1 files changed, 335 insertions, 0 deletions
diff --git a/java/com/google/gerrit/httpd/raw/ResourceServlet.java b/java/com/google/gerrit/httpd/raw/ResourceServlet.java
new file mode 100644
index 0000000000..4b44af45f7
--- /dev/null
+++ b/java/com/google/gerrit/httpd/raw/ResourceServlet.java
@@ -0,0 +1,335 @@
+// Copyright (C) 2015 The Android Open Source Project
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package com.google.gerrit.httpd.raw;
+
+import static com.google.common.net.HttpHeaders.CONTENT_ENCODING;
+import static com.google.common.net.HttpHeaders.ETAG;
+import static com.google.common.net.HttpHeaders.IF_MODIFIED_SINCE;
+import static com.google.common.net.HttpHeaders.IF_NONE_MATCH;
+import static com.google.common.net.HttpHeaders.LAST_MODIFIED;
+import static java.util.Objects.requireNonNull;
+import static java.util.concurrent.TimeUnit.DAYS;
+import static java.util.concurrent.TimeUnit.MINUTES;
+import static javax.servlet.http.HttpServletResponse.SC_INTERNAL_SERVER_ERROR;
+import static javax.servlet.http.HttpServletResponse.SC_NOT_FOUND;
+import static javax.servlet.http.HttpServletResponse.SC_NOT_MODIFIED;
+
+import com.google.common.annotations.VisibleForTesting;
+import com.google.common.base.CharMatcher;
+import com.google.common.cache.Cache;
+import com.google.common.collect.ImmutableMap;
+import com.google.common.flogger.FluentLogger;
+import com.google.common.hash.Hashing;
+import com.google.gerrit.common.Nullable;
+import com.google.gerrit.httpd.HtmlDomUtil;
+import com.google.gerrit.server.UsedAt;
+import com.google.gerrit.util.http.CacheHeaders;
+import com.google.gwtjsonrpc.server.RPCServletUtils;
+import java.io.IOException;
+import java.io.OutputStream;
+import java.nio.file.Files;
+import java.nio.file.NoSuchFileException;
+import java.nio.file.Path;
+import java.nio.file.attribute.FileTime;
+import java.util.concurrent.Callable;
+import java.util.concurrent.ExecutionException;
+import java.util.zip.GZIPOutputStream;
+import javax.servlet.http.HttpServlet;
+import javax.servlet.http.HttpServletRequest;
+import javax.servlet.http.HttpServletResponse;
+
+/**
+ * Base class for serving static resources.
+ *
+ * <p>Supports caching, ETags, basic content type detection, and limited gzip compression.
+ */
+public abstract class ResourceServlet extends HttpServlet {
+  private static final long serialVersionUID = 1L;
+
+  private static final FluentLogger logger = FluentLogger.forEnclosingClass();
+
+  private static final int CACHE_FILE_SIZE_LIMIT_BYTES = 100 << 10;
+
+  private static final String JS = "application/x-javascript";
+  private static final ImmutableMap<String, String> MIME_TYPES =
+      ImmutableMap.<String, String>builder()
+          .put("css", "text/css")
+          .put("gif", "image/gif")
+          .put("htm", "text/html")
+          .put("html", "text/html")
+          .put("ico", "image/x-icon")
+          .put("jpeg", "image/jpeg")
+          .put("jpg", "image/jpeg")
+          .put("js", JS)
+          .put("pdf", "application/pdf")
+          .put("png", "image/png")
+          .put("rtf", "text/rtf")
+          .put("svg", "image/svg+xml")
+          .put("text", "text/plain")
+          .put("tif", "image/tiff")
+          .put("tiff", "image/tiff")
+          .put("txt", "text/plain")
+          .put("woff", "font/woff")
+          .put("woff2", "font/woff2")
+          .build();
+
+  protected static String contentType(String name) {
+    int dot = name.lastIndexOf('.');
+    String ext = 0 < dot ? name.substring(dot + 1) : "";
+    String type = MIME_TYPES.get(ext);
+    return type != null ? type : "application/octet-stream";
+  }
+
+  private final Cache<Path, Resource> cache;
+  private final boolean refresh;
+  private final boolean cacheOnClient;
+  private final int cacheFileSizeLimitBytes;
+
+  protected ResourceServlet(Cache<Path, Resource> cache, boolean refresh) {
+    this(cache, refresh, true, CACHE_FILE_SIZE_LIMIT_BYTES);
+  }
+
+  protected ResourceServlet(Cache<Path, Resource> cache, boolean refresh, boolean cacheOnClient) {
+    this(cache, refresh, cacheOnClient, CACHE_FILE_SIZE_LIMIT_BYTES);
+  }
+
+  @VisibleForTesting
+  ResourceServlet(
+      Cache<Path, Resource> cache,
+      boolean refresh,
+      boolean cacheOnClient,
+      int cacheFileSizeLimitBytes) {
+    this.cache = requireNonNull(cache, "cache");
+    this.refresh = refresh;
+    this.cacheOnClient = cacheOnClient;
+    this.cacheFileSizeLimitBytes = cacheFileSizeLimitBytes;
+  }
+
+  /**
+   * Get the resource path on the filesystem that should be served for this request.
+   *
+   * @param pathInfo result of {@link HttpServletRequest#getPathInfo()}.
+   * @return path where static content can be found.
+   * @throws IOException if an error occurred resolving the resource.
+   */
+  protected abstract Path getResourcePath(String pathInfo) throws IOException;
+
+  protected FileTime getLastModifiedTime(Path p) throws IOException {
+    return Files.getLastModifiedTime(p);
+  }
+
+  @Override
+  protected void doGet(HttpServletRequest req, HttpServletResponse rsp) throws IOException {
+    String name;
+    if (req.getPathInfo() == null) {
+      name = "/";
+    } else {
+      name = CharMatcher.is('/').trimFrom(req.getPathInfo());
+    }
+    if (isUnreasonableName(name)) {
+      notFound(rsp);
+      return;
+    }
+    Path p = getResourcePath(name);
+    if (p == null) {
+      notFound(rsp);
+      return;
+    }
+
+    Resource r = cache.getIfPresent(p);
+    try {
+      if (r == null) {
+        if (maybeStream(p, req, rsp)) {
+          return; // Bypass cache for large resource.
+        }
+        r = cache.get(p, newLoader(p));
+      }
+      if (refresh && r.isStale(p, this)) {
+        cache.invalidate(p);
+        r = cache.get(p, newLoader(p));
+      }
+    } catch (ExecutionException e) {
+      logger.atWarning().withCause(e).log("Cannot load static resource %s", req.getPathInfo());
+      CacheHeaders.setNotCacheable(rsp);
+      rsp.setStatus(SC_INTERNAL_SERVER_ERROR);
+      return;
+    }
+    if (r == Resource.NOT_FOUND) {
+      notFound(rsp); // Cached not found response.
+      return;
+    }
+
+    String e = req.getParameter("e");
+    if (e != null && !r.etag.equals(e)) {
+      CacheHeaders.setNotCacheable(rsp);
+      rsp.setStatus(SC_NOT_FOUND);
+      return;
+    } else if (cacheOnClient && r.etag.equals(req.getHeader(IF_NONE_MATCH))) {
+      rsp.setStatus(SC_NOT_MODIFIED);
+      return;
+    }
+
+    byte[] tosend = r.raw;
+    if (!r.contentType.equals(JS) && RPCServletUtils.acceptsGzipEncoding(req)) {
+      byte[] gz = HtmlDomUtil.compress(tosend);
+      if ((gz.length + 24) < tosend.length) {
+        rsp.setHeader(CONTENT_ENCODING, "gzip");
+        tosend = gz;
+      }
+    }
+
+    if (cacheOnClient) {
+      rsp.setHeader(ETAG, r.etag);
+    } else {
+      CacheHeaders.setNotCacheable(rsp);
+    }
+    if (!CacheHeaders.hasCacheHeader(rsp)) {
+      if (e != null && r.etag.equals(e)) {
+        CacheHeaders.setCacheable(req, rsp, 360, DAYS, false);
+      } else {
+        CacheHeaders.setCacheable(req, rsp, 15, MINUTES, refresh);
+      }
+    }
+    rsp.setContentType(r.contentType);
+    rsp.setContentLength(tosend.length);
+    try (OutputStream out = rsp.getOutputStream()) {
+      out.write(tosend);
+    }
+  }
+
+  @Nullable
+  Resource getResource(String name) {
+    try {
+      Path p = getResourcePath(name);
+      if (p == null) {
+        logger.atWarning().log("Path doesn't exist %s", name);
+        return null;
+      }
+      return cache.get(p, newLoader(p));
+    } catch (ExecutionException | IOException e) {
+      logger.atWarning().withCause(e).log("Cannot load static resource %s", name);
+      return null;
+    }
+  }
+
+  private static void notFound(HttpServletResponse rsp) {
+    rsp.setStatus(SC_NOT_FOUND);
+    CacheHeaders.setNotCacheable(rsp);
+  }
+
+  /**
+   * Maybe stream a path to the response, depending on the properties of the file and cache headers
+   * in the request.
+   *
+   * @param p path to stream
+   * @param req HTTP request.
+   * @param rsp HTTP response.
+   * @return true if the response was written (either the file contents or an error); false if the
+   *     path is too small to stream and should be cached.
+   */
+  private boolean maybeStream(Path p, HttpServletRequest req, HttpServletResponse rsp)
+      throws IOException {
+    try {
+      if (Files.size(p) < cacheFileSizeLimitBytes) {
+        return false;
+      }
+    } catch (NoSuchFileException e) {
+      cache.put(p, Resource.NOT_FOUND);
+      notFound(rsp);
+      return true;
+    }
+
+    long lastModified = getLastModifiedTime(p).toMillis();
+    if (req.getDateHeader(IF_MODIFIED_SINCE) >= lastModified) {
+      rsp.setStatus(SC_NOT_MODIFIED);
+      return true;
+    }
+
+    if (lastModified > 0) {
+      rsp.setDateHeader(LAST_MODIFIED, lastModified);
+    }
+    if (!CacheHeaders.hasCacheHeader(rsp)) {
+      CacheHeaders.setCacheable(req, rsp, 15, MINUTES, refresh);
+    }
+    rsp.setContentType(contentType(p.toString()));
+
+    OutputStream out = rsp.getOutputStream();
+    GZIPOutputStream gz = null;
+    if (RPCServletUtils.acceptsGzipEncoding(req)) {
+      rsp.setHeader(CONTENT_ENCODING, "gzip");
+      gz = new GZIPOutputStream(out);
+      out = gz;
+    }
+    Files.copy(p, out);
+    if (gz != null) {
+      gz.finish();
+    }
+    return true;
+  }
+
+  private static boolean isUnreasonableName(String name) {
+    return name.length() < 1
+        || name.contains("\\") // no windows/dos style paths
+        || name.startsWith("../") // no "../etc/passwd"
+        || name.contains("/../") // no "foo/../etc/passwd"
+        || name.contains("/./") // "foo/./foo" is insane to ask
+        || name.contains("//"); // windows UNC path can be "//..."
+  }
+
+  private Callable<Resource> newLoader(Path p) {
+    return () -> {
+      try {
+        return new Resource(
+            getLastModifiedTime(p), contentType(p.toString()), Files.readAllBytes(p));
+      } catch (NoSuchFileException e) {
+        return Resource.NOT_FOUND;
+      }
+    };
+  }
+
+  public static class Resource {
+    static final Resource NOT_FOUND = new Resource(FileTime.fromMillis(0), "", new byte[] {});
+
+    final FileTime lastModified;
+    final String contentType;
+    final String etag;
+    final byte[] raw;
+
+    Resource(FileTime lastModified, String contentType, byte[] raw) {
+      this.lastModified = requireNonNull(lastModified, "lastModified");
+      this.contentType = requireNonNull(contentType, "contentType");
+      this.raw = requireNonNull(raw, "raw");
+      this.etag = Hashing.murmur3_128().hashBytes(raw).toString();
+    }
+
+    boolean isStale(Path p, ResourceServlet rs) throws IOException {
+      FileTime t;
+      try {
+        t = rs.getLastModifiedTime(p);
+      } catch (NoSuchFileException e) {
+        return this != NOT_FOUND;
+      }
+      return t.toMillis() == 0 || lastModified.toMillis() == 0 || !lastModified.equals(t);
+    }
+  }
+
+  @UsedAt(UsedAt.Project.GOOGLE)
+  public static class Weigher implements com.google.common.cache.Weigher<Path, Resource> {
+    @Override
+    public int weigh(Path p, Resource r) {
+      return 2 * p.toString().length() + r.raw.length;
+    }
+  }
+}