Add 3DES CMAC for ARM

armsrc/Makefile

@@ -153,7 +153,8 @@ THUMBSRC = start.c \
     clocks.c \
     hfsnoop.c \
     generator.c \
-    cmac_calc.c
+    cmac_calc.c \
+    cmac_3des.c
 
 
 # These are to be compiled in ARM mode

armsrc/cmac_3des.c

@@ -0,0 +1,126 @@
+//-----------------------------------------------------------------------------
+// Copyright (C) Aaron Tulino - December 2025
+// Copyright (C) Christian Herrmman, Iceman - October 2025
+// Copyright (C) Proxmark3 contributors. See AUTHORS.md for details.
+//
+// This program is free software: you can redistribute it and/or modify
+// it under the terms of the GNU General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// This program is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+//
+// See LICENSE.txt for the text of the license.
+//-----------------------------------------------------------------------------
+// Calculate CMAC 3DES
+//-----------------------------------------------------------------------------
+#include "cmac_3des.h"
+
+#include <string.h>
+#include "commonutil.h"
+#include "dbprint.h"
+#include "mbedtls/des.h"
+
+// XOR two 64-bit blocks
+static void xor_64(const uint8_t *a, const uint8_t *b, uint8_t *out) {
+    for (int i = 0; i < 8; i++) {
+        out[i] = a[i] ^ b[i];
+    }
+}
+
+// Left shift one bit in a 64-bit block
+static void left_shift_64(const uint8_t *input, uint8_t *output) {
+    uint8_t overflow = 0;
+    for (int i = 7; i >= 0; i--) {
+        output[i] = (input[i] << 1) | overflow;
+        overflow = (input[i] & 0x80) ? 1 : 0;
+    }
+}
+
+// Generate Subkeys K1 and K2
+static void generate_subkeys(mbedtls_des3_context *ctx, uint8_t *K1, uint8_t *K2) {
+    uint8_t L[8] = {0};
+
+    // Step 1: L = 3DES-ENC(0^64)
+    mbedtls_des3_crypt_ecb(ctx, L, L);
+
+    // Step 2: K1 = L << 1 (with conditional XOR with 0x1B)
+    left_shift_64(L, K1);
+    if (L[0] & 0x80) {
+        // If MSB is 1
+        K1[7] ^= 0x1B;
+    }
+
+    // Step 3: K2 = K1 << 1 (with conditional XOR with 0x1B)
+    left_shift_64(K1, K2);
+    if (K1[0] & 0x80) {
+        K2[7] ^= 0x1B;
+    }
+}
+
+// Pad the last block (adds 0x80 followed by zeros)
+static void padding(const uint8_t *lastb, uint8_t *pad, size_t len) {
+    memcpy(pad, lastb, len);
+    pad[len] = 0x80;
+    for (size_t i = len + 1; i < 16; i++) {
+        pad[i] = 0x00;
+    }
+}
+
+// CMAC implementation
+void des3_cmac(const uint8_t *key, size_t key_len, const uint8_t *input, size_t ilen, uint8_t output[8]) {
+    uint8_t last[8] = {0};
+    uint8_t X[8] = {0};
+    uint8_t Y[8] = {0};
+    uint8_t buffer[8] = {0};
+    uint8_t K1[8] = {0};
+    uint8_t K2[8] = {0};
+
+    int last_block_complete = (ilen % 8 == 0 && ilen != 0);
+
+    mbedtls_des3_context ctx;
+    mbedtls_des3_init(&ctx);
+    if (key_len == 16) {
+        mbedtls_des3_set2key_enc(&ctx, key);
+    } else if (key_len == 24) {
+        mbedtls_des3_set3key_enc(&ctx, key);
+    }
+
+    generate_subkeys(&ctx, K1, K2);
+
+    size_t n_blocks = (ilen + 7) / 8;
+
+    // prepare last block
+    if (n_blocks == 0) {
+        // if message is empty, CMAC is just MAC of padded block XOR K2
+        // since buffer is all zeros here.
+        n_blocks = 1;
+        buffer[0] = 0x80;
+        xor_64(buffer, K2, last);
+    } else {
+
+        const uint8_t *last_block = input + 8 * (n_blocks - 1);
+
+        if (last_block_complete) {
+            xor_64(last_block, K1, last);
+        } else {
+            padding(last_block, buffer, ilen % 8);
+            xor_64(buffer, K2, last);
+        }
+    }
+
+    // main loop
+    for (size_t i = 0; i < n_blocks - 1; i++) {
+        xor_64(X, input + 8 * i, Y);
+        mbedtls_des3_crypt_ecb(&ctx, Y, X);
+    }
+
+    // last block
+    xor_64(X, last, Y);
+    mbedtls_des3_crypt_ecb(&ctx, Y, output);
+    mbedtls_des3_free(&ctx);
+
+}

armsrc/cmac_3des.h

@@ -0,0 +1,29 @@
+//-----------------------------------------------------------------------------
+// Copyright (C) Aaron Tulino - December 2025
+// Copyright (C) Christian Herrmman, Iceman - October 2025
+// Copyright (C) Proxmark3 contributors. See AUTHORS.md for details.
+//
+// This program is free software: you can redistribute it and/or modify
+// it under the terms of the GNU General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// This program is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+//
+// See LICENSE.txt for the text of the license.
+//-----------------------------------------------------------------------------
+// Calculate CMAC 3DES
+//-----------------------------------------------------------------------------
+
+#ifndef __CMAC_3DES_H
+#define __CMAC_3DES_H
+
+
+#include "common.h"
+
+void des3_cmac(const uint8_t *key, size_t key_len, const uint8_t *input, size_t ilen, uint8_t output[8]);
+
+#endif