Merge branch 'keys-blacklist' into keys-next

certs/Kconfig

@@ -64,4 +64,22 @@ config SECONDARY_TRUSTED_KEYRING
 	  those keys are not blacklisted and are vouched for by a key built
 	  into the kernel or already in the secondary trusted keyring.
 
+config SYSTEM_BLACKLIST_KEYRING
+	bool "Provide system-wide ring of blacklisted keys"
+	depends on KEYS
+	help
+	  Provide a system keyring to which blacklisted keys can be added.
+	  Keys in the keyring are considered entirely untrusted.  Keys in this
+	  keyring are used by the module signature checking to reject loading
+	  of modules signed with a blacklisted key.
+
+config SYSTEM_BLACKLIST_HASH_LIST
+	string "Hashes to be preloaded into the system blacklist keyring"
+	depends on SYSTEM_BLACKLIST_KEYRING
+	help
+	  If set, this option should be the filename of a list of hashes in the
+	  form "<hash>", "<hash>", ... .  This will be included into a C
+	  wrapper to incorporate the list into the kernel.  Each <hash> should
+	  be a string of hex digits.
+
 endmenu

certs/Makefile

@@ -3,6 +3,12 @@
 #
 
 obj-$(CONFIG_SYSTEM_TRUSTED_KEYRING) += system_keyring.o system_certificates.o
+obj-$(CONFIG_SYSTEM_BLACKLIST_KEYRING) += blacklist.o
+ifneq ($(CONFIG_SYSTEM_BLACKLIST_HASH_LIST),"")
+obj-$(CONFIG_SYSTEM_BLACKLIST_KEYRING) += blacklist_hashes.o
+else
+obj-$(CONFIG_SYSTEM_BLACKLIST_KEYRING) += blacklist_nohashes.o
+endif
 
 ifeq ($(CONFIG_SYSTEM_TRUSTED_KEYRING),y)
 

certs/blacklist.c

+/* 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);

certs/blacklist.h

+#include <linux/kernel.h>
+
+extern const char __initdata *const blacklist_hashes[];

certs/blacklist_hashes.c

+#include "blacklist.h"
+
+const char __initdata *const blacklist_hashes[] = {
+#include CONFIG_SYSTEM_BLACKLIST_HASH_LIST
+	, NULL
+};

certs/blacklist_nohashes.c

+#include "blacklist.h"
+
+const char __initdata *const blacklist_hashes[] = {
+	NULL
+};

crypto/asymmetric_keys/pkcs7_parser.h

@@ -23,6 +23,7 @@ struct pkcs7_signed_info {
 	struct x509_certificate *signer; /* Signing certificate (in msg->certs) */
 	unsigned	index;
 	bool		unsupported_crypto;	/* T if not usable due to missing crypto */
+	bool		blacklisted;
 
 	/* Message digest - the digest of the Content Data (or NULL) */
 	const void	*msgdigest;

crypto/asymmetric_keys/pkcs7_verify.c

@@ -190,6 +190,18 @@ static int pkcs7_verify_sig_chain(struct pkcs7_message *pkcs7,
 			 x509->subject,
 			 x509->raw_serial_size, x509->raw_serial);
 		x509->seen = true;
+
+		if (x509->blacklisted) {
+			/* If this cert is blacklisted, then mark everything
+			 * that depends on this as blacklisted too.
+			 */
+			sinfo->blacklisted = true;
+			for (p = sinfo->signer; p != x509; p = p->signer)
+				p->blacklisted = true;
+			pr_debug("- blacklisted\n");
+			return 0;
+		}
+
 		if (x509->unsupported_key)
 			goto unsupported_crypto_in_x509;
 
@@ -357,17 +369,19 @@ static int pkcs7_verify_one(struct pkcs7_message *pkcs7,
  *
  *  (*) -EBADMSG if some part of the message was invalid, or:
  *
- *  (*) -ENOPKG if none of the signature chains are verifiable because suitable
- *	crypto modules couldn't be found, or:
+ *  (*) 0 if no signature chains were found to be blacklisted or to contain
+ *	unsupported crypto, or:
  *
- *  (*) 0 if all the signature chains that don't incur -ENOPKG can be verified
- *	(note that a signature chain may be of zero length), or:
+ *  (*) -EKEYREJECTED if a blacklisted key was encountered, or:
+ *
+ *  (*) -ENOPKG if none of the signature chains are verifiable because suitable
+ *	crypto modules couldn't be found.
  */
 int pkcs7_verify(struct pkcs7_message *pkcs7,
 		 enum key_being_used_for usage)
 {
 	struct pkcs7_signed_info *sinfo;
-	int enopkg = -ENOPKG;
+	int actual_ret = -ENOPKG;
 	int ret;
 
 	kenter("");
@@ -412,6 +426,8 @@ int pkcs7_verify(struct pkcs7_message *pkcs7,
 
 	for (sinfo = pkcs7->signed_infos; sinfo; sinfo = sinfo->next) {
 		ret = pkcs7_verify_one(pkcs7, sinfo);
+		if (sinfo->blacklisted && actual_ret == -ENOPKG)
+			actual_ret = -EKEYREJECTED;
 		if (ret < 0) {
 			if (ret == -ENOPKG) {
 				sinfo->unsupported_crypto = true;
@@ -420,11 +436,11 @@ int pkcs7_verify(struct pkcs7_message *pkcs7,
 			kleave(" = %d", ret);
 			return ret;
 		}
-		enopkg = 0;
+		actual_ret = 0;
 	}
 
-	kleave(" = %d", enopkg);
-	return enopkg;
+	kleave(" = %d", actual_ret);
+	return actual_ret;
 }
 EXPORT_SYMBOL_GPL(pkcs7_verify);
 

crypto/asymmetric_keys/x509_parser.h

@@ -42,6 +42,7 @@ struct x509_certificate {
 	bool		self_signed;		/* T if self-signed (check unsupported_sig too) */
 	bool		unsupported_key;	/* T if key uses unsupported crypto */
 	bool		unsupported_sig;	/* T if signature uses unsupported crypto */
+	bool		blacklisted;
 };
 
 /*

crypto/asymmetric_keys/x509_public_key.c

@@ -84,6 +84,16 @@ int x509_get_sig_params(struct x509_certificate *cert)
 		goto error_2;
 	might_sleep();
 	ret = crypto_shash_finup(desc, cert->tbs, cert->tbs_size, sig->digest);
+	if (ret < 0)
+		goto error_2;
+
+	ret = is_hash_blacklisted(sig->digest, sig->digest_size, "tbs");
+	if (ret == -EKEYREJECTED) {
+		pr_err("Cert %*phN is blacklisted\n",
+		       sig->digest_size, sig->digest);
+		cert->blacklisted = true;
+		ret = 0;
+	}
 
 error_2:
 	kfree(desc);
@@ -186,6 +196,11 @@ static int x509_key_preparse(struct key_preparsed_payload *prep)
 			 cert->sig->pkey_algo, cert->sig->hash_algo);
 	}
 
+	/* Don't permit addition of blacklisted keys */
+	ret = -EKEYREJECTED;
+	if (cert->blacklisted)
+		goto error_free_cert;
+
 	/* Propose a description */
 	sulen = strlen(cert->subject);
 	if (cert->raw_skid) {

include/keys/system_keyring.h

@@ -33,6 +33,18 @@ extern int restrict_link_by_builtin_and_secondary_trusted(
 #define restrict_link_by_builtin_and_secondary_trusted restrict_link_by_builtin_trusted
 #endif
 
+#ifdef CONFIG_SYSTEM_BLACKLIST_KEYRING
+extern int mark_hash_blacklisted(const char *hash);
+extern int is_hash_blacklisted(const u8 *hash, size_t hash_len,
+			       const char *type);
+#else
+static inline int is_hash_blacklisted(const u8 *hash, size_t hash_len,
+				      const char *type)
+{
+	return 0;
+}
+#endif
+
 #ifdef CONFIG_IMA_BLACKLIST_KEYRING
 extern struct key *ima_blacklist_keyring;