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// Copyright 2018 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.annotations.VisibleForTesting;
import com.google.common.collect.ImmutableList;
import com.google.common.collect.ImmutableMap;
import com.google.common.flogger.GoogleLogger;
import com.google.devtools.build.lib.shell.Subprocess;
import com.google.devtools.build.lib.shell.SubprocessBuilder;
import com.google.devtools.build.lib.util.OS;
import com.google.devtools.build.lib.versioning.GnuVersionParser;
import com.google.devtools.build.lib.versioning.ParseException;
import com.google.devtools.build.lib.versioning.SemVer;
import com.google.devtools.build.lib.vfs.Path;
import com.google.devtools.build.lib.vfs.PathFragment;
import java.io.IOException;
import javax.annotation.Nullable;
/**
* A sandboxfs implementation that uses an external sandboxfs binary to manage the mount point.
*
* <p>This class implements common code to generalize the interactions with sandboxfs, but delegates
* to its subclassess once the version of sandboxfs in use has been determined. The subclasses
* implement logic specific to each version to provide compatibility with the different versions of
* sandboxfs that the user might have installed.
*/
abstract class RealSandboxfsProcess implements SandboxfsProcess {
private static final GoogleLogger logger = GoogleLogger.forEnclosingClass();
/**
* Contains the {@code --allow} flag to pass to sandboxfs.
*
* <p>On macOS, we need to allow users other than self to access the sandboxfs instance. This is
* necessary because macOS's amfid, which runs as root, has to have access to the binaries within
* the sandbox in order to validate signatures. See:
* http://jmmv.dev/2017/10/fighting-execs-sandboxfs-macos.html
*/
@VisibleForTesting
static final String ALLOW_FLAG = OS.getCurrent() == OS.DARWIN ? "--allow=other" : "--allow=self";
/** Directory on which the sandboxfs is serving. */
private final Path mountPoint;
/**
* Process handle to the sandboxfs instance. Null only after {@link #destroy()} has been invoked.
*/
@Nullable private Subprocess process;
/**
* Shutdown hook to stop the sandboxfs instance on abrupt termination. Null only after {@link
* #destroy()} has been invoked.
*/
@Nullable private Thread shutdownHook;
/**
* Initializes a new sandboxfs process instance.
*
* @param process process handle for the already-running sandboxfs instance
*/
RealSandboxfsProcess(Path mountPoint, Subprocess process) {
this.mountPoint = mountPoint;
this.process = process;
this.shutdownHook =
new Thread(
() -> {
try {
this.destroy();
} catch (Exception e) {
logger.atWarning().withCause(e).log(
"Failed to destroy running sandboxfs instance; mount point may have "
+ "been left behind");
}
});
Runtime.getRuntime().addShutdownHook(shutdownHook);
}
/**
* Mounts a new sandboxfs instance.
*
* <p>The root of the file system instance is left unmapped which means that it remains as
* read-only throughout the lifetime of this instance. Writable subdirectories can later be mapped
* via {@link #createSandbox}.
*
* @param binary path to the sandboxfs binary. This is a {@link PathFragment} and not a {@link
* Path} because we want to support "bare" (non-absolute) names for the location of the
* sandboxfs binary; such names are automatically looked for in the {@code PATH}.
* @param mountPoint directory on which to mount the sandboxfs instance
* @param logFile path to the file that will receive all sandboxfs logging output
* @return a new handle that represents the running process
* @throws IOException if there is a problem starting the process
*/
static SandboxfsProcess mount(PathFragment binary, Path mountPoint, Path logFile)
throws IOException {
logger.atInfo().log("Mounting sandboxfs (%s) onto %s", binary, mountPoint);
GnuVersionParser<SemVer> parser = new GnuVersionParser<>("sandboxfs", SemVer::parse);
SemVer version;
try {
version = parser.fromProgram(binary);
} catch (IOException | ParseException e) {
throw new IOException("Failed to get sandboxfs version from " + binary, e);
}
ImmutableList.Builder<String> argvBuilder = ImmutableList.builder();
argvBuilder.add(binary.getPathString());
argvBuilder.add(ALLOW_FLAG);
// TODO(jmmv): Pass flags to enable sandboxfs' debugging support (--listen_address and --debug)
// when requested by the user via --sandbox_debug. Tricky because we have to figure out how to
// deal with port numbers (which sandboxfs can autoassign, but doesn't currently promise a way
// to tell us back what it picked).
argvBuilder.add(mountPoint.getPathString());
SubprocessBuilder processBuilder = new SubprocessBuilder();
processBuilder.setArgv(argvBuilder.build());
processBuilder.setStderr(logFile.getPathFile());
processBuilder.setEnv(ImmutableMap.of(
// sandboxfs may need to locate fusermount depending on the FUSE implementation so pass the
// PATH to the subprocess (which we assume is sufficient).
"PATH", System.getenv("PATH")));
Subprocess process = processBuilder.start();
RealSandboxfsProcess sandboxfs;
if (version.compareTo(SemVer.from(0, 2)) >= 0) {
sandboxfs = new RealSandboxfs02Process(mountPoint, process);
} else {
sandboxfs = new RealSandboxfs01Process(mountPoint, process);
}
try {
// Create an empty sandbox to ensure sandboxfs is successfully serving.
sandboxfs.createSandbox("empty", (mapper) -> {});
} catch (IOException e) {
process.destroyAndWait();
throw new IOException("sandboxfs failed to start", e);
}
return sandboxfs;
}
@Override
public Path getMountPoint() {
return mountPoint;
}
@Override
public boolean isAlive() {
return process != null && !process.finished();
}
@Override
public synchronized void destroy() {
if (shutdownHook != null) {
Runtime.getRuntime().removeShutdownHook(shutdownHook);
shutdownHook = null;
}
if (process != null) {
try {
process.getOutputStream().close();
} catch (IOException e) {
logger.atWarning().withCause(e).log("Failed to close sandboxfs's stdin pipe");
}
try {
process.getInputStream().close();
} catch (IOException e) {
logger.atWarning().withCause(e).log("Failed to close sandboxfs's stdout pipe");
}
process.destroyAndWait();
process = null;
}
}
}