Comment out the RANDSTRUCT_PERFORMANCE check

[kconfig-hardened-check.git] / kernel_hardening_checker / checks.py

diff --git a/kernel_hardening_checker/checks.py b/kernel_hardening_checker/checks.py
index fda5d46986f4f229c3e839f49f2107751005e907..c2440cfc33850cd2cc41905e30475f23db7e3f10 100755 (executable)
--- a/kernel_hardening_checker/checks.py
+++ b/kernel_hardening_checker/checks.py
@@ -171,9 +171,9 @@ def add_kconfig_checks(l: List[ChecklistObjType], arch: str) -> None:
     randstruct_is_set = OR(KconfigCheck('self_protection', 'kspp', 'RANDSTRUCT_FULL', 'y'),
                            KconfigCheck('self_protection', 'kspp', 'GCC_PLUGIN_RANDSTRUCT', 'y'))
     l += [randstruct_is_set]
-    l += [AND(KconfigCheck('self_protection', 'kspp', 'RANDSTRUCT_PERFORMANCE', 'is not set'),
-              KconfigCheck('self_protection', 'kspp', 'GCC_PLUGIN_RANDSTRUCT_PERFORMANCE', 'is not set'),
-              randstruct_is_set)]
+#   l += [AND(KconfigCheck('self_protection', 'kspp', 'RANDSTRUCT_PERFORMANCE', 'is not set'),
+#             KconfigCheck('self_protection', 'kspp', 'GCC_PLUGIN_RANDSTRUCT_PERFORMANCE', 'is not set'),
+#             randstruct_is_set)] # Comment this out for now: KSPP has revoked this recommendation
     hardened_usercopy_is_set = KconfigCheck('self_protection', 'kspp', 'HARDENED_USERCOPY', 'y')
     l += [hardened_usercopy_is_set]
     l += [AND(KconfigCheck('self_protection', 'kspp', 'HARDENED_USERCOPY_FALLBACK', 'is not set'),
@@ -421,7 +421,8 @@ def add_kconfig_checks(l: List[ChecklistObjType], arch: str) -> None:
     l += [KconfigCheck('cut_attack_surface', 'a13xp0p0v', 'BLK_DEV_WRITE_MOUNTED', 'is not set')]
     l += [OR(KconfigCheck('cut_attack_surface', 'a13xp0p0v', 'TRIM_UNUSED_KSYMS', 'y'),
              modules_not_set)]
-
+    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':
@@ -532,6 +533,7 @@ def add_cmdline_checks(l: List[ChecklistObjType], arch: str) -> None:
     l += [CmdlineCheck('self_protection', 'kspp', 'slab_merge', 'is not set')] # consequence of 'slab_nomerge' by kspp
     l += [CmdlineCheck('self_protection', 'kspp', 'slub_merge', 'is not set')] # consequence of 'slab_nomerge' by kspp
     l += [CmdlineCheck('self_protection', 'kspp', 'page_alloc.shuffle', '1')]
+    l += [CmdlineCheck('self_protection', 'kspp', 'cfi', 'kcfi')]
     l += [OR(CmdlineCheck('self_protection', 'kspp', 'slab_nomerge', 'is present'),
              AND(KconfigCheck('self_protection', 'clipos', 'SLAB_MERGE_DEFAULT', 'is not set'),
                  CmdlineCheck('self_protection', 'kspp', 'slab_merge', 'is not set'),
@@ -674,10 +676,7 @@ def normalize_cmdline_options(option: str, value: str) -> str:
 #    vm.mmap_min_addr has a good value
 #    nosmt sysfs control file
 #    vm.mmap_rnd_bits=max (?)
-#    kernel.sysrq=0
 #    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:
@@ -692,6 +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/
@@ -711,10 +716,14 @@ def add_sysctl_checks(l: List[ChecklistObjType], _arch: StrOrNone) -> None:
           # At first, it disabled unprivileged userfaultfd,
           # and since v5.11 it enables unprivileged userfaultfd for user-mode only.
 
-    l += [OR(SysctlCheck('cut_attack_surface', 'clipos', 'kernel.modules_disabled', '1'),
+    l += [OR(SysctlCheck('cut_attack_surface', 'kspp', 'kernel.modules_disabled', '1'),
              AND(KconfigCheck('cut_attack_surface', 'kspp', 'MODULES', 'is not set'),
                  have_kconfig))] # radical, but may be useful in some cases
 
+    l += [OR(SysctlCheck('cut_attack_surface', 'a13xp0p0v', 'kernel.sysrq', '0'),
+             AND(KconfigCheck('cut_attack_surface', 'clipos', 'MAGIC_SYSRQ', 'is not set'),
+                 have_kconfig))]
+
     l += [SysctlCheck('harden_userspace', 'kspp', 'fs.protected_symlinks', '1')]
     l += [SysctlCheck('harden_userspace', 'kspp', 'fs.protected_hardlinks', '1')]
     l += [SysctlCheck('harden_userspace', 'kspp', 'fs.protected_fifos', '2')]