ima: Define new template field imode

This patch defines the new template field imode, which includes the
inode mode. It can be used by a remote verifier to verify the EVM portable
signature, if it was included with the template fields sig or evmsig.

Signed-off-by: Roberto Sassu <roberto.sassu@huawei.com>
Signed-off-by: Mimi Zohar <zohar@linux.ibm.com>

Author: robertosassu

Documentation/security/IMA-templates.rst

@@ -77,6 +77,7 @@ descriptors by adding their identifier to the format string
  - 'evmsig': the EVM portable signature;
  - 'iuid': the inode UID;
  - 'igid': the inode GID;
+ - 'imode': the inode mode;
 
 
 Below, there is the list of defined template descriptors:

security/integrity/ima/ima_template.c

@@ -51,6 +51,8 @@ static const struct ima_template_field supported_fields[] = {
 	 .field_show = ima_show_template_uint},
 	{.field_id = "igid", .field_init = ima_eventinodegid_init,
 	 .field_show = ima_show_template_uint},
+	{.field_id = "imode", .field_init = ima_eventinodemode_init,
+	 .field_show = ima_show_template_uint},
 };
 
 /*

security/integrity/ima/ima_template_lib.c

@@ -596,3 +596,25 @@ int ima_eventinodegid_init(struct ima_event_data *event_data,
 {
 	return ima_eventinodedac_init_common(event_data, field_data, false);
 }
+
+/*
+ *  ima_eventinodemode_init - include the inode mode as part of the template
+ *  data
+ */
+int ima_eventinodemode_init(struct ima_event_data *event_data,
+			    struct ima_field_data *field_data)
+{
+	struct inode *inode;
+	umode_t mode;
+
+	if (!event_data->file)
+		return 0;
+
+	inode = file_inode(event_data->file);
+	mode = inode->i_mode;
+	if (ima_canonical_fmt)
+		mode = cpu_to_le16(mode);
+
+	return ima_write_template_field_data((char *)&mode, sizeof(mode),
+					     DATA_FMT_UINT, field_data);
+}

security/integrity/ima/ima_template_lib.h

@@ -54,4 +54,6 @@ int ima_eventinodeuid_init(struct ima_event_data *event_data,
 			   struct ima_field_data *field_data);
 int ima_eventinodegid_init(struct ima_event_data *event_data,
 			   struct ima_field_data *field_data);
+int ima_eventinodemode_init(struct ima_event_data *event_data,
+			    struct ima_field_data *field_data);
 #endif /* __LINUX_IMA_TEMPLATE_LIB_H */