#!/usr/bin/env python3
# Copyright Daniel Roesler, under MIT license, see LICENSE at github.com/diafygi/acme-tiny
import argparse, subprocess, json, os, sys, base64, binascii, time, hashlib, re, copy, textwrap, logging
from pritunl import settings
from pritunl import logger
try:
    from urllib.request import urlopen, Request # Python 3
except ImportError:
    from urllib.request import urlopen, Request # Python 2

#DEFAULT_CA = "https://acme-v02.api.letsencrypt.org" # DEPRECATED! USE DEFAULT_DIRECTORY_URL INSTEAD
#DEFAULT_DIRECTORY_URL = "https://acme-v02.api.letsencrypt.org/directory"

def get_crt(account_key, csr, set_acme, contact=None):
    directory, acct_headers, alg, jwk = None, None, None, None # global variables

    # helper functions - base64 encode for jose spec
    def _b64(b):
        return base64.urlsafe_b64encode(b).decode('utf8').replace("=", "")

    # helper function - run external commands
    def _cmd(cmd_list, stdin=None, cmd_input=None, err_msg="Command Line Error"):
        proc = subprocess.Popen(cmd_list, stdin=stdin, stdout=subprocess.PIPE, stderr=subprocess.PIPE)
        out, err = proc.communicate(cmd_input)
        if proc.returncode != 0:
            raise OSError("{0}\n{1}".format(err_msg, err))
        return out

    # helper function - make request and automatically parse json response
    def _do_request(url, data=None, err_msg="Error", depth=0):
        try:
            resp = urlopen(Request(url, data=data, headers={"Content-Type": "application/jose+json", "User-Agent": "acme-tiny"}))
            resp_data, code, headers = resp.read().decode("utf8"), resp.getcode(), resp.headers
            try:
                resp_data = json.loads(resp_data) # try to parse json results
            except ValueError:
                pass # ignore json parsing errors
        except OSError as e:
            resp_data = e.read().decode("utf8") if hasattr(e, "read") else str(e)
            code, headers = getattr(e, "code", None), {}
        if depth < 100 and code == 400 and json.loads(resp_data)['type'] == "urn:ietf:params:acme:error:badNonce":
            raise IndexError(resp_data) # allow 100 retrys for bad nonces
        if code not in [200, 201, 204]:
            raise ValueError("{0}:\nUrl: {1}\nData: {2}\nResponse Code: {3}\nResponse: {4}".format(err_msg, url, data, code, resp_data))
        return resp_data, code, headers

    # helper function - make signed requests
    def _send_signed_request(url, payload, err_msg, depth=0):
        payload64 = _b64(json.dumps(payload).encode('utf8'))
        new_nonce = _do_request(directory['newNonce'])[2]['Replay-Nonce']
        protected = {"url": url, "alg": alg, "nonce": new_nonce}
        protected.update({"jwk": jwk} if acct_headers is None else {"kid": acct_headers['Location']})
        protected64 = _b64(json.dumps(protected).encode('utf8'))
        protected_input = "{0}.{1}".format(protected64, payload64).encode('utf8')
        out = _cmd(["openssl", "dgst", "-sha256", "-sign", account_key], stdin=subprocess.PIPE, cmd_input=protected_input, err_msg="OpenSSL Error")
        data = json.dumps({"protected": protected64, "payload": payload64, "signature": _b64(out)})
        try:
            return _do_request(url, data=data.encode('utf8'), err_msg=err_msg, depth=depth)
        except IndexError: # retry bad nonces (they raise IndexError)
            return _send_signed_request(url, payload, err_msg, depth=(depth + 1))

    # helper function - poll until complete
    def _poll_until_not(url, pending_statuses, err_msg):
        while True:
            result, _, _ = _do_request(url, err_msg=err_msg)
            if result['status'] in pending_statuses:
                time.sleep(2)
                continue
            return result

    # parse account key to get public key
    logger.info("Parsing account key...")
    out = _cmd(["openssl", "rsa", "-in", account_key, "-noout", "-text"], err_msg="OpenSSL Error")
    pub_pattern = r"modulus:\n\s+00:([a-f0-9\:\s]+?)\npublicExponent: ([0-9]+)"
    pub_hex, pub_exp = re.search(pub_pattern, out.decode('utf8'), re.MULTILINE|re.DOTALL).groups()
    pub_exp = "{0:x}".format(int(pub_exp))
    pub_exp = "0{0}".format(pub_exp) if len(pub_exp) % 2 else pub_exp
    alg = "RS256"
    jwk = {
        "e": _b64(binascii.unhexlify(pub_exp.encode("utf-8"))),
        "kty": "RSA",
        "n": _b64(binascii.unhexlify(re.sub(r"(\s|:)", "", pub_hex).encode("utf-8"))),
    }
    accountkey_json = json.dumps(jwk, sort_keys=True, separators=(',', ':'))
    thumbprint = _b64(hashlib.sha256(accountkey_json.encode('utf8')).digest())

    # find domains
    logger.info("Parsing CSR...")
    out = _cmd(["openssl", "req", "-in", csr, "-noout", "-text"], err_msg="Error loading {0}".format(csr))
    domains = set([])
    common_name = re.search(r"Subject:.*? CN\s?=\s?([^\s,;/]+)", out.decode('utf8'))
    if common_name is not None:
        domains.add(common_name.group(1))
    subject_alt_names = re.search(r"X509v3 Subject Alternative Name: \n +([^\n]+)\n", out.decode('utf8'), re.MULTILINE|re.DOTALL)
    if subject_alt_names is not None:
        for san in subject_alt_names.group(1).split(", "):
            if san.startswith("DNS:"):
                domains.add(san[4:])
    logger.info("Found domains: {0}".format(", ".join(domains)))

    # get the ACME directory of urls
    logger.info("Getting directory...")
    directory_url = settings.app.acme_api_url # backwards compatibility with deprecated CA kwarg
    directory, _, _ = _do_request(directory_url, err_msg="Error getting directory")
    logger.info("Directory found!")

    # create account, update contact details (if any), and set the global key identifier
    logger.info("Registering account...")
    reg_payload = {"termsOfServiceAgreed": True}
    account, code, acct_headers = _send_signed_request(directory['newAccount'], reg_payload, "Error registering")
    logger.info("Registered!" if code == 201 else "Already registered!")
    if contact is not None:
        account, _, _ = _send_signed_request(acct_headers['Location'], {"contact": contact}, "Error updating contact details")
        logger.info("Updated contact details:\n{0}".format("\n".join(account['contact'])))

    # create a new order
    logger.info("Creating new order...")
    order_payload = {"identifiers": [{"type": "dns", "value": d} for d in domains]}
    order, _, order_headers = _send_signed_request(directory['newOrder'], order_payload, "Error creating new order")
    logger.info("Order created!")

    # get the authorizations that need to be completed
    for auth_url in order['authorizations']:
        authorization, _, _ = _do_request(auth_url, err_msg="Error getting challenges")
        domain = authorization['identifier']['value']
        logger.info("Verifying {0}...".format(domain))

        # find the http-01 challenge and write the challenge file
        challenge = [c for c in authorization['challenges'] if c['type'] == "http-01"][0]
        token = re.sub(r"[^A-Za-z0-9_\-]", "_", challenge['token'])
        keyauthorization = "{0}.{1}".format(token, thumbprint)
        set_acme(token, keyauthorization)

        # say the challenge is done
        _send_signed_request(challenge['url'], {}, "Error submitting challenges: {0}".format(domain))
        authorization = _poll_until_not(auth_url, ["pending"], "Error checking challenge status for {0}".format(domain))
        if authorization['status'] != "valid":
            raise ValueError("Challenge did not pass for {0}: {1}".format(domain, authorization))
        logger.info("{0} verified!".format(domain))

    # finalize the order with the csr
    logger.info("Signing certificate...")
    csr_der = _cmd(["openssl", "req", "-in", csr, "-outform", "DER"], err_msg="DER Export Error")
    _send_signed_request(order['finalize'], {"csr": _b64(csr_der)}, "Error finalizing order")

    # poll the order to monitor when it's done
    order = _poll_until_not(order_headers['Location'], ["pending", "processing"], "Error checking order status")
    if order['status'] != "valid":
        raise ValueError("Order failed: {0}".format(order))

    # download the certificate
    certificate_pem, _, _ = _do_request(order['certificate'], err_msg="Certificate download failed")
    logger.info("Certificate signed!")
    return certificate_pem
