Adding dkek procedures to wrap/unwrap.

Signed-off-by: Pol Henarejos <pol.henarejos@cttc.es>

CMakeLists.txt

@@ -52,6 +52,7 @@ target_sources(pico_hsm PUBLIC
         ${CMAKE_CURRENT_LIST_DIR}/src/rng/random.c
         ${CMAKE_CURRENT_LIST_DIR}/src/rng/neug.c
         ${CMAKE_CURRENT_LIST_DIR}/src/hsm/hash_utils.c
+        ${CMAKE_CURRENT_LIST_DIR}/src/hsm/dkek.c
         
         ${CMAKE_CURRENT_LIST_DIR}/mbedtls/library/sha256.c
         ${CMAKE_CURRENT_LIST_DIR}/mbedtls/library/aes.c

src/hsm/dkek.c

@@ -0,0 +1,129 @@
+/* 
+ * This file is part of the Pico HSM distribution (https://github.com/polhenarejos/pico-hsm).
+ * Copyright (c) 2022 Pol Henarejos.
+ * 
+ * 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, version 3.
+ *
+ * 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.
+ *
+ * You should have received a copy of the GNU General Public License 
+ * along with this program. If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#include <string.h>
+#include "stdlib.h"
+#include "pico/stdlib.h"
+#include "dkek.h"
+#include "hash_utils.h"
+#include "random.h"
+#include "sc_hsm.h"
+#include "mbedtls/md.h"
+#include "mbedtls/cmac.h"
+
+static uint8_t dkek[32];
+
+void init_dkek() {
+    memset(dkek, 0, sizeof(dkek));
+}
+
+void import_dkek_share(const uint8_t *share) {
+    for (int i = 0; i < 32; i++)
+        dkek[i] ^= share[i];
+}
+
+void dkek_kcv(uint8_t *kcv) { //kcv 8 bytes
+    uint8_t hsh[32];
+    hash256(dkek, sizeof(dkek), hsh);
+    memcpy(kcv, hsh, 8);
+}
+
+void dkek_kenc(uint8_t *kenc) { //kenc 32 bytes
+    uint8_t buf[32+4];
+    memcpy(buf, dkek, sizeof(dkek));
+    memcpy(buf, "\x0\x0\x0\x1", 4);
+    hash256(dkek, sizeof(dkek), kenc);
+}
+
+void dkek_kmac(uint8_t *kmac) { //kmac 32 bytes
+    uint8_t buf[32+4];
+    memcpy(buf, dkek, sizeof(dkek));
+    memcpy(buf, "\x0\x0\x0\x2", 4);
+    hash256(dkek, sizeof(dkek), kmac);
+}
+
+int dkek_encode_aes_key(uint8_t *key, int key_size, uint8_t *out, size_t *out_len) { //out has to be 93 bytes at least
+    if (key_size != 16 || key_size != 24 || key_size != 32)
+        return HSM_WRONG_DATA;
+    if (*out_len < 8+1+10+6+4+48+16)
+        return HSM_WRONG_LENGTH;
+    uint8_t kb[48]; //worst case (8+2+key_size+padding)
+    memset(kb, 0, sizeof(kb));
+    
+    uint8_t kenc[32];
+    memset(kenc, 0, sizeof(kenc));
+    dkek_kenc(kenc);
+    
+    uint8_t kcv[8];
+    memset(kcv, 0, sizeof(kcv));
+    dkek_kcv(kcv);
+    
+    uint8_t kmac[32];
+    memset(kmac, 0, sizeof(kmac));
+    dkek_kmac(kmac);
+    
+    int kb_len = 8+2+key_size;
+    int kb_len_pad = ((int)(kb_len/16))*16;
+    if (kb_len % 16 > 0)
+        kb_len_pad = ((int)(kb_len/16)+1)*16;
+    memcpy(kb, random_bytes_get(8), 8);
+    put_uint16_t(key_size, kb+8);
+    memcpy(kb+8+2, key, key_size);
+    if (kb_len < kb_len_pad) {
+        kb[kb_len] = 0x80;
+    }
+    int r = aes_encrypt(kenc, NULL, 32, kb, kb_len_pad);
+    if (r != HSM_OK)
+        return r;
+    
+    memset(out, 0, *out_len);
+    *out_len = 0;
+    uint8_t *aes_oid = "\x00\x08\x60\x86\x48\x01\x65\x03\x04\x01"; //2.16.840.1.101.3.4.1 (2+8)
+    uint8_t *aes_algo = "\x00\x04\x10\x11\x18\x99"; //(2+4)
+    
+    memcpy(out+*out_len, kcv, 8);
+    *out_len += 8;
+    
+    out[*out_len] = 15;
+    *out_len += 1;
+    
+    memcpy(out+*out_len, aes_oid, 10);
+    *out_len += 10;
+    
+    memcpy(out+*out_len, aes_algo, 6);
+    *out_len += 6;
+    
+    //add 4 zeros
+    *out_len += 4;
+    
+    memcpy(out+*out_len, kb, kb_len_pad);
+    *out_len += kb_len_pad;
+    
+    const mbedtls_cipher_info_t *cipher_info;
+    if (key_size == 16)
+        cipher_info = mbedtls_cipher_info_from_type(MBEDTLS_CIPHER_AES_128_ECB);
+    else if (key_size == 24)
+        cipher_info = mbedtls_cipher_info_from_type(MBEDTLS_CIPHER_AES_192_ECB);
+    else if (key_size == 32)
+        cipher_info = mbedtls_cipher_info_from_type(MBEDTLS_CIPHER_AES_256_ECB);
+    r = mbedtls_cipher_cmac(cipher_info, kmac, 256, out, *out_len, out+*out_len);
+    
+    *out_len += 16;
+    if (r != 0)
+        return r;
+    return HSM_OK;
+} 

src/hsm/dkek.h

@@ -0,0 +1,21 @@
+/* 
+ * This file is part of the Pico HSM distribution (https://github.com/polhenarejos/pico-hsm).
+ * Copyright (c) 2022 Pol Henarejos.
+ * 
+ * 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, version 3.
+ *
+ * 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.
+ *
+ * You should have received a copy of the GNU General Public License 
+ * along with this program. If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#ifndef _DKEK_H_
+#define _DKEK_H_
+
+#endif