From 194f13eb22e2ec821f42592b98017a1d7df36a33 Mon Sep 17 00:00:00 2001
From: siddharth <s@ricketyspace.net>
Date: Tue, 12 Oct 2021 21:23:13 -0400
Subject: lib: add HmacSha1

---
 lib/sha1.go      | 25 ++++++++++++++++
 lib/sha1_test.go | 91 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 116 insertions(+)

diff --git a/lib/sha1.go b/lib/sha1.go
index 891ba83..fb81b92 100644
--- a/lib/sha1.go
+++ b/lib/sha1.go
@@ -236,3 +236,28 @@ func (s *Sha1) MacVerify(secret, msg, mac []byte) bool {
 	}
 	return false
 }
+
+// HMAC-SHA1.
+func HmacSha1(key, msg []byte) []byte {
+	// Initialize SHA-1 object.
+	sha1 := Sha1{}
+	sha1.Init([]uint32{})
+
+	// Modify key based on it's size.
+	if len(key) > 64 { // > blocksize (64 bytes)
+		sha1.Message(key)
+		key = sha1.Hash()
+	}
+	if len(key) < 64 { // < blocksize (64 bytes)
+		// Pad with zeroes up to 64 bytes.
+		key = append(key, make([]byte, 64-len(key))...)
+	}
+
+	// Outer padded key.
+	opk := FixedXORBytes(key, FillBytes(0x5c, 64))
+
+	// Inner padded key.
+	ipk := FixedXORBytes(key, FillBytes(0x36, 64))
+
+	return sha1.Mac(opk, sha1.Mac(ipk, msg))
+}
diff --git a/lib/sha1_test.go b/lib/sha1_test.go
index 71b1296..58c6e61 100644
--- a/lib/sha1_test.go
+++ b/lib/sha1_test.go
@@ -42,3 +42,94 @@ func TestSha1Hash(t *testing.T) {
 		t.Errorf("sha1 test 3 failed: %x != %s\n", h, e)
 	}
 }
+
+// Test cases from RFC 2202
+func TestHmacSha1(t *testing.T) {
+	// Test 1
+	k := FillBytes(0x0b, 20)
+	m := StrToBytes("Hi There")
+	h := HmacSha1(k, m)
+	e := "b617318655057264e28bc0b6fb378c8ef146be00" // Expected HMAC-SHA1
+	if BytesToHexStr(h) != e {
+		t.Errorf("hmac-sha1 test 1 failed: %x != %s\n", h, e)
+	}
+
+	// Test 2
+	k = StrToBytes("Jefe")
+	m = StrToBytes("what do ya want for nothing?")
+	h = HmacSha1(k, m)
+	e = "effcdf6ae5eb2fa2d27416d5f184df9c259a7c79" // Expected HMAC-SHA1
+	if BytesToHexStr(h) != e {
+		t.Errorf("hmac-sha1 test 2 failed: %x != %s\n", h, e)
+	}
+
+	// Test 3
+	k = FillBytes(0xaa, 20)
+	m = FillBytes(0xdd, 50)
+	h = HmacSha1(k, m)
+	e = "125d7342b9ac11cd91a39af48aa17b4f63f175d3" // Expected HMAC-SHA1
+	if BytesToHexStr(h) != e {
+		t.Errorf("hmac-sha1 test 3 failed: %x != %s\n", h, e)
+	}
+
+	// Test 4
+	k = []byte{
+		0x01, 0x02, 0x03, 0x04, 0x05, 0x06, 0x07, 0x08,
+		0x09, 0x0a, 0x0b, 0x0c, 0x0d, 0x0e, 0x0f, 0x10,
+		0x11, 0x12, 0x13, 0x14, 0x15, 0x16, 0x17, 0x18,
+		0x19,
+	}
+	m = FillBytes(0xcd, 50)
+	h = HmacSha1(k, m)
+	e = "4c9007f4026250c6bc8414f9bf50c86c2d7235da" // Expected HMAC-SHA1
+	if BytesToHexStr(h) != e {
+		t.Errorf("hmac-sha1 test 4 failed: %x != %s\n", h, e)
+	}
+
+	// Test 5
+	k = FillBytes(0x0c, 20)
+	m = StrToBytes("Test With Truncation")
+	h = HmacSha1(k, m)
+	e = "4c1a03424b55e07fe7f27be1d58bb9324a9a5a04" // Expected HMAC-SHA1
+	if BytesToHexStr(h) != e {
+		t.Errorf("hmac-sha1 test 5 failed: %x != %s\n", h, e)
+	}
+
+	// Test 6
+	k = FillBytes(0xaa, 80)
+	m = StrToBytes("Test Using Larger Than Block-Size Key - Hash Key First")
+	h = HmacSha1(k, m)
+	e = "aa4ae5e15272d00e95705637ce8a3b55ed402112" // Expected HMAC-SHA1
+	if BytesToHexStr(h) != e {
+		t.Errorf("hmac-sha1 test 6 failed: %x != %s\n", h, e)
+	}
+
+	// Test 7
+	k = FillBytes(0xaa, 80)
+	m = StrToBytes("Test Using Larger Than Block-Size Key and")
+	m = append(m, StrToBytes(" Larger Than One Block-Size Data")...)
+	h = HmacSha1(k, m)
+	e = "e8e99d0f45237d786d6bbaa7965c7808bbff1a91" // Expected HMAC-SHA1
+	if BytesToHexStr(h) != e {
+		t.Errorf("hmac-sha1 test 7 failed: %x != %s\n", h, e)
+	}
+
+	// Test 8
+	k = FillBytes(0xaa, 80)
+	m = StrToBytes("Test Using Larger Than Block-Size Key - Hash Key First")
+	h = HmacSha1(k, m)
+	e = "aa4ae5e15272d00e95705637ce8a3b55ed402112" // Expected HMAC-SHA1
+	if BytesToHexStr(h) != e {
+		t.Errorf("hmac-sha1 test 8 failed: %x != %s\n", h, e)
+	}
+
+	// Test 9
+	k = FillBytes(0xaa, 80)
+	m = StrToBytes("Test Using Larger Than Block-Size Key and Larger")
+	m = append(m, StrToBytes(" Than One Block-Size Data")...)
+	h = HmacSha1(k, m)
+	e = "e8e99d0f45237d786d6bbaa7965c7808bbff1a91" // Expected HMAC-SHA1
+	if BytesToHexStr(h) != e {
+		t.Errorf("hmac-sha1 test 9 failed: %x != %s\n", h, e)
+	}
+}
-- 
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