/* SPDX-License-Identifier: LGPL-2.1-or-later */ #include #include #include #include "util.h" #include "xbootldr.h" union GptHeaderBuffer { EFI_PARTITION_TABLE_HEADER gpt_header; uint8_t space[CONST_ALIGN_TO(sizeof(EFI_PARTITION_TABLE_HEADER), 512)]; }; static EFI_DEVICE_PATH *path_replace_hd( const EFI_DEVICE_PATH *path, const EFI_DEVICE_PATH *node, const HARDDRIVE_DEVICE_PATH *new_node) { /* Create a new device path as a copy of path, while chopping off the remainder starting at the given * node. If new_node is provided, it is appended at the end of the new path. */ assert(path); assert(node); size_t len = (uint8_t *) node - (uint8_t *) path, new_node_len = 0; if (new_node) new_node_len = DevicePathNodeLength(&new_node->Header); EFI_DEVICE_PATH *ret = xmalloc(len + new_node_len + END_DEVICE_PATH_LENGTH); EFI_DEVICE_PATH *end = mempcpy(ret, path, len); if (new_node) end = mempcpy(end, new_node, new_node_len); SetDevicePathEndNode(end); return ret; } static bool verify_gpt(union GptHeaderBuffer *gpt_header_buffer, EFI_LBA lba_expected) { EFI_PARTITION_TABLE_HEADER *h; uint32_t crc32, crc32_saved; EFI_STATUS err; assert(gpt_header_buffer); h = &gpt_header_buffer->gpt_header; /* Some superficial validation of the GPT header */ if (memcmp(&h->Header.Signature, "EFI PART", sizeof(h->Header.Signature)) != 0) return false; if (h->Header.HeaderSize < 92 || h->Header.HeaderSize > 512) return false; if (h->Header.Revision != 0x00010000U) return false; /* Calculate CRC check */ crc32_saved = h->Header.CRC32; h->Header.CRC32 = 0; err = BS->CalculateCrc32(gpt_header_buffer, h->Header.HeaderSize, &crc32); h->Header.CRC32 = crc32_saved; if (err != EFI_SUCCESS || crc32 != crc32_saved) return false; if (h->MyLBA != lba_expected) return false; if ((h->SizeOfPartitionEntry % sizeof(EFI_PARTITION_ENTRY)) != 0) return false; if (h->NumberOfPartitionEntries <= 0 || h->NumberOfPartitionEntries > 1024) return false; /* overflow check */ if (h->SizeOfPartitionEntry > UINTN_MAX / h->NumberOfPartitionEntries) return false; return true; } static EFI_STATUS try_gpt( EFI_BLOCK_IO_PROTOCOL *block_io, EFI_LBA lba, EFI_LBA *ret_backup_lba, /* May be changed even on error! */ HARDDRIVE_DEVICE_PATH *ret_hd) { _cleanup_free_ EFI_PARTITION_ENTRY *entries = NULL; union GptHeaderBuffer gpt; EFI_STATUS err; uint32_t crc32; UINTN size; assert(block_io); assert(ret_hd); /* Read the GPT header */ err = block_io->ReadBlocks( block_io, block_io->Media->MediaId, lba, sizeof(gpt), &gpt); if (err != EFI_SUCCESS) return err; /* Indicate the location of backup LBA even if the rest of the header is corrupt. */ if (ret_backup_lba) *ret_backup_lba = gpt.gpt_header.AlternateLBA; if (!verify_gpt(&gpt, lba)) return EFI_NOT_FOUND; /* Now load the GPT entry table */ size = ALIGN_TO((UINTN) gpt.gpt_header.SizeOfPartitionEntry * (UINTN) gpt.gpt_header.NumberOfPartitionEntries, 512); entries = xmalloc(size); err = block_io->ReadBlocks( block_io, block_io->Media->MediaId, gpt.gpt_header.PartitionEntryLBA, size, entries); if (err != EFI_SUCCESS) return err; /* Calculate CRC of entries array, too */ err = BS->CalculateCrc32(entries, size, &crc32); if (err != EFI_SUCCESS || crc32 != gpt.gpt_header.PartitionEntryArrayCRC32) return EFI_CRC_ERROR; /* Now we can finally look for xbootloader partitions. */ for (UINTN i = 0; i < gpt.gpt_header.NumberOfPartitionEntries; i++) { EFI_PARTITION_ENTRY *entry = (EFI_PARTITION_ENTRY *) ((uint8_t *) entries + gpt.gpt_header.SizeOfPartitionEntry * i); if (memcmp(&entry->PartitionTypeGUID, XBOOTLDR_GUID, sizeof(entry->PartitionTypeGUID)) != 0) continue; if (entry->EndingLBA < entry->StartingLBA) /* Bogus? */ continue; *ret_hd = (HARDDRIVE_DEVICE_PATH) { .Header = { .Type = MEDIA_DEVICE_PATH, .SubType = MEDIA_HARDDRIVE_DP, }, .PartitionNumber = i + 1, .PartitionStart = entry->StartingLBA, .PartitionSize = entry->EndingLBA - entry->StartingLBA + 1, .MBRType = MBR_TYPE_EFI_PARTITION_TABLE_HEADER, .SignatureType = SIGNATURE_TYPE_GUID, }; memcpy(ret_hd->Signature, &entry->UniquePartitionGUID, sizeof(ret_hd->Signature)); /* HARDDRIVE_DEVICE_PATH has padding, which at least OVMF does not like. */ SetDevicePathNodeLength( &ret_hd->Header, offsetof(HARDDRIVE_DEVICE_PATH, SignatureType) + sizeof(ret_hd->SignatureType)); return EFI_SUCCESS; } /* This GPT was fully valid, but we didn't find what we are looking for. This * means there's no reason to check the second copy of the GPT header */ return EFI_NOT_FOUND; } static EFI_STATUS find_device(EFI_HANDLE *device, EFI_DEVICE_PATH **ret_device_path) { EFI_STATUS err; assert(device); assert(ret_device_path); EFI_DEVICE_PATH *partition_path; err = BS->HandleProtocol(device, &DevicePathProtocol, (void **) &partition_path); if (err != EFI_SUCCESS) return err; /* Find the (last) partition node itself. */ EFI_DEVICE_PATH *part_node = NULL; for (EFI_DEVICE_PATH *node = partition_path; !IsDevicePathEnd(node); node = NextDevicePathNode(node)) { if (DevicePathType(node) != MEDIA_DEVICE_PATH) continue; if (DevicePathSubType(node) != MEDIA_HARDDRIVE_DP) continue; part_node = node; } if (!part_node) return EFI_NOT_FOUND; /* Chop off the partition part, leaving us with the full path to the disk itself. */ _cleanup_free_ EFI_DEVICE_PATH *disk_path = NULL; EFI_DEVICE_PATH *p = disk_path = path_replace_hd(partition_path, part_node, NULL); EFI_HANDLE disk_handle; EFI_BLOCK_IO_PROTOCOL *block_io; err = BS->LocateDevicePath(&BlockIoProtocol, &p, &disk_handle); if (err != EFI_SUCCESS) return err; /* The drivers for other partitions on this drive may not be initialized on fastboot firmware, so we * have to ask the firmware to do just that. */ (void) BS->ConnectController(disk_handle, NULL, NULL, true); err = BS->HandleProtocol(disk_handle, &BlockIoProtocol, (void **)&block_io); if (err != EFI_SUCCESS) return err; /* Filter out some block devices early. (We only care about block devices that aren't * partitions themselves — we look for GPT partition tables to parse after all —, and only * those which contain a medium and have at least 2 blocks.) */ if (block_io->Media->LogicalPartition || !block_io->Media->MediaPresent || block_io->Media->LastBlock <= 1) return EFI_NOT_FOUND; /* Try several copies of the GPT header, in case one is corrupted */ EFI_LBA backup_lba = 0; for (UINTN nr = 0; nr < 3; nr++) { EFI_LBA lba; /* Read the first copy at LBA 1 and then try the backup GPT header pointed * to by the first header if that one was corrupted. As a last resort, * try the very last LBA of this block device. */ if (nr == 0) lba = 1; else if (nr == 1 && backup_lba != 0) lba = backup_lba; else if (nr == 2 && backup_lba != block_io->Media->LastBlock) lba = block_io->Media->LastBlock; else continue; HARDDRIVE_DEVICE_PATH hd; err = try_gpt( block_io, lba, nr == 0 ? &backup_lba : NULL, /* Only get backup LBA location from first GPT header. */ &hd); if (err != EFI_SUCCESS) { /* GPT was valid but no XBOOT loader partition found. */ if (err == EFI_NOT_FOUND) break; /* Bad GPT, try next one. */ continue; } /* Patch in the data we found */ *ret_device_path = path_replace_hd(partition_path, part_node, &hd); return EFI_SUCCESS; } /* No xbootloader partition found */ return EFI_NOT_FOUND; } EFI_STATUS xbootldr_open(EFI_HANDLE *device, EFI_HANDLE *ret_device, EFI_FILE **ret_root_dir) { _cleanup_free_ EFI_DEVICE_PATH *partition_path = NULL; EFI_HANDLE new_device; EFI_FILE *root_dir; EFI_STATUS err; assert(device); assert(ret_device); assert(ret_root_dir); err = find_device(device, &partition_path); if (err != EFI_SUCCESS) return err; EFI_DEVICE_PATH *dp = partition_path; err = BS->LocateDevicePath(&BlockIoProtocol, &dp, &new_device); if (err != EFI_SUCCESS) return err; err = open_volume(new_device, &root_dir); if (err != EFI_SUCCESS) return err; *ret_device = new_device; *ret_root_dir = root_dir; return EFI_SUCCESS; }