module SSH where
import Control.Concurrent (forkIO)
import Control.Concurrent.Chan
import Control.Exception (bracket)
import Control.Monad (replicateM)
import Control.Monad.Trans.State
import Data.Digest.Pure.SHA (bytestringDigest, sha1)
import Crypto.HMAC
import Crypto.Hash.CryptoAPI
import Data.List (intercalate)
import Data.List.Split (splitOn)
import Network
import OpenSSL.BN (randIntegerOneToNMinusOne, modexp)
import System.IO
import System.Random
import qualified Data.ByteString.Lazy as LBS
import qualified Data.Map as M
import qualified Data.Serialize as S
import SSH.Channel
import SSH.Crypto
import SSH.Debug
import SSH.NetReader
import SSH.Packet
import SSH.Sender
import SSH.Session
import SSH.Util
version :: String
version = "SSH-2.0-DarcsDen"
supportedKeyExchanges :: [String]
supportedKeyExchanges =
["diffie-hellman-group1-sha1"]
supportedKeyAlgorithms :: [String]
supportedKeyAlgorithms = ["ssh-rsa", "ssh-dss"]
supportedCiphers :: [(String, Cipher)]
supportedCiphers =
[ ("aes256-cbc", aesCipher CBC 32)
, ("aes192-cbc", aesCipher CBC 24)
, ("aes128-cbc", aesCipher CBC 16)
]
where
aesCipher m s =
Cipher AES m 16 s
supportedMACs :: [(String, LBS.ByteString -> HMAC)]
supportedMACs =
[ ("hmac-sha1", makeHMAC True)
, ("hmac-md5", makeHMAC False)
]
where
makeHMAC True k = HMAC 20 $ \b -> bsToLBS . S.runPut $ S.put (hmac (MacKey (strictLBS (LBS.take 20 k))) b :: SHA1)
makeHMAC False k = HMAC 16 $ \b -> bsToLBS . S.runPut $ S.put (hmac (MacKey (strictLBS (LBS.take 16 k))) b :: MD5)
bsToLBS = LBS.fromChunks . (: [])
supportedCompression :: String
supportedCompression = "none"
supportedLanguages :: String
supportedLanguages = ""
data Config =
Config {
cSession :: SessionConfig,
cChannel :: ChannelConfig,
cPort :: PortNumber,
cReadyAction :: IO ()
}
startedMessage :: PortNumber -> IO ()
startedMessage p = putStrLn $ "ssh server listening on port " ++ show p
start :: SessionConfig -> ChannelConfig -> PortNumber -> IO ()
start sc cc p = startConfig (Config sc cc p (startedMessage p))
startConfig :: Config -> IO ()
startConfig config = withSocketsDo $ do
bracket
(listenOn (PortNumber (cPort config)))
sClose
(\sock -> do
cReadyAction config
waitLoop (cSession config) (cChannel config) sock
)
waitLoop :: SessionConfig -> ChannelConfig -> Socket -> IO ()
waitLoop sc cc s = do
(handle, hostName, port) <- accept s
io $ hSetBinaryMode handle True
dump ("got connection from", hostName, port)
forkIO $ do
hPutStr handle (version ++ "\r\n")
hFlush handle
done <- hIsEOF handle
if done
then return ()
else do
theirVersion <- hGetLine handle >>= return . takeWhile (/= '\r')
cookie <- fmap (LBS.pack . map fromIntegral) $
replicateM 16 (randomRIO (0, 255 :: Int))
let ourKEXInit = doPacket $ pKEXInit cookie
out <- newChan
forkIO (sender out (NoKeys handle 0))
evalStateT
(send (Send ourKEXInit) >> readLoop)
(Initial
{ ssConfig = sc
, ssChannelConfig = cc
, ssThem = handle
, ssSend = writeChan out
, ssPayload = LBS.empty
, ssTheirVersion = theirVersion
, ssOurKEXInit = ourKEXInit
, ssInSeq = 0
})
waitLoop sc cc s
where
pKEXInit :: LBS.ByteString -> Packet ()
pKEXInit cookie = do
byte 20
raw cookie
mapM_ string
[ intercalate "," $ supportedKeyExchanges
, intercalate "," $ supportedKeyAlgorithms
, intercalate "," $ map fst supportedCiphers
, intercalate "," $ map fst supportedCiphers
, intercalate "," $ map fst supportedMACs
, intercalate "," $ map fst supportedMACs
, supportedCompression
, supportedCompression
, supportedLanguages
, supportedLanguages
]
byte 0
long 0
readLoop :: Session ()
readLoop = do
done <- gets ssThem >>= io . hIsEOF
if done
then shutdownChannels
else do
getPacket
msg <- net readByte
if msg == 1 || msg == 97
then shutdownChannels
else do
case msg of
5 -> serviceRequest
20 -> kexInit
21 -> newKeys
30 -> kexDHInit
50 -> userAuthRequest
90 -> channelOpen
94 -> dataReceived
96 -> eofReceived
98 -> channelRequest
u -> dump $ "unknown message: " ++ show u
modify (\s -> s { ssInSeq = ssInSeq s + 1 })
readLoop
where
shutdownChannels = do
s <- get
case s of
Final { ssChannels = cs } ->
mapM_ (io . flip writeChan Interrupt) (M.elems cs)
_ -> return ()
io $ ssSend s Stop
kexInit :: Session ()
kexInit = do
cookie <- net (readBytes 16)
nameLists <- fmap (map (splitOn "," . fromLBS)) (replicateM 10 (net readLBS))
kpf <- net readByte
dummy <- net readULong
let theirKEXInit = reconstruct cookie nameLists kpf dummy
ocn = match (nameLists !! 3) (map fst supportedCiphers)
icn = match (nameLists !! 2) (map fst supportedCiphers)
omn = match (nameLists !! 5) (map fst supportedMACs)
imn = match (nameLists !! 4) (map fst supportedMACs)
dump ("KEXINIT", theirKEXInit, ocn, icn, omn, imn)
modify $ \st ->
case st of
Initial c cc h s p cv sk is ->
case
( lookup ocn supportedCiphers
, lookup icn supportedCiphers
, lookup omn supportedMACs
, lookup imn supportedMACs
) of
(Just oc, Just ic, Just om, Just im) ->
GotKEXInit
{ ssConfig = c
, ssChannelConfig = cc
, ssThem = h
, ssSend = s
, ssPayload = p
, ssTheirVersion = cv
, ssOurKEXInit = sk
, ssTheirKEXInit = theirKEXInit
, ssOutCipher = oc
, ssInCipher = ic
, ssOutHMACPrep = om
, ssInHMACPrep = im
, ssInSeq = is
}
_ ->
error . concat $
[ "impossible: lookup failed for ciphers/macs: "
, show (ocn, icn, omn, imn)
]
_ -> error "impossible state transition; expected Initial"
where
match n h = head . filter (`elem` h) $ n
reconstruct c nls kpf dummy = doPacket $ do
byte 20
raw c
mapM_ (string . intercalate ",") nls
byte kpf
long dummy
kexDHInit :: Session ()
kexDHInit = do
e <- net readInteger
dump ("KEXDH_INIT", e)
y <- io $ randIntegerOneToNMinusOne ((safePrime 1) `div` 2)
let f = modexp generator y safePrime
k = modexp e y safePrime
keyPair <- gets (scKeyPair . ssConfig)
let pub =
case keyPair of
RSAKeyPair { rprivPub = p } -> p
DSAKeyPair { dprivPub = p } -> p
d <- digest e f k pub
let [civ, siv, ckey, skey, cinteg, sinteg] = map (makeKey k d) ['A'..'F']
dump ("DECRYPT KEY/IV", LBS.take 16 ckey, LBS.take 16 civ)
oc <- gets ssOutCipher
om <- gets ssOutHMACPrep
send $
Prepare
oc
(strictLBS $ LBS.take (fromIntegral $ cKeySize oc) $ skey)
(strictLBS $ LBS.take (fromIntegral $ cBlockSize oc) $ siv)
(om sinteg)
modify $ \st ->
case st of
GotKEXInit c cc h s p _ _ is _ _ ic _ im ->
Final
{ ssConfig = c
, ssChannelConfig = cc
, ssChannels = M.empty
, ssID = d
, ssThem = h
, ssSend = s
, ssPayload = p
, ssGotNEWKEYS = False
, ssInSeq = is
, ssInCipher = ic
, ssInHMAC = im cinteg
, ssInKey =
strictLBS $ LBS.take (fromIntegral $ cKeySize ic) $ ckey
, ssInVector =
strictLBS $ LBS.take (fromIntegral $ cBlockSize ic) $ civ
, ssUser = Nothing
}
_ -> error "impossible state transition; expected GotKEXInit"
signed <- io $ sign keyPair d
let reply = doPacket (kexDHReply f signed pub)
dump ("KEXDH_REPLY", reply)
send (Send reply)
where
kexDHReply f s p = do
byte 31
byteString (blob p)
integer f
byteString s
digest e f k p = do
cv <- gets ssTheirVersion
ck <- gets ssTheirKEXInit
sk <- gets ssOurKEXInit
return . bytestringDigest . sha1 . doPacket $ do
string cv
string version
byteString ck
byteString sk
byteString (blob p)
integer e
integer f
integer k
newKeys :: Session ()
newKeys = do
sendPacket (byte 21)
send StartEncrypting
modify (\ss -> ss { ssGotNEWKEYS = True })
serviceRequest :: Session ()
serviceRequest = do
name <- net readLBS
sendPacket $ do
byte 6
byteString name
userAuthRequest :: Session ()
userAuthRequest = do
user <- net readLBS
service <- net readLBS
method <- net readLBS
auth <- gets (scAuthorize . ssConfig)
authMethods <- gets (scAuthMethods . ssConfig)
dump ("userauth attempt", user, service, method)
let
authorized = do
sendPacket userAuthOK
modify (\s -> s { ssUser = Just (fromLBS user) })
authfailed = sendPacket $ userAuthFail authMethods
case fromLBS method of
x | not (x `elem` authMethods) -> authfailed
"publickey" -> do
b <- net readByte
name <- net readLBS
key <- net readLBS
let pkey = blobToKey key
ch <- auth (PublicKey (fromLBS user) pkey)
case (ch, b == 1) of
(False, _) -> authfailed
(True, True) ->
do sig <- net readLBS
sessionID <- gets ssID
let message =
doPacket $ do
byteString sessionID
byte 50
byteString user
byteString service
string "publickey"
byte 1
byteString name
byteString key
ok <- io $ verify pkey message sig
if ok then authorized else authfailed
(True, False) -> sendPacket $ userAuthPKOK name key
"password" -> do
0 <- net readByte
password <- net readLBS
ch <- auth (Password (fromLBS user) (fromLBS password))
if ch then authorized else authfailed
u -> error $ "unhandled authorization type: " ++ u
where
userAuthFail ms = do
byte 51
string (intercalate "," ms)
byte 0
userAuthPKOK name key = do
byte 60
byteString name
byteString key
userAuthOK = byte 52
channelOpen :: Session ()
channelOpen = do
name <- net readLBS
them <- net readULong
windowSize <- net readULong
maxPacketLength <- net readULong
dump ("channel open", name, them, windowSize, maxPacketLength)
us <- newChannelID
chan <- do
c <- gets ssChannelConfig
s <- gets ssSend
Just u <- gets ssUser
io $ newChannel c s us them windowSize maxPacketLength u
modify (\s -> s
{ ssChannels = M.insert us chan (ssChannels s) })
channelRequest :: Session ()
channelRequest = do
chan <- net readULong >>= getChannel
typ <- net readLBS
wantReply <- net readBool
let sendRequest = io . writeChan chan . Request wantReply
case fromLBS typ of
"pty-req" -> do
term <- net readString
cols <- net readULong
rows <- net readULong
width <- net readULong
height <- net readULong
modes <- net readString
sendRequest (PseudoTerminal term cols rows width height modes)
"x11-req" -> sendRequest X11Forwarding
"shell" -> sendRequest Shell
"exec" -> do
command <- net readString
dump ("execute command", command)
sendRequest (Execute command)
"subsystem" -> do
name <- net readString
dump ("subsystem request", name)
sendRequest (Subsystem name)
"env" -> do
name <- net readString
value <- net readString
dump ("environment request", name, value)
sendRequest (Environment name value)
"window-change" -> do
cols <- net readULong
rows <- net readULong
width <- net readULong
height <- net readULong
sendRequest (WindowChange cols rows width height)
"xon-xoff" -> do
b <- net readBool
sendRequest (FlowControl b)
"signal" -> do
name <- net readString
sendRequest (Signal name)
"exit-status" -> do
status <- net readULong
sendRequest (ExitStatus status)
"exit-signal" -> do
name <- net readString
dumped <- net readBool
msg <- net readString
lang <- net readString
sendRequest (ExitSignal name dumped msg lang)
u -> sendRequest (Unknown u)
dump ("request processed")
dataReceived :: Session ()
dataReceived = do
dump "got data"
chan <- net readULong >>= getChannel
msg <- net readLBS
io $ writeChan chan (Data msg)
dump "data processed"
eofReceived :: Session ()
eofReceived = do
chan <- net readULong >>= getChannel
io $ writeChan chan EOF