Agent skill
security-principles
Use this skill when handling secrets, credentials, PII, input validation, or any security-sensitive code. Covers secrets management, secure defaults, encryption, logging safety, and common vulnerability prevention. Apply when adding authentication, configuring environment variables, reviewing code for security issues, or working with sensitive data.
Install this agent skill to your Project
npx add-skill https://github.com/exceptionless/Exceptionless/tree/main/.agents/skills/security-principles
SKILL.md
Security Principles
Secrets Management
Secrets are injected via Kubernetes ConfigMaps and environment variables — never commit secrets to the repository.
- Configuration files — Use
appsettings.ymlfor non-secret config - Environment variables — Secrets injected at runtime via
EX_*prefix - Kubernetes — ConfigMaps mount configuration, Secrets mount credentials
// AppOptions binds to configuration (including env vars)
public class AppOptions
{
public string? StripeApiKey { get; set; }
public AuthOptions Auth { get; set; } = new();
}
Validate All Inputs
- Check bounds and formats before processing
- Use
ArgumentNullException.ThrowIfNull()and similar guards - Validate early, fail fast
Sanitize External Data
- Never trust data from queues, caches, user input, or external sources
- Validate against expected schema
- Sanitize HTML/script content before storage or display
No Sensitive Data in Logs
- Never log passwords, tokens, API keys, or PII
- Log identifiers and prefixes, not full values
- Use structured logging with safe placeholders
Use Secure Defaults
- Default to encrypted connections (SSL/TLS enabled)
- Default to restrictive permissions
- Require explicit opt-out for security features
Avoid Deprecated Cryptographic Algorithms
Use modern cryptographic algorithms:
- ❌
MD5,SHA1— Cryptographically broken - ✅
SHA256,SHA512— Current standards
Avoid Insecure Serialization
- ❌
BinaryFormatter— Insecure deserialization vulnerability - ✅
System.Text.Json,Newtonsoft.Json— Safe serialization
Input Bounds Checking
- Enforce minimum/maximum values on pagination parameters
- Limit batch sizes to prevent resource exhaustion
- Validate string lengths before storage
OWASP Reference
Review OWASP Top 10 regularly:
- Broken Access Control
- Cryptographic Failures
- Injection
- Insecure Design
- Security Misconfiguration
- Vulnerable and Outdated Components
- Identification and Authentication Failures
- Software and Data Integrity Failures
- Security Logging and Monitoring Failures
- Server-Side Request Forgery
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