Anthropic-Cybersecurity-Skills/skills/detecting-serverless-function-injection/references/api-reference.md

API Reference: Serverless Function Injection Detection Agent

Overview

Detects code injection vulnerabilities in AWS Lambda functions by scanning function code for dangerous sinks (eval, exec, os.system, child_process.exec), auditing Lambda layers for external account dependencies, identifying IAM privilege escalation paths through overprivileged execution roles, and monitoring CloudTrail for suspicious function modifications. For authorized security assessments only.

Dependencies

Package	Version	Purpose
boto3	>=1.26	AWS API access for Lambda, IAM, CloudTrail

CLI Usage

# Full assessment with code scanning
python agent.py --region us-east-1 --scan-code --cloudtrail-days 14 --output report.json

# Scan specific functions only
python agent.py --functions payment-processor auth-handler --scan-code --output report.json

# Quick assessment without code download (IAM, layers, CloudTrail only)
python agent.py --region us-west-2 --output quick_report.json

Arguments

Argument	Required	Description
--region	No	AWS region to assess (default: us-east-1)
--functions	No	Specific function names to scan (default: all functions in region)
--scan-code	No	Download and scan function deployment packages for injection sinks
--cloudtrail-days	No	Number of days of CloudTrail history to search (default: 7)
--output	No	Output file path (default: serverless_injection_report.json)

Key Functions

enumerate_functions(lambda_client)

Lists all Lambda functions with runtime, handler, execution role, layers, environment variable names, and function URL configuration. Flags functions with secrets in environment variables.

get_event_source_mappings(lambda_client)

Enumerates all event source mappings (SQS, DynamoDB Streams, Kinesis, Kafka, MQ) to identify injection entry points where untrusted data enters function handlers.

download_and_scan_function(lambda_client, function_name, runtime_family, work_dir)

Downloads the function deployment package, extracts it, and scans source files for injection sinks using regex patterns. Checks whether event data accessors (event[, event.get() appear in the context around each sink to assess data flow confidence.

audit_layers(lambda_client, functions)

Identifies Lambda layers from external AWS accounts and high-impact layers shared across 5+ functions. External layers can intercept function execution or override runtime dependencies.

detect_privilege_escalation_paths(iam_client, functions)

Audits execution roles for dangerous permissions (iam:PassRole, lambda:UpdateFunctionCode, sts:AssumeRole) and administrative policies. Any function with UpdateFunctionCode + PassRole is a privilege escalation vector.

check_cloudtrail_for_modifications(cloudtrail_client, days_back)

Searches CloudTrail for UpdateFunctionCode, UpdateFunctionConfiguration, PublishLayerVersion, and CreateFunction events. Flags modifications outside CloudFormation/console, role changes, layer additions, and off-hours activity.

check_function_url_security(lambda_client, functions)

Identifies Lambda function URLs with AuthType=NONE that are publicly accessible without authentication.

Injection Pattern Coverage

Python Sinks

Pattern	CWE	Severity
eval()	CWE-95	Critical
exec()	CWE-95	Critical
os.system()	CWE-78	Critical
os.popen()	CWE-78	Critical
subprocess.*(shell=True)	CWE-78	Critical
pickle.loads()	CWE-502	High
yaml.load() without SafeLoader	CWE-502	High
jinja2.Template() with event data	CWE-1336	High
SQL via f-string with event data	CWE-89	Critical

Node.js Sinks

Pattern	CWE	Severity
eval()	CWE-95	Critical
new Function()	CWE-95	Critical
child_process.exec()	CWE-78	Critical
child_process.execSync()	CWE-78	Critical
vm.runInNewContext()	CWE-95	Critical
vm.runInThisContext()	CWE-95	Critical
Template literal command injection	CWE-78	Critical

Output Schema

{
  "report_type": "Serverless Function Injection Assessment",
  "generated_at": "ISO-8601 timestamp",
  "summary": {
    "functions_analyzed": 0,
    "event_source_mappings": 0,
    "total_findings": 0,
    "critical_findings": 0,
    "high_findings": 0,
    "injection_sinks_found": 0,
    "layer_issues": 0,
    "escalation_paths": 0,
    "suspicious_modifications": 0
  },
  "findings": [
    {
      "category": "code_injection|layer_security|privilege_escalation|suspicious_modification|function_url",
      "function_name": "",
      "severity": "critical|high|medium",
      "description": ""
    }
  ],
  "functions": [],
  "event_source_mappings": [],
  "cloudtrail_events": []
}

Exit Codes

Code	Meaning
0	No critical findings
1	Critical injection sinks or privilege escalation paths detected