[GR-65624] Implement layer compatibility checks for environment variables.

Author: Tudor-Stefan Magirescu

substratevm/src/com.oracle.svm.core/src/com/oracle/svm/core/util/EnvVariableUtils.java

@@ -0,0 +1,101 @@
+/*
+ * Copyright (c) 2025, 2025, Oracle and/or its affiliates. All rights reserved.
+ * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
+ *
+ * This code is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License version 2 only, as
+ * published by the Free Software Foundation.  Oracle designates this
+ * particular file as subject to the "Classpath" exception as provided
+ * by Oracle in the LICENSE file that accompanied this code.
+ *
+ * This code is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+ * version 2 for more details (a copy is included in the LICENSE file that
+ * accompanied this code).
+ *
+ * You should have received a copy of the GNU General Public License version
+ * 2 along with this work; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
+ *
+ * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
+ * or visit www.oracle.com if you need additional information or have any
+ * questions.
+ */
+package com.oracle.svm.core.util;
+
+import com.oracle.svm.core.OS;
+
+import java.util.HashSet;
+import java.util.Locale;
+import java.util.Map;
+import java.util.Set;
+
+public class EnvVariableUtils {
+    private static final Set<String> REQUIRED_ENV_VARIABLE_KEYS_COMMON = Set.of(
+                    "PATH",
+                    "PWD",
+                    "HOME",
+                    "LANG",
+                    "LANGUAGE");
+
+    private static final Set<String> REQUIRED_ENV_VARIABLE_KEYS_WINDOWS = Set.of(
+                    "TEMP",
+                    "INCLUDE",
+                    "LIB");
+
+    private static final Set<String> REQUIRED_ENV_VARIABLE_KEYS = getRequiredEnvVariableKeys();
+
+    private static Set<String> getRequiredEnvVariableKeys() {
+        Set<String> requiredEnvVariableKeys = new HashSet<>(REQUIRED_ENV_VARIABLE_KEYS_COMMON);
+        if (OS.WINDOWS.isCurrent()) {
+            requiredEnvVariableKeys.addAll(REQUIRED_ENV_VARIABLE_KEYS_WINDOWS);
+        }
+        return requiredEnvVariableKeys;
+    }
+
+    public record EnvironmentVariable(String key, String value) {
+        public EnvironmentVariable {
+            key = mapKey(key);
+        }
+
+        public static EnvironmentVariable of(Map.Entry<String, String> entry) {
+            return new EnvironmentVariable(entry.getKey(), entry.getValue());
+        }
+
+        public static EnvironmentVariable of(String s) {
+            String[] envVarArr = s.split("=", 2);
+            return new EnvironmentVariable(envVarArr[0], envVarArr[1]);
+        }
+
+        @Override
+        public String toString() {
+            return key + "=" + value;
+        }
+
+        public boolean keyEquals(String otherKey) {
+            return key.equals(mapKey(otherKey));
+        }
+
+        public boolean isKeyRequired() {
+            return isKeyRequiredCondition(key);
+        }
+
+        public static boolean isKeyRequired(String key) {
+            mapKey(key);
+            return isKeyRequiredCondition(key);
+        }
+
+        private static String mapKey(String key) {
+            if (OS.WINDOWS.isCurrent()) {
+                return key.toUpperCase(Locale.ROOT);
+            }
+            return key;
+        }
+
+        private static boolean isKeyRequiredCondition(String key) {
+            // LC_* are locale vars that override LANG for specific categories (or all, with LC_ALL)
+            return REQUIRED_ENV_VARIABLE_KEYS.contains(key) || key.startsWith("LC_");
+        }
+    }
+}

substratevm/src/com.oracle.svm.driver/src/com/oracle/svm/driver/NativeImage.java

@@ -24,6 +24,8 @@
  */
 package com.oracle.svm.driver;
 
+import static com.oracle.svm.core.util.EnvVariableUtils.EnvironmentVariable;
+
 import java.io.BufferedReader;
 import java.io.File;
 import java.io.IOException;
@@ -1979,19 +1981,9 @@ private static void deprecatedSanitizeJVMEnvironment(Map<String, String> environ
     }
 
     private static void sanitizeJVMEnvironment(Map<String, String> environment, Map<String, String> imageBuilderEnvironment) {
-        Set<String> requiredKeys = new HashSet<>(List.of("PATH", "PWD", "HOME", "LANG", "LANGUAGE"));
-        Function<String, String> keyMapper;
-        if (OS.WINDOWS.isCurrent()) {
-            requiredKeys.addAll(List.of("TEMP", "INCLUDE", "LIB"));
-            keyMapper = s -> s.toUpperCase(Locale.ROOT);
-        } else {
-            keyMapper = Function.identity();
-        }
         Map<String, String> restrictedEnvironment = new HashMap<>();
         environment.forEach((key, val) -> {
-            String mappedKey = keyMapper.apply(key);
-            // LC_* are locale vars that override LANG for specific categories (or all, with LC_ALL)
-            if (requiredKeys.contains(mappedKey) || mappedKey.startsWith("LC_")) {
+            if (EnvironmentVariable.isKeyRequired(key)) {
                 restrictedEnvironment.put(key, val);
             }
         });
@@ -2000,8 +1992,9 @@ private static void sanitizeJVMEnvironment(Map<String, String> environment, Map<
             if (entry.getValue() != null) {
                 restrictedEnvironment.put(entry.getKey(), entry.getValue());
             } else {
+                EnvironmentVariable imageBuilderEnvironmentVariable = EnvironmentVariable.of(entry);
                 environment.forEach((key, val) -> {
-                    if (keyMapper.apply(key).equals(keyMapper.apply(entry.getKey()))) {
+                    if (imageBuilderEnvironmentVariable.keyEquals(key)) {
                         /*
                          * Record key as it was given by -E<key-name> (by using `entry.getKey()`
                          * instead of `key`) to allow creating bundles on Windows that will also

substratevm/src/com.oracle.svm.hosted/src/com/oracle/svm/hosted/imagelayer/LayerArchiveSupport.java

@@ -24,6 +24,8 @@
  */
 package com.oracle.svm.hosted.imagelayer;
 
+import static com.oracle.svm.core.util.EnvVariableUtils.EnvironmentVariable;
+
 import java.io.IOException;
 import java.io.OutputStream;
 import java.nio.file.Files;
@@ -37,6 +39,7 @@
 import java.util.Properties;
 
 import com.oracle.svm.core.OS;
+import com.oracle.svm.core.SharedConstants;
 import com.oracle.svm.core.SubstrateUtil;
 import com.oracle.svm.core.util.ArchiveSupport;
 import com.oracle.svm.core.util.UserError;
@@ -49,6 +52,7 @@ public class LayerArchiveSupport {
     private static final int LAYER_FILE_FORMAT_VERSION_MINOR = 1;
 
     private static final String BUILDER_ARGUMENTS_FILE_NAME = "builder-arguments.txt";
+    private static final String ENV_VARIABLES_FILE_NAME = "env-variables.txt";
     private static final String SNAPSHOT_FILE_NAME = "layer-snapshot.lsb";
     private static final String SNAPSHOT_GRAPHS_FILE_NAME = "layer-snapshot-graphs.big";
     private static final String LAYER_INFO_MESSAGE_PREFIX = "Native Image Layers";
@@ -121,6 +125,18 @@ protected Path getBuilderArgumentsFilePath() {
         return layerDir.resolve(BUILDER_ARGUMENTS_FILE_NAME);
     }
 
+    protected Path getEnvVariablesFilePath() {
+        return layerDir.resolve(ENV_VARIABLES_FILE_NAME);
+    }
+
+    protected List<EnvironmentVariable> parseEnvVariables() {
+        return System.getenv().entrySet().stream()
+                        .map(EnvironmentVariable::of)
+                        .filter(envVar -> !envVar.isKeyRequired())
+                        .filter(envVar -> !envVar.keyEquals(SharedConstants.DRIVER_TEMP_DIR_ENV_VARIABLE))
+                        .toList();
+    }
+
     public final class LayerProperties {
 
         private static final String PROPERTY_KEY_LAYER_FILE_VERSION_MAJOR = "LayerFileVersionMajor";

substratevm/src/com.oracle.svm.hosted/src/com/oracle/svm/hosted/imagelayer/LoadLayerArchiveSupport.java

@@ -24,11 +24,14 @@
  */
 package com.oracle.svm.hosted.imagelayer;
 
+import static com.oracle.svm.core.util.EnvVariableUtils.EnvironmentVariable;
+
 import java.io.IOException;
 import java.nio.file.Files;
 import java.nio.file.Path;
 import java.util.ArrayList;
 import java.util.HashMap;
+import java.util.HashSet;
 import java.util.List;
 import java.util.Map;
 import java.util.Set;
@@ -42,6 +45,7 @@
 import com.oracle.svm.core.option.OptionOrigin;
 import com.oracle.svm.core.option.SubstrateOptionsParser;
 import com.oracle.svm.core.util.ArchiveSupport;
+import com.oracle.svm.core.util.EnvVariableUtils;
 import com.oracle.svm.core.util.UserError;
 import com.oracle.svm.core.util.VMError;
 import com.oracle.svm.hosted.NativeImageClassLoaderSupport;
@@ -69,6 +73,16 @@ private void loadBuilderArgumentsFile() {
         }
     }
 
+    private List<EnvironmentVariable> loadEnvironmentVariablesFile() {
+        List<EnvironmentVariable> envVariables = new ArrayList<>();
+        try (Stream<String> lines = Files.lines(getEnvVariablesFilePath())) {
+            lines.map(EnvironmentVariable::of).forEach(envVariables::add);
+            return envVariables;
+        } catch (IOException e) {
+            throw UserError.abort("Unable to load environment variables from file " + getEnvVariablesFilePath());
+        }
+    }
+
     @Override
     protected void validateLayerFile() {
         super.validateLayerFile();
@@ -81,14 +95,15 @@ protected void validateLayerFile() {
     public void verifyCompatibility(NativeImageClassLoaderSupport classLoaderSupport, Map<String, OptionLayerVerificationRequests> allRequests, boolean strict, boolean verbose) {
         Function<String, String> filterFunction = argument -> splitArgumentOrigin(argument).argument;
         boolean violationsFound = false;
-        violationsFound |= verifyCompatibility(builderArguments, classLoaderSupport.getHostedOptionParser().getArguments(), filterFunction, allRequests, strict, verbose, true);
-        violationsFound |= verifyCompatibility(builderArguments, classLoaderSupport.getHostedOptionParser().getArguments(), filterFunction, allRequests, strict, verbose, false);
+        violationsFound |= verifyBuilderArgumentsCompatibility(builderArguments, classLoaderSupport.getHostedOptionParser().getArguments(), filterFunction, allRequests, strict, verbose, true);
+        violationsFound |= verifyBuilderArgumentsCompatibility(builderArguments, classLoaderSupport.getHostedOptionParser().getArguments(), filterFunction, allRequests, strict, verbose, false);
+        violationsFound |= verifyEnvironmentVariablesCompatibility(loadEnvironmentVariablesFile(), parseEnvVariables(), strict, verbose);
         if (violationsFound && verbose) {
             UserError.abort("Verbose LayerOptionVerification failed.");
         }
     }
 
-    private static boolean verifyCompatibility(List<String> previousArgs, List<String> currentArgs, Function<String, String> filterFunction,
+    private static boolean verifyBuilderArgumentsCompatibility(List<String> previousArgs, List<String> currentArgs, Function<String, String> filterFunction,
                     Map<String, OptionLayerVerificationRequests> allRequests, boolean strict, boolean verbose, boolean positional) {
 
         List<String> left;
@@ -203,6 +218,41 @@ private static boolean verifyCompatibility(List<String> previousArgs, List<Strin
         return violationsFound;
     }
 
+    /**
+     * Verifies that the user-specified environment variables in the previous layered image build
+     * are a subset of those used in the current layered image build. The environment variables
+     * obtained via {@link System#getenv()} were previously filtered to include only the
+     * user-specified variables for this verification. This filtering was performed in
+     * {@link LayerArchiveSupport#parseEnvVariables()}, which removed system-dependent variables
+     * defined in {@link EnvVariableUtils}. These excluded variables are required for image builds
+     * but are not considered by this verification, since mismatches between these don't affect
+     * layer compatibility.
+     */
+    private static boolean verifyEnvironmentVariablesCompatibility(List<EnvironmentVariable> previousEnvVars, List<EnvironmentVariable> currentEnvVars, boolean strict, boolean verbose) {
+        Set<EnvironmentVariable> currentEnvVarsSet = new HashSet<>(currentEnvVars);
+        boolean violationsFound = false;
+
+        for (EnvironmentVariable previousEnvVar : previousEnvVars) {
+            if (currentEnvVarsSet.contains(previousEnvVar)) {
+                continue;
+            }
+
+            violationsFound = true;
+            String message = "Current layered image build must set environment variable " + previousEnvVar + " as it was set in the previous layer build.";
+            if (verbose) {
+                LogUtils.info("Error: ", message);
+            } else {
+                if (strict) {
+                    throw UserError.abort(message);
+                } else {
+                    LogUtils.warning(message);
+                }
+            }
+        }
+
+        return violationsFound;
+    }
+
     record ArgumentOrigin(boolean booleanOption, String argument, String origin) {
 
         record NameValue(String name, String value) {

substratevm/src/com.oracle.svm.hosted/src/com/oracle/svm/hosted/imagelayer/WriteLayerArchiveSupport.java

@@ -24,6 +24,8 @@
  */
 package com.oracle.svm.hosted.imagelayer;
 
+import static com.oracle.svm.core.util.EnvVariableUtils.EnvironmentVariable;
+
 import java.io.IOException;
 import java.nio.file.Files;
 import java.nio.file.Path;
@@ -76,13 +78,24 @@ private void writeBuilderArgumentsFile() {
         }
     }
 
+    private void writeEnvVariablesFile() {
+        try {
+            Files.write(getEnvVariablesFilePath(), parseEnvVariables().stream().map(EnvironmentVariable::toString).toList());
+        } catch (IOException e) {
+            throw UserError.abort("Unable to write environment variables to file " + getEnvVariablesFilePath());
+        }
+    }
+
     public void write() {
         try (JarOutputStream jarOutStream = new JarOutputStream(Files.newOutputStream(layerFile), archiveSupport.createManifest())) {
             // disable compression for significant (un)archiving speedup at the cost of file size
             jarOutStream.setLevel(0);
             // write builder arguments file and add to jar
             writeBuilderArgumentsFile();
             archiveSupport.addFileToJar(layerDir, getBuilderArgumentsFilePath(), layerFile, jarOutStream);
+            // write environment variables file and add to jar
+            writeEnvVariablesFile();
+            archiveSupport.addFileToJar(layerDir, getEnvVariablesFilePath(), layerFile, jarOutStream);
             // copy the layer snapshot file and its graphs file to the jar
             archiveSupport.addFileToJar(layerDir, getSnapshotPath(), layerFile, jarOutStream);
             archiveSupport.addFileToJar(layerDir, getSnapshotGraphsPath(), layerFile, jarOutStream);