IMA: extend critical data hook to limit the measurement based on a label

The IMA hook ima_measure_critical_data() does not support a way to
specify the source of the critical data provider.  Thus, the data
measurement cannot be constrained based on the data source label
in the IMA policy.

Extend the IMA hook ima_measure_critical_data() to support passing
the data source label as an input parameter, so that the policy rule can
be used to limit the measurements based on the label.
Signed-off-by: Tushar Sugandhi <tusharsu@linux.microsoft.com>
Reviewed-by: Tyler Hicks <tyhicks@linux.microsoft.com>
Signed-off-by: Mimi Zohar <zohar@linux.ibm.com>

include/linux/ima.h

@@ -31,7 +31,8 @@ extern void ima_post_path_mknod(struct dentry *dentry);
 extern int ima_file_hash(struct file *file, char *buf, size_t buf_size);
 extern int ima_inode_hash(struct inode *inode, char *buf, size_t buf_size);
 extern void ima_kexec_cmdline(int kernel_fd, const void *buf, int size);
-extern void ima_measure_critical_data(const char *event_name,
+extern void ima_measure_critical_data(const char *event_label,
+				      const char *event_name,
 				      const void *buf, size_t buf_len,
 				      bool hash);
 
@@ -132,9 +133,11 @@ static inline int ima_inode_hash(struct inode *inode, char *buf, size_t buf_size
 
 static inline void ima_kexec_cmdline(int kernel_fd, const void *buf, int size) {}
 
-static inline void ima_measure_critical_data(const char *event_name,
+static inline void ima_measure_critical_data(const char *event_label,
+					     const char *event_name,
 					     const void *buf, size_t buf_len,
 					     bool hash) {}
+
 #endif /* CONFIG_IMA */
 
 #ifndef CONFIG_IMA_KEXEC

security/integrity/ima/ima_main.c

@@ -945,6 +945,7 @@ void ima_kexec_cmdline(int kernel_fd, const void *buf, int size)
 
 /**
  * ima_measure_critical_data - measure kernel integrity critical data
+ * @event_label: unique event label for grouping and limiting critical data
  * @event_name: event name for the record in the IMA measurement list
  * @buf: pointer to buffer data
  * @buf_len: length of buffer data (in bytes)
@@ -955,15 +956,16 @@ void ima_kexec_cmdline(int kernel_fd, const void *buf, int size)
  * structures, policies, and states stored in kernel memory that can
  * impact the integrity of the system.
  */
-void ima_measure_critical_data(const char *event_name,
+void ima_measure_critical_data(const char *event_label,
+			       const char *event_name,
 			       const void *buf, size_t buf_len,
 			       bool hash)
 {
-	if (!event_name || !buf || !buf_len)
+	if (!event_name || !event_label || !buf || !buf_len)
 		return;
 
 	process_buffer_measurement(NULL, buf, buf_len, event_name,
-				   CRITICAL_DATA, 0, NULL,
+				   CRITICAL_DATA, 0, event_label,
 				   hash);
 }