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SN_Decode_PublishResp: reject total_len not matching fixed layout #543

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SN_Decode_PublishResp: reject total_len not matching fixed layout #543

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15 changes: 15 additions & 0 deletions src/mqtt_sn_packet.c
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Original file line number Diff line number Diff line change
Expand Up @@ -1313,6 +1313,21 @@ int SN_Decode_PublishResp(byte* rx_buf, int rx_buf_len, byte type,
return MQTT_TRACE_ERROR(MQTT_CODE_ERROR_OUT_OF_BUFFER);
}

/* MQTT-SN: PUBACK is fixed at 7 octets (Length + MsgType + TopicID(2) +
* MsgID(2) + ReturnCode); PUBREC, PUBREL and PUBCOMP are fixed at 4
* octets (Length + MsgType + MsgID(2)). Any other total_len cannot
* cover the bytes the function still has to read - notably the
* *rx_payload++ message-type read below - so reject the frame before
* that read walks past the caller-supplied bound. */
if (type == SN_MSG_TYPE_PUBACK) {
if (total_len != 7) {
return MQTT_TRACE_ERROR(MQTT_CODE_ERROR_MALFORMED_DATA);
}
}
else if (total_len != 4) {
return MQTT_TRACE_ERROR(MQTT_CODE_ERROR_MALFORMED_DATA);
}

/* Validate packet type */
rec_type = *rx_payload++;
if (rec_type != type) {
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