/*
 * Copyright (c) 2004, 2013-2015 Galois, Inc.
 * Distributed under the terms of the BSD3 license (see LICENSE file)
 */

// Description of SHA1 at http://www.itl.nist.gov/fipspubs/fip180-4.htm

sha1 : {n} (width (8*n) <= 64) => [n][8] -> [160]
sha1 msg = sha1' pmsg
    where
        pmsg = pad(join(msg))

sha1' : {chunks} (fin chunks) => [chunks][512] -> [160]
sha1' pmsg = join (Hs!0)
  where 
    Hs = [[0x67452301, 0xefcdab89, 0x98badcfe, 0x10325476, 0xc3d2e1f0]] #
         [ block(H, split(M))
         | H <- Hs
         | M <- pmsg
         ]

/*
As a summary, a "1" followed by m "0"s followed by a 64-
   bit integer are appended to the end of the message to produce a
   padded message of length 512 * n.  The 64-bit integer is the length
   of the original message.  The padded message is then processed by the
   SHA-1 as n 512-bit blocks.
*/

pad : {msgLen,chunks}
     ( fin msgLen
     , 64 >= width msgLen                             // message width fits in a word
     , chunks     == (msgLen + 65 + 511) / 512
     )
     => [msgLen] -> [chunks][512]
pad msg = split (msg # [True] # (zero:[padding]) # (`msgLen:[64]))
    where type contentLen = msgLen + 65                      // message + header
          type padding    = (512 - contentLen % 512) % 512   // prettier if type #'s could be < 0

f : ([8], [32], [32], [32]) -> [32]
f (t, x, y, z) = 
       if (0 <= t)  && (t <= 19) then (x && y) ^ (~x && z)
        | (20 <= t) && (t <= 39) then x ^ y ^ z
        | (40 <= t) && (t <= 59) then (x && y) ^ (x && z) ^ (y && z)
        | (60 <= t) && (t <= 79) then x ^ y ^ z
        else error "f: t out of range"

Ks : [80][32]
Ks = [ 0x5a827999 | t <- [0..19]  ]
   # [ 0x6ed9eba1 | t <- [20..39] ]
   # [ 0x8f1bbcdc | t <- [40..59] ]
   # [ 0xca62c1d6 | t <- [60..79] ]

block : ([5][32], [16][32]) -> [5][32]
block ([H0, H1, H2, H3, H4], M) =
 [(H0+As@80), (H1+Bs@80), (H2+Cs@80), (H3+Ds@80), (H4+Es@80)]
  where 
    Ws : [80][32]
    Ws = M # [ (W3 ^ W8 ^ W14 ^ W16) <<< 1
             | W16 <- drop`{16 - 16} Ws
             | W14 <- drop`{16 - 14} Ws
             | W8  <- drop`{16 - 8}  Ws
             | W3  <- drop`{16 - 3}  Ws
             | t <- [16..79]
             ]
    As = [H0] # TEMP
    Bs = [H1] # As
    Cs = [H2] # [ B <<< 30 | B <- Bs ]
    Ds = [H3] # Cs
    Es = [H4] # Ds
    TEMP : [80][32]
    TEMP = [ (A <<< 5) + f(t, B, C, D) + E + W + K
           | A <- As | B <- Bs | C <- Cs | D <- Ds | E <- Es
           | W <- Ws | K <- Ks
           | t <- [0..79]
           ]


t0 = sha1 "" == 0xda39a3ee5e6b4b0d3255bfef95601890afd80709

// Sample messages and their digests from FIPS180-1 appendix.

t1 = sha1 "abc" == 0xA9993E364706816ABA3E25717850C26C9CD0D89D
t2 = sha1 "abcdbcdecdefdefgefghfghighijhijkijkljklmklmnlmnomnopnopq" ==
     0x84983E441C3BD26EBAAE4AA1F95129E5E54670F1
t3 = sha1 [ 'a' | i <- [1..1000000] ] ==
     0x34AA973CD4C4DAA4F61EEB2BDBAD27316534016F

property testsPass = [t0, t1, t2, t3] == ~zero