On 04/07/17 at 03:45am, Mimi Zohar wrote: > On Fri, 2017-04-07 at 14:19 +0800, Dave Young wrote: > > On 04/06/17 at 11:49pm, Mimi Zohar wrote: > > > On Fri, 2017-04-07 at 11:05 +0800, Dave Young wrote: > > > > On 04/05/17 at 09:15pm, David Howells wrote: > > > > > From: Chun-Yi Lee <joeyli.kernel@xxxxxxxxx> > > > > > > > > > > When KEXEC_VERIFY_SIG is not enabled, kernel should not loads image > > > > > through kexec_file systemcall if securelevel has been set. > > > > > > > > > > This code was showed in Matthew's patch but not in git: > > > > > https://lkml.org/lkml/2015/3/13/778 > > I specifically checked to make sure that either kexec_file() signature > verification was acceptable and would have commented then, if it had > not been included. > > > > > > Cc: Matthew Garrett <mjg59@xxxxxxxxxxxxx> > > > > > Signed-off-by: Chun-Yi Lee <jlee@xxxxxxxx> > > > > > Signed-off-by: David Howells <dhowells@xxxxxxxxxx> > > > > > cc: kexec@xxxxxxxxxxxxxxxxxxx > > > > > --- > > > > > > > > > > kernel/kexec_file.c | 6 ++++++ > > > > > 1 file changed, 6 insertions(+) > > > > > > > > > > diff --git a/kernel/kexec_file.c b/kernel/kexec_file.c > > > > > index b118735fea9d..f6937eecd1eb 100644 > > > > > --- a/kernel/kexec_file.c > > > > > +++ b/kernel/kexec_file.c > > > > > @@ -268,6 +268,12 @@ SYSCALL_DEFINE5(kexec_file_load, int, kernel_fd, int, initrd_fd, > > > > > if (!capable(CAP_SYS_BOOT) || kexec_load_disabled) > > > > > return -EPERM; > > > > > > > > > > + /* Don't permit images to be loaded into trusted kernels if we're not > > > > > + * going to verify the signature on them > > > > > + */ > > > > > + if (!IS_ENABLED(CONFIG_KEXEC_VERIFY_SIG) && kernel_is_locked_down()) > > > > > + return -EPERM; > > > > > + > > > > > > > > > > > IMA can be used to verify file signatures too, based on the LSM hooks > > > in kernel_read_file_from_fd(). CONFIG_KEXEC_VERIFY_SIG should not be > > > required. > > > > Mimi, I remember we talked somthing before about the two signature > > verification. One can change IMA policy in initramfs userspace, > > also there are kernel cmdline param to disable IMA, so it can break the > > lockdown? Suppose kexec boot with ima disabled cmdline param and then > > kexec reboot again.. > > Right, we discussed that the same method of measuring the kexec image > and initramfs, for extending trusted boot to the OS, could also be > used for verifying the kexec image and initramfs signatures, for > extending secure boot to the OS. The file hash would be calculated > once for both. > > All of your concerns could be addressed with very minor changes to > IMA. (Continued in response to David.) Thanks! As long as IMA can ensure not breaking the lockdown it should be fine to add an check for either !CONFIG_KEXEC_VERIFY_SIG or !IMA enforced. > > > > > > > > /* Make sure we have a legal set of flags */ > > > > > if (flags != (flags & KEXEC_FILE_FLAGS)) > > > > > return -EINVAL; > > > > > > > > > > > > > > > _______________________________________________ > > > > > kexec mailing list > > > > > kexec@xxxxxxxxxxxxxxxxxxx > > > > > http://lists.infradead.org/mailman/listinfo/kexec > > > > > > > > Acked-by: Dave Young <dyoung@xxxxxxxxxx> > > > > > > > > Thanks > > > > Dave > > > > -- > > > > To unsubscribe from this list: send the line "unsubscribe linux-security-module" in > > > > the body of a message to majordomo@xxxxxxxxxxxxxxx > > > > More majordomo info at http://vger.kernel.org/majordomo-info.html > > > > > > > > > > -- To unsubscribe from this list: send the line "unsubscribe linux-efi" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
