[v26,03/25] LSM: provide lsm name and id slot mappings

Commit Message

Casey Schaufler May 13, 2021, 8:07 p.m. UTC

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

Signed-off-by: Casey Schaufler <[e-mail]>
---
 include/linux/security.h |  4 ++++
 security/security.c      | 45 ++++++++++++++++++++++++++++++++++++++++
 2 files changed, 49 insertions(+)

Comments

Kees Cook May 14, 2021, 7 p.m. UTC | #1

On Thu, May 13, 2021 at 01:07:45PM -0700, Casey Schaufler wrote:
> Provide interfaces to map LSM slot numbers and LSM names.
> Update the LSM registration code to save this information.
> 
> Signed-off-by: Casey Schaufler <[e-mail]>

Seems a reasonable set of utilities. :)

Reviewed-by: Kees Cook <[e-mail]>

Paul Moore May 21, 2021, 8:18 p.m. UTC | #2

On Thu, May 13, 2021 at 4:11 PM Casey Schaufler <[e-mail]> wrote:
>
> Provide interfaces to map LSM slot numbers and LSM names.
> Update the LSM registration code to save this information.
>
> Signed-off-by: Casey Schaufler <[e-mail]>
> ---
>  include/linux/security.h |  4 ++++
>  security/security.c      | 45 ++++++++++++++++++++++++++++++++++++++++
>  2 files changed, 49 insertions(+)

Acked-by: Paul Moore <[e-mail]>


--
paul moore
www.paul-moore.com

Patch

diff --git a/include/linux/security.h b/include/linux/security.h
index 62588bc522ba..ca9485105f00 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 a3276deb1b8a..9471bcecc052 100644
--- a/security/security.c
+++ b/security/security.c
@@ -476,6 +476,50 @@  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.
@@ -495,6 +539,7 @@  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);