#!/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 http://mozilla.org/MPL/2.0/.

"""
Parses a JSON file listing the known Certificate Transparency logs
(log_list.json) and generates a C++ header file to be included in Firefox.

The current log_list.json file available under security/manager/tools
was originally downloaded from
https://www.certificate-transparency.org/known-logs
and edited to include the disqualification time for the disqualified logs using
https://cs.chromium.org/chromium/src/net/cert/ct_known_logs_static-inc.h
"""

import argparse
import base64
import datetime
import json
import os.path
import sys
import textwrap
from string import Template

import six
import urllib3


def decodebytes(s):
    if six.PY3:
        return base64.decodebytes(six.ensure_binary(s))
    return base64.decodestring(s)


OUTPUT_TEMPLATE = """\
/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
/* vim: set ts=8 sts=2 et sw=2 tw=80: */
/* 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 http://mozilla.org/MPL/2.0/. */

/* This file was automatically generated by $prog. */

#ifndef $include_guard
#define $include_guard

#include "CTLog.h"

#include <stddef.h>

struct CTLogInfo
{
  // See bug 1338873 about making these fields const.
  const char* name;
  // Index within kCTLogOperatorList.
  mozilla::ct::CTLogStatus status;
  // 0 for qualified logs, disqualification time for disqualified logs
  // (in milliseconds, measured since the epoch, ignoring leap seconds).
  uint64_t disqualificationTime;
  size_t operatorIndex;
  const char* key;
  size_t keyLength;
};

struct CTLogOperatorInfo
{
  // See bug 1338873 about making these fields const.
  const char* name;
  mozilla::ct::CTLogOperatorId id;
};

const CTLogInfo kCTLogList[] = {
$logs
};

const CTLogOperatorInfo kCTLogOperatorList[] = {
$operators
};

#endif // $include_guard
"""


def get_disqualification_time(time_str):
    """
    Convert a time string such as "2017-01-01T00:00:00Z" to an integer
    representing milliseconds since the epoch.
    Timezones in the string are not supported and will result in an exception.
    """
    t = datetime.datetime.strptime(time_str, "%Y-%m-%dT%H:%M:%SZ")
    epoch = datetime.datetime.utcfromtimestamp(0)
    seconds_since_epoch = (t - epoch).total_seconds()
    return int(seconds_since_epoch * 1000)


def get_hex_lines(blob, width):
    """Convert a binary string to a multiline text of C escape sequences."""
    text = "".join(["\\x{:02x}".format(c) for c in blob])
    # When escaped, a single byte takes 4 chars (e.g. "\x00").
    # Make sure we don't break an escaped byte between the lines.
    return textwrap.wrap(text, width - width % 4)


def get_operator_index(json_data, target_name):
    """Return operator's entry from the JSON along with its array index."""
    matches = [
        (operator, index)
        for (index, operator) in enumerate(json_data["operators"])
        if operator["name"] == target_name
    ]
    assert len(matches) != 0, "No operators with id {0} defined.".format(target_name)
    assert len(matches) == 1, "Found multiple operators with id {0}.".format(
        target_name
    )
    return matches[0][1]


def get_log_info_structs(json_data):
    """Return array of CTLogInfo initializers for the known logs."""
    tmpl = Template(
        textwrap.dedent(
            """\
          { $description,
            $status,
            $disqualification_time, // $disqualification_time_comment
            $operator_index, // $operator_comment
        $indented_log_key,
            $log_key_len }"""
        )
    )
    initializers = []
    for operator in json_data["operators"]:
        operator_name = operator["name"]
        for log in operator["logs"]:
            log_key = decodebytes(log["key"])
            operator_index = get_operator_index(json_data, operator_name)
            if "disqualification_time" in log:
                status = "mozilla::ct::CTLogStatus::Disqualified"
                disqualification_time = get_disqualification_time(
                    log["disqualification_time"]
                )
                disqualification_time_comment = 'Date.parse("{0}")'.format(
                    log["disqualification_time"]
                )
            else:
                status = "mozilla::ct::CTLogStatus::Included"
                disqualification_time = 0
                disqualification_time_comment = "no disqualification time"
            is_test_log = "test_only" in operator and operator["test_only"]
            prefix = ""
            suffix = ","
            if is_test_log:
                prefix = "#ifdef DEBUG\n"
                suffix = ",\n#endif // DEBUG"
            toappend = tmpl.substitute(
                # Use json.dumps for C-escaping strings.
                # Not perfect but close enough.
                description=json.dumps(log["description"]),
                operator_index=operator_index,
                operator_comment="operated by {0}".
                # The comment must not contain "/".
                format(operator_name).replace("/", "|"),
                status=status,
                disqualification_time=disqualification_time,
                disqualification_time_comment=disqualification_time_comment,
                # Maximum line width is 80.
                indented_log_key="\n".join(
                    ['    "{0}"'.format(l) for l in get_hex_lines(log_key, 74)]
                ),
                log_key_len=len(log_key),
            )
            initializers.append(prefix + toappend + suffix)
    return initializers


def get_log_operator_structs(json_data):
    """Return array of CTLogOperatorInfo initializers."""
    tmpl = Template("  { $name, $id }")
    initializers = []
    currentId = 0
    for operator in json_data["operators"]:
        prefix = ""
        suffix = ","
        is_test_log = "test_only" in operator and operator["test_only"]
        if is_test_log:
            prefix = "#ifdef DEBUG\n"
            suffix = ",\n#endif // DEBUG"
        toappend = tmpl.substitute(name=json.dumps(operator["name"]), id=currentId)
        currentId += 1
        initializers.append(prefix + toappend + suffix)
    return initializers


def generate_cpp_header_file(json_data, out_file):
    """Generate the C++ header file for the known logs."""
    filename = os.path.basename(out_file.name)
    include_guard = filename.replace(".", "_").replace("/", "_")
    log_info_initializers = get_log_info_structs(json_data)
    operator_info_initializers = get_log_operator_structs(json_data)
    out_file.write(
        Template(OUTPUT_TEMPLATE).substitute(
            prog=os.path.basename(sys.argv[0]),
            include_guard=include_guard,
            logs="\n".join(log_info_initializers),
            operators="\n".join(operator_info_initializers),
        )
    )


def patch_in_test_logs(json_data):
    """Insert Mozilla-specific test log data."""
    max_id = len(json_data["operators"])
    mozilla_test_operator_1 = {
        "name": "Mozilla Test Org 1",
        "id": max_id + 1,
        "test_only": True,
        "logs": [
            {
                "description": "Mozilla Test RSA Log 1",
                # `openssl x509 -noout -pubkey -in <path/to/default-ee.pem>`
                "key": """
            MIIBIjANBgkqhkiG9w0BAQEFAAOCAQ8AMIIBCgKCAQEAuohRqESOFtZB/W62iAY2
            ED08E9nq5DVKtOz1aFdsJHvBxyWo4NgfvbGcBptuGobya+KvWnVramRxCHqlWqdF
            h/cc1SScAn7NQ/weadA4ICmTqyDDSeTbuUzCa2wO7RWCD/F+rWkasdMCOosqQe6n
            cOAPDY39ZgsrsCSSpH25iGF5kLFXkD3SO8XguEgfqDfTiEPvJxbYVbdmWqp+ApAv
            OnsQgAYkzBxsl62WYVu34pYSwHUxowyR3bTK9/ytHSXTCe+5Fw6naOGzey8ib2nj
            tIqVYR3uJtYlnauRCE42yxwkBCy/Fosv5fGPmRcxuLP+SSP6clHEMdUDrNoYCjXt
            jQIDAQAB
        """,
                "operated_by": [max_id + 1],
            },
            {
                "description": "Mozilla Test EC Log",
                # `openssl x509 -noout -pubkey -in <path/to/root_secp256r1_256.pem`
                "key": """
            MFkwEwYHKoZIzj0CAQYIKoZIzj0DAQcDQgAET7+7u2Hg+PmxpgpZrIcE4uwFC0I+
            PPcukj8sT3lLRVwqadIzRWw2xBGdBwbgDu3I0ZOQ15kbey0HowTqoEqmwA==
        """,
                "operated_by": [max_id + 1],
            },
        ],
    }
    mozilla_test_operator_2 = {
        "name": "Mozilla Test Org 2",
        "id": max_id + 2,
        "test_only": True,
        "logs": [
            {
                "description": "Mozilla Test RSA Log 2",
                # `openssl x509 -noout -pubkey -in <path/to/other-test-ca.pem>`
                "key": """
            MIIBIjANBgkqhkiG9w0BAQEFAAOCAQ8AMIIBCgKCAQEAwXXGUmYJn3cIKmeR8bh2
            w39c5TiwbErNIrHL1G+mWtoq3UHIwkmKxKOzwfYUh/QbaYlBvYClHDwSAkTFhKTE
            SDMF5ROMAQbPCL6ahidguuai6PNvI8XZgxO53683g0XazlHU1tzSpss8xwbrzTBw
            7JjM5AqlkdcpWn9xxb5maR0rLf7ISURZC8Wj6kn9k7HXU0BfF3N2mZWGZiVHl+1C
            aQiICBFCIGmYikP+5Izmh4HdIramnNKDdRMfkysSjOKG+n0lHAYq0n7wFvGHzdVO
            gys1uJMPdLqQqovHYWckKrH9bWIUDRjEwLjGj8N0hFcyStfehuZVLx0eGR1xIWjT
            uwIDAQAB
        """,
                "operated_by": [max_id + 2],
            }
        ],
    }
    json_data["operators"].append(mozilla_test_operator_1)
    json_data["operators"].append(mozilla_test_operator_2)


def run(args):
    """
    Load the input JSON file and generate the C++ header according to the
    command line arguments.
    """
    if args.file:
        print("Reading file: ", args.file)
        with open(args.file, "rb") as json_file:
            json_text = json_file.read()
    elif args.url:
        print("Fetching URL: ", args.url)
        json_request = urllib3.urlopen(args.url)
        try:
            json_text = json_request.read()
        finally:
            json_request.close()

    json_data = json.loads(json_text)

    print("Writing output: ", args.out)

    patch_in_test_logs(json_data)

    with open(args.out, "w") as out_file:
        generate_cpp_header_file(json_data, out_file)

    print("Done.")


def parse_arguments_and_run():
    """Parse the command line arguments and run the program."""
    arg_parser = argparse.ArgumentParser(
        description="Parses a JSON file listing the known "
        "Certificate Transparency logs and generates "
        "a C++ header file to be included in Firefox.",
        epilog="Example: python %s --url" % os.path.basename(sys.argv[0]),
    )

    source_group = arg_parser.add_mutually_exclusive_group(required=True)
    source_group.add_argument(
        "--file",
        nargs="?",
        const="log_list.json",
        help="Read the known CT logs JSON data from the "
        "specified local file (%(const)s by default).",
    )
    source_group.add_argument(
        "--url", help="Download the known CT logs JSON file " "from the specified URL."
    )

    arg_parser.add_argument(
        "--out",
        default="../../certverifier/CTKnownLogs.h",
        help="Path and filename of the header file "
        "to be generated. Defaults to %(default)s",
    )

    run(arg_parser.parse_args())


if __name__ == "__main__":
    parse_arguments_and_run()