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// Copyright (C) 2010 The Android Open Source Project
//
// 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.gerrit.sshd;
import static java.nio.charset.StandardCharsets.UTF_8;
import com.google.common.base.Throwables;
import com.google.common.util.concurrent.Atomics;
import com.google.gerrit.extensions.restapi.AuthException;
import com.google.gerrit.reviewdb.client.Account;
import com.google.gerrit.server.CurrentUser;
import com.google.gerrit.server.IdentifiedUser;
import com.google.gerrit.server.PeerDaemonUser;
import com.google.gerrit.server.config.AuthConfig;
import com.google.gerrit.server.permissions.GlobalPermission;
import com.google.gerrit.server.permissions.PermissionBackend;
import com.google.gerrit.server.permissions.PermissionBackendException;
import com.google.gerrit.sshd.SshScope.Context;
import com.google.inject.Inject;
import java.io.IOException;
import java.net.SocketAddress;
import java.util.ArrayList;
import java.util.List;
import java.util.concurrent.atomic.AtomicReference;
import org.apache.sshd.server.Environment;
import org.apache.sshd.server.command.Command;
import org.kohsuke.args4j.Argument;
import org.kohsuke.args4j.Option;
/**
* Executes any other command as a different user identity.
*
* <p>The calling user must be authenticated as a {@link PeerDaemonUser}, which usually requires
* public key authentication using this daemon's private host key, or a key on this daemon's peer
* host key ring.
*/
public final class SuExec extends BaseCommand {
private final SshScope sshScope;
private final DispatchCommandProvider dispatcher;
private final PermissionBackend permissionBackend;
private boolean enableRunAs;
private CurrentUser caller;
private SshSession session;
private IdentifiedUser.GenericFactory userFactory;
private SshScope.Context callingContext;
@Option(name = "--as", required = true)
private Account.Id accountId;
@Option(name = "--from")
private SocketAddress peerAddress;
@Argument(index = 0, multiValued = true, metaVar = "COMMAND")
private List<String> args = new ArrayList<>();
private final AtomicReference<Command> atomicCmd;
@Inject
SuExec(
final SshScope sshScope,
@CommandName(Commands.ROOT) final DispatchCommandProvider dispatcher,
PermissionBackend permissionBackend,
final CurrentUser caller,
final SshSession session,
final IdentifiedUser.GenericFactory userFactory,
final SshScope.Context callingContext,
AuthConfig config) {
this.sshScope = sshScope;
this.dispatcher = dispatcher;
this.permissionBackend = permissionBackend;
this.caller = caller;
this.session = session;
this.userFactory = userFactory;
this.callingContext = callingContext;
this.enableRunAs = config.isRunAsEnabled();
atomicCmd = Atomics.newReference();
}
@Override
public void start(Environment env) throws IOException {
try {
checkCanRunAs();
parseCommandLine();
final Context ctx = callingContext.subContext(newSession(), join(args));
final Context old = sshScope.set(ctx);
try {
final BaseCommand cmd = dispatcher.get();
cmd.setArguments(args.toArray(new String[args.size()]));
provideStateTo(cmd);
atomicCmd.set(cmd);
cmd.start(env);
} finally {
sshScope.set(old);
}
} catch (UnloggedFailure e) {
String msg = e.getMessage();
if (!msg.endsWith("\n")) {
msg += "\n";
}
err.write(msg.getBytes(UTF_8));
err.flush();
onExit(1);
}
}
private void checkCanRunAs() throws UnloggedFailure {
if (caller instanceof PeerDaemonUser) {
// OK.
} else if (!enableRunAs) {
throw die("suexec disabled by auth.enableRunAs = false");
} else {
try {
permissionBackend.user(caller).check(GlobalPermission.RUN_AS);
} catch (AuthException e) {
throw die("suexec not permitted");
} catch (PermissionBackendException e) {
throw die("suexec not available: " + e);
}
}
}
private SshSession newSession() {
final SocketAddress peer;
if (peerAddress == null) {
peer = session.getRemoteAddress();
} else {
peer = peerAddress;
}
if (caller instanceof PeerDaemonUser) {
caller = null;
}
return new SshSession(session, peer, userFactory.runAs(peer, accountId, caller));
}
private static String join(List<String> args) {
StringBuilder r = new StringBuilder();
for (String a : args) {
if (r.length() > 0) {
r.append(" ");
}
r.append(a);
}
return r.toString();
}
@Override
public void destroy() {
Command cmd = atomicCmd.getAndSet(null);
if (cmd != null) {
try {
cmd.destroy();
} catch (Exception e) {
Throwables.throwIfUnchecked(e);
throw new RuntimeException(e);
}
}
}
}
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