Add a micro scp daemon to our SSHD

This daemon can host static files contained within the Gerrit JAR,
for clients to download via scp.  The idea is to make utilities
easily available for download from the command line.

Signed-off-by: Shawn O. Pearce <sop@google.com>

pom.xml

@@ -268,6 +268,7 @@ limitations under the License.
         <includes>
           <include>log4j.properties</include>
           <include>com/google/gerrit/client/GerritVersion.properties</include>
+          <include>com/google/gerrit/server/ssh/scproot/**</include>
         </includes>
       </resource>
     </resources>

src/main/java/com/google/gerrit/server/ssh/GerritCommandFactory.java

@@ -98,6 +98,8 @@ class GerritCommandFactory implements CommandFactory {
         cmd += args;
         args = "";
       }
+    } else if ("scp".equals(cmd)) {
+      return new ScpCommand(args.split(" "));
     }
 
     final AbstractCommand c = create(cmd);

src/main/java/com/google/gerrit/server/ssh/ScpCommand.java

@@ -0,0 +1,335 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements. See the NOTICE file distributed with this
+ * work for additional information regarding copyright ownership. The ASF
+ * licenses this file to you 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.
+ */
+
+/*
+ * NB: This code was primarly ripped out of MINA SSHD.
+ * 
+ * @author <a href="mailto:dev@mina.apache.org">Apache MINA SSHD Project</a>
+ */
+package com.google.gerrit.server.ssh;
+
+import org.apache.sshd.server.CommandFactory;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+import java.io.BufferedReader;
+import java.io.ByteArrayInputStream;
+import java.io.ByteArrayOutputStream;
+import java.io.FileNotFoundException;
+import java.io.IOException;
+import java.io.InputStream;
+import java.io.InputStreamReader;
+import java.io.OutputStream;
+import java.io.UnsupportedEncodingException;
+import java.util.ArrayList;
+import java.util.List;
+import java.util.TreeMap;
+
+class ScpCommand implements CommandFactory.Command, Runnable {
+  private static final String TYPE_DIR = "D";
+  private static final String TYPE_FILE = "C";
+  private static final Logger log = LoggerFactory.getLogger(ScpCommand.class);
+
+  private boolean opt_r;
+  private boolean opt_t;
+  private boolean opt_f;
+  private boolean opt_v;
+  private boolean opt_p;
+  private String root;
+
+  private TreeMap<String, Entry> toc;
+  private InputStream in;
+  private OutputStream out;
+  private OutputStream err;
+  private CommandFactory.ExitCallback callback;
+  private IOException error;
+
+  public ScpCommand(final String[] args) {
+    root = "";
+    for (int i = 0; i < args.length; i++) {
+      if (args[i].charAt(0) == '-') {
+        for (int j = 1; j < args[i].length(); j++) {
+          switch (args[i].charAt(j)) {
+            case 'f':
+              opt_f = true;
+              break;
+            case 'p':
+              opt_p = true;
+              break;
+            case 'r':
+              opt_r = true;
+              break;
+            case 't':
+              opt_t = true;
+              break;
+            case 'v':
+              opt_v = true;
+              break;
+          }
+        }
+      } else if (i == args.length - 1) {
+        root = args[args.length - 1];
+      }
+    }
+    if (!opt_f && !opt_t) {
+      error = new IOException("Either -f or -t option should be set");
+    }
+  }
+
+  public void setInputStream(InputStream in) {
+    this.in = in;
+  }
+
+  public void setOutputStream(OutputStream out) {
+    this.out = out;
+  }
+
+  public void setErrorStream(OutputStream err) {
+    this.err = err;
+  }
+
+  public void setExitCallback(CommandFactory.ExitCallback callback) {
+    this.callback = callback;
+  }
+
+  public void start() throws IOException {
+    if (error != null) {
+      throw error;
+    }
+    new Thread(this).start();
+  }
+
+  public void run() {
+    try {
+      readToc();
+      if (opt_f) {
+        if (root.startsWith("/")) {
+          root = root.substring(1);
+        }
+        if (root.endsWith("/")) {
+          root = root.substring(0, root.length() - 1);
+        }
+        if (root.equals(".")) {
+          root = "";
+        }
+
+        final Entry ent = toc.get(root);
+        if (ent == null) {
+          throw new IOException(root + " not found");
+
+        } else if (TYPE_FILE.equals(ent.type)) {
+          readFile(ent);
+
+        } else if (TYPE_DIR.equals(ent.type)) {
+          if (!opt_r) {
+            throw new IOException(root + " not a regular file");
+          }
+          readDir(ent);
+        } else {
+          throw new IOException(root + " not supported");
+        }
+      } else {
+        throw new IOException("Unsupported mode");
+      }
+    } catch (IOException e) {
+      try {
+        out.write(2);
+        out.write(e.getMessage().getBytes());
+        out.write('\n');
+        out.flush();
+      } catch (IOException e2) {
+        // Ignore
+      }
+      log.debug("Error in scp command", e);
+    } finally {
+      callback.onExit(0);
+    }
+  }
+
+  private void readToc() throws IOException {
+    toc = new TreeMap<String, Entry>();
+    final BufferedReader br =
+        new BufferedReader(new InputStreamReader(new ByteArrayInputStream(
+            read("TOC")), "UTF-8"));
+    String line;
+    while ((line = br.readLine()) != null) {
+      if (line.length() > 0 && !line.startsWith("#")) {
+        final Entry e = new Entry(TYPE_FILE, line);
+        toc.put(e.path, e);
+      }
+    }
+
+    final List<Entry> all = new ArrayList<Entry>(toc.values());
+    for (Entry e : all) {
+      String path = dirOf(e.path);
+      while (path != null) {
+        Entry d = toc.get(path);
+        if (d == null) {
+          d = new Entry(TYPE_DIR, 0755, path);
+          toc.put(d.path, d);
+        }
+        d.children.add(e);
+        path = dirOf(path);
+        e = d;
+      }
+    }
+
+    final Entry top = new Entry(TYPE_DIR, 0755, "");
+    for (Entry e : toc.values()) {
+      if (dirOf(e.path) == null) {
+        top.children.add(e);
+      }
+    }
+    toc.put(top.path, top);
+  }
+
+  private String readLine() throws IOException {
+    ByteArrayOutputStream baos = new ByteArrayOutputStream();
+    for (;;) {
+      int c = in.read();
+      if (c == '\n') {
+        return baos.toString();
+      } else if (c == -1) {
+        throw new IOException("End of stream");
+      } else {
+        baos.write(c);
+      }
+    }
+  }
+
+  private static String nameOf(String path) {
+    final int s = path.lastIndexOf('/');
+    return s < 0 ? path : path.substring(s + 1);
+  }
+
+  private static String dirOf(String path) {
+    final int s = path.lastIndexOf('/');
+    return s < 0 ? null : path.substring(0, s);
+  }
+
+  private static byte[] read(String path) {
+    final InputStream in =
+        ScpCommand.class.getClassLoader().getResourceAsStream(
+            "com/google/gerrit/server/ssh/scproot/" + path);
+    if (in == null) {
+      return null;
+    }
+    try {
+      final ByteArrayOutputStream out = new ByteArrayOutputStream();
+      try {
+        final byte[] buf = new byte[8192];
+        int n;
+        while ((n = in.read(buf, 0, buf.length)) > 0) {
+          out.write(buf, 0, n);
+        }
+      } finally {
+        in.close();
+      }
+      return out.toByteArray();
+    } catch (Exception e) {
+      log.debug("Cannot read " + path, e);
+      return null;
+    }
+  }
+
+  private void readFile(final Entry ent) throws IOException {
+    final byte[] data = read(ent.path);
+    if (data == null) {
+      throw new FileNotFoundException(ent.path);
+    }
+
+    header(ent, data.length);
+    readAck();
+
+    out.write(data);
+    ack();
+    readAck();
+  }
+
+  private void readDir(final Entry dir) throws IOException {
+    header(dir, 0);
+    readAck();
+
+    for (Entry e : dir.children) {
+      if (TYPE_DIR.equals(e.type)) {
+        readDir(e);
+      } else {
+        readFile(e);
+      }
+    }
+
+    out.write("E\n".getBytes("UTF-8"));
+    out.flush();
+    readAck();
+  }
+
+  private void header(final Entry dir, final int len) throws IOException,
+      UnsupportedEncodingException {
+    final StringBuilder buf = new StringBuilder();
+    buf.append(dir.type);
+    buf.append(dir.mode); // perms
+    buf.append(" ");
+    buf.append(len); // length
+    buf.append(" ");
+    buf.append(nameOf(dir.path));
+    buf.append("\n");
+    out.write(buf.toString().getBytes("UTF-8"));
+    out.flush();
+  }
+
+  private void ack() throws IOException {
+    out.write(0);
+    out.flush();
+  }
+
+  private void readAck() throws IOException {
+    switch (in.read()) {
+      case 0:
+        break;
+      case 1:
+        log.debug("Received warning: " + readLine());
+        break;
+      case 2:
+        throw new IOException("Received nack: " + readLine());
+    }
+  }
+
+  private static class Entry {
+    String type;
+    String mode;
+    String path;
+    List<Entry> children;
+
+    Entry(String type, String line) {
+      this.type = type;
+      int s = line.indexOf(' ');
+      mode = line.substring(0, s);
+      path = line.substring(s + 1);
+
+      if (!mode.startsWith("0")) {
+        mode = "0" + mode;
+      }
+    }
+
+    Entry(String type, int mode, String path) {
+      this.type = type;
+      this.mode = "0" + Integer.toOctalString(mode);
+      this.path = path;
+      this.children = new ArrayList<Entry>();
+    }
+  }
+}

src/main/java/com/google/gerrit/server/ssh/scproot/TOC

@@ -0,0 +1,3 @@
+# Format of this file is:
+#   mode <SPACE> fullpath
+#