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Message-Id: <20200901165143.10295-1-eric.snowberg@oracle.com>
Date: Tue, 1 Sep 2020 12:51:43 -0400
From: Eric Snowberg <eric.snowberg@...cle.com>
To: dhowells@...hat.com, dwmw2@...radead.org
Cc: jarkko.sakkinen@...ux.intel.com, jmorris@...ei.org,
serge@...lyn.com, zohar@...ux.ibm.com, erichte@...ux.ibm.com,
nayna@...ux.ibm.com, mpe@...erman.id.au, keyrings@...r.kernel.org,
linux-kernel@...r.kernel.org,
linux-security-module@...r.kernel.org, eric.snowberg@...cle.com
Subject: [RFC PATCH] certs: Add EFI_CERT_X509_GUID support for dbx entries
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.
This change adds 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.
Signed-off-by: Eric Snowberg <eric.snowberg@...cle.com>
---
certs/blacklist.c | 36 +++++++++++++++++++
certs/system_keyring.c | 6 ++++
include/keys/system_keyring.h | 11 ++++++
.../platform_certs/keyring_handler.c | 11 ++++++
4 files changed, 64 insertions(+)
diff --git a/certs/blacklist.c b/certs/blacklist.c
index 6514f9ebc943..17ebf50cf0ae 100644
--- a/certs/blacklist.c
+++ b/certs/blacklist.c
@@ -15,6 +15,7 @@
#include <linux/err.h>
#include <linux/seq_file.h>
#include <keys/system_keyring.h>
+#include <crypto/pkcs7.h>
#include "blacklist.h"
static struct key *blacklist_keyring;
@@ -100,6 +101,41 @@ int mark_hash_blacklisted(const char *hash)
return 0;
}
+int mark_key_revocationlisted(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;
+}
+
+int is_key_revocationlisted(struct pkcs7_message *pkcs7)
+{
+ int ret;
+
+ ret = pkcs7_validate_trust(pkcs7, blacklist_keyring);
+
+ if (ret == 0)
+ return -EKEYREJECTED;
+
+ return -ENOKEY;
+}
+EXPORT_SYMBOL_GPL(is_key_revocationlisted);
+
/**
* is_hash_blacklisted - Determine if a hash is blacklisted
* @hash: The hash to be checked as a binary blob
diff --git a/certs/system_keyring.c b/certs/system_keyring.c
index 798291177186..f8ea96219155 100644
--- a/certs/system_keyring.c
+++ b/certs/system_keyring.c
@@ -241,6 +241,12 @@ int verify_pkcs7_message_sig(const void *data, size_t len,
pr_devel("PKCS#7 platform keyring is not available\n");
goto error;
}
+
+ ret = is_key_revocationlisted(pkcs7);
+ if (ret != -ENOKEY) {
+ pr_devel("PKCS#7 platform key revocationlisted\n");
+ goto error;
+ }
}
ret = pkcs7_validate_trust(pkcs7, trusted_keys);
if (ret < 0) {
diff --git a/include/keys/system_keyring.h b/include/keys/system_keyring.h
index fb8b07daa9d1..b6991cfe1b6d 100644
--- a/include/keys/system_keyring.h
+++ b/include/keys/system_keyring.h
@@ -31,11 +31,14 @@ extern int restrict_link_by_builtin_and_secondary_trusted(
#define restrict_link_by_builtin_and_secondary_trusted restrict_link_by_builtin_trusted
#endif
+extern struct pkcs7_message *pkcs7;
#ifdef CONFIG_SYSTEM_BLACKLIST_KEYRING
extern int mark_hash_blacklisted(const char *hash);
+extern int mark_key_revocationlisted(const char *data, size_t size);
extern int is_hash_blacklisted(const u8 *hash, size_t hash_len,
const char *type);
extern int is_binary_blacklisted(const u8 *hash, size_t hash_len);
+extern int is_key_revocationlisted(struct pkcs7_message *pkcs7);
#else
static inline int is_hash_blacklisted(const u8 *hash, size_t hash_len,
const char *type)
@@ -47,6 +50,14 @@ static inline int is_binary_blacklisted(const u8 *hash, size_t hash_len)
{
return 0;
}
+static inline int mark_key_revocationlisted(const char *data, size_t size)
+{
+ return 0;
+}
+static inline int is_key_revocationlisted(struct pkcs7_message *pkcs7)
+{
+ return -ENOKEY;
+}
#endif
#ifdef CONFIG_IMA_BLACKLIST_KEYRING
diff --git a/security/integrity/platform_certs/keyring_handler.c b/security/integrity/platform_certs/keyring_handler.c
index c5ba695c10e3..cc5a43804bc4 100644
--- a/security/integrity/platform_certs/keyring_handler.c
+++ b/security/integrity/platform_certs/keyring_handler.c
@@ -55,6 +55,15 @@ static __init void uefi_blacklist_binary(const char *source,
uefi_blacklist_hash(source, data, len, "bin:", 4);
}
+/*
+ * Revocationlist the X509 cert
+ */
+static __init void uefi_revocationlist_x509(const char *source,
+ const void *data, size_t len)
+{
+ mark_key_revocationlisted(data, len);
+}
+
/*
* Return the appropriate handler for particular signature list types found in
* the UEFI db and MokListRT tables.
@@ -76,5 +85,7 @@ __init efi_element_handler_t get_handler_for_dbx(const efi_guid_t *sig_type)
return uefi_blacklist_x509_tbs;
if (efi_guidcmp(*sig_type, efi_cert_sha256_guid) == 0)
return uefi_blacklist_binary;
+ if (efi_guidcmp(*sig_type, efi_cert_x509_guid) == 0)
+ return uefi_revocationlist_x509;
return 0;
}
--
2.18.1
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