edge/pkg/module/auth/http/passwd/argon2id/hasher.go

package argon2id

import (
	"crypto/rand"
	"crypto/subtle"
	"encoding/base64"
	"fmt"
	"strings"

	"forge.cadoles.com/arcad/edge/pkg/module/auth/http/passwd"
	"github.com/pkg/errors"
	"golang.org/x/crypto/argon2"
)

const (
	Algo passwd.Algo = "argon2id"
)

func init() {
	passwd.Register(Algo, &Hasher{})
}

var (
	ErrInvalidHash         = errors.New("invalid hash")
	ErrIncompatibleVersion = errors.New("incompatible version")
)

type params struct {
	memory      uint32
	iterations  uint32
	parallelism uint8
	saltLength  uint32
	keyLength   uint32
}

var defaultParams = params{
	memory:      64 * 1024,
	iterations:  3,
	parallelism: 2,
	saltLength:  16,
	keyLength:   32,
}

type Hasher struct{}

// Hash implements passwd.Hasher
func (*Hasher) Hash(plaintext string) (string, error) {
	salt, err := generateRandomBytes(defaultParams.saltLength)
	if err != nil {
		return "", errors.WithStack(err)
	}

	hash := argon2.IDKey([]byte(plaintext), salt, defaultParams.iterations, defaultParams.memory, defaultParams.parallelism, defaultParams.keyLength)

	// Base64 encode the salt and hashed password.
	b64Salt := base64.RawStdEncoding.EncodeToString(salt)
	b64Hash := base64.RawStdEncoding.EncodeToString(hash)

	// Return a string using the standard encoded hash representation.
	encodedHash := fmt.Sprintf("$argon2id$v=%d$m=%d,t=%d,p=%d$%s$%s", argon2.Version, defaultParams.memory, defaultParams.iterations, defaultParams.parallelism, b64Salt, b64Hash)

	return encodedHash, nil
}

// Match implements passwd.Hasher.
func (*Hasher) Match(plaintext string, hash string) (bool, error) {
	matches, err := comparePasswordAndHash(plaintext, hash)
	if err != nil {
		return false, errors.WithStack(err)
	}

	return matches, nil
}

var _ passwd.Hasher = &Hasher{}

func generateRandomBytes(n uint32) ([]byte, error) {
	buf := make([]byte, n)

	if _, err := rand.Read(buf); err != nil {
		return nil, errors.WithStack(err)
	}

	return buf, nil
}

func comparePasswordAndHash(password, encodedHash string) (match bool, err error) {
	p, salt, hash, err := decodeHash(encodedHash)
	if err != nil {
		return false, errors.WithStack(err)
	}

	otherHash := argon2.IDKey([]byte(password), salt, p.iterations, p.memory, p.parallelism, p.keyLength)

	if subtle.ConstantTimeCompare(hash, otherHash) == 1 {
		return true, nil
	}

	return false, nil
}

func decodeHash(encodedHash string) (p *params, salt, hash []byte, err error) {
	vals := strings.Split(encodedHash, "$")
	if len(vals) != 6 {
		return nil, nil, nil, ErrInvalidHash
	}

	var version int
	_, err = fmt.Sscanf(vals[2], "v=%d", &version)
	if err != nil {
		return nil, nil, nil, err
	}
	if version != argon2.Version {
		return nil, nil, nil, ErrIncompatibleVersion
	}

	p = &params{}
	_, err = fmt.Sscanf(vals[3], "m=%d,t=%d,p=%d", &p.memory, &p.iterations, &p.parallelism)
	if err != nil {
		return nil, nil, nil, err
	}

	salt, err = base64.RawStdEncoding.Strict().DecodeString(vals[4])
	if err != nil {
		return nil, nil, nil, err
	}
	p.saltLength = uint32(len(salt))

	hash, err = base64.RawStdEncoding.Strict().DecodeString(vals[5])
	if err != nil {
		return nil, nil, nil, err
	}
	p.keyLength = uint32(len(hash))

	return p, salt, hash, nil
}