Blazor WebAssembly Application fails to load due to integrity errors - security

Question

We have developed a Blazor WebAssembly Application that has already gone into productive usage for a certain group of customers.
The Application works well in all Browsers with Standard Security settings. However, this morning I got a call from one of the customers, where the Application did not load at all in their Chrome Browser.
I saw the following Errors in the console:
Unknown error occurred while trying to verify integrity.
Failed to load resource: the server responded with a status of 403 (forbidden)
Failed to find a valid digest in the 'integrity' attribute for ressource '<somepath.dll>' with SHA-256 integrity <sha56>. the resource has been blocked
Now my question is, what could cause this? Is this a Browser Security setting, or another security setting e.g on server, in code etc.? How can I fix this?
Here's a picture of the errors mentioned above

Answer 1

The most likely reason why this is happening, is that some Antiviruses block the execution of downloaded .dll files. That's why it is working in some networks, but doesn't in some others.
What you can do, and what is also suggested as a Workaround by microsoft, is to rename all .dll to .bin - and also change the config json. it worked in my case.
I use the following PowerShell function for that:
Function Hide-BlazorDLL {
Param(
[string]$Path = (Get-Location).Path
)
<#
According to the following Links:
https://github.com/dotnet/aspnetcore/issues/19552
https://github.com/dotnet/aspnetcore/issues/5477#issuecomment-599148931
https://github.com/dotnet/aspnetcore/issues/21489
https://gist.github.com/Swimburger/774ca2b63bad4a16eb2fa23b47297e71
#>
# Test if path is correct and accessible
$WorkingDir = Join-Path $Path "_framework"
if (!(Test-Path $WorkingDir)) { Throw "Wrong path $Path. current location must be wwwroot folder of published application." }
# Get All Items
$AllItems = Get-ChildItem $WorkingDir -Recurse
$DLLs = $AllItems | Where-Object { $_.Name -like '*.dll*' }
$BINs = $AllItems | Where-Object { $_.Name -like '*.bin*' }
# End script if no .dll are found
if ($DLLs) {
# Delete all current .bin files
if ($BINs) {
Remove-item $BINs.FullName -Force
}
# Change .dll to .bin on files and config
$DLLs | Rename-item -NewName { $_.Name -replace ".dll\b",".bin" }
((Get-Content "$WorkingDir\blazor.boot.json" -Raw) -replace '.dll"','.bin"') | Set-Content "$WorkingDir\blazor.boot.json"
# Delete Compressed Blazor files
if (Test-Path "$WorkingDir\blazor.boot.json.gz") {
Remove-Item "$WorkingDir\blazor.boot.json.gz"
}
if (Test-Path "$WorkingDir\blazor.boot.json.br") {
Remove-Item "$WorkingDir\blazor.boot.json.br"
}
# Do the same for ServiceWorker, if it exists
$ServiceWorker = Get-Item "$Path\service-worker-assets.js" -ErrorAction SilentlyContinue
if ($ServiceWorker) {
((Get-Content $ServiceWorker.FullName -Raw) -replace '.dll"','.bin"') | Set-Content $ServiceWorker.FullName
Remove-Item ($ServiceWorker.FullName + ".gz")
Remove-Item ($ServiceWorker.FullName + ".br")
}
}
else {
Write-Host "There are no .dll Files to rename to .bin"
}
}
Basically you need to navigate to the wwwroot folder of your published application and run the function there. e.g:
PS D:\inetpub\wwwroot\<appname>\wwwroot> Hide-BlazorDLL

Answer 2

Solution for me was to delete the obj and the bin folder in both the client and the server project folder

Answer 3

This error for some reason kept happening for me when I tested my application in an anonymous browser window (Google Chrome).
Try using a normal browser window if you're getting integrity errors.
Also, if you're using Cloudflare CDN don't forget to "Purge Everything" in the cache.

Answer 4

We have experienced this issue using Cloudflare auto minify feature. That feature removes any comments from html, js and other files - which some of the blazor .js files seems to contain.
This means that the hash of the file contents no longer matches the hash found in blazor.boot.json -> an integrity issue will be thrown and stop the app from loading.
Disabling the auto minify feature fixed the issue.

Answer 5

Tech Stack:
.NET 6.0.11
I had a similar issue. In the local machine, it is working fine. But when it is deployed through GitHub Actions, I get integrity checks error. I got this issue for Blazor WebAssembly ASP.NET Core Hosted (WebAssemblyPrerendered) project. Here is the fix I followed.
Added the .gitattributes file to the solution root folder.
Added the below code at the end of the file.
# blazor dlls - treat all .dll files as binary
*.dll binary