Version: 1.1.2

Secret Types

Safely handle sensitive data with SecretStr and SecretBytes to prevent accidental exposure in logs, API responses, and error messages.

The Problem

Sensitive data like passwords, API keys, encryption keys, and tokens are frequently exposed by accident:

In logs: Developers print full structs with fmt.Printf, revealing secrets
In API responses: Marshaling to JSON without masking sensitive fields
In error messages: Stack traces or validation errors containing actual values
In middleware: Logging frameworks capturing request/response bodies

Pedantigo's secret types automatically mask sensitive data while preserving the actual value for internal use.

SecretStr

Use SecretStr for string-based secrets: passwords, API keys, tokens, and other sensitive strings.

Overview

type SecretStr struct {
    // value is unexported and private
}

// Create a new secret
func NewSecretStr(s string) SecretStr

// Get the actual secret value
func (s SecretStr) Value() string

// Returns "**********" (safe for logs)
func (s SecretStr) String() string

// Returns "**********" (safe for JSON output)
func (s SecretStr) MarshalJSON() ([]byte, error)

// Stores actual value from JSON input
func (s *SecretStr) UnmarshalJSON(data []byte) error

Behavior

Method	Output	Use Case
`Value()`	Actual secret	Internal processing, passing to external services
`String()`	"**********"	fmt.Printf, string concatenation, logging
`MarshalJSON()`	"**********"	JSON serialization, API responses
`UnmarshalJSON()`	Stores actual value	JSON deserialization, form input

Example: In Struct Definitions

type Config struct {
    // Database connection string (sensitive)
    DatabaseURL SecretStr `json:"database_url" pedantigo:"required"`

    // API authentication token
    APIToken SecretStr `json:"api_token" pedantigo:"required,min=20"`

    // Webhook secret for signature verification
    WebhookSecret SecretStr `json:"webhook_secret" pedantigo:"required"`
}

Accessing the Value

config, err := pedantigo.Unmarshal[Config](jsonData)
if err != nil {
    return err
}

// Get the actual secret for use
dbURL := config.DatabaseURL.Value()  // Returns: "postgres://user:pass@host/db"

// Connect to database
db, err := sql.Open("postgres", dbURL)

Logging Safety

When logging structs, the secret is automatically masked:

config := &Config{
    DatabaseURL: NewSecretStr("postgres://user:password123@localhost/mydb"),
    APIToken:    NewSecretStr("sk-1234567890abcdefghijklmn"),
}

// Safe - secrets are masked
fmt.Printf("Config: %v\n", config)
// Output: Config: {DatabaseURL:********** APIToken:**********}

// Also safe - String() method returns masked value
log.Infof("Config loaded with token %s", config.APIToken)
// Log: Config loaded with token **********

API Response Safety

When marshaling to JSON, secrets are automatically masked:

config := &Config{
    DatabaseURL: NewSecretStr("postgres://user:password123@localhost/mydb"),
    APIToken:    NewSecretStr("sk-1234567890abcdefghijklmn"),
}

// Marshal for API response
jsonData, err := pedantigo.Marshal(config)
if err != nil {
    return err
}

// The returned JSON will contain masked values
// {"database_url":"**********","api_token":"**********"}

// Safe to send in HTTP response without data leaks
http.HandleFunc("/api/config", func(w http.ResponseWriter, r *http.Request) {
    w.Header().Set("Content-Type", "application/json")
    w.Write(jsonData)  // No secrets exposed
})

Complete Example

package main

import (
    "fmt"
    "log"
    "github.com/smrutai/pedantigo"
)

type AppConfig struct {
    // Database credentials
    DatabaseURL SecretStr `json:"database_url" pedantigo:"required"`

    // External service API key
    ExternalAPIKey SecretStr `json:"external_api_key" pedantigo:"required,min=20"`

    // Application name (not sensitive)
    AppName string `json:"app_name" pedantigo:"required,min=1"`
}

func main() {
    // 1. Unmarshal from JSON (actual values stored internally)
    jsonInput := []byte(`{
        "database_url": "postgres://admin:secretpass@localhost:5432/myapp",
        "external_api_key": "sk-1234567890abcdefghijklmnopqrst",
        "app_name": "MyApp"
    }`)

    config, err := pedantigo.Unmarshal[AppConfig](jsonInput)
    if err != nil {
        log.Fatalf("Failed to load config: %v", err)
    }

    // 2. Log the config - secrets are automatically masked
    fmt.Printf("Loaded config: %+v\n", config)
    // Output: Loaded config: {DatabaseURL:********** ExternalAPIKey:********** AppName:MyApp}

    // 3. Access actual secret value only when needed
    dbURL := config.DatabaseURL.Value()  // "postgres://admin:secretpass@localhost:5432/myapp"
    apiKey := config.ExternalAPIKey.Value()  // "sk-1234567890abcdefghijklmnopqrst"

    // Use secrets for actual operations
    setupDatabase(dbURL)
    setupExternalAPI(apiKey)

    // 4. Marshal back to JSON - secrets are masked
    response, _ := pedantigo.Marshal(config)
    fmt.Println(string(response))
    // Output: {"database_url":"**********","external_api_key":"**********","app_name":"MyApp"}

    // Safe to include in API responses without data leaks
}

func setupDatabase(url string) {
    // Use the actual secret
    fmt.Printf("Connecting to database at %s\n", url)
}

func setupExternalAPI(key string) {
    // Use the actual secret
    fmt.Printf("Setting up API with key %s\n", key)
}

SecretBytes

Use SecretBytes for binary secrets: encryption keys, authentication certificates, and other binary data.

Overview

type SecretBytes struct {
    // value is unexported and private
}

// Create a new secret from bytes
func NewSecretBytes(b []byte) SecretBytes

// Get the actual secret bytes
func (s SecretBytes) Value() []byte

// Returns "**********" (safe for logs)
func (s SecretBytes) String() string

// Returns "**********" (safe for JSON output)
func (s SecretBytes) MarshalJSON() ([]byte, error)

// Expects base64-encoded string in JSON input
func (s *SecretBytes) UnmarshalJSON(data []byte) error

Base64 Encoding for JSON

Since JSON cannot represent raw binary data, SecretBytes expects base64-encoded strings in JSON input:

type EncryptionConfig struct {
    // Encryption key as base64-encoded bytes
    EncryptionKey SecretBytes `json:"encryption_key" pedantigo:"required"`
}

// JSON must contain base64-encoded value
jsonInput := []byte(`{
    "encryption_key": "aGVsbG8gd29ybGQ="  // base64 for "hello world"
}`)

config, _ := pedantigo.Unmarshal[EncryptionConfig](jsonInput)

// Access actual bytes
key := config.EncryptionKey.Value()  // []byte("hello world")

// Marshal back to JSON - masked
output, _ := pedantigo.Marshal(config)
// {"encryption_key":"**********"}

Example: Encryption Key Management

package main

import (
    "crypto/aes"
    "crypto/cipher"
    "encoding/base64"
    "fmt"
    "github.com/smrutai/pedantigo"
)

type SecurityConfig struct {
    // 32-byte AES-256 encryption key (base64-encoded in JSON)
    EncryptionKey SecretBytes `json:"encryption_key" pedantigo:"required"`

    // HMAC key for signature verification
    HMACKey SecretBytes `json:"hmac_key" pedantigo:"required"`

    // Security level
    Level string `json:"level" pedantigo:"required,oneof=low medium high"`
}

func main() {
    // Generate keys (in real scenarios, load from secure storage)
    encKey := make([]byte, 32)  // 32 bytes for AES-256
    hmacKey := make([]byte, 32)

    // Encode to base64 for JSON
    encKeyB64 := base64.StdEncoding.EncodeToString(encKey)
    hmacKeyB64 := base64.StdEncoding.EncodeToString(hmacKey)

    // Create JSON input
    jsonInput := []byte(fmt.Sprintf(`{
        "encryption_key": "%s",
        "hmac_key": "%s",
        "level": "high"
    }`, encKeyB64, hmacKeyB64))

    // Load config
    config, err := pedantigo.Unmarshal[SecurityConfig](jsonInput)
    if err != nil {
        fmt.Printf("Failed to load security config: %v\n", err)
        return
    }

    // 1. Log the config - keys are masked
    fmt.Printf("Security config: %+v\n", config)
    // Output: Security config: {EncryptionKey:********** HMACKey:********** Level:high}

    // 2. Create cipher with actual key
    key := config.EncryptionKey.Value()  // Get actual 32 bytes
    block, _ := aes.NewCipher(key)
    cipher := cipher.NewGCM(block)

    // Use cipher for encryption/decryption
    nonce := make([]byte, cipher.NonceSize())
    ciphertext := cipher.Seal(nonce, nonce, []byte("secret data"), nil)
    fmt.Printf("Encrypted data: %s\n", base64.StdEncoding.EncodeToString(ciphertext))

    // 3. Marshal config - keys are masked
    output, _ := pedantigo.Marshal(config)
    // Safe to store or transmit: {"encryption_key":"**********","hmac_key":"**********","level":"high"}
}

Complete Integration Example

This example demonstrates using both SecretStr and SecretBytes together in a real-world scenario:

package main

import (
    "crypto/tls"
    "database/sql"
    "encoding/base64"
    "fmt"
    "log"
    "net/http"
    "github.com/smrutai/pedantigo"
)

type ServerConfig struct {
    // Server basics
    Host string `json:"host" pedantigo:"required"`
    Port int    `json:"port" pedantigo:"required,min=1,max=65535"`

    // Secrets - string-based
    JWTSecret  SecretStr `json:"jwt_secret" pedantigo:"required,min=32"`
    APIKey     SecretStr `json:"api_key" pedantigo:"required"`

    // Secrets - binary (base64-encoded)
    TLSCert SecretBytes `json:"tls_cert" pedantigo:"required"`
    TLSKey  SecretBytes `json:"tls_key" pedantigo:"required"`

    // Non-sensitive fields
    Environment string `json:"environment" pedantigo:"required,oneof=dev staging prod"`
    Timeout     int    `json:"timeout" pedantigo:"min=1,max=300"`
}

func main() {
    // Load config from JSON (from env file, config server, etc)
    configJSON := []byte(`{
        "host": "0.0.0.0",
        "port": 8443,
        "jwt_secret": "your-super-secret-jwt-key-must-be-at-least-32-chars",
        "api_key": "sk-1234567890abcdefghijklmnopqrstu",
        "tls_cert": "` + base64.StdEncoding.EncodeToString([]byte("cert-data")) + `",
        "tls_key": "` + base64.StdEncoding.EncodeToString([]byte("key-data")) + `",
        "environment": "prod",
        "timeout": 30
    }`)

    // Parse and validate
    config, err := pedantigo.Unmarshal[ServerConfig](configJSON)
    if err != nil {
        log.Fatalf("Invalid config: %v", err)
    }

    // Safe to log - secrets are automatically masked
    log.Infof("Starting server at %s:%d", config.Host, config.Port)
    log.Infof("Config: %+v", config)  // Secrets are "**********"

    // Set up HTTPS with actual secrets
    cert := config.TLSCert.Value()  // Get actual certificate bytes
    key := config.TLSKey.Value()    // Get actual key bytes

    tlsCert, err := tls.X509KeyPair(cert, key)
    if err != nil {
        log.Fatalf("Failed to load TLS credentials: %v", err)
    }

    // Set up server
    mux := http.NewServeMux()
    mux.HandleFunc("/health", func(w http.ResponseWriter, r *http.Request) {
        // Use JWT secret for token validation
        jwtSecret := config.JWTSecret.Value()

        // Validate request with JWT
        token := r.Header.Get("Authorization")
        if !validateToken(token, jwtSecret) {
            http.Error(w, "Unauthorized", http.StatusUnauthorized)
            return
        }

        w.Write([]byte(`{"status":"ok"}`))
    })

    mux.HandleFunc("/config", func(w http.ResponseWriter, r *http.Request) {
        // Safe to return config - secrets are masked
        configJSON, _ := pedantigo.Marshal(config)
        w.Header().Set("Content-Type", "application/json")
        w.Write(configJSON)
        // Secrets are "**********" - no data leaks!
    })

    // Start HTTPS server
    server := &http.Server{
        Addr:    fmt.Sprintf("%s:%d", config.Host, config.Port),
        Handler: mux,
        TLSConfig: &tls.Config{
            Certificates: []tls.Certificate{tlsCert},
        },
    }

    log.Fatal(server.ListenAndServeTLS("", ""))
}

func validateToken(token, secret string) bool {
    // Token validation using secret
    // This is a simplified example
    return token != "" && secret != ""
}

Best Practices

1. Use the Correct Type

// Good: Use SecretStr for strings
type Config struct {
    DatabasePassword SecretStr `json:"db_password"`
}

// Bad: Storing secrets in plain strings
type Config struct {
    DatabasePassword string `json:"db_password"`  // Will be visible in logs!
}

2. Always Get Value() When Needed

// Good: Get actual secret only when you need to use it
password := config.DatabasePassword.Value()
db.Connect(password)

// Bad: Logging or printing the struct
log.Println(config)  // Even with SecretStr, don't do this carelessly
fmt.Println(config)  // Use specific fields only

3. Use Base64 for Binary Secrets

// Good: Use base64-encoded strings in JSON
type Config struct {
    EncryptionKey SecretBytes `json:"encryption_key"`  // Expects base64 input
}

// In JSON:
// {"encryption_key": "aGVsbG8gd29ybGQ="}

// Bad: Trying to pass raw bytes (JSON doesn't support)
// {"encryption_key": [104, 101, 108, 108, 111]}  // Won't unmarshal properly

4. Combine with Other Constraints

// Good: Add validation constraints
type Config struct {
    APIKey SecretStr `json:"api_key" pedantigo:"required,min=20,max=100"`
    Secret SecretStr `json:"secret" pedantigo:"required"`
}

// This ensures:
// - Fields are required
// - APIKey is 20-100 characters
// - Both values are preserved and masked

5. Never Store Masked Values

// Good: Always work with actual secrets
actual := config.APIKey.Value()

// Bad: Trying to store the masked output
masked := config.APIKey.String()  // "**********"
useWithAPI(masked)  // This won't work!

Error Handling

Both SecretStr and SecretBytes report validation errors without exposing secrets:

type Config struct {
    APIKey SecretStr `json:"api_key" pedantigo:"required,min=32"`
}

// If validation fails, error message won't contain the actual secret
jsonInput := []byte(`{"api_key": "short"}`)
_, err := pedantigo.Unmarshal[Config](jsonInput)

// Error: validation error: field "api_key": constraint "min" failed
// The actual value "short" is NOT in the error message
log.Println(err)  // Safe to log - no secret exposed

Thread Safety

Both SecretStr and SecretBytes are safe to use concurrently:

var config *ServerConfig
var wg sync.WaitGroup

// Multiple goroutines can access the secrets safely
for i := 0; i < 100; i++ {
    wg.Add(1)
    go func() {
        defer wg.Done()

        // All goroutines can call Value() concurrently
        secret := config.JWTSecret.Value()
        apiKey := config.APIKey.Value()
        encKey := config.EncryptionKey.Value()

        // Process with secrets
        processRequest(secret, apiKey, encKey)
    }()
}

wg.Wait()

Summary

Feature	SecretStr	SecretBytes
Use for	Passwords, API keys, tokens	Encryption keys, certificates
JSON Input	Plain string	Base64-encoded string
`Value()`	Returns actual string	Returns actual bytes
`String()`	Returns "**********"	Returns "**********"
`MarshalJSON()`	Outputs "**********"	Outputs "**********"
Safe for logs	Yes	Yes
Safe for JSON output	Yes	Yes
Safe for API responses	Yes	Yes

Both types protect against accidental exposure while preserving full access to the actual secret values when needed.

The Problem​

SecretStr​

Overview​

Behavior​

Example: In Struct Definitions​

Accessing the Value​

Logging Safety​

API Response Safety​

Complete Example​

SecretBytes​

Overview​

Base64 Encoding for JSON​

Example: Encryption Key Management​

Complete Integration Example​

Best Practices​

1. Use the Correct Type​

2. Always Get Value() When Needed​

3. Use Base64 for Binary Secrets​

4. Combine with Other Constraints​

5. Never Store Masked Values​

Error Handling​

Thread Safety​

Summary​

The Problem

SecretStr

Overview

Behavior

Example: In Struct Definitions

Accessing the Value

Logging Safety

API Response Safety

Complete Example

SecretBytes

Overview

Base64 Encoding for JSON

Example: Encryption Key Management

Complete Integration Example

Best Practices

1. Use the Correct Type

2. Always Get Value() When Needed

3. Use Base64 for Binary Secrets

4. Combine with Other Constraints

5. Never Store Masked Values

Error Handling

Thread Safety

Summary