/*
* 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_file_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, FILE_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_file_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),
FILE_CHECK);
return 0;
}
EXPORT_SYMBOL_GPL(ima_file_check);
static int __init init_ima(void)
{
int error;
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");
