[mapguide-users] SQLite Failure with Empty Geometries

[Kyel Shippey]

Hello all,

 

We recently experienced a vulnerability in MapGuide when encountering a
feature selection that contains "empty" geometries in SQLite. We have not
examined whether it occurs in other file or database formats as well. We are
operating on MapGuide 3.1.2 in 64-bit Windows with FDO 4.1 with PHP
scripting.

 

Empty geometries seem to include WKT values such as:

                POINT()

                LINESTRING()

                POLYGON()

 

When looping over an MgFeatureReader collection that contains a feature like
this, the logic fails when merely attempting to access the affected feature,
so there is no opportunity to detect and gracefully bypass it:

 

while($features->ReadNext()) {

// breaks down before anything can happen

// if this current item has an "empty" geometry

}

 

On our system, the failure is repeatably complete and devastating, requiring
a full server reset which often does not suffice without additional
monkeying on the /Repositores/Library/ and /Repositories/Site/ database
files, suggesting that some file database corruption might occur with this
event.

 

For our purposes, we had success in sanitizing our SQLite files by first
processing them through GeoJSON. From there, ogr2ogr can utilize the
AsText() in its sqlite dialect query and prevent these known culprits from
propagating into our SQLite files library. But the underlying vulnerability
still exists, whether on the MapGuide internals side or just for the SQLite
FDO provider.

 

This seemed worth bringing to everyone's attention for consideration on the
compiled engine code. I can provide a sample SQLite file for investigation
if you like.

 

 

Thank you,

 

Kyel Shippey

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