path: root/security/integrity/ima/ima_main.c

// SPDX-License-Identifier: GPL-2.0-only
/*
 * Integrity Measurement Architecture
 *
 * 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>
 *
 * 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/kernel_read_file.h>
#include <linux/mount.h>
#include <linux/mman.h>
#include <linux/slab.h>
#include <linux/xattr.h>
#include <linux/ima.h>
#include <linux/iversion.h>
#include <linux/fs.h>

#include "ima.h"

#ifdef CONFIG_IMA_APPRAISE
int ima_appraise = IMA_APPRAISE_ENFORCE;
#else
int ima_appraise;
#endif

int __ro_after_init ima_hash_algo = HASH_ALGO_SHA1;
static int hash_setup_done;

static struct notifier_block ima_lsm_policy_notifier = {
	.notifier_call = ima_lsm_policy_change,
};

static int __init hash_setup(char *str)
{
	struct ima_template_desc *template_desc = ima_template_desc_current();
	int i;

	if (hash_setup_done)
		return 1;

	if (strcmp(template_desc->name, IMA_TEMPLATE_IMA_NAME) == 0) {
		if (strncmp(str, "sha1", 4) == 0) {
			ima_hash_algo = HASH_ALGO_SHA1;
		} else if (strncmp(str, "md5", 3) == 0) {
			ima_hash_algo = HASH_ALGO_MD5;
		} else {
			pr_err("invalid hash algorithm \"%s\" for template \"%s\"",
				str, IMA_TEMPLATE_IMA_NAME);
			return 1;
		}
		goto out;
	}

	i = match_string(hash_algo_name, HASH_ALGO__LAST, str);
	if (i < 0) {
		pr_err("invalid hash algorithm \"%s\"", str);
		return 1;
	}

	ima_hash_algo = i;
out:
	hash_setup_done = 1;
	return 1;
}
__setup("ima_hash=", hash_setup);

enum hash_algo ima_get_current_hash_algo(void)
{
	return ima_hash_algo;
}

/* Prevent mmap'ing a file execute that is already mmap'ed write */
static int mmap_violation_check(enum ima_hooks func, struct file *file,
				char **pathbuf, const char **pathname,
				char *filename)
{
	struct inode *inode;
	int rc = 0;

	if ((func == MMAP_CHECK) && mapping_writably_mapped(file->f_mapping)) {
		rc = -ETXTBSY;
		inode = file_inode(file);

		if (!*pathbuf)	/* ima_rdwr_violation possibly pre-fetched */
			*pathname = ima_d_path(&file->f_path, pathbuf,
					       filename);
		integrity_audit_msg(AUDIT_INTEGRITY_DATA, inode, *pathname,
				    "mmap_file", "mmapped_writers", rc, 0);
	}
	return rc;
}

/*
 * 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 integrity_iint_cache *iint,
				     int must_measure,
				     char **pathbuf,
				     const char **pathname,
				     char *filename)
{
	struct inode *inode = file_inode(file);
	fmode_t mode = file->f_mode;
	bool send_tomtou = false, send_writers = false;

	if (mode & FMODE_WRITE) {
		if (atomic_read(&inode->i_readcount) && IS_IMA(inode)) {
			if (!iint)
				iint = integrity_iint_find(inode);
			/* IMA_MEASURE is set from reader side */
			if (iint && test_bit(IMA_MUST_MEASURE,
						&iint->atomic_flags))
				send_tomtou = true;
		}
	} else {
		if (must_measure)
			set_bit(IMA_MUST_MEASURE, &iint->atomic_flags);
		if (inode_is_open_for_write(inode) && must_measure)
			send_writers = true;
	}

	if (!send_tomtou && !send_writers)
		return;

	*pathname = ima_d_path(&file->f_path, pathbuf, filename);

	if (send_tomtou)
		ima_add_violation(file, *pathname, iint,
				  "invalid_pcr", "ToMToU");
	if (send_writers)
		ima_add_violation(file, *pathname, iint,
				  "invalid_pcr", "open_writers");
}

static void ima_check_last_writer(struct integrity_iint_cache *iint,
				  struct inode *inode, struct file *file)
{
	fmode_t mode = file->f_mode;
	bool update;

	if (!(mode & FMODE_WRITE))
		return;

	mutex_lock(&iint->mutex);
	if (atomic_read(&inode->i_writecount) == 1) {
		update = test_and_clear_bit(IMA_UPDATE_XATTR,