// SPDX-License-Identifier: GPL-2.0-or-later

  /* System hash blacklist.
   *
   * Copyright (C) 2016 Red Hat, Inc. All Rights Reserved.
   * Written by David Howells (dhowells@redhat.com)

   */
  
  #define pr_fmt(fmt) "blacklist: "fmt
  #include <linux/module.h>
  #include <linux/slab.h>
  #include <linux/key.h>
  #include <linux/key-type.h>
  #include <linux/sched.h>
  #include <linux/ctype.h>
  #include <linux/err.h>
  #include <linux/seq_file.h>
  #include <keys/system_keyring.h>
  #include "blacklist.h"
  
  static struct key *blacklist_keyring;
  
  /*
   * The description must be a type prefix, a colon and then an even number of
   * hex digits.  The hash is kept in the description.
   */
  static int blacklist_vet_description(const char *desc)
  {
  	int n = 0;
  
  	if (*desc == ':')
  		return -EINVAL;
  	for (; *desc; desc++)
  		if (*desc == ':')
  			goto found_colon;
  	return -EINVAL;
  
  found_colon:
  	desc++;
  	for (; *desc; desc++) {
  		if (!isxdigit(*desc))
  			return -EINVAL;
  		n++;
  	}
  
  	if (n == 0 || n & 1)
  		return -EINVAL;
  	return 0;
  }
  
  /*
   * The hash to be blacklisted is expected to be in the description.  There will
   * be no payload.
   */
  static int blacklist_preparse(struct key_preparsed_payload *prep)
  {
  	if (prep->datalen > 0)
  		return -EINVAL;
  	return 0;
  }
  
  static void blacklist_free_preparse(struct key_preparsed_payload *prep)
  {
  }
  
  static void blacklist_describe(const struct key *key, struct seq_file *m)
  {
  	seq_puts(m, key->description);
  }
  
  static struct key_type key_type_blacklist = {
  	.name			= "blacklist",
  	.vet_description	= blacklist_vet_description,
  	.preparse		= blacklist_preparse,
  	.free_preparse		= blacklist_free_preparse,
  	.instantiate		= generic_key_instantiate,
  	.describe		= blacklist_describe,
  };
  
  /**
   * mark_hash_blacklisted - Add a hash to the system blacklist
   * @hash - The hash as a hex string with a type prefix (eg. "tbs:23aa429783")
   */
  int mark_hash_blacklisted(const char *hash)
  {
  	key_ref_t key;
  
  	key = key_create_or_update(make_key_ref(blacklist_keyring, true),
  				   "blacklist",
  				   hash,
  				   NULL,
  				   0,

  				   ((KEY_POS_ALL & ~KEY_POS_SETATTR) |
  				    KEY_USR_VIEW),

  				   KEY_ALLOC_NOT_IN_QUOTA |
  				   KEY_ALLOC_BUILT_IN);
  	if (IS_ERR(key)) {
  		pr_err("Problem blacklisting hash (%ld)
  ", PTR_ERR(key));
  		return PTR_ERR(key);
  	}
  	return 0;
  }
  
  /**
   * is_hash_blacklisted - Determine if a hash is blacklisted
   * @hash: The hash to be checked as a binary blob
   * @hash_len: The length of the binary hash
   * @type: Type of hash
   */
  int is_hash_blacklisted(const u8 *hash, size_t hash_len, const char *type)
  {
  	key_ref_t kref;
  	size_t type_len = strlen(type);
  	char *buffer, *p;
  	int ret = 0;
  
  	buffer = kmalloc(type_len + 1 + hash_len * 2 + 1, GFP_KERNEL);
  	if (!buffer)
  		return -ENOMEM;
  	p = memcpy(buffer, type, type_len);
  	p += type_len;
  	*p++ = ':';
  	bin2hex(p, hash, hash_len);
  	p += hash_len * 2;
  	*p = 0;
  
  	kref = keyring_search(make_key_ref(blacklist_keyring, true),

  			      &key_type_blacklist, buffer, false);

  	if (!IS_ERR(kref)) {
  		key_ref_put(kref);
  		ret = -EKEYREJECTED;
  	}
  
  	kfree(buffer);
  	return ret;
  }
  EXPORT_SYMBOL_GPL(is_hash_blacklisted);

  int is_binary_blacklisted(const u8 *hash, size_t hash_len)
  {
  	if (is_hash_blacklisted(hash, hash_len, "bin") == -EKEYREJECTED)
  		return -EPERM;
  
  	return 0;
  }
  EXPORT_SYMBOL_GPL(is_binary_blacklisted);

  /*

   * Initialise the blacklist

   */
  static int __init blacklist_init(void)
  {
  	const char *const *bl;
  
  	if (register_key_type(&key_type_blacklist) < 0)
  		panic("Can't allocate system blacklist key type
  ");
  
  	blacklist_keyring =
  		keyring_alloc(".blacklist",
  			      KUIDT_INIT(0), KGIDT_INIT(0),
  			      current_cred(),

  			      (KEY_POS_ALL & ~KEY_POS_SETATTR) |
  			      KEY_USR_VIEW | KEY_USR_READ |
  			      KEY_USR_SEARCH,

  			      KEY_ALLOC_NOT_IN_QUOTA |
  			      KEY_FLAG_KEEP,
  			      NULL, NULL);
  	if (IS_ERR(blacklist_keyring))
  		panic("Can't allocate system blacklist keyring
  ");
  
  	for (bl = blacklist_hashes; *bl; bl++)
  		if (mark_hash_blacklisted(*bl) < 0)
  			pr_err("- blacklisting failed
  ");
  	return 0;
  }
  
  /*
   * Must be initialised before we try and load the keys into the keyring.
   */
  device_initcall(blacklist_init);