linux/security/integrity/ima/ima_main.c

311 lines
8.2 KiB
C

/*
* 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 <linux/slab.h>
#include <linux/xattr.h>
#include <linux/ima.h>
#include "ima.h"
int ima_initialized;
#ifdef CONFIG_IMA_APPRAISE
int ima_appraise = IMA_APPRAISE_ENFORCE;
#else
int ima_appraise;
#endif
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_rdwr_violation_check
*
* 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.
*
*/
static void ima_rdwr_violation_check(struct file *file)
{
struct dentry *dentry = file->f_path.dentry;
struct inode *inode = dentry->d_inode;
fmode_t mode = file->f_mode;
int must_measure;
bool send_tomtou = false, send_writers = false;
char *pathbuf = NULL;
const char *pathname;
if (!S_ISREG(inode->i_mode) || !ima_initialized)
return;
mutex_lock(&inode->i_mutex); /* file metadata: permissions, xattr */
if (mode & FMODE_WRITE) {
if (atomic_read(&inode->i_readcount) && IS_IMA(inode))
send_tomtou = true;
goto out;
}
must_measure = ima_must_measure(inode, MAY_READ, FILE_CHECK);
if (!must_measure)
goto out;
if (atomic_read(&inode->i_writecount) > 0)
send_writers = true;
out:
mutex_unlock(&inode->i_mutex);
if (!send_tomtou && !send_writers)
return;
pathname = ima_d_path(&file->f_path, &pathbuf);
if (!pathname || strlen(pathname) > IMA_EVENT_NAME_LEN_MAX)
pathname = dentry->d_name.name;
if (send_tomtou)
ima_add_violation(inode, pathname,
"invalid_pcr", "ToMToU");
if (send_writers)
ima_add_violation(inode, pathname,
"invalid_pcr", "open_writers");
kfree(pathbuf);
}
static void ima_check_last_writer(struct integrity_iint_cache *iint,
struct inode *inode, struct file *file)
{
fmode_t mode = file->f_mode;
if (!(mode & FMODE_WRITE))
return;
mutex_lock(&inode->i_mutex);
if (atomic_read(&inode->i_writecount) == 1 &&
iint->version != inode->i_version) {
iint->flags &= ~IMA_DONE_MASK;
if (iint->flags & IMA_APPRAISE)
ima_update_xattr(iint, file);
}
mutex_unlock(&inode->i_mutex);
}
/**
* ima_file_free - called on __fput()
* @file: pointer to file structure being freed
*
* Flag files that changed, based on i_version
*/
void ima_file_free(struct file *file)
{
struct inode *inode = file_inode(file);
struct integrity_iint_cache *iint;
if (!iint_initialized || !S_ISREG(inode->i_mode))
return;
iint = integrity_iint_find(inode);
if (!iint)
return;
ima_check_last_writer(iint, inode, file);
}
static int process_measurement(struct file *file, const char *filename,
int mask, int function)
{
struct inode *inode = file_inode(file);
struct integrity_iint_cache *iint;
char *pathbuf = NULL;
const char *pathname = NULL;
int rc = -ENOMEM, action, must_appraise, _func;
if (!ima_initialized || !S_ISREG(inode->i_mode))
return 0;
/* Return an IMA_MEASURE, IMA_APPRAISE, IMA_AUDIT action
* bitmask based on the appraise/audit/measurement policy.
* Included is the appraise submask.
*/
action = ima_get_action(inode, mask, function);
if (!action)
return 0;
must_appraise = action & IMA_APPRAISE;
/* Is the appraise rule hook specific? */
_func = (action & IMA_FILE_APPRAISE) ? FILE_CHECK : function;
mutex_lock(&inode->i_mutex);
iint = integrity_inode_get(inode);
if (!iint)
goto out;
/* Determine if already appraised/measured based on bitmask
* (IMA_MEASURE, IMA_MEASURED, IMA_XXXX_APPRAISE, IMA_XXXX_APPRAISED,
* IMA_AUDIT, IMA_AUDITED)
*/
iint->flags |= action;
action &= IMA_DO_MASK;
action &= ~((iint->flags & IMA_DONE_MASK) >> 1);
/* Nothing to do, just return existing appraised status */
if (!action) {
if (must_appraise)
rc = ima_get_cache_status(iint, _func);
goto out_digsig;
}
rc = ima_collect_measurement(iint, file);
if (rc != 0)
goto out_digsig;
if (function != BPRM_CHECK)
pathname = ima_d_path(&file->f_path, &pathbuf);
if (!pathname)
pathname = filename;
if (action & IMA_MEASURE)
ima_store_measurement(iint, file, pathname);
if (action & IMA_APPRAISE_SUBMASK)
rc = ima_appraise_measurement(_func, iint, file, pathname);
if (action & IMA_AUDIT)
ima_audit_measurement(iint, pathname);
kfree(pathbuf);
out_digsig:
if ((mask & MAY_WRITE) && (iint->flags & IMA_DIGSIG))
rc = -EACCES;
out:
mutex_unlock(&inode->i_mutex);
if ((rc && must_appraise) && (ima_appraise & IMA_APPRAISE_ENFORCE))
return -EACCES;
return 0;
}
/**
* 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.
*
* On success return 0. On integrity appraisal error, assuming the file
* is in policy and IMA-appraisal is in enforcing mode, return -EACCES.
*/
int ima_file_mmap(struct file *file, unsigned long prot)
{
if (file && (prot & PROT_EXEC))
return process_measurement(file, file->f_dentry->d_name.name,
MAY_EXEC, MMAP_CHECK);
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.
*
* On success return 0. On integrity appraisal error, assuming the file
* is in policy and IMA-appraisal is in enforcing mode, return -EACCES.
*/
int ima_bprm_check(struct linux_binprm *bprm)
{
return process_measurement(bprm->file,
(strcmp(bprm->filename, bprm->interp) == 0) ?
bprm->filename : bprm->interp,
MAY_EXEC, BPRM_CHECK);
}
/**
* 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.
*
* On success return 0. On integrity appraisal error, assuming the file
* is in policy and IMA-appraisal is in enforcing mode, return -EACCES.
*/
int ima_file_check(struct file *file, int mask)
{
ima_rdwr_violation_check(file);
return process_measurement(file, file->f_dentry->d_name.name,
mask & (MAY_READ | MAY_WRITE | MAY_EXEC),
FILE_CHECK);
}
EXPORT_SYMBOL_GPL(ima_file_check);
/**
* ima_module_check - based on policy, collect/store/appraise measurement.
* @file: pointer to the file to be measured/appraised
*
* Measure/appraise kernel modules based on policy.
*
* On success return 0. On integrity appraisal error, assuming the file
* is in policy and IMA-appraisal is in enforcing mode, return -EACCES.
*/
int ima_module_check(struct file *file)
{
if (!file) {
#ifndef CONFIG_MODULE_SIG_FORCE
if ((ima_appraise & IMA_APPRAISE_MODULES) &&
(ima_appraise & IMA_APPRAISE_ENFORCE))
return -EACCES; /* INTEGRITY_UNKNOWN */
#endif
return 0; /* We rely on module signature checking */
}
return process_measurement(file, file->f_dentry->d_name.name,
MAY_EXEC, MODULE_CHECK);
}
static int __init init_ima(void)
{
int error;
error = ima_init();
if (!error)
ima_initialized = 1;
return error;
}
late_initcall(init_ima); /* Start IMA after the TPM is available */
MODULE_DESCRIPTION("Integrity Measurement Architecture");
MODULE_LICENSE("GPL");