Configuration: Fixed integer overflow in setting MaxRequestBodySize and MultipartBodyLengthLimit

[AndyButland]

Prerequisites

• I have added steps to test this contribution in the description below

Fixes: #20343

Description

We have an integer overflow exception when we attempt to convert a configured KB value into bytes. It's caused by multiplying two ints together to make a long - if the two ints go over int.MaxValue the result is zero.

I've fixed this by casting one of the ints to a long before doing the calculation.

Testing

You can test this via breakpoints at the places of the changed code on start up, veryfiny that the value is set to a non-zero value when configured in Umbraco:Cms to be, e.g. as follows:

  "Runtime": {
    "MaxRequestLength": 4194304
  },

And verify that you can save and publish nodes (previously having this value coerced to zero would cause an exception to be thrown).

Release

Once verified and merged for 13, needs to be cherry-picked up to 16.

[Copilot]

Pull Request Overview

This PR fixes an integer overflow bug that occurs when converting configured MaxRequestLength values from KB to bytes. The fix prevents the overflow by casting one operand to long before multiplication.

• Cast integer to long before multiplication to prevent overflow when converting KB to bytes
• Apply fix to both KestrelServerOptions and FormOptions configuration classes

Reviewed Changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated no comments.

File	Description
src/Umbraco.Web.Common/Security/ConfigureKestrelServerOptions.cs	Cast MaxRequestLength to long before multiplication to prevent integer overflow
src/Umbraco.Web.Common/Security/ConfigureFormOptions.cs	Cast MaxRequestLength to long before multiplication to prevent integer overflow

[iOvergaard]

This is essentially the same fix as #18141, so I assume we do not need to merge it forward. But really great to see a non-breaking solution for v13. Happy to approve, LGTM!