# Missing Authentication for Critical Function (CWE-306)

The product does not perform any authentication for functionality that requires a provable user identity or consumes a significant amount of resources.

- Prevalence: High Frequently exploited
- Impact: High 6 high-severity rules
- Prevention: Documented 6 fix examples

**OWASP:** Identification and Authentication Failures (A07:2021-Identification and Authentication Failures) - #7

## Description

As data traverses trust boundaries, the data should be validated before being processed. When authentication is not applied to critical functions, attackers can invoke these functions without proving their identity.

## Prevention

### Python

Add @login_required or @permission_required decorator to all protected views

Add authentication using FastAPI Depends() dependency injection

### Go

Add Echo JWT middleware to protect API endpoints

Add Fiber JWT middleware to protect API endpoints

Add JWT authentication middleware to protect API endpoints

### Node.js

Add @UseGuards decorator with authentication guard at controller or method level

## Warning Signs

- [HIGH] View handles sensitive operations without authentication decorator
- [HIGH] Django views that should require authentication but lack
@login_required, @permission_required, or o
- [HIGH] Endpoint performs sensitive operations without Depends(get_current_user) or similar auth
- [HIGH] FastAPI endpoints that perform sensitive operations without
authentication via Depends() dependency 
- [HIGH] Gin application missing JWT authentication middleware
- [HIGH] NestJS endpoint has no @UseGuards() decorator for authentication

## Consequences

- Gain Privileges
- Read Application Data
- Modify Application Data
- Execute Unauthorized Code

## Mitigations

- Divide the software into components with different trust levels
- Identify all areas with security-critical functionality and require authentication for all such areas
- Ensure that appropriate access controls are enforced

## Detection

- Total rules: 6
- Languages: python, go, typescript

## Rules by Language

### Go (3 rules)

- **Echo Missing JWT Middleware** [HIGH]: API endpoints lack JWT authentication middleware protection.
  - Remediation: Add JWT middleware to protect API routes.

```go
import "github.com/labstack/echo-jwt/v4"

api := e.Group("/api")
api.Use(echojwt.JWT([]byte(os.Getenv("JWT_SECRET"))))
api.POST("/transfer", transferHandler)
```

Learn more: https://shoulder.dev/learn/go/cwe-306/jwt-middleware
- **Fiber Missing JWT Middleware** [HIGH]: API endpoints lack JWT authentication middleware protection.
  - Remediation: Add JWT middleware to protect API routes.

```go
import "github.com/gofiber/contrib/jwt"

api := app.Group("/api")
api.Use(jwtware.New(jwtware.Config{
    SigningKey: jwtware.SigningKey{Key: []byte(os.Getenv("JWT_SECRET"))},
}))
api.Post("/transfer", transferHandler)
```

Learn more: https://shoulder.dev/learn/go/cwe-306/jwt-middleware
- **Gin Missing JWT Middleware** [HIGH]: API endpoints lack JWT authentication middleware protection.
  - Remediation: Add JWT middleware to protect API routes.

```go
import jwt "github.com/appleboy/gin-jwt/v2"

auth, _ := jwt.New(&jwt.GinJWTMiddleware{
    Realm: "api",
    Key:   []byte(os.Getenv("JWT_SECRET")),
})
api := r.Group("/api")
api.Use(auth.MiddlewareFunc())
api.POST("/transfer", transferHandler)
```

Learn more: https://shoulder.dev/learn/go/cwe-306/jwt-middleware

### Python (2 rules)

- **Django View Missing Authentication** [HIGH]: Detects Django views that should require authentication but lack
@login_required, @permission_required, or other authentication decorators.
  - Remediation: Add authentication:

```python
from django.contrib.auth.decorators import login_required, permission_required

@login_required
def protected_view(request):
    # Only authenticated users can access
    pass

@permission_required('app.change_model')
def admin_view(request):
    # Only users with permission can access
    pass
```
- **FastAPI Endpoint Missing Authentication** [HIGH]: Detects FastAPI endpoints that perform sensitive operations without
authentication via Depends() dependency injection.
  - Remediation: Add authentication via dependency injection:

```python
from fastapi import Depends, FastAPI
from fastapi.security import OAuth2PasswordBearer

oauth2_scheme = OAuth2PasswordBearer(tokenUrl="token")

async def get_current_user(token: str = Depends(oauth2_scheme)):
    # Verify token and return user
    return user

@app.delete("/users/{user_id}")
async def delete_user(
    user_id: int,
    current_user: User = Depends(get_current_user)  # Required auth
):
    # Only authenticated users can delete
    pass
```

### Typescript (1 rules)

- **NestJS Endpoint Missing Authentication Guard** [HIGH]: Endpoints without @UseGuards or @Public decorators are accessible to
unauthenticated users, enabling unauthorized access.
  - Remediation: Add @UseGuards decorator at controller or method level.

```typescript
import { UseGuards } from '@nestjs/common';
import { JwtAuthGuard } from '../auth/jwt-auth.guard';

@Controller('users')
@UseGuards(JwtAuthGuard)
export class UsersController {
  @Get(':id')
  findOne(@Param('id') id: string) {
    return this.usersService.findOne(id);
  }
}
```

Learn more: https://shoulder.dev/learn/typescript/cwe-306/missing-auth-guard