diff options
Diffstat (limited to 'debian/patches/features/all/db-mok-keyring/0004-MODSIGN-Import-certificates-from-UEFI-Secure-Boot.patch')
| -rw-r--r-- | debian/patches/features/all/db-mok-keyring/0004-MODSIGN-Import-certificates-from-UEFI-Secure-Boot.patch | 242 |
1 files changed, 242 insertions, 0 deletions
diff --git a/debian/patches/features/all/db-mok-keyring/0004-MODSIGN-Import-certificates-from-UEFI-Secure-Boot.patch b/debian/patches/features/all/db-mok-keyring/0004-MODSIGN-Import-certificates-from-UEFI-Secure-Boot.patch new file mode 100644 index 000000000..cdb3b7a22 --- /dev/null +++ b/debian/patches/features/all/db-mok-keyring/0004-MODSIGN-Import-certificates-from-UEFI-Secure-Boot.patch @@ -0,0 +1,242 @@ +From: Josh Boyer <jwboyer@fedoraproject.org> +Date: Fri, 5 May 2017 08:21:59 +0100 +Subject: [PATCH 4/7] MODSIGN: Import certificates from UEFI Secure Boot +Origin: https://git.kernel.org/pub/scm/linux/kernel/git/jforbes/linux.git/commit/?id=7b7aae2efea13b5a7b80305856c28f235ea8b2fa + +Secure Boot stores a list of allowed certificates in the 'db' variable. +This imports those certificates into the system trusted keyring. This +allows for a third party signing certificate to be used in conjunction +with signed modules. By importing the public certificate into the 'db' +variable, a user can allow a module signed with that certificate to +load. The shim UEFI bootloader has a similar certificate list stored +in the 'MokListRT' variable. We import those as well. + +Secure Boot also maintains a list of disallowed certificates in the 'dbx' +variable. We load those certificates into the newly introduced system +blacklist keyring and forbid any module signed with those from loading and +forbid the use within the kernel of any key with a matching hash. + +This facility is enabled by setting CONFIG_LOAD_UEFI_KEYS. + +Signed-off-by: Josh Boyer <jwboyer@fedoraproject.org> +Signed-off-by: David Howells <dhowells@redhat.com> +--- + certs/Kconfig | 16 +++++ + certs/Makefile | 4 ++ + certs/load_uefi.c | 168 ++++++++++++++++++++++++++++++++++++++++++++++ + 3 files changed, 188 insertions(+) + create mode 100644 certs/load_uefi.c + +Index: linux/certs/Kconfig +=================================================================== +--- linux.orig/certs/Kconfig ++++ linux/certs/Kconfig +@@ -91,4 +91,20 @@ config EFI_SIGNATURE_LIST_PARSER + This option provides support for parsing EFI signature lists for + X.509 certificates and turning them into keys. + ++config LOAD_UEFI_KEYS ++ bool "Load certs and blacklist from UEFI db for module checking" ++ depends on SYSTEM_BLACKLIST_KEYRING ++ depends on SECONDARY_TRUSTED_KEYRING ++ depends on EFI ++ depends on EFI_SIGNATURE_LIST_PARSER ++ help ++ If the kernel is booted in secure boot mode, this option will cause ++ the kernel to load the certificates from the UEFI db and MokListRT ++ into the secondary trusted keyring. It will also load any X.509 ++ SHA256 hashes in the dbx list into the blacklist. ++ ++ The effect of this is that, if the kernel is booted in secure boot ++ mode, modules signed with UEFI-stored keys will be permitted to be ++ loaded and keys that match the blacklist will be rejected. ++ + endmenu +Index: linux/certs/Makefile +=================================================================== +--- linux.orig/certs/Makefile ++++ linux/certs/Makefile +@@ -12,6 +12,10 @@ obj-$(CONFIG_SYSTEM_BLACKLIST_KEYRING) + + endif + obj-$(CONFIG_EFI_SIGNATURE_LIST_PARSER) += efi_parser.o + ++obj-$(CONFIG_LOAD_UEFI_KEYS) += load_uefi.o ++$(obj)/load_uefi.o: KBUILD_CFLAGS += -fshort-wchar ++ ++ + ifeq ($(CONFIG_SYSTEM_TRUSTED_KEYRING),y) + + $(eval $(call config_filename,SYSTEM_TRUSTED_KEYS)) +Index: linux/certs/load_uefi.c +=================================================================== +--- /dev/null ++++ linux/certs/load_uefi.c +@@ -0,0 +1,168 @@ ++#include <linux/kernel.h> ++#include <linux/sched.h> ++#include <linux/cred.h> ++#include <linux/err.h> ++#include <linux/efi.h> ++#include <linux/slab.h> ++#include <keys/asymmetric-type.h> ++#include <keys/system_keyring.h> ++#include "internal.h" ++ ++static __initdata efi_guid_t efi_cert_x509_guid = EFI_CERT_X509_GUID; ++static __initdata efi_guid_t efi_cert_x509_sha256_guid = EFI_CERT_X509_SHA256_GUID; ++static __initdata efi_guid_t efi_cert_sha256_guid = EFI_CERT_SHA256_GUID; ++ ++/* ++ * Get a certificate list blob from the named EFI variable. ++ */ ++static __init void *get_cert_list(efi_char16_t *name, efi_guid_t *guid, ++ unsigned long *size) ++{ ++ efi_status_t status; ++ unsigned long lsize = 4; ++ unsigned long tmpdb[4]; ++ void *db; ++ ++ status = efi.get_variable(name, guid, NULL, &lsize, &tmpdb); ++ if (status != EFI_BUFFER_TOO_SMALL) { ++ pr_err("Couldn't get size: 0x%lx\n", status); ++ return NULL; ++ } ++ ++ db = kmalloc(lsize, GFP_KERNEL); ++ if (!db) { ++ pr_err("Couldn't allocate memory for uefi cert list\n"); ++ return NULL; ++ } ++ ++ status = efi.get_variable(name, guid, NULL, &lsize, db); ++ if (status != EFI_SUCCESS) { ++ kfree(db); ++ pr_err("Error reading db var: 0x%lx\n", status); ++ return NULL; ++ } ++ ++ *size = lsize; ++ return db; ++} ++ ++/* ++ * Blacklist an X509 TBS hash. ++ */ ++static __init void uefi_blacklist_x509_tbs(const char *source, ++ const void *data, size_t len) ++{ ++ char *hash, *p; ++ ++ hash = kmalloc(4 + len * 2 + 1, GFP_KERNEL); ++ if (!hash) ++ return; ++ p = memcpy(hash, "tbs:", 4); ++ p += 4; ++ bin2hex(p, data, len); ++ p += len * 2; ++ *p = 0; ++ ++ mark_hash_blacklisted(hash); ++ kfree(hash); ++} ++ ++/* ++ * Blacklist the hash of an executable. ++ */ ++static __init void uefi_blacklist_binary(const char *source, ++ const void *data, size_t len) ++{ ++ char *hash, *p; ++ ++ hash = kmalloc(4 + len * 2 + 1, GFP_KERNEL); ++ if (!hash) ++ return; ++ p = memcpy(hash, "bin:", 4); ++ p += 4; ++ bin2hex(p, data, len); ++ p += len * 2; ++ *p = 0; ++ ++ mark_hash_blacklisted(hash); ++ kfree(hash); ++} ++ ++/* ++ * Return the appropriate handler for particular signature list types found in ++ * the UEFI db and MokListRT tables. ++ */ ++static __init efi_element_handler_t get_handler_for_db(const efi_guid_t *sig_type) ++{ ++ if (efi_guidcmp(*sig_type, efi_cert_x509_guid) == 0) ++ return add_trusted_secondary_key; ++ return 0; ++} ++ ++/* ++ * Return the appropriate handler for particular signature list types found in ++ * the UEFI dbx and MokListXRT tables. ++ */ ++static __init efi_element_handler_t get_handler_for_dbx(const efi_guid_t *sig_type) ++{ ++ if (efi_guidcmp(*sig_type, efi_cert_x509_sha256_guid) == 0) ++ return uefi_blacklist_x509_tbs; ++ if (efi_guidcmp(*sig_type, efi_cert_sha256_guid) == 0) ++ return uefi_blacklist_binary; ++ return 0; ++} ++ ++/* ++ * Load the certs contained in the UEFI databases ++ */ ++static int __init load_uefi_certs(void) ++{ ++ 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; ++ int rc = 0; ++ ++ if (!efi.get_variable) ++ return false; ++ ++ /* Get db, MokListRT, and dbx. They might not exist, so it isn't ++ * an error if we can't get them. ++ */ ++ db = get_cert_list(L"db", &secure_var, &dbsize); ++ if (!db) { ++ pr_err("MODSIGN: Couldn't get UEFI db list\n"); ++ } else { ++ rc = parse_efi_signature_list("UEFI:db", ++ db, dbsize, get_handler_for_db); ++ if (rc) ++ pr_err("Couldn't parse db signatures: %d\n", rc); ++ kfree(db); ++ } ++ ++ mok = get_cert_list(L"MokListRT", &mok_var, &moksize); ++ if (!mok) { ++ pr_info("MODSIGN: Couldn't get UEFI MokListRT\n"); ++ } else { ++ 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); ++ } ++ ++ dbx = get_cert_list(L"dbx", &secure_var, &dbxsize); ++ if (!dbx) { ++ pr_info("MODSIGN: Couldn't get UEFI dbx list\n"); ++ } else { ++ rc = parse_efi_signature_list("UEFI:dbx", ++ dbx, dbxsize, ++ get_handler_for_dbx); ++ if (rc) ++ pr_err("Couldn't parse dbx signatures: %d\n", rc); ++ kfree(dbx); ++ } ++ ++ return rc; ++} ++late_initcall(load_uefi_certs); |