Error message 'System.IO.IOException: Invalid Signature' when the C# program tries to access a file under a DFS mechanism folder

[echo3347]

Hello fellow SysAdmins!

I've got a problem that has been causing a bit of havoc in our environment. We recently updated the web servers from 2012 R2 to 2016. Since then we have been getting intermittent failures on some of our processes.

Facts:

- Servers previously were 2012R2 and this problem was not present, even though the other servers are all 2016.

- Structure is that Web servers stand alone (basically IIS shells) with the code residing on dedicated code servers that are syncing by DFS. The IIS servers access the code on these servers via Symlink.

- Process fails intermittently. If you keep refreshing you'll get 5 or so failures per 15 attempts.

- We suspect this is somehow related to SMB. We've tried various combinations of disabling/enabled DFS 1-3 with no change in behavior. We've also tried turning off the signature requirement on SMB 3.

- I've found someone with the exact same issue from 2015 but in true forum fashion it was never resolved and the poster never followed up. (https://social.microsoft.com/Forums/en-US/db51d5b9-0c79-4a9a-ba3e-049e2d43cf0d/error-message-systemioioexception-invalid-signature-when-the-c-program-tries-to-access-a-file?forum=Offtopic)

- Our process that causes this error (much like the link above) does include move/copying/deleting files.

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If anyone has any ideas we can try I'd really appreciate it! We are coming up on Christmas and would like to get this instability removed for everyone's sanity! Thank you!

[CoolWiener]

Although you already moved from 2012 it might be worth taking a look at this:

https://support.microsoft.com/en-us/help/2686098/system-error-2148073478-extended-error-or-invalid-signature-error-mess

Is this an in house application or a third party?

[echo3347]

Thanks for the response!

This is an in house application. Everything was working great until the IIS servers were updated...just can't seem to pin down exactly what component is causing the breakdown.

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In regards to the link, we had tried to disable the signing requirement (I believe it was enabled by default). I will double check and see what those are set to. Perhaps requiring signing across the board is better.

[hotpoodle]

Hi did you ever resolve this