src/main/java/com/google/devtools/build/lib/sandbox/SandboxStrategy.java

// Copyright 2016 The Bazel Authors. All rights reserved.
//
// 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.devtools.build.lib.sandbox;

import com.google.common.collect.ImmutableSet;
import com.google.common.eventbus.EventBus;
import com.google.devtools.build.lib.actions.ActionExecutionContext;
import com.google.devtools.build.lib.actions.ActionExecutionMetadata;
import com.google.devtools.build.lib.actions.ActionStatusMessage;
import com.google.devtools.build.lib.actions.ExecException;
import com.google.devtools.build.lib.actions.ResourceManager;
import com.google.devtools.build.lib.actions.ResourceManager.ResourceHandle;
import com.google.devtools.build.lib.actions.SandboxedSpawnActionContext;
import com.google.devtools.build.lib.actions.Spawn;
import com.google.devtools.build.lib.actions.SpawnActionContext;
import com.google.devtools.build.lib.actions.Spawns;
import com.google.devtools.build.lib.actions.UserExecException;
import com.google.devtools.build.lib.buildtool.BuildRequest;
import com.google.devtools.build.lib.events.Event;
import com.google.devtools.build.lib.events.EventHandler;
import com.google.devtools.build.lib.runtime.CommandEnvironment;
import com.google.devtools.build.lib.util.io.OutErr;
import com.google.devtools.build.lib.vfs.FileSystem;
import com.google.devtools.build.lib.vfs.Path;
import com.google.devtools.build.lib.vfs.PathFragment;
import java.io.IOException;
import java.util.Map;
import java.util.Set;
import java.util.concurrent.atomic.AtomicReference;

/** Abstract common ancestor for sandbox strategies implementing the common parts. */
abstract class SandboxStrategy implements SandboxedSpawnActionContext {

  private final CommandEnvironment cmdEnv;
  private final BuildRequest buildRequest;
  private final Path execRoot;
  private final Path sandboxBase;
  private final boolean verboseFailures;
  private final SandboxOptions sandboxOptions;
  private final ImmutableSet<Path> inaccessiblePaths;

  public SandboxStrategy(
      CommandEnvironment cmdEnv,
      BuildRequest buildRequest,
      Path sandboxBase,
      boolean verboseFailures,
      SandboxOptions sandboxOptions) {
    this.cmdEnv = cmdEnv;
    this.buildRequest = buildRequest;
    this.execRoot = cmdEnv.getExecRoot();
    this.sandboxBase = sandboxBase;
    this.verboseFailures = verboseFailures;
    this.sandboxOptions = sandboxOptions;

    ImmutableSet.Builder<Path> inaccessiblePaths = ImmutableSet.builder();
    FileSystem fileSystem = cmdEnv.getDirectories().getFileSystem();
    for (String path : sandboxOptions.sandboxBlockPath) {
      Path blockedPath = fileSystem.getPath(path);
      try {
        inaccessiblePaths.add(blockedPath.resolveSymbolicLinks());
      } catch (IOException e) {
        // It's OK to block access to an invalid symlink. In this case we'll just make the symlink
        // itself inaccessible, instead of the target, though.
        inaccessiblePaths.add(blockedPath);
      }
    }
    this.inaccessiblePaths = inaccessiblePaths.build();
  }

  /** Executes the given {@code spawn}. */
  @Override
  public void exec(Spawn spawn, ActionExecutionContext actionExecutionContext)
      throws ExecException, InterruptedException {
    exec(spawn, actionExecutionContext, null);
  }

  @Override
  public void exec(
      Spawn spawn,
      ActionExecutionContext actionExecutionContext,
      AtomicReference<Class<? extends SpawnActionContext>> writeOutputFiles)
      throws ExecException, InterruptedException {
    // Certain actions can't run remotely or in a sandbox - pass them on to the standalone strategy.
    if (!spawn.isRemotable() || spawn.hasNoSandbox()) {
      SandboxHelpers.fallbackToNonSandboxedExecution(spawn, actionExecutionContext);
      return;
    }

    EventBus eventBus = actionExecutionContext.getEventBus();
    ActionExecutionMetadata owner = spawn.getResourceOwner();
    eventBus.post(ActionStatusMessage.schedulingStrategy(owner));
    try (ResourceHandle ignored =
        ResourceManager.instance().acquireResources(owner, spawn.getLocalResources())) {
      actuallyExec(spawn, actionExecutionContext, writeOutputFiles);
    } catch (IOException e) {
      throw new UserExecException("I/O exception during sandboxed execution", e);
    }
  }

  protected abstract void actuallyExec(
      Spawn spawn,
      ActionExecutionContext actionExecutionContext,
      AtomicReference<Class<? extends SpawnActionContext>> writeOutputFiles)
      throws ExecException, InterruptedException, IOException;

  protected void runSpawn(
      Spawn spawn,
      ActionExecutionContext actionExecutionContext,
      Map<String, String> spawnEnvironment,
      SandboxExecRoot sandboxExecRoot,
      Set<PathFragment> outputs,
      SandboxRunner runner,
      AtomicReference<Class<? extends SpawnActionContext>> writeOutputFiles)
      throws ExecException, InterruptedException {
    EventHandler eventHandler = actionExecutionContext.getEventHandler();
    ExecException execException = null;
    OutErr outErr = actionExecutionContext.getFileOutErr();
    try {
      runner.run(
          cmdEnv,
          spawn.getArguments(),
          spawnEnvironment,
          outErr,
          Spawns.getTimeoutSeconds(spawn),
          SandboxHelpers.shouldAllowNetwork(buildRequest, spawn),
          sandboxOptions.sandboxDebug,
          sandboxOptions.sandboxFakeHostname,
          sandboxOptions.sandboxFakeUsername);
    } catch (ExecException e) {
      execException = e;
    }

    if (writeOutputFiles != null && !writeOutputFiles.compareAndSet(null, SandboxStrategy.class)) {
      throw new InterruptedException();
    }

    try {
      // We copy the outputs even when the command failed, otherwise StandaloneTestStrategy
      // won't be able to get the test logs of a failed test. (We should probably do this in
      // some better way.)
      sandboxExecRoot.copyOutputs(execRoot, outputs);
    } catch (IOException e) {
      if (execException == null) {
        throw new UserExecException("Could not move output artifacts from sandboxed execution", e);
      } else {
        // Catch the IOException and turn it into an error message, otherwise this might hide an
        // exception thrown during runner.run earlier.
        eventHandler.handle(
            Event.error(
                "I/O exception while extracting output artifacts from sandboxed execution: " + e));
      }
    }

    if (execException != null) {
      outErr.printErr(
          "Use --strategy="
          + spawn.getMnemonic()
          + "=standalone to disable sandboxing for the failing actions.\n");
      throw execException;
    }
  }

  /**
   * Returns a temporary directory that should be used as the sandbox directory for a single action.
   */
  protected Path getSandboxRoot() throws IOException {
    return sandboxBase.getRelative(
        java.nio.file.Files.createTempDirectory(
                java.nio.file.Paths.get(sandboxBase.getPathString()), "")
            .getFileName()
            .toString());
  }

  /**
   * Gets the list of directories that the spawn will assume to be writable.
   *
   * @throws IOException because we might resolve symlinks, which throws {@link IOException}.
   */
  protected ImmutableSet<Path> getWritableDirs(Path sandboxExecRoot, Map<String, String> env)
      throws IOException {
    // We have to make the TEST_TMPDIR directory writable if it is specified.
    ImmutableSet.Builder<Path> writablePaths = ImmutableSet.builder();
    writablePaths.add(sandboxExecRoot);
    if (env.containsKey("TEST_TMPDIR")) {
      // We add this even though it may be below sandboxExecRoot (and thus would already be writable
      // as a subpath) to take advantage of the side-effect that SymlinkedExecRoot also creates this
      // needed directory if it doesn't exist yet.
      writablePaths.add(sandboxExecRoot.getRelative(env.get("TEST_TMPDIR")));
    }

    FileSystem fileSystem = sandboxExecRoot.getFileSystem();
    for (String writablePath : sandboxOptions.sandboxWritablePath) {
      writablePaths.add(fileSystem.getPath(writablePath));
    }

    return writablePaths.build();
  }

  protected ImmutableSet<Path> getInaccessiblePaths() {
    return inaccessiblePaths;
  }

  @Override
  public String toString() {
    return "sandboxed";
  }

  @Override
  public boolean shouldPropagateExecException() {
    return verboseFailures && sandboxOptions.sandboxDebug;
  }
}