#!/usr/bin/python3

import sys, os, getopt, binascii, json, pprint, signal, time
import urllib.request
import Crypto.PublicKey.RSA, Crypto.Random, Crypto.Hash.SHA256, Crypto.Signature.PKCS1_v1_5

service = "https://acme-v02.api.letsencrypt.org/directory"
_directory = None
def directory():
    global _directory
    if _directory is None:
        with req(service) as resp:
            _directory = json.loads(resp.read().decode("utf-8"))
    return _directory

def base64url(dat):
    return binascii.b2a_base64(dat).decode("us-ascii").translate({43: 45, 47: 95, 61: None}).strip()

def ebignum(num):
    h = "%x" % num
    if len(h) % 2 == 1: h = "0" + h
    return base64url(binascii.a2b_hex(h))

def getnonce():
    with urllib.request.urlopen(directory()["newNonce"]) as resp:
        resp.read()
        return resp.headers["Replay-Nonce"]

def req(url, data=None, ctype=None, headers={}, method=None, **kws):
    if data is not None and not isinstance(data, bytes):
        data = json.dumps(data).encode("utf-8")
        ctype = "application/jose+json"
    req = urllib.request.Request(url, data=data, method=method)
    for hnam, hval in headers.items():
        req.add_header(hnam, hval)
    if ctype is not None:
        req.add_header("Content-Type", ctype)
    return urllib.request.urlopen(req)

def jreq(url, data, auth):
    authdata = {"alg": "RS256", "url": url, "nonce": getnonce()}
    authdata.update(auth.authdata())
    authdata = base64url(json.dumps(authdata).encode("us-ascii"))
    if data is None:
        data = ""
    else:
        data = base64url(json.dumps(data).encode("us-ascii"))
    seal = base64url(auth.sign(("%s.%s" % (authdata, data)).encode("us-ascii")))
    enc = {"protected": authdata, "payload": data, "signature": seal}
    with req(url, data=enc) as resp:
        return json.loads(resp.read().decode("utf-8")), resp.headers

class certificate(object):
    @property
    def enddate(self):
        # No X509 parser for Python?
        import subprocess, re, calendar
        with subprocess.Popen(["openssl", "x509", "-noout", "-enddate"], stdin=subprocess.PIPE, stdout=subprocess.PIPE) as openssl:
            openssl.stdin.write(self.data.encode("us-ascii"))
            openssl.stdin.close()
            resp = openssl.stdout.read().decode("utf-8")
            if openssl.wait() != 0:
                raise Exception("openssl error")
        m = re.search(r"notAfter=(.*)$", resp)
        if m is None: raise Exception("unexpected openssl reply: %r" % (resp,))
        return calendar.timegm(time.strptime(m.group(1), "%b %d %H:%M:%S %Y GMT"))

    def expiring(self, timespec):
        if timespec.endswith("y"):
            timespec = int(timespec[:-1]) * 365 * 86400
        elif timespec.endswith("m"):
            timespec = int(timespec[:-1]) * 30 * 86400
        elif timespec.endswith("w"):
            timespec = int(timespec[:-1]) * 7 * 86400
        elif timespec.endswith("d"):
            timespec = int(timespec[:-1]) * 86400
        elif timespec.endswith("h"):
            timespec = int(timespec[:-1]) * 3600
        else:
            timespec = int(timespec)
        return (self.enddate - time.time()) < timespec

    @classmethod
    def read(cls, fp):
        self = cls()
        self.data = fp.read()
        return self

class signreq(object):
    def domains(self):
        # No PCKS10 parser for Python?
        import subprocess, re
        with subprocess.Popen(["openssl", "req", "-noout", "-text"], stdin=subprocess.PIPE, stdout=subprocess.PIPE) as openssl:
            openssl.stdin.write(self.data.encode("us-ascii"))
            openssl.stdin.close()
            resp = openssl.stdout.read().decode("utf-8")
            if openssl.wait() != 0:
                raise Exception("openssl error")
        m = re.search(r"X509v3 Subject Alternative Name:[^\n]*\n\s*((\w+:\S+,\s*)*\w+:\S+)\s*\n", resp)
        if m is None:
            return []
        ret = []
        for nm in m.group(1).split(","):
            nm = nm.strip()
            typ, nm = nm.split(":", 1)
            if typ == "DNS":
                ret.append(nm)
        return ret

    def der(self):
        import subprocess
        with subprocess.Popen(["openssl", "req", "-outform", "der"], stdin=subprocess.PIPE, stdout=subprocess.PIPE) as openssl:
            openssl.stdin.write(self.data.encode("us-ascii"))
            openssl.stdin.close()
            resp = openssl.stdout.read()
            if openssl.wait() != 0:
                raise Exception("openssl error")
        return resp

    @classmethod
    def read(cls, fp):
        self = cls()
        self.data = fp.read()
        return self

class jwkauth(object):
    def __init__(self, key):
        self.key = key

    def authdata(self):
        return {"jwk": {"kty": "RSA", "e": ebignum(self.key.e), "n": ebignum(self.key.n)}}

    def sign(self, data):
        dig = Crypto.Hash.SHA256.new()
        dig.update(data)
        return Crypto.Signature.PKCS1_v1_5.new(self.key).sign(dig)

class account(object):
    def __init__(self, uri, key):
        self.uri = uri
        self.key = key

    def authdata(self):
        return {"kid": self.uri}

    def sign(self, data):
        dig = Crypto.Hash.SHA256.new()
        dig.update(data)
        return Crypto.Signature.PKCS1_v1_5.new(self.key).sign(dig)

    def getinfo(self):
        data, headers = jreq(self.uri, None, self)
        return data

    def validate(self):
        data = self.getinfo()
        if data.get("status", "") != "valid":
            raise Exception("account is not valid: %s" % (data.get("status", "\"\"")))

    def write(self, out):
        out.write("%s\n" % (self.uri,))
        out.write("%s\n" % (self.key.exportKey().decode("us-ascii"),))

    @classmethod
    def read(cls, fp):
        uri = fp.readline()
        if uri == "":
            raise Exception("missing account URI")
        uri = uri.strip()
        key = Crypto.PublicKey.RSA.importKey(fp.read())
        return cls(uri, key)

class htconfig(object):
    def __init__(self):
        self.roots = {}

    @classmethod
    def read(cls, fp):
        self = cls()
        for ln in fp:
            words = ln.split()
            if len(words) < 1 or ln[0] == '#':
                continue
            if words[0] == "root":
                self.roots[words[1]] = words[2]
            else:
                sys.stderr.write("acmecert: warning: unknown htconfig directive: %s\n" % (words[0]))
        return self

def register(keysize=4096):
    key = Crypto.PublicKey.RSA.generate(keysize, Crypto.Random.new().read)
    # jwk = {"kty": "RSA", "e": ebignum(key.e), "n": ebignum(key.n)}
    # cjwk = json.dumps(jwk, separators=(',', ':'), sort_keys=True)
    data, headers = jreq(directory()["newAccount"], {"termsOfServiceAgreed": True}, jwkauth(key))
    return account(headers["Location"], key)
    
def mkorder(acct, csr):
    data, headers = jreq(directory()["newOrder"], {"identifiers": [{"type": "dns", "value": dn} for dn in csr.domains()]}, acct)
    data["acmecert.location"] = headers["Location"]
    return data

def httptoken(acct, ch):
    jwk = {"kty": "RSA", "e": ebignum(acct.key.e), "n": ebignum(acct.key.n)}
    dig = Crypto.Hash.SHA256.new()
    dig.update(json.dumps(jwk, separators=(',', ':'), sort_keys=True).encode("us-ascii"))
    khash = base64url(dig.digest())
    return ch["token"], ("%s.%s" % (ch["token"], khash))

def authorder(acct, htconf, orderid):
    order, headers = jreq(orderid, None, acct)
    valid = False
    tries = 0
    while not valid:
        valid = True
        tries += 1
        if tries > 5:
            raise Exception("challenges refuse to become valid even after 5 retries")
        for authuri in order["authorizations"]:
            auth, headers = jreq(authuri, None, acct)
            if auth["status"] == "valid":
                continue
            elif auth["status"] == "pending":
                pass
            else:
                raise Exception("unknown authorization status: %s" % (auth["status"],))
            valid = False
            if auth["identifier"]["type"] != "dns":
                raise Exception("unknown authorization type: %s" % (auth["identifier"]["type"],))
            dn = auth["identifier"]["value"]
            if dn not in htconf.roots:
                raise Exception("no configured ht-root for domain name %s" % (dn,))
            for ch in auth["challenges"]:
                if ch["type"] == "http-01":
                    break
            else:
                raise Exception("no http-01 challenge for %s" % (dn,))
            root = htconf.roots[dn]
            tokid, tokval = httptoken(acct, ch)
            tokpath = os.path.join(root, tokid);
            fp = open(tokpath, "w")
            try:
                with fp:
                    fp.write(tokval)
                with req("http://%s/.well-known/acme-challenge/%s" % (dn, tokid)) as resp:
                    if resp.read().decode("utf-8") != tokval:
                        raise Exception("challenge from %s does not match written value" % (dn,))
                for n in range(30):
                    resp, headers = jreq(ch["url"], {}, acct)
                    if resp["status"] == "processing":
                        time.sleep(2)
                    elif resp["status"] == "valid":
                        break
                    else:
                        raise Exception("unexpected challenge status for %s when validating: %s" % (dn, resp["status"]))
                else:
                    raise Exception("challenge processing timed out for %s" % (dn,))
            finally:
                os.unlink(tokpath)

def finalize(acct, csr, orderid):
    order, headers = jreq(orderid, None, acct)
    if order["status"] == "valid":
        pass
    elif order["status"] == "ready":
        jreq(order["finalize"], {"csr": base64url(csr.der())}, acct)
        for n in range(30):
            resp, headers = jreq(orderid, None, acct)
            if resp["status"] == "processing":
                time.sleep(2)
            elif resp["status"] == "valid":
                order = resp
                break
            else:
                raise Exception("unexpected order status when finalizing: %s" % resp["status"])
        else:
            raise Exception("order finalization timed out")
    else:
        raise Exception("unexpected order state when finalizing: %s" % (order["status"],))
    with req(order["certificate"]) as resp:
        return resp.read().decode("us-ascii")

class maybeopen(object):
    def __init__(self, name, mode):
        if name == "-":
            self.opened = False
            if mode == "r":
                self.fp = sys.stdin
            elif mode == "w":
                self.fp = sys.stdout
            else:
                raise ValueError(mode)
        else:
            self.opened = True
            self.fp = open(name, mode)

    def __enter__(self):
        return self.fp

    def __exit__(self, *excinfo):
        if self.opened:
            self.fp.close()
        return False

class usageerr(Exception):
    pass

commands = {}

def cmd_reg(args):
    "usage: acmecert reg [OUTPUT-FILE]"
    acct = register()
    os.umask(0o077)
    with maybeopen(args[1] if len(args) > 1 else "-", "w") as fp:
        acct.write(fp)
commands["reg"] = cmd_reg

def cmd_validate_acct(args):
    "usage: acmecert validate-acct ACCOUNT-FILE"
    if len(args) < 2: raise usageerr()
    with maybeopen(args[1], "r") as fp:
        account.read(fp).validate()
commands["validate-acct"] = cmd_validate_acct

def cmd_acct_info(args):
    "usage: acmecert acct-info ACCOUNT-FILE"
    if len(args) < 2: raise usageerr()
    with maybeopen(args[1], "r") as fp:
        pprint.pprint(account.read(fp).getinfo())
commands["acct-info"] = cmd_acct_info

def cmd_order(args):
    "usage: acmecert order ACCOUNT-FILE CSR [OUTPUT-FILE]"
    if len(args) < 4: raise usageerr()
    with maybeopen(args[1], "r") as fp:
        acct = account.read(fp)
    with maybeopen(args[2], "r") as fp:
        csr = signreq.read(fp)
    order = mkorder(acct, csr)
    with maybeopen(args[3] if len(args) > 3 else "-", "w") as fp:
        fp.write("%s\n" % (order["acmecert.location"]))
commands["order"] = cmd_order

def cmd_http_auth(args):
    "usage: acmecert http-auth ACCOUNT-FILE HTTP-CONFIG {ORDER-ID|ORDER-FILE}"
    if len(args) < 4: raise usageerr()
    with maybeopen(args[1], "r") as fp:
        acct = account.read(fp)
    with maybeopen(args[2], "r") as fp:
        htconf = htconfig.read(fp)
    if "://" in args[3]:
        orderid = args[3]
    else:
        with maybeopen(args[3], "r") as fp:
            orderid = fp.readline().strip()
    authorder(acct, htconf, orderid)
commands["http-auth"] = cmd_http_auth

def cmd_get(args):
    "usage: acmecert get ACCOUNT-FILE CSR {ORDER-ID|ORDER-FILE}"
    if len(args) < 4: raise usageerr()
    with maybeopen(args[1], "r") as fp:
        acct = account.read(fp)
    with maybeopen(args[2], "r") as fp:
        csr = signreq.read(fp)
    if "://" in args[3]:
        orderid = args[3]
    else:
        with maybeopen(args[3], "r") as fp:
            orderid = fp.readline().strip()
    sys.stdout.write(finalize(acct, csr, orderid))
commands["get"] = cmd_get

def cmd_http_order(args):
    "usage: acmecert http-order ACCOUNT-FILE CSR HTTP-CONFIG [OUTPUT-FILE]"
    if len(args) < 4: raise usageerr()
    with maybeopen(args[1], "r") as fp:
        acct = account.read(fp)
    with maybeopen(args[2], "r") as fp:
        csr = signreq.read(fp)
    with maybeopen(args[3], "r") as fp:
        htconf = htconfig.read(fp)
    orderid = mkorder(acct, csr)["acmecert.location"]
    authorder(acct, htconf, orderid)
    with maybeopen(args[4] if len(args) > 4 else "-", "w") as fp:
        fp.write(finalize(acct, csr, orderid))
commands["http-order"] = cmd_http_order

def cmd_check_cert(args):
    "usage: acmecert check-cert CERT-FILE TIME-SPEC"
    if len(args) < 3: raise usageerr()
    with maybeopen(args[1], "r") as fp:
        crt = certificate.read(fp)
    sys.exit(1 if crt.expiring(args[2]) else 0)
commands["check-cert"] = cmd_check_cert

def cmd_directory(args):
    "usage: acmecert directory"
    pprint.pprint(directory())
commands["directory"] = cmd_directory

def usage(out):
    out.write("usage: acmecert [-D SERVICE] COMMAND [ARGS...]\n")
    out.write("       acmecert -h [COMMAND]\n")
    buf =     "       COMMAND is any of: "
    f = True
    for cmd in commands:
        if len(buf) + len(cmd) > 70:
            out.write("%s\n" % (buf,))
            buf =     "           "
            f = True
        if not f:
            buf += ", "
        buf += cmd
        f = False
    if not f:
        out.write("%s\n" % (buf,))

def main(argv):
    global service
    opts, args = getopt.getopt(argv[1:], "hD:")
    for o, a in opts:
        if o == "-h":
            if len(args) > 0:
                cmd = commands.get(args[0])
                if cmd is None:
                    sys.stderr.write("acmecert: unknown command: %s\n" % (args[0],))
                    sys.exit(1)
                sys.stdout.write("%s\n" % (cmd.__doc__,))
            else:
                usage(sys.stdout)
            sys.exit(0)
        elif o == "-D":
            service = a
    if len(args) < 1:
        usage(sys.stderr)
        sys.exit(1)
    cmd = commands.get(args[0])
    if cmd is None:
        sys.stderr.write("acmecert: unknown command: %s\n" % (args[0],))
        usage(sys.stderr)
        sys.exit(1)
    try:
        cmd(args)
    except usageerr:
        sys.stderr.write("%s\n" % (cmd.__doc__,))
        sys.exit(1)

if __name__ == "__main__":
    try:
        main(sys.argv)
    except KeyboardInterrupt:
        signal.signal(signal.SIGINT, signal.SIG_DFL)
        os.kill(os.getpid(), signal.SIGINT)