On Tue, 2013-01-15 at 20:30 -0800, Eric W. Biederman wrote: > Vivek Goyal <vgo...@redhat.com> writes: > > > If a binary is signed, verify its signature. If signature is not valid, do > > not allow execution. If binary is not signed, execution is allowed > > unconditionally. > > > > CONFIG_BINFMT_ELF_SIGNATURE controls whether elf binary signature support > > is compiled in or not. > > > > Signature are expected to be present in elf section ".section". This code > > is written along the lines of module signature verification code. Just > > that I have removed the magic string. It is not needed as signature is > > expected to be present in a specific section. > > > > I put the signature into a section, instead of appending it so that > > strip operation works fine. > > > > One signs and verifies all the areas mapped by PT_LOAD segments of elf > > binary. Typically Elf header is mapped in first PT_LOAD segment. As adding > > .signature section can change three elf header fields (e_shoff, e_shnum > > and e_shstrndx), these fields are excluded from digest calculation > > My gut feel says that a signature that we verify should reside in an ELF > segment. Sections are for the linker not the kernel. > > I don't totally know what the signature should cover but my gut feels > says the signature should come after ever non-signature segment and > cover all of the prior segments (PT_LOAD or not). Because presumably > the loader needs to look at everything in a segment. We can > restrict ourselves to only processing signed binaries on executables > with only PT_LOAD segments and signatures for now.
Please remind me why you can't use IMA-appraisal, which was upstreamed in Linux 3.7? Why another method is needed? With IMA-appraisal, there are a couple of issues that would still need to be addressed: - missing the ability to specify the validation method required. - modify the ima_appraise_tcb policy policy to require elf executables to be digitally signed. - security_bprm_check() is called before the binary handler is known. The first issue is addressed by a set of patches queued to be upstreamed in linux-integrity/next-ima-appraise-status. To address the last issue would either require moving the existing bprm_check or defining a new hook after the binary handler is known. thanks, Mimi -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
