Middleware enhancements

pkg/middleware/sanitize.go

@@ -0,0 +1,251 @@
+package middleware
+
+import (
+	"html"
+	"net/http"
+	"regexp"
+	"strings"
+)
+
+// Sanitizer provides input sanitization beyond SQL injection protection
+type Sanitizer struct {
+	// StripHTML removes HTML tags from input
+	StripHTML bool
+
+	// EscapeHTML escapes HTML entities
+	EscapeHTML bool
+
+	// RemoveNullBytes removes null bytes from input
+	RemoveNullBytes bool
+
+	// RemoveControlChars removes control characters (except newline, carriage return, tab)
+	RemoveControlChars bool
+
+	// MaxStringLength limits individual string field length (0 = no limit)
+	MaxStringLength int
+
+	// BlockPatterns are regex patterns to block (e.g., script tags, SQL keywords)
+	BlockPatterns []*regexp.Regexp
+
+	// Custom sanitization function
+	CustomSanitizer func(string) string
+}
+
+// DefaultSanitizer returns a sanitizer with secure defaults
+func DefaultSanitizer() *Sanitizer {
+	return &Sanitizer{
+		StripHTML:          false, // Don't strip by default (breaks legitimate HTML content)
+		EscapeHTML:         true,  // Escape HTML entities to prevent XSS
+		RemoveNullBytes:    true,  // Remove null bytes (security best practice)
+		RemoveControlChars: true,  // Remove dangerous control characters
+		MaxStringLength:    0,     // No limit by default
+
+		// Block common XSS and injection patterns
+		BlockPatterns: []*regexp.Regexp{
+			regexp.MustCompile(`(?i)<script[^>]*>.*?</script>`), // Script tags
+			regexp.MustCompile(`(?i)javascript:`),               // JavaScript protocol
+			regexp.MustCompile(`(?i)on\w+\s*=`),                 // Event handlers (onclick, onerror, etc.)
+			regexp.MustCompile(`(?i)<iframe[^>]*>`),             // Iframes
+			regexp.MustCompile(`(?i)<object[^>]*>`),             // Objects
+			regexp.MustCompile(`(?i)<embed[^>]*>`),              // Embeds
+		},
+	}
+}
+
+// StrictSanitizer returns a sanitizer with very strict rules
+func StrictSanitizer() *Sanitizer {
+	s := DefaultSanitizer()
+	s.StripHTML = true
+	s.MaxStringLength = 10000
+	return s
+}
+
+// Sanitize sanitizes a string value
+func (s *Sanitizer) Sanitize(value string) string {
+	if value == "" {
+		return value
+	}
+
+	// Remove null bytes
+	if s.RemoveNullBytes {
+		value = strings.ReplaceAll(value, "\x00", "")
+	}
+
+	// Remove control characters
+	if s.RemoveControlChars {
+		value = removeControlCharacters(value)
+	}
+
+	// Check block patterns
+	for _, pattern := range s.BlockPatterns {
+		if pattern.MatchString(value) {
+			// Replace matched pattern with empty string
+			value = pattern.ReplaceAllString(value, "")
+		}
+	}
+
+	// Strip HTML tags
+	if s.StripHTML {
+		value = stripHTMLTags(value)
+	}
+
+	// Escape HTML entities
+	if s.EscapeHTML && !s.StripHTML {
+		value = html.EscapeString(value)
+	}
+
+	// Apply max length
+	if s.MaxStringLength > 0 && len(value) > s.MaxStringLength {
+		value = value[:s.MaxStringLength]
+	}
+
+	// Apply custom sanitizer
+	if s.CustomSanitizer != nil {
+		value = s.CustomSanitizer(value)
+	}
+
+	return value
+}
+
+// SanitizeMap sanitizes all string values in a map
+func (s *Sanitizer) SanitizeMap(data map[string]interface{}) map[string]interface{} {
+	result := make(map[string]interface{})
+	for key, value := range data {
+		result[key] = s.sanitizeValue(value)
+	}
+	return result
+}
+
+// sanitizeValue recursively sanitizes values
+func (s *Sanitizer) sanitizeValue(value interface{}) interface{} {
+	switch v := value.(type) {
+	case string:
+		return s.Sanitize(v)
+	case map[string]interface{}:
+		return s.SanitizeMap(v)
+	case []interface{}:
+		result := make([]interface{}, len(v))
+		for i, item := range v {
+			result[i] = s.sanitizeValue(item)
+		}
+		return result
+	default:
+		return value
+	}
+}
+
+// Middleware returns an HTTP middleware that sanitizes request headers and query params
+// Note: Body sanitization should be done at the application level after parsing
+func (s *Sanitizer) Middleware(next http.Handler) http.Handler {
+	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		// Sanitize query parameters
+		if r.URL.RawQuery != "" {
+			q := r.URL.Query()
+			sanitized := false
+			for key, values := range q {
+				for i, value := range values {
+					sanitizedValue := s.Sanitize(value)
+					if sanitizedValue != value {
+						values[i] = sanitizedValue
+						sanitized = true
+					}
+				}
+				if sanitized {
+					q[key] = values
+				}
+			}
+			if sanitized {
+				r.URL.RawQuery = q.Encode()
+			}
+		}
+
+		// Sanitize specific headers (User-Agent, Referer, etc.)
+		dangerousHeaders := []string{
+			"User-Agent",
+			"Referer",
+			"X-Forwarded-For",
+			"X-Real-IP",
+		}
+
+		for _, header := range dangerousHeaders {
+			if value := r.Header.Get(header); value != "" {
+				sanitized := s.Sanitize(value)
+				if sanitized != value {
+					r.Header.Set(header, sanitized)
+				}
+			}
+		}
+
+		next.ServeHTTP(w, r)
+	})
+}
+
+// Helper functions
+
+// removeControlCharacters removes control characters except \n, \r, \t
+func removeControlCharacters(s string) string {
+	var result strings.Builder
+	for _, r := range s {
+		// Keep newline, carriage return, tab, and non-control characters
+		if r == '\n' || r == '\r' || r == '\t' || r >= 32 {
+			result.WriteRune(r)
+		}
+	}
+	return result.String()
+}
+
+// stripHTMLTags removes HTML tags from a string
+func stripHTMLTags(s string) string {
+	// Simple regex to remove HTML tags
+	re := regexp.MustCompile(`<[^>]*>`)
+	return re.ReplaceAllString(s, "")
+}
+
+// Common sanitization patterns
+
+// SanitizeFilename sanitizes a filename
+func SanitizeFilename(filename string) string {
+	// Remove path traversal attempts
+	filename = strings.ReplaceAll(filename, "..", "")
+	filename = strings.ReplaceAll(filename, "/", "")
+	filename = strings.ReplaceAll(filename, "\\", "")
+
+	// Remove null bytes
+	filename = strings.ReplaceAll(filename, "\x00", "")
+
+	// Limit length
+	if len(filename) > 255 {
+		filename = filename[:255]
+	}
+
+	return filename
+}
+
+// SanitizeEmail performs basic email sanitization
+func SanitizeEmail(email string) string {
+	email = strings.TrimSpace(strings.ToLower(email))
+
+	// Remove dangerous characters
+	email = strings.ReplaceAll(email, "\x00", "")
+	email = removeControlCharacters(email)
+
+	return email
+}
+
+// SanitizeURL performs basic URL sanitization
+func SanitizeURL(url string) string {
+	url = strings.TrimSpace(url)
+
+	// Remove null bytes
+	url = strings.ReplaceAll(url, "\x00", "")
+
+	// Block javascript: and data: protocols
+	if strings.HasPrefix(strings.ToLower(url), "javascript:") {
+		return ""
+	}
+	if strings.HasPrefix(strings.ToLower(url), "data:") {
+		return ""
+	}
+
+	return url
+}