ima: define a canonical binary_runtime_measurements list format

The IMA binary_runtime_measurements list is currently in platform native
format.

To allow restoring a measurement list carried across kexec with a
different endianness than the targeted kernel, this patch defines
little-endian as the canonical format.  For big endian systems wanting
to save/restore the measurement list from a system with a different
endianness, a new boot command line parameter named "ima_canonical_fmt"
is defined.

Considerations: use of the "ima_canonical_fmt" boot command line option
will break existing userspace applications on big endian systems
expecting the binary_runtime_measurements list to be in platform native
format.

Link: http://lkml.kernel.org/r/1480554346-29071-10-git-send-email-zohar@linux.vnet.ibm.com
Signed-off-by: Mimi Zohar <zohar@linux.vnet.ibm.com>
Acked-by: Dmitry Kasatkin <dmitry.kasatkin@gmail.com>
Cc: Thiago Jung Bauermann <bauerman@linux.vnet.ibm.com>
Cc: "Eric W. Biederman" <ebiederm@xmission.com>
Cc: Andreas Steffen <andreas.steffen@strongswan.org>
Cc: Josh Sklar <sklar@linux.vnet.ibm.com>
Cc: Dave Young <dyoung@redhat.com>
Cc: Vivek Goyal <vgoyal@redhat.com>
Cc: Baoquan He <bhe@redhat.com>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Stewart Smith <stewart@linux.vnet.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

security/integrity/ima/ima_fs.c

@@ -28,6 +28,16 @@
 
 static DEFINE_MUTEX(ima_write_mutex);
 
+bool ima_canonical_fmt;
+static int __init default_canonical_fmt_setup(char *str)
+{
+#ifdef __BIG_ENDIAN
+	ima_canonical_fmt = 1;
+#endif
+	return 1;
+}
+__setup("ima_canonical_fmt", default_canonical_fmt_setup);
+
 static int valid_policy = 1;
 #define TMPBUFLEN 12
 static ssize_t ima_show_htable_value(char __user *buf, size_t count,
@@ -122,7 +132,7 @@ int ima_measurements_show(struct seq_file *m, void *v)
 	struct ima_queue_entry *qe = v;
 	struct ima_template_entry *e;
 	char *template_name;
-	int namelen;
+	u32 pcr, namelen, template_data_len; /* temporary fields */
 	bool is_ima_template = false;
 	int i;
 
@@ -139,25 +149,29 @@ int ima_measurements_show(struct seq_file *m, void *v)
 	 * PCR used defaults to the same (config option) in
 	 * little-endian format, unless set in policy
 	 */
-	ima_putc(m, &e->pcr, sizeof(e->pcr));
+	pcr = !ima_canonical_fmt ? e->pcr : cpu_to_le32(e->pcr);
+	ima_putc(m, &pcr, sizeof(e->pcr));
 
 	/* 2nd: template digest */
 	ima_putc(m, e->digest, TPM_DIGEST_SIZE);
 
 	/* 3rd: template name size */
-	namelen = strlen(template_name);
+	namelen = !ima_canonical_fmt ? strlen(template_name) :
+		cpu_to_le32(strlen(template_name));
 	ima_putc(m, &namelen, sizeof(namelen));
 
 	/* 4th:  template name */
-	ima_putc(m, template_name, namelen);
+	ima_putc(m, template_name, strlen(template_name));
 
 	/* 5th:  template length (except for 'ima' template) */
 	if (strcmp(template_name, IMA_TEMPLATE_IMA_NAME) == 0)
 		is_ima_template = true;
 
-	if (!is_ima_template)
-		ima_putc(m, &e->template_data_len,
-			 sizeof(e->template_data_len));
+	if (!is_ima_template) {
+		template_data_len = !ima_canonical_fmt ? e->template_data_len :
+			cpu_to_le32(e->template_data_len);
+		ima_putc(m, &template_data_len, sizeof(e->template_data_len));
+	}
 
 	/* 6th:  template specific data */
 	for (i = 0; i < e->template_desc->num_fields; i++) {