mirror of
https://github.com/cnlohr/lolra.git
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cnlohr
161 lines
4.1 KiB
C
161 lines
4.1 KiB
C
/*
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MIT License
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Copyright (c) 2024 Charles Lohr "CNLohr"
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Permission is hereby granted, free of charge, to any person obtaining a copy
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of this software and associated documentation files (the "Software"), to deal
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in the Software without restriction, including without limitation the rights
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to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
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copies of the Software, and to permit persons to whom the Software is
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furnished to do so, subject to the following conditions:
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The above copyright notice and this permission notice shall be included in all
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copies or substantial portions of the Software.
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THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
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IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
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FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
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AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
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LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
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OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
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SOFTWARE.
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*/
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#ifndef _LORAWAN_SIMPLE_H
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#define _LORAWAN_SIMPLE_H
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#include <string.h>
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#include <unistd.h>
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// Configuration needed for aes-cbc-cmac.h
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#define TINY_AES_C_IMPLEMENTATION
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#define TINY_AES_ECB 1
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#include "tiny-AES-c.h"
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#include "aes-cbc-cmac.h"
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static int GenerateLoRaWANPacket( uint8_t * raw_payload_with_b0, const uint8_t * inner_payload_raw, int inner_payload_len, const uint8_t * payload_key, const uint8_t * network_skey, const uint8_t * devaddress, int frame )
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{
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int i;
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uint8_t * raw_payload = raw_payload_with_b0 + 16;
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uint8_t * pl = raw_payload;
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struct AES_ctx payload_key_ctx;
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AES_init_ctx( &payload_key_ctx, payload_key );
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// MAC header
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// 010 Unconfirmed data uplink.
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// 000 RFU
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// 00 Major Version
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*(pl++) = ( 0b01000000 );
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// Frame header
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// Device address (4 bytes)
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memcpy( pl, devaddress, 4 );
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pl += 4;
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// Frame Control
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// MSB
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// 0 = ADR (cannot do rate adaptation)
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// 0 = Not confirming ADR.
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// 0 = ACK
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// 0 = Class B (we are not a class B device because we can't schedule downlinks)
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// 0000 = fopts length (no fopts)
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// LSB
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*(pl++) = 0b00000000;
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// Frame Count
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*(pl++) = frame;
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*(pl++) = frame>>8;
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// Frame Port
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*(pl++) = 1; // Port (1-223 are application specific)
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int padded_pad_length = ( inner_payload_len + AES_BLOCKLEN - 1 ) & (~(AES_BLOCKLEN-1));
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int nr_blocks = padded_pad_length / AES_BLOCKLEN;
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uint8_t pad[padded_pad_length];
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for( i = 0; i < nr_blocks; i++ )
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{
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// Add CMAC. Construct b0
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uint8_t * Ai = &pad[i*AES_BLOCKLEN];
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*(Ai++) = 0x01;
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*(Ai++) = 0;
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*(Ai++) = 0;
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*(Ai++) = 0;
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*(Ai++) = 0;
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*(Ai++) = 0; // Uplink = 0
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*(Ai++) = devaddress[0];
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*(Ai++) = devaddress[1];
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*(Ai++) = devaddress[2];
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*(Ai++) = devaddress[3];
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*(Ai++) = (frame>>0) & 0xff;
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*(Ai++) = (frame>>8) & 0xff;
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*(Ai++) = (frame>>16) & 0xff;
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*(Ai++) = (frame>>24) & 0xff;
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*(Ai++) = 0;
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*(Ai++) = i+1;
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}
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for( i = 0; i < nr_blocks; i++ )
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{
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AES_ECB_encrypt( &payload_key_ctx, &pad[i*AES_BLOCKLEN] );
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}
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// uint8_t * start_of_payload = pl;
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for( i = 0; i < inner_payload_len; i++ )
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{
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*(pl++) = pad[i] ^ inner_payload_raw[i];
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}
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int to_cmac_size = pl - raw_payload_with_b0;
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int length_of_frame_without_b0 = pl - raw_payload;
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uint8_t * b0 = raw_payload_with_b0;
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*(b0++) = 0x49;
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*(b0++) = 0x00;
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*(b0++) = 0x00;
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*(b0++) = 0x00;
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*(b0++) = 0x00;
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*(b0++) = 0x00;
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*(b0++) = devaddress[0];
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*(b0++) = devaddress[1];
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*(b0++) = devaddress[2];
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*(b0++) = devaddress[3];
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*(b0++) = (frame>>0) & 0xff;
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*(b0++) = (frame>>8) & 0xff;
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*(b0++) = (frame>>16) & 0xff;
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*(b0++) = (frame>>24) & 0xff;
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*(b0++) = 0x00;
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*(b0++) = length_of_frame_without_b0;
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uint8_t mac[AES_BLOCKLEN];
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//printf( "To CMAC: %d\n", to_cmac_size );
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//for ( i = 0; i < to_cmac_size; i++ )
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//{
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// printf( "%02x ", raw_payload_with_b0[i] );
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//}
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//printf( "\n" );
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AES_CMAC( network_skey, raw_payload_with_b0, to_cmac_size, mac );
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*(pl++) = mac[0];
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*(pl++) = mac[1];
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*(pl++) = mac[2];
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*(pl++) = mac[3];
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//printf( "MAC %02x%02x%02x%02x %02x%02x%02x%02x\n", mac[0], mac[1], mac[2], mac[3], mac[12], mac[13], mac[14], mac[15] );
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return pl - raw_payload_with_b0 - 16;
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}
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#endif
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