Introduce Scanner Interface for Extensible Scanning Capabilities

[knqyf263]

Background

Currently, Trivy has four built-in scanners:

• Vulnerability Scanner
• Misconfiguration Scanner
• Secret Scanner
• License Scanner

This issue proposes introducing a unified Scanner interface that all scanners must implement to make the scanner system more extensible and maintainable.

Proposal

Scanner Interface

type Scanner interface {
    // PreScan performs initialization tasks before scanning
    // e.g., downloading vulnerability databases or scan assets
    PreScan(flag.Options) error
    
    // Scan performs the actual scanning process
    Scan(context.Context, types.ScanTarget, types.ScanOptions)
    
    // PostScan handles cleanup or final processing after scanning
    PostScan(flag.Options) error

    // WriteTable writes scan results in table format
    WriteTable(bytes.Buffer, types.Result) error
    
    // WriteSARIF writes scan results in SARIF format
    WriteSARIF(types.Result) (sarif.Data, error)
}

Scanner Registration System

Scanners will be managed through a registration system, similar to the existing analyzer system:

var scanners []Scanner

func RegisterScanner(s Scanner) {
    scanners = append(scanners, s)
}

func Scanners() []Scanner {
    return scanners
}

Benefits

1. Extensibility: Third-party developers (mainly targeting Aqua) can easily add custom scanners by implementing the Scanner interface
2. Standardization: All scanners follow the same lifecycle (PreScan → Scan → PostScan)
3. Unified Output: Custom scanners can output results in both table and SARIF formats

Example Usage

The CLI flag --scanners vuln,misconfig will internally translate to:

RegisterScanner(vulnerability.Scanner)
RegisterScanner(misconfig.Scanner)

Output Implementation

Table writer implementation example:

func (tw *Writer) Write(_ context.Context, report types.Report) error {
    if slices.Contains(tw.options.TableModes, types.Detailed) {
        for _, scanner := range scan.Scanners() {
            for _, result := range report.Results {
                scanner.WriteTable(tw.w, result)
            }
        }
    }
    tw.flush()
    return nil
}