Add patches to enable loading dbx and MOKX blacklists

Import patches from: https://lore.kernel.org/patchwork/cover/933178/ that allow to also load dbx and MOKX as blacklists for modules. These patches also disable loading MOK/MOKX when secure boot is not enabled, as the variables will not be safe, and to check the variables attributes before accepting them.
2019-05-02 23:03:39 +01:00 · 2019-05-02 23:03:39 +01:00 · 643cc8a41c
parent 188df85f5b
commit 643cc8a41c
6 changed files with 347 additions and 1 deletions
--- a/debian/changelog
+++ b/debian/changelog
@ -1105,7 +1105,8 @@ linux (4.19.37-1) UNRELEASED; urgency=medium
    libbpf-generate-pkg-config.patch from bpf-next.
  * Import patches to enable loading keys from UEFI db and MOK from
    http://git.kernel.org/cgit/linux/kernel/git/dhowells/linux-fs.git to
-    allow kernel modules built by users (eg: by dkms) to be verified.
+    allow kernel modules built by users (eg: by dkms) to be verified, and
+    to load dbx and MOKX for the equivalent blacklisting functionality.

  [ Bastian Blank ]
  * Don't longer recommend irqbalance. (closes: #926967)
--- a/debian/patches/features/all/db-mok-keyring/0001-MODSIGN-do-not-load-mok-when-secure-boot-disabled.patch
+++ b/debian/patches/features/all/db-mok-keyring/0001-MODSIGN-do-not-load-mok-when-secure-boot-disabled.patch
@ -0,0 +1,59 @@
+Origin: https://lore.kernel.org/patchwork/cover/933178/
+From: "Lee, Chun-Yi" <joeyli.kernel@gmail.com>
+Subject: [PATCH 1/5] MODSIGN: do not load mok when secure boot disabled
+
+The mok can not be trusted when the secure boot is disabled. Which
+means that the kernel embedded certificate is the only trusted key.
+
+Due to db/dbx are authenticated variables, they needs manufacturer's
+KEK for update. So db/dbx are secure when secureboot disabled.
+
+Signed-off-by: "Lee, Chun-Yi" <jlee@suse.com>
+---
+ certs/load_uefi.c | 26 +++++++++++++++-----------
+ 1 file changed, 15 insertions(+), 11 deletions(-)
+
+diff --git a/certs/load_uefi.c b/certs/load_uefi.c
+index 3d88459..d6de4d0 100644
+--- a/certs/load_uefi.c
+++ b/certs/load_uefi.c
+@@ -171,17 +171,6 @@
+ 		}
+ 	}
+ 
+-	rc = get_cert_list(L"MokListRT", &mok_var, &moksize, &mok);
+-	if (rc < 0) {
+-		pr_info("MODSIGN: Couldn't get UEFI MokListRT\n");
+-	} else if (moksize != 0) {
+-		rc = parse_efi_signature_list("UEFI:MokListRT",
+-					      mok, moksize, get_handler_for_db);
+-		if (rc)
+-			pr_err("Couldn't parse MokListRT signatures: %d\n", rc);
+-		kfree(mok);
+-	}
+-
+ 	rc = get_cert_list(L"dbx", &secure_var, &dbxsize, &dbx);
+ 	if (rc < 0) {
+ 		pr_info("MODSIGN: Couldn't get UEFI dbx list\n");
+@@ -194,6 +183,21 @@
+ 		kfree(dbx);
+ 	}
+ 
+	/* the MOK can not be trusted when secure boot is disabled */
+	if (!efi_enabled(EFI_SECURE_BOOT))
+		return 0;
+
+	rc = get_cert_list(L"MokListRT", &mok_var, &moksize, &mok);
+	if (rc < 0) {
+		pr_info("MODSIGN: Couldn't get UEFI MokListRT\n");
+	} else if (moksize != 0) {
+		rc = parse_efi_signature_list("UEFI:MokListRT",
+					      mok, moksize, get_handler_for_db);
+		if (rc)
+			pr_err("Couldn't parse MokListRT signatures: %d\n", rc);
+		kfree(mok);
+	}
+
+ 	return rc;
+ }
+ late_initcall(load_uefi_certs);
--- a/debian/patches/features/all/db-mok-keyring/0002-MODSIGN-load-blacklist-from-MOKx.patch
+++ b/debian/patches/features/all/db-mok-keyring/0002-MODSIGN-load-blacklist-from-MOKx.patch
@ -0,0 +1,55 @@
+Origin: https://lore.kernel.org/patchwork/cover/933178/
+From: "Lee, Chun-Yi" <joeyli.kernel@gmail.com>
+Subject: [PATCH 2/4] MODSIGN: load blacklist from MOKx
+
+This patch adds the logic to load the blacklisted hash and
+certificates from MOKx which is maintained by shim bootloader.
+
+Signed-off-by: "Lee, Chun-Yi" <jlee@suse.com>
+---
+ certs/load_uefi.c | 16 +++++++++++++---
+ 1 file changed, 13 insertions(+), 3 deletions(-)
+
+diff --git a/certs/load_uefi.c b/certs/load_uefi.c
+index f2f372b..dc66a79 100644
+--- a/certs/load_uefi.c
+++ b/certs/load_uefi.c
+@@ -148,8 +148,8 @@
+ {
+ 	efi_guid_t secure_var = EFI_IMAGE_SECURITY_DATABASE_GUID;
+ 	efi_guid_t mok_var = EFI_SHIM_LOCK_GUID;
+-	void *db = NULL, *dbx = NULL, *mok = NULL;
+-	unsigned long dbsize = 0, dbxsize = 0, moksize = 0;
+	void *db = NULL, *dbx = NULL, *mok = NULL, *mokx = NULL;
+	unsigned long dbsize = 0, dbxsize = 0, moksize = 0, mokxsize = 0;
+ 	int rc = 0;
+ 
+ 	if (!efi.get_variable)
+@@ -183,7 +183,7 @@
+ 		kfree(dbx);
+ 	}
+ 
+-	/* the MOK can not be trusted when secure boot is disabled */
+	/* the MOK and MOKx can not be trusted when secure boot is disabled */
+ 	if (!efi_enabled(EFI_SECURE_BOOT))
+ 		return 0;
+ 
+@@ -198,6 +198,18 @@
+ 		kfree(mok);
+ 	}
+ 
+	rc = get_cert_list(L"MokListXRT", &mok_var, &mokxsize, &mokx);
+	if (rc < 0) {
+		pr_info("MODSIGN: Couldn't get UEFI MokListXRT\n");
+	} else if (mokxsize != 0) {
+		rc = parse_efi_signature_list("UEFI:mokx",
+					      mokx, mokxsize,
+					      get_handler_for_dbx);
+		if (rc)
+			pr_err("Couldn't parse MokListXRT signatures: %d\n", rc);
+		kfree(mokx);
+	}
+
+ 	return rc;
+ }
+ late_initcall(load_uefi_certs);
--- a/debian/patches/features/all/db-mok-keyring/0003-MODSIGN-checking-the-blacklisted-hash-before-loading-a-kernel-module.patch
+++ b/debian/patches/features/all/db-mok-keyring/0003-MODSIGN-checking-the-blacklisted-hash-before-loading-a-kernel-module.patch
@ -0,0 +1,124 @@
+Origin: https://lore.kernel.org/patchwork/cover/933178/
+From: "Lee, Chun-Yi" <joeyli.kernel@gmail.com>
+Subject: [PATCH 3/4] MODSIGN: checking the blacklisted hash before loading a
+ kernel module
+
+This patch adds the logic for checking the kernel module's hash
+base on blacklist. The hash must be generated by sha256 and enrolled
+to dbx/mokx.
+
+For example:
+	sha256sum sample.ko
+	mokutil --mokx --import-hash $HASH_RESULT
+
+Whether the signature on ko file is stripped or not, the hash can be
+compared by kernel.
+
+Signed-off-by: "Lee, Chun-Yi" <jlee@suse.com>
+---
+ kernel/module_signing.c | 62 +++++++++++++++++++++++++++++++++++++++++++++++--
+ 1 file changed, 60 insertions(+), 2 deletions(-)
+
+diff --git a/kernel/module_signing.c b/kernel/module_signing.c
+index d3d6f95..d30ac74 100644
+--- a/kernel/module_signing.c
+++ b/kernel/module_signing.c
+@@ -11,9 +11,12 @@
+ 
+ #include <linux/kernel.h>
+ #include <linux/errno.h>
+#include <linux/module.h>
+ #include <linux/string.h>
+ #include <linux/verification.h>
+ #include <crypto/public_key.h>
+#include <crypto/hash.h>
+#include <keys/system_keyring.h>
+ #include "module-internal.h"
+ 
+ enum pkey_id_type {
+@@ -42,19 +45,67 @@
+ 	__be32	sig_len;	/* Length of signature data */
+ };
+ 
+static int mod_is_hash_blacklisted(const void *mod, size_t verifylen)
+{
+	struct crypto_shash *tfm;
+	struct shash_desc *desc;
+	size_t digest_size, desc_size;
+	u8 *digest;
+	int ret = 0;
+
+	tfm = crypto_alloc_shash("sha256", 0, 0);
+	if (IS_ERR(tfm))
+		goto error_return;
+
+	desc_size = crypto_shash_descsize(tfm) + sizeof(*desc);
+	digest_size = crypto_shash_digestsize(tfm);
+	digest = kzalloc(digest_size + desc_size, GFP_KERNEL);
+	if (!digest) {
+		pr_err("digest memory buffer allocate fail\n");
+		ret = -ENOMEM;
+		goto error_digest;
+	}
+	desc = (void *)digest + digest_size;
+	desc->tfm = tfm;
+	desc->flags = CRYPTO_TFM_REQ_MAY_SLEEP;
+	ret = crypto_shash_init(desc);
+	if (ret < 0)
+		goto error_shash;
+
+	ret = crypto_shash_finup(desc, mod, verifylen, digest);
+	if (ret < 0)
+		goto error_shash;
+
+	pr_debug("%ld digest: %*phN\n", verifylen, (int) digest_size, digest);
+
+	ret = is_hash_blacklisted(digest, digest_size, "bin");
+	if (ret == -EKEYREJECTED)
+		pr_err("Module hash %*phN is blacklisted\n",
+		       (int) digest_size, digest);
+
+error_shash:
+	kfree(digest);
+error_digest:
+	crypto_free_shash(tfm);
+error_return:
+	return ret;
+}
+
+ /*
+  * Verify the signature on a module.
+  */
+ int mod_verify_sig(const void *mod, struct load_info *info)
+ {
+ 	struct module_signature ms;
+-	size_t sig_len, modlen = info->len;
+	size_t sig_len, modlen = info->len, wholelen;
+	int ret;;
+ 
+ 	pr_devel("==>%s(,%zu)\n", __func__, modlen);
+ 
+ 	if (modlen <= sizeof(ms))
+ 		return -EBADMSG;
+ 
+	wholelen = modlen + sizeof(MODULE_SIG_STRING) - 1;
+ 	memcpy(&ms, mod + (modlen - sizeof(ms)), sizeof(ms));
+ 	modlen -= sizeof(ms);
+ 
+@@ -82,8 +133,15 @@
+ 		return -EBADMSG;
+ 	}
+ 
+-	return verify_pkcs7_signature(mod, modlen, mod + modlen, sig_len,
+	ret = verify_pkcs7_signature(mod, modlen, mod + modlen, sig_len,
+ 				      VERIFY_USE_SECONDARY_KEYRING,
+ 				      VERIFYING_MODULE_SIGNATURE,
+ 				      NULL, NULL);
+	pr_devel("verify_pkcs7_signature() = %d\n", ret);
+
+	/* checking hash of module is in blacklist */
+	if (!ret)
+		ret = mod_is_hash_blacklisted(mod, wholelen);
+
+	return ret;
+ }
--- a/debian/patches/features/all/db-mok-keyring/0004-MODSIGN-check-the-attributes-of-db-and-mok.patch
+++ b/debian/patches/features/all/db-mok-keyring/0004-MODSIGN-check-the-attributes-of-db-and-mok.patch
@ -0,0 +1,103 @@
+Origin: https://lore.kernel.org/patchwork/cover/933178/
+From: "Lee, Chun-Yi" <joeyli.kernel@gmail.com>
+Subject: [PATCH 4/4] MODSIGN: check the attributes of db and mok
+
+That's better for checking the attributes of db and mok variables
+before loading certificates to kernel keyring.
+
+For db and dbx, both of them are authenticated variables. Which
+means that they can only be modified by manufacturer's key. So
+the kernel should checks EFI_VARIABLE_TIME_BASED_AUTHENTICATED_WRITE_ACCESS
+attribute before we trust it.
+
+For mok-rt and mokx-rt, both of them are created by shim boot loader
+to forward the mok/mokx content to runtime. They must be runtime-volatile
+variables. So kernel should checks that the attributes map did not set
+EFI_VARIABLE_NON_VOLATILE bit before we trust it.
+
+Signed-off-by: "Lee, Chun-Yi" <jlee@suse.com>
+---
+ certs/load_uefi.c | 35 +++++++++++++++++++++++------------
+ 1 file changed, 23 insertions(+), 12 deletions(-)
+
+diff --git a/certs/load_uefi.c b/certs/load_uefi.c
+index dc66a79..52526bd 100644
+--- a/certs/load_uefi.c
+++ b/certs/load_uefi.c
+@@ -36,12 +36,14 @@
+  * Get a certificate list blob from the named EFI variable.
+  */
+ static __init int get_cert_list(efi_char16_t *name, efi_guid_t *guid,
+-				unsigned long *size, void **cert_list)
+				unsigned long *size, void **cert_list,
+				u32 pos_attr, u32 neg_attr)
+ {
+ 	efi_status_t status;
+ 	unsigned long lsize = 4;
+ 	unsigned long tmpdb[4];
+ 	void *db;
+	u32 attr = 0;
+ 
+ 	status = efi.get_variable(name, guid, NULL, &lsize, &tmpdb);
+ 	if (status == EFI_NOT_FOUND) {
+@@ -61,12 +63,19 @@
+ 		return -ENOMEM;
+ 	}
+ 
+-	status = efi.get_variable(name, guid, NULL, &lsize, db);
+	status = efi.get_variable(name, guid, &attr, &lsize, db);
+ 	if (status != EFI_SUCCESS) {
+ 		kfree(db);
+ 		pr_err("Error reading db var: 0x%lx\n", status);
+ 		return efi_status_to_err(status);
+ 	}
+	/* must have positive attributes and no negative attributes */
+	if ((pos_attr && !(attr & pos_attr)) ||
+	    (neg_attr && (attr & neg_attr))) {
+		kfree(db);
+		pr_err("Error reading db var attributes: 0x%016x\n", attr);
+		return -1;
+	}
+ 
+ 	*size = lsize;
+ 	*cert_list = db;
+@@ -159,7 +168,8 @@
+ 	 * an error if we can't get them.
+ 	 */
+ 	if (!uefi_check_ignore_db()) {
+-		rc = get_cert_list(L"db", &secure_var, &dbsize, &db);
+		rc = get_cert_list(L"db", &secure_var, &dbsize, &db,
+			EFI_VARIABLE_TIME_BASED_AUTHENTICATED_WRITE_ACCESS, 0);
+ 		if (rc < 0) {
+ 			pr_err("MODSIGN: Couldn't get UEFI db list\n");
+ 		} else if (dbsize != 0) {
+@@ -171,7 +181,8 @@
+ 		}
+ 	}
+ 
+-	rc = get_cert_list(L"dbx", &secure_var, &dbxsize, &dbx);
+	rc = get_cert_list(L"dbx", &secure_var, &dbxsize, &dbx,
+		EFI_VARIABLE_TIME_BASED_AUTHENTICATED_WRITE_ACCESS, 0);
+ 	if (rc < 0) {
+ 		pr_info("MODSIGN: Couldn't get UEFI dbx list\n");
+ 	} else if (dbxsize != 0) {
+@@ -187,7 +198,8 @@
+ 	if (!efi_enabled(EFI_SECURE_BOOT))
+ 		return 0;
+ 
+-	rc = get_cert_list(L"MokListRT", &mok_var, &moksize, &mok);
+	rc = get_cert_list(L"MokListRT", &mok_var, &moksize, &mok,
+				0, EFI_VARIABLE_NON_VOLATILE);
+ 	if (rc < 0) {
+ 		pr_info("MODSIGN: Couldn't get UEFI MokListRT\n");
+ 	} else if (moksize != 0) {
+@@ -198,7 +210,8 @@
+ 		kfree(mok);
+ 	}
+ 
+-	rc = get_cert_list(L"MokListXRT", &mok_var, &mokxsize, &mokx);
+	rc = get_cert_list(L"MokListXRT", &mok_var, &mokxsize, &mokx,
+				0, EFI_VARIABLE_NON_VOLATILE);
+ 	if (rc < 0) {
+ 		pr_info("MODSIGN: Couldn't get UEFI MokListXRT\n");
+ 	} else if (mokxsize != 0) {
--- a/debian/patches/series
+++ b/debian/patches/series
@ -151,6 +151,10 @@ features/all/db-mok-keyring/0004-MODSIGN-Import-certificates-from-UEFI-Secure-Bo
 features/all/db-mok-keyring/0005-MODSIGN-Allow-the-db-UEFI-variable-to-be-suppressed.patch
 features/all/db-mok-keyring/0006-Make-get_cert_list-not-complain-about-cert-lists-tha.patch
 features/all/db-mok-keyring/0007-modsign-Use-secondary-trust-keyring-for-module-signi.patch
+features/all/db-mok-keyring/0001-MODSIGN-do-not-load-mok-when-secure-boot-disabled.patch
+features/all/db-mok-keyring/0002-MODSIGN-load-blacklist-from-MOKx.patch
+features/all/db-mok-keyring/0003-MODSIGN-checking-the-blacklisted-hash-before-loading-a-kernel-module.patch
+features/all/db-mok-keyring/0004-MODSIGN-check-the-attributes-of-db-and-mok.patch

 # Security fixes
 debian/i386-686-pae-pci-set-pci-nobios-by-default.patch