/* System trusted keyring for trusted public keys
   *
   * Copyright (C) 2012 Red Hat, Inc. All Rights Reserved.
   * Written by David Howells (dhowells@redhat.com)
   *
   * This program is free software; you can redistribute it and/or
   * modify it under the terms of the GNU General Public Licence
   * as published by the Free Software Foundation; either version
   * 2 of the Licence, or (at your option) any later version.
   */
  
  #include <linux/export.h>
  #include <linux/kernel.h>
  #include <linux/sched.h>
  #include <linux/cred.h>
  #include <linux/err.h>
  #include <keys/asymmetric-type.h>
  #include <keys/system_keyring.h>

  #include <crypto/pkcs7.h>

  static struct key *builtin_trusted_keys;
  #ifdef CONFIG_SECONDARY_TRUSTED_KEYRING
  static struct key *secondary_trusted_keys;
  #endif

  
  extern __initconst const u8 system_certificate_list[];

  extern __initconst const unsigned long system_certificate_list_size;

  /**

   * restrict_link_to_builtin_trusted - Restrict keyring addition by built in CA

   *
   * Restrict the addition of keys into a keyring based on the key-to-be-added

   * being vouched for by a key in the built in system keyring.

   */
  int restrict_link_by_builtin_trusted(struct key *keyring,
  				     const struct key_type *type,

  				     const union key_payload *payload)
  {

  	return restrict_link_by_signature(builtin_trusted_keys, type, payload);

  }

  #ifdef CONFIG_SECONDARY_TRUSTED_KEYRING
  /**
   * restrict_link_by_builtin_and_secondary_trusted - Restrict keyring
   *   addition by both builtin and secondary keyrings
   *
   * Restrict the addition of keys into a keyring based on the key-to-be-added
   * being vouched for by a key in either the built-in or the secondary system
   * keyrings.
   */
  int restrict_link_by_builtin_and_secondary_trusted(
  	struct key *keyring,
  	const struct key_type *type,
  	const union key_payload *payload)
  {
  	/* If we have a secondary trusted keyring, then that contains a link
  	 * through to the builtin keyring and the search will follow that link.
  	 */
  	if (type == &key_type_keyring &&
  	    keyring == secondary_trusted_keys &&
  	    payload == &builtin_trusted_keys->payload)
  		/* Allow the builtin keyring to be added to the secondary */
  		return 0;
  
  	return restrict_link_by_signature(secondary_trusted_keys, type, payload);
  }
  #endif

  /*

   * Create the trusted keyrings

   */
  static __init int system_trusted_keyring_init(void)
  {

  	pr_notice("Initialise system trusted keyrings
  ");

  	builtin_trusted_keys =
  		keyring_alloc(".builtin_trusted_keys",

  			      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,

  			      NULL, NULL);
  	if (IS_ERR(builtin_trusted_keys))
  		panic("Can't allocate builtin trusted keyring
  ");
  
  #ifdef CONFIG_SECONDARY_TRUSTED_KEYRING
  	secondary_trusted_keys =
  		keyring_alloc(".secondary_trusted_keys",
  			      KUIDT_INIT(0), KGIDT_INIT(0), current_cred(),
  			      ((KEY_POS_ALL & ~KEY_POS_SETATTR) |
  			       KEY_USR_VIEW | KEY_USR_READ | KEY_USR_SEARCH |
  			       KEY_USR_WRITE),
  			      KEY_ALLOC_NOT_IN_QUOTA,
  			      restrict_link_by_builtin_and_secondary_trusted,
  			      NULL);
  	if (IS_ERR(secondary_trusted_keys))
  		panic("Can't allocate secondary trusted keyring
  ");
  
  	if (key_link(secondary_trusted_keys, builtin_trusted_keys) < 0)
  		panic("Can't link trusted keyrings
  ");
  #endif

  	return 0;
  }
  
  /*
   * Must be initialised before we try and load the keys into the keyring.
   */
  device_initcall(system_trusted_keyring_init);
  
  /*
   * Load the compiled-in list of X.509 certificates.
   */
  static __init int load_system_certificate_list(void)
  {
  	key_ref_t key;
  	const u8 *p, *end;
  	size_t plen;
  
  	pr_notice("Loading compiled-in X.509 certificates
  ");

  	p = system_certificate_list;

  	end = p + system_certificate_list_size;

  	while (p < end) {
  		/* Each cert begins with an ASN.1 SEQUENCE tag and must be more
  		 * than 256 bytes in size.
  		 */
  		if (end - p < 4)
  			goto dodgy_cert;
  		if (p[0] != 0x30 &&
  		    p[1] != 0x82)
  			goto dodgy_cert;
  		plen = (p[2] << 8) | p[3];
  		plen += 4;
  		if (plen > end - p)
  			goto dodgy_cert;

  		key = key_create_or_update(make_key_ref(builtin_trusted_keys, 1),

  					   "asymmetric",
  					   NULL,
  					   p,
  					   plen,

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

  					   KEY_ALLOC_NOT_IN_QUOTA |

  					   KEY_ALLOC_BUILT_IN |
  					   KEY_ALLOC_BYPASS_RESTRICTION);

  		if (IS_ERR(key)) {
  			pr_err("Problem loading in-kernel X.509 certificate (%ld)
  ",
  			       PTR_ERR(key));
  		} else {
  			pr_notice("Loaded X.509 cert '%s'
  ",
  				  key_ref_to_ptr(key)->description);
  			key_ref_put(key);
  		}
  		p += plen;
  	}
  
  	return 0;
  
  dodgy_cert:
  	pr_err("Problem parsing in-kernel X.509 certificate list
  ");
  	return 0;
  }
  late_initcall(load_system_certificate_list);

  
  #ifdef CONFIG_SYSTEM_DATA_VERIFICATION
  
  /**

   * verify_pkcs7_signature - Verify a PKCS#7-based signature on system data.
   * @data: The data to be verified (NULL if expecting internal data).

   * @len: Size of @data.
   * @raw_pkcs7: The PKCS#7 message that is the signature.
   * @pkcs7_len: The size of @raw_pkcs7.

   * @trusted_keys: Trusted keys to use (NULL for builtin trusted keys only,
   *					(void *)1UL for all trusted keys).

   * @usage: The use to which the key is being put.

   * @view_content: Callback to gain access to content.
   * @ctx: Context for callback.

   */

  int verify_pkcs7_signature(const void *data, size_t len,
  			   const void *raw_pkcs7, size_t pkcs7_len,
  			   struct key *trusted_keys,

  			   enum key_being_used_for usage,
  			   int (*view_content)(void *ctx,
  					       const void *data, size_t len,
  					       size_t asn1hdrlen),
  			   void *ctx)

  {
  	struct pkcs7_message *pkcs7;

  	int ret;
  
  	pkcs7 = pkcs7_parse_message(raw_pkcs7, pkcs7_len);
  	if (IS_ERR(pkcs7))
  		return PTR_ERR(pkcs7);
  
  	/* The data should be detached - so we need to supply it. */

  	if (data && pkcs7_supply_detached_data(pkcs7, data, len) < 0) {

  		pr_err("PKCS#7 signature with non-detached data
  ");
  		ret = -EBADMSG;
  		goto error;
  	}

  	ret = pkcs7_verify(pkcs7, usage);

  	if (ret < 0)
  		goto error;

  	if (!trusted_keys) {
  		trusted_keys = builtin_trusted_keys;
  	} else if (trusted_keys == (void *)1UL) {
  #ifdef CONFIG_SECONDARY_TRUSTED_KEYRING
  		trusted_keys = secondary_trusted_keys;
  #else
  		trusted_keys = builtin_trusted_keys;
  #endif
  	}

  	ret = pkcs7_validate_trust(pkcs7, trusted_keys);
  	if (ret < 0) {
  		if (ret == -ENOKEY)
  			pr_err("PKCS#7 signature not signed with a trusted key
  ");

  		goto error;
  	}
  
  	if (view_content) {
  		size_t asn1hdrlen;
  
  		ret = pkcs7_get_content_data(pkcs7, &data, &len, &asn1hdrlen);
  		if (ret < 0) {
  			if (ret == -ENODATA)
  				pr_devel("PKCS#7 message does not contain data
  ");
  			goto error;
  		}
  
  		ret = view_content(ctx, data, len, asn1hdrlen);

  	}
  
  error:
  	pkcs7_free_message(pkcs7);
  	pr_devel("<==%s() = %d
  ", __func__, ret);
  	return ret;
  }

  EXPORT_SYMBOL_GPL(verify_pkcs7_signature);

  
  #endif /* CONFIG_SYSTEM_DATA_VERIFICATION */