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From:   David Howells <dhowells@redhat.com>
In-Reply-To: <E090372C-06A3-4991-8FC3-F06A0DA60729@oracle.com>
References: <E090372C-06A3-4991-8FC3-F06A0DA60729@oracle.com> <20200916004927.64276-1-eric.snowberg@oracle.com> <1360578.1607593748@warthog.procyon.org.uk>
To:     Eric Snowberg <eric.snowberg@oracle.com>
Cc:     dhowells@redhat.com, dwmw2@infradead.org,
        Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>,
        herbert@gondor.apana.org.au, davem@davemloft.net,
        jmorris@namei.org, serge@hallyn.com, nayna@linux.ibm.com,
        Mimi Zohar <zohar@linux.ibm.com>, erichte@linux.ibm.com,
        mpe@ellerman.id.au, keyrings@vger.kernel.org,
        linux-kernel@vger.kernel.org, linux-crypto@vger.kernel.org,
        linux-security-module@vger.kernel.org
Subject: Re: [PATCH v4] certs: Add EFI_CERT_X509_GUID support for dbx entries
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Date:   Tue, 12 Jan 2021 17:10:00 +0000
Message-ID: <2560432.1610471400@warthog.procyon.org.uk>
Precedence: bulk

How about the attached?  I've changed the function names to something that=
 I
think reads better, but otherwise it's the same.

David
---
commit 8913866babb96fcfe452aac6042ca8862d4c0b53
Author: Eric Snowberg <eric.snowberg@oracle.com>
Date:   Tue Sep 15 20:49:27 2020 -0400

    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 Secu=
re
    Boot enabled.  The dbx is capable of containing any number of
    EFI_CERT_X509_SHA256_GUID, EFI_CERT_SHA256_GUID, and EFI_CERT_X509_GUI=
D
    entries.
    =

    Currently when EFI_CERT_X509_GUID are contained in the dbx, the entrie=
s are
    skipped.
    =

    Add support for EFI_CERT_X509_GUID dbx entries. When a EFI_CERT_X509_G=
UID
    is found, it is added as an asymmetrical key to the .blacklist keyring=
.
    Anytime the .platform keyring is used, the keys in the .blacklist keyr=
ing
    are referenced, if a matching key is found, the key will be rejected.
    =

    Signed-off-by: Eric Snowberg <eric.snowberg@oracle.com>
    Reviewed-by: Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>
    Signed-off-by: David Howells <dhowells@redhat.com>

diff --git a/certs/blacklist.c b/certs/blacklist.c
index 6514f9ebc943..a7f021878a4b 100644
--- a/certs/blacklist.c
+++ b/certs/blacklist.c
@@ -100,6 +100,38 @@ int mark_hash_blacklisted(const char *hash)
 	return 0;
 }
 =

+int add_key_to_revocation_list(const char *data, size_t size)
+{
+	key_ref_t key;
+
+	key =3D 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_on_revocation_list(struct pkcs7_message *pkcs7)
+{
+	int ret;
+
+	ret =3D validate_trust(pkcs7, blacklist_keyring);
+
+	if (ret =3D=3D 0)
+		return -EKEYREJECTED;
+
+	return -ENOKEY;
+}
+
 /**
  * is_hash_blacklisted - Determine if a hash is blacklisted
  * @hash: The hash to be checked as a binary blob
diff --git a/certs/blacklist.h b/certs/blacklist.h
index 1efd6fa0dc60..420bb7c86e07 100644
--- a/certs/blacklist.h
+++ b/certs/blacklist.h
@@ -1,3 +1,15 @@
 #include <linux/kernel.h>
+#include <linux/errno.h>
+#include <crypto/pkcs7.h>
 =

 extern const char __initconst *const blacklist_hashes[];
+
+#ifdef CONFIG_INTEGRITY_PLATFORM_KEYRING
+#define validate_trust pkcs7_validate_trust
+#else
+static inline int validate_trust(struct pkcs7_message *pkcs7,
+				 struct key *trust_keyring)
+{
+	return -ENOKEY;
+}
+#endif
diff --git a/certs/system_keyring.c b/certs/system_keyring.c
index 798291177186..cc165b359ea3 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 =3D is_key_on_revocation_list(pkcs7);
+		if (ret !=3D -ENOKEY) {
+			pr_devel("PKCS#7 platform key is on revocation list\n");
+			goto error;
+		}
 	}
 	ret =3D 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..61f98739e8b1 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_trus=
ted(
 #define restrict_link_by_builtin_and_secondary_trusted restrict_link_by_b=
uiltin_trusted
 #endif
 =

+extern struct pkcs7_message *pkcs7;
 #ifdef CONFIG_SYSTEM_BLACKLIST_KEYRING
 extern int mark_hash_blacklisted(const char *hash);
+extern int add_key_to_revocation_list(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_on_revocation_list(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 add_key_to_revocation_list(const char *data, size_t siz=
e)
+{
+	return 0;
+}
+static inline int is_key_on_revocation_list(struct pkcs7_message *pkcs7)
+{
+	return -ENOKEY;
+}
 #endif
 =

 #ifdef CONFIG_IMA_BLACKLIST_KEYRING
diff --git a/security/integrity/platform_certs/keyring_handler.c b/securit=
y/integrity/platform_certs/keyring_handler.c
index c5ba695c10e3..5604bd57c990 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 *so=
urce,
 	uefi_blacklist_hash(source, data, len, "bin:", 4);
 }
 =

+/*
+ * Add an X509 cert to the revocation list.
+ */
+static __init void uefi_revocation_list_x509(const char *source,
+					     const void *data, size_t len)
+{
+	add_key_to_revocation_list(data, len);
+}
+
 /*
  * Return the appropriate handler for particular signature list types fou=
nd in
  * the UEFI db and MokListRT tables.
@@ -76,5 +85,7 @@ __init efi_element_handler_t get_handler_for_dbx(const e=
fi_guid_t *sig_type)
 		return uefi_blacklist_x509_tbs;
 	if (efi_guidcmp(*sig_type, efi_cert_sha256_guid) =3D=3D 0)
 		return uefi_blacklist_binary;
+	if (efi_guidcmp(*sig_type, efi_cert_x509_guid) =3D=3D 0)
+		return uefi_revocation_list_x509;
 	return 0;
 }