[PATCH v24 03/25] LSM: provide lsm name and id slot mappings

Casey Schaufler
2021-01-26T18:11:03Z

Provide interfaces to map LSM slot numbers and LSM names.
Update the LSM registration code to save this information.

Signed-off-by: Casey Schaufler <casey@schaufler-ca.com>
---
include/linux/security.h | 4 ++++
security/security.c | 45 ++++++++++++++++++++++++++++++++++++++++
2 files changed, 49 insertions(+)

diff --git a/include/linux/security.h b/include/linux/security.h
index 4a109092a8d7..a99a4307176f 100644
--- a/include/linux/security.h
+++ b/include/linux/security.h
@@ -192,6 +192,10 @@ static inline bool lsmblob_equal(struct lsmblob *bloba, struct lsmblob *blobb)
return !memcmp(bloba, blobb, sizeof(*bloba));
}

+/* Map lsm names to blob slot numbers */
+extern int lsm_name_to_slot(char *name);
+extern const char *lsm_slot_to_name(int slot);
+
/* These functions are in security/commoncap.c */
extern int cap_capable(const struct cred *cred, struct user_namespace *ns,
int cap, unsigned int opts);
diff --git a/security/security.c b/security/security.c
index 39dce9eb3bcd..05ce02ae7c46 100644
--- a/security/security.c
+++ b/security/security.c
@@ -474,6 +474,50 @@ static int lsm_append(const char *new, char **result)
* Current index to use while initializing the lsmblob secid list.
*/
static int lsm_slot __lsm_ro_after_init;
+static struct lsm_id *lsm_slotlist[LSMBLOB_ENTRIES] __lsm_ro_after_init;
+
+/**
+ * lsm_name_to_slot - Report the slot number for a security module
+ * @name: name of the security module
+ *
+ * Look up the slot number for the named security module.
+ * Returns the slot number or LSMBLOB_INVALID if @name is not
+ * a registered security module name.
+ */
+int lsm_name_to_slot(char *name)
+{
+ int i;
+
+ for (i = 0; i < lsm_slot; i++)
+ if (strcmp(lsm_slotlist[i]->lsm, name) == 0)
+ return i;
+
+ return LSMBLOB_INVALID;
+}
+
+/**
+ * lsm_slot_to_name - Get the name of the security module in a slot
+ * @slot: index into the interface LSM slot list.
+ *
+ * Provide the name of the security module associated with
+ * a interface LSM slot.
+ *
+ * If @slot is LSMBLOB_INVALID return the value
+ * for slot 0 if it has been set, otherwise NULL.
+ *
+ * Returns a pointer to the name string or NULL.
+ */
+const char *lsm_slot_to_name(int slot)
+{
+ if (slot == LSMBLOB_INVALID)
+ slot = 0;
+ else if (slot >= LSMBLOB_ENTRIES || slot < 0)
+ return NULL;
+
+ if (lsm_slotlist[slot] == NULL)
+ return NULL;
+ return lsm_slotlist[slot]->lsm;
+}

/**
* security_add_hooks - Add a modules hooks to the hook lists.
@@ -493,6 +537,7 @@ void __init security_add_hooks(struct security_hook_list *hooks, int count,
if (lsmid->slot == LSMBLOB_NEEDED) {
if (lsm_slot >= LSMBLOB_ENTRIES)
panic("%s Too many LSMs registered.\n", __func__);
+ lsm_slotlist[lsm_slot] = lsmid;
lsmid->slot = lsm_slot++;
init_debug("%s assigned lsmblob slot %d\n", lsmid->lsm,
lsmid->slot);
--
2.25.4