diff options
Diffstat (limited to 'src/shared/efi-api.c')
| -rw-r--r-- | src/shared/efi-api.c | 556 |
1 files changed, 556 insertions, 0 deletions
diff --git a/src/shared/efi-api.c b/src/shared/efi-api.c new file mode 100644 index 0000000..4cd1091 --- /dev/null +++ b/src/shared/efi-api.c @@ -0,0 +1,556 @@ +/* SPDX-License-Identifier: LGPL-2.1-or-later */ + +#include <unistd.h> + +#include "alloc-util.h" +#include "dirent-util.h" +#include "efi-api.h" +#include "efivars.h" +#include "fd-util.h" +#include "sort-util.h" +#include "stat-util.h" +#include "stdio-util.h" +#include "utf8.h" + +#if ENABLE_EFI + +#define LOAD_OPTION_ACTIVE 0x00000001 +#define MEDIA_DEVICE_PATH 0x04 +#define MEDIA_HARDDRIVE_DP 0x01 +#define MEDIA_FILEPATH_DP 0x04 +#define SIGNATURE_TYPE_GUID 0x02 +#define MBR_TYPE_EFI_PARTITION_TABLE_HEADER 0x02 +#define END_DEVICE_PATH_TYPE 0x7f +#define END_ENTIRE_DEVICE_PATH_SUBTYPE 0xff + +#define EFI_OS_INDICATIONS_BOOT_TO_FW_UI UINT64_C(0x0000000000000001) + +#define boot_option__contents \ + { \ + uint32_t attr; \ + uint16_t path_len; \ + uint16_t title[]; \ + } + +struct boot_option boot_option__contents; +struct boot_option__packed boot_option__contents _packed_; +assert_cc(offsetof(struct boot_option, title) == offsetof(struct boot_option__packed, title)); +/* sizeof(struct boot_option) != sizeof(struct boot_option__packed), so + * the *size* of the structure should not be used anywhere below. */ + +struct drive_path { + uint32_t part_nr; + uint64_t part_start; + uint64_t part_size; + char signature[16]; + uint8_t mbr_type; + uint8_t signature_type; +} _packed_; + +#define device_path__contents \ + { \ + uint8_t type; \ + uint8_t sub_type; \ + uint16_t length; \ + union { \ + uint16_t path[0]; \ + struct drive_path drive; \ + }; \ + } + +struct device_path device_path__contents; +struct device_path__packed device_path__contents _packed_; +assert_cc(sizeof(struct device_path) == sizeof(struct device_path__packed)); + +int efi_reboot_to_firmware_supported(void) { + _cleanup_free_ void *v = NULL; + static int cache = -1; + uint64_t b; + size_t s; + int r; + + if (cache > 0) + return 0; + if (cache == 0) + return -EOPNOTSUPP; + + if (!is_efi_boot()) + goto not_supported; + + r = efi_get_variable(EFI_GLOBAL_VARIABLE(OsIndicationsSupported), NULL, &v, &s); + if (r == -ENOENT) + goto not_supported; /* variable doesn't exist? it's not supported then */ + if (r < 0) + return r; + if (s != sizeof(uint64_t)) + return -EINVAL; + + b = *(uint64_t*) v; + if (!(b & EFI_OS_INDICATIONS_BOOT_TO_FW_UI)) + goto not_supported; /* bit unset? it's not supported then */ + + cache = 1; + return 0; + +not_supported: + cache = 0; + return -EOPNOTSUPP; +} + +static int get_os_indications(uint64_t *ret) { + static struct stat cache_stat = {}; + _cleanup_free_ void *v = NULL; + static uint64_t cache; + struct stat new_stat; + size_t s; + int r; + + assert(ret); + + /* Let's verify general support first */ + r = efi_reboot_to_firmware_supported(); + if (r < 0) + return r; + + /* stat() the EFI variable, to see if the mtime changed. If it did we need to cache again. */ + if (stat(EFIVAR_PATH(EFI_GLOBAL_VARIABLE(OsIndications)), &new_stat) < 0) { + if (errno != ENOENT) + return -errno; + + /* Doesn't exist? Then we can exit early (also see below) */ + *ret = 0; + return 0; + + } else if (stat_inode_unmodified(&new_stat, &cache_stat)) { + /* inode didn't change, we can return the cached value */ + *ret = cache; + return 0; + } + + r = efi_get_variable(EFI_GLOBAL_VARIABLE(OsIndications), NULL, &v, &s); + if (r == -ENOENT) { + /* Some firmware implementations that do support OsIndications and report that with + * OsIndicationsSupported will remove the OsIndications variable when it is unset. Let's + * pretend it's 0 then, to hide this implementation detail. Note that this call will return + * -ENOENT then only if the support for OsIndications is missing entirely, as determined by + * efi_reboot_to_firmware_supported() above. */ + *ret = 0; + return 0; + } + if (r < 0) + return r; + if (s != sizeof(uint64_t)) + return -EINVAL; + + cache_stat = new_stat; + *ret = cache = *(uint64_t *)v; + return 0; +} + +int efi_get_reboot_to_firmware(void) { + int r; + uint64_t b; + + r = get_os_indications(&b); + if (r < 0) + return r; + + return !!(b & EFI_OS_INDICATIONS_BOOT_TO_FW_UI); +} + +int efi_set_reboot_to_firmware(bool value) { + int r; + uint64_t b, b_new; + + r = get_os_indications(&b); + if (r < 0) + return r; + + b_new = UPDATE_FLAG(b, EFI_OS_INDICATIONS_BOOT_TO_FW_UI, value); + + /* Avoid writing to efi vars store if we can due to firmware bugs. */ + if (b != b_new) + return efi_set_variable(EFI_GLOBAL_VARIABLE(OsIndications), &b_new, sizeof(uint64_t)); + + return 0; +} + +static ssize_t utf16_size(const uint16_t *s, size_t buf_len_bytes) { + size_t l = 0; + + /* Returns the size of the string in bytes without the terminating two zero bytes */ + + while (l < buf_len_bytes / sizeof(uint16_t)) { + if (s[l] == 0) + return (l + 1) * sizeof(uint16_t); + l++; + } + + return -EINVAL; /* The terminator was not found */ +} + +int efi_get_boot_option( + uint16_t id, + char **ret_title, + sd_id128_t *ret_part_uuid, + char **ret_path, + bool *ret_active) { + + char variable[STRLEN(EFI_GLOBAL_VARIABLE_STR("Boot")) + 4 + 1]; + _cleanup_free_ uint8_t *buf = NULL; + size_t l; + struct boot_option *header; + ssize_t title_size; + _cleanup_free_ char *s = NULL, *p = NULL; + sd_id128_t p_uuid = SD_ID128_NULL; + int r; + + if (!is_efi_boot()) + return -EOPNOTSUPP; + + xsprintf(variable, EFI_GLOBAL_VARIABLE_STR("Boot%04X"), id); + r = efi_get_variable(variable, NULL, (void **)&buf, &l); + if (r < 0) + return r; + if (l < offsetof(struct boot_option, title)) + return -ENOENT; + + header = (struct boot_option *)buf; + title_size = utf16_size(header->title, l - offsetof(struct boot_option, title)); + if (title_size < 0) + return title_size; + + if (ret_title) { + s = utf16_to_utf8(header->title, title_size); + if (!s) + return -ENOMEM; + } + + if (header->path_len > 0) { + uint8_t *dbuf; + size_t dnext, doff; + + doff = offsetof(struct boot_option, title) + title_size; + dbuf = buf + doff; + if (header->path_len > l - doff) + return -EINVAL; + + dnext = 0; + while (dnext < header->path_len) { + struct device_path *dpath; + + dpath = (struct device_path *)(dbuf + dnext); + if (dpath->length < 4) + break; + + /* Type 0x7F – End of Hardware Device Path, Sub-Type 0xFF – End Entire Device Path */ + if (dpath->type == END_DEVICE_PATH_TYPE && dpath->sub_type == END_ENTIRE_DEVICE_PATH_SUBTYPE) + break; + + dnext += dpath->length; + + /* Type 0x04 – Media Device Path */ + if (dpath->type != MEDIA_DEVICE_PATH) + continue; + + /* Sub-Type 1 – Hard Drive */ + if (dpath->sub_type == MEDIA_HARDDRIVE_DP) { + /* 0x02 – GUID Partition Table */ + if (dpath->drive.mbr_type != MBR_TYPE_EFI_PARTITION_TABLE_HEADER) + continue; + + /* 0x02 – GUID signature */ + if (dpath->drive.signature_type != SIGNATURE_TYPE_GUID) + continue; + + if (ret_part_uuid) + p_uuid = efi_guid_to_id128(dpath->drive.signature); + continue; + } + + /* Sub-Type 4 – File Path */ + if (dpath->sub_type == MEDIA_FILEPATH_DP && !p && ret_path) { + p = utf16_to_utf8(dpath->path, dpath->length-4); + if (!p) + return -ENOMEM; + + efi_tilt_backslashes(p); + continue; + } + } + } + + if (ret_title) + *ret_title = TAKE_PTR(s); + if (ret_part_uuid) + *ret_part_uuid = p_uuid; + if (ret_path) + *ret_path = TAKE_PTR(p); + if (ret_active) + *ret_active = header->attr & LOAD_OPTION_ACTIVE; + + return 0; +} + +static void to_utf16(uint16_t *dest, const char *src) { + int i; + + for (i = 0; src[i] != '\0'; i++) + dest[i] = src[i]; + dest[i] = '\0'; +} + +static uint16_t *tilt_slashes(uint16_t *s) { + for (uint16_t *p = s; *p; p++) + if (*p == '/') + *p = '\\'; + + return s; +} + +int efi_add_boot_option( + uint16_t id, + const char *title, + uint32_t part, + uint64_t pstart, + uint64_t psize, + sd_id128_t part_uuid, + const char *path) { + + size_t size, title_len, path_len; + _cleanup_free_ char *buf = NULL; + struct boot_option *option; + struct device_path *devicep; + char variable[STRLEN(EFI_GLOBAL_VARIABLE_STR("Boot")) + 4 + 1]; + + if (!is_efi_boot()) + return -EOPNOTSUPP; + + title_len = (strlen(title)+1) * 2; + path_len = (strlen(path)+1) * 2; + + buf = malloc0(offsetof(struct boot_option, title) + title_len + + sizeof(struct drive_path) + + sizeof(struct device_path) + path_len); + if (!buf) + return -ENOMEM; + + /* header */ + option = (struct boot_option *)buf; + option->attr = LOAD_OPTION_ACTIVE; + option->path_len = offsetof(struct device_path, drive) + sizeof(struct drive_path) + + offsetof(struct device_path, path) + path_len + + offsetof(struct device_path, path); + to_utf16(option->title, title); + size = offsetof(struct boot_option, title) + title_len; + + /* partition info */ + devicep = (struct device_path *)(buf + size); + devicep->type = MEDIA_DEVICE_PATH; + devicep->sub_type = MEDIA_HARDDRIVE_DP; + devicep->length = offsetof(struct device_path, drive) + sizeof(struct drive_path); + memcpy(&devicep->drive.part_nr, &part, sizeof(uint32_t)); + memcpy(&devicep->drive.part_start, &pstart, sizeof(uint64_t)); + memcpy(&devicep->drive.part_size, &psize, sizeof(uint64_t)); + efi_id128_to_guid(part_uuid, devicep->drive.signature); + devicep->drive.mbr_type = MBR_TYPE_EFI_PARTITION_TABLE_HEADER; + devicep->drive.signature_type = SIGNATURE_TYPE_GUID; + size += devicep->length; + + /* path to loader */ + devicep = (struct device_path *)(buf + size); + devicep->type = MEDIA_DEVICE_PATH; + devicep->sub_type = MEDIA_FILEPATH_DP; + devicep->length = offsetof(struct device_path, path) + path_len; + to_utf16(devicep->path, path); + tilt_slashes(devicep->path); + size += devicep->length; + + /* end of path */ + devicep = (struct device_path *)(buf + size); + devicep->type = END_DEVICE_PATH_TYPE; + devicep->sub_type = END_ENTIRE_DEVICE_PATH_SUBTYPE; + devicep->length = offsetof(struct device_path, path); + size += devicep->length; + + xsprintf(variable, EFI_GLOBAL_VARIABLE_STR("Boot%04X"), id); + return efi_set_variable(variable, buf, size); +} + +int efi_remove_boot_option(uint16_t id) { + char variable[STRLEN(EFI_GLOBAL_VARIABLE_STR("Boot")) + 4 + 1]; + + if (!is_efi_boot()) + return -EOPNOTSUPP; + + xsprintf(variable, EFI_GLOBAL_VARIABLE_STR("Boot%04X"), id); + return efi_set_variable(variable, NULL, 0); +} + +int efi_get_boot_order(uint16_t **ret_order) { + _cleanup_free_ void *buf = NULL; + size_t l; + int r; + + assert(ret_order); + + if (!is_efi_boot()) + return -EOPNOTSUPP; + + r = efi_get_variable(EFI_GLOBAL_VARIABLE(BootOrder), NULL, &buf, &l); + if (r < 0) + return r; + + if (l <= 0) + return -ENOENT; + + if (l % sizeof(uint16_t) > 0 || + l / sizeof(uint16_t) > INT_MAX) + return -EINVAL; + + *ret_order = TAKE_PTR(buf); + return (int) (l / sizeof(uint16_t)); +} + +int efi_set_boot_order(const uint16_t *order, size_t n) { + + if (!is_efi_boot()) + return -EOPNOTSUPP; + + return efi_set_variable(EFI_GLOBAL_VARIABLE(BootOrder), order, n * sizeof(uint16_t)); +} + +static int boot_id_hex(const char s[static 4]) { + int id = 0; + + assert(s); + + for (int i = 0; i < 4; i++) + if (s[i] >= '0' && s[i] <= '9') + id |= (s[i] - '0') << (3 - i) * 4; + else if (s[i] >= 'A' && s[i] <= 'F') + id |= (s[i] - 'A' + 10) << (3 - i) * 4; + else + return -EINVAL; + + return id; +} + +int efi_get_boot_options(uint16_t **ret_options) { + _cleanup_closedir_ DIR *dir = NULL; + _cleanup_free_ uint16_t *list = NULL; + int count = 0; + + assert(ret_options); + + if (!is_efi_boot()) + return -EOPNOTSUPP; + + dir = opendir(EFIVAR_PATH(".")); + if (!dir) + return -errno; + + FOREACH_DIRENT(de, dir, return -errno) { + int id; + + if (strncmp(de->d_name, "Boot", 4) != 0) + continue; + + if (strlen(de->d_name) != 45) + continue; + + if (strcmp(de->d_name + 8, EFI_GLOBAL_VARIABLE_STR("")) != 0) /* generate variable suffix using macro */ + continue; + + id = boot_id_hex(de->d_name + 4); + if (id < 0) + continue; + + if (!GREEDY_REALLOC(list, count + 1)) + return -ENOMEM; + + list[count++] = id; + } + + typesafe_qsort(list, count, cmp_uint16); + + *ret_options = TAKE_PTR(list); + + return count; +} + +bool efi_has_tpm2(void) { + static int cache = -1; + + /* Returns whether the system has a TPM2 chip which is known to the EFI firmware. */ + + if (cache >= 0) + return cache; + + /* First, check if we are on an EFI boot at all. */ + if (!is_efi_boot()) { + cache = 0; + return cache; + } + + /* Then, check if the ACPI table "TPM2" exists, which is the TPM2 event log table, see: + * https://trustedcomputinggroup.org/wp-content/uploads/TCG_ACPIGeneralSpecification_v1.20_r8.pdf + * This table exists whenever the firmware is hooked up to TPM2. */ + cache = access("/sys/firmware/acpi/tables/TPM2", F_OK) >= 0; + if (cache) + return cache; + + if (errno != ENOENT) + log_debug_errno(errno, "Unable to test whether /sys/firmware/acpi/tables/TPM2 exists, assuming it doesn't: %m"); + + /* As the last try, check if the EFI firmware provides the EFI_TCG2_FINAL_EVENTS_TABLE + * stored in EFI configuration table, see: + * https://trustedcomputinggroup.org/wp-content/uploads/EFI-Protocol-Specification-rev13-160330final.pdf + */ + cache = access("/sys/kernel/security/tpm0/binary_bios_measurements", F_OK) >= 0; + if (!cache && errno != ENOENT) + log_debug_errno(errno, "Unable to test whether /sys/kernel/security/tpm0/binary_bios_measurements exists, assuming it doesn't: %m"); + + return cache; +} + +#endif + +struct efi_guid { + uint32_t u1; + uint16_t u2; + uint16_t u3; + uint8_t u4[8]; +} _packed_; + +sd_id128_t efi_guid_to_id128(const void *guid) { + const struct efi_guid *uuid = ASSERT_PTR(guid); /* cast is safe, because struct efi_guid is packed */ + sd_id128_t id128; + + id128.bytes[0] = (uuid->u1 >> 24) & 0xff; + id128.bytes[1] = (uuid->u1 >> 16) & 0xff; + id128.bytes[2] = (uuid->u1 >> 8) & 0xff; + id128.bytes[3] = uuid->u1 & 0xff; + + id128.bytes[4] = (uuid->u2 >> 8) & 0xff; + id128.bytes[5] = uuid->u2 & 0xff; + + id128.bytes[6] = (uuid->u3 >> 8) & 0xff; + id128.bytes[7] = uuid->u3 & 0xff; + + memcpy(&id128.bytes[8], uuid->u4, sizeof(uuid->u4)); + + return id128; +} + +void efi_id128_to_guid(sd_id128_t id, void *ret_guid) { + assert(ret_guid); + + struct efi_guid uuid = { + .u1 = id.bytes[0] << 24 | id.bytes[1] << 16 | id.bytes[2] << 8 | id.bytes[3], + .u2 = id.bytes[4] << 8 | id.bytes[5], + .u3 = id.bytes[6] << 8 | id.bytes[7], + }; + memcpy(uuid.u4, id.bytes+8, sizeof(uuid.u4)); + memcpy(ret_guid, &uuid, sizeof(uuid)); +} |