// SPDX-License-Identifier: GPL-2.0
/*
* This file is part of UBIFS.
*
* Copyright (C) 2018 Pengutronix, Sascha Hauer <[email protected]>
*/
/*
* This file implements various helper functions for UBIFS authentication support
*/
#include <linux/verification.h>
#include <crypto/hash.h>
#include <crypto/utils.h>
#include <keys/user-type.h>
#include <keys/asymmetric-type.h>
#include "ubifs.h"
/**
* __ubifs_node_calc_hash - calculate the hash of a UBIFS node
* @c: UBIFS file-system description object
* @node: the node to calculate a hash for
* @hash: the returned hash
*
* Returns 0 for success or a negative error code otherwise.
*/
int __ubifs_node_calc_hash(const struct ubifs_info *c, const void *node,
u8 *hash)
{
const struct ubifs_ch *ch = node;
return crypto_shash_tfm_digest(c->hash_tfm, node, le32_to_cpu(ch->len),
hash);
}
/**
* ubifs_hash_calc_hmac - calculate a HMAC from a hash
* @c: UBIFS file-system description object
* @hash: the node to calculate a HMAC for
* @hmac: the returned HMAC
*
* Returns 0 for success or a negative error code otherwise.
*/
static int ubifs_hash_calc_hmac(const struct ubifs_info *c, const u8 *hash,
u8 *hmac)
{
return crypto_shash_tfm_digest(c->hmac_tfm, hash, c->hash_len, hmac);
}
/**
* ubifs_prepare_auth_node - Prepare an authentication node
* @c: UBIFS file-system description object
* @node: the node to calculate a hash for
* @inhash: input hash of previous nodes
*
* This function prepares an authentication node for writing onto flash.
* It creates a HMAC from the given input hash and writes it to the node.
*
* Returns 0 for success or a negative error code otherwise.
*/
int ubifs_prepare_auth_node(struct ubifs_info *c, void *node,
struct shash_desc *inhash)
{
struct ubifs_auth_node *auth = node;
u8 hash[UBIFS_HASH_ARR_SZ];
int err;
{
SHASH_DESC_ON_STACK(hash_desc, c->hash_tfm);
hash_desc->tfm = c->hash_tfm;
ubifs_shash_copy_state(c, inhash, hash_desc);
err = crypto_shash_final(hash_desc, hash);
if (err)
return err;
}
err = ubifs_hash_calc_hmac(c, hash, auth->hmac);
if (err)
return err;
auth->ch.node_type = UBIFS_AUTH_NODE;
ubifs_prepare_node(c, auth, ubifs_auth_node_sz(c), 0);
return 0;
}
static struct shash_desc *ubifs_get_desc(const struct ubifs_info *c,
struct crypto_shash *tfm)
{
struct shash_desc *desc;
int err;
if (!ubifs_authenticated(c))
return NULL;
desc = kmalloc(sizeof(*desc) + crypto_shash_descsize(tfm), GFP_KERNEL);
if (!desc)
return ERR_PTR(-ENOMEM);
desc->tfm = tfm;
err = crypto_shash_init(desc);
if (err) {
kfree(desc);
return ERR_PTR(err);
}
return desc;
}
/**
* __ubifs_hash_get_desc - get a descriptor suitable for hashing a node
* @c: UBIFS file-system description object
*
* This function returns a descriptor suitable for hashing a node. Free after use
* with kfree.
*/
struct shash_desc *__ubifs_hash_get_desc(const struct ubifs_info *c)
{
return ubifs_get_desc(c, c->hash_tfm);
}
/**
* ubifs_bad_hash - Report hash mismatches
* @c: UBIFS file-system description object
* @node: the node
* @hash: the expected hash
* @lnum: the LEB @node was read from
* @offs: offset in LEB @node was read from
*
* This function reports a hash mismatch when a node has a different hash than
* expected.
*/
void ubifs_bad_hash(const struct ubifs_info *c, const void *node, const u8 *hash,
int lnum, int offs)
{
int len = min(c->hash_len, 20);
int cropped = len != c->hash_len;
const char *cont = cropped ? "..." : "";
u8 calc[UBIFS_HASH_ARR_SZ];
__ubifs_node_calc_hash(c, node, calc);
ubifs_err(c, "hash mismatch on node at LEB %d:%d", lnum, offs);
ubifs_err(c, "hash expected: %*ph%s", len, hash, cont);
ubifs_err(c, "hash calculated: %*ph%s", len, calc, cont);
}
/**
* __ubifs_node_check_hash - check the hash of a node against given hash
* @c: UBIFS file-system description object
* @node: the node
* @expected: the expected hash
*
* This function calculates a hash over a node and compares it to the given hash.
* Returns 0 if both hashes are equal or authentication is disabled, otherwise a
* negative error code is returned.
*/
int __ubifs_node_check_hash(const struct ubifs_info *c, const void *node,
const u8 *expected)
{
u8 calc[UBIFS_HASH_ARR_SZ];
int err;
err = __ubifs_node_calc_hash(c, node, calc);
if (err)
return err;
if (ubifs_check_hash(c, expected, calc))
return -EPERM;
return 0;
}
/**
* ubifs_sb_verify_signature - verify the signature of a superblock
* @c: UBIFS file-system description object
* @sup: The superblock node
*
* To support offline signed images the superblock can be signed with a
* PKCS#7 signature. The signature is placed directly behind the superblock
* node in an ubifs_sig_node.
*
* Returns 0 when the signature can be successfully verified or a negative
* error code if not.
*/
int ubifs_sb_verify_signature(struct ubifs_info *c,
const struct ubifs_sb_node *sup)
{
int err;
struct ubifs_scan_leb *sleb;
struct ubifs_scan_node *snod;
const struct ubifs_sig_node *signode;
sleb = ubifs_scan(c, UBIFS_SB_LNUM, UBIFS_SB_NODE_SZ, c->sbuf, 0);
if (IS_ERR(sleb)) {
err = PTR_ERR(sleb);
return err;
}
if (sleb->nodes_cnt == 0) {
ubifs_err(c, "Unable to find signature node");
err = -EINVAL;
goto out_destroy;
}
snod = list_first_entry(&sleb->nodes, struct ubifs_scan_node, list);
if (snod->type != UBIFS_SIG_NODE) {
ubifs_err(c, "Signature node is of wrong type");
err = -EINVAL;
goto out_destroy;
}
signode = snod->node;
if (le32_to_cpu(signode->len) > snod->len + sizeof(struct ubifs_sig_node)) {
ubifs_err(c, "invalid signature len %d", le32_to_cpu(signode->len));
err = -EINVAL;
goto out_destroy;
}
if (le32_to_cpu(signode->type) != UBIFS_SIGNATURE_TYPE_PKCS7) {
ubifs_err(c, "Signature type %d is not supported\n",
le32_to_cpu(signode->type));
err = -EINVAL;
goto out_destroy;
}
err = verify_pkcs7_signature(sup, sizeof(struct ubifs_sb_node),
signode->sig, le32_to_cpu(signode->len),
NULL, VERIFYING_UNSPECIFIED_SIGNATURE,
NULL, NULL);
if (err)
ubifs_err(c, "Failed to verify signature");
else
ubifs_msg(c, "Successfully verified super block signature");
out_destroy:
ubifs_scan_destroy(sleb);
return err;
}
/**
* ubifs_init_authentication - initialize UBIFS authentication support
* @c: UBIFS file-system description object
*
* This function returns 0 for success or a negative error code otherwise.
*/
int ubifs_init_authentication(struct ubifs_info *c)
{
struct key *keyring_key;
const struct user_key_payload *ukp;
int err;
char hmac_name[CRYPTO_MAX_ALG_NAME];
if (!c->auth_hash_name) {
ubifs_err(c, "authentication hash name needed with authentication");
return -EINVAL;
}
c->auth_hash_algo = match_string(hash_algo_name, HASH_ALGO__LAST,
c->auth_hash_name);
if ((int)c->auth_hash_algo < 0) {
ubifs_err(c, "Unknown hash algo %s specified",
c->auth_hash_name);
return -EINVAL;
}
snprintf(hmac_name, CRYPTO_MAX_ALG_NAME, "hmac(%s)",
c->auth_hash_name);
keyring_key = request_key(&key_type_logon, c->auth_key_name, NULL);
if (IS_ERR(keyring_key)) {
ubifs_err(c, "Failed to request key: %ld",
PTR_ERR(keyring_key));
return PTR_ERR(keyring_key);
}
down_read(&keyring_key->sem);
if (keyring_key->type != &key_type_logon) {
ubifs_err(c, "key type must be logon");
err = -ENOKEY;
goto out;
}
ukp = user_key_payload_locked(keyring_key);
if (!ukp) {
/* key was revoked before we acquired its semaphore */
err = -EKEYREVOKED;
goto out;
}
c->hash_tfm = crypto_alloc_shash(c->auth_hash_name, 0, 0);
if (IS_ERR(c->hash_tfm)) {
err = PTR_ERR(c->hash_tfm);
ubifs_err(c, "Can not allocate %s: %d",
c->auth_hash_name, err);
goto out;
}
c->hash_len = crypto_shash_digestsize(c->hash_tfm);
if (c->hash_len > UBIFS_HASH_ARR_SZ) {
ubifs_err(c, "hash %s is bigger than maximum allowed hash size (%d > %d)",
c->auth_hash_name, c->hash_len, UBIFS_HASH_ARR_SZ);
err = -EINVAL;
goto out_free_hash;
}
c->hmac_tfm = crypto_alloc_shash(hmac_name, 0, 0);
if (IS_ERR(c->hmac_tfm)) {
err = PTR_ERR(c->hmac_tfm);
ubifs_err(c, "Can not allocate %s: %d", hmac_name, err);
goto out_free_hash;
}
c->hmac_desc_len = crypto_shash_digestsize(c->hmac_tfm);
if (c->hmac_desc_len > UBIFS_HMAC_ARR_SZ) {
ubifs_err(c, "hmac %s is bigger than maximum allowed hmac size (%d > %d)",
hmac_name, c->hmac_desc_len, UBIFS_HMAC_ARR_SZ);
err = -EINVAL;
goto out_free_hmac;
}
err = crypto_shash_setkey(c->hmac_tfm, ukp->data, ukp->datalen);
if (err)
goto out_free_hmac;
c->authenticated = true;
c->log_hash = ubifs_hash_get_desc(c);
if (IS_ERR(c->log_hash)) {
err = PTR_ERR(c->log_hash);
goto out_free_hmac;
}
err = 0;
out_free_hmac:
if (err)
crypto_free_shash(c->hmac_tfm);
out_free_hash:
if (err)
crypto_free_shash(c->hash_tfm);
out:
up_read(&keyring_key->sem);
key_put(keyring_key);
return err;
}
/**
* __ubifs_exit_authentication - release resource
* @c: UBIFS file-system description object
*
* This function releases the authentication related resources.
*/
void __ubifs_exit_authentication(struct ubifs_info *c)
{
if (!ubifs_authenticated(c))
return;
crypto_free_shash(c->hmac_tfm);
crypto_free_shash(c->hash_tfm);
kfree(c->log_hash);
}
/**
* ubifs_node_calc_hmac - calculate the HMAC of a UBIFS node
* @c: UBIFS file-system description object
* @node: the node to insert a HMAC into.
* @len: the length of the node
* @ofs_hmac: the offset in the node where the HMAC is inserted
* @hmac: returned HMAC
*
* This function calculates a HMAC of a UBIFS node. The HMAC is expected to be
* embedded into the node, so this area is not covered by the HMAC. Also not
* covered is the UBIFS_NODE_MAGIC and the CRC of the node.
*/
static int ubifs_node_calc_hmac(const struct ubifs_info *c, const void *node,
int len, int ofs_hmac, void *hmac)
{
SHASH_DESC_ON_STACK(shash, c->hmac_tfm);
int hmac_len = c->hmac_desc_len;
int err;
ubifs_assert(c, ofs_hmac > 8);
ubifs_assert(c, ofs_hmac + hmac_len < len);
shash->tfm = c->hmac_tfm;
err = crypto_shash_init(shash);
if (err)
return err;
/* behind common node header CRC up to HMAC begin */
err = crypto_shash_update(shash, node + 8, ofs_hmac - 8);
if (err < 0)
return err;
/* behind HMAC, if any */
if (len - ofs_hmac - hmac_len > 0) {
err = crypto_shash_update(shash, node + ofs_hmac + hmac_len,
len - ofs_hmac - hmac_len);
if (err < 0)
return err;
}
return crypto_shash_final(shash, hmac);
}
/**
* __ubifs_node_insert_hmac - insert a HMAC into a UBIFS node
* @c: UBIFS file-system description object
* @node: the node to insert a HMAC into.
* @len: the length of the node
* @ofs_hmac: the offset in the node where the HMAC is inserted
*
* This function inserts a HMAC at offset @ofs_hmac into the node given in
* @node.
*
* This function returns 0 for success or a negative error code otherwise.
*/
int __ubifs_node_insert_hmac(const struct ubifs_info *c, void *node, int len,
int ofs_hmac)
{
return ubifs_node_calc_hmac(c, node, len, ofs_hmac, node + ofs_hmac);
}
/**
* __ubifs_node_verify_hmac - verify the HMAC of UBIFS node
* @c: UBIFS file-system description object
* @node: the node to insert a HMAC into.
* @len: the length of the node
* @ofs_hmac: the offset in the node where the HMAC is inserted
*
* This function verifies the HMAC at offset @ofs_hmac of the node given in
* @node. Returns 0 if successful or a negative error code otherwise.
*/
int __ubifs_node_verify_hmac(const struct ubifs_info *c, const void *node,
int len, int ofs_hmac)
{
int hmac_len = c->hmac_desc_len;
u8 *hmac;
int err;
hmac = kmalloc(hmac_len, GFP_NOFS);
if (!hmac)
return -ENOMEM;
err = ubifs_node_calc_hmac(c, node, len, ofs_hmac, hmac);
if (err) {
kfree(hmac);
return err;
}
err = crypto_memneq(hmac, node + ofs_hmac, hmac_len);
kfree(hmac);
if (!err)
return 0;
return -EPERM;
}
int __ubifs_shash_copy_state(const struct ubifs_info *c, struct shash_desc *src,
struct shash_desc *target)
{
u8 *state;
int err;
state = kmalloc(crypto_shash_descsize(src->tfm), GFP_NOFS);
if (!state)
return -ENOMEM;
err = crypto_shash_export(src, state);
if (err)
goto out;
err = crypto_shash_import(target, state);
out:
kfree(state);
return err;
}
/**
* ubifs_hmac_wkm - Create a HMAC of the well known message
* @c: UBIFS file-system description object
* @hmac: The HMAC of the well known message
*
* This function creates a HMAC of a well known message. This is used
* to check if the provided key is suitable to authenticate a UBIFS
* image. This is only a convenience to the user to provide a better
* error message when the wrong key is provided.
*
* This function returns 0 for success or a negative error code otherwise.
*/
int ubifs_hmac_wkm(struct ubifs_info *c, u8 *hmac)
{
const char well_known_message[] = "UBIFS";
if (!ubifs_authenticated(c))
return 0;
return crypto_shash_tfm_digest(c->hmac_tfm, well_known_message,
sizeof(well_known_message) - 1, hmac);
}
/*
* ubifs_hmac_zero - test if a HMAC is zero
* @c: UBIFS file-system description object
* @hmac: the HMAC to test
*
* This function tests if a HMAC is zero and returns true if it is
* and false otherwise.
*/
bool ubifs_hmac_zero(struct ubifs_info *c, const u8 *hmac)
{
return !memchr_inv(hmac, 0, c->hmac_desc_len);
}
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