# Improper Input Validation (CWE-20)

The product receives input or data, but it does not validate or incorrectly validates that the input has the properties that are required to process the data safely and correctly.

**Stack:** Go

- Prevalence: उच्च बार-बार शोषित
- Impact: उच्च 6 उच्च गंभीरता वाले नियम
- Prevention: प्रलेखित 13 फिक्स उदाहरण

**OWASP:** Broken Access Control (A01:2021-Broken Access Control) - #1

## Description

Input validation is a frequently-used technique for checking potentially dangerous inputs in order to ensure that the inputs are safe for processing within the code, or when communicating with other components. When software does not validate input properly, an attacker is able to craft the input in a form that is not expected by the rest of the application.

## Prevention

4 Shoulder डिटेक्शन नियमों पर आधारित Improper Input Validation के लिए रोकथाम रणनीतियाँ।

### Go

Parse string inputs to typed values and validate against business rules before use

Use Echo struct binding with validation tags instead of untyped maps

Use Fiber BodyParser with typed structs and validation tags

## Warning Signs

- [MEDIUM] Business-critical value used without proper validation
- [MEDIUM] Gin application missing input validation middleware

## Consequences

- अनधिकृत कोड निष्पादित करना
- एप्लिकेशन डेटा संशोधित करना
- DoS
- एप्लिकेशन डेटा पढ़ना

## Mitigations

- मानें कि सभी इनपुट दुर्भावनापूर्ण हैं। केवल ज्ञात-अच्छे इनपुट स्वीकार करने वाली रणनीति का उपयोग करें
- इनपुट सत्यापन करते समय, सभी संभावित प्रासंगिक गुणों पर विचार करें
- केवल दुर्भावनापूर्ण या विकृत इनपुट खोजने पर निर्भर न रहें

## Detection

- Total rules: 13
- Languages: python, go, javascript, typescript

## Rules by Language

### Go (4 rules)

- **Business Logic Input Validation** [MEDIUM]: Business-critical values (discount, quantity, refund) used without validation.
  - Remediation: Parse and validate business-critical values before use.

```go
discount, err := strconv.ParseFloat(r.FormValue("discount"), 64)
if err != nil || discount < 0 || discount > 100 {
    http.Error(w, "Invalid discount", 400)
    return
}
```

Learn more: https://shoulder.dev/learn/go/cwe-20/input-validation
- **Echo Missing Input Validation** [MEDIUM]: Echo endpoints accepting user input without struct validation.
  - Remediation: Use struct binding with validation tags.

```go
type Input struct {
    Name string `json:"name" validate:"required"`
}

func handler(c echo.Context) error {
    var input Input
    if err := c.Bind(&input); err != nil {
        return c.JSON(400, map[string]string{"error": err.Error()})
    }
    if err := c.Validate(&input); err != nil {
        return c.JSON(400, map[string]string{"error": err.Error()})
    }
    return nil
}
```

Learn more: https://shoulder.dev/learn/go/cwe-20/input-validation
- **Fiber Missing Input Validation** [MEDIUM]: Fiber endpoints accepting user input without struct validation.
  - Remediation: Use BodyParser with struct validation tags.

```go
type Input struct {
    Name string `json:"name" validate:"required"`
}

func handler(c *fiber.Ctx) error {
    var input Input
    if err := c.BodyParser(&input); err != nil {
        return c.Status(400).JSON(fiber.Map{"error": err.Error()})
    }
    if err := validate.Struct(&input); err != nil {
        return c.Status(400).JSON(fiber.Map{"error": err.Error()})
    }
    return nil
}
```

Learn more: https://shoulder.dev/learn/go/cwe-20/input-validation
- **Gin Missing Input Validation** [MEDIUM]: Gin endpoints accepting user input without struct binding validation.
  - Remediation: Use ShouldBindJSON with struct binding tags for validation.

```go
type Input struct {
    Name  string `json:"name" binding:"required,min=2"`
    Email string `json:"email" binding:"required,email"`
}

func handler(c *gin.Context) {
    var input Input
    if err := c.ShouldBindJSON(&input); err != nil {
        c.JSON(400, gin.H{"error": err.Error()})
        return
    }
}
```

Learn more: https://shoulder.dev/learn/go/cwe-20/input-validation