Description
Hello,
I have an importante issue.
What happened?
When the MQTT Forwarder deserialize JoinRequest Frame from Semtech UDP GWMP Frame, the MIC code is badly decoded.
For exemple the Semtech UDP GWMP JoinRequest have this MIC code [1 192 29 90] but after decoding by MQTT Forwarder have this [1 192 28 90].
All my JoinRequest with MQTT Packet Forwarder are in MIC Error.
I am sur the problem appears during json deserialization, especially when decoding the payload in base64.
How I found?
I added in code a debug print (only for me), before and After this line https://github.com/chirpstack/chirpstack-mqtt-forwarder/blob/8b2ed3d2a2bc1aab8d11a6a78a2d09929be983b9/src/backend/semtech_udp/mod.rs#L342C5-L342C51
Like this.
debug!("--- RAW UPLINK --- {:?}", data);
let pl = structs::PushData::from_slice(data)?;
debug!("--- DECODED PAYLOAD --- {:?}", pl.payload);And I obtained this :
RAW UDP GWMP Frame :
7b 22 72 78 70 6b 22 3a 5b 7b 22 6a 76 65 72 22 3a 31 2c 22 74 6d 73 74 22 3a 38 36 33 34 32 32 31 33 2c 22 63 68 61 6e 22 3a 37 2c 22 72 66 63 68 22 3a 31 2c 22 66 72 65 71 22 3a 38 36 38 2e 35 30 30 30 30 30 2c 22 6d 69 64 22 3a 20 30 2c 22 73 74 61 74 22 3a 31 2c 22 6d 6f 64 75 22 3a 22 4c 4f 52 41 22 2c 22 64 61 74 72 22 3a 22 53 46 31 32 42 57 31 32 35 22 2c 22 63 6f 64 72 22 3a 22 34 2f 35 22 2c 22 72 73 73 69 73 22 3a 2d 35 32 2c 22 6c 73 6e 72 22 3a 36 2e 32 2c 22 66 6f 66 66 22 3a 2d 37 34 37 36 2c 22 72 73 73 69 22 3a 2d 35 31 2c 22 73 69 7a 65 22 3a 32 33 2c 22 64 61 74 61 22 3a 22 41 41 49 41 41 41 44 77 37 4a 41 41 2b 52 30 78 46 67 48 73 6b 41 41 6c 4c 77 48 41 48 56 6f 3d 22 7d 5d 7d
Manual decoding I optain this Payload in JSON
{"rxpk":[{"jver":1,"tmst":86342213,"chan":7,"rfch":1,"freq":868.500000,"mid": 0,"stat":1,"modu":"LORA","datr":"SF12BW125","codr":"4/5","rssis":-52,"lsnr":6.2,"foff":-7476,"rssi":-51,"size":23,"data":"AAIAAADw7JAA+R0xFgHskAAlLwHAHVo="}]}This LoRaWAN DATA
AAIAAADw7JAA+R0xFgHskAAlLwHAHVo=
00 02 00 00 00 f0 ec 90 00 f9 1d 31 16 01 ec 90 00 25 2f 01 c0 1d 5a
Contain this MIC
MIC : [1 192 29 90], 01c01d5a
But after let pl = structs::PushData::from_slice(data)?;
When MQTT Forwarder deserialize the RAW UDP GWMP and decode the DATA of Payload Frame I obtaine this LoRaWAN Frame
00 02 00 00 00 f0 ec 90 00 f9 1d 31 16 01 ec 90 00 25 2f 01 c0 1c 5a
MIC : [1 192 28 90], 01c01c5a
The mic code does not correspond to the UDP frame.
GOOD 01c01d5a, BAD 01c01c5a
Material
Gateway : RAK7268CV2
uname : Linux RAK7268CV2 5.4.154 #0 Fri Nov 24 07:30:08 2023 mips GNU/Linux
cpuinfo :
system type : MediaTek MT7628AN ver:1 eco:2
machine : Rakwireless RAK636
processor : 0
cpu model : MIPS 24KEc V5.5
BogoMIPS : 385.02
wait instruction : yes
microsecond timers : yes
tlb_entries : 32
extra interrupt vector : yes
hardware watchpoint : yes, count: 4, address/irw mask: [0x0ffc, 0x0ffc, 0x0ffb, 0x0ffb]
isa : mips1 mips2 mips32r1 mips32r2
ASEs implemented : mips16 dsp
Options implemented : tlb 4kex 4k_cache prefetch mcheck ejtag llsc pindexed_dcache userlocal vint perf_cntr_intr_bit perf
shadow register sets : 1
kscratch registers : 0
package : 0
core : 0
VCED exceptions : not available
VCEI exceptions : not available
OS : WisGateOS_2.2.1_RAK based on OpenWRT 21.2
Toolchain : make dist-mipsel-unknown-linux-musl