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- // SPDX-License-Identifier: GPL-2.0
- /*
- * This file is part of UBIFS.
- *
- * Copyright (C) 2018 Pengutronix, Sascha Hauer <s.hauer@pengutronix.de>
- */
- /*
- * This file implements various helper functions for UBIFS authentication support
- */
- #include <linux/crypto.h>
- #include <linux/verification.h>
- #include <crypto/hash.h>
- #include <crypto/sha.h>
- #include <crypto/algapi.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)
- {
- SHASH_DESC_ON_STACK(shash, c->hmac_tfm);
- int err;
- const char well_known_message[] = "UBIFS";
- if (!ubifs_authenticated(c))
- return 0;
- shash->tfm = c->hmac_tfm;
- err = crypto_shash_init(shash);
- if (err)
- return err;
- err = crypto_shash_update(shash, well_known_message,
- sizeof(well_known_message) - 1);
- if (err < 0)
- return err;
- err = crypto_shash_final(shash, hmac);
- if (err)
- return err;
- return 0;
- }
- /*
- * 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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