[PATCH v2 6/7] efi: Allow the "db" UEFI variable to be suppressed
From: Nayna Jain <nayna@linux.ibm.com>
Date: 2018-12-08 20:31:17
Also in:
kexec, keyrings, linux-efi, linux-integrity, lkml
Subsystem:
extended verification module (evm), integrity measurement architecture (ima), security subsystem, the rest · Maintainers:
Mimi Zohar, Roberto Sassu, Dmitry Kasatkin, Paul Moore, James Morris, "Serge E. Hallyn", Linus Torvalds
From: Josh Boyer <redacted> If a user tells shim to not use the certs/hashes in the UEFI db variable for verification purposes, shim will set a UEFI variable called MokIgnoreDB. Have the uefi import code look for this and ignore the db variable if it is found. Signed-off-by: Josh Boyer <redacted> Signed-off-by: David Howells <dhowells@redhat.com> Acked-by: Nayna Jain <nayna@linux.ibm.com> Acked-by: Serge Hallyn <serge@hallyn.com> --- Changelog: v0: - No changes v2: - Fixed the checkpatch.pl warnings security/integrity/platform_certs/load_uefi.c | 45 +++++++++++++++++++++------ 1 file changed, 35 insertions(+), 10 deletions(-)
diff --git a/security/integrity/platform_certs/load_uefi.c b/security/integrity/platform_certs/load_uefi.c
index acd9db90dde7..8bd2e9b421e1 100644
--- a/security/integrity/platform_certs/load_uefi.c
+++ b/security/integrity/platform_certs/load_uefi.c@@ -16,6 +16,26 @@ static efi_guid_t efi_cert_x509_sha256_guid __initdata = static efi_guid_t efi_cert_sha256_guid __initdata = EFI_CERT_SHA256_GUID; /* + * Look to see if a UEFI variable called MokIgnoreDB exists and return true if + * it does. + * + * This UEFI variable is set by the shim if a user tells the shim to not use + * the certs/hashes in the UEFI db variable for verification purposes. If it + * is set, we should ignore the db variable also and the true return indicates + * this. + */ +static __init bool uefi_check_ignore_db(void) +{ + efi_status_t status; + unsigned int db = 0; + unsigned long size = sizeof(db); + efi_guid_t guid = EFI_SHIM_LOCK_GUID; + + status = efi.get_variable(L"MokIgnoreDB", &guid, NULL, &size, &db); + return status == EFI_SUCCESS; +} + +/* * Get a certificate list blob from the named EFI variable. */ static __init void *get_cert_list(efi_char16_t *name, efi_guid_t *guid,
@@ -116,7 +136,9 @@ static __init efi_element_handler_t get_handler_for_dbx(const efi_guid_t * } /* - * Load the certs contained in the UEFI databases + * Load the certs contained in the UEFI databases into the secondary trusted + * keyring and the UEFI blacklisted X.509 cert SHA256 hashes into the blacklist + * keyring. */ static int __init load_uefi_certs(void) {
@@ -132,15 +154,18 @@ static int __init load_uefi_certs(void) /* 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("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); + if (!uefi_check_ignore_db()) { + 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);
--
2.13.6