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fix: support zero-length clientId #331

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Merged
merged 5 commits into from
Oct 30, 2025
Merged

fix: support zero-length clientId #331

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311e4f2
fix: support zero-length clientId
Ryan-CW-Code Oct 24, 2025
1d55cfd
Fix formatting
kstribrnAmzn Oct 24, 2025
37b90bc
Add unit tests
kstribrnAmzn Oct 28, 2025
b7cec15
Fix CBMC tests
kstribrnAmzn Oct 29, 2025
e827ee2
Only access when not NULL
kstribrnAmzn Oct 29, 2025
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9 changes: 7 additions & 2 deletions source/core_mqtt_serializer.c
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Original file line number Diff line number Diff line change
Expand Up @@ -1706,9 +1706,14 @@ MQTTStatus_t MQTT_GetConnectPacketSize( const MQTTConnectInfo_t * pConnectInfo,
( void * ) pPacketSize ) );
status = MQTTBadParameter;
}
else if( ( pConnectInfo->clientIdentifierLength == 0U ) || ( pConnectInfo->pClientIdentifier == NULL ) )
else if( ( pConnectInfo->clientIdentifierLength == 0U ) ^ ( ( pConnectInfo->pClientIdentifier == NULL ) || ( *( pConnectInfo->pClientIdentifier ) == '\0' ) ) )
{
LogError( ( "Mqtt_GetConnectPacketSize() client identifier must be set." ) );
LogError( ( "Client ID length and value mismatch." ) );
status = MQTTBadParameter;
}
else if( ( pConnectInfo->clientIdentifierLength == 0U ) && ( pConnectInfo->cleanSession == false ) )
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@Ryan-CW-Code Ryan-CW-Code Oct 24, 2025 •
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The preceding if already ensures that when clientIdentifierLength is 0, pClientIdentifier must be either NULL or '\0'. Therefore, this if does not need to repeat those conditions. However, I am not sure whether this simplification might cause difficulties in reading and understanding.

{
LogError( ( "Zero-length client identifier requires cleanSession=true per MQTT 3.1.1." ) );
status = MQTTBadParameter;
}
else if( ( pWillInfo != NULL ) && ( pWillInfo->payloadLength > ( size_t ) UINT16_MAX ) )
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7 changes: 6 additions & 1 deletion test/cbmc/proofs/MQTT_SerializeConnect/MQTT_SerializeConnect_harness.c
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Expand Up @@ -39,7 +39,12 @@ void harness()
MQTTStatus_t status = MQTTSuccess;

pConnectInfo = allocateMqttConnectInfo( NULL );
__CPROVER_assume( isValidMqttConnectInfo( pConnectInfo ) );

/* Avoid a malloc(0U) which causes dereference errors */
if( ( pConnectInfo != NULL ) && ( pConnectInfo->clientIdentifierLength == 0U ) )
{
pConnectInfo->pClientIdentifier = NULL;
}

pWillInfo = allocateMqttPublishInfo( NULL );
__CPROVER_assume( isValidMqttPublishInfo( pWillInfo ) );
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48 changes: 48 additions & 0 deletions test/unit-test/core_mqtt_serializer_utest.c
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Expand Up @@ -463,11 +463,59 @@ void test_MQTT_GetConnectPacketSize( void )
status = MQTT_GetConnectPacketSize( &connectInfo, NULL, &remainingLength, &packetSize );
TEST_ASSERT_EQUAL_INT( MQTTBadParameter, status );

/* Verify NULL client identifier with provided non-zero length fails. */
connectInfo.pClientIdentifier = NULL;
connectInfo.clientIdentifierLength = CLIENT_IDENTIFIER_LENGTH;
connectInfo.cleanSession = true;
status = MQTT_GetConnectPacketSize( &connectInfo, NULL, &remainingLength, &packetSize );
TEST_ASSERT_EQUAL_INT( MQTTBadParameter, status );

/* Verify empty string client ID with provided non-zero length fails. */
connectInfo.pClientIdentifier = "";
connectInfo.clientIdentifierLength = 99U;
connectInfo.cleanSession = true;
status = MQTT_GetConnectPacketSize( &connectInfo, NULL, &remainingLength, &packetSize );
TEST_ASSERT_EQUAL_INT( MQTTBadParameter, status );

/* Verify zero-length client identifier must have clean session. */
connectInfo.pClientIdentifier = NULL;
connectInfo.clientIdentifierLength = 0U;
connectInfo.cleanSession = false;
status = MQTT_GetConnectPacketSize( &connectInfo, NULL, &remainingLength, &packetSize );
TEST_ASSERT_EQUAL_INT( MQTTBadParameter, status );

/* Verify zero-length client identifier must have clean session. */
connectInfo.pClientIdentifier = "";
connectInfo.clientIdentifierLength = 0U;
connectInfo.cleanSession = false;
status = MQTT_GetConnectPacketSize( &connectInfo, NULL, &remainingLength, &packetSize );
TEST_ASSERT_EQUAL_INT( MQTTBadParameter, status );

/* NULL client ID and client ID length of 0 is treated as zero-length identifier */
connectInfo.pClientIdentifier = NULL;
connectInfo.clientIdentifierLength = 0U;
connectInfo.cleanSession = true;
connectInfo.pUserName = NULL;
connectInfo.pPassword = NULL;
status = MQTT_GetConnectPacketSize( &connectInfo, NULL, &remainingLength, &packetSize );
TEST_ASSERT_EQUAL_INT( MQTTSuccess, status );
/* Make sure remaining size returned is 12. */
TEST_ASSERT_EQUAL_INT( 12, remainingLength );
/* Make sure packet size is 14. */
TEST_ASSERT_EQUAL_INT( 14, packetSize );

/* Empty string client ID and client ID length of 0 is treated as zero-length identifier */
connectInfo.pClientIdentifier = "";
connectInfo.clientIdentifierLength = 0U;
connectInfo.pUserName = NULL;
connectInfo.pPassword = NULL;
status = MQTT_GetConnectPacketSize( &connectInfo, NULL, &remainingLength, &packetSize );
TEST_ASSERT_EQUAL_INT( MQTTSuccess, status );
/* Make sure remaining size returned is 12. */
TEST_ASSERT_EQUAL_INT( 12, remainingLength );
/* Make sure packet size is 14. */
TEST_ASSERT_EQUAL_INT( 14, packetSize );

/* Test a will message payload length that is too large. */
memset( &connectInfo, 0x0, sizeof( connectInfo ) );
connectInfo.pClientIdentifier = CLIENT_IDENTIFIER;
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