task-151: 路径安全校验（PathSafetyGuard 规范化 startsWith 判定、../与绝对路径与符号链接逃逸拒绝、接入清理路径）+ 8 条测试

backend-java/src/main/java/com/nanri/aiimage/modules/file/service/LocalTempCleanupService.java

@@ -57,6 +57,11 @@ public class LocalTempCleanupService {
 
         for (File child : children) {
             try {
+                // 路径安全：child 必须位于临时根目录内（防穿越/符号链接逃逸），否则跳过并告警
+                if (!PathSafetyGuard.isInside(tempDir, child)) {
+                    log.warn("local temp cleanup skipped unsafe path: {}", child.getAbsolutePath());
+                    continue;
+                }
                 if (child.isFile() && isManagedRootTempFile(child) && isExpired(child, sourceExpireBefore)) {
                     if (FileUtil.del(child)) {
                         deletedSourceCount++;
@@ -89,6 +94,9 @@ public class LocalTempCleanupService {
             File[] children = file.listFiles();
             if (children != null) {
                 for (File child : children) {
+                    if (!PathSafetyGuard.isInside(file, child)) {
+                        continue;
+                    }
                     deletedCount += deleteExpiredChildrenRecursively(child, expireBefore);
                 }
             }

backend-java/src/main/java/com/nanri/aiimage/modules/file/service/PathSafetyGuard.java

@@ -0,0 +1,54 @@
+package com.nanri.aiimage.modules.file.service;
+
+import java.io.File;
+import java.io.IOException;
+import java.nio.file.Path;
+
+/**
+ * 临时文件删除前的路径安全校验（task-151）。
+ *
+ * 删除前校验：child 规范化后必须位于 root 内（startsWith(root) 且不等于 root）；
+ * 穿越（../、绝对路径逃逸、符号链接逃逸）拒绝；null/非法输入返回 false。
+ * 符号链接用 toRealPath 解析（存在时），防止链接指向根外文件被误删。
+ */
+public final class PathSafetyGuard {
+
+    private PathSafetyGuard() {
+    }
+
+    /**
+     * child 是否位于 root 内（规范化比较；root 本身不算内部）。
+     * 路径不存在时以 toAbsolutePath().normalize() 兜底，存在时优先 toRealPath
+     * 解析符号链接。
+     */
+    public static boolean isInside(File root, File child) {
+        if (root == null || child == null) {
+            return false;
+        }
+        Path rootPath = resolve(root);
+        Path childPath = resolve(child);
+        if (rootPath == null || childPath == null) {
+            return false;
+        }
+        return childPath.startsWith(rootPath) && !childPath.equals(rootPath);
+    }
+
+    /** 路径名是否含穿越特征（../、绝对路径、盘符、反斜杠）。 */
+    public static boolean isTraversal(String name) {
+        if (name == null || name.isBlank()) {
+            return true;
+        }
+        return name.contains("..")
+                || name.startsWith("/")
+                || name.matches("^[A-Za-z]:.*")
+                || name.contains("\\");
+    }
+
+    private static Path resolve(File file) {
+        try {
+            return file.toPath().toRealPath();
+        } catch (IOException ex) {
+            return file.toPath().toAbsolutePath().normalize();
+        }
+    }
+}

backend-java/src/test/java/com/nanri/aiimage/modules/file/service/PathSafetyGuardTest.java

@@ -0,0 +1,97 @@
+package com.nanri.aiimage.modules.file.service;
+
+import org.junit.jupiter.api.Test;
+import org.junit.jupiter.api.io.TempDir;
+
+import java.io.File;
+import java.nio.file.Files;
+import java.nio.file.Path;
+
+import static org.junit.jupiter.api.Assertions.assertFalse;
+import static org.junit.jupiter.api.Assertions.assertTrue;
+
+/**
+ * task-151：路径安全校验契约（plan 09）。
+ * 删除前校验：child 规范化后 startsWith(临时根目录) 且不等于根；
+ * 穿越（../、绝对路径逃逸、符号链接逃逸）拒绝；非法输入安全返回 false。
+ */
+class PathSafetyGuardTest {
+
+    @TempDir
+    Path tempDir;
+
+    @Test
+    void insideRootIsAllowed() throws Exception {
+        Path child = tempDir.resolve("a.tmp");
+        Files.writeString(child, "x");
+
+        assertTrue(PathSafetyGuard.isInside(tempDir.toFile(), child.toFile()));
+    }
+
+    @Test
+    void nestedDirectoryInsideRootIsAllowed() throws Exception {
+        Path nested = tempDir.resolve("result/2026/09").resolve("f.tmp");
+        Files.createDirectories(nested.getParent());
+        Files.writeString(nested, "x");
+
+        assertTrue(PathSafetyGuard.isInside(tempDir.toFile(), nested.toFile()));
+    }
+
+    @Test
+    void parentTraversalIsRejected() {
+        assertTrue(PathSafetyGuard.isTraversal("../escape"));
+        assertTrue(PathSafetyGuard.isTraversal("a/../../b"));
+        assertFalse(PathSafetyGuard.isTraversal("normal-file.tmp"));
+    }
+
+    @Test
+    void absolutePathEscapeIsRejected() {
+        assertTrue(PathSafetyGuard.isTraversal("/etc/passwd"));
+        assertTrue(PathSafetyGuard.isTraversal("C:\\windows\\x"));
+        assertTrue(PathSafetyGuard.isTraversal("D:/escape"));
+    }
+
+    @Test
+    void outsideRootIsRejected() throws Exception {
+        Path outside = tempDir.getParent().resolve("outside-" + System.nanoTime() + ".tmp");
+        Files.writeString(outside, "x");
+        try {
+            assertFalse(PathSafetyGuard.isInside(tempDir.toFile(), outside.toFile()),
+                    "根外路径必须拒绝");
+        } finally {
+            Files.deleteIfExists(outside);
+        }
+    }
+
+    @Test
+    void symlinkEscapeIsRejected() throws Exception {
+        Path outside = tempDir.getParent().resolve("symlink-target-" + System.nanoTime() + ".tmp");
+        Files.writeString(outside, "secret");
+        Path link = tempDir.resolve("link.tmp");
+        try {
+            Files.createSymbolicLink(link, outside);
+            assertFalse(PathSafetyGuard.isInside(tempDir.toFile(), link.toFile()),
+                    "符号链接指向根外必须拒绝（toRealPath 解析）");
+        } catch (UnsupportedOperationException | java.io.IOException ex) {
+            // 平台不支持符号链接时跳过
+        } finally {
+            Files.deleteIfExists(link);
+            Files.deleteIfExists(outside);
+        }
+    }
+
+    @Test
+    void rootItselfIsNotDeletable() {
+        assertFalse(PathSafetyGuard.isInside(tempDir.toFile(), tempDir.toFile()),
+                "根目录本身不算内部（禁止删根）");
+    }
+
+    @Test
+    void nullAndBlankAreSafe() {
+        assertFalse(PathSafetyGuard.isInside(null, null));
+        assertFalse(PathSafetyGuard.isInside(tempDir.toFile(), null));
+        assertFalse(PathSafetyGuard.isInside(null, tempDir.toFile()));
+        assertTrue(PathSafetyGuard.isTraversal(null));
+        assertTrue(PathSafetyGuard.isTraversal("   "));
+    }
+}