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| -rw-r--r-- | lib/sha1.go | 209 |
1 files changed, 209 insertions, 0 deletions
diff --git a/lib/sha1.go b/lib/sha1.go new file mode 100644 index 0000000..3596160 --- /dev/null +++ b/lib/sha1.go @@ -0,0 +1,209 @@ +// Copyright © 2021 rsiddharth <s@ricketyspace.net> +// SPDX-License-Identifier: ISC + +package lib + +// SHA-1 implementation. +// Reference https://csrc.nist.gov/publications/detail/fips/180/4/final + +// Initial hash value. +var sha1IHashValue []uint32 = []uint32{ + 0x67452301, + 0xefcdab89, + 0x98badcfe, + 0x10325476, + 0xc3d2e1f0, +} + +// (a + b + ...) mod 2^32 +func sha1Add(n ...uint32) uint32 { + sum := uint64(0) + for _, v := range n { + sum += uint64(v) + } + return uint32(sum & 0xFFFFFFFF) +} + +// Circular Right Shift +func sha1Rotr(x uint32, n uint) uint32 { + return (x >> n) | (x << (32 - n)) +} + +// Circular Left Shift +func sha1Rotl(x uint32, n uint) uint32 { + return (x << n) | (x >> (32 - n)) +} + +// SHA-1 - Function f_t(x, y, z) +func sha1FT(t int, x, y, z uint32) uint32 { + switch { + case t <= 19: + return (x & y) ^ (^x & z) + case t >= 20 && t <= 39: + return x ^ y ^ z + case t >= 40 && t <= 59: + return (x & y) ^ (x & z) ^ (y & z) + case t >= 60 && t <= 79: + return x ^ y ^ z + default: + return uint32(0) + } +} + +// SHA-1 - Constant K_t +func sha1KT(t int) uint32 { + switch { + case t <= 19: + return uint32(0x5a827999) + case t >= 20 && t <= 39: + return uint32(0x6ed9eba1) + case t >= 40 && t <= 59: + return uint32(0x8f1bbcdc) + case t >= 60 && t <= 79: + return uint32(0xca62c1d6) + default: + return uint32(0) + } +} + +// SHA-1 - Pad message such that its length is a multiple of 512. +func sha1Pad(m []byte) []byte { + l := len(m) * 8 // msg size in bits + + // Reckon value of `k` + k := 0 + for ((l + 1 + k) % 512) != 448 { + k += 1 + } + + // Initialize padded message + pm := make([]byte, len(m)) + copy(pm, m) + + // Add bit `1` as byte block. + pm = append(pm, 0x80) + f := 7 // unclaimed bits in last byte of `pm` + + // Add `k` bit `0`s + for i := 0; i < k; i++ { + if f == 0 { + pm = append(pm, 0x0) + f = 8 + } + f = f - 1 + } + + // Add `l` in a 64 bit block in `pm` + l64 := uint64(l) + b64 := make([]byte, 8) // last 64-bits + for i := 7; i >= 0; i-- { + // Get 8 last bits. + b64[i] = byte(l64 & 0xFF) + + // Get rid of the last 8 bits. + l64 = l64 >> 8 + } + pm = append(pm, b64...) + + return pm +} + +// Converts padded messages bytes `pm` into 512-bit message blocks. +// Each 512-bit block is an array of 16 32-bit words. +func sha1MessageBlocks(pm []byte) [][]uint32 { + // Break into 512-bit blocks + bs := BreakIntoBlocks(pm, 64) + + mbs := make([][]uint32, 0) // Message blocks. + for i := 0; i < len(bs); i++ { + ws := make([]uint32, 0) // 32-bit words. + + // Break 512-bit (64 bytes) into 32-bit words. + for j := 0; j < 64; j = j + 4 { + // Pack 4 bytes into a 32-bit word. + w := (uint32(bs[i][j])<<24 | + uint32(bs[i][j+1])<<16 | + uint32(bs[i][j+2])<<8 | + uint32(bs[i][j+3])) + ws = append(ws, w) + } + mbs = append(mbs, ws) + } + return mbs +} + +// Returns the message schedule W_t for message black `mb` +// The message schedule has 80 32-bit words. +func sha1MessageSchedule(mb []uint32) []uint32 { + // Message schedule. + w := make([]uint32, 0) + + // Generate message schedule. + for t := 0; t <= 79; t++ { + if t <= 15 { + w = append(w, mb[t]) + } else { + w = append(w, sha1Rotl(w[t-3]^w[t-8]^w[t-14]^w[t-16], 1)) + } + } + return w +} + +func Sha1(m []byte) []byte { + // Pad message. + pm := sha1Pad(m) + + // Break into message blocks. + mbs := sha1MessageBlocks(pm) + + // Initialize hash values. + h := make([]uint32, 5) + copy(h, sha1IHashValue) // Initial hash values. + + // Process each message block. + for _, mb := range mbs { + // Get message schedule. + w := sha1MessageSchedule(mb) + + // Initialize working variables. + a := h[0] + b := h[1] + c := h[2] + d := h[3] + e := h[4] + + for t := 0; t <= 79; t++ { + tmp := sha1Add(sha1Rotl(a, 5), sha1FT(t, b, c, d), + e, sha1KT(t), w[t]) + e = d + d = c + c = sha1Rotl(b, 30) + b = a + a = tmp + } + + // Compute intermediate hash values. + h[0] = sha1Add(a, h[0]) + h[1] = sha1Add(b, h[1]) + h[2] = sha1Add(c, h[2]) + h[3] = sha1Add(d, h[3]) + h[4] = sha1Add(e, h[4]) + } + + // Slurp sha1 digest from hash values. + d := make([]byte, 0) // sha1 digest + for i := 0; i < 5; i++ { + // Break 32-bit hash value into 4 bytes. + hb := make([]byte, 4) + for j := 3; j >= 0; j-- { + // Get last 8 bits. + hb[j] = byte(h[i] & 0xFF) + + // Get rid of last 8 bits. + h[i] = h[i] >> 8 + } + d = append(d, hb...) + } + + return d +} |