CWE-502 可信数据的反序列化

admin 2021年12月16日16:45:44CWE(弱点枚举)评论221 views7223字阅读24分4秒阅读模式

CWE-502 可信数据的反序列化

Deserialization of Untrusted Data

结构: Simple

Abstraction: Base

状态: Draft

被利用可能性: Medium

基本描述

The application deserializes untrusted data without sufficiently verifying that the resulting data will be valid.

扩展描述

It is often convenient to serialize objects for communication or to save them for later use. However, deserialized data or code can often be modified without using the provided accessor functions if it does not use cryptography to protect itself. Furthermore, any cryptography would still be client-side security -- which is a dangerous security assumption.

Data that is untrusted can not be trusted to be well-formed.

When developers place no restrictions on "gadget chains," or series of instances and method invocations that can self-execute during the deserialization process (i.e., before the object is returned to the caller), it is sometimes possible for attackers to leverage them to perform unauthorized actions, like generating a shell.

相关缺陷

  • cwe_Nature: ChildOf cwe_CWE_ID: 913 cwe_View_ID: 1000 cwe_Ordinal: Primary

  • cwe_Nature: ChildOf cwe_CWE_ID: 913 cwe_View_ID: 1003 cwe_Ordinal: Primary

  • cwe_Nature: ChildOf cwe_CWE_ID: 913 cwe_View_ID: 699 cwe_Ordinal: Primary

  • cwe_Nature: PeerOf cwe_CWE_ID: 915 cwe_View_ID: 1000

适用平台

Language: [{'cwe_Name': 'Java', 'cwe_Prevalence': 'Undetermined'}, {'cwe_Name': 'Ruby', 'cwe_Prevalence': 'Undetermined'}, {'cwe_Name': 'PHP', 'cwe_Prevalence': 'Undetermined'}, {'cwe_Name': 'Python', 'cwe_Prevalence': 'Undetermined'}, {'cwe_Name': 'JavaScript', 'cwe_Prevalence': 'Undetermined'}]

常见的影响

范围 影响 注释
Integrity ['Modify Application Data', 'Unexpected State'] Attackers can modify unexpected objects or data that was assumed to be safe from modification.
Availability DoS: Resource Consumption (CPU) If a function is making an assumption on when to terminate, based on a sentry in a string, it could easily never terminate.
Other Varies by Context The consequences can vary widely, because it depends on which objects or methods are being deserialized, and how they are used. Making an assumption that the code in the deserialized object is valid is dangerous and can enable exploitation.

可能的缓解方案

['Architecture and Design', 'Implementation']

策略:

If available, use the signing/sealing features of the programming language to assure that deserialized data has not been tainted. For example, a hash-based message authentication code (HMAC) could be used to ensure that data has not been modified.

Implementation

策略:

When deserializing data, populate a new object rather than just deserializing. The result is that the data flows through safe input validation and that the functions are safe.

Implementation

策略:

Explicitly define a final object() to prevent deserialization.

['Architecture and Design', 'Implementation']

策略:

Make fields transient to protect them from deserialization.
An attempt to serialize and then deserialize a class containing transient fields will result in NULLs where the transient data should be. This is an excellent way to prevent time, environment-based, or sensitive variables from being carried over and used improperly.

Implementation

策略:

Avoid having unnecessary types or gadgets available that can be leveraged for malicious ends. This limits the potential for unintended or unauthorized types and gadgets to be leveraged by the attacker. Whitelist acceptable classes. Note: new gadgets are constantly being discovered, so this alone is not a sufficient mitigation.

示例代码

This code snippet deserializes an object from a file and uses it as a UI button:

bad Java

try {

File file = new File("object.obj");
ObjectInputStream in = new ObjectInputStream(new FileInputStream(file));
javax.swing.JButton button = (javax.swing.JButton) in.readObject();
in.close();

}

This code does not attempt to verify the source or contents of the file before deserializing it. An attacker may be able to replace the intended file with a file that contains arbitrary malicious code which will be executed when the button is pressed.

To mitigate this, explicitly define final readObject() to prevent deserialization. An example of this is:

good Java

private final void readObject(ObjectInputStream in) throws java.io.IOException {
throw new java.io.IOException("Cannot be deserialized"); }

In Python, the Pickle library handles the serialization and deserialization processes. In this example derived from [R.502.7], the code receives and parses data, and afterwards tries to authenticate a user based on validating a token.

bad Python

try {

class ExampleProtocol(protocol.Protocol):
def dataReceived(self, data):

# Code that would be here would parse the incoming data
# After receiving headers, call confirmAuth() to authenticate

def confirmAuth(self, headers):
try:
token = cPickle.loads(base64.b64decode(headers['AuthToken']))
if not check_hmac(token['signature'], token['data'], getSecretKey()):
raise AuthFail
self.secure_data = token['data']
except:
raise AuthFail

}

Unfortunately, the code does not verify that the incoming data is legitimate. An attacker can construct a illegitimate, serialized object "AuthToken" that instantiates one of Python's subprocesses to execute arbitrary commands. For instance,the attacker could construct a pickle that leverages Python's subprocess module, which spawns new processes and includes a number of arguments for various uses. Since Pickle allows objects to define the process for how they should be unpickled, the attacker can direct the unpickle process to call Popen in the subprocess module and execute /bin/sh.

分析过的案例

标识 说明 链接
CVE-2015-8103 Deserialization issue in commonly-used Java library allows remote execution. https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2015-8103
CVE-2015-4852 Deserialization issue in commonly-used Java library allows remote execution. https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2015-4852
CVE-2013-1465 Use of PHP unserialize function on untrusted input allows attacker to modify application configuration. https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2013-1465
CVE-2012-3527 Use of PHP unserialize function on untrusted input in content management system might allow code execution. https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2012-3527
CVE-2012-0911 Use of PHP unserialize function on untrusted input in content management system allows code execution using a crafted cookie value. https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2012-0911
CVE-2012-0911 Content management system written in PHP allows unserialize of arbitrary objects, possibly allowing code execution. https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2012-0911
CVE-2011-2520 Python script allows local users to execute code via pickled data. https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2011-2520
CVE-2012-4406 Unsafe deserialization using pickle in a Python script. https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2012-4406
CVE-2003-0791 Web browser allows execution of native methods via a crafted string to a JavaScript function that deserializes the string. https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2003-0791

Notes

分类映射

映射的分类名 ImNode ID Fit Mapped Node Name
CLASP Deserialization of untrusted data
The CERT Oracle Secure Coding Standard for Java (2011) SER01-J Do not deviate from the proper signatures of serialization methods
The CERT Oracle Secure Coding Standard for Java (2011) SER03-J Do not serialize unencrypted, sensitive data
The CERT Oracle Secure Coding Standard for Java (2011) SER06-J Make defensive copies of private mutable components during deserialization
The CERT Oracle Secure Coding Standard for Java (2011) SER08-J Do not use the default serialized form for implementation defined invariants
Software Fault Patterns SFP25 Tainted input to variable

相关攻击模式

  • CAPEC-586

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  • 本文由 发表于 2021年12月16日16:45:44
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