Add sshd feature (#132)

* Initial plan

* Add sshd feature

Co-authored-by: sebst <592313+sebst@users.noreply.github.com>

* Fix sshd tests: install procps/iproute2, create /run/sshd, make test self-starting

Co-authored-by: sebst <592313+sebst@users.noreply.github.com>

---------

Co-authored-by: copilot-swe-agent[bot] <198982749+Copilot@users.noreply.github.com>
Co-authored-by: sebst <592313+sebst@users.noreply.github.com>

Author: Copilot

.github/workflows/test.yaml

@@ -52,6 +52,7 @@ jobs:
           - smallstep.com
           - starship.rs
           - swc.rs
+          - sshd
           - tailscale.com
           - webinstall.dev
           - yq
@@ -114,6 +115,7 @@ jobs:
           - smallstep.com
           - starship.rs
           - swc.rs
+          - sshd
           - tailscale.com
           - webinstall.dev
           - yq

src/sshd/README.md

@@ -0,0 +1,30 @@
+# sshd (sshd)
+
+Install OpenSSH server (sshd) and ensure it starts when the container starts
+
+## Example Usage
+
+```json
+"features": {
+    "ghcr.io/devcontainer-community/devcontainer-features/sshd:1": {}
+}
+```
+
+## Options
+
+| Options Id | Description | Type | Default Value |
+|-----|-----|-----|-----|
+| port | Port for sshd to listen on. | string | 2222 |
+
+## Notes
+
+The `openssh-server` package is installed via `apt` and sshd is configured to
+listen on the specified port (default `2222`).  An entrypoint script is added
+that starts the sshd daemon automatically each time the container starts.
+
+To connect from the host you may need to forward the port in your
+`devcontainer.json`:
+
+```json
+"forwardPorts": [2222]
+```

src/sshd/devcontainer-feature.json

@@ -0,0 +1,19 @@
+{
+    "name": "sshd",
+    "id": "sshd",
+    "version": "1.0.0",
+    "description": "Install OpenSSH server (sshd) and ensure it starts when the container starts",
+    "documentationURL": "https://github.com/devcontainer-community/devcontainer-features/tree/main/src/sshd",
+    "options": {
+        "port": {
+            "type": "string",
+            "default": "2222",
+            "proposals": [
+                "2222",
+                "22"
+            ],
+            "description": "Port for sshd to listen on."
+        }
+    },
+    "entrypoint": "/usr/local/share/sshd/entrypoint.sh"
+}

src/sshd/install.sh

@@ -0,0 +1,69 @@
+#!/bin/bash
+set -o errexit
+set -o pipefail
+set -o noclobber
+set -o nounset
+set -o allexport
+
+readonly name="sshd"
+
+apt_get_update() {
+    if [ "$(find /var/lib/apt/lists/* | wc -l)" = "0" ]; then
+        echo "Running apt-get update..."
+        apt-get update -y
+    fi
+}
+
+apt_get_checkinstall() {
+    if ! dpkg -s "$@" >/dev/null 2>&1; then
+        apt_get_update
+        DEBIAN_FRONTEND=noninteractive apt-get -y install --no-install-recommends --no-install-suggests --option 'Debug::pkgProblemResolver=true' --option 'Debug::pkgAcquire::Worker=1' "$@"
+    fi
+}
+
+apt_get_cleanup() {
+    apt-get clean
+    rm -rf /var/lib/apt/lists/*
+}
+
+echo_banner() {
+    local text="$1"
+    echo -e "\e[1m\e[97m\e[41m$text\e[0m"
+}
+
+install() {
+    # procps provides pgrep (used in entrypoint); iproute2 provides ss (used in tests)
+    apt_get_checkinstall openssh-server procps iproute2
+
+    # Create SSH drop-in config directory if missing and add devcontainer config
+    mkdir -p /etc/ssh/sshd_config.d
+    echo "Port ${PORT}" > /etc/ssh/sshd_config.d/devcontainer.conf
+
+    # Generate SSH host keys at install time so they are baked into the image
+    ssh-keygen -A
+
+    # Create the privilege separation directory required by sshd
+    mkdir -p /run/sshd
+
+    # Create entrypoint directory and script
+    mkdir -p /usr/local/share/sshd
+    cat > /usr/local/share/sshd/entrypoint.sh << 'EOF'
+#!/bin/bash
+# Recreate the privilege separation directory (may be absent after container restart)
+mkdir -p /run/sshd
+# Regenerate host keys if any are missing (e.g. first start of a new container)
+ssh-keygen -A 2>/dev/null || true
+# Start sshd in daemon mode if it is not already running
+if ! pgrep sshd > /dev/null 2>&1; then
+    /usr/sbin/sshd
+fi
+EOF
+    chmod 755 /usr/local/share/sshd/entrypoint.sh
+
+    apt_get_cleanup
+}
+
+echo_banner "devcontainer.community"
+echo "Installing $name..."
+install "$@"
+echo "(*) Done!"

test/sshd/test.sh

@@ -0,0 +1,23 @@
+#!/bin/bash
+
+
+set -e
+
+# Optional: Import test library bundled with the devcontainer CLI
+# See https://github.com/devcontainers/cli/blob/HEAD/docs/features/test.md#dev-container-features-test-lib
+# Provides the 'check' and 'reportResults' commands.
+source dev-container-features-test-lib
+
+# Feature-specific tests
+# The 'check' command comes from the dev-container-features-test-lib. Syntax is...
+# check <LABEL> <cmd> [args...]
+
+check "sshd installed" which sshd
+check "openssh version" bash -c "sshd -V 2>&1 | grep -i openssh"
+check "sshd port configured" bash -c "grep -r 'Port 2222' /etc/ssh/"
+check "sshd running" bash -c "pgrep sshd || ( mkdir -p /run/sshd && /usr/sbin/sshd && sleep 1 && pgrep sshd )"
+check "sshd listening on port 2222" bash -c "ss -tln | grep ':2222'"
+
+# Report results
+# If any of the checks above exited with a non-zero exit code, the test will fail.
+reportResults