xmidt-org/themis

package random

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

const DefaultNonceSize = 16

// Noncer is a strategy for creating nonces for JWTs, to be stored in the jti claim.
type Noncer interface {
    Nonce() (string, error)
}

type base64Noncer struct {
    random   io.Reader
    size     int
    encoding *base64.Encoding
}

func (n base64Noncer) Nonce() (string, error) {
    b := make([]byte, n.size)
    if _, err := n.random.Read(b); err != nil {
        return "", err
    }

    return n.encoding.EncodeToString(b), nil
}

// NewBase64Noncer creates a Noncer that generates a random sequence of bits encoded via
// the given base64 encoding.  All parameters have defaults:
//
// If random is nil, crypto/rand.Reader is used
// If size is nonpositive, DefaultNonceSize is used
// if encoding is nil, base64.RawURLEncoding is used
func NewBase64Noncer(random io.Reader, size int, encoding *base64.Encoding) Noncer {
    if random == nil {
        random = rand.Reader
    }

    if size <= 0 {
        size = DefaultNonceSize
    }

    if encoding == nil {
        encoding = base64.RawURLEncoding
    }

    return base64Noncer{
        random:   random,
        size:     size,
        encoding: encoding,
    }
}