239 lines
6.7 KiB
C
239 lines
6.7 KiB
C
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// SPDX-License-Identifier: GPL-2.0
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#include <linux/kernel.h>
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#include <linux/sched.h>
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#include <linux/cred.h>
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#include <linux/dmi.h>
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#include <linux/err.h>
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#include <linux/efi.h>
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#include <linux/slab.h>
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#include <linux/ima.h>
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#include <keys/asymmetric-type.h>
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#include <keys/system_keyring.h>
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#include "../integrity.h"
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#include "keyring_handler.h"
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/*
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* On T2 Macs reading the db and dbx efi variables to load UEFI Secure Boot
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* certificates causes occurrence of a page fault in Apple's firmware and
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* a crash disabling EFI runtime services. The following quirk skips reading
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* these variables.
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*/
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static const struct dmi_system_id uefi_skip_cert[] = {
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{ UEFI_QUIRK_SKIP_CERT("Apple Inc.", "MacBookPro15,1") },
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{ UEFI_QUIRK_SKIP_CERT("Apple Inc.", "MacBookPro15,2") },
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{ UEFI_QUIRK_SKIP_CERT("Apple Inc.", "MacBookPro15,3") },
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{ UEFI_QUIRK_SKIP_CERT("Apple Inc.", "MacBookPro15,4") },
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{ UEFI_QUIRK_SKIP_CERT("Apple Inc.", "MacBookPro16,1") },
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{ UEFI_QUIRK_SKIP_CERT("Apple Inc.", "MacBookPro16,2") },
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{ UEFI_QUIRK_SKIP_CERT("Apple Inc.", "MacBookPro16,3") },
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{ UEFI_QUIRK_SKIP_CERT("Apple Inc.", "MacBookPro16,4") },
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{ UEFI_QUIRK_SKIP_CERT("Apple Inc.", "MacBookAir8,1") },
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{ UEFI_QUIRK_SKIP_CERT("Apple Inc.", "MacBookAir8,2") },
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{ UEFI_QUIRK_SKIP_CERT("Apple Inc.", "MacBookAir9,1") },
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{ UEFI_QUIRK_SKIP_CERT("Apple Inc.", "Macmini8,1") },
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{ UEFI_QUIRK_SKIP_CERT("Apple Inc.", "MacPro7,1") },
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{ UEFI_QUIRK_SKIP_CERT("Apple Inc.", "iMac20,1") },
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{ UEFI_QUIRK_SKIP_CERT("Apple Inc.", "iMac20,2") },
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{ UEFI_QUIRK_SKIP_CERT("Apple Inc.", "iMacPro1,1") },
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{ }
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};
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/*
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* Look to see if a UEFI variable called MokIgnoreDB exists and return true if
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* it does.
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*
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* This UEFI variable is set by the shim if a user tells the shim to not use
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* the certs/hashes in the UEFI db variable for verification purposes. If it
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* is set, we should ignore the db variable also and the true return indicates
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* this.
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*/
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static __init bool uefi_check_ignore_db(void)
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{
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efi_status_t status;
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unsigned int db = 0;
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unsigned long size = sizeof(db);
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efi_guid_t guid = EFI_SHIM_LOCK_GUID;
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status = efi.get_variable(L"MokIgnoreDB", &guid, NULL, &size, &db);
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return status == EFI_SUCCESS;
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}
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/*
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* Get a certificate list blob from the named EFI variable.
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*/
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static __init void *get_cert_list(efi_char16_t *name, efi_guid_t *guid,
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unsigned long *size, efi_status_t *status)
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{
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unsigned long lsize = 4;
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unsigned long tmpdb[4];
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void *db;
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*status = efi.get_variable(name, guid, NULL, &lsize, &tmpdb);
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if (*status == EFI_NOT_FOUND)
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return NULL;
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if (*status != EFI_BUFFER_TOO_SMALL) {
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pr_err("Couldn't get size: 0x%lx\n", *status);
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return NULL;
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}
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db = kmalloc(lsize, GFP_KERNEL);
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if (!db)
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return NULL;
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*status = efi.get_variable(name, guid, NULL, &lsize, db);
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if (*status != EFI_SUCCESS) {
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kfree(db);
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pr_err("Error reading db var: 0x%lx\n", *status);
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return NULL;
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}
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*size = lsize;
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return db;
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}
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/*
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* load_moklist_certs() - Load MokList certs
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*
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* Load the certs contained in the UEFI MokListRT database into the
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* platform trusted keyring.
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*
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* This routine checks the EFI MOK config table first. If and only if
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* that fails, this routine uses the MokListRT ordinary UEFI variable.
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*
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* Return: Status
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*/
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static int __init load_moklist_certs(void)
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{
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struct efi_mokvar_table_entry *mokvar_entry;
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efi_guid_t mok_var = EFI_SHIM_LOCK_GUID;
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void *mok;
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unsigned long moksize;
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efi_status_t status;
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int rc;
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/* First try to load certs from the EFI MOKvar config table.
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* It's not an error if the MOKvar config table doesn't exist
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* or the MokListRT entry is not found in it.
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*/
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mokvar_entry = efi_mokvar_entry_find("MokListRT");
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if (mokvar_entry) {
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rc = parse_efi_signature_list("UEFI:MokListRT (MOKvar table)",
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mokvar_entry->data,
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mokvar_entry->data_size,
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get_handler_for_mok);
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/* All done if that worked. */
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if (!rc)
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return rc;
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pr_err("Couldn't parse MokListRT signatures from EFI MOKvar config table: %d\n",
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rc);
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}
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/* Get MokListRT. It might not exist, so it isn't an error
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* if we can't get it.
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*/
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mok = get_cert_list(L"MokListRT", &mok_var, &moksize, &status);
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if (mok) {
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rc = parse_efi_signature_list("UEFI:MokListRT",
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mok, moksize, get_handler_for_mok);
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kfree(mok);
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if (rc)
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pr_err("Couldn't parse MokListRT signatures: %d\n", rc);
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return rc;
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}
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if (status == EFI_NOT_FOUND)
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pr_debug("MokListRT variable wasn't found\n");
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else
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pr_info("Couldn't get UEFI MokListRT\n");
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return 0;
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}
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/*
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* load_uefi_certs() - Load certs from UEFI sources
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*
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* Load the certs contained in the UEFI databases into the platform trusted
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* keyring and the UEFI blacklisted X.509 cert SHA256 hashes into the blacklist
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* keyring.
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*/
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static int __init load_uefi_certs(void)
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{
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efi_guid_t secure_var = EFI_IMAGE_SECURITY_DATABASE_GUID;
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efi_guid_t mok_var = EFI_SHIM_LOCK_GUID;
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void *db = NULL, *dbx = NULL, *mokx = NULL;
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unsigned long dbsize = 0, dbxsize = 0, mokxsize = 0;
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efi_status_t status;
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int rc = 0;
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const struct dmi_system_id *dmi_id;
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dmi_id = dmi_first_match(uefi_skip_cert);
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if (dmi_id) {
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pr_err("Reading UEFI Secure Boot Certs is not supported on T2 Macs.\n");
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return false;
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}
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if (!efi_rt_services_supported(EFI_RT_SUPPORTED_GET_VARIABLE))
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return false;
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/* Get db and dbx. They might not exist, so it isn't an error
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* if we can't get them.
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*/
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if (!uefi_check_ignore_db()) {
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db = get_cert_list(L"db", &secure_var, &dbsize, &status);
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if (!db) {
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if (status == EFI_NOT_FOUND)
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pr_debug("MODSIGN: db variable wasn't found\n");
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else
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pr_err("MODSIGN: Couldn't get UEFI db list\n");
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} else {
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rc = parse_efi_signature_list("UEFI:db",
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db, dbsize, get_handler_for_db);
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if (rc)
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pr_err("Couldn't parse db signatures: %d\n",
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rc);
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kfree(db);
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}
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}
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dbx = get_cert_list(L"dbx", &secure_var, &dbxsize, &status);
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if (!dbx) {
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if (status == EFI_NOT_FOUND)
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pr_debug("dbx variable wasn't found\n");
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else
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pr_info("Couldn't get UEFI dbx list\n");
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} else {
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rc = parse_efi_signature_list("UEFI:dbx",
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dbx, dbxsize,
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get_handler_for_dbx);
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if (rc)
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pr_err("Couldn't parse dbx signatures: %d\n", rc);
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kfree(dbx);
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}
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/* the MOK/MOKx can not be trusted when secure boot is disabled */
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if (!arch_ima_get_secureboot())
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return 0;
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mokx = get_cert_list(L"MokListXRT", &mok_var, &mokxsize, &status);
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if (!mokx) {
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if (status == EFI_NOT_FOUND)
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pr_debug("mokx variable wasn't found\n");
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else
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pr_info("Couldn't get mokx list\n");
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} else {
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rc = parse_efi_signature_list("UEFI:MokListXRT",
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mokx, mokxsize,
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get_handler_for_dbx);
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if (rc)
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pr_err("Couldn't parse mokx signatures %d\n", rc);
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kfree(mokx);
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}
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/* Load the MokListRT certs */
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rc = load_moklist_certs();
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return rc;
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}
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late_initcall(load_uefi_certs);
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