEXEC > >> series with a new syscall: introspect_access(2) . Access check are now > >> only possible on a file descriptor, which enable to avoid possible race > >> conditions in user space. > > > > But introspection is about examining _yourself_. This isn't about > > doing that. It's about doing ... something ... to a script that you're > > going to execute. If the script were going to call the syscall, then > > it might be introspection. Or if the interpreter were measuring itself, > > that would be introspection. But neither of those would be useful things > > to do, because an attacker could simply avoid doing them. > Michael, is the confusion here that IMA isn't measuring anything, but verifying the integrity of the file? The usecase, from an IMA perspective, is enforcing a system wide policy requiring everything executed to be signed. In this particular use case, the interpreter is asking the kernel if the script is signed with a permitted key. The signature may be an IMA signature or an EVM portable and immutable signature, based on policy. > Picking a good name other than "access" (or faccessat2) is not easy. The > idea with introspect_access() is for the calling task to ask the kernel > if this task should allows to do give access to a kernel resource which > is already available to this task. In this sense, we think that > introspection makes sense because it is the choice of the task to allow > or deny an access. > > > > > So, bad name. What might be better? sys_security_check()? > > sys_measure()? sys_verify_fd()? I don't know. > > > > "security_check" looks quite broad, "measure" doesn't make sense here, > "verify_fd" doesn't reflect that it is an access check. Yes, not easy, > but if this is the only concern we are on the good track. :) Maybe replacing the term "measure" with "integrity", but rather than "integrity_check", something along the lines of fgetintegrity, freadintegrity, fcheckintegrity. Mimi > > > Other ideas: > - interpret_access (mainly, but not only, for interpreters) > - indirect_access > - may_access > - faccessat3
