add md5 hashing (#764)

hashing/md5/md5.go

@@ -0,0 +1,118 @@
+// md5.go
+// description: The MD5 hashing function as defined in RFC 1321.
+// author: Simon Waldherr
+// ref: https://datatracker.ietf.org/doc/html/rfc1321
+// see md5_test.go for testing
+
+package md5
+
+import (
+	"encoding/binary"
+)
+
+// Constants for MD5
+var (
+	s = [64]uint32{
+		7, 12, 17, 22, 7, 12, 17, 22, 7, 12, 17, 22, 7, 12, 17, 22,
+		5, 9, 14, 20, 5, 9, 14, 20, 5, 9, 14, 20, 5, 9, 14, 20,
+		4, 11, 16, 23, 4, 11, 16, 23, 4, 11, 16, 23, 4, 11, 16, 23,
+		6, 10, 15, 21, 6, 10, 15, 21, 6, 10, 15, 21, 6, 10, 15, 21,
+	}
+
+	K = [64]uint32{
+		0xd76aa478, 0xe8c7b756, 0x242070db, 0xc1bdceee,
+		0xf57c0faf, 0x4787c62a, 0xa8304613, 0xfd469501,
+		0x698098d8, 0x8b44f7af, 0xffff5bb1, 0x895cd7be,
+		0x6b901122, 0xfd987193, 0xa679438e, 0x49b40821,
+		0xf61e2562, 0xc040b340, 0x265e5a51, 0xe9b6c7aa,
+		0xd62f105d, 0x02441453, 0xd8a1e681, 0xe7d3fbc8,
+		0x21e1cde6, 0xc33707d6, 0xf4d50d87, 0x455a14ed,
+		0xa9e3e905, 0xfcefa3f8, 0x676f02d9, 0x8d2a4c8a,
+		0xfffa3942, 0x8771f681, 0x6d9d6122, 0xfde5380c,
+		0xa4beea44, 0x4bdecfa9, 0xf6bb4b60, 0xbebfbc70,
+		0x289b7ec6, 0xeaa127fa, 0xd4ef3085, 0x04881d05,
+		0xd9d4d039, 0xe6db99e5, 0x1fa27cf8, 0xc4ac5665,
+		0xf4292244, 0x432aff97, 0xab9423a7, 0xfc93a039,
+		0x655b59c3, 0x8f0ccc92, 0xffeff47d, 0x85845dd1,
+		0x6fa87e4f, 0xfe2ce6e0, 0xa3014314, 0x4e0811a1,
+		0xf7537e82, 0xbd3af235, 0x2ad7d2bb, 0xeb86d391,
+	}
+)
+
+// leftRotate rotates x left by n bits
+func leftRotate(x, n uint32) uint32 {
+	return (x << n) | (x >> (32 - n))
+}
+
+// pad pads the input message so that its length is congruent to 448 modulo 512
+func pad(message []byte) []byte {
+	originalLength := len(message) * 8
+	message = append(message, 0x80)
+	for (len(message)*8)%512 != 448 {
+		message = append(message, 0x00)
+	}
+
+	lengthBytes := make([]byte, 8)
+	binary.LittleEndian.PutUint64(lengthBytes, uint64(originalLength))
+	message = append(message, lengthBytes...)
+
+	return message
+}
+
+// Hash computes the MD5 hash of the input message
+func Hash(message []byte) [16]byte {
+	message = pad(message)
+
+	// Initialize MD5 state variables
+	a0, b0, c0, d0 := uint32(0x67452301), uint32(0xefcdab89), uint32(0x98badcfe), uint32(0x10325476)
+
+	// Process the message in successive 512-bit chunks
+	for i := 0; i < len(message); i += 64 {
+		chunk := message[i : i+64]
+		var M [16]uint32
+		for j := 0; j < 16; j++ {
+			M[j] = binary.LittleEndian.Uint32(chunk[j*4 : (j+1)*4])
+		}
+
+		// Initialize hash value for this chunk
+		A, B, C, D := a0, b0, c0, d0
+
+		// Main loop
+		for i := 0; i < 64; i++ {
+			var F, g uint32
+			if i < 16 {
+				F = (B & C) | ((^B) & D)
+				g = uint32(i)
+			} else if i < 32 {
+				F = (D & B) | ((^D) & C)
+				g = uint32((5*i + 1) % 16)
+			} else if i < 48 {
+				F = B ^ C ^ D
+				g = uint32((3*i + 5) % 16)
+			} else {
+				F = C ^ (B | (^D))
+				g = uint32((7 * i) % 16)
+			}
+			F = F + A + K[i] + M[g]
+			A = D
+			D = C
+			C = B
+			B = B + leftRotate(F, s[i])
+		}
+
+		// Add this chunk's hash to result so far
+		a0 += A
+		b0 += B
+		c0 += C
+		d0 += D
+	}
+
+	// Produce the final hash value (digest)
+	var digest [16]byte
+	binary.LittleEndian.PutUint32(digest[0:4], a0)
+	binary.LittleEndian.PutUint32(digest[4:8], b0)
+	binary.LittleEndian.PutUint32(digest[8:12], c0)
+	binary.LittleEndian.PutUint32(digest[12:16], d0)
+
+	return digest
+}

hashing/md5/md5_test.go

@@ -0,0 +1,42 @@
+// md5_test.go
+// description: Tests for the MD5 hashing function as defined in RFC 1321.
+// author: Simon Waldherr
+
+package md5
+
+import (
+	"encoding/hex"
+	"testing"
+)
+
+// Helper function to convert hash output to hex string for comparison
+func toHexString(hash [16]byte) string {
+	return hex.EncodeToString(hash[:])
+}
+
+// Test vectors for MD5 (from RFC 1321 and other known sources)
+var tests = []struct {
+	input    string
+	expected string
+}{
+	{"", "d41d8cd98f00b204e9800998ecf8427e"},
+	{"a", "0cc175b9c0f1b6a831c399e269772661"},
+	{"abc", "900150983cd24fb0d6963f7d28e17f72"},
+	{"message digest", "f96b697d7cb7938d525a2f31aaf161d0"},
+	{"abcdefghijklmnopqrstuvwxyz", "c3fcd3d76192e4007dfb496cca67e13b"},
+	{"ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789", "d174ab98d277d9f5a5611c2c9f419d9f"},
+	{"12345678901234567890123456789012345678901234567890123456789012345678901234567890", "57edf4a22be3c955ac49da2e2107b67a"},
+}
+
+// TestHash verifies that the Hash function produces the correct MD5 hash values
+func TestHash(t *testing.T) {
+	for _, tt := range tests {
+		t.Run(tt.input, func(t *testing.T) {
+			result := Hash([]byte(tt.input))
+			resultHex := toHexString(result)
+			if resultHex != tt.expected {
+				t.Errorf("MD5(%q) = %s; want %s", tt.input, resultHex, tt.expected)
+			}
+		})
+	}
+}