Proxy authentication for nuget does not work since dotnet 8

[heiner-suter]

Since we switched from dotnet 6 to dotnet 8, we cannot execute dotnet restore anymore. Authentication at the proxy to reach nuget does not work. With the dotnet 7 image it is working as well. Using dotnet 9, the script failes.

We build our application in GitLab using the image mcr.microsoft.com/dotnet/sdk:8.0 or version 6.0 (working).

The simplified build script looks as follows:

  script:
    - export http_proxy=${BUILD_PROXY} # lower case for apt
    - export https_proxy=${BUILD_PROXY}
    - apt update
    - apt install gss-ntlmssp -y
    - export HTTP_PROXY=${BUILD_PROXY} # upper case for nuget
    - export HTTPS_PROXY=${BUILD_PROXY}
    - echo "export http_proxy=${BUILD_PROXY}"
    - dotnet add src/Test/Test.csproj package Newtonsoft.Json

(we call dotnet add as it gives a more detailed error message than dotnet restore)

The Build_PROXY looks like this: http://proxy-user:[MASKED]@proxy-dev.loc:8080

This is the output of the command:

  Determining projects to restore...
  Writing /tmp/tmpsFfHsE.tmp
info : X.509 certificate chain validation will use the fallback certificate bundle at '/usr/share/dotnet/sdk/8.0.407/trustedroots/codesignctl.pem'.
info : X.509 certificate chain validation will use the fallback certificate bundle at '/usr/share/dotnet/sdk/8.0.407/trustedroots/timestampctl.pem'.
info : Adding PackageReference for package 'Newtonsoft.Json' into project 'src/Test/Test.csproj'.
error: Unable to load the service index for source https://api.nuget.org/v3/index.json.
error:   The proxy tunnel request to proxy 'http://proxy-dev.loc:8080/' failed with status code '407'."