Folders and files

Name		Name	Last commit message	Last commit date
header		header
sample		sample
README.md		README.md
hdec.py		hdec.py

README

Universal Header Decoder

This tool takes one or more descriptions of a binary header and decodes the header of a given file. The main purpose of this tool is for debugging file formats.

Usage

python3 ./hdec.py <file-to-decode> <type> <header description> [<header 2 description> ...]

Header files consist of a line-by-line description of each header field. Each line has the form

Name: Size in bits

Name: Size in bits: display type

Name: Size in bits: display type: condition

Name is displayed as field name
Size in bits determines the field size in bits. It can also be a mathematical expression and can use previously parsed fields (referenced by their name)
display type (optional) defines how the value should be displayed. It is a comma separated list with the following possible types: int, hex, str, bin, intE (int with changed endianness). The default is int, hex, bin if this field is not given.
condition (optional) the field is only considered if the condition is fulfilled. The condition can contain any logical expression and the names of already parsed fields.

Examples

IPv6 Packets

python3 ./hdec.py sample/ipv6_icmpv6 hex header/IPv6 header/ICMPv6

    File: sample/ipv6_icmpv6.txt
    Definition: header/IPv6, header/ICMPv6
    Type: hex
    Version: 6
    TrafficClass: 0x00
    FlowLabel: 0x10000
    Length: 24
    NextHeader: 0x3a 58
    HopLimit: 64
    Source: 0xfe8000000000000002124b0006a0f908
    Destination: 0xfe8000000000000002124b00068a090f
    Type: 128 0x80
    Code: 0 0x00
    Checksum: 0xb924
    Identifier: 0x0000
    Sequence: 0x0000
    Payload: 0x04040404040404040404040404040404

python3 ./hdec.py sample/ipv6_udp hex header/IPv6 header/UDP

    File: sample/ipv6_upd.txt
    Definition: header/IPv6, header/UDP
    Type: hex
    Version: 6
    TrafficClass: 0x00
    FlowLabel: 0x00000
    Length: 16
    NextHeader: 0x11 17
    HopLimit: 64
    Source: 0xfe8000000000000002124b0006a0f908
    Destination: 0xfe8000000000000002124b00068a090f
    SourcePort: 7778 0x1e62
    DestinationPort: 7777 0x1e61
    Length: 16 0x0010
    Checksum: 0xea70
    Payload: 0x0000320000320000

python3 ./hdec.py sample/6lowpan_iphc hex header/IPHC

    File: sample/6lowpan_iphc.txt
    Definition: header/IPHC
    Type: hex
    Start: 0b011
    TF: 0b01 1
    NH: 0b0
    HopLimit: 0b10 2
    CID: 0b0
    SAC: 0b0
    SAM: 0b11 3
    M: 0b0
    DAC: 0b0
    DAM: 0b11 3
    ECN: 0b00 0
    Padding: 0b00
    FlowLabel: 0x10000
    NextHeader: 0x3a 58

Bitmap

python3 ./hdec.py sample/bitmap.bmp raw header/BMP

    File: sample/bitmap.bmp
    Definition: header/BMP
    Type: raw
    Magic: 0x424d BM
    FileSize: 307338
    Zero: 0x00000000
    Position: 138
    HeaderLen: 124
    Width: 320
    Height: 320
    Layers: 1
    Depth: 24
    Compression: 0
    DataLength: 307200
    XPixelMeter: 2835
    YPixelMeter: 2835
    UsedColors: 0
    ImportantColors: 0