.trx file format is widely used for distribution of firmware updates for Broadcom devices. The most well-known are ASUS routers.
Fundamentally, it includes a footer which acts as a safeguard against installing a firmware package on a wrong hardware model or version, and a header which list numerous partitions packaged inside a single .trx file.
trx files not necessarily contain all these headers.
This page hosts a formal specification of Broadcom devices .trx firmware packaging using Kaitai Struct. This specification can be automatically translated into a variety of programming languages to get a parsing library.
All parsing code for Python generated by Kaitai Struct depends on the Python runtime library. You have to install it before you can parse data.
The Python runtime library can be installed from PyPI:
python3 -m pip install kaitaistructParse a local file and get structure in memory:
data = BroadcomTrx.from_file("path/to/local/file.trx")
Or parse structure from a bytes:
from kaitaistruct import KaitaiStream, BytesIO
raw = b"\x00\x01\x02..."
data = BroadcomTrx(KaitaiStream(BytesIO(raw)))
After that, one can get various attributes from the structure by invoking getter methods like:
data.header # => get header
# This is a generated file! Please edit source .ksy file and use kaitai-struct-compiler to rebuild
import kaitaistruct
from kaitaistruct import KaitaiStruct, KaitaiStream, BytesIO
if getattr(kaitaistruct, 'API_VERSION', (0, 9)) < (0, 9):
raise Exception("Incompatible Kaitai Struct Python API: 0.9 or later is required, but you have %s" % (kaitaistruct.__version__))
class BroadcomTrx(KaitaiStruct):
""".trx file format is widely used for distribution of firmware
updates for Broadcom devices. The most well-known are ASUS routers.
Fundamentally, it includes a footer which acts as a safeguard
against installing a firmware package on a wrong hardware model or
version, and a header which list numerous partitions packaged inside
a single .trx file.
trx files not necessarily contain all these headers.
.. seealso::
Source - https://github.com/openwrt/firmware-utils/blob/a2c80c5/src/trx.c
.. seealso::
Source - https://web.archive.org/web/20190127154419/https://openwrt.org/docs/techref/header
.. seealso::
Source - https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/Documentation/devicetree/bindings/mtd/partitions/brcm,trx.txt
"""
def __init__(self, _io, _parent=None, _root=None):
self._io = _io
self._parent = _parent
self._root = _root if _root else self
self._read()
def _read(self):
pass
class Revision(KaitaiStruct):
def __init__(self, _io, _parent=None, _root=None):
self._io = _io
self._parent = _parent
self._root = _root if _root else self
self._read()
def _read(self):
self.major = self._io.read_u1()
self.minor = self._io.read_u1()
class Version(KaitaiStruct):
def __init__(self, _io, _parent=None, _root=None):
self._io = _io
self._parent = _parent
self._root = _root if _root else self
self._read()
def _read(self):
self.major = self._io.read_u1()
self.minor = self._io.read_u1()
self.patch = self._io.read_u1()
self.tweak = self._io.read_u1()
class Tail(KaitaiStruct):
"""A safeguard against installation of firmware to an incompatible device."""
def __init__(self, _io, _parent=None, _root=None):
self._io = _io
self._parent = _parent
self._root = _root if _root else self
self._read()
def _read(self):
self.version = BroadcomTrx.Version(self._io, self, self._root)
self.product_id = (KaitaiStream.bytes_terminate(self._io.read_bytes(12), 0, False)).decode(u"utf-8")
self.comp_hw = []
for i in range(4):
self.comp_hw.append(BroadcomTrx.Tail.HwCompInfo(self._io, self, self._root))
self.reserved = self._io.read_bytes(32)
class HwCompInfo(KaitaiStruct):
def __init__(self, _io, _parent=None, _root=None):
self._io = _io
self._parent = _parent
self._root = _root if _root else self
self._read()
def _read(self):
self.min = BroadcomTrx.Revision(self._io, self, self._root)
self.max = BroadcomTrx.Revision(self._io, self, self._root)
class Header(KaitaiStruct):
def __init__(self, _io, _parent=None, _root=None):
self._io = _io
self._parent = _parent
self._root = _root if _root else self
self._read()
def _read(self):
self.magic = self._io.read_bytes(4)
if not self.magic == b"\x48\x44\x52\x30":
raise kaitaistruct.ValidationNotEqualError(b"\x48\x44\x52\x30", self.magic, self._io, u"/types/header/seq/0")
self.len = self._io.read_u4le()
self.crc32 = self._io.read_u4le()
self.version = self._io.read_u2le()
self.flags = BroadcomTrx.Header.Flags(self._io, self, self._root)
self.partitions = []
i = 0
while True:
_ = BroadcomTrx.Header.Partition(i, self._io, self, self._root)
self.partitions.append(_)
if ((i >= 4) or (not (_.is_present))) :
break
i += 1
class Partition(KaitaiStruct):
def __init__(self, idx, _io, _parent=None, _root=None):
self._io = _io
self._parent = _parent
self._root = _root if _root else self
self.idx = idx
self._read()
def _read(self):
self.ofs_body = self._io.read_u4le()
@property
def is_present(self):
if hasattr(self, '_m_is_present'):
return self._m_is_present
self._m_is_present = self.ofs_body != 0
return getattr(self, '_m_is_present', None)
@property
def is_last(self):
if hasattr(self, '_m_is_last'):
return self._m_is_last
if self.is_present:
self._m_is_last = ((self.idx == (len(self._parent.partitions) - 1)) or (not (self._parent.partitions[(self.idx + 1)].is_present)))
return getattr(self, '_m_is_last', None)
@property
def len_body(self):
if hasattr(self, '_m_len_body'):
return self._m_len_body
if self.is_present:
self._m_len_body = ((self._root._io.size() - self.ofs_body) if self.is_last else self._parent.partitions[(self.idx + 1)].ofs_body)
return getattr(self, '_m_len_body', None)
@property
def body(self):
if hasattr(self, '_m_body'):
return self._m_body
if self.is_present:
io = self._root._io
_pos = io.pos()
io.seek(self.ofs_body)
self._m_body = io.read_bytes(self.len_body)
io.seek(_pos)
return getattr(self, '_m_body', None)
class Flags(KaitaiStruct):
def __init__(self, _io, _parent=None, _root=None):
self._io = _io
self._parent = _parent
self._root = _root if _root else self
self._read()
def _read(self):
self.flags = []
for i in range(16):
self.flags.append(self._io.read_bits_int_le(1) != 0)
@property
def header(self):
if hasattr(self, '_m_header'):
return self._m_header
_pos = self._io.pos()
self._io.seek(0)
self._m_header = BroadcomTrx.Header(self._io, self, self._root)
self._io.seek(_pos)
return getattr(self, '_m_header', None)
@property
def tail(self):
if hasattr(self, '_m_tail'):
return self._m_tail
_pos = self._io.pos()
self._io.seek((self._io.size() - 64))
self._m_tail = BroadcomTrx.Tail(self._io, self, self._root)
self._io.seek(_pos)
return getattr(self, '_m_tail', None)