Port System.Net.Security to OpenBSD

[am11]

Contributes to #124911.

[am11]

@sethjackson, unit tests with this change:

/home/am11/th/artifacts/bin/testhost/net11.0-openbsd-Debug-x64/dotnet exec --runtimeconfig System.Net.Security.Unit.Tests.runtimeconfig.json --depsfile System.Net.Security.Unit.Tests.deps.json xunit.console.dll System.Net.Security.Unit.Tests.dll -xml testResults.xml -nologo -nocolor -notrait category=IgnoreForCI -notrait category=OuterLoop -notrait category=failing
popd
===========================================================================================================
~/system.netsec ~/system.netsec
  Discovering: System.Net.Security.Unit.Tests (method display = ClassAndMethod, method display options = None)
  Discovered:  System.Net.Security.Unit.Tests (found 83 of 86 test cases)
  Starting:    System.Net.Security.Unit.Tests (parallel test collections = on [5 threads], stop on fail = off)
    System.Net.Security.Tests.NegotiateAuthenticationTests.Package_Unsupported_NTLM [SKIP]
      Condition(s) not met: "IsNtlmUnavailable"
    System.Net.Security.Tests.NegotiateAuthenticationTests.NtlmMalformedChallenge_ReturnsInvalidToken [SKIP]
      Condition(s) not met: "UseManagedNtlm"
    System.Net.Security.Tests.NegotiateAuthenticationTests.NtlmWithPreExistingTargetInfoEntriesTest [SKIP]
      Condition(s) not met: "UseManagedNtlm"
  Finished:    System.Net.Security.Unit.Tests
=== TEST EXECUTION SUMMARY ===
   System.Net.Security.Unit.Tests  Total: 114, Errors: 0, Failed: 0, Skipped: 3, Time: 5.449s
~/system.netsec

[dotnet-policy-service]

Tagging subscribers to this area: @dotnet/ncl, @bartonjs, @vcsjones
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[sethjackson]

Nice! Seems you fixed the test failures I was having and makes sense as I didn't do the opt-in to managed NTLM. 💯

[rzikm]

LGTM

[rzikm]

/ba-g Test failures are unrelated

[vcsjones]

This looks like it broke the build. it's odd that Helix did not surface the compilation errors. If I dig in the logs, they are there though https://dev.azure.com/dnceng-public/cbb18261-c48f-4abb-8651-8cdcb5474649/_apis/build/builds/1467260/logs/1003

2026-06-16T22:57:34.0038203Z D:\a\_work\1\s\src\libraries\System.Net.Security\tests\FunctionalTests\TestConfiguration.cs(29,158): error CS0103: The name 'RuntimeInformation' does not exist in the current context [D:\a\_work\1\s\src\libraries\System.Net.Security\tests\FunctionalTests\System.Net.Security.Tests.csproj::TargetFramework=net11.0-windows]
2026-06-16T22:57:34.0052636Z D:\a\_work\1\s\src\libraries\System.Net.Security\tests\FunctionalTests\TestConfiguration.cs(29,190): error CS0103: The name 'OSPlatform' does not exist in the current context [D:\a\_work\1\s\src\libraries\System.Net.Security\tests\FunctionalTests\System.Net.Security.Tests.csproj::TargetFramework=net11.0-windows]
2026-06-16T22:57:34.0054981Z D:\a\_work\1\s\src\libraries\System.Net.Security\tests\FunctionalTests\TestConfiguration.cs(30,158): error CS0103: The name 'RuntimeInformation' does not exist in the current context [D:\a\_work\1\s\src\libraries\System.Net.Security\tests\FunctionalTests\System.Net.Security.Tests.csproj::TargetFramework=net11.0-windows]
2026-06-16T22:57:34.0056051Z D:\a\_work\1\s\src\libraries\System.Net.Security\tests\FunctionalTests\TestConfiguration.cs(30,190): error CS0103: The name 'OSPlatform' does not exist in the current context [D:\a\_work\1\s\src\libraries\System.Net.Security\tests\FunctionalTests\System.Net.Security.Tests.csproj::TargetFramework=net11.0-windows]

[am11]

Fix in #129579. I was gathering changes from a shared branch missed it.

it's odd that Helix did not surface the compilation errors.

Perhaps this false-negative is interesting for @dotnet/dnceng.

[lewing]

/ba-g Test failures are unrelated

Nope #129587

[am11]

@lewing, read the comment above yours.