Add ability to run as other users

.golangci.yml

@@ -19,6 +19,9 @@ linters:
     - nilnil
     - funcorder
 
+    # Deprecated linters that have been replaced with newer versions.
+    - gomodguard  # Replaced by gomodguard_v2 (deprecated since v2.12.0)
+
     # Below are linters that lint for things we don't value. Each entry below
     # this line must have a comment explaining the rationale.
 

Dockerfile

@@ -39,10 +39,12 @@ RUN --mount=target=. \
 
 # Produce the Function image.
 FROM python:3.14-bookworm AS image
-RUN apt-get update && apt-get install -y coreutils curl jq unzip zsh less
+RUN apt-get update && apt-get install -y coreutils curl jq unzip zsh less libnss-wrapper
 RUN groupadd -g 65532 nonroot
-RUN useradd -u 65532 -g 65532 -d /home/nonroot --system --shell /usr/sbin/nologin nonroot
-RUN mkdir /scripts /.aws && chown 65532:65532 /scripts /.aws 
+RUN useradd -u 65532 -g 65532 -d /home/nonroot --create-home nonroot
+RUN mkdir /scripts /.aws && chown 65532:65532 /scripts /.aws
+COPY scripts/nss-wrapper-entrypoint.sh /scripts/nss-wrapper-entrypoint.sh
+RUN chmod +x /scripts/nss-wrapper-entrypoint.sh
 
 # Download platform-specific AWS CLI binaries
 ARG TARGETPLATFORM
@@ -55,7 +57,8 @@ RUN if [ "$TARGETPLATFORM" = "linux/arm64" ]; then \
        curl "https://awscli.amazonaws.com/awscli-exe-linux-x86_64.zip" -o "/tmp/awscliv2.zip"; \
     fi && \
     unzip "/tmp/awscliv2.zip" && \
-    ./aws/install
+    ./aws/install && \
+    rm -rf /aws /tmp/awscliv2.zip
 
 WORKDIR /
 

README.md

@@ -21,6 +21,7 @@ returns the output to specified fields.
 - [Parameters](#parameters)
 - [Error Handling and Output Capture](#error-handling-and-output-capture)
 - [Caching Function Outputs](#caching-function-outputs)
+- [Running as Arbitrary User IDs](#running-as-arbitrary-user-ids)
 - [Examples](#examples)
 - [Development and Test](#development-and-test)
 
@@ -153,10 +154,69 @@ set a new cache duration for the output.
 
 See the echo [composition.yaml](example/echo/composition.yaml) for an example.
 
+## Running as Arbitrary User IDs
+
+Some Kubernetes environments (OpenShift, restricted Pod Security Standards) force containers to run as arbitrary user IDs that don't exist in `/etc/passwd`. This can cause tools like AWS CLI, git, and ssh to fail because they can't look up the current user.
+
+The function-shell image includes `nss-wrapper` support to handle this scenario. When enabled via a `DeploymentRuntimeConfig`, the entrypoint script creates a fake passwd/group entry for the running UID, allowing tools that require user lookup to function correctly.
+
+### Enabling nss-wrapper
+
+Configure your `DeploymentRuntimeConfig` to use the nss-wrapper entrypoint:
+
+```yaml
+apiVersion: pkg.crossplane.io/v1beta1
+kind: DeploymentRuntimeConfig
+metadata:
+  name: function-shell-arbitrary-uid
+spec:
+  deploymentTemplate:
+    spec:
+      selector: {}
+      template:
+        spec:
+          containers:
+            - name: package-runtime
+              # Override the entrypoint to use nss-wrapper
+              command: ["/scripts/nss-wrapper-entrypoint.sh"]
+              args: ["/function"]
+              securityContext:
+                allowPrivilegeEscalation: false
+                privileged: false
+                runAsNonRoot: true
+                runAsUser: 2000
+                runAsGroup: 2000
+```
+
+Reference this config in your Function:
+
+```yaml
+apiVersion: pkg.crossplane.io/v1
+kind: Function
+metadata:
+  name: function-shell
+spec:
+  package: xpkg.upbound.io/crossplane-contrib/function-shell:v0.7.0
+  runtimeConfigRef:
+    apiVersion: pkg.crossplane.io/v1beta1
+    kind: DeploymentRuntimeConfig
+    name: function-shell-arbitrary-uid
+```
+
+The nss-wrapper entrypoint:
+
+- Creates a home directory at `/tmp/home` (writable by any user)
+- Generates passwd/group entries for the arbitrary UID/GID
+- Sets `HOME` environment variable appropriately
+- Only activates when running as a UID other than 0 (root) or 65532 (default nonroot user)
+
+See the [arbitrary-uid example](example/arbitrary-uid/) for a complete configuration.
+
 ## Examples
 
 This repository includes the following examples in the `example/` directory:
 
+- **[arbitrary-uid](example/arbitrary-uid/)** - Running as arbitrary user IDs (OpenShift/restricted environments)
 - **[echo](example/echo/)** - Basic shell command execution with output capture
 - **[datadog-dashboard-ids](example/datadog-dashboard-ids/)** - API integration with secret management
 - **[fieldRef](example/fieldRef/)** - Using field references for dynamic values

example/arbitrary-uid/README.md

@@ -0,0 +1,118 @@
+# Arbitrary UID Example
+
+This example demonstrates how to run function-shell as an arbitrary user ID,
+which is common in OpenShift and other restricted Kubernetes environments.
+
+## Problem
+
+Some Kubernetes environments force containers to run as arbitrary user IDs
+that don't exist in `/etc/passwd`. This causes tools like AWS CLI, git, and
+ssh to fail because they can't look up the current user.
+
+## Solution
+
+The function-shell image includes `nss-wrapper` support. When enabled via
+a `DeploymentRuntimeConfig`, the entrypoint script creates fake passwd/group
+entries for the running UID/GID, allowing tools that require user lookup to
+function correctly.
+
+## Files
+
+- `functions.yaml` - Function and DeploymentRuntimeConfig with nss-wrapper enabled
+- `composition.yaml` - Example composition that prints user info (HOME, UID, GID, whoami)
+- `xr.yaml` - Example composite resource
+
+## Testing Locally
+
+1. Start the function in development mode:
+
+   ```shell
+   go run . --insecure --debug
+   ```
+
+2. In another terminal, render the example:
+
+   ```shell
+   crossplane beta render \
+       example/arbitrary-uid/xr.yaml \
+       example/arbitrary-uid/composition.yaml \
+       example/arbitrary-uid/functions.yaml
+   ```
+
+## Expected Output
+
+The composition runs a shell command that outputs:
+
+- `HOME` environment variable (should be `/tmp/home` for arbitrary UIDs)
+- Current user ID and group ID
+- Output of `whoami` (should be `runner` for arbitrary UIDs)
+
+Example output in `status.atFunction.shell.stdout`:
+
+```yaml
+status:
+  atFunction:
+    shell:
+      stderr: ""
+      stdout: |-
+        HOME=/tmp/home
+        uid=2000(runner) gid=2000(runner) groups=2000(runner)
+        whoami=runner
+```
+
+## Deploying to a Cluster
+
+1. Install the function with the DeploymentRuntimeConfig:
+
+   ```shell
+   kubectl apply -f example/arbitrary-uid/functions.yaml
+   ```
+
+2. Apply the CompositeResourceDefinition and Composition:
+
+   ```shell
+   kubectl apply -f example/arbitrary-uid/definition.yaml
+   kubectl apply -f example/arbitrary-uid/composition.yaml
+   ```
+
+3. Create a composite resource to trigger the composition:
+
+   ```shell
+   kubectl apply -f example/arbitrary-uid/xr.yaml
+   ```
+
+4. Check the composite resource status:
+
+   ```shell
+   kubectl get xr example-arbitrary-uid -o yaml
+   ```
+
+   The output should show the function successfully ran with the arbitrary UID:
+
+   ```yaml
+   apiVersion: example.crossplane.io/v1
+   kind: XR
+   metadata:
+     name: example-arbitrary-uid
+   spec:
+     crossplane:
+       compositionRef:
+         name: arbitrary-uid-example
+   status:
+     atFunction:
+       shell:
+         stderr: ""
+         stdout: |-
+           HOME=/tmp/home
+           uid=2000(runner) gid=2000(runner) groups=2000(runner)
+           whoami=runner
+     conditions:
+     - lastTransitionTime: "2026-07-27T17:45:59Z"
+       reason: ReconcileSuccess
+       status: "True"
+       type: Synced
+     - lastTransitionTime: "2026-07-27T17:45:59Z"
+       reason: Available
+       status: "True"
+       type: Ready
+   ```

example/arbitrary-uid/composition.yaml

@@ -0,0 +1,22 @@
+apiVersion: apiextensions.crossplane.io/v1
+kind: Composition
+metadata:
+  name: arbitrary-uid-example
+spec:
+  compositeTypeRef:
+    apiVersion: example.crossplane.io/v1
+    kind: XR
+  mode: Pipeline
+  pipeline:
+    - step: shell
+      functionRef:
+        name: function-shell
+      input:
+        apiVersion: shell.fn.crossplane.io/v1alpha1
+        kind: Parameters
+        shellCommand: |
+          echo "HOME=${HOME}"
+          echo "$(id)"
+          echo "whoami=$(whoami)"
+        stdoutField: status.atFunction.shell.stdout
+        stderrField: status.atFunction.shell.stderr

example/arbitrary-uid/definition.yaml

@@ -0,0 +1,27 @@
+apiVersion: apiextensions.crossplane.io/v2
+kind: CompositeResourceDefinition
+metadata:
+  name: xrs.example.crossplane.io
+spec:
+  group: example.crossplane.io
+  names:
+    kind: XR
+    plural: xrs
+  scope: Cluster
+  versions:
+    - name: v1
+      served: true
+      referenceable: true
+      schema:
+        openAPIV3Schema:
+          type: object
+          properties:
+            spec:
+              type: object
+              properties: {}
+            status:
+              type: object
+              properties:
+                atFunction:
+                  type: object
+                  x-kubernetes-preserve-unknown-fields: true

example/arbitrary-uid/functions.yaml

@@ -0,0 +1,46 @@
+# Example: Running function-shell as an arbitrary UID
+#
+# Some Kubernetes environments (OpenShift, restricted Pod Security Standards)
+# force containers to run as arbitrary user IDs that don't exist in /etc/passwd.
+# This can cause tools like AWS CLI, git, and ssh to fail.
+#
+# This example shows how to use the nss-wrapper entrypoint to handle arbitrary UIDs.
+# The entrypoint script creates a fake passwd entry for the running UID, allowing
+# tools that require user lookup to function correctly.
+#
+---
+apiVersion: pkg.crossplane.io/v1
+kind: Function
+metadata:
+  name: function-shell
+spec:
+  package: xpkg.upbound.io/crossplane-contrib/function-shell:v0.7.0
+  runtimeConfigRef:
+    apiVersion: pkg.crossplane.io/v1beta1
+    kind: DeploymentRuntimeConfig
+    name: function-shell-arbitrary-uid
+---
+apiVersion: pkg.crossplane.io/v1beta1
+kind: DeploymentRuntimeConfig
+metadata:
+  name: function-shell-arbitrary-uid
+spec:
+  deploymentTemplate:
+    spec:
+      selector: {}
+      template:
+        spec:
+          containers:
+            - name: package-runtime
+              # Override the entrypoint to use nss-wrapper
+              # This enables running as arbitrary UIDs
+              command: ["/scripts/nss-wrapper-entrypoint.sh"]
+              args: ["/function"]
+              securityContext:
+                allowPrivilegeEscalation: false
+                privileged: false
+                runAsNonRoot: true
+                # Example: OpenShift may assign a UID like 1000580000
+                # The nss-wrapper entrypoint will handle this automatically
+                runAsUser: 2000
+                runAsGroup: 2000

example/arbitrary-uid/xr.yaml

@@ -0,0 +1,6 @@
+---
+apiVersion: example.crossplane.io/v1
+kind: XR
+metadata:
+  name: example-arbitrary-uid
+spec: {}

input/v1alpha1/parameters.go

@@ -94,7 +94,7 @@ func (sev *ShellEnvVar) GetType() ShellEnvVarType {
 	return sev.Type
 }
 
-// ShellEnvVarsRef refers to an environment variable or secret leaded into
+// ShellEnvVarsRef refers to an environment variable or secret loaded into
 // the function pod.
 type ShellEnvVarsRef struct {
 	// The Key whose value is the secret