[PATCH v27 03/25] LSM: provide lsm name and id slot mappings

From: Casey Schaufler <casey@schaufler-ca.com>
To: casey.schaufler@intel.com, jmorris@namei.org,
	linux-security-module@vger.kernel.org, selinux@vger.kernel.org
Cc: john.johansen@canonical.com, linux-kernel@vger.kernel.org,
	linux-audit@redhat.com, sds@tycho.nsa.gov
Subject: [PATCH v27 03/25] LSM: provide lsm name and id slot mappings
Date: Thu, 10 Jun 2021 17:04:13 -0700	[thread overview]
Message-ID: <20210611000435.36398-4-casey@schaufler-ca.com> (raw)
In-Reply-To: <20210611000435.36398-1-casey@schaufler-ca.com>

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 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 473b49971aab..6387107e4014 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.
@@ -497,6 +541,7 @@ 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);
-- 
2.29.2

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