1 files changed, 372 insertions, 0 deletions
diff --git a/certs/blacklist.c b/certs/blacklist.c
new file mode 100644
index 000000000..41f10601c
--- /dev/null
+++ b/certs/blacklist.c
@@ -0,0 +1,372 @@
+// 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