cachepc-linux

Fork of AMDESE/linux with modifications for CachePC side-channel attack
git clone https://git.sinitax.com/sinitax/cachepc-linux
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measure.c (2868B)

      1// SPDX-License-Identifier: GPL-2.0
      2/*
      3 * Ioctl to get a verity file's digest
      4 *
      5 * Copyright 2019 Google LLC
      6 */
      7
      8#include "fsverity_private.h"
      9
     10#include <linux/uaccess.h>
     11
     12/**
     13 * fsverity_ioctl_measure() - get a verity file's digest
     14 * @filp: file to get digest of
     15 * @_uarg: user pointer to fsverity_digest
     16 *
     17 * Retrieve the file digest that the kernel is enforcing for reads from a verity
     18 * file.  See the "FS_IOC_MEASURE_VERITY" section of
     19 * Documentation/filesystems/fsverity.rst for the documentation.
     20 *
     21 * Return: 0 on success, -errno on failure
     22 */
     23int fsverity_ioctl_measure(struct file *filp, void __user *_uarg)
     24{
     25	const struct inode *inode = file_inode(filp);
     26	struct fsverity_digest __user *uarg = _uarg;
     27	const struct fsverity_info *vi;
     28	const struct fsverity_hash_alg *hash_alg;
     29	struct fsverity_digest arg;
     30
     31	vi = fsverity_get_info(inode);
     32	if (!vi)
     33		return -ENODATA; /* not a verity file */
     34	hash_alg = vi->tree_params.hash_alg;
     35
     36	/*
     37	 * The user specifies the digest_size their buffer has space for; we can
     38	 * return the digest if it fits in the available space.  We write back
     39	 * the actual size, which may be shorter than the user-specified size.
     40	 */
     41
     42	if (get_user(arg.digest_size, &uarg->digest_size))
     43		return -EFAULT;
     44	if (arg.digest_size < hash_alg->digest_size)
     45		return -EOVERFLOW;
     46
     47	memset(&arg, 0, sizeof(arg));
     48	arg.digest_algorithm = hash_alg - fsverity_hash_algs;
     49	arg.digest_size = hash_alg->digest_size;
     50
     51	if (copy_to_user(uarg, &arg, sizeof(arg)))
     52		return -EFAULT;
     53
     54	if (copy_to_user(uarg->digest, vi->file_digest, hash_alg->digest_size))
     55		return -EFAULT;
     56
     57	return 0;
     58}
     59EXPORT_SYMBOL_GPL(fsverity_ioctl_measure);
     60
     61/**
     62 * fsverity_get_digest() - get a verity file's digest
     63 * @inode: inode to get digest of
     64 * @digest: (out) pointer to the digest
     65 * @alg: (out) pointer to the hash algorithm enumeration
     66 *
     67 * Return the file hash algorithm and digest of an fsverity protected file.
     68 * Assumption: before calling fsverity_get_digest(), the file must have been
     69 * opened.
     70 *
     71 * Return: 0 on success, -errno on failure
     72 */
     73int fsverity_get_digest(struct inode *inode,
     74			u8 digest[FS_VERITY_MAX_DIGEST_SIZE],
     75			enum hash_algo *alg)
     76{
     77	const struct fsverity_info *vi;
     78	const struct fsverity_hash_alg *hash_alg;
     79	int i;
     80
     81	vi = fsverity_get_info(inode);
     82	if (!vi)
     83		return -ENODATA; /* not a verity file */
     84
     85	hash_alg = vi->tree_params.hash_alg;
     86	memset(digest, 0, FS_VERITY_MAX_DIGEST_SIZE);
     87
     88	/* convert the verity hash algorithm name to a hash_algo_name enum */
     89	i = match_string(hash_algo_name, HASH_ALGO__LAST, hash_alg->name);
     90	if (i < 0)
     91		return -EINVAL;
     92	*alg = i;
     93
     94	if (WARN_ON_ONCE(hash_alg->digest_size != hash_digest_size[*alg]))
     95		return -EINVAL;
     96	memcpy(digest, vi->file_digest, hash_alg->digest_size);
     97
     98	pr_debug("file digest %s:%*phN\n", hash_algo_name[*alg],
     99		 hash_digest_size[*alg], digest);
    100
    101	return 0;
    102}