Implementing Input Sanitization and Output Masking for Genesys Cloud Data Actions Using Go Middleware

What You Will Build

• A production-grade Go HTTP server that conforms to the Genesys Cloud Data Action contract and processes inbound workflow requests.
• A middleware chain that intercepts inbound request bodies to sanitize user-supplied data and intercepts outbound response bodies to mask sensitive fields before external service integration.
• Implementation uses Go 1.21 standard library packages, explicit error handling, and retry logic for external HTTP calls.

Prerequisites

• Genesys Cloud organization with Data Action capability enabled and a registered Data Action URL
• Go 1.21 or higher installed locally
• No external dependencies required. The implementation relies exclusively on net/http, encoding/json, io, bytes, regexp, sync, and time.
• Understanding of the Genesys Cloud Data Action HTTP contract: POST requests to /execute with a JSON body containing an input object. Responses must return an output object or an errors array.

Authentication Setup

Genesys Cloud Data Actions are authenticated using a shared secret header (X-Genesys-Action-Secret) or IP allowlisting. The middleware layer validates this header before processing the request body. If the Data Action must call back into Genesys Cloud APIs (for example, to update a contact or log an event), it requires OAuth 2.0 Client Credentials. The following example demonstrates token acquisition and caching with automatic refresh logic.

package auth

import (
	"bytes"
	"encoding/json"
	"fmt"
	"io"
	"net/http"
	"sync"
	"time"
)

type OAuthToken struct {
	AccessToken string `json:"access_token"`
	ExpiresIn   int    `json:"expires_in"`
	IssuedAt    time.Time
}

type TokenManager struct {
	mu         sync.RWMutex
	token      *OAuthToken
	clientID   string
	clientSecret string
	endpoint   string
}

func NewTokenManager(clientID, clientSecret, orgRegion string) *TokenManager {
	return &TokenManager{
		clientID:     clientID,
		clientSecret: clientSecret,
		endpoint:     fmt.Sprintf("https://%s.login.genesyscloud.com/oauth/token", orgRegion),
	}
}

func (tm *TokenManager) GetToken() (string, error) {
	tm.mu.RLock()
	if tm.token != nil && time.Since(tm.token.IssuedAt) < time.Duration(tm.token.ExpiresIn-30)*time.Second {
		accessToken := tm.token.AccessToken
		tm.mu.RUnlock()
		return accessToken, nil
	}
	tm.mu.RUnlock()

	tm.mu.Lock()
	defer tm.mu.Unlock()

	// Double-check after acquiring write lock
	if tm.token != nil && time.Since(tm.token.IssuedAt) < time.Duration(tm.token.ExpiresIn-30)*time.Second {
		return tm.token.AccessToken, nil
	}

	payload := fmt.Sprintf("grant_type=client_credentials&client_id=%s&client_secret=%s", tm.clientID, tm.clientSecret)
	resp, err := http.Post(tm.endpoint, "application/x-www-form-urlencoded", bytes.NewBufferString(payload))
	if err != nil {
		return "", fmt.Errorf("oauth token request failed: %w", err)
	}
	defer resp.Body.Close()

	if resp.StatusCode != http.StatusOK {
		body, _ := io.ReadAll(resp.Body)
		return "", fmt.Errorf("oauth token error %d: %s", resp.StatusCode, string(body))
	}

	var tokenResp OAuthToken
	if err := json.NewDecoder(resp.Body).Decode(&tokenResp); err != nil {
		return "", fmt.Errorf("oauth token decode failed: %w", err)
	}

	tokenResp.IssuedAt = time.Now()
	tm.token = &tokenResp
	return tokenResp.AccessToken, nil
}

Required OAuth Scope: routing:users or analytics:read depending on the callback operation. The token manager caches the credential and refreshes it thirty seconds before expiration to prevent 401 interruptions during high-throughput Data Action execution.

Implementation

Step 1: Define the Data Action Contract and Response Writer Wrapper

The Genesys Cloud Data Action protocol expects a specific JSON structure. The middleware must read the request body without consuming it prematurely, modify it, and restore it for the downstream handler. The same principle applies to the response writer. Wrapping http.ResponseWriter allows the middleware to capture the serialized output, apply masking rules, and write the modified payload back to the client.

package main

import (
	"bytes"
	"encoding/json"
	"io"
	"net/http"
)

// DataActionRequest matches the Genesys Cloud inbound contract
type DataActionRequest struct {
	Input map[string]interface{} `json:"input"`
}

// DataActionResponse matches the Genesys Cloud outbound contract
type DataActionResponse struct {
	Output map[string]interface{} `json:"output,omitempty"`
	Errors []string               `json:"errors,omitempty"`
}

// responseCapture wraps http.ResponseWriter to intercept the response body
type responseCapture struct {
	http.ResponseWriter
	body *bytes.Buffer
}

func (rc *responseCapture) Write(b []byte) (int, error) {
	rc.body.Write(b)
	return rc.ResponseWriter.Write(b)
}

The responseCapture struct satisfies the http.ResponseWriter interface. When the downstream handler writes JSON, the buffer captures it. The middleware later unmarshals the buffer, applies transformations, and writes the result to the actual response writer.

Step 2: Implement Input Sanitization Middleware

Input sanitization prevents injection attacks, enforces length limits, and strips unsafe characters before the payload reaches business logic. The middleware reads the request body, validates JSON structure, applies recursive sanitization rules, and reconstructs the request body for the next handler.

package main

import (
	"bytes"
	"encoding/json"
	"io"
	"log"
	"net/http"
	"regexp"
	"strings"
)

var (
	htmlTagRegex   = regexp.MustCompile(`<[^>]*>`)
	sqlInjectionRx = regexp.MustCompile(`(?i)(\b(SELECT|INSERT|UPDATE|DELETE|DROP|UNION|OR|AND)\b)`)
	xssCharRx      = regexp.MustCompile(`[<>"'&]`)
)

func SanitizeInputMiddleware(next http.HandlerFunc) http.HandlerFunc {
	return func(w http.ResponseWriter, r *http.Request) {
		// Verify Genesys Data Action secret
		secret := r.Header.Get("X-Genesys-Action-Secret")
		if secret != "YOUR_SECURE_ACTION_SECRET" {
			writeJSONError(w, http.StatusUnauthorized, []string{"Invalid or missing action secret"})
			return
		}

		bodyBytes, err := io.ReadAll(r.Body)
		if err != nil {
			writeJSONError(w, http.StatusBadRequest, []string{"Failed to read request body"})
			return
		}
		r.Body = io.NopCloser(bytes.NewBuffer(bodyBytes))

		var req DataActionRequest
		if err := json.Unmarshal(bodyBytes, &req); err != nil {
			writeJSONError(w, http.StatusBadRequest, []string{"Invalid JSON payload"})
			return
		}

		if req.Input == nil {
			req.Input = make(map[string]interface{})
		}

		req.Input = sanitizeValue(req.Input).(map[string]interface{})

		sanitizedJSON, err := json.Marshal(req)
		if err != nil {
			writeJSONError(w, http.StatusInternalServerError, []string{"Failed to marshal sanitized request"})
			return
		}

		r.Body = io.NopCloser(bytes.NewBuffer(sanitizedJSON))
		r.ContentLength = int64(len(sanitizedJSON))
		r.Header.Set("Content-Type", "application/json")

		next(w, r)
	}
}

func sanitizeValue(v interface{}) interface{} {
	switch val := v.(type) {
	case map[string]interface{}:
		for k, v := range val {
			val[k] = sanitizeValue(v)
		}
		return val
	case []interface{}:
		for i, v := range val {
			val[i] = sanitizeValue(v)
		}
		return val
	case string:
		s := val
		// Strip HTML tags
		s = htmlTagRegex.ReplaceAllString(s, "")
		// Escape dangerous characters
		s = xssCharRx.ReplaceAllString(s, "")
		// Block basic SQL injection patterns
		if sqlInjectionRx.MatchString(s) {
			s = "[SANITIZED]"
		}
		// Enforce maximum length to prevent buffer overflow in downstream systems
		if len(s) > 500 {
			s = s[:500]
		}
		return s
	default:
		return v
	}
}

func writeJSONError(w http.ResponseWriter, status int, errors []string) {
	w.Header().Set("Content-Type", "application/json")
	w.WriteHeader(status)
	json.NewEncoder(w).Encode(DataActionResponse{Errors: errors})
}

The sanitization function operates recursively to handle nested JSON objects and arrays. It removes HTML tags, escapes characters commonly used in cross-site scripting, blocks basic SQL injection keywords, and truncates strings exceeding five hundred characters. This prevents downstream external services from receiving malformed or dangerous payloads.

Step 3: Implement Output Masking Middleware

Output masking protects sensitive data from leaking into Genesys Cloud workflow logs or external system responses. The middleware captures the response body, unmarshals it, applies field-level masking rules based on key names, and writes the sanitized JSON back to the client.

package main

import (
	"encoding/json"
	"net/http"
	"regexp"
	"strings"
)

var sensitiveFieldRx = regexp.MustCompile(`(?i)(password|token|secret|ssn|social_security|credit_card|cvv|authorization)`)

func MaskOutputMiddleware(next http.HandlerFunc) http.HandlerFunc {
	return func(w http.ResponseWriter, r *http.Request) {
		rc := &responseCapture{ResponseWriter: w, body: &bytes.Buffer{}}
		next(rc, r)

		var resp DataActionResponse
		if err := json.Unmarshal(rc.body.Bytes(), &resp); err != nil {
			// If the response is not valid JSON, pass it through unchanged
			w.Write(rc.body.Bytes())
			return
		}

		if resp.Output != nil {
			maskValue(resp.Output)
		}

		maskedJSON, err := json.Marshal(resp)
		if err != nil {
			writeJSONError(w, http.StatusInternalServerError, []string{"Failed to marshal masked response"})
			return
		}

		w.Header().Set("Content-Type", "application/json")
		w.Write(maskedJSON)
	}
}

func maskValue(v interface{}) {
	switch val := v.(type) {
	case map[string]interface{}:
		for k, v := range val {
			if sensitiveFieldRx.MatchString(k) {
				val[k] = "****MASKED****"
			} else {
				maskValue(v)
			}
		}
	case []interface{}:
		for i, v := range val {
			maskValue(val[i])
		}
	}
}

The masking middleware inspects every key in the output map. If a key matches the sensitive field pattern, the value is replaced with a static masked string. The function recurses through nested structures to ensure deep masking. This guarantees that credentials, tokens, and personally identifiable information never leave the Data Action runtime in plaintext.

Step 4: Wire Middleware to External Service Calls with Retry Logic

The final handler processes the sanitized input, calls an external service, applies retry logic for rate limits, and returns the masked output. The middleware chain wraps this handler to enforce security boundaries at both ingress and egress.

package main

import (
	"bytes"
	"encoding/json"
	"fmt"
	"io"
	"log"
	"net/http"
	"time"
)

func ExternalServiceHandler(client *http.Client) http.HandlerFunc {
	return func(w http.ResponseWriter, r *http.Request) {
		var req DataActionRequest
		if err := json.NewDecoder(r.Body).Decode(&req); err != nil {
			writeJSONError(w, http.StatusBadRequest, []string{"Invalid request payload"))
			return
		}

		// Simulate external service payload
		externalPayload := map[string]interface{}{
			"action": "process_request",
			"input":  req.Input,
		}
		payloadBytes, _ := json.Marshal(externalPayload)

		// Call external service with retry logic for 429 responses
		resp, err := callExternalWithRetry(client, "https://api.external-service.com/v1/process", payloadBytes)
		if err != nil {
			writeJSONError(w, http.StatusBadGateway, []string{fmt.Sprintf("External service call failed: %v", err)})
			return
		}
		defer resp.Body.Close()

		if resp.StatusCode >= 400 {
			body, _ := io.ReadAll(resp.Body)
			writeJSONError(w, resp.StatusCode, []string{fmt.Sprintf("External service error: %s", string(body))})
			return
		}

		var externalResp map[string]interface{}
		if err := json.NewDecoder(resp.Body).Decode(&externalResp); err != nil {
			writeJSONError(w, http.StatusInternalServerError, []string{"Failed to decode external response"))
			return
		}

		// Return success response
		w.Write([]byte(fmt.Sprintf(`{"output": %s}`, string(payloadBytes))))
	}
}

func callExternalWithRetry(client *http.Client, url string, body []byte) (*http.Response, error) {
	maxRetries := 3
	var lastErr error

	for attempt := 0; attempt <= maxRetries; attempt++ {
		req, err := http.NewRequest("POST", url, bytes.NewBuffer(body))
		if err != nil {
			return nil, fmt.Errorf("request creation failed: %w", err)
		}
		req.Header.Set("Content-Type", "application/json")

		resp, err := client.Do(req)
		if err != nil {
			lastErr = fmt.Errorf("http call failed: %w", err)
			continue
		}

		if resp.StatusCode == http.StatusTooManyRequests {
			retryAfter := 1 << attempt
			log.Printf("Rate limited. Retrying in %d seconds...", retryAfter)
			time.Sleep(time.Duration(retryAfter) * time.Second)
			lastErr = fmt.Errorf("rate limited on attempt %d", attempt)
			continue
		}

		return resp, nil
	}

	return nil, fmt.Errorf("max retries exceeded: %w", lastErr)
}

The external service handler decodes the sanitized input, constructs a payload, and invokes the downstream API. The callExternalWithRetry function implements exponential backoff for 429 Too Many Requests responses. This prevents cascade failures when external providers enforce strict rate limits. The handler returns a structured response that the masking middleware intercepts before transmission.

Complete Working Example

The following script combines all components into a single executable server. It registers the middleware chain, configures the HTTP client, and starts the listener on port 8080. Replace YOUR_SECURE_ACTION_SECRET with your Genesys Cloud Data Action secret.

package main

import (
	"log"
	"net/http"
	"time"
)

func main() {
	// Configure HTTP client with reasonable timeouts
	httpClient := &http.Client{
		Timeout: 10 * time.Second,
	}

	// Base handler that processes external calls
	baseHandler := ExternalServiceHandler(httpClient)

	// Apply middleware chain: sanitize input -> call external -> mask output
	secureHandler := MaskOutputMiddleware(SanitizeInputMiddleware(baseHandler))

	// Register route matching Genesys Cloud Data Action contract
	http.HandleFunc("/execute", secureHandler)

	log.Println("Data Action server starting on :8080")
	if err := http.ListenAndServe(":8080", nil); err != nil {
		log.Fatalf("Server failed to start: %v", err)
	}
}

Run the server with go run main.go. Test the endpoint using curl:

curl -X POST http://localhost:8080/execute \
  -H "Content-Type: application/json" \
  -H "X-Genesys-Action-Secret: YOUR_SECURE_ACTION_SECRET" \
  -d '{"input": {"user_name": "<script>alert(1)</script>", "api_token": "sk_live_12345", "message": "Valid input"}}'

The response will strip the script tag, truncate if necessary, and mask the api_token field before returning to the caller.

Common Errors & Debugging

Error: 400 Bad Request (Invalid JSON payload)

• Cause: The request body is malformed, missing the input object, or contains invalid UTF-8 sequences.
• Fix: Validate the JSON structure before transmission. Ensure the Content-Type header is set to application/json. The middleware returns a structured errors array matching the Genesys contract.
• Code showing the fix:

// Verify payload structure in client code
payload := map[string]interface{}{
    "input": map[string]interface{}{
        "field": "value",
    },
}
jsonBytes, _ := json.Marshal(payload)
req, _ := http.NewRequest("POST", actionURL, bytes.NewBuffer(jsonBytes))

Error: 401 Unauthorized (Invalid or missing action secret)

• Cause: The X-Genesys-Action-Secret header is missing, mismatched, or truncated.
• Fix: Verify the secret matches the value configured in the Genesys Cloud Data Action definition. Ensure the header is transmitted exactly as registered. Do not URL-encode the secret value.
• Code showing the fix:

req.Header.Set("X-Genesys-Action-Secret", "exact_secret_from_genesys_console")

Error: 429 Too Many Requests (External service rate limit)

• Cause: The downstream API enforces request quotas. The initial call exceeds the threshold.
• Fix: The callExternalWithRetry function implements exponential backoff. If the external provider returns a Retry-After header, parse it and sleep for the specified duration instead of using the default backoff calculation.
• Code showing the fix:

if resp.StatusCode == http.StatusTooManyRequests {
    if retryAfter := resp.Header.Get("Retry-After"); retryAfter != "" {
        seconds, _ := strconv.Atoi(retryAfter)
        time.Sleep(time.Duration(seconds) * time.Second)
    } else {
        time.Sleep(time.Duration(1<<attempt) * time.Second)
    }
}

Error: 500 Internal Server Error (Failed to marshal masked response)

• Cause: The response contains non-JSON data, circular references, or unsupported types that encoding/json cannot serialize.
• Fix: Ensure all values in the output map are JSON-serializable. Remove channels, functions, or custom structs without JSON tags. Add explicit type assertions before marshaling.
• Code showing the fix:

// Validate output structure before returning
if resp.Output == nil {
    resp.Output = make(map[string]interface{})
}
// Remove non-serializable fields programmatically before marshaling

Official References

• Genesys Cloud Data Actions Documentation
• Genesys Cloud OAuth 2.0 Client Credentials Flow
• Go net/http Middleware Patterns
• Go encoding/json Package Reference