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mqtt: WIP: Read variable header indepentenly from payload #13465

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mqtt: WIP: Read variable header indepentenly from payload #13465

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6404f8d
mqtt: read variable header independently from payload
schicho Apr 24, 2024
965786e
mqtt: correctly handle zero length payloads in publish packets
schicho Apr 25, 2024
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48 changes: 46 additions & 2 deletions lib/mqtt.c
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Original file line number Diff line number Diff line change
Expand Up @@ -623,10 +623,12 @@ static CURLcode mqtt_read_publish(struct Curl_easy *data, bool *done)
CURLcode result = CURLE_OK;
struct connectdata *conn = data->conn;
ssize_t nread;
ssize_t nprocessed = 0;
size_t remlen;
struct mqtt_conn *mqtt = &conn->proto.mqtt;
struct MQTT *mq = data->req.p.mqtt;
unsigned char packet;
ssize_t topiclen;

switch(mqtt->state) {
MQTT_SUBACK_COMING:
Expand Down Expand Up @@ -691,10 +693,52 @@ static CURLcode mqtt_read_publish(struct Curl_easy *data, bool *done)
goto end;
}

/* if QoS is set, message contains packet id */
result = Curl_client_write(data, CLIENTWRITE_BODY, buffer, nread);
/* read the variable header */

/* read topic */
if(nread < 2) {
failf(data, "packet too short");
result = CURLE_WEIRD_SERVER_REPLY;
goto end;
}
nprocessed += 2;
topiclen = (unsigned char)buffer[0] << 8 | (unsigned char)buffer[1];
if(nread < nprocessed + topiclen) {
failf(data, "topic length longer than packet");
result = CURLE_WEIRD_SERVER_REPLY;
goto end;
}
result = Curl_client_write(data, CLIENTWRITE_HEADER,
&buffer[nprocessed], topiclen);
if(result)
goto end;
nprocessed += topiclen;

/* if QoS is set, message contains packet id */
if(mq->firstbyte & 0x06) {
if(nread < nprocessed + 2) {
failf(data, "packet too short");
result = CURLE_WEIRD_SERVER_REPLY;
goto end;
}
result = Curl_client_write(data, CLIENTWRITE_HEADER,
&buffer[nprocessed], 2);
if(result)
goto end;
nprocessed += 2;
}

/* read payload */
if(nread - nprocessed > 0) {
result = Curl_client_write(data, CLIENTWRITE_BODY,
&buffer[nprocessed], nread - nprocessed);
if(result)
goto end;
}
else {
/* zero length payload are valid in MQTT */
infof(data, "Zero length payload");
}

mq->npacket -= nread;
if(!mq->npacket)
Expand Down