| // 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/asymmetric-type.h> |
| #include <keys/system_keyring.h> |
| #include "blacklist.h" |
| |
| /* |
| * According to crypto/asymmetric_keys/x509_cert_parser.c:x509_note_pkey_algo(), |
| * the size of the currently longest supported hash algorithm is 512 bits, |
| * which translates into 128 hex characters. |
| */ |
| #define MAX_HASH_LEN 128 |
| |
| #define BLACKLIST_KEY_PERM (KEY_POS_SEARCH | KEY_POS_VIEW | \ |
| KEY_USR_SEARCH | KEY_USR_VIEW) |
| |
| static const char tbs_prefix[] = "tbs"; |
| static const char bin_prefix[] = "bin"; |
| |
| 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 i, prefix_len, tbs_step = 0, bin_step = 0; |
| |
| /* The following algorithm only works if prefix lengths match. */ |
| BUILD_BUG_ON(sizeof(tbs_prefix) != sizeof(bin_prefix)); |
| prefix_len = sizeof(tbs_prefix) - 1; |
| for (i = 0; *desc; desc++, i++) { |
| if (*desc == ':') { |
| if (tbs_step == prefix_len) |
| goto found_colon; |
| if (bin_step == prefix_len) |
| goto found_colon; |
| return -EINVAL; |
| } |
| if (i >= prefix_len) |
| return -EINVAL; |
| if (*desc == tbs_prefix[i]) |
| tbs_step++; |
| if (*desc == bin_prefix[i]) |
| bin_step++; |
| } |
| return -EINVAL; |
| |
| found_colon: |
| desc++; |
| for (i = 0; *desc && i < MAX_HASH_LEN; desc++, i++) { |
| if (!isxdigit(*desc) || isupper(*desc)) |
| return -EINVAL; |
| } |
| if (*desc) |
| /* The hash is greater than MAX_HASH_LEN. */ |
| return -ENOPKG; |
| |
| /* Checks for an even number of hexadecimal characters. */ |
| if (i == 0 || i & 1) |
| return -EINVAL; |
| return 0; |
| } |
| |
| static int blacklist_key_instantiate(struct key *key, |
| struct key_preparsed_payload *prep) |
| { |
| #ifdef CONFIG_SYSTEM_BLACKLIST_AUTH_UPDATE |
| int err; |
| #endif |
| |
| /* Sets safe default permissions for keys loaded by user space. */ |
| key->perm = BLACKLIST_KEY_PERM; |
| |
| /* |
| * Skips the authentication step for builtin hashes, they are not |
| * signed but still trusted. |
| */ |
| if (key->flags & (1 << KEY_FLAG_BUILTIN)) |
| goto out; |
| |
| #ifdef CONFIG_SYSTEM_BLACKLIST_AUTH_UPDATE |
| /* |
| * Verifies the description's PKCS#7 signature against the builtin |
| * trusted keyring. |
| */ |
| err = verify_pkcs7_signature(key->description, |
| strlen(key->description), prep->data, prep->datalen, |
| NULL, VERIFYING_UNSPECIFIED_SIGNATURE, NULL, NULL); |
| if (err) |
| return err; |
| #else |
| /* |
| * It should not be possible to come here because the keyring doesn't |
| * have KEY_USR_WRITE and the only other way to call this function is |
| * for builtin hashes. |
| */ |
| WARN_ON_ONCE(1); |
| return -EPERM; |
| #endif |
| |
| out: |
| return generic_key_instantiate(key, prep); |
| } |
| |
| static int blacklist_key_update(struct key *key, |
| struct key_preparsed_payload *prep) |
| { |
| return -EPERM; |
| } |
| |
| 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, |
| .instantiate = blacklist_key_instantiate, |
| .update = blacklist_key_update, |
| .describe = blacklist_describe, |
| }; |
| |
| static char *get_raw_hash(const u8 *hash, size_t hash_len, |
| enum blacklist_hash_type hash_type) |
| { |
| size_t type_len; |
| const char *type_prefix; |
| char *buffer, *p; |
| |
| switch (hash_type) { |
| case BLACKLIST_HASH_X509_TBS: |
| type_len = sizeof(tbs_prefix) - 1; |
| type_prefix = tbs_prefix; |
| break; |
| case BLACKLIST_HASH_BINARY: |
| type_len = sizeof(bin_prefix) - 1; |
| type_prefix = bin_prefix; |
| break; |
| default: |
| WARN_ON_ONCE(1); |
| return ERR_PTR(-EINVAL); |
| } |
| buffer = kmalloc(type_len + 1 + hash_len * 2 + 1, GFP_KERNEL); |
| if (!buffer) |
| return ERR_PTR(-ENOMEM); |
| p = memcpy(buffer, type_prefix, type_len); |
| p += type_len; |
| *p++ = ':'; |
| bin2hex(p, hash, hash_len); |
| p += hash_len * 2; |
| *p = '\0'; |
| return buffer; |
| } |
| |
| /** |
| * mark_raw_hash_blacklisted - Add a hash to the system blacklist |
| * @hash: The hash as a hex string with a type prefix (eg. "tbs:23aa429783") |
| */ |
| static int mark_raw_hash_blacklisted(const char *hash) |
| { |
| key_ref_t key; |
| |
| key = key_create_or_update(make_key_ref(blacklist_keyring, true), |
| "blacklist", |
| hash, |
| NULL, |
| 0, |
| BLACKLIST_KEY_PERM, |
| 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; |
| } |
| |
| int mark_hash_blacklisted(const u8 *hash, size_t hash_len, |
| enum blacklist_hash_type hash_type) |
| { |
| const char *buffer; |
| int err; |
| |
| buffer = get_raw_hash(hash, hash_len, hash_type); |
| if (IS_ERR(buffer)) |
| return PTR_ERR(buffer); |
| err = mark_raw_hash_blacklisted(buffer); |
| kfree(buffer); |
| return err; |
| } |
| |
| /** |
| * 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 |
| * @hash_type: Type of hash |
| */ |
| int is_hash_blacklisted(const u8 *hash, size_t hash_len, |
| enum blacklist_hash_type hash_type) |
| { |
| key_ref_t kref; |
| const char *buffer; |
| int ret = 0; |
| |
| buffer = get_raw_hash(hash, hash_len, hash_type); |
| if (IS_ERR(buffer)) |
| return PTR_ERR(buffer); |
| 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, BLACKLIST_HASH_BINARY) == |
| -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_VIEW | KEY_POS_READ | KEY_POS_SEARCH |
| | KEY_USR_VIEW, |
| KEY_ALLOC_NOT_IN_QUOTA | KEY_ALLOC_BUILT_IN |
| | KEY_ALLOC_BYPASS_RESTRICTION); |
| |
| 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 |
| |
| static int restrict_link_for_blacklist(struct key *dest_keyring, |
| const struct key_type *type, const union key_payload *payload, |
| struct key *restrict_key) |
| { |
| if (type == &key_type_blacklist) |
| return 0; |
| return -EOPNOTSUPP; |
| } |
| |
| /* |
| * Initialise the blacklist |
| * |
| * The blacklist_init() function is registered as an initcall via |
| * device_initcall(). As a result if the blacklist_init() function fails for |
| * any reason the kernel continues to execute. While cleanly returning -ENODEV |
| * could be acceptable for some non-critical kernel parts, if the blacklist |
| * keyring fails to load it defeats the certificate/key based deny list for |
| * signed modules. If a critical piece of security functionality that users |
| * expect to be present fails to initialize, panic()ing is likely the right |
| * thing to do. |
| */ |
| static int __init blacklist_init(void) |
| { |
| const char *const *bl; |
| struct key_restriction *restriction; |
| |
| if (register_key_type(&key_type_blacklist) < 0) |
| panic("Can't allocate system blacklist key type\n"); |
| |
| restriction = kzalloc(sizeof(*restriction), GFP_KERNEL); |
| if (!restriction) |
| panic("Can't allocate blacklist keyring restriction\n"); |
| restriction->check = restrict_link_for_blacklist; |
| |
| blacklist_keyring = |
| keyring_alloc(".blacklist", |
| GLOBAL_ROOT_UID, GLOBAL_ROOT_GID, current_cred(), |
| KEY_POS_VIEW | KEY_POS_READ | KEY_POS_SEARCH | |
| KEY_POS_WRITE | |
| KEY_USR_VIEW | KEY_USR_READ | KEY_USR_SEARCH |
| #ifdef CONFIG_SYSTEM_BLACKLIST_AUTH_UPDATE |
| | KEY_USR_WRITE |
| #endif |
| , KEY_ALLOC_NOT_IN_QUOTA | |
| KEY_ALLOC_SET_KEEP, |
| restriction, NULL); |
| if (IS_ERR(blacklist_keyring)) |
| panic("Can't allocate system blacklist keyring\n"); |
| |
| for (bl = blacklist_hashes; *bl; bl++) |
| if (mark_raw_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 x509_load_certificate_list(revocation_certificate_list, |
| revocation_certificate_list_size, |
| blacklist_keyring); |
| } |
| late_initcall(load_revocation_certificate_list); |
| #endif |