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-rw-r--r--fs/ubifs/auth.c546
1 files changed, 546 insertions, 0 deletions
diff --git a/fs/ubifs/auth.c b/fs/ubifs/auth.c
new file mode 100644
index 000000000..e564d5ff8
--- /dev/null
+++ b/fs/ubifs/auth.c
@@ -0,0 +1,546 @@
+// 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/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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