security/integrity/ima/ima_main.c - maze/linux - Git at Google

 /*
  * Copyright (C) 2005,2006,2007,2008 IBM Corporation
  *
  * Authors:
  * Reiner Sailer <sailer@watson.ibm.com>
  * Serge Hallyn <serue@us.ibm.com>
  * Kylene Hall <kylene@us.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_main.c
  *	implements the IMA hooks: ima_bprm_check, ima_file_mmap,
  *	and ima_path_check.
  */
 #include <linux/module.h>
 #include <linux/file.h>
 #include <linux/binfmts.h>
 #include <linux/mount.h>
 #include <linux/mman.h>

 #include "ima.h"

 int ima_initialized;

 char *ima_hash = "sha1";
 static int __init hash_setup(char *str)
 {
 	if (strncmp(str, "md5", 3) == 0)
 		ima_hash = "md5";
 	return 1;
 }
 __setup("ima_hash=", hash_setup);

 struct ima_imbalance {
 	struct hlist_node node;
 	unsigned long fsmagic;
 };

 /*
  * ima_limit_imbalance - emit one imbalance message per filesystem type
  *
  * Maintain list of filesystem types that do not measure files properly.
  * Return false if unknown, true if known.
  */
 static bool ima_limit_imbalance(struct file *file)
 {
 	static DEFINE_SPINLOCK(ima_imbalance_lock);
 	static HLIST_HEAD(ima_imbalance_list);

 	struct super_block *sb = file->f_dentry->d_sb;
 	struct ima_imbalance *entry;
 	struct hlist_node *node;
 	bool found = false;

 	rcu_read_lock();
 	hlist_for_each_entry_rcu(entry, node, &ima_imbalance_list, node) {
 		if (entry->fsmagic == sb->s_magic) {
 			found = true;
 			break;
 		}
 	}
 	rcu_read_unlock();
 	if (found)
 		goto out;

 	entry = kmalloc(sizeof(*entry), GFP_NOFS);
 	if (!entry)
 		goto out;
 	entry->fsmagic = sb->s_magic;
 	spin_lock(&ima_imbalance_lock);
 	/*
 	 * we could have raced and something else might have added this fs
 	 * to the list, but we don't really care
 	 */
 	hlist_add_head_rcu(&entry->node, &ima_imbalance_list);
 	spin_unlock(&ima_imbalance_lock);
 	printk(KERN_INFO "IMA: unmeasured files on fsmagic: %lX\n",
 	       entry->fsmagic);
 out:
 	return found;
 }

 /* ima_read_write_check - reflect possible reading/writing errors in the PCR.
  *
  * When opening a file for read, if the file is already open for write,
  * the file could change, resulting in a file measurement error.
  *
  * Opening a file for write, if the file is already open for read, results
  * in a time of measure, time of use (ToMToU) error.
  *
  * In either case invalidate the PCR.
  */
 enum iint_pcr_error { TOMTOU, OPEN_WRITERS };
 static void ima_read_write_check(enum iint_pcr_error error,
 				 struct ima_iint_cache *iint,
 				 struct inode *inode,
 				 const unsigned char *filename)
 {
 	switch (error) {
 	case TOMTOU:
 		if (iint->readcount > 0)
 			ima_add_violation(inode, filename, "invalid_pcr",
 					  "ToMToU");
 		break;
 	case OPEN_WRITERS:
 		if (iint->writecount > 0)
 			ima_add_violation(inode, filename, "invalid_pcr",
 					  "open_writers");
 		break;
 	}
 }

 /*
  * Update the counts given an fmode_t
  */
 static void ima_inc_counts(struct ima_iint_cache *iint, fmode_t mode)
 {
 	BUG_ON(!mutex_is_locked(&iint->mutex));

 	iint->opencount++;
 	if ((mode & (FMODE_READ | FMODE_WRITE)) == FMODE_READ)
 		iint->readcount++;
 	if (mode & FMODE_WRITE)
 		iint->writecount++;
 }

 /*
  * ima_counts_get - increment file counts
  *
  * Maintain read/write counters for all files, but only
  * invalidate the PCR for measured files:
  * 	- Opening a file for write when already open for read,
  *	  results in a time of measure, time of use (ToMToU) error.
  *	- Opening a file for read when already open for write,
  * 	  could result in a file measurement error.
  *
  */
 void ima_counts_get(struct file *file)
 {
 	struct dentry *dentry = file->f_path.dentry;
 	struct inode *inode = dentry->d_inode;
 	fmode_t mode = file->f_mode;
 	struct ima_iint_cache *iint;
 	int rc;

 	if (!ima_initialized || !S_ISREG(inode->i_mode))
 		return;
 	iint = ima_iint_find_get(inode);
 	if (!iint)
 		return;
 	mutex_lock(&iint->mutex);
 	rc = ima_must_measure(iint, inode, MAY_READ, PATH_CHECK);
 	if (rc < 0)
 		goto out;

 	if (mode & FMODE_WRITE) {
 		ima_read_write_check(TOMTOU, iint, inode, dentry->d_name.name);
 		goto out;
 	}
 	ima_read_write_check(OPEN_WRITERS, iint, inode, dentry->d_name.name);
 out:
 	ima_inc_counts(iint, file->f_mode);
 	mutex_unlock(&iint->mutex);

 	kref_put(&iint->refcount, iint_free);
 }

 /*
  * Decrement ima counts
  */
 static void ima_dec_counts(struct ima_iint_cache *iint, struct inode *inode,
 			   struct file *file)
 {
 	mode_t mode = file->f_mode;
 	BUG_ON(!mutex_is_locked(&iint->mutex));

 	iint->opencount--;
 	if ((mode & (FMODE_READ | FMODE_WRITE)) == FMODE_READ)
 		iint->readcount--;
 	if (mode & FMODE_WRITE) {
 		iint->writecount--;
 		if (iint->writecount == 0) {
 			if (iint->version != inode->i_version)
 				iint->flags &= ~IMA_MEASURED;
 		}
 	}

 	if (((iint->opencount < 0) ||
 	     (iint->readcount < 0) ||
 	     (iint->writecount < 0)) &&
 	    !ima_limit_imbalance(file)) {
 		printk(KERN_INFO "%s: open/free imbalance (r:%ld w:%ld o:%ld)\n",
 		       __FUNCTION__, iint->readcount, iint->writecount,
 		       iint->opencount);
 		dump_stack();
 	}
 }

 /**
  * ima_file_free - called on __fput()
  * @file: pointer to file structure being freed
  *
  * Flag files that changed, based on i_version;
  * and decrement the iint readcount/writecount.
  */
 void ima_file_free(struct file *file)
 {
 	struct inode *inode = file->f_dentry->d_inode;
 	struct ima_iint_cache *iint;

 	if (!ima_initialized || !S_ISREG(inode->i_mode))
 		return;
 	iint = ima_iint_find_get(inode);
 	if (!iint)
 		return;

 	mutex_lock(&iint->mutex);
 	ima_dec_counts(iint, inode, file);
 	mutex_unlock(&iint->mutex);
 	kref_put(&iint->refcount, iint_free);
 }

 static int process_measurement(struct file *file, const unsigned char *filename,
 			       int mask, int function)
 {
 	struct inode *inode = file->f_dentry->d_inode;
 	struct ima_iint_cache *iint;
 	int rc;

 	if (!ima_initialized || !S_ISREG(inode->i_mode))
 		return 0;
 	iint = ima_iint_find_get(inode);
 	if (!iint)
 		return -ENOMEM;

 	mutex_lock(&iint->mutex);
 	rc = ima_must_measure(iint, inode, mask, function);
 	if (rc != 0)
 		goto out;

 	rc = ima_collect_measurement(iint, file);
 	if (!rc)
 		ima_store_measurement(iint, file, filename);
 out:
 	mutex_unlock(&iint->mutex);
 	kref_put(&iint->refcount, iint_free);
 	return rc;
 }

 /**
  * ima_file_mmap - based on policy, collect/store measurement.
  * @file: pointer to the file to be measured (May be NULL)
  * @prot: contains the protection that will be applied by the kernel.
  *
  * Measure files being mmapped executable based on the ima_must_measure()
  * policy decision.
  *
  * Return 0 on success, an error code on failure.
  * (Based on the results of appraise_measurement().)
  */
 int ima_file_mmap(struct file *file, unsigned long prot)
 {
 	int rc;

 	if (!file)
 		return 0;
 	if (prot & PROT_EXEC)
 		rc = process_measurement(file, file->f_dentry->d_name.name,
 					 MAY_EXEC, FILE_MMAP);
 	return 0;
 }

 /**
  * ima_bprm_check - based on policy, collect/store measurement.
  * @bprm: contains the linux_binprm structure
  *
  * The OS protects against an executable file, already open for write,
  * from being executed in deny_write_access() and an executable file,
  * already open for execute, from being modified in get_write_access().
  * So we can be certain that what we verify and measure here is actually
  * what is being executed.
  *
  * Return 0 on success, an error code on failure.
  * (Based on the results of appraise_measurement().)
  */
 int ima_bprm_check(struct linux_binprm *bprm)
 {
 	int rc;

 	rc = process_measurement(bprm->file, bprm->filename,
 				 MAY_EXEC, BPRM_CHECK);
 	return 0;
 }

 /**
  * ima_path_check - based on policy, collect/store measurement.
  * @file: pointer to the file to be measured
  * @mask: contains MAY_READ, MAY_WRITE or MAY_EXECUTE
  *
  * Measure files based on the ima_must_measure() policy decision.
  *
  * Always return 0 and audit dentry_open failures.
  * (Return code will be based upon measurement appraisal.)
  */
 int ima_path_check(struct file *file, int mask)
 {
 	int rc;

 	rc = process_measurement(file, file->f_dentry->d_name.name,
 				 mask & (MAY_READ | MAY_WRITE | MAY_EXEC),
 				 PATH_CHECK);
 	return 0;
 }
 EXPORT_SYMBOL_GPL(ima_path_check);

 static int __init init_ima(void)
 {
 	int error;

 	ima_iintcache_init();
 	error = ima_init();
 	ima_initialized = 1;
 	return error;
 }

 static void __exit cleanup_ima(void)
 {
 	ima_cleanup();
 }

 late_initcall(init_ima);	/* Start IMA after the TPM is available */

 MODULE_DESCRIPTION("Integrity Measurement Architecture");
 MODULE_LICENSE("GPL");
	/*
	* Copyright (C) 2005,2006,2007,2008 IBM Corporation
	*
	* Authors:
	* Reiner Sailer <sailer@watson.ibm.com>
	* Serge Hallyn <serue@us.ibm.com>
	* Kylene Hall <kylene@us.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_main.c
	* implements the IMA hooks: ima_bprm_check, ima_file_mmap,
	* and ima_path_check.
	*/
	#include <linux/module.h>
	#include <linux/file.h>
	#include <linux/binfmts.h>
	#include <linux/mount.h>
	#include <linux/mman.h>

	#include "ima.h"

	int ima_initialized;

	char *ima_hash = "sha1";
	static int __init hash_setup(char *str)
	{
	if (strncmp(str, "md5", 3) == 0)
	ima_hash = "md5";
	return 1;
	}
	__setup("ima_hash=", hash_setup);

	struct ima_imbalance {
	struct hlist_node node;
	unsigned long fsmagic;
	};

	/*
	* ima_limit_imbalance - emit one imbalance message per filesystem type
	*
	* Maintain list of filesystem types that do not measure files properly.
	* Return false if unknown, true if known.
	*/
	static bool ima_limit_imbalance(struct file *file)
	{
	static DEFINE_SPINLOCK(ima_imbalance_lock);
	static HLIST_HEAD(ima_imbalance_list);

	struct super_block *sb = file->f_dentry->d_sb;
	struct ima_imbalance *entry;
	struct hlist_node *node;
	bool found = false;

	rcu_read_lock();
	hlist_for_each_entry_rcu(entry, node, &ima_imbalance_list, node) {
	if (entry->fsmagic == sb->s_magic) {
	found = true;
	break;
	}
	}
	rcu_read_unlock();
	if (found)
	goto out;

	entry = kmalloc(sizeof(*entry), GFP_NOFS);
	if (!entry)
	goto out;
	entry->fsmagic = sb->s_magic;
	spin_lock(&ima_imbalance_lock);
	/*
	* we could have raced and something else might have added this fs
	* to the list, but we don't really care
	*/
	hlist_add_head_rcu(&entry->node, &ima_imbalance_list);
	spin_unlock(&ima_imbalance_lock);
	printk(KERN_INFO "IMA: unmeasured files on fsmagic: %lX\n",
	entry->fsmagic);
	out:
	return found;
	}

	/* ima_read_write_check - reflect possible reading/writing errors in the PCR.
	*
	* When opening a file for read, if the file is already open for write,
	* the file could change, resulting in a file measurement error.
	*
	* Opening a file for write, if the file is already open for read, results
	* in a time of measure, time of use (ToMToU) error.
	*
	* In either case invalidate the PCR.
	*/
	enum iint_pcr_error { TOMTOU, OPEN_WRITERS };
	static void ima_read_write_check(enum iint_pcr_error error,
	struct ima_iint_cache *iint,
	struct inode *inode,
	const unsigned char *filename)
	{
	switch (error) {
	case TOMTOU:
	if (iint->readcount > 0)
	ima_add_violation(inode, filename, "invalid_pcr",
	"ToMToU");
	break;
	case OPEN_WRITERS:
	if (iint->writecount > 0)
	ima_add_violation(inode, filename, "invalid_pcr",
	"open_writers");
	break;
	}
	}

	/*
	* Update the counts given an fmode_t
	*/
	static void ima_inc_counts(struct ima_iint_cache *iint, fmode_t mode)
	{
	BUG_ON(!mutex_is_locked(&iint->mutex));

	iint->opencount++;
	if ((mode & (FMODE_READ \| FMODE_WRITE)) == FMODE_READ)
	iint->readcount++;
	if (mode & FMODE_WRITE)
	iint->writecount++;
	}

	/*
	* ima_counts_get - increment file counts
	*
	* Maintain read/write counters for all files, but only
	* invalidate the PCR for measured files:
	* - Opening a file for write when already open for read,
	* results in a time of measure, time of use (ToMToU) error.
	* - Opening a file for read when already open for write,
	* could result in a file measurement error.
	*
	*/
	void ima_counts_get(struct file *file)
	{
	struct dentry *dentry = file->f_path.dentry;
	struct inode *inode = dentry->d_inode;
	fmode_t mode = file->f_mode;
	struct ima_iint_cache *iint;
	int rc;

	if (!ima_initialized \|\| !S_ISREG(inode->i_mode))
	return;
	iint = ima_iint_find_get(inode);
	if (!iint)
	return;
	mutex_lock(&iint->mutex);
	rc = ima_must_measure(iint, inode, MAY_READ, PATH_CHECK);
	if (rc < 0)
	goto out;

	if (mode & FMODE_WRITE) {
	ima_read_write_check(TOMTOU, iint, inode, dentry->d_name.name);
	goto out;
	}
	ima_read_write_check(OPEN_WRITERS, iint, inode, dentry->d_name.name);
	out:
	ima_inc_counts(iint, file->f_mode);
	mutex_unlock(&iint->mutex);

	kref_put(&iint->refcount, iint_free);
	}

	/*
	* Decrement ima counts
	*/
	static void ima_dec_counts(struct ima_iint_cache iint, struct inode inode,
	struct file *file)
	{
	mode_t mode = file->f_mode;
	BUG_ON(!mutex_is_locked(&iint->mutex));

	iint->opencount--;
	if ((mode & (FMODE_READ \| FMODE_WRITE)) == FMODE_READ)
	iint->readcount--;
	if (mode & FMODE_WRITE) {
	iint->writecount--;
	if (iint->writecount == 0) {
	if (iint->version != inode->i_version)
	iint->flags &= ~IMA_MEASURED;
	}
	}

	if (((iint->opencount < 0) \|\|
	(iint->readcount < 0) \|\|
	(iint->writecount < 0)) &&
	!ima_limit_imbalance(file)) {
	printk(KERN_INFO "%s: open/free imbalance (r:%ld w:%ld o:%ld)\n",
	__FUNCTION__, iint->readcount, iint->writecount,
	iint->opencount);
	dump_stack();
	}
	}

	/**
	* ima_file_free - called on __fput()
	* @file: pointer to file structure being freed
	*
	* Flag files that changed, based on i_version;
	* and decrement the iint readcount/writecount.
	*/
	void ima_file_free(struct file *file)
	{
	struct inode *inode = file->f_dentry->d_inode;
	struct ima_iint_cache *iint;

	if (!ima_initialized \|\| !S_ISREG(inode->i_mode))
	return;
	iint = ima_iint_find_get(inode);
	if (!iint)
	return;

	mutex_lock(&iint->mutex);
	ima_dec_counts(iint, inode, file);
	mutex_unlock(&iint->mutex);
	kref_put(&iint->refcount, iint_free);
	}

	static int process_measurement(struct file file, const unsigned char filename,
	int mask, int function)
	{
	struct inode *inode = file->f_dentry->d_inode;
	struct ima_iint_cache *iint;
	int rc;

	if (!ima_initialized \|\| !S_ISREG(inode->i_mode))
	return 0;
	iint = ima_iint_find_get(inode);
	if (!iint)
	return -ENOMEM;

	mutex_lock(&iint->mutex);
	rc = ima_must_measure(iint, inode, mask, function);
	if (rc != 0)
	goto out;

	rc = ima_collect_measurement(iint, file);
	if (!rc)
	ima_store_measurement(iint, file, filename);
	out:
	mutex_unlock(&iint->mutex);
	kref_put(&iint->refcount, iint_free);
	return rc;
	}

	/**
	* ima_file_mmap - based on policy, collect/store measurement.
	* @file: pointer to the file to be measured (May be NULL)
	* @prot: contains the protection that will be applied by the kernel.
	*
	* Measure files being mmapped executable based on the ima_must_measure()
	* policy decision.
	*
	* Return 0 on success, an error code on failure.
	* (Based on the results of appraise_measurement().)
	*/
	int ima_file_mmap(struct file *file, unsigned long prot)
	{
	int rc;

	if (!file)
	return 0;
	if (prot & PROT_EXEC)
	rc = process_measurement(file, file->f_dentry->d_name.name,
	MAY_EXEC, FILE_MMAP);
	return 0;
	}

	/**
	* ima_bprm_check - based on policy, collect/store measurement.
	* @bprm: contains the linux_binprm structure
	*
	* The OS protects against an executable file, already open for write,
	* from being executed in deny_write_access() and an executable file,
	* already open for execute, from being modified in get_write_access().
	* So we can be certain that what we verify and measure here is actually
	* what is being executed.
	*
	* Return 0 on success, an error code on failure.
	* (Based on the results of appraise_measurement().)
	*/
	int ima_bprm_check(struct linux_binprm *bprm)
	{
	int rc;

	rc = process_measurement(bprm->file, bprm->filename,
	MAY_EXEC, BPRM_CHECK);
	return 0;
	}

	/**
	* ima_path_check - based on policy, collect/store measurement.
	* @file: pointer to the file to be measured
	* @mask: contains MAY_READ, MAY_WRITE or MAY_EXECUTE
	*
	* Measure files based on the ima_must_measure() policy decision.
	*
	* Always return 0 and audit dentry_open failures.
	* (Return code will be based upon measurement appraisal.)
	*/
	int ima_path_check(struct file *file, int mask)
	{
	int rc;

	rc = process_measurement(file, file->f_dentry->d_name.name,
	mask & (MAY_READ \| MAY_WRITE \| MAY_EXEC),
	PATH_CHECK);
	return 0;
	}
	EXPORT_SYMBOL_GPL(ima_path_check);

	static int __init init_ima(void)
	{
	int error;

	ima_iintcache_init();
	error = ima_init();
	ima_initialized = 1;
	return error;
	}

	static void __exit cleanup_ima(void)
	{
	ima_cleanup();
	}

	late_initcall(init_ima); /* Start IMA after the TPM is available */

	MODULE_DESCRIPTION("Integrity Measurement Architecture");
	MODULE_LICENSE("GPL");