| // 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); |