/*
* 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);
/**
* 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);
if (iint->opencount <= 0) {
printk(KERN_INFO
"%s: %s open/free imbalance (r:%ld w:%ld o:%ld f:%ld)\n",
__FUNCTION__, file->f_dentry->d_name.name,
iint->readcount, iint->writecount,
iint->opencount, atomic_long_read(&file->f_count));
if (!(iint->flags & IMA_IINT_DUMP_STACK)) {
dump_stack();
iint->flags |= IMA_IINT_DUMP_STACK;
}
}
iint->opencount--;
if ((file->f_mode & (FMODE_READ | FMODE_WRITE)) == FMODE_READ)
iint->readcount--;
if (file->f_mode & FMODE_WRITE) {
iint->writecount--;
if (iint->writecount == 0) {
if (iint->version != inode->i_version)
iint->flags &= ~IMA_MEASURED;
}
}
mutex_unlock(&iint->mutex);
kref_put(&iint->refcount, iint_free);
}
/* 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;
}
}
static int get_path_measurement(struct ima_iint_cache *iint, struct file *file,
const unsigned char *filename)
{
int rc = 0;
iint->opencount++;
iint->readcount++;
rc = ima_collect_measurement(iint, file);
if (!rc)
ima_store_measurement(iint, file, filename);
return rc;
}
/**
* ima_path_check - based on policy, collect/store measurement.
* @path: contains a pointer to the path to be measured
* @mask: contains MAY_READ, MAY_WRITE or MAY_EXECUTE
*
* Measure the file being open for readonly, based on the
* ima_must_measure() policy decision.
*
* Keep 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.
*
* Return 0 on success, an error code on failure.
* (Based on the results of appraise_measurement().)
*/
int ima_path_check(struct path *path, int mask)
{
struct inode *inode = path->dentry->d_inode;
struct ima_iint_cache *iint;
struct file *file = NULL;
int rc;
if (!ima_initialized || !S_ISREG(inode->i_mode))
return 0;
iint = ima_iint_find_insert_get(inode);
if (!iint)
return 0;
mutex_lock(&iint->mutex);
iint->opencount++;
if ((mask & MAY_WRITE) || (mask == 0))
iint->writecount++;
else if (mask & (MAY_READ | MAY_EXEC))
iint->readcount++;
rc = ima_must_measure(iint, inode, MAY_READ, PATH_CHECK);
if (rc < 0)
goto out;
if ((mask & MAY_WRITE) || (mask == 0))
ima_read_write_check(TOMTOU, iint, inode,
path->dentry->d_name.name);
if ((mask & (MAY_WRITE | MAY_READ | MAY_EXEC)) != MAY_READ)
goto out;
ima_read_write_check(OPEN_WRITERS, iint, inode,
path->dentry->d_name.name);
if (!(iint->flags & IMA_MEASURED)) {
struct dentry *dentry = dget(path->dentry);
struct vfsmount *mnt = mntget(path->mnt);
file = dentry_open(dentry, mnt, O_RDONLY, current_cred());
if (IS_ERR(file)) {
pr_info("%s dentry_open failed\n", dentry->d_name.name);
rc = PTR_ERR(file);
file = NULL;
goto out;
}
rc = get_path_measurement(iint, file, dentry->d_name.name);
}
out:
mutex_unlock(&iint->mutex);
if (file)
fput(file);
kref_put(&iint->refcount, iint_free);
return 0;
}
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_insert_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;
}
static void opencount_get(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_insert_get(inode);
if (!iint)
return;
mutex_lock(&iint->mutex);
iint->opencount++;
mutex_unlock(&iint->mutex);
}
/**
* 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_shm_check - IPC shm and shmat create/fput a file
*
* Maintain the opencount for these files to prevent unnecessary
* imbalance messages.
*/
void ima_shm_check(struct file *file)
{
opencount_get(file);
return;
}
/**
* 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;
}
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");
