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Incorrect remaining length is calculated when topic contains utf-8-3 or utf-8-4 characters in SUBSCRIBE/PUBLISH packets #90

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Eason010212 opened this issue Aug 27, 2021 · 3 comments
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Incorrect remaining length is calculated when topic contains utf-8-3 or utf-8-4 characters in SUBSCRIBE/PUBLISH packets #90

Eason010212 opened this issue Aug 27, 2021 · 3 comments

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@Eason010212
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Eason010212 commented Aug 27, 2021 •
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Current version of adafruit_minimqtt.py uses len() method to calculate a packet's remaining length, for example：

Adafruit_CircuitPython_MiniMQTT/adafruit_minimqtt/adafruit_minimqtt.py

Line 671 in c55a484

packet_length += sum(len(topic) for topic, qos in topics)

Adafruit_CircuitPython_MiniMQTT/adafruit_minimqtt/adafruit_minimqtt.py

Line 592 in c55a484

remaining_length = 2 + len(msg) + len(topic)

As shown above, strings are measured instead of UTF-8 bytes. When a topic only contains English characters, numbers and punctuation marks, the calculation result is correct; However, when it contains some utf-8-3 or utf-8-4 characters (such as Chinese characters) , an incorrect calculation result of remaining length will be obtained. For example, the actual encoding length of "中文" should be 6, while the length calculated by len() is 2. As a result, such packets will be rejected by any MQTT server.

In MQTT protocol, there is no restriction on utf-8-3 or utf-8-4 characters, so I think this issue is probably a bug that needs to be fixed.

At present, in the application I developed, I rewrite the len() method to temporarily solve this problem, but I still hope that the developers of this library can make official bug fixes.

Thank you very much.
@Eason010212 Eason010212 changed the title Incorrect variable length field in SUBSCRIBE/PUBLISH packets are generated when topic contains utf-8-3 or utf-8-4 characters Incorrect variable length in SUBSCRIBE/PUBLISH packet is calculated when topic contains utf-8-3 or utf-8-4 characters Aug 27, 2021
@Eason010212 Eason010212 changed the title Incorrect variable length in SUBSCRIBE/PUBLISH packet is calculated when topic contains utf-8-3 or utf-8-4 characters Incorrect variable length is calculated when topic contains utf-8-3 or utf-8-4 characters in SUBSCRIBE/PUBLISH packets Aug 27, 2021
@Eason010212 Eason010212 changed the title Incorrect variable length is calculated when topic contains utf-8-3 or utf-8-4 characters in SUBSCRIBE/PUBLISH packets Incorrect remaining length is calculated when topic contains utf-8-3 or utf-8-4 characters in SUBSCRIBE/PUBLISH packets Aug 27, 2021
@brentru
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brentru commented Aug 27, 2021

@Eason010212 Hi - are you interested in submitting this as a pull request? I'll review it.

@Eason010212 Eason010212 mentioned this issue Aug 27, 2021
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@Eason010212
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@Eason010212 Hi - are you interested in submitting this as a pull request? I'll review it.
OK

FoamyGuy added a commit that referenced this issue Dec 22, 2021
@FoamyGuy
Merge pull request #91 from Eason010212/fix-remaining-length
3cd9d3d 
Fix Issue #90: Remaining length issues
@FoamyGuy
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closed by #91

rtwfroody pushed a commit to rtwfroody/Adafruit_CircuitPython_MiniMQTT that referenced this issue Sep 18, 2022
@FoamyGuy
Merge pull request adafruit#91 from Eason010212/fix-remaining-length
da50f5c 
Fix Issue adafruit#90: Remaining length issues
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@brentru @FoamyGuy @Eason010212