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372 lines
9.4 KiB
372 lines
9.4 KiB
// SPDX-License-Identifier: GPL-2.0-or-later |
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/* System hash blacklist. |
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* |
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* Copyright (C) 2016 Red Hat, Inc. All Rights Reserved. |
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* Written by David Howells ([email protected]) |
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*/ |
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|
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#define pr_fmt(fmt) "blacklist: "fmt |
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#include <linux/module.h> |
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#include <linux/slab.h> |
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#include <linux/key.h> |
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#include <linux/key-type.h> |
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#include <linux/sched.h> |
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#include <linux/ctype.h> |
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#include <linux/err.h> |
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#include <linux/seq_file.h> |
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#include <linux/uidgid.h> |
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#include <keys/asymmetric-type.h> |
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#include <keys/system_keyring.h> |
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#include "blacklist.h" |
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|
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/* |
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* According to crypto/asymmetric_keys/x509_cert_parser.c:x509_note_pkey_algo(), |
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* the size of the currently longest supported hash algorithm is 512 bits, |
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* which translates into 128 hex characters. |
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*/ |
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#define MAX_HASH_LEN 128 |
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#define BLACKLIST_KEY_PERM (KEY_POS_SEARCH | KEY_POS_VIEW | \ |
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KEY_USR_SEARCH | KEY_USR_VIEW) |
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static const char tbs_prefix[] = "tbs"; |
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static const char bin_prefix[] = "bin"; |
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static struct key *blacklist_keyring; |
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#ifdef CONFIG_SYSTEM_REVOCATION_LIST |
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extern __initconst const u8 revocation_certificate_list[]; |
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extern __initconst const unsigned long revocation_certificate_list_size; |
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#endif |
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/* |
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* The description must be a type prefix, a colon and then an even number of |
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* hex digits. The hash is kept in the description. |
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*/ |
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static int blacklist_vet_description(const char *desc) |
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{ |
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int i, prefix_len, tbs_step = 0, bin_step = 0; |
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|
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/* The following algorithm only works if prefix lengths match. */ |
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BUILD_BUG_ON(sizeof(tbs_prefix) != sizeof(bin_prefix)); |
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prefix_len = sizeof(tbs_prefix) - 1; |
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for (i = 0; *desc; desc++, i++) { |
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if (*desc == ':') { |
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if (tbs_step == prefix_len) |
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goto found_colon; |
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if (bin_step == prefix_len) |
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goto found_colon; |
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return -EINVAL; |
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} |
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if (i >= prefix_len) |
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return -EINVAL; |
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if (*desc == tbs_prefix[i]) |
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tbs_step++; |
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if (*desc == bin_prefix[i]) |
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bin_step++; |
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} |
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return -EINVAL; |
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found_colon: |
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desc++; |
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for (i = 0; *desc && i < MAX_HASH_LEN; desc++, i++) { |
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if (!isxdigit(*desc) || isupper(*desc)) |
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return -EINVAL; |
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} |
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if (*desc) |
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/* The hash is greater than MAX_HASH_LEN. */ |
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return -ENOPKG; |
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/* Checks for an even number of hexadecimal characters. */ |
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if (i == 0 || i & 1) |
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return -EINVAL; |
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return 0; |
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} |
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static int blacklist_key_instantiate(struct key *key, |
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struct key_preparsed_payload *prep) |
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{ |
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#ifdef CONFIG_SYSTEM_BLACKLIST_AUTH_UPDATE |
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int err; |
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#endif |
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|
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/* Sets safe default permissions for keys loaded by user space. */ |
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key->perm = BLACKLIST_KEY_PERM; |
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/* |
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* Skips the authentication step for builtin hashes, they are not |
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* signed but still trusted. |
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*/ |
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if (key->flags & (1 << KEY_FLAG_BUILTIN)) |
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goto out; |
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#ifdef CONFIG_SYSTEM_BLACKLIST_AUTH_UPDATE |
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/* |
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* Verifies the description's PKCS#7 signature against the builtin |
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* trusted keyring. |
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*/ |
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err = verify_pkcs7_signature(key->description, |
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strlen(key->description), prep->data, prep->datalen, |
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NULL, VERIFYING_UNSPECIFIED_SIGNATURE, NULL, NULL); |
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if (err) |
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return err; |
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#else |
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/* |
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* It should not be possible to come here because the keyring doesn't |
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* have KEY_USR_WRITE and the only other way to call this function is |
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* for builtin hashes. |
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*/ |
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WARN_ON_ONCE(1); |
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return -EPERM; |
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#endif |
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out: |
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return generic_key_instantiate(key, prep); |
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} |
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static int blacklist_key_update(struct key *key, |
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struct key_preparsed_payload *prep) |
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{ |
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return -EPERM; |
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} |
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static void blacklist_describe(const struct key *key, struct seq_file *m) |
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{ |
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seq_puts(m, key->description); |
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} |
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static struct key_type key_type_blacklist = { |
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.name = "blacklist", |
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.vet_description = blacklist_vet_description, |
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.instantiate = blacklist_key_instantiate, |
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.update = blacklist_key_update, |
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.describe = blacklist_describe, |
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}; |
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static char *get_raw_hash(const u8 *hash, size_t hash_len, |
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enum blacklist_hash_type hash_type) |
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{ |
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size_t type_len; |
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const char *type_prefix; |
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char *buffer, *p; |
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switch (hash_type) { |
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case BLACKLIST_HASH_X509_TBS: |
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type_len = sizeof(tbs_prefix) - 1; |
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type_prefix = tbs_prefix; |
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break; |
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case BLACKLIST_HASH_BINARY: |
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type_len = sizeof(bin_prefix) - 1; |
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type_prefix = bin_prefix; |
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break; |
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default: |
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WARN_ON_ONCE(1); |
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return ERR_PTR(-EINVAL); |
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} |
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buffer = kmalloc(type_len + 1 + hash_len * 2 + 1, GFP_KERNEL); |
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if (!buffer) |
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return ERR_PTR(-ENOMEM); |
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p = memcpy(buffer, type_prefix, type_len); |
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p += type_len; |
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*p++ = ':'; |
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bin2hex(p, hash, hash_len); |
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p += hash_len * 2; |
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*p = '\0'; |
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return buffer; |
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} |
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/** |
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* mark_raw_hash_blacklisted - Add a hash to the system blacklist |
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* @hash: The hash as a hex string with a type prefix (eg. "tbs:23aa429783") |
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*/ |
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static int mark_raw_hash_blacklisted(const char *hash) |
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{ |
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key_ref_t key; |
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key = key_create_or_update(make_key_ref(blacklist_keyring, true), |
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"blacklist", |
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hash, |
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NULL, |
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0, |
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BLACKLIST_KEY_PERM, |
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KEY_ALLOC_NOT_IN_QUOTA | |
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KEY_ALLOC_BUILT_IN); |
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if (IS_ERR(key)) { |
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pr_err("Problem blacklisting hash (%ld)\n", PTR_ERR(key)); |
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return PTR_ERR(key); |
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} |
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return 0; |
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} |
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int mark_hash_blacklisted(const u8 *hash, size_t hash_len, |
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enum blacklist_hash_type hash_type) |
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{ |
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const char *buffer; |
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int err; |
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buffer = get_raw_hash(hash, hash_len, hash_type); |
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if (IS_ERR(buffer)) |
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return PTR_ERR(buffer); |
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err = mark_raw_hash_blacklisted(buffer); |
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kfree(buffer); |
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return err; |
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} |
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/** |
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* is_hash_blacklisted - Determine if a hash is blacklisted |
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* @hash: The hash to be checked as a binary blob |
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* @hash_len: The length of the binary hash |
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* @hash_type: Type of hash |
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*/ |
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int is_hash_blacklisted(const u8 *hash, size_t hash_len, |
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enum blacklist_hash_type hash_type) |
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{ |
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key_ref_t kref; |
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const char *buffer; |
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int ret = 0; |
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buffer = get_raw_hash(hash, hash_len, hash_type); |
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if (IS_ERR(buffer)) |
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return PTR_ERR(buffer); |
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kref = keyring_search(make_key_ref(blacklist_keyring, true), |
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&key_type_blacklist, buffer, false); |
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if (!IS_ERR(kref)) { |
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key_ref_put(kref); |
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ret = -EKEYREJECTED; |
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} |
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kfree(buffer); |
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return ret; |
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} |
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EXPORT_SYMBOL_GPL(is_hash_blacklisted); |
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int is_binary_blacklisted(const u8 *hash, size_t hash_len) |
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{ |
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if (is_hash_blacklisted(hash, hash_len, BLACKLIST_HASH_BINARY) == |
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-EKEYREJECTED) |
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return -EPERM; |
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return 0; |
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} |
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EXPORT_SYMBOL_GPL(is_binary_blacklisted); |
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#ifdef CONFIG_SYSTEM_REVOCATION_LIST |
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/** |
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* add_key_to_revocation_list - Add a revocation certificate to the blacklist |
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* @data: The data blob containing the certificate |
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* @size: The size of data blob |
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*/ |
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int add_key_to_revocation_list(const char *data, size_t size) |
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{ |
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key_ref_t key; |
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key = key_create_or_update(make_key_ref(blacklist_keyring, true), |
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"asymmetric", |
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NULL, |
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data, |
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size, |
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KEY_POS_VIEW | KEY_POS_READ | KEY_POS_SEARCH |
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| KEY_USR_VIEW, |
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KEY_ALLOC_NOT_IN_QUOTA | KEY_ALLOC_BUILT_IN |
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| KEY_ALLOC_BYPASS_RESTRICTION); |
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if (IS_ERR(key)) { |
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pr_err("Problem with revocation key (%ld)\n", PTR_ERR(key)); |
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return PTR_ERR(key); |
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} |
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return 0; |
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} |
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/** |
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* is_key_on_revocation_list - Determine if the key for a PKCS#7 message is revoked |
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* @pkcs7: The PKCS#7 message to check |
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*/ |
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int is_key_on_revocation_list(struct pkcs7_message *pkcs7) |
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{ |
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int ret; |
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ret = pkcs7_validate_trust(pkcs7, blacklist_keyring); |
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if (ret == 0) |
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return -EKEYREJECTED; |
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return -ENOKEY; |
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} |
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#endif |
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static int restrict_link_for_blacklist(struct key *dest_keyring, |
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const struct key_type *type, const union key_payload *payload, |
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struct key *restrict_key) |
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{ |
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if (type == &key_type_blacklist) |
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return 0; |
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return -EOPNOTSUPP; |
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} |
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/* |
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* Initialise the blacklist |
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* |
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* The blacklist_init() function is registered as an initcall via |
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* device_initcall(). As a result if the blacklist_init() function fails for |
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* any reason the kernel continues to execute. While cleanly returning -ENODEV |
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* could be acceptable for some non-critical kernel parts, if the blacklist |
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* keyring fails to load it defeats the certificate/key based deny list for |
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* signed modules. If a critical piece of security functionality that users |
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* expect to be present fails to initialize, panic()ing is likely the right |
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* thing to do. |
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*/ |
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static int __init blacklist_init(void) |
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{ |
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const char *const *bl; |
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struct key_restriction *restriction; |
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if (register_key_type(&key_type_blacklist) < 0) |
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panic("Can't allocate system blacklist key type\n"); |
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restriction = kzalloc(sizeof(*restriction), GFP_KERNEL); |
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if (!restriction) |
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panic("Can't allocate blacklist keyring restriction\n"); |
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restriction->check = restrict_link_for_blacklist; |
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blacklist_keyring = |
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keyring_alloc(".blacklist", |
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GLOBAL_ROOT_UID, GLOBAL_ROOT_GID, current_cred(), |
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KEY_POS_VIEW | KEY_POS_READ | KEY_POS_SEARCH | |
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KEY_POS_WRITE | |
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KEY_USR_VIEW | KEY_USR_READ | KEY_USR_SEARCH |
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#ifdef CONFIG_SYSTEM_BLACKLIST_AUTH_UPDATE |
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| KEY_USR_WRITE |
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#endif |
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, KEY_ALLOC_NOT_IN_QUOTA | |
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KEY_ALLOC_SET_KEEP, |
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restriction, NULL); |
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if (IS_ERR(blacklist_keyring)) |
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panic("Can't allocate system blacklist keyring\n"); |
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for (bl = blacklist_hashes; *bl; bl++) |
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if (mark_raw_hash_blacklisted(*bl) < 0) |
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pr_err("- blacklisting failed\n"); |
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return 0; |
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} |
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/* |
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* Must be initialised before we try and load the keys into the keyring. |
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*/ |
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device_initcall(blacklist_init); |
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#ifdef CONFIG_SYSTEM_REVOCATION_LIST |
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/* |
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* Load the compiled-in list of revocation X.509 certificates. |
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*/ |
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static __init int load_revocation_certificate_list(void) |
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{ |
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if (revocation_certificate_list_size) |
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pr_notice("Loading compiled-in revocation X.509 certificates\n"); |
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return x509_load_certificate_list(revocation_certificate_list, |
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revocation_certificate_list_size, |
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blacklist_keyring); |
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} |
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late_initcall(load_revocation_certificate_list); |
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#endif
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