fips140-eval-testing.c

// SPDX-License-Identifier: GPL-2.0-only
/*
 * Copyright 2021 Google LLC
 *
 * This file can optionally be built into fips140.ko in order to support certain
 * types of testing that the FIPS lab has to do to evaluate the module.  It
 * should not be included in production builds of the module.
 */

/*
 * We have to redefine inline to mean always_inline, so that _copy_to_user()
 * gets inlined.  This is needed for it to be placed into the correct section.
 * See fips140_copy_to_user().
 *
 * We also need to undefine BUILD_FIPS140_KO to allow the use of the code
 * patching which copy_to_user() requires.
 */
#undef inline
#define inline inline __attribute__((__always_inline__)) __gnu_inline \
       __inline_maybe_unused notrace
#undef BUILD_FIPS140_KO

#include <linux/cdev.h>
#include <linux/fs.h>
#include <linux/module.h>
#include <linux/slab.h>

#include "fips140-module.h"
#include "fips140-eval-testing-uapi.h"

/*
 * This option allows deliberately failing the self-tests for a particular
 * algorithm.
 */
static char *fips140_fail_selftest;
module_param_named(fail_selftest, fips140_fail_selftest, charp, 0);

/* This option allows deliberately failing the integrity check. */
static bool fips140_fail_integrity_check;
module_param_named(fail_integrity_check, fips140_fail_integrity_check, bool, 0);

static dev_t fips140_devnum;
static struct cdev fips140_cdev;

/* Inject a self-test failure (via corrupting the result) if requested. */
void fips140_inject_selftest_failure(const char *impl, u8 *result)
{
	if (fips140_fail_selftest && strcmp(impl, fips140_fail_selftest) == 0)
		result[0] ^= 0xff;
}

/* Inject an integrity check failure (via corrupting the text) if requested. */
void fips140_inject_integrity_failure(u8 *textcopy)
{
	if (fips140_fail_integrity_check)
		textcopy[0] ^= 0xff;
}

static long fips140_ioctl_is_approved_service(unsigned long arg)
{
	const char *service_name = strndup_user((const char __user *)arg, 256);
	long ret;

	if (IS_ERR(service_name))
		return PTR_ERR(service_name);

	ret = fips140_is_approved_service(service_name);

	kfree(service_name);
	return ret;
}

/*
 * Code in fips140.ko is covered by an integrity check by default, and this
 * check breaks if copy_to_user() is called.  This is because copy_to_user() is
 * an inline function that relies on code patching.  However, since this is
 * "evaluation testing" code which isn't included in the production builds of
 * fips140.ko, it's acceptable to just exclude it from the integrity check.
 */
static noinline unsigned long __section("text.._fips140_unchecked")
fips140_copy_to_user(void __user *to, const void *from, unsigned long n)
{
	return copy_to_user(to, from, n);
}

static long fips140_ioctl_module_version(unsigned long arg)
{
	const char *version = fips140_module_version();
	size_t len = strlen(version) + 1;

	if (len > 256)
		return -EOVERFLOW;

	if (fips140_copy_to_user((void __user *)arg, version, len))
		return -EFAULT;

	return 0;
}

static long fips140_ioctl(struct file *file, unsigned int cmd,
			  unsigned long arg)
{
	switch (cmd) {
	case FIPS140_IOCTL_IS_APPROVED_SERVICE:
		return fips140_ioctl_is_approved_service(arg);
	case FIPS140_IOCTL_MODULE_VERSION:
		return fips140_ioctl_module_version(arg);
	default:
		return -ENOTTY;
	}
}

static const struct file_operations fips140_fops = {
	.unlocked_ioctl = fips140_ioctl,
};

bool fips140_eval_testing_init(void)
{
	if (alloc_chrdev_region(&fips140_devnum, 1, 1, "fips140") != 0) {
		pr_err("failed to allocate device number\n");
		return false;
	}
	cdev_init(&fips140_cdev, &fips140_fops);
	if (cdev_add(&fips140_cdev, fips140_devnum, 1) != 0) {
		pr_err("failed to add fips140 character device\n");
		return false;
	}
	return true;
}