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The -EKEYREJECTED error returned by existing is_hash_blacklisted() is misleading when called for checking against blacklisted hash of a binary. This patch adds a wrapper function is_binary_blacklisted() to return -EPERM error if binary is blacklisted. Signed-off-by: Nayna Jain <nayna@linux.ibm.com> Reviewed-by: Mimi Zohar <zohar@linux.ibm.com> Signed-off-by: Michael Ellerman <mpe@ellerman.id.au> Link: https://lore.kernel.org/r/1572492694-6520-7-git-send-email-zohar@linux.ibm.com
180 lines
4.0 KiB
C
180 lines
4.0 KiB
C
// SPDX-License-Identifier: GPL-2.0-or-later
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/* System hash blacklist.
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*
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* Copyright (C) 2016 Red Hat, Inc. All Rights Reserved.
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* Written by David Howells (dhowells@redhat.com)
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*/
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#define pr_fmt(fmt) "blacklist: "fmt
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#include <linux/module.h>
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#include <linux/slab.h>
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#include <linux/key.h>
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#include <linux/key-type.h>
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#include <linux/sched.h>
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#include <linux/ctype.h>
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#include <linux/err.h>
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#include <linux/seq_file.h>
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#include <keys/system_keyring.h>
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#include "blacklist.h"
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static struct key *blacklist_keyring;
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/*
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* The description must be a type prefix, a colon and then an even number of
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* hex digits. The hash is kept in the description.
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*/
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static int blacklist_vet_description(const char *desc)
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{
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int n = 0;
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if (*desc == ':')
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return -EINVAL;
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for (; *desc; desc++)
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if (*desc == ':')
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goto found_colon;
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return -EINVAL;
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found_colon:
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desc++;
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for (; *desc; desc++) {
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if (!isxdigit(*desc))
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return -EINVAL;
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n++;
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}
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if (n == 0 || n & 1)
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return -EINVAL;
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return 0;
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}
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/*
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* The hash to be blacklisted is expected to be in the description. There will
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* be no payload.
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*/
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static int blacklist_preparse(struct key_preparsed_payload *prep)
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{
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if (prep->datalen > 0)
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return -EINVAL;
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return 0;
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}
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static void blacklist_free_preparse(struct key_preparsed_payload *prep)
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{
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}
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static void blacklist_describe(const struct key *key, struct seq_file *m)
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{
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seq_puts(m, key->description);
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}
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static struct key_type key_type_blacklist = {
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.name = "blacklist",
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.vet_description = blacklist_vet_description,
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.preparse = blacklist_preparse,
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.free_preparse = blacklist_free_preparse,
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.instantiate = generic_key_instantiate,
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.describe = blacklist_describe,
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};
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/**
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* mark_hash_blacklisted - Add a hash to the system blacklist
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* @hash - The hash as a hex string with a type prefix (eg. "tbs:23aa429783")
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*/
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int mark_hash_blacklisted(const char *hash)
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{
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key_ref_t key;
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key = key_create_or_update(make_key_ref(blacklist_keyring, true),
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"blacklist",
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hash,
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NULL,
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0,
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((KEY_POS_ALL & ~KEY_POS_SETATTR) |
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KEY_USR_VIEW),
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KEY_ALLOC_NOT_IN_QUOTA |
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KEY_ALLOC_BUILT_IN);
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if (IS_ERR(key)) {
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pr_err("Problem blacklisting hash (%ld)\n", PTR_ERR(key));
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return PTR_ERR(key);
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}
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return 0;
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}
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/**
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* is_hash_blacklisted - Determine if a hash is blacklisted
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* @hash: The hash to be checked as a binary blob
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* @hash_len: The length of the binary hash
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* @type: Type of hash
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*/
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int is_hash_blacklisted(const u8 *hash, size_t hash_len, const char *type)
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{
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key_ref_t kref;
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size_t type_len = strlen(type);
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char *buffer, *p;
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int ret = 0;
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buffer = kmalloc(type_len + 1 + hash_len * 2 + 1, GFP_KERNEL);
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if (!buffer)
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return -ENOMEM;
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p = memcpy(buffer, type, type_len);
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p += type_len;
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*p++ = ':';
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bin2hex(p, hash, hash_len);
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p += hash_len * 2;
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*p = 0;
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kref = keyring_search(make_key_ref(blacklist_keyring, true),
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&key_type_blacklist, buffer, false);
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if (!IS_ERR(kref)) {
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key_ref_put(kref);
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ret = -EKEYREJECTED;
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}
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kfree(buffer);
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return ret;
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}
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EXPORT_SYMBOL_GPL(is_hash_blacklisted);
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int is_binary_blacklisted(const u8 *hash, size_t hash_len)
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{
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if (is_hash_blacklisted(hash, hash_len, "bin") == -EKEYREJECTED)
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return -EPERM;
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return 0;
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}
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EXPORT_SYMBOL_GPL(is_binary_blacklisted);
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/*
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* Initialise the blacklist
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*/
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static int __init blacklist_init(void)
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{
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const char *const *bl;
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if (register_key_type(&key_type_blacklist) < 0)
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panic("Can't allocate system blacklist key type\n");
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blacklist_keyring =
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keyring_alloc(".blacklist",
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KUIDT_INIT(0), KGIDT_INIT(0),
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current_cred(),
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(KEY_POS_ALL & ~KEY_POS_SETATTR) |
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KEY_USR_VIEW | KEY_USR_READ |
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KEY_USR_SEARCH,
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KEY_ALLOC_NOT_IN_QUOTA |
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KEY_FLAG_KEEP,
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NULL, NULL);
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if (IS_ERR(blacklist_keyring))
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panic("Can't allocate system blacklist keyring\n");
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for (bl = blacklist_hashes; *bl; bl++)
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if (mark_hash_blacklisted(*bl) < 0)
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pr_err("- blacklisting failed\n");
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return 0;
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}
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/*
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* Must be initialised before we try and load the keys into the keyring.
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*/
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device_initcall(blacklist_init);
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