// 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; SHASH_DESC_ON_STACK(shash, c->hash_tfm); int err; shash->tfm = c->hash_tfm; err = crypto_shash_digest(shash, node, le32_to_cpu(ch->len), hash); if (err < 0) return err; return 0; } /** * 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) { SHASH_DESC_ON_STACK(shash, c->hmac_tfm); int err; shash->tfm = c->hmac_tfm; err = crypto_shash_digest(shash, hash, c->hash_len, hmac); if (err < 0) return err; return 0; } /** * ubifs_prepare_auth_node - Prepare an authentication node * @c: UBIFS file-system description object * @node: the node to calculate a hash for * @hash: 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; int err; hash = kmalloc(crypto_shash_descsize(c->hash_tfm), GFP_NOFS); if (!hash) return -ENOMEM; { 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) goto out; } err = ubifs_hash_calc_hmac(c, hash, auth->hmac); if (err) goto out; auth->ch.node_type = UBIFS_AUTH_NODE; ubifs_prepare_node(c, auth, ubifs_auth_node_sz(c), 0); err = 0; out: kfree(hash); return err; } 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_hash; } 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)) 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); }