lib: move common hashing functions to hash.go

2 files changed, 72 insertions, 67 deletions

diff --git a/lib/hash.go b/lib/hash.go
new file mode 100644
index 0000000..f0f4625
--- /dev/null
+++ b/lib/hash.go
@@ -0,0 +1,71 @@
+// Copyright © 2021 rsiddharth <s@ricketyspace.net>
+// SPDX-License-Identifier: ISC
+
+package lib
+
+// Converts padded messages bytes `pm` into 512-bit message blocks.
+// Each 512-bit block is an array of 16 32-bit words.
+// It's assumed bit length of `pm` is a multiple of 512.
+func shaMessageBlocks(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 Merkle–Damgård padding in bytes for length of mesage `l`
+// bytes.
+func MDPadding(l int) []byte {
+	l = l * 8 // msg size in bits
+
+	// Reckon value of `k`
+	k := 0
+	for ((l + 1 + k) % 512) != 448 {
+		k += 1
+	}
+
+	// Initialize padding bytes
+	pbs := make([]byte, 0)
+
+	// Add bit `1` as byte block.
+	pbs = append(pbs, 0x80)
+	f := 7 // unclaimed bits in last byte of `pbs`
+
+	// Add `k` bit `0`s
+	for i := 0; i < k; i++ {
+		if f == 0 {
+			pbs = append(pbs, 0x0)
+			f = 8
+		}
+		f = f - 1
+	}
+
+	// Add `l` in a 64 bit block in `pbs`
+	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
+	}
+	pbs = append(pbs, b64...)
+
+	return pbs
+}
diff --git a/lib/sha1.go b/lib/sha1.go
index 3b648c8..5010bfb 100644
--- a/lib/sha1.go
+++ b/lib/sha1.go
@@ -72,30 +72,6 @@ func sha1KT(t int) uint32 {
 	}
 }
 
-// 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 {
@@ -147,7 +123,7 @@ func (s *Sha1) Hash() []byte {
 	pm := s.Pad()
 
 	// Break into message blocks.
-	mbs := sha1MessageBlocks(pm)
+	mbs := shaMessageBlocks(pm)
 
 	// Initialize hash values.
 	h := make([]uint32, 5)
@@ -213,45 +189,3 @@ func (s *Sha1) MacVerify(secret, msg, mac []byte) bool {
 	}
 	return false
 }
-
-// Returns Merkle–Damgård padding in bytes for length of mesage `l`
-// bytes.
-func MDPadding(l int) []byte {
-	l = l * 8 // msg size in bits
-
-	// Reckon value of `k`
-	k := 0
-	for ((l + 1 + k) % 512) != 448 {
-		k += 1
-	}
-
-	// Initialize padding bytes
-	pbs := make([]byte, 0)
-
-	// Add bit `1` as byte block.
-	pbs = append(pbs, 0x80)
-	f := 7 // unclaimed bits in last byte of `pbs`
-
-	// Add `k` bit `0`s
-	for i := 0; i < k; i++ {
-		if f == 0 {
-			pbs = append(pbs, 0x0)
-			f = 8
-		}
-		f = f - 1
-	}
-
-	// Add `l` in a 64 bit block in `pbs`
-	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
-	}
-	pbs = append(pbs, b64...)
-
-	return pbs
-}