From 096da19de900a115ee3610b666ecb7e55926623d Mon Sep 17 00:00:00 2001
From: Josh Boyer <jwboyer@fedoraproject.org>
Date: Fri, 26 Oct 2012 12:36:24 -0400
Subject: [PATCH 6/9] KEYS: Add a system blacklist keyring

This adds an additional keyring that is used to store certificates that
are blacklisted.  This keyring is searched first when loading signed modules
and if the module's certificate is found, it will refuse to load.  This is
useful in cases where third party certificates are used for module signing.

Signed-off-by: Josh Boyer <jwboyer@fedoraproject.org>
---
 certs/system_keyring.c        | 22 ++++++++++++++++++++++
 include/keys/system_keyring.h |  4 ++++
 init/Kconfig                  |  9 +++++++++
 3 files changed, 35 insertions(+)

diff --git a/certs/system_keyring.c b/certs/system_keyring.c
index 50979d6dcecd..787eeead2f57 100644
--- a/certs/system_keyring.c
+++ b/certs/system_keyring.c
@@ -22,6 +22,9 @@ static struct key *builtin_trusted_keys;
 #ifdef CONFIG_SECONDARY_TRUSTED_KEYRING
 static struct key *secondary_trusted_keys;
 #endif
+#ifdef CONFIG_SYSTEM_BLACKLIST_KEYRING
+struct key *system_blacklist_keyring;
+#endif
 
 extern __initconst const u8 system_certificate_list[];
 extern __initconst const unsigned long system_certificate_list_size;
@@ -99,6 +102,16 @@ static __init int system_trusted_keyring_init(void)
 	if (key_link(secondary_trusted_keys, builtin_trusted_keys) < 0)
 		panic("Can't link trusted keyrings\n");
 #endif
+#ifdef CONFIG_SYSTEM_BLACKLIST_KEYRING
+	system_blacklist_keyring = keyring_alloc(".system_blacklist_keyring",
+			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,
+			NULL, NULL);
+	if (IS_ERR(system_blacklist_keyring))
+		panic("Can't allocate system blacklist keyring\n");
+#endif
 
 	return 0;
 }
@@ -214,6 +227,15 @@ int verify_pkcs7_signature(const void *data, size_t len,
 		trusted_keys = builtin_trusted_keys;
 #endif
 	}
+#ifdef CONFIG_SYSTEM_BLACKLIST_KEYRING
+	ret = pkcs7_validate_trust(pkcs7, system_blacklist_keyring);
+	if (!ret) {
+		/* module is signed with a cert in the blacklist.  reject */
+		pr_err("Module key is in the blacklist\n");
+		ret = -EKEYREJECTED;
+		goto error;
+	}
+#endif
 	ret = pkcs7_validate_trust(pkcs7, trusted_keys);
 	if (ret < 0) {
 		if (ret == -ENOKEY)
diff --git a/include/keys/system_keyring.h b/include/keys/system_keyring.h
index fbd4647767e9..5bc291a3d261 100644
--- a/include/keys/system_keyring.h
+++ b/include/keys/system_keyring.h
@@ -33,6 +33,10 @@ 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 struct key *system_blacklist_keyring;
+#endif
+
 #ifdef CONFIG_IMA_BLACKLIST_KEYRING
 extern struct key *ima_blacklist_keyring;
 
diff --git a/init/Kconfig b/init/Kconfig
index a9c4aefd5436..e5449d5aeff9 100644
--- a/init/Kconfig
+++ b/init/Kconfig
@@ -1829,6 +1829,15 @@ config SYSTEM_DATA_VERIFICATION
 	  module verification, kexec image verification and firmware blob
 	  verification.
 
+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 PROFILING
 	bool "Profiling support"
 	help
-- 
2.5.5