[mapserver-users] RE: CGI returning a 502 error

Thu Sep 23 13:19:15 EDT 2010

The hard limit was purposeful. The thought at the time was that 100 would be sufficient in 99.9% of cases (this is the only time I've heard of someone running into it) and anything beyond 100 would likely be some sort of rogue attack. The code itself does not use the maximum in allocating parameter lists, that's done dynamically. It's only a check...

Steve

From: mapserver-users-bounces at lists.osgeo.org [mailto:mapserver-users-bounces at lists.osgeo.org] On Behalf Of Jan Hartmann
Sent: Thursday, September 23, 2010 1:23 AM
To: mapserver-users at lists.osgeo.org; Lime, Steve D (DNR)
Subject: Re: [mapserver-users] RE: CGI returning a 502 error

Wasn't there a similar problem about the hard-coded maximum number of classes a few years ago? That problem was solved, if I remember correctly. Wouldn't it be a good idea to take that solution over to the number of CGI parms? The problem won't turn up often, but if it does it is hard to detect, and as far as I can see it's not hard to solve.

Jan

On 09/22/10 20:56, Lime, Steve D (DNR) wrote:

Yes, there is a preset limit on the number of parameters the MapServer cgi will accept and indeed it is 100. There are two ways to work around this.

1) Edit the MS_MAX_CGI_PARAMS setting in cgiutil.h and recompile.

2) Consider combining the requested layers calls into a single variable. That is:

Change

  ...layer=layer1&layer=layer2&layer=layer3...

to:

  ...layers=layer1+layer2+layer3...

You should see an error message from MapServer in your web server error log if you ran into this limitation...

Steve

-----Original Message-----

From: mapserver-users-bounces at lists.osgeo.org<mailto:mapserver-users-bounces at lists.osgeo.org> [mailto:mapserver-users-bounces at lists.osgeo.org] On Behalf Of stoli

Sent: Tuesday, September 21, 2010 11:19 AM

To: mapserver-users at lists.osgeo.org<mailto:mapserver-users at lists.osgeo.org>

Subject: [mapserver-users] RE: CGI returning a 502 error

I do not think it is a string length limit. The IIS returns a separate error

for that. At least it does when you exceed the URL length limit in a GET

request.

I have been doing some tests and it looks like it might be more of a limit

in the number of parameters in the POST request. I can't find any info

regarding the maximum number of parameters that you can send in one request

(to an IIS server), but again, I would think that IIS would be responding

with a more specific error if the limit was with it.

Is it possible that the MapServer CGI is limited to 100 POST parameters?

Fawcett, David (MPCA) wrote:

According to the docs, starting with MapServer 5.0, there is no limit to

the number of layers in a mapfile.

http://mapserver.org/introduction.html#layer-object

I am guessing that you are running into a different issue.

Have you captured the post request string and examined it to make sure

that it is valid?

Are you running into a string length limit for your post request?  The URL

for your post request would be limited to ~2k char for IE, but this only

includes the URL to the server, not the key:value pairs.  There could be a

size limit for post requests set on your Web server to help prevent DOS

attacks.  I don't know where this would be set in IIS.

David.

-----Original Message-----

From: mapserver-users-bounces at lists.osgeo.org<mailto:mapserver-users-bounces at lists.osgeo.org>

[mailto:mapserver-users-bounces at lists.osgeo.org] On Behalf Of stoli

Sent: Monday, September 20, 2010 6:18 PM

To: mapserver-users at lists.osgeo.org<mailto:mapserver-users at lists.osgeo.org>

Subject: [mapserver-users] CGI returning a 502 error

I'm using the ms4w binaries (5.6.3) under IIS 7.

My application sends (via http POST) a lot of parameters to modify the

.map

file. Mostly to add features to layers that are turned off by default and

then make them visible. When my parameters cause the map to show over 50

layers, the IIS returns a 502 error.

I realize that the max layers are set to 100 in the default map.h file,

but

like I said, I am using the compiled binaries from ms4w. Does anyone know

if

they change that to 50 when they compile, or should I look elsewhere to

find

my problem?

--

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