KEYS: Add a system blacklist keyring

[mirror_ubuntu-bionic-kernel.git] / certs / blacklist.c

diff --git a/certs/blacklist.c b/certs/blacklist.c
new file mode 100644 (file)
index 0000000..3eddce0
--- /dev/null
+++ b/certs/blacklist.c
@@ -0,0 +1,174 @@
+/* System hash blacklist.
+ *
+ * Copyright (C) 2016 Red Hat, Inc. All Rights Reserved.
+ * Written by David Howells (dhowells@redhat.com)
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public Licence
+ * as published by the Free Software Foundation; either version
+ * 2 of the Licence, or (at your option) any later version.
+ */
+
+#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 <keys/system_keyring.h>
+#include "blacklist.h"
+
+static struct key *blacklist_keyring;
+
+/*
+ * 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))
+                       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);
+       if (!IS_ERR(kref)) {
+               key_ref_put(kref);
+               ret = -EKEYREJECTED;
+       }
+
+       kfree(buffer);
+       return ret;
+}
+EXPORT_SYMBOL_GPL(is_hash_blacklisted);
+
+/*
+ * Intialise 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",
+                             KUIDT_INIT(0), KGIDT_INIT(0),
+                             current_cred(),
+                             (KEY_POS_ALL & ~KEY_POS_SETATTR) |
+                             KEY_USR_VIEW | KEY_USR_READ |
+                             KEY_USR_SEARCH,
+                             KEY_ALLOC_NOT_IN_QUOTA |
+                             KEY_FLAG_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);