// 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 <linux/uidgid.h>
#include <keys/system_keyring.h>
#include "blacklist.h"
#include "common.h"

static struct key *blacklist_keyring;

#ifdef CONFIG_SYSTEM_REVOCATION_LIST
extern __initconst const u8 revocation_certificate_list[];
extern __initconst const unsigned long revocation_certificate_list_size;
#endif

/*
 * 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) || isupper(*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)\n", 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);

#ifdef CONFIG_SYSTEM_REVOCATION_LIST
/**
 * add_key_to_revocation_list - Add a revocation certificate to the blacklist
 * @data: The data blob containing the certificate
 * @size: The size of data blob
 */
int add_key_to_revocation_list(const char *data, size_t size)
{
        key_ref_t key;

        key = key_create_or_update(make_key_ref(blacklist_keyring, true),
                                   "asymmetric",
                                   NULL,
                                   data,
                                   size,
                                   ((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 with revocation key (%ld)\n", PTR_ERR(key));
                return PTR_ERR(key);
        }

        return 0;
}

/**
 * is_key_on_revocation_list - Determine if the key for a PKCS#7 message is revoked
 * @pkcs7: The PKCS#7 message to check
 */
int is_key_on_revocation_list(struct pkcs7_message *pkcs7)
{
        int ret;

        ret = pkcs7_validate_trust(pkcs7, blacklist_keyring);

        if (ret == 0)
                return -EKEYREJECTED;

        return -ENOKEY;
}
#endif

/*
 * 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\n");

        blacklist_keyring =
                keyring_alloc(".blacklist",
                              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 |
                              KEY_ALLOC_SET_KEEP,
                              NULL, NULL);
        if (IS_ERR(blacklist_keyring))
                panic("Can't allocate system blacklist keyring\n");

        for (bl = blacklist_hashes; *bl; bl++)
                if (mark_hash_blacklisted(*bl) < 0)
                        pr_err("- blacklisting failed\n");
        return 0;
}

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

#ifdef CONFIG_SYSTEM_REVOCATION_LIST
/*
 * Load the compiled-in list of revocation X.509 certificates.
 */
static __init int load_revocation_certificate_list(void)
{
        if (revocation_certificate_list_size)
                pr_notice("Loading compiled-in revocation X.509 certificates\n");

        return load_certificate_list(revocation_certificate_list, revocation_certificate_list_size,
                                     blacklist_keyring);
}
late_initcall(load_revocation_certificate_list);
#endif