linux/certs/blacklist.c

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// 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"
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#include "common.h"
static struct key *blacklist_keyring;
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#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);
certs: Add EFI_CERT_X509_GUID support for dbx entries This fixes CVE-2020-26541. The Secure Boot Forbidden Signature Database, dbx, contains a list of now revoked signatures and keys previously approved to boot with UEFI Secure Boot enabled. The dbx is capable of containing any number of EFI_CERT_X509_SHA256_GUID, EFI_CERT_SHA256_GUID, and EFI_CERT_X509_GUID entries. Currently when EFI_CERT_X509_GUID are contained in the dbx, the entries are skipped. Add support for EFI_CERT_X509_GUID dbx entries. When a EFI_CERT_X509_GUID is found, it is added as an asymmetrical key to the .blacklist keyring. Anytime the .platform keyring is used, the keys in the .blacklist keyring are referenced, if a matching key is found, the key will be rejected. [DH: Made the following changes: - Added to have a config option to enable the facility. This allows a Kconfig solution to make sure that pkcs7_validate_trust() is enabled.[1][2] - Moved the functions out from the middle of the blacklist functions. - Added kerneldoc comments.] Signed-off-by: Eric Snowberg <eric.snowberg@oracle.com> Signed-off-by: David Howells <dhowells@redhat.com> Reviewed-by: Jarkko Sakkinen <jarkko@kernel.org> cc: Randy Dunlap <rdunlap@infradead.org> cc: Mickaël Salaün <mic@digikod.net> cc: Arnd Bergmann <arnd@kernel.org> cc: keyrings@vger.kernel.org Link: https://lore.kernel.org/r/20200901165143.10295-1-eric.snowberg@oracle.com/ # rfc Link: https://lore.kernel.org/r/20200909172736.73003-1-eric.snowberg@oracle.com/ # v2 Link: https://lore.kernel.org/r/20200911182230.62266-1-eric.snowberg@oracle.com/ # v3 Link: https://lore.kernel.org/r/20200916004927.64276-1-eric.snowberg@oracle.com/ # v4 Link: https://lore.kernel.org/r/20210122181054.32635-2-eric.snowberg@oracle.com/ # v5 Link: https://lore.kernel.org/r/161428672051.677100.11064981943343605138.stgit@warthog.procyon.org.uk/ Link: https://lore.kernel.org/r/161433310942.902181.4901864302675874242.stgit@warthog.procyon.org.uk/ # v2 Link: https://lore.kernel.org/r/161529605075.163428.14625520893961300757.stgit@warthog.procyon.org.uk/ # v3 Link: https://lore.kernel.org/r/bc2c24e3-ed68-2521-0bf4-a1f6be4a895d@infradead.org/ [1] Link: https://lore.kernel.org/r/20210225125638.1841436-1-arnd@kernel.org/ [2]
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#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);
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#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