diohsc-0.1.1: ClientCert.hs

-- This file is part of Diohsc
-- Copyright (C) 2020 Martin Bays <mbays@sdf.org>
--
-- This program is free software: you can redistribute it and/or modify
-- it under the terms of version 3 of the GNU General Public License as
-- published by the Free Software Foundation, or any later version.
--
-- You should have received a copy of the GNU General Public License
-- along with this program.  If not, see http://www.gnu.org/licenses/.

{-# LANGUAGE OverloadedStrings #-}
{-# LANGUAGE CPP #-}

module ClientCert where

import Control.Applicative (liftA2)
import Crypto.Hash.Algorithms (SHA256(..))
import Crypto.PubKey.RSA
import Crypto.PubKey.RSA.PKCS15
import Data.ASN1.OID
import Data.ASN1.Types.String (ASN1StringEncoding(UTF8))
import Data.Either (fromRight)
import Data.Hourglass
import Data.PEM
import Data.X509
import Network.TLS (PrivKey(PrivKeyRSA))
import Safe
import System.FilePath
import Time.System

import qualified Data.ByteString as BS
import qualified Data.Text as TS
import qualified Data.Text.Encoding as TS

import Fingerprint
import Mundanities
import Util

#ifndef WINDOWS
import System.Posix.Files
#endif

-- |Certificate chain with secret key for tail cert
data ClientCert = ClientCert CertificateChain PrivKey
    deriving (Eq,Show)

clientCertFingerprint :: ClientCert -> Fingerprint
clientCertFingerprint (ClientCert (CertificateChain chain) _) =
    fingerprint $ head chain

loadClientCert :: FilePath -> String -> IO (Maybe ClientCert)
loadClientCert path name =
    let certpath = path </> name <.> "crt"
        keypath = path </> name <.> "rsa"
    in ignoreIOErrAlt $ do
        chain <- pemParseBS <$> BS.readFile certpath >>= \pem -> return $ case pem of
            Right pems -> case decodeCertificateChain . CertificateChainRaw $ map pemContent pems of
                Right chain -> Just chain
                _ -> Nothing
            _ -> Nothing
        key <- (PrivKeyRSA <$>) . readMay <$> readFile keypath
        return $ liftA2 ClientCert chain key

saveClientCert :: FilePath -> String -> ClientCert -> IO ()
saveClientCert path name (ClientCert chain (PrivKeyRSA key)) =
    let filepath = path </> name
        certpath = filepath <.> "crt"
        keypath = filepath <.> "rsa"
    in isSubPath path filepath >>? ignoreIOErr $ do
        let CertificateChainRaw rawCerts = encodeCertificateChain chain
            chainPEMs = map (pemWriteBS . PEM "CERTIFICATE" []) rawCerts
        BS.writeFile certpath $ BS.intercalate "\n" chainPEMs
        writeFile keypath $ show key
#ifndef WINDOWS
        setFileMode keypath $ unionFileModes ownerReadMode ownerWriteMode -- chmod 600
#endif
saveClientCert _ _ _ = putStrLn "! Error: can't save key of this type"

-- |generate 2048bit RSA key with (-1y,+2y) validity
-- FIXME: these choices fingerprint the client
generateSelfSigned :: String -> IO ClientCert
generateSelfSigned cn = do
    (pubKey, secKey) <- generate 256 65537
    blinder <- generateBlinder $ public_n pubKey
    currentTime <- timeConvert <$> timeCurrent
    let dn = DistinguishedName [(getObjectID DnCommonName, ASN1CharacterString UTF8 . TS.encodeUtf8 $ TS.pack cn)]
        sigAlg = SignatureALG HashSHA256 PubKeyALG_RSA
        to = timeConvert . dateAddPeriod currentTime $ Period {periodYears = 2, periodMonths = 0, periodDays = 0}
        from = timeConvert . dateAddPeriod currentTime $ Period {periodYears = -1, periodMonths = 0, periodDays = 0}
        cert = Certificate
            { certVersion = 3
            , certSerial = 0
            , certSignatureAlg = sigAlg
            , certIssuerDN = dn
            , certSubjectDN = dn
            , certValidity = (from, to)
            , certPubKey = PubKeyRSA pubKey
            , certExtensions = Extensions Nothing
            }
        signed = fst $ objectToSignedExact
            (\b -> (fromRight BS.empty $ sign (Just blinder) (Just SHA256) secKey b, sigAlg, ()))
            cert
    return $ ClientCert (CertificateChain [signed]) (PrivKeyRSA secKey)

{- Using Crypto.PubKey.Ed25519; perhaps if TLS1.3 becomes mandatory for 
-- gemini, we should use this?
import qualified Data.ByteArray as BA

generateSelfSigned :: String -> IO ClientCert
generateSelfSigned cn = do
    secKey <- generateSecretKey
    currentTime <- timeConvert <$> timeCurrent
    let pubKey = toPublic secKey
        dn = DistinguishedName [(getObjectID DnCommonName, ASN1CharacterString UTF8 . TS.encodeUtf8 $ TS.pack cn)]
        sigAlg = SignatureALG_IntrinsicHash PubKeyALG_Ed25519
        -- TODO: think about correct validity dates
        to = timeConvert . dateAddPeriod currentTime $ Period {periodYears = 1, periodMonths = 0, periodDays = 0}
        from = timeConvert . dateAddPeriod currentTime $ Period {periodYears = -1, periodMonths = 0, periodDays = 0}
        cert = Certificate
            { certVersion = 3
            , certSerial = 0
            , certSignatureAlg = sigAlg
            , certIssuerDN = dn
            , certSubjectDN = dn
            , certValidity = (from, to)
            , certPubKey = PubKeyEd25519 pubKey
            , certExtensions = Extensions Nothing
            }
        signed = fst $ objectToSignedExact
            (\b -> (BS.pack . BA.unpack $ sign secKey pubKey b, sigAlg, ()))
            cert
    return (CertificateChain [signed], PrivKeyEd25519 secKey)
-}