Add create-secrets.sh helper for Docker Swarm secret provisioning

deploy/create-secrets.sh

@@ -0,0 +1,76 @@
+#!/bin/bash
+################################################################################
+# create-secrets.sh — Docker Swarm secret provisioning helper
+#
+# Usage:
+#   source deploy/create-secrets.sh
+#   create_or_update_secret "secret_name" "secret_value"
+#
+# What it does:
+#   - Creates a Docker secret if it does not already exist
+#   - Detects value changes via a SHA256 checksum stored as a secret label
+#   - If the value has changed: removes the old secret and recreates it
+#   - If the value is unchanged: skips silently (no service disruption)
+#
+# Important notes:
+#   - Docker Swarm has no native "update secret" API. Changing a secret
+#     requires removing and recreating it, then redeploying all services
+#     that reference it. This script handles removal + recreation, but the
+#     stack redeploy still happens via the normal deploy step.
+#   - Secrets are stored encrypted in Swarm's Raft consensus database and
+#     automatically replicated across all nodes.
+#   - The checksum label is NOT the secret value — it is a SHA256 hash used
+#     only to detect whether the value has changed, avoiding unnecessary
+#     secret rotation.
+################################################################################
+
+create_or_update_secret() {
+  local NAME="$1"
+  local VALUE="$2"
+
+  if [ -z "$NAME" ]; then
+    echo "  [ERROR] create_or_update_secret: NAME is required"
+    return 1
+  fi
+
+  if [ -z "$VALUE" ]; then
+    echo "  [WARN] $NAME: value is empty, skipping"
+    return 0
+  fi
+
+  # Compute SHA256 of the new value (no trailing newline to keep hash stable)
+  local NEW_HASH
+  NEW_HASH=$(printf '%s' "$VALUE" | sha256sum | cut -d' ' -f1)
+
+  if docker secret inspect "$NAME" >/dev/null 2>&1; then
+    # Secret exists — check if value has changed via stored checksum label
+    local OLD_HASH
+    OLD_HASH=$(docker secret inspect "$NAME" \
+      --format '{{index .Spec.Labels "checksum"}}' 2>/dev/null || echo "")
+
+    if [ "$NEW_HASH" = "$OLD_HASH" ]; then
+      echo "  [SKIP]   $NAME (unchanged)"
+      return 0
+    fi
+
+    # Value changed — must remove and recreate (Docker limitation)
+    echo "  [UPDATE] $NAME (value changed, rotating)"
+    docker secret rm "$NAME" >/dev/null 2>&1 || {
+      echo "  [ERROR]  $NAME: failed to remove existing secret"
+      echo "           Secret may be in use by a running service."
+      echo "           Scale down the service first, then re-run."
+      return 1
+    }
+  else
+    echo "  [CREATE] $NAME"
+  fi
+
+  # Create the secret with checksum label for future change detection
+  printf '%s' "$VALUE" | docker secret create \
+    --label "checksum=${NEW_HASH}" \
+    --label "managed-by=woodpecker" \
+    "$NAME" - >/dev/null && echo "  [OK]     $NAME" || {
+    echo "  [ERROR]  $NAME: failed to create secret"
+    return 1
+  }
+}