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

  /* Instantiate a public key crypto key from an X.509 Certificate
   *

   * Copyright (C) 2012, 2016 Red Hat, Inc. All Rights Reserved.

   * Written by David Howells (dhowells@redhat.com)

   */

  #define pr_fmt(fmt) "ASYM: "fmt

  #include <linux/module.h>
  #include <linux/kernel.h>

  #include <linux/err.h>

  #include <crypto/public_key.h>
  #include "asymmetric_keys.h"

  
  static bool use_builtin_keys;
  static struct asymmetric_key_id *ca_keyid;
  
  #ifndef MODULE
  static struct {
  	struct asymmetric_key_id id;
  	unsigned char data[10];
  } cakey;
  
  static int __init ca_keys_setup(char *str)
  {
  	if (!str)		/* default system keyring */
  		return 1;
  
  	if (strncmp(str, "id:", 3) == 0) {
  		struct asymmetric_key_id *p = &cakey.id;
  		size_t hexlen = (strlen(str) - 3) / 2;
  		int ret;
  
  		if (hexlen == 0 || hexlen > sizeof(cakey.data)) {
  			pr_err("Missing or invalid ca_keys id
  ");
  			return 1;
  		}
  
  		ret = __asymmetric_key_hex_to_key_id(str + 3, p, hexlen);
  		if (ret < 0)
  			pr_err("Unparsable ca_keys id hex string
  ");
  		else
  			ca_keyid = p;	/* owner key 'id:xxxxxx' */
  	} else if (strcmp(str, "builtin") == 0) {
  		use_builtin_keys = true;
  	}
  
  	return 1;
  }
  __setup("ca_keys=", ca_keys_setup);
  #endif

  /**
   * restrict_link_by_signature - Restrict additions to a ring of public keys

   * @dest_keyring: Keyring being linked to.

   * @type: The type of key being added.
   * @payload: The payload of the new key.

   * @trust_keyring: A ring of keys that can be used to vouch for the new cert.

   *

   * Check the new certificate against the ones in the trust keyring.  If one of
   * those is the signing key and validates the new certificate, then mark the
   * new certificate as being trusted.
   *

   * Returns 0 if the new certificate was accepted, -ENOKEY if we couldn't find a
   * matching parent certificate in the trusted list, -EKEYREJECTED if the

   * signature check fails or the key is blacklisted, -ENOPKG if the signature
   * uses unsupported crypto, or some other error if there is a matching
   * certificate but the signature check cannot be performed.

   */

  int restrict_link_by_signature(struct key *dest_keyring,

  			       const struct key_type *type,

  			       const union key_payload *payload,
  			       struct key *trust_keyring)

  {

  	const struct public_key_signature *sig;

  	struct key *key;

  	int ret;

  	pr_devel("==>%s()
  ", __func__);

  
  	if (!trust_keyring)

  		return -ENOKEY;
  
  	if (type != &key_type_asymmetric)

  		return -EOPNOTSUPP;

  
  	sig = payload->data[asym_auth];

  	if (!sig)
  		return -ENOPKG;

  	if (!sig->auth_ids[0] && !sig->auth_ids[1])

  		return -ENOKEY;

  	if (ca_keyid && !asymmetric_key_id_partial(sig->auth_ids[1], ca_keyid))
  		return -EPERM;

  	/* See if we have a key that signed this one. */

  	key = find_asymmetric_key(trust_keyring,
  				  sig->auth_ids[0], sig->auth_ids[1],
  				  false);
  	if (IS_ERR(key))

  		return -ENOKEY;

  	if (use_builtin_keys && !test_bit(KEY_FLAG_BUILTIN, &key->flags))
  		ret = -ENOKEY;
  	else
  		ret = verify_signature(key, sig);

  	key_put(key);
  	return ret;
  }

  static bool match_either_id(const struct asymmetric_key_ids *pair,
  			    const struct asymmetric_key_id *single)
  {
  	return (asymmetric_key_id_same(pair->id[0], single) ||
  		asymmetric_key_id_same(pair->id[1], single));
  }
  
  static int key_or_keyring_common(struct key *dest_keyring,
  				 const struct key_type *type,
  				 const union key_payload *payload,
  				 struct key *trusted, bool check_dest)

  {
  	const struct public_key_signature *sig;

  	struct key *key = NULL;

  	int ret;
  
  	pr_devel("==>%s()
  ", __func__);
  
  	if (!dest_keyring)
  		return -ENOKEY;
  	else if (dest_keyring->type != &key_type_keyring)
  		return -EOPNOTSUPP;

  	if (!trusted && !check_dest)

  		return -ENOKEY;
  
  	if (type != &key_type_asymmetric)
  		return -EOPNOTSUPP;
  
  	sig = payload->data[asym_auth];

  	if (!sig)
  		return -ENOPKG;

  	if (!sig->auth_ids[0] && !sig->auth_ids[1])
  		return -ENOKEY;

  	if (trusted) {
  		if (trusted->type == &key_type_keyring) {
  			/* See if we have a key that signed this one. */
  			key = find_asymmetric_key(trusted, sig->auth_ids[0],
  						  sig->auth_ids[1], false);
  			if (IS_ERR(key))
  				key = NULL;
  		} else if (trusted->type == &key_type_asymmetric) {
  			const struct asymmetric_key_ids *signer_ids;

  			signer_ids = asymmetric_key_ids(trusted);

  			/*
  			 * The auth_ids come from the candidate key (the
  			 * one that is being considered for addition to
  			 * dest_keyring) and identify the key that was
  			 * used to sign.
  			 *
  			 * The signer_ids are identifiers for the
  			 * signing key specified for dest_keyring.
  			 *
  			 * The first auth_id is the preferred id, and
  			 * the second is the fallback. If only one
  			 * auth_id is present, it may match against
  			 * either signer_id. If two auth_ids are
  			 * present, the first auth_id must match one
  			 * signer_id and the second auth_id must match
  			 * the second signer_id.
  			 */
  			if (!sig->auth_ids[0] || !sig->auth_ids[1]) {
  				const struct asymmetric_key_id *auth_id;

  				auth_id = sig->auth_ids[0] ?: sig->auth_ids[1];
  				if (match_either_id(signer_ids, auth_id))
  					key = __key_get(trusted);
  
  			} else if (asymmetric_key_id_same(signer_ids->id[1],
  							  sig->auth_ids[1]) &&
  				   match_either_id(signer_ids,
  						   sig->auth_ids[0])) {
  				key = __key_get(trusted);
  			}
  		} else {
  			return -EOPNOTSUPP;
  		}

  	}

  	if (check_dest && !key) {
  		/* See if the destination has a key that signed this one. */
  		key = find_asymmetric_key(dest_keyring, sig->auth_ids[0],
  					  sig->auth_ids[1], false);
  		if (IS_ERR(key))
  			key = NULL;
  	}
  
  	if (!key)
  		return -ENOKEY;

  	ret = key_validate(key);
  	if (ret == 0)
  		ret = verify_signature(key, sig);
  
  	key_put(key);
  	return ret;
  }

  
  /**
   * restrict_link_by_key_or_keyring - Restrict additions to a ring of public
   * keys using the restrict_key information stored in the ring.
   * @dest_keyring: Keyring being linked to.
   * @type: The type of key being added.
   * @payload: The payload of the new key.
   * @trusted: A key or ring of keys that can be used to vouch for the new cert.
   *
   * Check the new certificate only against the key or keys passed in the data
   * parameter. If one of those is the signing key and validates the new
   * certificate, then mark the new certificate as being ok to link.
   *
   * Returns 0 if the new certificate was accepted, -ENOKEY if we
   * couldn't find a matching parent certificate in the trusted list,

   * -EKEYREJECTED if the signature check fails, -ENOPKG if the signature uses
   * unsupported crypto, or some other error if there is a matching certificate
   * but the signature check cannot be performed.

   */
  int restrict_link_by_key_or_keyring(struct key *dest_keyring,
  				    const struct key_type *type,
  				    const union key_payload *payload,
  				    struct key *trusted)
  {
  	return key_or_keyring_common(dest_keyring, type, payload, trusted,
  				     false);
  }
  
  /**
   * restrict_link_by_key_or_keyring_chain - Restrict additions to a ring of
   * public keys using the restrict_key information stored in the ring.
   * @dest_keyring: Keyring being linked to.
   * @type: The type of key being added.
   * @payload: The payload of the new key.
   * @trusted: A key or ring of keys that can be used to vouch for the new cert.
   *

   * Check the new certificate against the key or keys passed in the data
   * parameter and against the keys already linked to the destination keyring. If
   * one of those is the signing key and validates the new certificate, then mark
   * the new certificate as being ok to link.

   *
   * Returns 0 if the new certificate was accepted, -ENOKEY if we
   * couldn't find a matching parent certificate in the trusted list,

   * -EKEYREJECTED if the signature check fails, -ENOPKG if the signature uses
   * unsupported crypto, or some other error if there is a matching certificate
   * but the signature check cannot be performed.

   */
  int restrict_link_by_key_or_keyring_chain(struct key *dest_keyring,
  					  const struct key_type *type,
  					  const union key_payload *payload,
  					  struct key *trusted)
  {
  	return key_or_keyring_common(dest_keyring, type, payload, trusted,
  				     true);
  }