Add application-controlled security policies for kubeconfig exec plugins by Copilot · Pull Request #1930 · kubernetes-client/csharp

Copilot · 2026-10-06T21:51:05Z

Untrusted kubeconfigs can launch arbitrary local processes through exec credential plugins. This adds application-controlled authorization without requiring callers to parse and inspect kubeconfig themselves.

Policy API: Immutable AllowAll (default), DenyAll, and Allowlist policies across configuration builders, including Classic and AOT. Existing API signatures remain available.
Enforcement: Checks initial execution and token refresh before process launch. Denials throw ExecCredentialPluginDeniedException; kubeconfig cannot override the application policy.
Allowlist semantics: Match basenames or exact absolute paths, including Windows UNC paths. Empty lists deny all; invalid entries and quoted commands are rejected. Allowlist mode also rejects kubeconfig-supplied environment overrides to prevent command redirection and loader injection.
Trust boundaries: Basenames permit any matching executable location. Arguments and executable contents are not restricted; the policy is not a sandbox.

var config = KubernetesClientConfiguration.BuildConfigFromConfigFile(
    kubeConfigPath,
    execCredentialPluginPolicy: ExecCredentialPluginPolicy.DenyAll);

// Or explicitly approve credential plugins:
var config = KubernetesClientConfiguration.BuildConfigFromConfigFile(
    kubeConfigPath,
    execCredentialPluginPolicy: ExecCredentialPluginPolicy.Allowlist(
        "kubelogin",
        @"C:\Program Files\Contoso\trusted-plugin.exe"));

Fixes Add security policy support for kubeconfig exec credential plugins #1918

Copilot

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linux-foundation-easycla · 2026-10-06T21:51:13Z

✅ login: brendandburns / name: Brendan Burns (0157b92, 10dd249, 36876d0, 506e755, 53fbfcf, 6b8c21d, 72e7598, 8525843, 8a6b270, b270f4f, f7bfc6b)
❌ - login: @Copilot / name: Copilot Autofix powered by AI. The commit (10dd249, 506e755, 53fbfcf, 72e7598) is not authorized under a signed CLA. Please click here to be authorized. For further assistance with EasyCLA, please visit our EasyCLA portal and chat with our support bot.
❌ - login: @Copilot / name: copilot-swe-agent[bot]. The commit (0157b92, 36876d0, 53692ed, 6b8c21d, 8525843, 8a6b270, b270f4f, f7bfc6b) is not authorized under a signed CLA. Please click here to be authorized. For further assistance with EasyCLA, please visit our EasyCLA portal and chat with our support bot.

Co-authored-by: brendandburns <5751682+brendandburns@users.noreply.github.com>

kubernetes-prow · 2026-10-06T22:01:06Z

[APPROVALNOTIFIER] This PR is NOT APPROVED

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Copilot

Copilot review overview

🟡 Changes recommended

Kubeconfig-controlled environment variables can bypass allowlisted command restrictions and still enable arbitrary code execution.

Review effort: Balanced
Findings: 1

Open (1)

Allowlist ignores kubeconfig-controlled environment during execution · New

Co-authored-by: brendandburns <5751682+brendandburns@users.noreply.github.com>

Copilot

Copilot review overview

🔵 Needs a closer look

Security-sensitive process execution changes span multiple target variants, while the PR explicitly indicates build and security validation remain incomplete.

Review effort: Balanced
Findings: 1

Open (1)

Allowlist ignores kubeconfig-controlled environment during execution

brendandburns · 2026-10-14T16:01:40Z

@copilot can you add documentation that this is intended for defense in depth and is not a hard security boundary, loading a kubeconfig from an untrusted source is an inherently dangerous activity and should be handled as part of an overall security model, not relying exclusively on this capability.

Co-authored-by: brendandburns <5751682+brendandburns@users.noreply.github.com>

Copilot · 2026-10-14T16:03:36Z

@copilot can you add documentation that this is intended for defense in depth and is not a hard security boundary, loading a kubeconfig from an untrusted source is an inherently dangerous activity and...

Added the README clarification in commit 36876d0: the policy is defense in depth, not a hard security boundary, and untrusted kubeconfigs must be addressed within the application's overall security model.

Co-authored-by: brendandburns <5751682+brendandburns@users.noreply.github.com>

Copilot · 2026-10-19T17:43:59Z

@copilot There are some common environment variables used for exec (e.g. AWS_PROFILE) so I think that blocking all environment variables won't work. Can you focus on just blocking dangerous ones and a...

Allowlist mode now blocks PATH, dynamic-loader variables, and common language-runtime injection variables while allowing ordinary overrides such as AWS_PROFILE. Added coverage and updated the README in commit 0157b92.

Copilot

🟡 Changes recommended

Unblocked startup environment variables allow code injection through approved credential plugins.

4 open issues

_{Review effort: Balanced}

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Co-authored-by: brendandburns <5751682+brendandburns@users.noreply.github.com>

Copilot

🟡 Changes recommended

The environment filter still permits CLR profiler settings that can inject native code into an approved .NET credential plugin.

3 open issues

2 resolved since last review

_{Review effort: Balanced}

Co-authored-by: Copilot Autofix powered by AI <175728472+Copilot@users.noreply.github.com>

Co-authored-by: brendandburns <5751682+brendandburns@users.noreply.github.com>

Copilot

🟡 Changes recommended

Allowlist mode permits HOME overrides that can inject startup code into an approved Python-based credential helper.

2 open issues

2 resolved since last review

_{Review effort: Balanced}

+
+        private static bool IsDangerousEnvironmentVariable(string name)
+        {
+            return name != null && (string.Equals(name, "PATH", StringComparison.OrdinalIgnoreCase) ||


Copilot

🟡 Changes recommended

Allowlist environment filtering still permits runtime redirection and Bash function injection that can execute unapproved code.

2 open issues

1 resolved since last review

Normalize Windows path casing during executable matching

_{Review effort: Balanced}

+                string.Equals(name, "DOTNET_STARTUP_HOOKS", StringComparison.OrdinalIgnoreCase) ||
+                string.Equals(name, "CORECLR_ENABLE_PROFILING", StringComparison.OrdinalIgnoreCase) ||
+                name.StartsWith("CORECLR_PROFILER", StringComparison.OrdinalIgnoreCase) ||
+                string.Equals(name, "COR_ENABLE_PROFILING", StringComparison.OrdinalIgnoreCase) ||
+                name.StartsWith("COR_PROFILER", StringComparison.OrdinalIgnoreCase) ||
+                string.Equals(name, "BASH_ENV", StringComparison.OrdinalIgnoreCase) ||
+                string.Equals(name, "PYTHONUSERBASE", StringComparison.OrdinalIgnoreCase));


Initial plan

53692ed

Copilot AI assigned Copilot and brendandburns Oct 6, 2026

Copilot AI balanced review requested due to automatic review settings October 6, 2026 21:51

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Copilot AI linked an issue Oct 6, 2026 that may be closed by this pull request

Add security policy support for kubeconfig exec credential plugins #1918

Open

Add application-controlled exec credential plugin policies

8525843

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Comment thread src/KubernetesClient/ExecCredentialPluginPolicy.cs Resolved

Harden exec allowlists against quoted commands and environment injection

b270f4f

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Copilot AI changed the title ~~[WIP] Add security policy support for kubeconfig exec credential plugins~~ Add application-controlled security policies for kubeconfig exec plugins Oct 6, 2026

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Document exec policy defense-in-depth limits

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Copilot AI balanced review requested due to automatic review settings October 14, 2026 16:03

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Allow safe exec environment overrides

0157b92

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Comment thread src/KubernetesClient/ExecCredentialPluginPolicy.cs Resolved

Add additional environment variable checks

72e7598

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Refactor command resolution logic with exception handling

10dd249

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Prevent probes of unapproved explicit plugin paths

f7bfc6b

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Comment thread src/KubernetesClient/ExecCredentialPluginPolicy.cs Resolved

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kubernetes-prow Bot added size/XXL Denotes a PR that changes 1000+ lines, ignoring generated files. and removed size/XL Denotes a PR that changes 500-999 lines, ignoring generated files. labels Oct 24, 2026

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Add profiling environment variable checks

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Copilot finished work on behalf of brendandburns October 24, 2026 00:53

Match resolved paths case-insensitively on Windows

8a6b270

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brendandburns marked this pull request as ready for review October 24, 2026 00:54

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Comment thread src/KubernetesClient/ExecCredentialPluginPolicy.cs

private static bool IsDangerousEnvironmentVariable(string name)

{

return name != null && (string.Equals(name, "PATH", StringComparison.OrdinalIgnoreCase) ||

Copilot AI balanced review requested due to automatic review settings October 24, 2026 00:55

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