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// SPDX-License-Identifier: GPL-2.0
#include <linux/kernel.h>
#include <linux/sched.h>
#include <linux/cred.h>
#include <linux/dmi.h>
#include <linux/err.h>
#include <linux/efi.h>
#include <linux/slab.h>
#include <linux/ima.h>
#include <keys/asymmetric-type.h>
#include <keys/system_keyring.h>
#include "../integrity.h"
#include "keyring_handler.h"
/*
* On T2 Macs reading the db and dbx efi variables to load UEFI Secure Boot
* certificates causes occurrence of a page fault in Apple's firmware and
* a crash disabling EFI runtime services. The following quirk skips reading
* these variables.
*/
static const struct dmi_system_id uefi_skip_cert[] = {
{ UEFI_QUIRK_SKIP_CERT("Apple Inc.", "MacBookPro15,1") },
{ UEFI_QUIRK_SKIP_CERT("Apple Inc.", "MacBookPro15,2") },
{ UEFI_QUIRK_SKIP_CERT("Apple Inc.", "MacBookPro15,3") },
{ UEFI_QUIRK_SKIP_CERT("Apple Inc.", "MacBookPro15,4") },
{ UEFI_QUIRK_SKIP_CERT("Apple Inc.", "MacBookPro16,1") },
{ UEFI_QUIRK_SKIP_CERT("Apple Inc.", "MacBookPro16,2") },
{ UEFI_QUIRK_SKIP_CERT("Apple Inc.", "MacBookPro16,3") },
{ UEFI_QUIRK_SKIP_CERT("Apple Inc.", "MacBookPro16,4") },
{ UEFI_QUIRK_SKIP_CERT("Apple Inc.", "MacBookAir8,1") },
{ UEFI_QUIRK_SKIP_CERT("Apple Inc.", "MacBookAir8,2") },
{ UEFI_QUIRK_SKIP_CERT("Apple Inc.", "MacBookAir9,1") },
{ UEFI_QUIRK_SKIP_CERT("Apple Inc.", "Macmini8,1") },
{ UEFI_QUIRK_SKIP_CERT("Apple Inc.", "MacPro7,1") },
{ UEFI_QUIRK_SKIP_CERT("Apple Inc.", "iMac20,1") },
{ UEFI_QUIRK_SKIP_CERT("Apple Inc.", "iMac20,2") },
{ }
};
/*
* 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,
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_NOT_FOUND)
return NULL;
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)
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;
}
/*
* load_moklist_certs() - Load MokList certs
*
* Load the certs contained in the UEFI MokListRT database into the
* platform trusted keyring.
*
* This routine checks the EFI MOK config table first. If and only if
* that fails, this routine uses the MokListRT ordinary UEFI variable.
*
* Return: Status
*/
static int __init load_moklist_certs(void)
{
struct efi_mokvar_table_entry *mokvar_entry;
efi_guid_t mok_var = EFI_SHIM_LOCK_GUID;
void *mok;
unsigned long moksize;
efi_status_t status;
int rc;
/* First try to load certs from the EFI MOKvar config table.
* It's not an error if the MOKvar config table doesn't exist
* or the MokListRT entry is not found in it.
*/
mokvar_entry = efi_mokvar_entry_find("MokListRT");
if (mokvar_entry) {
rc = parse_efi_signature_list("UEFI:MokListRT (MOKvar table)",
mokvar_entry->data,
mokvar_entry->data_size,
get_handler_for_mok);
/* All done if that worked. */
if (!rc)
return rc;
pr_err("Couldn't parse MokListRT signatures from EFI MOKvar config table: %d\n",
rc);
}
/* Get MokListRT. It might not exist, so it isn't an error
* if we can't get it.
*/
mok = get_cert_list(L"MokListRT", &mok_var, &moksize, &status);
if (mok) {
rc = parse_efi_signature_list("UEFI:MokListRT",
mok, moksize, get_handler_for_mok);
kfree(mok);
if (rc)
pr_err("Couldn't parse MokListRT signatures: %d\n", rc);
return rc;
}
if (status == EFI_NOT_FOUND)
pr_debug("MokListRT variable wasn't found\n");
else
pr_info("Couldn't get UEFI MokListRT\n");
return 0;
}
/*
* load_uefi_certs() - Load certs from UEFI sources
*
* 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)
{
efi_guid_t secure_var = EFI_IMAGE_SECURITY_DATABASE_GUID;
efi_guid_t mok_var = EFI_SHIM_LOCK_GUID;
void *db = NULL, *dbx = NULL, *mokx = NULL;
unsigned long dbsize = 0, dbxsize = 0, mokxsize = 0;
efi_status_t status;
int rc = 0;
const struct dmi_system_id *dmi_id;
dmi_id = dmi_first_match(uefi_skip_cert);
if (dmi_id) {
pr_err("Reading UEFI Secure Boot Certs is not supported on T2 Macs.\n");
return false;
}
if (!efi_rt_services_supported(EFI_RT_SUPPORTED_GET_VARIABLE))
return false;
/* Get db and dbx. They might not exist, so it isn't an error
* if we can't get them.
*/
if (!uefi_check_ignore_db()) {
db = get_cert_list(L"db", &secure_var, &dbsize, &status);
if (!db) {
if (status == EFI_NOT_FOUND)
pr_debug("MODSIGN: db variable wasn't found\n");
else
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);
}
}
dbx = get_cert_list(L"dbx", &secure_var, &dbxsize, &status);
if (!dbx) {
if (status == EFI_NOT_FOUND)
pr_debug("dbx variable wasn't found\n");
else
pr_info("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);
}
/* the MOK/MOKx can not be trusted when secure boot is disabled */
if (!arch_ima_get_secureboot())
return 0;
mokx = get_cert_list(L"MokListXRT", &mok_var, &mokxsize, &status);
if (!mokx) {
if (status == EFI_NOT_FOUND)
pr_debug("mokx variable wasn't found\n");
else
pr_info("Couldn't get mokx list\n");
} else {
rc = parse_efi_signature_list("UEFI:MokListXRT",
mokx, mokxsize,
get_handler_for_dbx);
if (rc)
pr_err("Couldn't parse mokx signatures %d\n", rc);
kfree(mokx);
}
/* Load the MokListRT certs */
rc = load_moklist_certs();
return rc;
}
late_initcall(load_uefi_certs);
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