everything-claude-code/rules/java/security.md

paths

paths
**/*.java

Java Security

This file extends common/security.md with Java-specific content.

Secrets Management

• Never hardcode API keys, tokens, or credentials in source code
• Use environment variables: System.getenv("API_KEY")
• Use a secret manager (Vault, AWS Secrets Manager) for production secrets
• Keep local config files with secrets in .gitignore

// BAD
private static final String API_KEY = "sk-abc123...";

// GOOD — environment variable
String apiKey = System.getenv("PAYMENT_API_KEY");
Objects.requireNonNull(apiKey, "PAYMENT_API_KEY must be set");

SQL Injection Prevention

• Always use parameterized queries — never concatenate user input into SQL
• Use PreparedStatement or your framework's parameterized query API
• Validate and sanitize any input used in native queries

// BAD — SQL injection via string concatenation
Statement stmt = conn.createStatement();
String sql = "SELECT * FROM orders WHERE name = '" + name + "'";
stmt.executeQuery(sql);

// GOOD — PreparedStatement with parameterized query
PreparedStatement ps = conn.prepareStatement("SELECT * FROM orders WHERE name = ?");
ps.setString(1, name);

// GOOD — JDBC template
jdbcTemplate.query("SELECT * FROM orders WHERE name = ?", mapper, name);

Input Validation

• Validate all user input at system boundaries before processing
• Use Bean Validation (@NotNull, @NotBlank, @Size) on DTOs when using a validation framework
• Sanitize file paths and user-provided strings before use
• Reject input that fails validation with clear error messages

// Validate manually in plain Java
public Order createOrder(String customerName, BigDecimal amount) {
    if (customerName == null || customerName.isBlank()) {
        throw new IllegalArgumentException("Customer name is required");
    }
    if (amount == null || amount.compareTo(BigDecimal.ZERO) <= 0) {
        throw new IllegalArgumentException("Amount must be positive");
    }
    return new Order(customerName, amount);
}

Authentication and Authorization

• Never implement custom auth crypto — use established libraries
• Store passwords with bcrypt or Argon2, never MD5/SHA1
• Enforce authorization checks at service boundaries
• Clear sensitive data from logs — never log passwords, tokens, or PII

Dependency Security

• Run mvn dependency:tree or ./gradlew dependencies to audit transitive dependencies
• Use OWASP Dependency-Check or Snyk to scan for known CVEs
• Keep dependencies updated — set up Dependabot or Renovate

Error Messages

• Never expose stack traces, internal paths, or SQL errors in API responses
• Map exceptions to safe, generic client messages at handler boundaries
• Log detailed errors server-side; return generic messages to clients

// Log the detail, return a generic message
try {
    return orderService.findById(id);
} catch (OrderNotFoundException ex) {
    log.warn("Order not found: id={}", id);
    return ApiResponse.error("Resource not found");  // generic, no internals
} catch (Exception ex) {
    log.error("Unexpected error processing order id={}", id, ex);
    return ApiResponse.error("Internal server error");  // never expose ex.getMessage()
}

References

See skill: springboot-security for Spring Security authentication and authorization patterns. See skill: security-review for general security checklists.