From 9133601088f5fe10923178677287644f66fa78f3 Mon Sep 17 00:00:00 2001
From: Thomas Florian <thomas.florian@tum.de>
Date: Wed, 29 Jun 2022 19:10:43 +0200
Subject: [PATCH] fix: error in reference

---
 Implementierung/src/md2.c | 39 +++++++++++++++++++++------------------
 1 file changed, 21 insertions(+), 18 deletions(-)

diff --git a/Implementierung/src/md2.c b/Implementierung/src/md2.c
index 03e0b79..04b3764 100644
--- a/Implementierung/src/md2.c
+++ b/Implementierung/src/md2.c
@@ -5,23 +5,23 @@
 
 // Source: https://datatracker.ietf.org/doc/html/rfc1319
 static unsigned char PI_SUBST[256] = {
-    41,  46,  67,  201, 162, 216, 124, 1,   61,  54,  84,  161, 236, 240, 6,
-    19,  98,  167, 5,   243, 192, 199, 115, 140, 152, 147, 43,  217, 188, 76,
-    130, 202, 30,  155, 87,  60,  253, 212, 224, 22,  103, 66,  111, 24,  138,
-    23,  229, 18,  190, 78,  196, 214, 218, 158, 222, 73,  160, 251, 245, 142,
-    187, 47,  238, 122, 169, 104, 121, 145, 21,  178, 7,   63,  148, 194, 16,
-    137, 11,  34,  95,  33,  128, 127, 93,  154, 90,  144, 50,  39,  53,  62,
-    204, 231, 191, 247, 151, 3,   255, 25,  48,  179, 72,  165, 181, 209, 215,
-    94,  146, 42,  172, 86,  170, 198, 79,  184, 56,  210, 150, 164, 125, 182,
-    118, 252, 107, 226, 156, 116, 4,   241, 69,  157, 112, 89,  100, 113, 135,
-    32,  134, 91,  207, 101, 230, 45,  168, 2,   27,  96,  37,  173, 174, 176,
-    185, 246, 28,  70,  97,  105, 52,  64,  126, 15,  85,  71,  163, 35,  221,
-    81,  175, 58,  195, 92,  249, 206, 186, 197, 234, 38,  44,  83,  13,  110,
-    133, 40,  132, 9,   211, 223, 205, 244, 65,  129, 77,  82,  106, 220, 55,
-    200, 108, 193, 171, 250, 36,  225, 123, 8,   12,  189, 177, 74,  120, 136,
-    149, 139, 227, 99,  232, 109, 233, 203, 213, 254, 59,  0,   29,  57,  242,
-    239, 183, 14,  102, 88,  208, 228, 166, 119, 114, 248, 235, 117, 75,  10,
-    49,  68,  80,  180, 143, 237, 31,  26,  219, 153, 141, 51,  159, 17,  131,
+    41, 46, 67, 201, 162, 216, 124, 1, 61, 54, 84, 161, 236, 240, 6,
+    19, 98, 167, 5, 243, 192, 199, 115, 140, 152, 147, 43, 217, 188, 76,
+    130, 202, 30, 155, 87, 60, 253, 212, 224, 22, 103, 66, 111, 24, 138,
+    23, 229, 18, 190, 78, 196, 214, 218, 158, 222, 73, 160, 251, 245, 142,
+    187, 47, 238, 122, 169, 104, 121, 145, 21, 178, 7, 63, 148, 194, 16,
+    137, 11, 34, 95, 33, 128, 127, 93, 154, 90, 144, 50, 39, 53, 62,
+    204, 231, 191, 247, 151, 3, 255, 25, 48, 179, 72, 165, 181, 209, 215,
+    94, 146, 42, 172, 86, 170, 198, 79, 184, 56, 210, 150, 164, 125, 182,
+    118, 252, 107, 226, 156, 116, 4, 241, 69, 157, 112, 89, 100, 113, 135,
+    32, 134, 91, 207, 101, 230, 45, 168, 2, 27, 96, 37, 173, 174, 176,
+    185, 246, 28, 70, 97, 105, 52, 64, 126, 15, 85, 71, 163, 35, 221,
+    81, 175, 58, 195, 92, 249, 206, 186, 197, 234, 38, 44, 83, 13, 110,
+    133, 40, 132, 9, 211, 223, 205, 244, 65, 129, 77, 82, 106, 220, 55,
+    200, 108, 193, 171, 250, 36, 225, 123, 8, 12, 189, 177, 74, 120, 136,
+    149, 139, 227, 99, 232, 109, 233, 203, 213, 254, 59, 0, 29, 57, 242,
+    239, 183, 14, 102, 88, 208, 228, 166, 119, 114, 248, 235, 117, 75, 10,
+    49, 68, 80, 180, 143, 237, 31, 26, 219, 153, 141, 51, 159, 17, 131,
     20};
 
 void printBuf(size_t len, uint8_t buf[len]) {
@@ -37,7 +37,8 @@ void md2_checksum(size_t len, uint8_t* buf) {
   for (int i = 0; i < len / 16; i++) {
     for (int j = 0; j < 16; j++) {
       u_int8_t c = buf[i * 16 + j];
-      l = buf[len + j] = PI_SUBST[c ^ l];
+      // reference is wrong. It says: Set C[j] to S[c xor L]. But it should be:
+      l = buf[len + j] ^= PI_SUBST[c ^ l];
     }
   }
 }
@@ -54,6 +55,8 @@ void md2_hash(size_t len, const uint8_t buf[len], uint8_t out[16]) {
   uint8_t* newBuf = calloc(len + 16, sizeof(uint8_t));
   memcpy(newBuf, buf, len - paddingNeeded);
 
+  printBuf(len + 16, newBuf);
+
   while (paddingNeeded > 0) {
     newBuf[len - paddingNeeded] = originalPadding;
     paddingNeeded--;