IIS Server Security, Unable to upload files over 1MB

Hi all,

When I try to copy files over 1MB to a webfolder (webdav), I get:
"an error copying some or all of the selected files "

This is just happening for one website on this IIS server (hosting about 10
others as well) and only on this one IIS server (we have a number of other
servers running and none of the rest exhibit this behaviour). I happens for
all file types for files over 1MB. Anything less copies fine.

As per MS tech support, we increased the uploadreadaheadsize (to 200MB) but
we still get the problem.

Has anyone else experienced the same? Any suggestions on what to check?

Thx folks.

On Jan 14, 4:02m, CamaroZ281LE




Change UploadReadAheadSize back to the default value (49152). Tech
Support is improper for making that suggestion. You want to close the
window for DoS attack.

UploadReadAheadSize has nothing to do with failure to copy files of
that size. If it was involved, then you would not have been able to
copy a 64KB file at all(larger than default value of 48K), but
obviously you could.

Since you are using WebDAV, none of the Asp* limits on upload are
involved, so don't bother trying them - won't matter.

Basically, there is no setting in IIS that limits upload size, so you
must look for limits imposed by custom software *outside* of IIS
itself which is invoked on all those uploaded file types.

For example, URLScan or any other global ISAPI Filter installed on
this server and limiting content-length would prevent uploads. Or
Global Wildcard Application Mappings which can filter the incoming
request and their sizes doing the rejection.


//David
http://w3-4u.blogspot.com
http://blogs.msdn.com/David.Wang
//

I'll reset the value back to 49K but this server isn't public facing so the
chances of DoS on this box is limited.

I'll check for other software outside IIS but I'm pretty confident that this
server isn't running anything other than IIS for hosting about a dozen sites.
If it was something like URLScan or global ISAPI filter (neither of which
I'm familiar with so forgive my ignorance), wouldn't the uploading of files
be affected for all sites on this server?

Thx

David,

I confirmed that the server is not running URLScan. The Global ISAPI
filters include the following: fpexedll.dll ; RpcProxy.dll ;
ASP.NET_2.0.50727.0 (in this order and all set to low priority).

Cheers

If this is IIS7 it might be RequestFiltering default is 4 MB.
The Request Filtering stting is available after installation of the IIS7
Administration pack or it is directly settable in xxx.config

maxallowedcontentlength. Whether Webdav interacts with that I don't know
(don't know what webdav is. )

Unfortunately this is IIS6 running on a 2003 box.

n Jan 14, 5:41m, CamaroZ281LE
< XXXX@XXXXX.COM > wrote:


When talking about arbitrary binaries like ISAPI Filter or ISAPI
Extension DLLs which are installed in IIS to modify web server
behavior, you cannot make the assumption that global configuration
would affect certain behavior for all sites on the server. The code
can very easily have a configuration to toggle logic that excludes/
include certain URLs.

Thus, you need to first look at ALL of the following (they are at
different places in IIS Manager UI):
1. Global ISAPI Filter
2. Site ISAPI Filter
3. Wildcard Application Mapping

Yes, it is possible that your issue is due to site-specific config of
3rd party extension DLLs, which is possible by #2 and #3.


//David
http://w3-4u.blogspot.com
http://blogs.msdn.com/David.Wang
//

Hi David,

Thx for the guidance on this but I must admit - I'm lost when you say look
at the Global ISAPI, Site ISAPI and Wildcard App Mapping. I can find the
Global ISAPI and Site ISAPI in IIS Mgr, but I just see a list of DLL's and to
be honest, I don't know where to go from here. Do you have a link to some
info on how to investigate these items in further detail. I checked your
blog (great blog btw) but I could not find anything specific.

Again, thanks

On Jan 20, 12:14m, CamaroZ281LE



It is unlikely that you will find info on how to investigate those
items in further detail. Everyone can have different values, and
depending on the issue, you look at things differently. It is possible
to attach a debugger and using public symbols and breakpoints get a
good understanding of what is going on, but that requires expertise
with ISAPI that is not easy to transfer nor explain within the context
of any set of documents.

I suggest posting what is actually configured in your system for
others to assist (and for you to learn in return if you want the
information). I can explain the rationale, but I cannot just write all
possible explanations into a document -- that will take too much
effort on my part for very uncertain gains by anyone else.


//David
http://w3-4u.blogspot.com
http://blogs.msdn.com/David.Wang
//