[PATCH 1/3] ima: measure other types of data

[Mimi Zohar <zohar@linux.vnet.ibm.com>]

In addition to files, other data (eg. boot command line) should be
included in the measurement list to attest to the integrity of a running
system.  A new IMA hook named ima_buffer_check() calculates and includes
the buffer hash in the measurement list.  Callers of this hook provide
the buffer, buffer length and a buffer identifier.

Signed-off-by: Mimi Zohar <zohar@linux.vnet.ibm.com>
---
 include/linux/ima.h                 | 11 +++++
 security/integrity/ima/Makefile     |  2 +-
 security/integrity/ima/ima.h        |  2 +
 security/integrity/ima/ima_buffer.c | 82 +++++++++++++++++++++++++++++++++++++
 security/integrity/ima/ima_policy.c | 26 ++++++++++++
 5 files changed, 122 insertions(+), 1 deletion(-)
 create mode 100644 security/integrity/ima/ima_buffer.c

diff --git a/include/linux/ima.h b/include/linux/ima.h
index 0eb7c2e..01319b3 100644
--- a/include/linux/ima.h
+++ b/include/linux/ima.h
@@ -13,6 +13,10 @@
 #include <linux/fs.h>
 struct linux_binprm;
 
+enum ima_buffer_id {
+	MEASURING_MAX_BUFFER_ID
+};
+
 #ifdef CONFIG_IMA
 extern int ima_bprm_check(struct linux_binprm *bprm);
 extern int ima_file_check(struct file *file, int mask, int opened);
@@ -22,6 +26,8 @@ extern int ima_read_file(struct file *file, enum kernel_read_file_id id);
 extern int ima_post_read_file(struct file *file, void *buf, loff_t size,
 			      enum kernel_read_file_id id);
 extern void ima_post_path_mknod(struct dentry *dentry);
+extern void ima_buffer_check(void *buf, loff_t size,
+			     enum ima_buffer_id buffer_id);
 
 #else
 static inline int ima_bprm_check(struct linux_binprm *bprm)
@@ -60,6 +66,11 @@ static inline void ima_post_path_mknod(struct dentry *dentry)
 	return;
 }
 
+static inline void ima_buffer_check(void *buf, loff_t size,
+				    enum ima_buffer_id buffer_id)
+{
+	return;
+}
 #endif /* CONFIG_IMA */
 
 #ifdef CONFIG_IMA_APPRAISE
diff --git a/security/integrity/ima/Makefile b/security/integrity/ima/Makefile
index 9aeaeda..c34599f 100644
--- a/security/integrity/ima/Makefile
+++ b/security/integrity/ima/Makefile
@@ -6,6 +6,6 @@
 obj-$(CONFIG_IMA) += ima.o
 
 ima-y := ima_fs.o ima_queue.o ima_init.o ima_main.o ima_crypto.o ima_api.o \
-	 ima_policy.o ima_template.o ima_template_lib.o
+	 ima_policy.o ima_template.o ima_template_lib.o ima_buffer.o
 ima-$(CONFIG_IMA_APPRAISE) += ima_appraise.o
 obj-$(CONFIG_IMA_BLACKLIST_KEYRING) += ima_mok.o
diff --git a/security/integrity/ima/ima.h b/security/integrity/ima/ima.h
index db25f54..cc2e77b 100644
--- a/security/integrity/ima/ima.h
+++ b/security/integrity/ima/ima.h
@@ -154,6 +154,8 @@ enum ima_hooks {
 	MAX_CHECK
 };
 
+int ima_match_buffer_id(enum ima_hooks func, int *pcr);
+
 /* LIM API function definitions */
 int ima_get_action(struct inode *inode, int mask,
 		   enum ima_hooks func, int *pcr);
diff --git a/security/integrity/ima/ima_buffer.c b/security/integrity/ima/ima_buffer.c
new file mode 100644
index 0000000..84c9494
--- /dev/null
+++ b/security/integrity/ima/ima_buffer.c
@@ -0,0 +1,82 @@
+/*
+ * Copyright (C) 2016 IBM Corporation
+ *
+ * Author:
+ * Mimi Zohar <zohar@us.ibm.com>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, version 2 of the License.
+ */
+#include <linux/uaccess.h>
+#include <linux/module.h>
+#include <linux/ima.h>
+
+#include "ima.h"
+
+struct buffer_idmap {
+	enum ima_hooks func;
+	char *buf;
+};
+
+static struct buffer_idmap _idmap[MEASURING_MAX_BUFFER_ID] = {
+};
+
+static void process_buffer_measurement(void *buf, loff_t size,
+				       enum ima_buffer_id buffer_id, int pcr)
+{
+	struct {
+		struct ima_digest_data hdr;
+		char digest[IMA_MAX_DIGEST_SIZE];
+	} hash;
+	struct ima_template_entry *entry;
+	struct integrity_iint_cache tmp_iint, *iint = &tmp_iint;
+	struct ima_event_data event_data = {iint, NULL, NULL, NULL, 0, NULL};
+	int violation = 0;
+	int result;
+
+	memset(&hash, 0, sizeof(hash));
+	hash.hdr.algo = ima_hash_algo;
+	result = ima_calc_buffer_hash(buf, size, &hash.hdr);
+	if (result < 0) {
+		pr_debug("failed calculating buffer hash\n");
+		return;
+	}
+
+	iint->ima_hash = &hash.hdr;
+	event_data.filename = _idmap[buffer_id].buf;
+	result = ima_alloc_init_template(&event_data, &entry);
+	if (result < 0) {
+		pr_debug("failed allocating template\n");
+		return;
+	}
+
+	result = ima_store_template(entry, violation, NULL,
+				    event_data.filename, pcr);
+	if (result < 0) {
+		pr_debug("failed storing buffer measurement\n");
+		ima_free_template_entry(entry);
+	}
+}
+
+/**
+ * ima_buffer_check - based on policy, collect & store buffer measurement
+ * @buf: pointer to buffer
+ * @size: size of buffer
+ * @buffer_id: caller identifier
+ *
+ * Buffers can only be measured, not appraised.
+ */
+void ima_buffer_check(void *buf, loff_t size, enum ima_buffer_id buffer_id)
+{
+	int pcr = CONFIG_IMA_MEASURE_PCR_IDX;
+
+	if (buffer_id > MEASURING_MAX_BUFFER_ID)
+		return;
+
+	if (!ima_match_buffer_id(_idmap[buffer_id].func, &pcr))
+		return;
+
+	process_buffer_measurement(buf, size, buffer_id, pcr);
+}
+EXPORT_SYMBOL_GPL(ima_buffer_check);
diff --git a/security/integrity/ima/ima_policy.c b/security/integrity/ima/ima_policy.c
index aed47b7..521d612 100644
--- a/security/integrity/ima/ima_policy.c
+++ b/security/integrity/ima/ima_policy.c
@@ -370,6 +370,32 @@ int ima_match_policy(struct inode *inode, enum ima_hooks func, int mask,
 	return action;
 }
 
+/**
+ * ima_match_buffer_id - decision based on policy
+ * @buffer_id: IMA buffer identifier
+ *
+ * Measure decision based the buffer identifier's existence in policy.
+ * Without an inode, buffers can only be measured, not appraised.
+ */
+int ima_match_buffer_id(enum ima_hooks func, int *pcr)
+{
+	struct ima_rule_entry *entry;
+	int result = 0;
+
+	rcu_read_lock();
+	list_for_each_entry_rcu(entry, ima_rules, list) {
+		if ((entry->action == MEASURE) && (entry->flags & IMA_FUNC) &&
+		     (entry->func == func)) {
+			if (entry->flags & IMA_PCR)
+				*pcr = entry->pcr;
+			result = 1;
+		}
+	}
+	rcu_read_unlock();
+
+	return result;
+}
+
 /*
  * Initialize the ima_policy_flag variable based on the currently
  * loaded policy.  Based on this flag, the decision to short circuit
-- 
2.1.0