mbirth/gcd-parser
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Detect trailing data (signed firmwares) and print a warning.

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This commit is contained in:
Markus Birth 2019-07-04 23:42:47 +02:00
parent 5ca2f8cad5
commit 7d884a526a
Signed by: mbirth
GPG Key ID: A9928D7A098C3A9A
1 changed files with 16 additions and 3 deletions
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19
grmn/gcd.py
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@ -6,6 +6,7 @@ from .chksum import ChkSum
from .tlv import TLV, TLV6, TLV7, TLVbinary from .tlv import TLV, TLV6, TLV7, TLVbinary
from struct import unpack from struct import unpack
import configparser import configparser
import os
import sys import sys
GCD_SIG = b"G\x41RM\x49Nd\00" GCD_SIG = b"G\x41RM\x49Nd\00"
@ -25,7 +26,10 @@ class Gcd:
def __init__(self, filename: str=None): def __init__(self, filename: str=None):
self.filename = filename self.filename = filename
self.struct = [] self.struct = []
self.is_truncated = False
self.has_trailing = False
if filename is not None: if filename is not None:
self.file_len = os.path.getsize(self.filename)
self.load() self.load()
def load(self): def load(self):
@ -41,6 +45,7 @@ class Gcd:
cur_offset = f.tell() cur_offset = f.tell()
header = f.read(4) header = f.read(4)
if len(header) < 4: if len(header) < 4:
self.is_truncated = True
#raise ParseException("File truncated. End marker not reached yet.") #raise ParseException("File truncated. End marker not reached yet.")
print(RED + "WARNING: File truncated. End marker not reached yet. (pos={})".format(f.tell()) + RESET, file=sys.stderr) print(RED + "WARNING: File truncated. End marker not reached yet. (pos={})".format(f.tell()) + RESET, file=sys.stderr)
break break
@ -48,7 +53,7 @@ class Gcd:
tlv = TLV.factory(type_id, length, offset=cur_offset) tlv = TLV.factory(type_id, length, offset=cur_offset)
self.add_tlv(tlv) self.add_tlv(tlv)
if tlv.type_id == 0xFFFF: if tlv.type_id == 0xFFFF:
# End of file reached # End of TLV structure reached
break break
tlength = tlv.length tlength = tlv.length
payload = f.read(tlength) payload = f.read(tlength)
@ -60,6 +65,10 @@ class Gcd:
last_tlv7 = tlv last_tlv7 = tlv
elif tlv.is_binary: elif tlv.is_binary:
tlv.set_tlv7(last_tlv7) tlv.set_tlv7(last_tlv7)
self.end_offset = f.tell()
self.trailing_bytes = self.file_len - self.end_offset
if (self.trailing_bytes > 0):
self.has_trailing = True
f.close() f.close()
def add_tlv(self, new_tlv: TLV): def add_tlv(self, new_tlv: TLV):
@ -67,7 +76,7 @@ class Gcd:
def print_struct(self): def print_struct(self):
""" """
Prints the structure of the parsed GCD file Prints the structure of the parsed GCD file with compact format for binary data.
""" """
last_tlv = 0xffff last_tlv = 0xffff
tlv_count = 0 tlv_count = 0
@ -84,13 +93,17 @@ class Gcd:
if tlv.length is not None: if tlv.length is not None:
tlv_length += tlv.length tlv_length += tlv.length
last_tlv = tlv.type_id last_tlv = tlv.type_id
if (self.has_trailing):
print(RED + "WARNING: {} trailing Bytes. Probably a signed firmware.".format(self.trailing_bytes) + RESET, file=sys.stderr)
def print_struct_full(self): def print_struct_full(self):
""" """
Prints the structure of the parsed GCD file Prints the detailed structure of the parsed GCD file
""" """
for i, tlv in enumerate(self.struct): for i, tlv in enumerate(self.struct):
print("#{:03d}: {}".format(i, tlv)) print("#{:03d}: {}".format(i, tlv))
if (self.has_trailing):
print(RED + "WARNING: {} trailing Bytes. Probably a signed firmware.".format(self.trailing_bytes) + RESET, file=sys.stderr)
def validate(self, print_stats: bool=False): def validate(self, print_stats: bool=False):
""" """