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efi: Allow the "db" UEFI variable to be suppressed 

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.

[zohar@linux.ibm.com: removed reference to "secondary" keyring comment]
Signed-off-by: Josh Boyer <jwboyer@fedoraproject.org>
Signed-off-by: David Howells <dhowells@redhat.com>
Acked-by: Nayna Jain <nayna@linux.ibm.com>
Acked-by: Serge Hallyn <serge@hallyn.com>
Reviewed-by: James Morris <james.morris@microsoft.com>
Signed-off-by: Mimi Zohar <zohar@linux.ibm.com>
This commit is contained in:
Josh Boyer 2018-12-09 01:57:04 +05:30 committed by Mimi Zohar
parent 15ea0e1e3e
commit 386b49f51d
1 changed files with 35 additions and 10 deletions
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45
security/integrity/platform_certs/load_uefi.c
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@ -15,6 +15,26 @@ static efi_guid_t efi_cert_x509_sha256_guid __initdata =
EFI_CERT_X509_SHA256_GUID;
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.
*/
@ -114,7 +134,9 @@ 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 platform trusted
* keyring and the UEFI blacklisted X.509 cert SHA256 hashes into the blacklist
* keyring.
*/
static int __init load_uefi_certs(void)
{
@ -130,15 +152,18 @@ 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);