gogjango/gjango

package secret

import (
    "crypto/rand"
    "encoding/base64"
)

// GenerateRandomBytes returns securely generated random bytes.
// It will return an error if the system's secure random
// number generator fails to function correctly, in which
// case the caller should not continue.
func GenerateRandomBytes(n int) ([]byte, error) {
    b := make([]byte, n)
    _, err := rand.Read(b)
    // Note that err == nil only if we read len(b) bytes.
    if err != nil {
        return nil, err
    }

    return b, nil
}

// GenerateRandomString returns a securely generated random string.
// It will return an error if the system's secure random
// number generator fails to function correctly, in which
// case the caller should not continue.
// Example: this will give us a 32 byte output
// token, err = GenerateRandomString(32)
func GenerateRandomString(n int) (string, error) {
    const letters = "0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz-"
    bytes, err := GenerateRandomBytes(n)
    if err != nil {
        return "", err
    }
    for i, b := range bytes {
        bytes[i] = letters[b%byte(len(letters))]
    }
    return string(bytes), nil
}

// GenerateRandomStringURLSafe returns a URL-safe, base64 encoded
// securely generated random string.
// It will return an error if the system's secure random
// number generator fails to function correctly, in which
// case the caller should not continue.
// Example: this will give us a 44 byte, base64 encoded output
// token, err := GenerateRandomStringURLSafe(32)
func GenerateRandomStringURLSafe(n int) (string, error) {
    b, err := GenerateRandomBytes(n)
    return base64.URLEncoding.EncodeToString(b), err
}