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// SPDX-License-Identifier: GPL-2.0
/*
* Copyright 2019 Google LLC
*/
#include <crypto/sha.h>
#include <crypto/hash.h>
#include <linux/err.h>
#include <linux/version.h>
#include "integrity.h"
struct incfs_hash_alg *incfs_get_hash_alg(enum incfs_hash_tree_algorithm id)
{
static struct incfs_hash_alg sha256 = {
.name = "sha256",
.digest_size = SHA256_DIGEST_SIZE,
.id = INCFS_HASH_TREE_SHA256
};
struct incfs_hash_alg *result = NULL;
struct crypto_shash *shash;
if (id == INCFS_HASH_TREE_SHA256) {
BUILD_BUG_ON(INCFS_MAX_HASH_SIZE < SHA256_DIGEST_SIZE);
result = &sha256;
}
if (result == NULL)
return ERR_PTR(-ENOENT);
/* pairs with cmpxchg_release() below */
shash = smp_load_acquire(&result->shash);
if (shash)
return result;
shash = crypto_alloc_shash(result->name, 0, 0);
if (IS_ERR(shash)) {
int err = PTR_ERR(shash);
pr_err("Can't allocate hash alg %s, error code:%d",
result->name, err);
return ERR_PTR(err);
}
/* pairs with smp_load_acquire() above */
if (cmpxchg_release(&result->shash, NULL, shash) != NULL)
crypto_free_shash(shash);
return result;
}
struct signature_info {
u32 version;
enum incfs_hash_tree_algorithm hash_algorithm;
u8 log2_blocksize;
struct mem_range salt;
struct mem_range root_hash;
};
static bool read_u32(u8 **p, u8 *top, u32 *result)
{
if (*p + sizeof(u32) > top)
return false;
*result = le32_to_cpu(*(__le32 *)*p);
*p += sizeof(u32);
return true;
}
static bool read_u8(u8 **p, u8 *top, u8 *result)
{
if (*p + sizeof(u8) > top)
return false;
*result = *(u8 *)*p;
*p += sizeof(u8);
return true;
}
static bool read_mem_range(u8 **p, u8 *top, struct mem_range *range)
{
u32 len;
if (!read_u32(p, top, &len) || *p + len > top)
return false;
range->len = len;
range->data = *p;
*p += len;
return true;
}
static int incfs_parse_signature(struct mem_range signature,
struct signature_info *si)
{
u8 *p = signature.data;
u8 *top = signature.data + signature.len;
u32 hash_section_size;
if (signature.len > INCFS_MAX_SIGNATURE_SIZE)
return -EINVAL;
if (!read_u32(&p, top, &si->version) ||
si->version != INCFS_SIGNATURE_VERSION)
return -EINVAL;
if (!read_u32(&p, top, &hash_section_size) ||
p + hash_section_size > top)
return -EINVAL;
top = p + hash_section_size;
if (!read_u32(&p, top, &si->hash_algorithm) ||
si->hash_algorithm != INCFS_HASH_TREE_SHA256)
return -EINVAL;
if (!read_u8(&p, top, &si->log2_blocksize) || si->log2_blocksize != 12)
return -EINVAL;
if (!read_mem_range(&p, top, &si->salt))
return -EINVAL;
if (!read_mem_range(&p, top, &si->root_hash))
return -EINVAL;
if (p != top)
return -EINVAL;
return 0;
}
struct mtree *incfs_alloc_mtree(struct mem_range signature,
int data_block_count)
{
int error;
struct signature_info si;
struct mtree *result = NULL;
struct incfs_hash_alg *hash_alg = NULL;
int hash_per_block;
int lvl;
int total_blocks = 0;
int blocks_in_level[INCFS_MAX_MTREE_LEVELS];
int blocks = data_block_count;
if (data_block_count <= 0)
return ERR_PTR(-EINVAL);
error = incfs_parse_signature(signature, &si);
if (error)
return ERR_PTR(error);
hash_alg = incfs_get_hash_alg(si.hash_algorithm);
if (IS_ERR(hash_alg))
return ERR_PTR(PTR_ERR(hash_alg));
if (si.root_hash.len < hash_alg->digest_size)
return ERR_PTR(-EINVAL);
result = kzalloc(sizeof(*result), GFP_NOFS);
if (!result)
return ERR_PTR(-ENOMEM);
result->alg = hash_alg;
hash_per_block = INCFS_DATA_FILE_BLOCK_SIZE / result->alg->digest_size;
/* Calculating tree geometry. */
/* First pass: calculate how many blocks in each tree level. */
for (lvl = 0; blocks > 1; lvl++) {
if (lvl >= INCFS_MAX_MTREE_LEVELS) {
pr_err("incfs: too much data in mtree");
goto err;
}
blocks = (blocks + hash_per_block - 1) / hash_per_block;
blocks_in_level[lvl] = blocks;
total_blocks += blocks;
}
result->depth = lvl;
result->hash_tree_area_size = total_blocks * INCFS_DATA_FILE_BLOCK_SIZE;
if (result->hash_tree_area_size > INCFS_MAX_HASH_AREA_SIZE)
goto err;
blocks = 0;
/* Second pass: calculate offset of each level. 0th level goes last. */
for (lvl = 0; lvl < result->depth; lvl++) {
u32 suboffset;
blocks += blocks_in_level[lvl];
suboffset = (total_blocks - blocks)
* INCFS_DATA_FILE_BLOCK_SIZE;
result->hash_level_suboffset[lvl] = suboffset;
}
/* Root hash is stored separately from the rest of the tree. */
memcpy(result->root_hash, si.root_hash.data, hash_alg->digest_size);
return result;
err:
kfree(result);
return ERR_PTR(-E2BIG);
}
void incfs_free_mtree(struct mtree *tree)
{
kfree(tree);
}
int incfs_calc_digest(struct incfs_hash_alg *alg, struct mem_range data,
struct mem_range digest)
{
SHASH_DESC_ON_STACK(desc, alg->shash);
if (!alg || !alg->shash || !data.data || !digest.data)
return -EFAULT;
if (alg->digest_size > digest.len)
return -EINVAL;
desc->tfm = alg->shash;
if (data.len < INCFS_DATA_FILE_BLOCK_SIZE) {
int err;
void *buf = kzalloc(INCFS_DATA_FILE_BLOCK_SIZE, GFP_NOFS);
if (!buf)
return -ENOMEM;
memcpy(buf, data.data, data.len);
err = crypto_shash_digest(desc, buf, INCFS_DATA_FILE_BLOCK_SIZE,
digest.data);
kfree(buf);
return err;
}
return crypto_shash_digest(desc, data.data, data.len, digest.data);
}
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