#!/usr/bin/python3

# Copyright (c) 2017-2018 Jonathan McDowell <noodles@earth.li>
# GNU GPL; v2 or later
#
# Process RT tickets for keyring-maint@debian as raised by the
# nm.debian.org web interface

# Semi-helpful gpgme/Python examples:
# https://pypkg.com/pypi/gpg/f/examples/

import datetime
import gpg
import io
import os
import pprint
import re
import requests
import subprocess
import sys
from urllib.parse import urlencode

debug = False
RT_BASE_URL = 'https://rt.debian.org/REST/1.0/'
KEYSERVERS = ['keyserver.ubuntu.com:11371', 'the.earth.li:11371',
        'pool.sks-keyservers.net:11371' ]
DAM = ['enrico', 'joerg', 'jmw', 'olasd', 'stuart']
FD = DAM + ['noodles', 'mattia', 'peb', 'santiago', 'tiago',
            'tobi', 'hartmans']

SIG_DAYS_WARN = 45
DATE_FORMAT = "%d/%m/%Y %H:%M:%S"

# Try to find the keyring base directory, assuming we live in /scripts/
basedir = os.path.dirname(os.path.dirname(os.path.realpath(sys.argv[0]))) + '/'
if os.path.exists(basedir + 'debian-keyring-pgp'):
    KEYRING_BASE_DIR = basedir
else:
    print("Can't find keyring directory.")
    sys.exit(-1)
GNUPG_HOME = KEYRING_BASE_DIR + 'gpghome/'

# Maps roles to keyring directories
role2keyring = {
    'DM': 'debian-maintainers-pgp',
    'DD': 'debian-keyring-pgp',
    'DN': 'debian-nonupload-pgp',
    'emeritus': 'emeritus-keyring-pgp',
}

# The keys must match nm2:backend/const.py:ALL_STATUS
desc2role = {
    'Debian Developer, uploading': 'DD',
    'Debian Developer, non-uploading': 'DN',
    'Debian Maintainer': 'DM',
    'Debian Maintainer, with guest account': 'DM',
    'Debian Contributor': 'DC',
    'Debian Contributor, with guest account': 'DC',
    'Debian Developer, emeritus': 'emeritus',
    'Debian Developer, removed': 'removed',
}

fp_regex = (r"[0-9A-F]{4} [0-9A-F]{4} [0-9A-F]{4} [0-9A-F]{4} [0-9A-F]{4}  " +
            r"[0-9A-F]{4} [0-9A-F]{4} [0-9A-F]{4} [0-9A-F]{4} [0-9A-F]{4}")
fp_regex_nospc = r"[0-9A-F]{40}"

# Global keyid to username/name dict
keyids = {}


def get_gpg_ctx(do_import=False):
    """ Setup (if necessary) and return a GnuPG context

    Checks if the private GnuPG home directory already exists. If not,
    creates it and imports the DD + DN keyrings into it. Also configures
    GnuPG to do clean imports (i.e. only include signatures that can be
    verified).
    """
    if not os.path.isdir(GNUPG_HOME):
        os.makedirs(GNUPG_HOME)
        do_import = True

    c = gpg.Context()

    c.set_engine_info(gpg.constants.protocol.OpenPGP,
                      home_dir=GNUPG_HOME)

    if do_import:
        for keyring in ['debian-keyring', 'debian-nonupload']:
            keyfile = KEYRING_BASE_DIR + 'output/keyrings/' + keyring + '.pgp'
            if not os.path.exists(keyfile):
                raise RuntimeError(keyfile + " does not exist. " +
                                   "Need to run 'make'?")
            keys = gpg.Data(file=keyfile)
            c.op_import(keys)

        with open(GNUPG_HOME + 'gpg.conf', 'w') as f:
            f.write('import-options import-clean\n')

    return c


def fetch_key(ctx, fpr):
    """Fetches the supplied fingerprint from a public keyserver

    Does an HKP lookup for the supplied fingerprint, then imports it into
    the current keyring. Then does an export (picking up any cleaning done
    by the import) and returns the binary key data.

    Note this function does not remove the key from the GnuPG keyring. If
    the key is destined for the DM keyring, or subsequently not to be added,
    it must be removed by the caller using delete_key().
    """
    gotkey = False
    for keyserver in KEYSERVERS:
        url = "http://{server}/pks/lookup?{query}".format(
                server=keyserver,
                query=urlencode({
                    "op": "get",
                    "search": "0x" + fpr,
                    "exact": "on",
                }))
        res = requests.get(url)
        keytext = []
        for line in res.text.splitlines():
            if line == "-----BEGIN PGP PUBLIC KEY BLOCK-----":
                gotkey = True
            if gotkey:
                keytext.append(line)
            if line == "-----END PGP PUBLIC KEY BLOCK-----":
                break
        if gotkey:
            break

    if not gotkey:
        raise RuntimeError('Failed to fetch key')

    key = gpg.Data(string="\n".join(keytext))
    ctx.op_import(key)

    key = gpg.Data()
    ctx.op_export(fpr, 0, key)
    key.seek(0, os.SEEK_SET)
    keydata = key.read()

    return keydata


def delete_key(ctx, fpr):
    """Delete the key matching fpr from the GnuPG keyring"""
    keys = list(ctx.keylist(fpr))
    for k in keys:
        ctx.op_delete(k, True)


def get_keyinfo(ctx, fpr, needsigs=2):
    ctx.set_keylist_mode(gpg.constants.keylist.mode.SIGS)
    key = ctx.get_key(fpr)
    for subkey in key.subkeys:
        if subkey.fpr == fpr:
            keytype = str(subkey.length)
            if subkey.pubkey_algo == gpg.constants.pk.RSA:
                keytype += 'R'
            elif subkey.pubkey_algo == gpg.constants.pk.DSA:
                keytype += 'D'
            elif subkey.pubkey_algo == gpg.constants.pk.ECC:
                keytype += 'E'
            elif subkey.pubkey_algo == gpg.constants.pk.EDDSA:
                keytype += 'E'
            elif subkey.pubkey_algo == gpg.constants.pk.ELG:
                keytype += 'g'
            else:
                keytype += '?'

    sigs = {}
    for uid in key.uids:
        # print(uid.name, uid.email)
        if not uid.revoked:
            for sig in uid.signatures:
                if sig.keyid in keyids:
                    sigs[keyids[sig.keyid]['username']] = 1
                # else:
                #    print("Skipping unknown ID " + sig.keyid)

    if len(sigs) < needsigs:
        print('\nWARNING: Insufficient key signatures, check endorsements\n')

    certs = None
    for sig in sorted(sigs.keys()):
        if certs:
            certs += ', ' + sig
        else:
            certs = sig

    return (keytype, certs)


def read_keyids():
    """Read the keyids file into a dict allowing a username/name mapping"""
    with open(KEYRING_BASE_DIR + 'keyids', 'r') as f:
        dds = f.readlines()
        for dd in dds:
            keyid = dd[2:18]
            name = dd[19:dd.find('<') - 1]
            username = dd[dd.find('<') + 1:]
            username = username[:username.find('>')]
            keyids[keyid] = {
                'name':     name,
                'username': username,
            }


def write_keyids():
    """Write the sorted keyids username/name dict out to the keyids file"""
    with open(KEYRING_BASE_DIR + 'keyids', 'w') as f:
        for key in sorted(keyids.keys()):
            f.write("0x{} {} <{}>\n".format(key,
                                            keyids[key]['name'],
                                            keyids[key]['username']))


def get_rt_auth():
    """Attempt to locate a valid set of RT login details

    Look for, and return, a set of RT login details. Uses RT_USER/RT_PASS
    from the environment, failing back to ~/.rtrc if either is not set.
    """
    rt_user = None
    rt_pass = None

    if 'RT_USER' in os.environ:
        rt_user = os.environ['RT_USER']
    if 'RT_PASS' in os.environ:
        rt_pass = os.environ['RT_PASS']

    if not rt_user or not rt_pass:
        with open(os.environ['HOME'] + '/.rtrc', 'r') as f:
            for line in f:
                if not rt_user and line.startswith('user '):
                    rt_user = line[5:].strip()
                elif not rt_pass and line.startswith('passwd '):
                    rt_pass = line[7:].strip()

    return (rt_user, rt_pass)


def fetch_ticket(rtid):
    (rt_user, rt_pass) = get_rt_auth()

    args = {
        'params': {
            'user': rt_user,
            'pass': rt_pass,
        }
    }

    print("Fetching ticket " + str(rtid))

    # res = requests.post(RT_BASE_URL + 'ticket/' + str(rtid) + '/show',
    #                    **args)
    # Look for "Owner: Nobody" or "Owner: noodles"
    # res = requests.post(RT_BASE_URL + 'ticket/' + str(rtid) + '/edit',
    #                    **args)
    # "content" variable = "Owner: noodles"

    res = requests.post(RT_BASE_URL + 'ticket/' + str(rtid) + '/attachments',
                        **args)

    # Validate the RT result
    res_lines = res.text.splitlines()
    ver, status, text = res_lines[0].split(None, 2)

    if int(status) != 200:
        print("RT status code is not 200", res_lines)
        return

    attachments = []
    inattachments = False
    text = None
    signature = None

    for line in res_lines[2:]:
        if inattachments:
            m = re.match(r' +(\d+):', line)
            if m:
                print('Attachment found, ' + m.group(1))
                attachments.append(int(m.group(1)))
            else:
                inattachments = False
        else:
            m = re.match(r'Attachments: (\d+):', line)
            if m:
                print('Attachment found, ' + m.group(1))
                attachments.append(int(m.group(1)))
                inattachments = True

    for attachment in attachments:
        res = requests.post(RT_BASE_URL + 'ticket/' + str(rtid) +
                            '/attachments/' + str(attachment),
                            **args)

        # Validate the RT result
        res_lines = res.text.splitlines()
        ver, status, text = res_lines[0].split(None, 2)

        if int(status) != 200:
            print("RT status code is not 200", res_lines)

        incontent = False
        message = []
        for line in res_lines[2:]:
            if line.startswith('Content: '):
                incontent = True
                message.append(line[9:])
            elif incontent and line.startswith('         '):
                message.append(line[9:])
            elif incontent:
                incontent = False

        with get_gpg_ctx() as c:
            sig = None
            try:
                text, result = c.verify(io.BytesIO(
                                        "\n".join(message).encode('utf-8')))
                sig = result.signatures[0]
            except IndexError:
                # The result does not include any signatures
                sig = None
            except gpg.errors.GPGMEError:
                text = None
                continue
            except gpg.errors.BadSignatures as e:
                # If a request is signed by multiple keys (such as old + new
                # for a replacement) the important thing is one of the
                # signatures is valid.
                for s in e.results[1].signatures:
                    if s.status == 0:
                        text = e.results[0]
                        sig = s
                        break
                    else:
                        print("Bad signature from", s.fpr)
            if sig:
                key = c.get_key(sig.fpr)
                # print(result.signatures[0].__str__())
                for subkey in key.subkeys:
                    if subkey.fpr[24:] in keyids:
                        signature = keyids[subkey.fpr[24:]]['username']
                print("Good signature from " + signature + " (" +
                      sig.fpr + ")")

                sig_date = datetime.datetime.fromtimestamp(sig.timestamp)
                now = datetime.datetime.now()
                if (now - sig_date) >= datetime.timedelta(days=SIG_DAYS_WARN):
                    print((
                        "WARNING: Old GPG signature ({formatted_sig_date}, "
                        "today is {formatted_now}), please verify validity."
                    ).format(
                        formatted_sig_date=sig_date.strftime(DATE_FORMAT),
                        formatted_now=now.strftime(DATE_FORMAT),
                    ))
                break
            else:
                print("Couldn't verify message.")

    return (signature, text)


def parse_ticket(text):
    state = {}

    for line in text.decode().split('\n'):
        if line.startswith('  Key fingerprint:  '):
            if line[20:] != 'None':
                state['keyid'] = line[20:]
        elif line.startswith('  Username:         '):
            state['username'] = line[20:]
        elif line.startswith('  uid:              '):
            state['username'] = line[20:]
        elif line.startswith('  Details:          '):
            state['details'] = line[20:]
        elif line.startswith('  First name:       '):
            state['first'] = line[20:]
        elif line.startswith('  Middle name:      '):
            state['middle'] = line[20:]
        elif line.startswith('  Last name:        '):
            state['last'] = line[20:]
        elif line.startswith('  Current status:   '):
            if line[20:] not in desc2role:
                print('Unknown current status: ' + line[20:])
            else:
                state['current'] = desc2role[line[20:]]
        elif line.startswith('  Target keyring:   '):
            if line[20:] not in desc2role:
                print('Unknown destination status: ' + line[20:])
            else:
                state['dest'] = desc2role[line[20:]]
        elif 'details' not in state:
            # Try to see if we have a fingerprint on the line and if
            # it might be a replacement request
            m = re.search(fp_regex, line)
            if not m:
                m = re.search(fp_regex_nospc, line)
            if m:
                fp = m.group(0).replace(' ', '')
                if fp[24:] in keyids:
                    state['oldkeyid'] = fp
                else:
                    state['keyid'] = fp


    # Based on the current + target statuses work out if this is an add or
    # remove.
    if 'dest' not in state:
        # Assume it's a replacement.
        for role in role2keyring:
            if os.path.exists(role2keyring[role] + '/0x' +
                              state['oldkeyid'][24:]):
                state['role'] = role
                break
        if 'role' not in state:
            state['role'] = 'DD'
        state['action'] = 'replace'
        state['subject'] = keyids[state['oldkeyid'][24:]]['name']
        state['username'] = keyids[state['oldkeyid'][24:]]['username']
    elif state['dest'] in ['DD', 'DM', 'DN']:
        state['action'] = 'add'
        state['role'] = state['dest']
    elif state['dest'] in ['DC', 'emeritus', 'removed']:
        state['action'] = 'remove'
        if 'current' in state:
            state['role'] = state['current']
        else:
            # Assume DD -> removed as a fall back
            state['role'] = 'DD'

    # Collapse first/middle/last to a single name field
    if 'first' in state and state['first'] != '-':
        state['subject'] = state['first']
    if 'middle' in state and state['middle'] != '-':
        if 'subject' in state:
            state['subject'] += ' ' + state['middle']
        else:
            state['subject'] = state['middle']
    if 'last' in state and state['last'] != '-':
        if 'subject' in state:
            state['subject'] += ' ' + state['last']
        else:
            state['subject'] = state['last']

    for field in ['details', 'username']:
        if field in state and state[field] == '-':
            del state[field]

    # Get the key length + type, plus signatures from other DDs
    if 'keyid' in state:
        with get_gpg_ctx() as c:
            if state['action'] in ('add', 'replace') or state['role'] == 'DM':
                state['keydata'] = fetch_key(c, state['keyid'])
            # If it's a removal we don't need to check signature count. For
            # DM we relax the number of signatures, otherwise we use the
            # default.
            if state['action'] == 'remove':
                keyinfo = get_keyinfo(c, state['keyid'], 0)
            elif state['role'] == 'DM':
                keyinfo = get_keyinfo(c, state['keyid'], 1)
            else:
                keyinfo = get_keyinfo(c, state['keyid'])
            state['keytype'] = keyinfo[0]
            state['certs'] = keyinfo[1]

    if 'oldkeyid' in state:
        with get_gpg_ctx() as c:
            fetch_key(c, state['oldkeyid'])
            keyinfo = get_keyinfo(c, state['oldkeyid'], 0)
            state['oldkeytype'] = keyinfo[0]

    return state


def do_action(state):
    if state['action'] == 'remove':
        if 'keyid' not in state:
            # When inactive DDs with no valid keys are retired,
            # there's nothing for us to do
            print('-!- Nothing for keyring-maint to do, please reasign ticket')
            print('-!- to DSA for account removal.')
            sys.exit(-1)
        if 'dest' in state and state['dest'] == 'emeritus':
            subprocess.call(['git', 'mv', role2keyring[state['role']] + '/0x' +
                             state['keyid'][24:],
                             'emeritus-keyring-pgp/'])
            state['logmsg'] = ('Move 0x' + state['keyid'][24:] +
                               ' (' + state['subject'] + ') to ' +
                               'emeritus (RT #' + state['rtid'] + ')')
        else:
            subprocess.call(['git', 'rm', role2keyring[state['role']] + '/0x' +
                             state['keyid'][24:]])
            state['logmsg'] = ('Remove 0x' + state['keyid'][24:] +
                               ' (' + state['subject'] + ')' +
                               ' (RT #' + state['rtid'] + ')')
        if state['role'] in ['DD', 'DN']:
            with get_gpg_ctx() as c:
                delete_key(c, state['keyid'])
    elif state['action'] == 'add':
        state['logmsg'] = ('Add new ' + state['dest'] + ' key 0x' +
                           state['keyid'][24:] + ' (' + state['subject'] +
                           ') (RT #' + state['rtid'] + ')')
        # See if it's just a move from a different keyring
        if state['current'] in role2keyring:
            subprocess.call(['git', 'mv',
                             role2keyring[state['current']] + '/0x' +
                             state['keyid'][24:],
                             role2keyring[state['dest']]])
            state['notes'] = 'Move from ' + state['current'] + ' keyring'
        else:
            keyfile = role2keyring[state['dest']] + '/0x' + state['keyid'][24:]
            with open(keyfile, 'wb') as f:
                f.write(state['keydata'])
            subprocess.call(['git', 'add', keyfile])

            # We don't keep DM keys in the our working keyring
            if state['dest'] == 'DM':
                with get_gpg_ctx() as c:
                    delete_key(c, state['keyid'])
        keyids[state['keyid'][24:]] = {
            'name':     state['subject'],
            'username': state['username'],
        }
        write_keyids()
        subprocess.call(['git', 'add', 'keyids'])
    elif state['action'] == 'replace':
        state['logmsg'] = ('Replace 0x' + state['oldkeyid'][24:] + ' with 0x' +
                           state['keyid'][24:] + ' (' + state['subject'] +
                           ') (RT #' + state['rtid'] + ')')

        keyfile = role2keyring[state['role']] + '/0x' + state['keyid'][24:]
        with open(keyfile, 'wb') as f:
            f.write(state['keydata'])
        subprocess.call(['git', 'add', keyfile])
        subprocess.call(['git', 'rm', role2keyring[state['role']] + '/0x' +
                                      state['oldkeyid'][24:]])

        # Remove the replaced key
        with get_gpg_ctx() as c:
            delete_key(c, state['oldkeyid'])

        keyids[state['keyid'][24:]] = {
            'name':     state['subject'],
            'username': state['username'],
        }
        write_keyids()
        subprocess.call(['git', 'add', 'keyids'])
    else:
        print("Don't know how to handle action: " + state['action'])


def do_dch(state):
    release = "unknown"
    with open('debian/changelog', 'r') as f:
        line = f.readline()
        m = re.match(r"debian-keyring \((.*)\) (.*); urgency=", line)
        version = m.group(1)
        release = m.group(2)
    if release == "UNRELEASED":
        if debug:
            print('dch --multimaint-merge -D UNRELEASED -a "' +
                  state['logmsg'] + '"')
        else:
            subprocess.call(['dch', '--multimaint-merge', '-D', 'UNRELEASED',
                             '-a', state['logmsg']])
    elif release == "unstable":
        newver = datetime.date.today().strftime("%Y.%m.xx")
        if newver == version:
            print(' * Warning: New version and previous released version are ')
            print('   the same: ' + newver + '. This should not be so!')
            print('   Check debian/changelog')
        if debug:
            print('dch -D UNRELEASED -v ' + newver + ' "' + state['logmsg'] +
                  '"')
        else:
            subprocess.call(['dch', '-D', 'UNRELEASED', '-v', newver,
                             state['logmsg']])
    else:
        print("Unknown changelog release: " + release)

    if not debug:
        subprocess.call(['git', 'add', 'debian/changelog'])


def do_git_template(state):
    with open('git-commit-template', 'w') as f:
        f.write(state['logmsg'])
        f.write('\n\n')
        f.write("Action: " + state['action'] + "\n")
        f.write("Subject: " + state['subject'] + "\n")
        if 'username' in state:
            f.write("Username: " + state['username'] + "\n")
        f.write("Role: " + state['role'] + "\n")
        if state['action'] == 'replace':
            f.write("Old-key: " + state['oldkeyid'] + "\n")
            f.write("Old-key-type: " + state['oldkeytype'] + "\n")
            f.write("New-key: " + state['keyid'] + "\n")
            f.write("New-key-type: " + state['keytype'] + "\n")
        else:
            f.write("Key: " + state['keyid'] + "\n")
            f.write("Key-type: " + state['keytype'] + "\n")
        f.write("RT-Ticket: " + state['rtid'] + "\n")
        f.write("Request-signed-by: " + state['requester'] + "\n")
        if state['action'] != 'remove' and state['certs'] != None:
            prefix = 'Key-certified-by: '
            prefixlen = len(prefix)
            certs = state['certs']
            while (len(certs) + prefixlen) > 72:
                last = certs.rfind(',', 0, 72 - prefixlen) + 1
                f.write(prefix + certs[:last] + "\n")
                certs = certs[last:]
                prefix = ' '
                prefixlen = 1
            f.write(prefix + certs + "\n")
        if 'details' in state:
            f.write("Details: " + state['details'] + "\n")
        if state['role'] == 'DM' and 'agreement' in state:
            f.write("Advocates:\n")
            for a in state['advocates']:
                f.write(" " + a + "\n")
            f.write("Agreement: " + state['agreement'] + "\n")
            f.write("BTS: " + state['bts'] + "\n")
        if 'notes' in state:
            f.write('Notes: ' + state['notes'] + '\n')


if len(sys.argv) < 2:
    print('Must supply RT ticket to process.')
    sys.exit(-1)

# Change to the keyring dir so that git etc work
os.chdir(KEYRING_BASE_DIR)

read_keyids()
(requester, ticket) = fetch_ticket(sys.argv[1])
if ticket is None:
    print('No signature on ticket.')
    sys.exit(-1)
if requester is None:
    print('Signature from unknown key.')
    sys.exit(-1)
state = parse_ticket(ticket)
state['rtid'] = sys.argv[1]
state['requester'] = requester
if state['action'] == 'add':
    if requester not in FD:
        print('Signature for add must come from Front Desk.')
        sys.exit(-1)
# Output our state for confirmation, without the keydata
pp = pprint.PrettyPrinter()
s = dict(state)
if 'keydata' in s:
    del s['keydata']
pp.pprint(s)
proceed = input("Do you wish to proceed? [y/n]: ")
if proceed.lower() not in ['y', 'yes']:
    print("Aborting.")
    # If this was an add we need to make sure the key isn't in our keyring
    if state['action'] in ['add', 'replace']:
        delete_key(get_gpg_ctx(), state['keyid'])
    sys.exit(-1)
do_action(state)
do_dch(state)
do_git_template(state)