从代码层面分析Jenkins未授权访问CVE-2017-1000353

wget https://repo.huaweicloud.com/jenkins/redhat-stable/jenkins-2.190.3-1.1.noarch.rpm

rpm -ivh jenkins-2.190.3-1.1.noarch.rpm

# 启动jenkins服务
systemctl start jenkins

# 查看jenkins状态
systemctl status jenkins

创建双向channel->启动Reader Thread->读取command对象->反序列化漏洞执行cmd

@Extension @Symbol("cli")
@Restricted(NoExternalUse.class)
public class CLIAction implements UnprotectedRootAction, StaplerProxy {

    private transient final Map<UUID,FullDuplexHttpChannel> duplexChannels = new HashMap<UUID, FullDuplexHttpChannel>();

     ......

    @Override
    public Object getTarget() {
        StaplerRequest req = Stapler.getCurrentRequest();
        if (req.getRestOfPath().length()==0 && "POST".equals(req.getMethod())) {
            // CLI connection request
            throw new CliEndpointResponse();
        } else {
            return this;
        }
    }

    private class CliEndpointResponse extends HttpResponseException {
        @Override
        public void generateResponse(StaplerRequest req, StaplerResponse rsp, Object node) throws IOException, ServletException {
            try {
                // do not require any permission to establish a CLI connection
                // the actual authentication for the connecting Channel is done by CLICommand

                UUID uuid = UUID.fromString(req.getHeader("Session"));
                rsp.setHeader("Hudson-Duplex",""); // set the header so that the client would know

                FullDuplexHttpChannel server;
                if(req.getHeader("Side").equals("download")) {
                    duplexChannels.put(uuid,server=new FullDuplexHttpChannel(uuid, !Jenkins.getActiveInstance().hasPermission(Jenkins.ADMINISTER)) {
                        @Override
                        protected void main(Channel channel) throws IOException, InterruptedException {
                            // capture the identity given by the transport, since this can be useful for SecurityRealm.createCliAuthenticator()
                            channel.setProperty(CLICommand.TRANSPORT_AUTHENTICATION, Jenkins.getAuthentication());
                            channel.setProperty(CliEntryPoint.class.getName(),new CliManagerImpl(channel));
                        }
                    });
                    try {
                        server.download(req,rsp);
                    } finally {
                        duplexChannels.remove(uuid);
                    }
                } else {
                    duplexChannels.get(uuid).upload(req,rsp);
                }
            } catch (InterruptedException e) {
                throw new IOException(e);
            }
        }
    }

public synchronized void download(StaplerRequest req, StaplerResponse rsp) throws InterruptedException, IOException {
            ......

        {// wait until we have the other channel
            long end = System.currentTimeMillis() + CONNECTION_TIMEOUT;
            while (upload == null && System.currentTimeMillis()<end)
                wait(1000);

            if (upload==null)
                throw new IOException("HTTP full-duplex channel timeout: "+uuid);
        }

        try {
            channel = new Channel("HTTP full-duplex channel " + uuid,
                    Computer.threadPoolForRemoting, Mode.BINARY, upload, out, null, restricted);
             ......
        } finally {
            // publish that we are done
            completed=true;
            notify();
        }
    }

  public synchronized void upload(StaplerRequest req, StaplerResponse rsp) throws InterruptedException, IOException {
        rsp.setStatus(HttpServletResponse.SC_OK);
        InputStream in = req.getInputStream();
        if(DIY_CHUNKING)    in = new ChunkedInputStream(in);

        // publish the upload channel
        upload = in;
        notify();

        // wait until we are done
        while (!completed)
            wait();
    }

protected CommandTransport negotiate(final InputStream is, final OutputStream os) throws IOException {
          ......
        {// read the input until we hit preamble
            Mode[] modes={Mode.BINARY,Mode.TEXT};
            byte[][] preambles = new byte[][]{Mode.BINARY.preamble, Mode.TEXT.preamble, Capability.PREAMBLE};
            int[] ptr=new int[3];
            Capability cap = new Capability(0); // remote capacity that we obtained. If we don't hear from remote, assume no capability

            while(true) {
                int ch = is.read();
                ......
                for(int i=0;i<preambles.length;i++) {
                    byte[] preamble = preambles[i];
                    if(preamble[ptr[i]]==ch) {
                        if(++ptr[i]==preamble.length) {
                            switch (i) {
                            case 0:
                            case 1:
                                ......
                                return makeTransport(is, os, mode, cap);
                            case 2:
                                cap = Capability.read(is);

protected CommandTransport makeTransport(InputStream is, OutputStream os, Mode mode, Capability cap) throws IOException {
    FlightRecorderInputStream fis = new FlightRecorderInputStream(is);

    if (cap.supportsChunking())
        return new ChunkedCommandTransport(cap, mode.wrap(fis), mode.wrap(os), os);
    else {
        ObjectOutputStream oos = new ObjectOutputStream(mode.wrap(os));
        oos.flush();    // make sure that stream preamble is sent to the other end. avoids dead-lock

        return new ClassicCommandTransport(
                new ObjectInputStreamEx(mode.wrap(fis),getBaseLoader(),getClassFilter()),
                oos,fis,os,cap);
    }
}

ClassicCommandTransport -> SynchronousCommandTransport -> CommandTransport

public void setup(Channel channel, CommandReceiver receiver) {
        this.channel = channel;
        new ReaderThread(receiver).start();
    }

//通过上面的ReaderThread.start()方法启动一个线程，ReaderThread为SynchronousCommandTransport类的内部类，在run()方法中，调用ClassicCommandTransport类的read()方法读取输入，read()方法实际是调用Command类的readFrom()方法读取，通过反序列化输入返回一个Command对象。

private final class ReaderThread extends Thread {
        ......
        public ReaderThread(CommandReceiver receiver) {
            super("Channel reader thread: "+channel.getName());
            this.receiver = receiver;
        }

        @Override
        public void run() {
            final String name =channel.getName();
            try {
                while(!channel.isInClosed()) {
                    Command cmd = null;
                    try {
                        cmd = read();
  public final Command read() throws IOException, ClassNotFoundException {
        try {
            Command cmd = Command.readFrom(channel, ois);