IMA: Define a new hook to measure the kexec boot command line arguments

Currently during soft reboot(kexec_file_load) boot command line
arguments are not measured. Define hooks needed to measure kexec
command line arguments during soft reboot(kexec_file_load).

- A new ima hook ima_kexec_cmdline is defined to be called by the
kexec code.
- A new function process_buffer_measurement is defined to measure
the buffer hash into the IMA measurement list.
- A new func policy KEXEC_CMDLINE is defined to control the
 measurement.

Signed-off-by: Prakhar Srivastava <prsriva02@gmail.com>
Signed-off-by: Mimi Zohar <zohar@linux.ibm.com>

1 files changed, 72 insertions, 0 deletions

diff --git a/security/integrity/ima/ima_main.c b/security/integrity/ima/ima_main.c
index a7e7e2d7224c..2507bee1b762 100644
--- a/security/integrity/ima/ima_main.c
+++ b/security/integrity/ima/ima_main.c
@@ -609,6 +609,78 @@ int ima_load_data(enum kernel_load_data_id id)
 	return 0;
 }
 
+/*
+ * process_buffer_measurement - Measure the buffer to ima log.
+ * @buf: pointer to the buffer that needs to be added to the log.
+ * @size: size of buffer(in bytes).
+ * @eventname: event name to be used for the buffer entry.
+ * @cred: a pointer to a credentials structure for user validation.
+ * @secid: the secid of the task to be validated.
+ *
+ * Based on policy, the buffer is measured into the ima log.
+ */
+static void process_buffer_measurement(const void *buf, int size,
+				       const char *eventname,
+				       const struct cred *cred, u32 secid)
+{
+	int ret = 0;
+	struct ima_template_entry *entry = NULL;
+	struct integrity_iint_cache iint = {};
+	struct ima_event_data event_data = {.iint = &iint,
+					    .filename = eventname};
+	struct ima_template_desc *template_desc = NULL;
+	struct {
+		struct ima_digest_data hdr;
+		char digest[IMA_MAX_DIGEST_SIZE];
+	} hash = {};
+	int violation = 0;
+	int pcr = CONFIG_IMA_MEASURE_PCR_IDX;
+	int action = 0;
+
+	action = ima_get_action(NULL, cred, secid, 0, KEXEC_CMDLINE, &pcr,
+				&template_desc);
+	if (!(action & IMA_MEASURE))
+		return;
+
+	iint.ima_hash = &hash.hdr;
+	iint.ima_hash->algo = ima_hash_algo;
+	iint.ima_hash->length = hash_digest_size[ima_hash_algo];
+
+	ret = ima_calc_buffer_hash(buf, size, iint.ima_hash);
+	if (ret < 0)
+		goto out;
+
+	ret = ima_alloc_init_template(&event_data, &entry, template_desc);
+	if (ret < 0)
+		goto out;
+
+	ret = ima_store_template(entry, violation, NULL, buf, pcr);
+
+	if (ret < 0)
+		ima_free_template_entry(entry);
+
+out:
+	return;
+}
+
+/**
+ * ima_kexec_cmdline - measure kexec cmdline boot args
+ * @buf: pointer to buffer
+ * @size: size of buffer
+ *
+ * Buffers can only be measured, not appraised.
+ */
+void ima_kexec_cmdline(const void *buf, int size)
+{
+	u32 secid;
+
+	if (buf && size != 0) {
+		security_task_getsecid(current, &secid);
+		process_buffer_measurement(buf, size, "kexec-cmdline",
+					   current_cred(), secid);
+	}
+}
+
 static int __init init_ima(void)
 {
 	int error;