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![David Howells](/assets/img/avatar_default.png)
Move load_certificate_list(), which loads a series of binary X.509 certificates from a blob and inserts them as keys into a keyring, to be with the asymmetric keys code that it drives. This makes it easier to add FIPS selftest code in which we need to load up a private keyring for the tests to use. Signed-off-by: David Howells <dhowells@redhat.com> Reviewed-by: Simo Sorce <simo@redhat.com> Reviewed-by: Herbert Xu <herbert@gondor.apana.org.au> cc: keyrings@vger.kernel.org cc: linux-crypto@vger.kernel.org Link: https://lore.kernel.org/r/165515742145.1554877.13488098107542537203.stgit@warthog.procyon.org.uk/
372 lines
9.4 KiB
C
372 lines
9.4 KiB
C
// 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 (dhowells@redhat.com)
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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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* 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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/* 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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/* 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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