integrity: IMA as an integrity service provider

IMA provides hardware (TPM) based measurement and attestation for
file measurements. As the Trusted Computing (TPM) model requires,
IMA measures all files before they are accessed in any way (on the
integrity_bprm_check, integrity_path_check and integrity_file_mmap
hooks), and commits the measurements to the TPM. Once added to the
TPM, measurements can not be removed.

In addition, IMA maintains a list of these file measurements, which
can be used to validate the aggregate value stored in the TPM.  The
TPM can sign these measurements, and thus the system can prove, to
itself and to a third party, the system's integrity in a way that
cannot be circumvented by malicious or compromised software.

- alloc ima_template_entry before calling ima_store_template()
- log ima_add_boot_aggregate() failure
- removed unused IMA_TEMPLATE_NAME_LEN
- replaced hard coded string length with #define name

Signed-off-by: Mimi Zohar <zohar@us.ibm.com>
Signed-off-by: James Morris <jmorris@namei.org>

1 files changed, 135 insertions, 0 deletions

diff --git a/security/integrity/ima/ima.h b/security/integrity/ima/ima.h
new file mode 100644
index 0000000..bfa72ed
--- /dev/null
+++ b/security/integrity/ima/ima.h
@@ -0,0 +1,135 @@
+/*
+ * Copyright (C) 2005,2006,2007,2008 IBM Corporation
+ *
+ * Authors:
+ * Reiner Sailer <sailer@watson.ibm.com>
+ * 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.
+ *
+ * File: ima.h
+ *	internal Integrity Measurement Architecture (IMA) definitions
+ */
+
+#ifndef __LINUX_IMA_H
+#define __LINUX_IMA_H
+
+#include <linux/types.h>
+#include <linux/crypto.h>
+#include <linux/security.h>
+#include <linux/hash.h>
+#include <linux/tpm.h>
+#include <linux/audit.h>
+
+enum ima_show_type { IMA_SHOW_BINARY, IMA_SHOW_ASCII };
+enum tpm_pcrs { TPM_PCR0 = 0, TPM_PCR8 = 8 };
+
+/* digest size for IMA, fits SHA1 or MD5 */
+#define IMA_DIGEST_SIZE		20
+#define IMA_EVENT_NAME_LEN_MAX	255
+
+#define IMA_HASH_BITS 9
+#define IMA_MEASURE_HTABLE_SIZE (1 << IMA_HASH_BITS)
+
+/* set during initialization */
+extern int ima_initialized;
+extern int ima_used_chip;
+extern char *ima_hash;
+
+/* IMA inode template definition */
+struct ima_template_data {
+	u8 digest[IMA_DIGEST_SIZE];	/* sha1/md5 measurement hash */
+	char file_name[IMA_EVENT_NAME_LEN_MAX + 1];	/* name + \0 */
+};
+
+struct ima_template_entry {
+	u8 digest[IMA_DIGEST_SIZE];	/* sha1 or md5 measurement hash */
+	char *template_name;
+	int template_len;
+	struct ima_template_data template;
+};
+
+struct ima_queue_entry {
+	struct hlist_node hnext;	/* place in hash collision list */
+	struct list_head later;		/* place in ima_measurements list */
+	struct ima_template_entry *entry;
+};
+extern struct list_head ima_measurements;	/* list of all measurements */
+
+/* declarations */
+void integrity_audit_msg(int audit_msgno, struct inode *inode,
+			 const unsigned char *fname, const char *op,
+			 const char *cause, int result, int info);
+
+/* Internal IMA function definitions */
+void ima_iintcache_init(void);
+int ima_init(void);
+int ima_add_template_entry(struct ima_template_entry *entry, int violation,
+			   const char *op, struct inode *inode);
+int ima_calc_hash(struct file *file, char *digest);
+int ima_calc_template_hash(int template_len, void *template, char *digest);
+int ima_calc_boot_aggregate(char *digest);
+void ima_add_violation(struct inode *inode, const unsigned char *filename,
+		       const char *op, const char *cause);
+
+/*
+ * used to protect h_table and sha_table
+ */
+extern spinlock_t ima_queue_lock;
+
+struct ima_h_table {
+	atomic_long_t len;	/* number of stored measurements in the list */
+	atomic_long_t violations;
+	struct hlist_head queue[IMA_MEASURE_HTABLE_SIZE];
+};
+extern struct ima_h_table ima_htable;
+
+static inline unsigned long ima_hash_key(u8 *digest)
+{
+	return hash_long(*digest, IMA_HASH_BITS);
+}
+
+/* iint cache flags */
+#define IMA_MEASURED		1
+
+/* integrity data associated with an inode */
+struct ima_iint_cache {
+	u64 version;		/* track inode changes */
+	unsigned long flags;
+	u8 digest[IMA_DIGEST_SIZE];
+	struct mutex mutex;	/* protects: version, flags, digest */
+	long readcount;		/* measured files readcount */
+	long writecount;	/* measured files writecount */
+	struct kref refcount;	/* ima_iint_cache reference count */
+	struct rcu_head rcu;
+};
+
+/* LIM API function definitions */
+int ima_must_measure(struct ima_iint_cache *iint, struct inode *inode,
+		     int mask, int function);
+int ima_collect_measurement(struct ima_iint_cache *iint, struct file *file);
+void ima_store_measurement(struct ima_iint_cache *iint, struct file *file,
+			   const unsigned char *filename);
+int ima_store_template(struct ima_template_entry *entry, int violation,
+		       struct inode *inode);
+
+/* radix tree calls to lookup, insert, delete
+ * integrity data associated with an inode.
+ */
+struct ima_iint_cache *ima_iint_insert(struct inode *inode);
+struct ima_iint_cache *ima_iint_find_get(struct inode *inode);
+struct ima_iint_cache *ima_iint_find_insert_get(struct inode *inode);
+void ima_iint_delete(struct inode *inode);
+void iint_free(struct kref *kref);
+void iint_rcu_free(struct rcu_head *rcu);
+
+/* IMA policy related functions */
+enum ima_hooks { PATH_CHECK = 1, FILE_MMAP, BPRM_CHECK };
+
+int ima_match_policy(struct inode *inode, enum ima_hooks func, int mask);
+void ima_init_policy(void);
+void ima_update_policy(void);
+#endif