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#! /usr/bin/env python
# This Source Code Form is subject to the terms of the Mozilla Public
# License, v. 2.0. If a copy of the MPL was not distributed with this file,
# You can obtain one at
from __future__ import absolute_import, print_function
import argparse
import logging
import mmap
import json
import os
import shutil
import struct
import sys
import tempfile
import urllib.parse
logging.basicConfig(level=logging.INFO, format="%(levelname)s - %(message)s")
log = logging.getLogger()
def write_attribution_data(filepath, data):
"""Insert data into a prepared certificate in a signed PE file.
Returns False if the file isn't a valid PE file, or if the necessary
certificate was not found.
This function assumes that somewhere in the given file's certificate table
there exists a 1024-byte space which begins with the tag "__MOZCUSTOM__:".
The given data will be inserted into the file following this tag.
We don't bother updating the optional header checksum.
Windows doesn't check it for executables, only drivers and certain DLL's.
with open(filepath, "r+b") as file:
mapped = mmap.mmap(file.fileno(), 0, access=mmap.ACCESS_WRITE)
# Get the location of the PE header and the optional header
pe_header_offset = struct.unpack("<I", mapped[0x3C:0x40])[0]
optional_header_offset = pe_header_offset + 24
# Look up the magic number in the optional header,
# so we know if we have a 32 or 64-bit executable.
# We need to know that so that we can find the data directories.
pe_magic_number = struct.unpack(
"<H", mapped[optional_header_offset : optional_header_offset + 2]
if pe_magic_number == 0x10B:
# 32-bit
cert_dir_entry_offset = optional_header_offset + 128
elif pe_magic_number == 0x20B:
# 64-bit. Certain header fields are wider.
cert_dir_entry_offset = optional_header_offset + 144
# Not any known PE format
return False
# The certificate table offset and length give us the valid range
# to search through for where we should put our data.
cert_table_offset = struct.unpack(
"<I", mapped[cert_dir_entry_offset : cert_dir_entry_offset + 4]
cert_table_size = struct.unpack(
"<I", mapped[cert_dir_entry_offset + 4 : cert_dir_entry_offset + 8]
if cert_table_offset == 0 or cert_table_size == 0:
# The file isn't signed
return False
tag = b"__MOZCUSTOM__:"
tag_index = mapped.find(
tag, cert_table_offset, cert_table_offset + cert_table_size
if tag_index == -1:
return False
# convert to quoted-url byte-string for insertion
data = urllib.parse.quote(data).encode("utf-8")
mapped[tag_index + len(tag) : tag_index + len(tag) + len(data)] = data
return True
def validate_attribution_code(attribution):"Checking attribution %s" % attribution)
return_code = True
if len(attribution) == 0:
log.error("Attribution code has 0 length")
return False
if len(attribution) > MAX_LENGTH:
log.error("Attribution code longer than %s chars" % MAX_LENGTH)
return_code = False
# this leaves out empty values like 'foo='
params = urllib.parse.parse_qsl(attribution)
used_keys = set()
for key, value in params:
# check for invalid keys
if key not in (
log.error("Invalid key %s" % key)
return_code = False
# avoid ambiguity from repeated keys
if key in used_keys:
log.error("Repeated key %s" % key)
return_code = False
# TODO the service checks for valid source, should we do that here too ?
# some keys are required
for key in ("source", "medium", "campaign", "content"):
if key not in used_keys:
log.error("key '%s' must be set, use '(not set)' if not needed" % key)
return_code = False
return return_code
def main():
parser = argparse.ArgumentParser(
description="Add attribution to Windows installer(s).",
By default, configuration from envvar ATTRIBUTION_CONFIG is used, with
expected format
[{"input": "in/abc.exe", "output": "out/def.exe", "attribution": "abcdef"},
{"input": "in/ghi.exe", "output": "out/jkl.exe", "attribution": "ghijkl"}]
for 1 or more attributions. Or the script arguments may be used for a single attribution.
The attribution code should be a string which is not url-encoded.
parser.add_argument("--input", help="Source installer to attribute a copy of")
parser.add_argument("--output", help="Location to write the attributed installer")
parser.add_argument("--attribution", help="Attribution code")
args = parser.parse_args()
if os.environ.get("ATTRIBUTION_CONFIG"):
work = json.loads(os.environ["ATTRIBUTION_CONFIG"])
elif args.input and args.output and args.attribution:
work = [
"input": args.input,
"output": args.output,
"attribution": args.attribution,
log.error("No configuration found. Set ATTRIBUTION_CONFIG or pass arguments.")
return 1
cached_code_checks = []
for job in work:
if job["attribution"] not in cached_code_checks:
status = validate_attribution_code(job["attribution"])
if status:
log.error("Failed attribution code check")
return 1
with tempfile.TemporaryDirectory() as td:"Attributing installer %s ..." % job["input"])
tf = shutil.copy(job["input"], td)
if write_attribution_data(tf, job["attribution"]):
os.makedirs(os.path.dirname(job["output"]), exist_ok=True)
shutil.move(tf, job["output"])"Wrote %s" % job["output"])
if __name__ == "__main__":