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#!/usr/bin/env python3
# Generate the array of Certificate Transparency Log ID to description mappings
# for the TLS dissector.
#
# To update the TLS dissector source file, run this from the source directory:
#
# python3 tools/make-tls-ct-logids.py --update
#
import argparse
from base64 import b64decode, b64encode
from enum import Enum
import itertools
import os
import requests
from hashlib import sha256
# Begin of comment, followed by the actual array definition
HEADER = "/* Generated by tools/make-tls-ct-logids.py\n"
# See also https://www.certificate-transparency.org/known-logs
CT_JSON_URL = 'https://www.gstatic.com/ct/log_list/v3/all_logs_list.json'
# File to be patched
SOURCE_FILE = os.path.join('epan', 'dissectors', 'packet-tls-utils.c')
# Maximum elements per line in the value array. 11 is chosen because it results
# in output consistent with clang-format.
BYTES_PER_LINE = 11
class SourceStage(Enum):
BEGIN = 1
IN_METAINFO = 2
IN_BLOCK = 3
END = 4
def escape_c(s):
return s.replace('\\', '\\\\').replace('"', '\\"')
def byteshex(b):
return " ".join("0x%02x," % b for b in bytearray(b))
def process_json(obj, lastmod):
logs = list(itertools.chain(*[op['logs'] for op in obj['operators']]))
metainfo, block = HEADER, ''
metainfo += " * Last-Modified %s, %s entries. */\n" % (lastmod, len(logs))
block += "static const bytes_string ct_logids[] = {\n"
for entry in logs:
desc = entry["description"]
pubkey_der = b64decode(entry["key"])
key_id = sha256(pubkey_der).digest()
block += ' { (const uint8_t[]){\n'
for offset in range(0, len(key_id), BYTES_PER_LINE):
block += ' %s\n' % \
byteshex(key_id[offset:offset+BYTES_PER_LINE])
block += ' },\n'
block += ' %d, "%s" },\n' % (len(key_id), escape_c(desc))
block += " { NULL, 0, NULL }\n"
block += "};\n"
return metainfo, block
def parse_source(source_path):
"""
Reads the source file and tries to split it in the parts before, inside and
after the block.
"""
begin, metainfo, block, end = '', '', '', ''
# Stages: BEGIN (before block), IN_METAINFO, IN_BLOCK (skip), END
stage = SourceStage.BEGIN
with open(source_path) as f:
for line in f:
if line.startswith('/* Generated by '):
stage = SourceStage.IN_METAINFO
if stage == SourceStage.BEGIN:
begin += line
elif stage == SourceStage.IN_METAINFO:
metainfo += line
elif stage == SourceStage.IN_BLOCK:
block += line
if line.startswith('}'):
stage = SourceStage.END
elif stage == SourceStage.END:
end += line
if line.startswith(' * Last-Modified '):
stage = SourceStage.IN_BLOCK
if stage != SourceStage.END:
raise RuntimeError("Could not parse file (in stage %s)" % stage.name)
return begin, metainfo, block, end
parser = argparse.ArgumentParser()
parser.add_argument("--update", action="store_true",
help="Update %s as needed instead of writing to stdout" % SOURCE_FILE)
def main():
args = parser.parse_args()
this_dir = os.path.dirname(__file__)
r = requests.get(CT_JSON_URL)
j_metainfo, j_block = process_json(r.json(), lastmod=r.headers['Last-Modified'])
source_path = os.path.join(this_dir, '..', SOURCE_FILE)
if args.update:
s_begin, _, s_block, s_end = parse_source(source_path)
if s_block == j_block:
print("File is up-to-date")
else:
with open(source_path, "w") as f:
f.write(s_begin)
f.write(j_metainfo)
f.write(j_block)
f.write(s_end)
print("Updated %s" % source_path)
else:
print(j_metainfo, j_block)
if __name__ == '__main__':
main()
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