@@ -4,73 +4,222 @@
44 Stability: beta
55 Portability: portable
66
7− Obtain entropy from system sources or x86 RDRAND when available.
8−
9− Currently supporting:
10−
11− - Windows via CryptoAPI
12− - *nix systems via @\/dev\/urandom@
13− - Includes QNX
14− - ghcjs/browser via JavaScript crypto API.
7+ Obtain entropy from system sources.
8+ Currently, windows and *nix systems with a @/dev/urandom@ are supported.
159-}
1610
1711module System.Entropy
18− ( getEntropy,
19− getHardwareEntropy,
20− CryptHandle,
21− openHandle,
22− hGetEntropy,
23− closeHandle
12+ ( getEntropy
13+ , CryptHandle
14+ , openHandle
15+ , hGetEntropy
16+ , closeHandle
2417 ) where
2518
26−#ifdef ghcjs_HOST_OS
27−import System.EntropyGhcjs
28−#elif defined(isWindows)
29−import System.EntropyWindows
30−#else
31−import System.EntropyNix
19+import Control.Monad (liftM)
20+import Data.ByteString as B
21+import System.IO.Error (mkIOError, eofErrorType, ioeSetErrorString)
22+import System.Posix (openFd, closeFd, fdReadBuf, OpenMode(..), defaultFileFlags, Fd)
23+import Foreign (allocaBytes)
24+
25+#if defined(isWindows)
26+{- C example for windows rng - taken from a blog, can't recall which one but thank you!
27+ #include <Windows.h>
28+ #include <Wincrypt.h>
29+ ...
30+ //
31+ // DISCLAIMER: Don't forget to check your error codes!!
32+ // I am not checking as to make the example simple...
33+ //
34+ HCRYPTPROV hCryptCtx = NULL;
35+ BYTE randomArray[128];
36+
37+ CryptAcquireContext(&hCryptCtx, NULL, MS_DEF_PROV, PROV_RSA_FULL, CRYPT_VERIFYCONTEXT);
38+ CryptGenRandom(hCryptCtx, 128, randomArray);
39+ CryptReleaseContext(hCryptCtx, 0);
40+-}
41+
42+import Data.ByteString.Internal as BI
43+import Data.Int (Int32)
44+import Data.Word (Word32, Word8)
45+import Foreign.C.String (CString, withCString)
46+import Foreign.C.Types
47+import Foreign.Ptr (Ptr, nullPtr, castPtr)
48+import Foreign.Marshal.Alloc (alloca)
49+import Foreign.Marshal.Utils (toBool)
50+import Foreign.Storable (peek)
51+
52+#ifdef HAVE_RDRAND
53+foreign import ccall unsafe "cpu_has_rdrand"
54+ c_cpu_has_rdrand :: IO CInt
55+
56+foreign import ccall unsafe "get_rand_bytes"
57+ c_get_rand_bytes :: Ptr CUChar -> CSize -> IO CInt
58+
59+cpuHasRdRand :: IO Bool
60+cpuHasRdRand = (/= 0) `fmap` c_cpu_has_rdrand
3261#endif
3362
34−import qualified Data.ByteString as B
35−import Control.Exception (bracket)
63+data CryptHandle
64+ = CH Word32
65+#ifdef HAVE_RDRAND
66+ | UseRdRand
67+#endif
3668
37−-- |Get a specific number of bytes of cryptographically
38−-- secure random data using the *system-specific* sources.
39−-- (As of 0.4. Versions <0.4 mixed system and hardware sources)
40−--
41−-- The returned random value is considered cryptographically secure but not true entropy.
42−--
43−-- On some platforms this requires a file handle which can lead to resource
44−-- exhaustion in some situations.
45−getEntropy :: Int -- ^ Number of bytes
46− -> IO B.ByteString
47−getEntropy = bracket openHandle closeHandle . flip hGetEntropy
48−
49−-- |Get a specific number of bytes of cryptographically
50−-- secure random data using a supported *hardware* random bit generator.
51−--
52−-- If there is no hardware random number generator then @Nothing@ is returned.
53−-- If any call returns non-Nothing then it should never be @Nothing@ unless
54−-- there has been a hardware failure.
55−--
56−-- If trust of the CPU allows it and no context switching is important,
57−-- a bias to the hardware rng with system rng as fall back is trivial:
58−--
59−-- @
60−-- let fastRandom nr = maybe (getEntropy nr) pure =<< getHardwareEntropy nr
61−-- @
62−--
63−-- The old, @<0.4@, behavior is possible using @xor@ from 'Data.Bits':
69+-- Define the constants we need from WinCrypt.h
70+msDefProv :: String
71+msDefProv = "Microsoft Base Cryptographic Provider v1.0"
72+provRSAFull :: Word32
73+provRSAFull = fromIntegral 1
74+cryptVerifyContext :: Word32
75+cryptVerifyContext = fromIntegral 0xF0000000
76+
77+-- Declare the required CryptoAPI imports
78+foreign import stdcall unsafe "CryptAcquireContextA"
79+ c_cryptAcquireCtx :: Ptr Word32 -> CString -> CString -> Word32 -> Word32 -> IO Int32
80+foreign import stdcall unsafe "CryptGenRandom"
81+ c_cryptGenRandom :: Word32 -> Word32 -> Ptr Word8 -> IO Int32
82+foreign import stdcall unsafe "CryptReleaseContext"
83+ c_cryptReleaseCtx :: Word32 -> Word32 -> IO Int32
84+
85+cryptAcquireCtx :: IO Word32
86+cryptAcquireCtx =
87+ alloca $ \handlePtr ->
88+ withCString msDefProv $ \provName -> do
89+ stat <- c_cryptAcquireCtx handlePtr nullPtr provName (fromIntegral 1) (fromIntegral cryptVerifyContext)
90+ if (toBool stat)
91+ then peek handlePtr
92+ else fail "c_cryptAcquireCtx"
93+
94+cryptGenRandom :: Word32 -> Int -> IO B.ByteString
95+cryptGenRandom h i =
96+ BI.create i $ \c_buffer -> do
97+ stat <- c_cryptGenRandom (fromIntegral h) (fromIntegral i) c_buffer
98+ if (toBool stat)
99+ then return ()
100+ else fail "c_cryptGenRandom"
101+
102+cryptReleaseCtx :: Word32 -> IO ()
103+cryptReleaseCtx h = do
104+ stat <- c_cryptReleaseCtx h 0
105+ if (toBool stat)
106+ then return ()
107+ else fail "c_cryptReleaseCtx"
108+
109+-- |Inefficiently get a specific number of bytes of cryptographically
110+-- secure random data using the system-specific facilities.
64111--
65−-- @
66−-- let oldRandom nr =
67−-- do hwRnd <- maybe (replicate nr 0) BS.unpack <$> getHardwareEntropy nr
68−-- sysRnd <- BS.unpack <$> getEntropy nr
69−-- pure $ BS.pack $ zipWith xor sysRnd hwRnd
70−-- @
112+-- This function will return zero bytes
113+-- on platforms without a secure RNG!
114+getEntropy :: Int -> IO B.ByteString
115+getEntropy n = do
116+#ifdef HAVE_RDRAND
117+ b <- cpuHasRdRand
118+ if b then hGetEntropy UseRdRand n
119+ else do
120+#endif
121+ h <- cryptAcquireCtx
122+ bs <- cryptGenRandom h n
123+ let !bs' = bs
124+ cryptReleaseCtx h
125+ return bs'
126+
127+-- |Open a handle from which random data can be read
128+openHandle :: IO CryptHandle
129+openHandle = do
130+#ifdef HAVE_RDRAND
131+ b <- cpuHasRdRand
132+ if b then return UseRdRand
133+ else do
134+#endif
135+ liftM CH cryptAcquireCtx
136+
137+-- |Close the `CryptHandle`
138+closeHandle (CH h) = cryptReleaseCtx h
139+
140+-- |Read from `CryptHandle`
141+hGetEntropy :: CryptHandle -> Int -> IO B.ByteString
142+hGetEntropy (CH h) = cryptGenRandom h
143+#ifdef HAVE_RDRAND
144+hGetEntropy UseRdRand =
145+ B.create n $ \ptr -> do
146+ r <- c_get_rand_bytes (castPtr ptr) (fromIntegral n)
147+ when (r /= 0)
148+ (fail "RDRand failed to gather entropy")
149+#endif
150+
151+#else
152+{- Not windows, assuming nix with a /dev/urandom -}
153+import Foreign.Ptr
154+
155+source :: FilePath
156+source = "/dev/urandom"
157+
158+-- |Handle for manual resource mangement
159+data CryptHandle
160+ = CH Fd
161+#ifdef HAVE_RDRAND
162+ | UseRdRand
163+#endif
164+
165+-- |Open a `CryptHandle`
166+openHandle :: IO CryptHandle
167+openHandle = do
168+#ifdef HAVE_RDRAND
169+ b <- cpuHasRdRand
170+ if b then return UseRdRand
171+ else do
172+#endif
173+ liftM CH (openFd source ReadOnly Nothing defaultFileFlags)
174+
175+-- |Close the `CryptHandle`
176+closeHandle :: CryptHandle -> IO ()
177+closeHandle (CH h) = closeFd h
178+#ifdef HAVE_RDRAND
179+closeHandle UseRdRand = return ()
180+#endif
181+
182+fdReadBS :: Fd -> Int -> IO B.ByteString
183+fdReadBS fd n = do
184+ allocaBytes n $ \buf -> do
185+ rc <- fdReadBuf fd buf (fromIntegral n)
186+ case rc of
187+ 0 -> ioError (ioeSetErrorString (mkIOError eofErrorType "fdRead" Nothing Nothing) "EOF")
188+ n' -> B.packCStringLen (castPtr buf, fromIntegral n')
189+
190+-- |Read random data from a `CryptHandle`
191+hGetEntropy :: CryptHandle -> Int -> IO B.ByteString
192+hGetEntropy (CH h) = fdReadBS h
193+#ifdef HAVE_RDRAND
194+hGetEntropy UseRdRand = \n -> do
195+ B.create n $ \ptr -> do
196+ r <- c_get_rand_bytes (castPtr ptr) (fromIntegral n)
197+ when (r /= 0)
198+ (fail "RDRand failed to gather entropy")
199+#endif
200+
201+#ifdef HAVE_RDRAND
202+foreign import ccall unsafe "cpu_has_rdrand"
203+ c_cpu_has_rdrand :: IO CInt
204+
205+foreign import ccall unsafe "get_rand_bytes"
206+ c_get_rand_bytes :: Ptr CUChar -> CSize -> IO CInt
207+
208+cpuHasRdRand :: IO Bool
209+cpuHasRdRand = (/= 0) `fmap` c_cpu_has_rdrand
210+#endif
211+
212+-- |Inefficiently get a specific number of bytes of cryptographically
213+-- secure random data using the system-specific facilities.
71214--
72−-- A less maliable mixing can be accomplished by replacing `xor` with a
73−-- composition of concat and cryptographic hash.
74−getHardwareEntropy :: Int -- ^ Number of bytes
75− -> IO (Maybe B.ByteString)
76−getHardwareEntropy = hardwareRandom
215+-- Use '/dev/urandom' on *nix and CryptAPI when on Windows. In short,
216+-- this entropy is considered "cryptographically secure" but not true
217+-- entropy.
218+getEntropy :: Int -> IO B.ByteString
219+getEntropy n = do
220+ h <- openHandle
221+ e <- hGetEntropy h n
222+ closeHandle h
223+ return e
224+#endif
225+{- OS Test -}