From 6d15e0e643293c38de7cfbdf71149d474801b3c7 Mon Sep 17 00:00:00 2001 From: Alexander Popov Date: Sun, 16 Jun 2024 08:48:14 +0300 Subject: [PATCH] Add the 'kernel.oops_limit' and 'kernel.warn_limit' checks --- kernel_hardening_checker/checks.py | 9 ++++++--- 1 file changed, 6 insertions(+), 3 deletions(-) diff --git a/kernel_hardening_checker/checks.py b/kernel_hardening_checker/checks.py index b84ecd6..9cb414e 100755 --- a/kernel_hardening_checker/checks.py +++ b/kernel_hardening_checker/checks.py @@ -424,7 +424,6 @@ def add_kconfig_checks(l: List[ChecklistObjType], arch: str) -> None: l += [OR(KconfigCheck('cut_attack_surface', 'a13xp0p0v', 'MAGIC_SYSRQ_SERIAL', 'is not set'), KconfigCheck('cut_attack_surface', 'a13xp0p0v', 'MAGIC_SYSRQ_DEFAULT_ENABLE', '0x0'))] - # 'harden_userspace' if arch == 'ARM64': l += [KconfigCheck('harden_userspace', 'defconfig', 'ARM64_PTR_AUTH', 'y')] @@ -678,8 +677,6 @@ def normalize_cmdline_options(option: str, value: str) -> str: # nosmt sysfs control file # vm.mmap_rnd_bits=max (?) # abi.vsyscall32 (any value except 2) -# kernel.oops_limit (think about a proper value) -# kernel.warn_limit (think about a proper value) # net.ipv4.tcp_syncookies=1 (?) def add_sysctl_checks(l: List[ChecklistObjType], _arch: StrOrNone) -> None: @@ -694,6 +691,12 @@ def add_sysctl_checks(l: List[ChecklistObjType], _arch: StrOrNone) -> None: l += [OR(SysctlCheck('self_protection', 'kspp', 'net.core.bpf_jit_harden', '2'), AND(KconfigCheck('-', '-', 'BPF_JIT', 'is not set'), have_kconfig))] + # Choosing a right value for 'kernel.oops_limit' and 'kernel.warn_limit' is not easy. + # A small value (e.g. 1, which is recommended by KSPP) allows easy DoS. + # A large value (e.g. 10000, which is default 'kernel.oops_limit') may miss the exploit attempt. + # Let's choose 100 as a reasonable compromise. + l += [SysctlCheck('self_protection', 'a13xp0p0v', 'kernel.oops_limit', '100')] + l += [SysctlCheck('self_protection', 'a13xp0p0v', 'kernel.warn_limit', '100')] l += [SysctlCheck('cut_attack_surface', 'kspp', 'kernel.dmesg_restrict', '1')] l += [SysctlCheck('cut_attack_surface', 'kspp', 'kernel.perf_event_paranoid', '3')] # with a custom patch, see https://lwn.net/Articles/696216/ -- 2.31.1