# Server-Side Request Forgery (SSRF) (CWE-918)

The web server receives a URL or similar request from an upstream component and retrieves the contents of this URL, but it does not sufficiently ensure that the request is being sent to the expected destination.

**Stack:** Go

- Prevalence: Średnia Pokryto 3 języków
- Impact: Wysoki 4 reguł o wysokim poziomie
- Prevention: Udokumentowane 4 przykładów poprawek

**OWASP:** Server-Side Request Forgery (A10:2021-Server-Side Request Forgery) - #10

## Description

By providing URLs to unexpected hosts or ports, attackers can make it appear that the server is sending the request, possibly bypassing access controls such as firewalls.

## Prevention

Strategie zapobiegania dla Server-Side Request Forgery oparte na 1 regułach detekcji Shoulder.

### Go

Parse URL and validate host against domain allowlist

## Warning Signs

- [HIGH] user input flowing to HTTP client requests, enabling Server-Side Request Forgery attacks

## Consequences

- Odczyt danych aplikacji
- Obejście mechanizmu ochrony
- Wykonanie nieautoryzowanych poleceń

## Mitigations

- Stosuj listę dozwolonych celów
- Wyłącz zbędne schematy URL (file://, gopher://)
- Stosuj segmentację na poziomie sieci

## Detection

- Total rules: 4
- Languages: go, javascript, typescript, python

## Rules by Language

### Go (1 rules)

- **Server-Side Request Forgery (SSRF)** [HIGH]: Detects user input flowing to HTTP client requests, enabling Server-Side Request Forgery attacks.
  - Remediation: Validate URLs against an allowlist of permitted domains.

```go
allowed := map[string]bool{"api.example.com": true}
parsed, _ := url.Parse(targetURL)
if !allowed[parsed.Host] {
    return errors.New("domain not allowed")
}
```

Learn more: https://shoulder.dev/learn/go/cwe-918/ssrf