[PATCH 3/5] LSM: Add security_state function pointer in lsm_info struct

Lakshmi Ramasubramanian
2020-06-13T02:42:02Z

The security modules that require their data to be measured need to
define a function that the LSM can call to gather the data.

Add a function pointer field namely security_state in lsm_info structure.
Update LSM to call this security module function, if defined, to gather
data and measure it by calling the IMA hook ima_lsm_state().

Signed-off-by: Lakshmi Ramasubramanian <nramas@linux.microsoft.com>
---
include/linux/lsm_hooks.h | 2 ++
security/security.c | 60 ++++++++++++++++++++++++++++++++++++++-
2 files changed, 61 insertions(+), 1 deletion(-)

diff --git a/include/linux/lsm_hooks.h b/include/linux/lsm_hooks.h
index 3e62dab77699..da248c3fd4ac 100644
--- a/include/linux/lsm_hooks.h
+++ b/include/linux/lsm_hooks.h
@@ -1568,6 +1568,8 @@ struct lsm_info {
int *enabled; /* Optional: controlled by CONFIG_LSM */
int (*init)(void); /* Required. */
struct lsm_blob_sizes *blobs; /* Optional: for blob sharing. */
+ int (*security_state)(char **lsm_name, void **state,
+ int *state_len); /*Optional */
};

extern struct lsm_info __start_lsm_info[], __end_lsm_info[];
diff --git a/security/security.c b/security/security.c
index e0290b7e6a08..a6e2d1cd95af 100644
--- a/security/security.c
+++ b/security/security.c
@@ -86,6 +86,9 @@ static __initconst const char * const builtin_lsm_order = CONFIG_LSM;
static __initdata struct lsm_info **ordered_lsms;
static __initdata struct lsm_info *exclusive;

+static struct lsm_info *security_state_lsms;
+static int security_state_lsms_count;
+
static __initdata bool debug;
#define init_debug(...) \
do { \
@@ -235,6 +238,57 @@ static void __init initialize_lsm(struct lsm_info *lsm)
}
}

+static int measure_security_state(struct lsm_info *lsm)
+{
+ char *lsm_name = NULL;
+ void *state = NULL;
+ int state_len = 0;
+ int rc;
+
+ if (!lsm->security_state)
+ return 0;
+
+ rc = lsm->security_state(&lsm_name, &state, &state_len);
+ if ((rc == 0) && (state_len > 0)) {
+ ima_lsm_state(lsm_name, state, state_len);
+ kfree(state);
+ kfree(lsm_name);
+ }
+
+ return rc;
+}
+
+static void __init initialize_security_state_lsms(void)
+{
+ struct lsm_info **lsm;
+ int count = 0;
+ int inx;
+
+ for (lsm = ordered_lsms; *lsm; lsm++) {
+ if ((*lsm)->security_state)
+ count++;
+ }
+
+ if (count == 0)
+ return;
+
+ security_state_lsms = kcalloc(count, sizeof(struct lsm_info),
+ GFP_KERNEL);
+ if (!security_state_lsms)
+ return;
+
+ inx = 0;
+ for (lsm = ordered_lsms; *lsm; lsm++) {
+ if ((*lsm)->security_state) {
+ security_state_lsms[inx].security_state =
+ (*lsm)->security_state;
+ inx++;
+ }
+ }
+
+ security_state_lsms_count = count;
+}
+
/* Populate ordered LSMs list from comma-separated LSM name list. */
static void __init ordered_lsm_parse(const char *order, const char *origin)
{
@@ -352,8 +406,12 @@ static void __init ordered_lsm_init(void)

lsm_early_cred((struct cred *) current->cred);
lsm_early_task(current);
- for (lsm = ordered_lsms; *lsm; lsm++)
+ for (lsm = ordered_lsms; *lsm; lsm++) {
initialize_lsm(*lsm);
+ measure_security_state(*lsm);
+ }
+
+ initialize_security_state_lsms();

kfree(ordered_lsms);
}
--
2.27.0