[mapserver-users] New limitations with mapserver 5 CGI

[Paul Ramsey]

I'd like to see backwards feature compatibility available, and I think
the CGI override controller is one of the most powerful
(under-appreciated) features of Mapserver.

Since the control of what is over-rideable is in the lexer though,
we're sort of in a narrow box. We could do a compile-time option,
which would allow us to default to strict but allow (relatively) easy
conversion to flexible. That wouldn't really help our Windows brethren
though, since they mostly rely on pre-compiled versions, and binary
maintainers don't maintain lots of different builds.

Having a map-level run-time directive to control the availability of
URL over-rides would be the ideal, IMO.  Default, NONE.  Other
options, STRICT and FULL.  However, I don't see how to get there from
here with the lexer requirement.

P.

On Thu, Jul 10, 2008 at 6:05 PM, Graeme Watmuff
<gwatmuff at geographicweb.com.au> wrote:
> Hi Steve,
>
> Thanks for replying and thanks for the coding pointers. You are right
> about the mapserv 4.10 tileindex syntax. Like filter, it is simply
> ignored by v5 rather than throwing an error. My apologies.
>
> Would it make sense to create a 'secure' version for the paranoid and a
> another version with full functionality? I realize this would create
> more maintenance work for you, but not all mapserver users are going to
> be able to climb inside the code themselves to modify functionality
> (fortunately we can).
>
> Regarding security, I presume you are concerned about mapserver exposing
> sensitive data to unintended users. If so, should you be taking that
> responsibility on yourself by limiting mapserver or should the onus be
> upon mapserver users to manage their own data more responsibly? I am a
> great believer in personal responsibility. If the security risk is made
> clear to users, they can make their own decisions as to the data they
> potentially expose to the world.
>
> We have greatly appreciated and benefited from the tremendous work you
> and your associates have done in bringing mapserver to the world and we
> have always looked forward to the added features of each new version.
> But upgrading now comes at some degree of inconvenience for us and maybe
> others unless someone wants to publish the workaround to resurrect lost
> functionality for all to simply acquire.
>
> I am not convinced that limiting the previous functionality is the right
> direction for mapserver unless you fear say a litigious threat from
> security breaches that people may bring upon themselves (hardly your
> responsibility). Those with seriously sensitive data are not going to
> want expose the CGI to all the world via a browser-sent URL anyway. I
> would expect them to send URLs from say, a java web app embedded in a
> secured tomcat container.
>
> Just my thoughts.
>
> Regards and best wishes
>
> Graeme
>
> On Thu, 2008-07-10 at 17:13 -0500, Steve Lime wrote:
>> Hi Graeme: Comments inline... I definitely underestimated the impacts of those
>> changes. Anyway...
>>
>> >>> On 7/9/2008 at 11:23 PM, in message
>> <1215663787.2513.112.camel at bongolx.ringo.net>, Graeme Watmuff
>> <gwatmuff at geographicweb.com.au> wrote:
>> > It has become apparent through some frustrating moments of trial and
>> > error that many of the mapfile variables that were changeable via URL
>> > with mapserver 4.10.x CGI seem no longer changeable with v5.x or 5.2.x.
>> > There is a hint from the docs that this is because of security concerns?
>> > Our java apps don't allow web users to directly interact with the CGI,
>> > so security doesn't seem so important in our case.
>>
>> Allowing unaltered, direct modification of things like FILTERs or CONNECTIONS
>> is a potential security risk although I've never run across a documented case. Filters
>> are risky because they are passed to the underlying data driver which generally
>> trust the contents.
>>
>> > Some examples:
>> >
>> > map_web_metadata='text1' 'text2'
>> > map_layerName_filter=<expression>
>> > map_layerName_tileindex=<tileindex.shp>
>> > map_layerName_data=<datasource>
>> >
>> > allow changes to the mapfile via URL with mapserver 4.10.x
>> >
>> > Following the new syntax specified for v5 + I had expected
>> >
>> > map_web=metadata+"'text1' 'text2'" or maybe
>> > map_web_metadata[0]='text1'+'text2',
>> > map_layer[layerName]=filter+<expression>,
>> > map_layer[layerName]=tileindex+<tileindex.shp>,
>> > map_layer[layerName]=data+<datasource>
>> >
>> > to all perform in the time-honoured way.
>>
>> And they don't... If they did you could combine modifications to a layer in a single
>> variable:
>>
>>   map_layer[layerName]=filter+<expression>+tileindex+<tileindex.shp>+data+<datasource>
>>
>> > Only 'data' could be changed with this new mapserver 5 syntax. I
>> > happened to discover through the change logs that changing tileindex was
>> > reinstated for mapserver 5 CGI, but using the old mapserver 4.10 syntax
>> > (map_layerName_tileindex)=<tileindex.shp> - not the new mapserver 5
>> > syntax style (map_layer[layerName]=tileindex+<tileindex.shp>).
>>
>> Looking at the code, TILEINDEX is not changable via a URL with any syntax. The
>> change log references a bug fix to 4.10. The old syntax doesn't work at all.
>>
>> > mapserv 5 CGI throws an error (Parsing error near (filter)) when the new
>> > syntax is used for filter and ignores the old 4.10 filter syntax.
>>
>> This is expected. It will fail with an error as opposed to the silent failure of versions
>> past.
>>
>> > No URL syntax for changing the web object's metadata content appears
>> > acceptable to the mapserver 5.
>>
>> Correct.
>>
>> > I would dearly like to see changing the layer filter via URL restored
>> > also to mapserver 5. And the web object's metadata setting functionality
>> > too.
>>
>> It's possible to customize this behavior by editing maplexer.l and recompiling
>> the code. Simply find the keyword you're interested in supporting and change
>> the states at which it is valid. So, for TILEINDEX:
>>
>> <INITIAL>tileindex
>>
>> becomes:
>>
>> <INITIAL,URL_STRING>tileindex
>>
>> Same goes for the other parameters you'd want to activate.
>>
>> > Can anyone indicate what mapfile properties are or are not going to be
>> > reinstated in mapserver 5 compared to mapserver 4 for change via URL?
>> > Obviously this has development ramifications for us when we try to
>> > upgrade mapserver.
>>
>> If I (or anyone) can think of a way to make this tunable at runtime I'd love
>> to talk more about it. The set of parameters supported in 5.2 has only changed
>> a little bit since 5.0 based on user input. I can't see exposing more without
>> good reason. FILTER in particular is worrisome and there is a work around with
>> the runtime substitution (e.g. FILTER %someval%). In that example you can
>> pass someval via URL but you have to define a validation pattern (a regex) to
>> check it against.
>>
>> > Alternatively, am I missing something with new mapserver 5 syntax?
>>
>> I'm curious if updating maplexer.l to fit your particular needs is workable.
>>
>> > Graeme Watmuff
>>
>> Steve
>>
> --
> Graeme Watmuff
> Geographic Web Solutions Pty Ltd
> 17 Tay Road
> Woodforde
> South Australia  5072
> ph:  + 61 8 83364463
>
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