build(docker): pin base container images to immutable digests (#6173)

app/common/src/main/java/stirling/software/common/util/FormUtils.java

@@ -629,11 +629,12 @@ public class FormUtils {
             }
             log.debug("Skipping form fill because document has no AcroForm");
             if (flatten) {
-                flattenEntireDocument(document, null, false);
+                flattenEntireDocument(document, null, false, false);
             }
             return;
         }
 
+        boolean valuesProvided = values != null && !values.isEmpty();
         boolean valuesApplied = false;
         if (values != null && !values.isEmpty()) {
             acroForm.setCacheFields(true);
@@ -679,7 +680,7 @@ public class FormUtils {
         repairWidgetGeometry(document, acroForm);
 
         if (flatten) {
-            flattenEntireDocument(document, acroForm, valuesApplied);
+            flattenEntireDocument(document, acroForm, valuesApplied, valuesProvided);
         }
     }
 
@@ -726,15 +727,16 @@ public class FormUtils {
     // Forcing appearance regeneration via setNeedAppearances(true) drives
     // PDFBox into refreshAppearances inside flatten(), where it can hang on
     // certain documents (PDFBOX-5962). We therefore only regenerate when we
-    // actually wrote new values, or when some widgets are missing appearance
-    // streams and would otherwise flatten blank.
+    // actually wrote new values, or when the request included values and the
+    // document has widgets without appearance streams.
     private void flattenEntireDocument(
-            PDDocument document, PDAcroForm acroForm, boolean valuesWritten) throws IOException {
+            PDDocument document, PDAcroForm acroForm, boolean valuesWritten, boolean valuesProvided)
+            throws IOException {
         if (document == null || acroForm == null) {
             return;
         }
 
-        if (valuesWritten || hasWidgetWithoutAppearance(acroForm)) {
+        if (valuesWritten || (valuesProvided && hasWidgetWithoutAppearance(acroForm))) {
             ensureAppearances(acroForm);
         } else {
             acroForm.setNeedAppearances(false);

docker/base/Dockerfile

@@ -5,7 +5,7 @@
 ARG TARGETPLATFORM
 
 # Stage 1: Build and strip Calibre
-FROM ubuntu:noble AS calibre-build
+FROM ubuntu:noble@sha256:c4a8d5503dfb2a3eb8ab5f807da5bc69a85730fb49b5cfca2330194ebcc41c7b AS calibre-build
 ARG TARGETPLATFORM
 ARG CALIBRE_VERSION=9.4.0
 ARG CALIBRE_STRIP_WEBENGINE=false
@@ -270,7 +270,7 @@ RUN if [ "${CALIBRE_STRIP_WEBENGINE}" = "true" ]; then \
 
 
 # Stage 2: Build Ghostscript from source
-FROM ubuntu:noble AS gs-build
+FROM ubuntu:noble@sha256:c4a8d5503dfb2a3eb8ab5f807da5bc69a85730fb49b5cfca2330194ebcc41c7b AS gs-build
 ARG TARGETPLATFORM
 ARG GS_VERSION=10.06.0
 
@@ -294,7 +294,7 @@ RUN --mount=type=cache,target=/var/cache/apt,sharing=locked \
 
 
 # Stage 3: Build PDF Tools (QPDF and ImageMagick 7)
-FROM ubuntu:noble AS pdf-tools-build
+FROM ubuntu:noble@sha256:c4a8d5503dfb2a3eb8ab5f807da5bc69a85730fb49b5cfca2330194ebcc41c7b AS pdf-tools-build
 ARG TARGETPLATFORM
 ARG QPDF_VERSION=12.3.2
 ARG IM_VERSION=7.1.2-13
@@ -339,7 +339,7 @@ RUN mkdir -p /magick-export/usr/bin \
 
 
 # Stage 4: Build Python venv
-FROM ubuntu:noble AS python-venv-build
+FROM ubuntu:noble@sha256:c4a8d5503dfb2a3eb8ab5f807da5bc69a85730fb49b5cfca2330194ebcc41c7b AS python-venv-build
 ARG TARGETPLATFORM
 ARG UNOSERVER_VERSION=3.6
 
@@ -364,7 +364,7 @@ RUN --mount=type=cache,target=/root/.cache/pip,sharing=locked \
 
 
 # Final runtime image - the actual base image
-FROM eclipse-temurin:25-jre-noble AS runtime
+FROM eclipse-temurin:25-jre-noble@sha256:a051234f864d7ab78bf0188c3c540ac06c711a3b566f00f246be37073cc99dce AS runtime
 
 SHELL ["/bin/bash", "-o", "pipefail", "-c"]
 

docker/embedded/Dockerfile

@@ -5,7 +5,7 @@ ARG BASE_VERSION=1.0.2
 ARG BASE_IMAGE=stirlingtools/stirling-pdf-base:${BASE_VERSION}
 
 # Stage 1: Build the Java application and frontend
-FROM gradle:9.3.1-jdk25 AS app-build
+FROM gradle:9.3.1-jdk25@sha256:85aec999629f4774a383cb792da4b598bdf5a7e69c4b9570bb70c0f919179183 AS app-build
 
 ARG TASK_VERSION=3.49.1
 RUN apt-get update \
@@ -48,7 +48,7 @@ RUN DISABLE_ADDITIONAL_FEATURES=false \
       --no-daemon
 
 # Stage 2: Extract Spring Boot Layers
-FROM eclipse-temurin:25-jre-noble AS jar-extract
+FROM eclipse-temurin:25-jre-noble@sha256:a051234f864d7ab78bf0188c3c540ac06c711a3b566f00f246be37073cc99dce AS jar-extract
 WORKDIR /tmp
 COPY --from=app-build /app/app/core/build/libs/*.jar app.jar
 RUN java -Djarmode=tools -jar app.jar extract --layers --destination /layers

engine/Dockerfile

@@ -1,5 +1,5 @@
 # syntax=docker/dockerfile:1.5
-FROM ghcr.io/astral-sh/uv:python3.13-bookworm-slim
+FROM ghcr.io/astral-sh/uv:python3.13-bookworm-slim@sha256:531f855bda2c73cd6ef67d56b733b357cea384185b3022bd09f05e002cd144ca
 
 ARG TASK_VERSION=3.49.1
 RUN apt-get update \