Go Masker v2

Go Masker v2 is a simple and extensible library for masking sensitive data in Go structs. Use struct tags to control how fields are masked — passwords, emails, IDs, credit cards, and more.

• Install
• Quick Start
• Masker Types
• Custom Mask Character
• Abuse Masker
• Custom Masker
• Contributors

Install

go get -u github.com/ggwhite/go-masker/v2

Quick Start

package main

import (
    "log"
    masker "github.com/ggwhite/go-masker/v2"
)

type User struct {
    Name     string `mask:"name"`
    Email    string `mask:"email"`
    Password string `mask:"password"`
    Mobile   string `mask:"mobile"`
}

func main() {
    u := &User{
        Name:     "John Doe",
        Email:    "john@gmail.com",
        Password: "secret",
        Mobile:   "0987654321",
    }

    m := masker.NewMaskerMarshaler()
    masked, err := m.Struct(u)
    if err != nil {
        log.Fatal(err)
    }
    log.Println(masked) // &{J**n D**e joh****@gmail.com ************** 0987***321}
}

You can also use the package-level default instance:

masked, err := masker.DefaultMaskerMarshaler.Struct(u)

Masker Types

Tag	Description	Example Input	Example Output
none	No masking, return as-is	foo	foo
password	Always returns 14 asterisks	secret	**************
name	Masks middle characters	John Doe	J**n D**e
addr	Masks last 6 characters	台北市內湖區內湖路一段737巷1號	台北市內湖區內湖路一段7******
email	Keeps first 3 chars and domain	john@gmail.com	joh****@gmail.com
mobile	Masks 3 digits from 4th position	0987654321	0987***321
tel	Formats and masks last 4 digits	0227993078	(02)2799-****
id	Masks digits 7–10	A123456789	A12345****
credit	Masks digits 7–12	4111111111111111	411111******1111
url	Masks URL password	http://user:pass@host	http://user:xxxxx@host
abuse	Masks abusive words via trie	bad word	*** word
struct	Recursively masks nested struct	—	—

Masking Slices

String slices are also supported:

type Foo struct {
    Tags []string `mask:"name"`
}

Masking Nested Structs

type Address struct {
    Street string `mask:"addr"`
}

type User struct {
    Name    string  `mask:"name"`
    Address Address `mask:"struct"`
}

Custom Mask Character

By default, * is used as the mask character. Use SetMasker to change it:

m := masker.NewMaskerMarshaler()
m.SetMasker("#")

masked, _ := m.Struct(u)
// Name "John" -> "J##n"

Abuse Masker

The abuse masker uses a trie for efficient word matching and replacement.

Basic Usage

abuseWords := []string{"bad", "terrible", "awful"}
abuseMasker := masker.NewAbuseMaskerWithWords(abuseWords)

text := "This is a bad and terrible situation"
masked := abuseMasker.Marshal("*", text)
// Output: "This is a *** and ******** situation"

Load Words from File

loader := masker.NewAbuseWordLoader()
words, err := loader.LoadFromFile("abuse_words.txt")
if err != nil {
    log.Fatal(err)
}
abuseMasker := masker.NewAbuseMaskerWithWords(words)

Use with Struct Tags

type Post struct {
    Title   string `mask:"name"`
    Content string `mask:"abuse"`
}

m := masker.NewMaskerMarshaler()
m.Register(masker.MaskerTypeAbuse, masker.NewAbuseMaskerWithWords([]string{"bad"}))

masked, _ := m.Struct(&Post{Title: "Hello", Content: "bad content"})

Custom Masker

Implement the Masker interface to create your own masker:

type Masker interface {
    Marshal(maskChar string, value string) string
}

Example:

type SSNMasker struct{}

func (m *SSNMasker) Marshal(s, i string) string {
    if len(i) != 9 {
        return i
    }
    return "***-**-" + i[7:]
}

m := masker.NewMaskerMarshaler()
m.Register("ssn", &SSNMasker{})

type Person struct {
    SSN string `mask:"ssn"`
}

Contributors

Thanks to all the people who already contributed!