547 lines
14 KiB
C
547 lines
14 KiB
C
// 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 <s.hauer@pengutronix.de>
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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)
|
|
{
|
|
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);
|
|
}
|