MQTT-SN fixes#550
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Pull request overview
This PR hardens MQTT-SN packet handling (especially CONNACK) by adding stricter length/bounds validation in MQTT-SN decoders and ensuring the client path uses the dedicated CONNACK decoder instead of trusting the last byte. It also introduces a standalone unit test binary that regression-tests these decoder guards.
Changes:
- Fix MQTT-SN CONNACK handling to decode/validate via
SN_Decode_ConnectAckrather than readingrx_buf[buf_len-1]. - Add additional declared-length lower-bound checks in
SN_Decode_Header,SN_Decode_GWInfo, andSN_Decode_Registerto prevent over-reads/underflows. - Add a new
tests/test_mqtt_sndecoder-focused unit test program (wired into Automake) plus.gitignoreentry.
Reviewed changes
Copilot reviewed 4 out of 5 changed files in this pull request and generated 2 comments.
Show a summary per file
| File | Description |
|---|---|
tests/test_mqtt_sn.c |
New standalone unit tests that construct MQTT-SN frames to validate decoder bounds checks and CONNACK behavior. |
tests/include.am |
Adds Automake rules to build/run the new tests/test_mqtt_sn program when BUILD_SN is enabled. |
src/mqtt_sn_packet.c |
Adds missing lower-bound validation and corrects GWINFO address-length computation for IND vs short headers. |
src/mqtt_sn_client.c |
Routes CONNACK handling through SN_Decode_ConnectAck for proper validation. |
.gitignore |
Ignores the new tests/test_mqtt_sn test binary. |
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| /* [len=8][type=REGISTER][topicId=0x0102][packetId=0x0304]['a']['b'][\0] */ | ||
| byte buf[9] = { 0x08, SN_MSG_TYPE_REGISTER, 0x01, 0x02, 0x03, 0x04, | ||
| 'a', 'b', 0x00 }; |
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| /* IND form: [IND][len=0x000A][type][topicId][packetId]['a']['b'][\0] */ | ||
| byte buf[11] = { SN_PACKET_LEN_IND, 0x00, 0x0A, SN_MSG_TYPE_REGISTER, | ||
| 0x01, 0x02, 0x03, 0x04, 'a', 'b', 0x00 }; |
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