TLS: append Log name for CT Log IDs

Show something like "Signed Certificate Timestamp (Google 'Pilot' Log)"
if the Log ID is recognized, or "... (Unknown Log)" otherwise.

Bug: 13372
Change-Id: I1cd373f110d5beb63ee89fb85831ab72cafe03d0
Reviewed-on: https://code.wireshark.org/review/20387
Petri-Dish: Peter Wu <peter@lekensteyn.nl>
Tested-by: Petri Dish Buildbot <buildbot-no-reply@wireshark.org>
Reviewed-by: Peter Wu <peter@lekensteyn.nl>

1 files changed, 92 insertions, 0 deletions

diff --git a/tools/make-tls-ct-logids.py b/tools/make-tls-ct-logids.py
new file mode 100755
index 0000000000..8f70c240a9
--- /dev/null
+++ b/tools/make-tls-ct-logids.py
@@ -0,0 +1,92 @@
+#!/usr/bin/env python
+# 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:
+#
+#   python tools/make-tls-ct-logids.py --update
+#
+
+import argparse
+from base64 import b64decode, b64encode
+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.certificate-transparency.org/known-logs/all_logs_list.json'
+# File to be patched
+SOURCE_FILE = "epan/dissectors/packet-ssl-utils.c"
+
+def escape_c(s):
+    return s.replace('\\', '\\\\').replace('"', '\\"')
+
+def byteshex(b):
+    return "".join("\\x%02x" % b for b in bytearray(b))
+
+def process_json(obj, lastmod):
+    lines = HEADER
+    lines += " * Last-Modified %s, %s entries. */\n" % (lastmod, len(obj["logs"]))
+    lines += "static const bytes_string ct_logids[] = {\n"
+    for entry in obj["logs"]:
+        desc = entry["description"]
+        pubkey_der = b64decode(entry["key"])
+        key_id = sha256(pubkey_der).digest()
+        lines += '    { '
+        lines += '"%s"\n' % byteshex(key_id[:16])
+        lines += '      "%s", %d,\n' % (byteshex(key_id[16:]), len(key_id))
+        lines += '      "%s" },\n' % escape_c(desc)
+    lines += "    { NULL, 0, NULL }\n"
+    lines += "};\n"
+    return lines
+
+def parse_source():
+    """
+    Reads the source file and tries to split it in the parts before, inside and
+    after the block.
+    """
+    begin, block, end = '', '', ''
+    # Stages: 1 (before block), 2 (in block, skip), 3 (after block)
+    stage = 1
+    with open(SOURCE_FILE) as f:
+        for line in f:
+            if line == HEADER:
+                stage = 2   # Begin of block
+            if stage == 1:
+                begin += line
+            elif stage == 2:
+                block += line
+                if line.startswith('}'):
+                    stage = 3   # End of block reached
+            elif stage == 3:
+                end += line
+    if stage != 3:
+        raise RuntimeError("Could not parse file (in stage %d)" % stage)
+    return begin, 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()
+    r = requests.get(CT_JSON_URL)
+    code = process_json(r.json(), lastmod=r.headers['Last-Modified'])
+
+    if args.update:
+        begin, block, end = parse_source()
+        if block == code:
+            print("File is up-to-date")
+        else:
+            with open(SOURCE_FILE, "w") as f:
+                f.write(begin)
+                f.write(code)
+                f.write(end)
+            print("Updated %s" % SOURCE_FILE)
+    else:
+        print(code)
+
+if __name__ == '__main__':
+    main()