// 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_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;

/**
 * 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 *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);
}

#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 *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);
}

/**
 * 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");

        restriction->check = restrict_link_by_builtin_and_secondary_trusted;

        return restriction;
}
#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);

/*
 * 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\n");

        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)\n",
                               PTR_ERR(key));
                } else {
                        pr_notice("Loaded X.509 cert '%s'\n",
                                  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\n");
        return 0;
}
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;

        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