Quelle system_keyring.c Sprache: C

// SPDX-License-Identifier: GPL-2.0-or-later
/* System trusted keyring for trusted public keys
*
* Copyright (C) 2012 Red Hat, Inc. All Rights Reserved.
* Written by David Howells (dhowells@redhat.com)
*/

#include <linux/export.h>
#include <linux/kernel.h>
#include <linux/sched.h>
#include <linux/cred.h>
#include <linux/err.h>
#include <linux/slab.h>
#include <linux/uidgid.h>
#include <linux/verification.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
#ifdef CONFIG_INTEGRITY_MACHINE_KEYRING
static struct key *machine_trusted_keys;
#endif
#ifdef CONFIG_INTEGRITY_PLATFORM_KEYRING
static struct key *platform_trusted_keys;
#endif

extern __initconst const u8 system_certificate_list[];
extern __initconst const unsigned long system_certificate_list_size;
extern __initconst const unsigned long module_cert_size;

/**
* restrict_link_by_builtin_trusted - Restrict keyring addition by built-in CA
* @dest_keyring: Keyring being linked to.
* @type: The type of key being added.
* @payload: The payload of the new key.
* @restriction_key: A ring of keys that can be used to vouch for the new cert.
*
* 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 *dest_keyring,
         const struct key_type *type,
         const union key_payload *payload,
         struct key *restriction_key)
{
return restrict_link_by_signature(dest_keyring, type, payload,
       builtin_trusted_keys);
}

/**
* restrict_link_by_digsig_builtin - Restrict digitalSignature key additions by the built-in keyring
* @dest_keyring: Keyring being linked to.
* @type: The type of key being added.
* @payload: The payload of the new key.
* @restriction_key: A ring of keys that can be used to vouch for the new cert.
*
* 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. The new key
* must have the digitalSignature usage field set.
*/
int restrict_link_by_digsig_builtin(struct key *dest_keyring,
        const struct key_type *type,
        const union key_payload *payload,
        struct key *restriction_key)
{
return restrict_link_by_digsig(dest_keyring, type, payload,
           builtin_trusted_keys);
}

#ifdef CONFIG_SECONDARY_TRUSTED_KEYRING
/**
* restrict_link_by_builtin_and_secondary_trusted - Restrict keyring
*   addition by both built-in and secondary keyrings.
* @dest_keyring: Keyring being linked to.
* @type: The type of key being added.
* @payload: The payload of the new key.
* @restrict_key: A ring of keys that can be used to vouch for the new cert.
*
* 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 *dest_keyring,
const struct key_type *type,
const union key_payload *payload,
struct key *restrict_key)
{
/* 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 &&
     dest_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(dest_keyring, type, payload,
       secondary_trusted_keys);
}

/**
* restrict_link_by_digsig_builtin_and_secondary - Restrict by digitalSignature.
* @dest_keyring: Keyring being linked to.
* @type: The type of key being added.
* @payload: The payload of the new key.
* @restrict_key: A ring of keys that can be used to vouch for the new cert.
*
* 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. The new key must have the digitalSignature usage field set.
*/
int restrict_link_by_digsig_builtin_and_secondary(struct key *dest_keyring,
        const struct key_type *type,
        const union key_payload *payload,
        struct key *restrict_key)
{
/* 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 &&
     dest_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_digsig(dest_keyring, type, payload,
           secondary_trusted_keys);
}

/*
* Allocate a struct key_restriction for the "builtin and secondary trust"
* keyring. Only for use in system_trusted_keyring_init().
*/
static __init struct key_restriction *get_builtin_and_secondary_restriction(void)
{
struct key_restriction *restriction;

restriction = kzalloc(sizeof(struct key_restriction), GFP_KERNEL);

if (!restriction)
  panic("Can't allocate secondary trusted keyring restriction\n");

if (IS_ENABLED(CONFIG_INTEGRITY_MACHINE_KEYRING))
  restriction->check = restrict_link_by_builtin_secondary_and_machine;
else
  restriction->check = restrict_link_by_builtin_and_secondary_trusted;

return restriction;
}

/**
* add_to_secondary_keyring - Add to secondary keyring.
* @source: Source of key
* @data: The blob holding the key
* @len: The length of the data blob
*
* Add a key to the secondary keyring. The key must be vouched for by a key in the builtin,
* machine or secondary keyring itself.
*/
void __init add_to_secondary_keyring(const char *source, const void *data, size_t len)
{
key_ref_t key;
key_perm_t perm;

perm = (KEY_POS_ALL & ~KEY_POS_SETATTR) | KEY_USR_VIEW;

key = key_create_or_update(make_key_ref(secondary_trusted_keys, 1),
       "asymmetric",
       NULL, data, len, perm,
       KEY_ALLOC_NOT_IN_QUOTA);
if (IS_ERR(key)) {
  pr_err("Problem loading X.509 certificate from %s to secondary keyring %ld\n",
         source, PTR_ERR(key));
  return;
}

pr_notice("Loaded X.509 cert '%s'\n", key_ref_to_ptr(key)->description);
key_ref_put(key);
}
#endif
#ifdef CONFIG_INTEGRITY_MACHINE_KEYRING
void __init set_machine_trusted_keys(struct key *keyring)
{
machine_trusted_keys = keyring;

if (key_link(secondary_trusted_keys, machine_trusted_keys) < 0)
  panic("Can't link (machine) trusted keyrings\n");
}

/**
* restrict_link_by_builtin_secondary_and_machine - Restrict keyring addition.
* @dest_keyring: Keyring being linked to.
* @type: The type of key being added.
* @payload: The payload of the new key.
* @restrict_key: A ring of keys that can be used to vouch for the new cert.
*
* 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, the secondary, or
* the machine keyrings.
*/
int restrict_link_by_builtin_secondary_and_machine(
struct key *dest_keyring,
const struct key_type *type,
const union key_payload *payload,
struct key *restrict_key)
{
if (machine_trusted_keys && type == &key_type_keyring &&
     dest_keyring == secondary_trusted_keys &&
     payload == &machine_trusted_keys->payload)
  /* Allow the machine keyring to be added to the secondary */
  return 0;

return restrict_link_by_builtin_and_secondary_trusted(dest_keyring, type,
             payload, restrict_key);
}
#endif

/*
* Create the trusted keyrings
*/
static __init int system_trusted_keyring_init(void)
{
pr_notice("Initialise system trusted keyrings\n");

builtin_trusted_keys =
  keyring_alloc(".builtin_trusted_keys",
         GLOBAL_ROOT_UID, GLOBAL_ROOT_GID, 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\n");

#ifdef CONFIG_SECONDARY_TRUSTED_KEYRING
secondary_trusted_keys =
  keyring_alloc(".secondary_trusted_keys",
         GLOBAL_ROOT_UID, GLOBAL_ROOT_GID, 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,
         get_builtin_and_secondary_restriction(),
         NULL);
if (IS_ERR(secondary_trusted_keys))
  panic("Can't allocate secondary trusted keyring\n");

if (key_link(secondary_trusted_keys, builtin_trusted_keys) < 0)
  panic("Can't link trusted keyrings\n");
#endif

return 0;
}

/*
* Must be initialised before we try and load the keys into the keyring.
*/
device_initcall(system_trusted_keyring_init);

__init int load_module_cert(struct key *keyring)
{
if (!IS_ENABLED(CONFIG_IMA_APPRAISE_MODSIG))
  return 0;

pr_notice("Loading compiled-in module X.509 certificates\n");

return x509_load_certificate_list(system_certificate_list,
       module_cert_size, keyring);
}

/*
* Load the compiled-in list of X.509 certificates.
*/
static __init int load_system_certificate_list(void)
{
const u8 *p;
unsigned long size;

pr_notice("Loading compiled-in X.509 certificates\n");

#ifdef CONFIG_MODULE_SIG
p = system_certificate_list;
size = system_certificate_list_size;
#else
p = system_certificate_list + module_cert_size;
size = system_certificate_list_size - module_cert_size;
#endif

return x509_load_certificate_list(p, size, builtin_trusted_keys);
}
late_initcall(load_system_certificate_list);

#ifdef CONFIG_SYSTEM_DATA_VERIFICATION

/**
* verify_pkcs7_message_sig - Verify a PKCS#7-based signature on system data.
* @data: The data to be verified (NULL if expecting internal data).
* @len: Size of @data.
* @pkcs7: The PKCS#7 message that is the signature.
* @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_message_sig(const void *data, size_t len,
        struct pkcs7_message *pkcs7,
        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)
{
int ret;

/* 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\n");
  ret = -EBADMSG;
  goto error;
}

ret = pkcs7_verify(pkcs7, usage);
if (ret < 0)
  goto error;

ret = is_key_on_revocation_list(pkcs7);
if (ret != -ENOKEY) {
  pr_devel("PKCS#7 key is on revocation list\n");
  goto error;
}

if (!trusted_keys) {
  trusted_keys = builtin_trusted_keys;
} else if (trusted_keys == VERIFY_USE_SECONDARY_KEYRING) {
#ifdef CONFIG_SECONDARY_TRUSTED_KEYRING
  trusted_keys = secondary_trusted_keys;
#else
  trusted_keys = builtin_trusted_keys;
#endif
} else if (trusted_keys == VERIFY_USE_PLATFORM_KEYRING) {
#ifdef CONFIG_INTEGRITY_PLATFORM_KEYRING
  trusted_keys = platform_trusted_keys;
#else
  trusted_keys = NULL;
#endif
  if (!trusted_keys) {
   ret = -ENOKEY;
   pr_devel("PKCS#7 platform keyring is not available\n");
   goto error;
  }
}
ret = pkcs7_validate_trust(pkcs7, trusted_keys);
if (ret < 0) {
  if (ret == -ENOKEY)
   pr_devel("PKCS#7 signature not signed with a trusted key\n");
  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\n");
   goto error;
  }

  ret = view_content(ctx, data, len, asn1hdrlen);
}

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

/**
* 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);

ret = verify_pkcs7_message_sig(data, len, pkcs7, trusted_keys, usage,
           view_content, ctx);

pkcs7_free_message(pkcs7);
pr_devel("<==%s() = %d\n", __func__, ret);
return ret;
}
EXPORT_SYMBOL_GPL(verify_pkcs7_signature);

#endif /* CONFIG_SYSTEM_DATA_VERIFICATION */

#ifdef CONFIG_INTEGRITY_PLATFORM_KEYRING
void __init set_platform_trusted_keys(struct key *keyring)
{
platform_trusted_keys = keyring;
}
#endif

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