Merge pull request #339 from nasa/44-crypto_key_otar---fixed-iv-length

[#44] Removed magic numbers from OTAR

Author: Donnie-Ice

include/crypto_config.h

@@ -210,6 +210,7 @@
 #define SDLS_IV_LEN          12 /* bytes */
 #define SDLS_KEYV_KEY_ID_LEN 2  /* bytes */
 #define SDLS_KEY_LEN         32 /* bytes */
+#define SDLS_KEYID_LEN       2  /* bytes */
 
 // TC Behavior Defines
 #define TC_SDLS_EP_VCID \

src/core/crypto_key_mgmt.c

@@ -45,7 +45,7 @@ int32_t Crypto_Key_OTAR(void)
     int         y;
     int32_t     status = CRYPTO_LIB_SUCCESS;
     // uint16_t pdu_len = (uint16_t) sdls_frame.pdu.hdr.pdu_len[1] << 8 | sdls_frame.pdu.hdr.pdu_len[0];
-    int           pdu_keys = (sdls_frame.pdu.hdr.pdu_len - 30) / (2 + 32);
+    int           pdu_keys = (sdls_frame.pdu.hdr.pdu_len - SDLS_KEYID_LEN - SDLS_IV_LEN - MAC_SIZE) / (SDLS_KEYID_LEN + SDLS_KEY_LEN);
     int           w;
     crypto_key_t *ekp = NULL;
 
@@ -76,7 +76,7 @@ int32_t Crypto_Key_OTAR(void)
         return status;
     }
 
-    for (count = 2; count < (2 + 12); count++)
+    for (count = 2; count < (2 + SDLS_IV_LEN); count++)
     { // Initialization Vector
         packet.iv[count - 2] = sdls_frame.pdu.data[count];
 #ifdef DEBUG
@@ -85,7 +85,7 @@ int32_t Crypto_Key_OTAR(void)
     }
 
     count = sdls_frame.pdu.hdr.pdu_len - MAC_SIZE;
-    for (w = 0; w < 16; w++)
+    for (w = 0; w < MAC_SIZE; w++)
     { // MAC
         packet.mac[w] = sdls_frame.pdu.data[count + w];
 #ifdef DEBUG
@@ -101,7 +101,7 @@ int32_t Crypto_Key_OTAR(void)
 
     uint8_t ecs = CRYPTO_CIPHER_AES256_GCM;
     status      = cryptography_if->cryptography_aead_decrypt(&(sdls_frame.pdu.data[14]), // plaintext output
-                                                             (size_t)(pdu_keys * (2 + SDLS_KEY_LEN)), // length of data
+                                                             (size_t)(pdu_keys * (SDLS_KEYID_LEN + SDLS_KEY_LEN)), // length of data
                                                              NULL,             // in place decryption
                                                              0,                // in data length
                                                              &(ekp->value[0]), // key