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