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// Copyright 2014 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.ImmutableList;
import com.google.common.collect.ImmutableMap;
import com.google.common.collect.ImmutableSet;
import com.google.common.collect.Maps;
import com.google.common.io.ByteStreams;
import com.google.devtools.build.lib.actions.ExecException;
import com.google.devtools.build.lib.actions.ExecutionRequirements;
import com.google.devtools.build.lib.actions.Spawn;
import com.google.devtools.build.lib.actions.Spawns;
import com.google.devtools.build.lib.actions.UserExecException;
import com.google.devtools.build.lib.analysis.BlazeDirectories;
import com.google.devtools.build.lib.exec.TreeDeleter;
import com.google.devtools.build.lib.exec.local.LocalEnvProvider;
import com.google.devtools.build.lib.exec.local.PosixLocalEnvProvider;
import com.google.devtools.build.lib.profiler.Profiler;
import com.google.devtools.build.lib.profiler.SilentCloseable;
import com.google.devtools.build.lib.runtime.CommandEnvironment;
import com.google.devtools.build.lib.sandbox.SandboxHelpers.SandboxOutputs;
import com.google.devtools.build.lib.shell.Command;
import com.google.devtools.build.lib.shell.CommandException;
import com.google.devtools.build.lib.util.OS;
import com.google.devtools.build.lib.vfs.FileSystem;
import com.google.devtools.build.lib.vfs.Path;
import com.google.devtools.build.lib.vfs.Symlinks;
import java.io.File;
import java.io.IOException;
import java.time.Duration;
import java.util.HashMap;
import java.util.Map;
import java.util.SortedMap;
import javax.annotation.Nullable;
/** Spawn runner that uses linux sandboxing APIs to execute a local subprocess. */
final class LinuxSandboxedSpawnRunner extends AbstractSandboxSpawnRunner {
// Since checking if sandbox is supported is expensive, we remember what we've checked.
private static final Map<Path, Boolean> isSupportedMap = new HashMap<>();
/**
* Returns whether the linux sandbox is supported on the local machine by running a small command
* in it.
*/
public static boolean isSupported(final CommandEnvironment cmdEnv) {
if (OS.getCurrent() != OS.LINUX) {
return false;
}
if (!LinuxSandboxUtil.isSupported(cmdEnv)) {
return false;
}
Path linuxSandbox = LinuxSandboxUtil.getLinuxSandbox(cmdEnv);
return isSupportedMap.computeIfAbsent(
linuxSandbox, linuxSandboxPath -> computeIsSupported(cmdEnv, linuxSandboxPath));
}
private static boolean computeIsSupported(CommandEnvironment cmdEnv, Path linuxSandbox) {
ImmutableList<String> linuxSandboxArgv =
LinuxSandboxUtil.commandLineBuilder(linuxSandbox, ImmutableList.of("/bin/true")).build();
ImmutableMap<String, String> env = ImmutableMap.of();
Path execRoot = cmdEnv.getExecRoot();
File cwd = execRoot.getPathFile();
Command cmd = new Command(linuxSandboxArgv.toArray(new String[0]), env, cwd);
try (SilentCloseable c = Profiler.instance().profile("LinuxSandboxedSpawnRunner.isSupported")) {
cmd.execute(ByteStreams.nullOutputStream(), ByteStreams.nullOutputStream());
} catch (CommandException e) {
return false;
}
return true;
}
private final FileSystem fileSystem;
private final BlazeDirectories blazeDirs;
private final Path execRoot;
private final boolean allowNetwork;
private final Path linuxSandbox;
private final Path sandboxBase;
private final Path inaccessibleHelperFile;
private final Path inaccessibleHelperDir;
private final LocalEnvProvider localEnvProvider;
private final Duration timeoutKillDelay;
private final @Nullable SandboxfsProcess sandboxfsProcess;
private final boolean sandboxfsMapSymlinkTargets;
private final TreeDeleter treeDeleter;
/**
* Creates a sandboxed spawn runner that uses the {@code linux-sandbox} tool.
*
* @param cmdEnv the command environment to use
* @param sandboxBase path to the sandbox base directory
* @param inaccessibleHelperFile path to a file that is (already) inaccessible
* @param inaccessibleHelperDir path to a directory that is (already) inaccessible
* @param timeoutKillDelay an additional grace period before killing timing out commands
* @param sandboxfsProcess instance of the sandboxfs process to use; may be null for none, in
* which case the runner uses a symlinked sandbox
* @param sandboxfsMapSymlinkTargets map the targets of symlinks within the sandbox if true
*/
LinuxSandboxedSpawnRunner(
CommandEnvironment cmdEnv,
Path sandboxBase,
Path inaccessibleHelperFile,
Path inaccessibleHelperDir,
Duration timeoutKillDelay,
@Nullable SandboxfsProcess sandboxfsProcess,
boolean sandboxfsMapSymlinkTargets,
TreeDeleter treeDeleter) {
super(cmdEnv);
this.fileSystem = cmdEnv.getRuntime().getFileSystem();
this.blazeDirs = cmdEnv.getDirectories();
this.execRoot = cmdEnv.getExecRoot();
this.allowNetwork = SandboxHelpers.shouldAllowNetwork(cmdEnv.getOptions());
this.linuxSandbox = LinuxSandboxUtil.getLinuxSandbox(cmdEnv);
this.sandboxBase = sandboxBase;
this.inaccessibleHelperFile = inaccessibleHelperFile;
this.inaccessibleHelperDir = inaccessibleHelperDir;
this.timeoutKillDelay = timeoutKillDelay;
this.sandboxfsProcess = sandboxfsProcess;
this.sandboxfsMapSymlinkTargets = sandboxfsMapSymlinkTargets;
this.localEnvProvider = new PosixLocalEnvProvider(cmdEnv.getClientEnv());
this.treeDeleter = treeDeleter;
}
@Override
protected SandboxedSpawn prepareSpawn(Spawn spawn, SpawnExecutionContext context)
throws IOException, ExecException {
// Each invocation of "exec" gets its own sandbox base.
// Note that the value returned by context.getId() is only unique inside one given SpawnRunner,
// so we have to prefix our name to turn it into a globally unique value.
Path sandboxPath =
sandboxBase.getRelative(getName()).getRelative(Integer.toString(context.getId()));
sandboxPath.getParentDirectory().createDirectory();
sandboxPath.createDirectory();
// b/64689608: The execroot of the sandboxed process must end with the workspace name, just like
// the normal execroot does.
Path sandboxExecRoot = sandboxPath.getRelative("execroot").getRelative(execRoot.getBaseName());
sandboxExecRoot.getParentDirectory().createDirectory();
sandboxExecRoot.createDirectory();
Map<String, String> environment =
localEnvProvider.rewriteLocalEnv(spawn.getEnvironment(), binTools, "/tmp");
ImmutableSet<Path> writableDirs = getWritableDirs(sandboxExecRoot, environment);
SandboxOutputs outputs = SandboxHelpers.getOutputs(spawn);
Duration timeout = context.getTimeout();
LinuxSandboxUtil.CommandLineBuilder commandLineBuilder =
LinuxSandboxUtil.commandLineBuilder(linuxSandbox, spawn.getArguments())
.setWritableFilesAndDirectories(writableDirs)
.setTmpfsDirectories(getTmpfsPaths())
.setBindMounts(getReadOnlyBindMounts(blazeDirs, sandboxExecRoot))
.setUseFakeHostname(getSandboxOptions().sandboxFakeHostname)
.setCreateNetworkNamespace(
!(allowNetwork
|| Spawns.requiresNetwork(
spawn, getSandboxOptions().defaultSandboxAllowNetwork)))
.setUseDebugMode(getSandboxOptions().sandboxDebug)
.setKillDelay(timeoutKillDelay);
if (!timeout.isZero()) {
commandLineBuilder.setTimeout(timeout);
}
if (spawn.getExecutionInfo().containsKey(ExecutionRequirements.REQUIRES_FAKEROOT)) {
commandLineBuilder.setUseFakeRoot(true);
} else if (getSandboxOptions().sandboxFakeUsername) {
commandLineBuilder.setUseFakeUsername(true);
}
Path statisticsPath = null;
if (getSandboxOptions().collectLocalSandboxExecutionStatistics) {
statisticsPath = sandboxPath.getRelative("stats.out");
commandLineBuilder.setStatisticsPath(statisticsPath);
}
if (sandboxfsProcess != null) {
return new SandboxfsSandboxedSpawn(
sandboxfsProcess,
sandboxPath,
commandLineBuilder.build(),
environment,
SandboxHelpers.processInputFiles(
spawn,
context,
execRoot,
getSandboxOptions().symlinkedSandboxExpandsTreeArtifactsInRunfilesTree),
outputs,
ImmutableSet.of(),
sandboxfsMapSymlinkTargets,
treeDeleter,
statisticsPath);
} else {
return new SymlinkedSandboxedSpawn(
sandboxPath,
sandboxExecRoot,
commandLineBuilder.build(),
environment,
SandboxHelpers.processInputFiles(
spawn,
context,
execRoot,
getSandboxOptions().symlinkedSandboxExpandsTreeArtifactsInRunfilesTree),
outputs,
writableDirs,
treeDeleter,
statisticsPath);
}
}
@Override
public String getName() {
return "linux-sandbox";
}
@Override
protected ImmutableSet<Path> getWritableDirs(Path sandboxExecRoot, Map<String, String> env)
throws IOException {
ImmutableSet.Builder<Path> writableDirs = ImmutableSet.builder();
writableDirs.addAll(super.getWritableDirs(sandboxExecRoot, env));
FileSystem fs = sandboxExecRoot.getFileSystem();
writableDirs.add(fs.getPath("/dev/shm").resolveSymbolicLinks());
writableDirs.add(fs.getPath("/tmp"));
return writableDirs.build();
}
private ImmutableSet<Path> getTmpfsPaths() {
ImmutableSet.Builder<Path> tmpfsPaths = ImmutableSet.builder();
for (String tmpfsPath : getSandboxOptions().sandboxTmpfsPath) {
tmpfsPaths.add(fileSystem.getPath(tmpfsPath));
}
return tmpfsPaths.build();
}
private SortedMap<Path, Path> getReadOnlyBindMounts(
BlazeDirectories blazeDirs, Path sandboxExecRoot) throws UserExecException {
Path tmpPath = fileSystem.getPath("/tmp");
final SortedMap<Path, Path> bindMounts = Maps.newTreeMap();
if (blazeDirs.getWorkspace().startsWith(tmpPath)) {
bindMounts.put(blazeDirs.getWorkspace(), blazeDirs.getWorkspace());
}
if (blazeDirs.getOutputBase().startsWith(tmpPath)) {
bindMounts.put(blazeDirs.getOutputBase(), blazeDirs.getOutputBase());
}
for (ImmutableMap.Entry<String, String> additionalMountPath :
getSandboxOptions().sandboxAdditionalMounts) {
try {
final Path mountTarget = fileSystem.getPath(additionalMountPath.getValue());
// If source path is relative, treat it as a relative path inside the execution root
final Path mountSource = sandboxExecRoot.getRelative(additionalMountPath.getKey());
// If a target has more than one source path, the latter one will take effect.
bindMounts.put(mountTarget, mountSource);
} catch (IllegalArgumentException e) {
throw new UserExecException(
String.format("Error occurred when analyzing bind mount pairs. %s", e.getMessage()));
}
}
for (Path inaccessiblePath : getInaccessiblePaths()) {
if (inaccessiblePath.isDirectory(Symlinks.NOFOLLOW)) {
bindMounts.put(inaccessiblePath, inaccessibleHelperDir);
} else {
bindMounts.put(inaccessiblePath, inaccessibleHelperFile);
}
}
validateBindMounts(bindMounts);
return bindMounts;
}
/**
* This method does the following things: - If mount source does not exist on the host system,
* throw an error message - If mount target exists, check whether the source and target are of the
* same type - If mount target does not exist on the host system, throw an error message
*
* @param bindMounts the bind mounts map with target as key and source as value
* @throws UserExecException
*/
private void validateBindMounts(SortedMap<Path, Path> bindMounts) throws UserExecException {
for (SortedMap.Entry<Path, Path> bindMount : bindMounts.entrySet()) {
final Path source = bindMount.getValue();
final Path target = bindMount.getKey();
// Mount source should exist in the file system
if (!source.exists()) {
throw new UserExecException(String.format("Mount source '%s' does not exist.", source));
}
// If target exists, but is not of the same type as the source, then we cannot mount it.
if (target.exists()) {
boolean areBothDirectories = source.isDirectory() && target.isDirectory();
boolean isSourceFile = source.isFile() || source.isSymbolicLink();
boolean isTargetFile = target.isFile() || target.isSymbolicLink();
boolean areBothFiles = isSourceFile && isTargetFile;
if (!(areBothDirectories || areBothFiles)) {
// Source and target are not of the same type; we cannot mount it.
throw new UserExecException(
String.format(
"Mount target '%s' is not of the same type as mount source '%s'.",
target, source));
}
} else {
// Mount target should exist in the file system
throw new UserExecException(
String.format(
"Mount target '%s' does not exist. Bazel only supports bind mounting on top of "
+ "existing files/directories. Please create an empty file or directory at "
+ "the mount target path according to the type of mount source.",
target));
}
}
}
@Override
public void cleanupSandboxBase(Path sandboxBase, TreeDeleter treeDeleter) throws IOException {
// Delete the inaccessible files synchronously, bypassing the treeDeleter. They are only a
// couple of files that can be deleted fast, and ensuring they are gone at the end of every
// build avoids annoying permission denied errors if the user happens to run "rm -rf" on the
// output base. (We have some tests that do that.)
if (inaccessibleHelperDir.exists()) {
inaccessibleHelperDir.chmod(0700);
inaccessibleHelperDir.deleteTree();
}
if (inaccessibleHelperFile.exists()) {
inaccessibleHelperFile.chmod(0600);
inaccessibleHelperFile.delete();
}
super.cleanupSandboxBase(sandboxBase, treeDeleter);
}
}