com.google.common.io.TempFileCreator Maven / Gradle / Ivy
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/*
* Copyright (C) 2007 The Guava Authors
*
* 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.common.io;
import static com.google.common.base.StandardSystemProperty.JAVA_IO_TMPDIR;
import static com.google.common.base.StandardSystemProperty.USER_NAME;
import static com.google.common.base.Throwables.throwIfUnchecked;
import static java.nio.file.attribute.AclEntryFlag.DIRECTORY_INHERIT;
import static java.nio.file.attribute.AclEntryFlag.FILE_INHERIT;
import static java.nio.file.attribute.AclEntryType.ALLOW;
import static java.nio.file.attribute.PosixFilePermissions.asFileAttribute;
import static java.util.Objects.requireNonNull;
import com.google.common.annotations.GwtIncompatible;
import com.google.common.annotations.J2ktIncompatible;
import com.google.common.annotations.VisibleForTesting;
import com.google.common.collect.ImmutableList;
import com.google.j2objc.annotations.J2ObjCIncompatible;
import java.io.File;
import java.io.IOException;
import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;
import java.nio.file.FileSystems;
import java.nio.file.Paths;
import java.nio.file.attribute.AclEntry;
import java.nio.file.attribute.AclEntryPermission;
import java.nio.file.attribute.FileAttribute;
import java.nio.file.attribute.PosixFilePermissions;
import java.nio.file.attribute.UserPrincipal;
import java.util.EnumSet;
import java.util.Set;
/**
* Creates temporary files and directories whose permissions are restricted to the current user or,
* in the case of Android, the current app. If that is not possible (as is the case under the very
* old Android Ice Cream Sandwich release), then this class throws an exception instead of creating
* a file or directory that would be more accessible.
*/
@J2ktIncompatible
@GwtIncompatible
@J2ObjCIncompatible
@ElementTypesAreNonnullByDefault
abstract class TempFileCreator {
static final TempFileCreator INSTANCE = pickSecureCreator();
/**
* @throws IllegalStateException if the directory could not be created (to implement the contract
* of {@link Files#createTempDir()}, such as if the system does not support creating temporary
* directories securely
*/
abstract File createTempDir();
abstract File createTempFile(String prefix) throws IOException;
private static TempFileCreator pickSecureCreator() {
try {
Class.forName("java.nio.file.Path");
return new JavaNioCreator();
} catch (ClassNotFoundException runningUnderAndroid) {
// Try another way.
}
try {
int version = (int) Class.forName("android.os.Build$VERSION").getField("SDK_INT").get(null);
int jellyBean =
(int) Class.forName("android.os.Build$VERSION_CODES").getField("JELLY_BEAN").get(null);
/*
* I assume that this check can't fail because JELLY_BEAN will be present only if we're
* running under Jelly Bean or higher. But it seems safest to check.
*/
if (version < jellyBean) {
return new ThrowingCreator();
}
// Don't merge these catch() blocks, let alone use ReflectiveOperationException directly:
// b/65343391
} catch (NoSuchFieldException e) {
// The JELLY_BEAN field doesn't exist because we're running on a version before Jelly Bean :)
return new ThrowingCreator();
} catch (ClassNotFoundException e) {
// Should be impossible, but we want to return *something* so that class init succeeds.
return new ThrowingCreator();
} catch (IllegalAccessException e) {
// ditto
return new ThrowingCreator();
}
// Android isolates apps' temporary directories since Jelly Bean:
// https://github.com/google/guava/issues/4011#issuecomment-770020802
// So we can create files there with any permissions and still get security from the isolation.
return new JavaIoCreator();
}
/**
* Creates the permissions normally used for Windows filesystems, looking up the user afresh, even
* if previous calls have initialized the {@code PermissionSupplier} fields.
*
* This lets us test the effects of different values of the {@code user.name} system property
* without needing a separate VM or classloader.
*/
@IgnoreJRERequirement // used only when Path is available (and only from tests)
@VisibleForTesting
static void testMakingUserPermissionsFromScratch() throws IOException {
// All we're testing is whether it throws.
FileAttribute unused = JavaNioCreator.userPermissions().get();
}
@IgnoreJRERequirement // used only when Path is available
private static final class JavaNioCreator extends TempFileCreator {
@Override
File createTempDir() {
try {
return java.nio.file.Files.createTempDirectory(
Paths.get(JAVA_IO_TMPDIR.value()), /* prefix= */ null, directoryPermissions.get())
.toFile();
} catch (IOException e) {
throw new IllegalStateException("Failed to create directory", e);
}
}
@Override
File createTempFile(String prefix) throws IOException {
return java.nio.file.Files.createTempFile(
Paths.get(JAVA_IO_TMPDIR.value()),
/* prefix= */ prefix,
/* suffix= */ null,
filePermissions.get())
.toFile();
}
@IgnoreJRERequirement // see enclosing class (whose annotation Animal Sniffer ignores here...)
private interface PermissionSupplier {
FileAttribute get() throws IOException;
}
private static final PermissionSupplier filePermissions;
private static final PermissionSupplier directoryPermissions;
static {
Set views = FileSystems.getDefault().supportedFileAttributeViews();
if (views.contains("posix")) {
filePermissions = () -> asFileAttribute(PosixFilePermissions.fromString("rw-------"));
directoryPermissions = () -> asFileAttribute(PosixFilePermissions.fromString("rwx------"));
} else if (views.contains("acl")) {
filePermissions = directoryPermissions = userPermissions();
} else {
filePermissions =
directoryPermissions =
() -> {
throw new IOException("unrecognized FileSystem type " + FileSystems.getDefault());
};
}
}
private static PermissionSupplier userPermissions() {
try {
UserPrincipal user =
FileSystems.getDefault()
.getUserPrincipalLookupService()
.lookupPrincipalByName(getUsername());
ImmutableList acl =
ImmutableList.of(
AclEntry.newBuilder()
.setType(ALLOW)
.setPrincipal(user)
.setPermissions(EnumSet.allOf(AclEntryPermission.class))
.setFlags(DIRECTORY_INHERIT, FILE_INHERIT)
.build());
FileAttribute> attribute =
new FileAttribute>() {
@Override
public String name() {
return "acl:acl";
}
@Override
public ImmutableList value() {
return acl;
}
};
return () -> attribute;
} catch (IOException e) {
// We throw a new exception each time so that the stack trace is right.
return () -> {
throw new IOException("Could not find user", e);
};
}
}
private static String getUsername() {
/*
* https://github.com/google/guava/issues/6634: ProcessHandle has more accurate information,
* but that class isn't available under all environments that we support. We use it if
* available and fall back if not.
*/
String fromSystemProperty = requireNonNull(USER_NAME.value());
try {
Class processHandleClass = Class.forName("java.lang.ProcessHandle");
Class processHandleInfoClass = Class.forName("java.lang.ProcessHandle$Info");
Class optionalClass = Class.forName("java.util.Optional");
/*
* We don't *need* to use reflection to access Optional: It's available on all JDKs we
* support, and Android code won't get this far, anyway, because ProcessHandle is
* unavailable. But given how much other reflection we're using, we might as well use it
* here, too, so that we don't need to also suppress an AndroidApiChecker error.
*/
Method currentMethod = processHandleClass.getMethod("current");
Method infoMethod = processHandleClass.getMethod("info");
Method userMethod = processHandleInfoClass.getMethod("user");
Method orElseMethod = optionalClass.getMethod("orElse", Object.class);
Object current = currentMethod.invoke(null);
Object info = infoMethod.invoke(current);
Object user = userMethod.invoke(info);
return (String) requireNonNull(orElseMethod.invoke(user, fromSystemProperty));
} catch (ClassNotFoundException runningUnderAndroidOrJava8) {
/*
* I'm not sure that we could actually get here for *Android*: I would expect us to enter
* the POSIX code path instead. And if we tried this code path, we'd have trouble unless we
* were running under a new enough version of Android to support NIO.
*
* So this is probably just the "Windows Java 8" case. In that case, if we wanted *another*
* layer of fallback before consulting the system property, we could try
* com.sun.security.auth.module.NTSystem.
*
* But for now, we use the value from the system property as our best guess.
*/
return fromSystemProperty;
} catch (InvocationTargetException e) {
throwIfUnchecked(e.getCause()); // in case it's an Error or something
return fromSystemProperty; // should be impossible
} catch (NoSuchMethodException shouldBeImpossible) {
return fromSystemProperty;
} catch (IllegalAccessException shouldBeImpossible) {
/*
* We don't merge these into `catch (ReflectiveOperationException ...)` or an equivalent
* multicatch because ReflectiveOperationException isn't available under Android:
* b/124188803
*/
return fromSystemProperty;
}
}
}
private static final class JavaIoCreator extends TempFileCreator {
@Override
File createTempDir() {
File baseDir = new File(JAVA_IO_TMPDIR.value());
@SuppressWarnings("GoodTime") // reading system time without TimeSource
String baseName = System.currentTimeMillis() + "-";
for (int counter = 0; counter < TEMP_DIR_ATTEMPTS; counter++) {
File tempDir = new File(baseDir, baseName + counter);
if (tempDir.mkdir()) {
return tempDir;
}
}
throw new IllegalStateException(
"Failed to create directory within "
+ TEMP_DIR_ATTEMPTS
+ " attempts (tried "
+ baseName
+ "0 to "
+ baseName
+ (TEMP_DIR_ATTEMPTS - 1)
+ ')');
}
@Override
File createTempFile(String prefix) throws IOException {
return File.createTempFile(
/* prefix= */ prefix,
/* suffix= */ null,
/* directory= */ null /* defaults to java.io.tmpdir */);
}
/** Maximum loop count when creating temp directories. */
private static final int TEMP_DIR_ATTEMPTS = 10000;
}
private static final class ThrowingCreator extends TempFileCreator {
private static final String MESSAGE =
"Guava cannot securely create temporary files or directories under SDK versions before"
+ " Jelly Bean. You can create one yourself, either in the insecure default directory"
+ " or in a more secure directory, such as context.getCacheDir(). For more information,"
+ " see the Javadoc for Files.createTempDir().";
@Override
File createTempDir() {
throw new IllegalStateException(MESSAGE);
}
@Override
File createTempFile(String prefix) throws IOException {
throw new IOException(MESSAGE);
}
}
private TempFileCreator() {}
}