On 09/24/2018 05:18 PM, Kees Cook wrote:
This introduces the "lsm.enable=..." and "lsm.disable=..." boot parameters
which each can contain a comma-separated list of LSMs to enable or
disable, respectively. The string "all" matches all LSMs.
This has very similar functionality to the existing per-LSM enable
handling ("apparmor.enabled=...", etc), but provides a centralized
place to perform the changes. These parameters take precedent over any
LSM-specific boot parameters.
Disabling an LSM means it will not be considered when performing
initializations. Enabling an LSM means either undoing a previous
LSM-specific boot parameter disabling or a undoing a default-disabled
CONFIG setting.
For example: "lsm.disable=apparmor apparmor.enabled=1" will result in
AppArmor being disabled. "selinux.enabled=0 lsm.enable=selinux" will
result in SELinux being enabled.
Signed-off-by: Kees Cook <redacted>
I don't like this. It brings about conflicting kernel params that are
bound to confuse users. Its pretty easy for a user to understand that
when they specify a parameter manually at boot, that it overrides the
build time default. But conflicting kernel parameters are a lot harder
to deal with.
I prefer a plain enabled= list being an override of the default build
time value. Where conflicts with LSM-specific configs always result in
the LSM being disabled with a complaint about the conflict.
Though I have yet to be convinced its worth the cost, I do recognize
it is sometimes convenient to disable a single LSM, instead of typing
in a whole list of what to enable. If we have to have conflicting
kernel parameters I would prefer that the conflict throw up a warning
and leaving the LSM with the conflicting config disabled.
quoted hunk ↗ jump to hunk
---
.../admin-guide/kernel-parameters.txt | 12 ++++++++++
security/Kconfig | 4 +++-
security/security.c | 22 +++++++++++++++++++
3 files changed, 37 insertions(+), 1 deletion(-)
diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
index 32d323ee9218..67c90985d2b8 100644
--- a/Documentation/admin-guide/kernel-parameters.txt
+++ b/Documentation/admin-guide/kernel-parameters.txt
@@ -2276,6 +2276,18 @@
lsm.debug [SECURITY] Enable LSM initialization debugging output.
+ lsm.disable=lsm1,...,lsmN
+ [SECURITY] Comma-separated list of LSMs to disable
+ at boot time. This overrides "lsm.enable=",
+ CONFIG_LSM_ENABLE, and any per-LSM CONFIGs and boot
+ parameters.
+
+ lsm.enable=lsm1,...,lsmN
+ [SECURITY] Comma-separated list of LSMs to enable
+ at boot time. This overrides any omissions from
+ CONFIG_LSM_ENABLE, and any per-LSM CONFIGs and
+ boot parameters.
+
machvec= [IA-64] Force the use of a particular machine-vector
(machvec) in a generic kernel.
Example: machvec=hpzx1_swiotlb
diff --git a/security/Kconfig b/security/Kconfig
index 71306b046270..1a82a006cc62 100644
--- a/security/Kconfig
+++ b/security/Kconfig
@@ -282,7 +282,9 @@ config LSM_ENABLE
help
A comma-separate list of LSMs to enable by default at boot. The
default is "all", to enable all LSM modules at boot. Any LSMs
- not listed here will be disabled by default.
+ not listed here will be disabled by default. This can be
+ changed with the "lsm.enable=" and "lsm.disable=" boot
+ parameters.
endmenu
diff --git a/security/security.c b/security/security.c
index 7ecb9879a863..456a3f73bc36 100644
--- a/security/security.c
+++ b/security/security.c
@@ -44,6 +44,8 @@ char *lsm_names;
/* Boot-time LSM user choice */
static __initdata char chosen_lsm[SECURITY_NAME_MAX + 1] =
CONFIG_DEFAULT_SECURITY;
+static __initdata const char *chosen_lsm_enable;
+static __initdata const char *chosen_lsm_disable;
static __initconst const char * const builtin_lsm_enable = CONFIG_LSM_ENABLE;
@@ -185,6 +187,10 @@ static void __init prepare_lsm_enable(void)
{
/* Prepare defaults. */
parse_lsm_enable(builtin_lsm_enable, default_enabled, true);
+
+ /* Process "lsm.enable=" and "lsm.disable=", if given. */
+ parse_lsm_enable(chosen_lsm_enable, set_enabled, true);
+ parse_lsm_enable(chosen_lsm_disable, set_enabled, false);
}
/**@@ -240,6 +246,22 @@ static int __init enable_debug(char *str)
}
__setup("lsm.debug", enable_debug);
+/* Explicitly enable a list of LSMs. */
+static int __init enable_lsm(char *str)
+{
+ chosen_lsm_enable = str;
+ return 1;
+}
+__setup("lsm.enable=", enable_lsm);
+
+/* Explicitly disable a list of LSMs. */
+static int __init disable_lsm(char *str)
+{
+ chosen_lsm_disable = str;
+ return 1;
+}
+__setup("lsm.disable=", disable_lsm);
+
static bool match_last_lsm(const char *list, const char *lsm)
{
const char *last;