Simple bootstrap script from gpt

bootstrap.sh

@@ -0,0 +1,90 @@
+#!/usr/bin/env sh
+set -eu
+
+SSH_DIR="$HOME/.ssh"
+MACHINE_KEY="$SSH_DIR/id_ed25519"
+
+providers="github university strato gitea"
+
+mkdir -p "$SSH_DIR"
+chmod 700 "$SSH_DIR"
+
+###############################################################################
+# 1. Ensure machine-only key exists
+###############################################################################
+
+if [ ! -e "$MACHINE_KEY" ]; then
+    echo "No machine key found. Generating id_ed25519 (machine-only)."
+
+    ssh-keygen \
+        -t ed25519 \
+        -f "$MACHINE_KEY" \
+        -N "" \
+        -C "$(hostname)-machine"
+
+    chmod 600 "$MACHINE_KEY"
+    chmod 644 "$MACHINE_KEY.pub"
+
+    echo "Machine key created:"
+    echo "  $MACHINE_KEY"
+    echo "  $MACHINE_KEY.pub"
+else
+    echo "Machine key already exists: $MACHINE_KEY"
+fi
+
+###############################################################################
+# 2. Provider-specific key bootstrap
+###############################################################################
+
+echo
+echo "Select provider:"
+i=1
+for p in $providers; do
+    printf "  %d) %s\n" "$i" "$p"
+    i=$((i + 1))
+done
+
+printf "> "
+read -r choice
+
+case "$choice" in
+    1) provider="github" ;;
+    2) provider="university" ;;
+    3) provider="strato" ;;
+    4) provider="gitea" ;;
+    *)
+        echo "Invalid selection" >&2
+        exit 1
+        ;;
+esac
+
+key_path="$SSH_DIR/id_$provider"
+
+if [ -e "$key_path" ]; then
+    echo "Refusing to overwrite existing key: $key_path" >&2
+    exit 1
+fi
+
+umask 077
+
+echo
+echo "Paste the private key for '$provider'."
+echo "Finish with EOF (Ctrl-D on empty line)."
+echo
+
+key="$(cat)"
+
+case "$key" in
+    *"BEGIN "*PRIVATE*" KEY"*)
+        ;;
+    *)
+        echo "Input does not look like a private key. Aborting." >&2
+        exit 1
+        ;;
+esac
+
+printf "%s\n" "$key" > "$key_path"
+chmod 600 "$key_path"
+
+echo
+echo "Key written to $key_path with permissions 600"