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1.1 root 1: ; 1.1.1.9 ! root 2: ; Copyright (c) 2008-2009 TrueCrypt Developers Association. All rights reserved. 1.1 root 3: ; 1.1.1.9 ! root 4: ; Governed by the TrueCrypt License 2.8 the full text of which is contained in ! 5: ; the file License.txt included in TrueCrypt binary and source code distribution ! 6: ; packages. 1.1 root 7: ; 8: 9: .MODEL tiny 10: .386 1.1.1.3 root 11: _TEXT SEGMENT USE16 1.1 root 12: 13: INCLUDE BootDefs.i 14: 1.1.1.3 root 15: ORG 7C00h ; Standard boot sector offset 1.1 root 16: 17: start: 18: ; BIOS executes boot sector from 0:7C00 or 7C0:0000 (default CD boot loader address). 1.1.1.3 root 19: ; Far jump to the next instruction sets IP to the standard offset 7C00. 1.1 root 20: db 0EAh ; jmp 0:main 21: dw main, 0 22: 1.1.1.3 root 23: loader_name_msg: 24: db ' TrueCrypt Boot Loader', 13, 10, 0 1.1 root 25: 1.1.1.6 root 26: main: 27: cli 1.1.1.2 root 28: xor ax, ax 1.1 root 29: mov ds, ax 1.1.1.6 root 30: mov ss, ax 31: mov sp, 7C00h 32: sti 33: 1.1.1.5 root 34: ; Display boot loader name 35: test byte ptr [start + TC_BOOT_SECTOR_USER_CONFIG_OFFSET], TC_BOOT_USER_CFG_FLAG_SILENT_MODE 36: jnz skip_loader_name_msg 37: 1.1.1.3 root 38: lea si, loader_name_msg 1.1 root 39: call print 1.1.1.5 root 40: skip_loader_name_msg: 41: 1.1.1.6 root 42: ; Determine boot loader segment 1.1 root 43: mov ax, TC_BOOT_LOADER_SEGMENT 44: 45: ; Check available memory 1.1.1.2 root 46: cmp word ptr [ds:413h], TC_BOOT_LOADER_SEGMENT / 1024 * 16 + TC_BOOT_MEMORY_REQUIRED 1.1.1.3 root 47: jge memory_ok 1.1 root 48: 1.1.1.6 root 49: mov ax, TC_BOOT_LOADER_SEGMENT_LOW 50: 51: cmp word ptr [ds:413h], TC_BOOT_LOADER_SEGMENT_LOW / 1024 * 16 + TC_BOOT_MEMORY_REQUIRED 52: jge memory_ok 53: 1.1 root 54: ; Insufficient memory 55: mov ax, TC_BOOT_LOADER_LOWMEM_SEGMENT 1.1.1.6 root 56: 1.1.1.3 root 57: memory_ok: 1.1.1.6 root 58: mov es, ax 1.1 root 59: 1.1.1.3 root 60: ; Clear BSS section 1.1 root 61: xor al, al 1.1.1.3 root 62: mov di, TC_COM_EXECUTABLE_OFFSET 63: mov cx, TC_BOOT_MEMORY_REQUIRED * 1024 - TC_COM_EXECUTABLE_OFFSET - 1 1.1.1.2 root 64: cld 1.1 root 65: rep stosb 66: 1.1.1.3 root 67: mov ax, es 68: sub ax, TC_BOOT_LOADER_DECOMPRESSOR_MEMORY_SIZE / 16 ; Decompressor segment 69: mov es, ax 70: 71: ; Load decompressor 72: mov cl, TC_BOOT_LOADER_DECOMPRESSOR_START_SECTOR 73: retry_backup: 74: mov al, TC_BOOT_LOADER_DECOMPRESSOR_SECTOR_COUNT 75: mov bx, TC_COM_EXECUTABLE_OFFSET 76: call read_sectors 77: 78: ; Decompressor checksum 79: xor ebx, ebx 80: mov si, TC_COM_EXECUTABLE_OFFSET 81: mov cx, TC_BOOT_LOADER_DECOMPRESSOR_SECTOR_COUNT * TC_LB_SIZE 82: call checksum 83: push ebx 84: 85: ; Load compressed boot loader 86: mov bx, TC_BOOT_LOADER_COMPRESSED_BUFFER_OFFSET 87: mov cl, TC_BOOT_LOADER_START_SECTOR 88: mov al, TC_MAX_BOOT_LOADER_SECTOR_COUNT 89: 90: test backup_loader_used, 1 91: jz non_backup 92: mov al, TC_BOOT_LOADER_BACKUP_SECTOR_COUNT - TC_BOOT_LOADER_DECOMPRESSOR_SECTOR_COUNT 93: mov cl, TC_BOOT_LOADER_START_SECTOR + TC_BOOT_LOADER_BACKUP_SECTOR_COUNT 94: 95: non_backup: 96: call read_sectors 97: 98: ; Boot loader checksum 99: pop ebx 100: mov si, TC_BOOT_LOADER_COMPRESSED_BUFFER_OFFSET 101: mov cx, word ptr [start + TC_BOOT_SECTOR_LOADER_LENGTH_OFFSET] 102: call checksum 103: 104: ; Verify checksum 105: cmp ebx, dword ptr [start + TC_BOOT_SECTOR_LOADER_CHECKSUM_OFFSET] 106: je checksum_ok 107: 108: ; Checksum incorrect - try using backup if available 109: test backup_loader_used, 1 110: jnz loader_damaged 111: 112: mov backup_loader_used, 1 113: mov cl, TC_BOOT_LOADER_DECOMPRESSOR_START_SECTOR + TC_BOOT_LOADER_BACKUP_SECTOR_COUNT 1.1 root 114: 1.1.1.3 root 115: test TC_BOOT_CFG_FLAG_BACKUP_LOADER_AVAILABLE, byte ptr [start + TC_BOOT_SECTOR_CONFIG_OFFSET] 116: jnz retry_backup 117: 118: loader_damaged: 119: lea si, loader_damaged_msg 120: call print 121: lea si, loader_name_msg 122: call print 1.1 root 123: jmp $ 1.1.1.3 root 124: checksum_ok: 125: 126: ; Set up decompressor segment 127: mov ax, es 128: mov ds, ax 129: cli 130: mov ss, ax 131: mov sp, TC_BOOT_LOADER_DECOMPRESSOR_MEMORY_SIZE 132: sti 1.1 root 133: 1.1.1.3 root 134: push dx 135: 136: ; Decompress boot loader 137: push TC_BOOT_LOADER_COMPRESSED_BUFFER_OFFSET + TC_GZIP_HEADER_SIZE ; Compressed data 138: push TC_MAX_BOOT_LOADER_DECOMPRESSED_SIZE ; Output buffer size 139: push TC_BOOT_LOADER_DECOMPRESSOR_MEMORY_SIZE + TC_COM_EXECUTABLE_OFFSET ; Output buffer 140: 1.1.1.6 root 141: push cs 142: push decompressor_ret 143: push es 144: push TC_COM_EXECUTABLE_OFFSET 145: retf 146: decompressor_ret: 1.1.1.3 root 147: 148: add sp, 6 149: pop dx 150: 151: ; Restore boot sector segment 1.1.1.6 root 152: push cs 153: pop ds 1.1.1.3 root 154: 155: ; Check decompression result 156: test ax, ax 157: jz decompression_ok 158: 1.1.1.6 root 159: lea si, loader_damaged_msg 1.1.1.3 root 160: call print 161: jmp $ 162: decompression_ok: 1.1 root 163: 164: ; DH = boot sector flags 165: mov dh, byte ptr [start + TC_BOOT_SECTOR_CONFIG_OFFSET] 166: 1.1.1.3 root 167: ; Set up boot loader segment 1.1 root 168: mov ax, es 1.1.1.3 root 169: add ax, TC_BOOT_LOADER_DECOMPRESSOR_MEMORY_SIZE / 16 170: mov es, ax 1.1 root 171: mov ds, ax 172: cli 173: mov ss, ax 1.1.1.3 root 174: mov sp, TC_BOOT_LOADER_STACK_TOP 1.1 root 175: sti 176: 1.1.1.3 root 177: ; Execute boot loader 178: push es 179: push TC_COM_EXECUTABLE_OFFSET 180: retf 181: 1.1 root 182: ; Print string 183: print: 184: xor bx, bx 185: mov ah, 0eh 1.1.1.3 root 186: cld 1.1 root 187: 188: @@: lodsb 189: test al, al 190: jz print_end 191: 192: int 10h 193: jmp @B 194: 195: print_end: 196: ret 1.1.1.3 root 197: 198: ; Read sectors of the first cylinder 199: read_sectors: 200: mov ch, 0 ; Cylinder 201: mov dh, 0 ; Head 202: ; DL = drive number passed from BIOS 203: mov ah, 2 204: int 13h 205: jnc read_ok 206: 207: lea si, disk_error_msg 208: call print 209: read_ok: 210: ret 211: 212: ; Calculate checksum 213: checksum: 214: push ds 215: push es 216: pop ds 217: xor eax, eax 218: cld 219: 220: @@: lodsb 221: add ebx, eax 222: rol ebx, 1 223: loop @B 224: 225: pop ds 226: ret 227: 228: backup_loader_used db 0 1.1 root 229: 1.1.1.3 root 230: disk_error_msg db 'Disk error', 13, 10, 7, 0 1.1.1.6 root 231: loader_damaged_msg db 7, 'Loader damaged! Use Rescue Disk: Repair Options > Restore', 0 1.1 root 232: 1.1.1.8 root 233: ORG 7C00h + 510 234: dw 0AA55h ; Boot sector signature 1.1 root 235: 236: _TEXT ENDS 237: END start
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