cmd/pwtool/main.go

@@ -86,7 +86,7 @@ func mkhash() (pwhash.PasswordHash, string, error) {
 	name := *algo
 	switch *algo {
 	case "argon2":
-		h = pwhash.NewArgon2WithParams(uint32(*argon2Time), uint32(*argon2Mem*1024), uint8(*argon2Threads))
+		h = pwhash.NewArgon2StdWithParams(uint32(*argon2Time), uint32(*argon2Mem*1024), uint8(*argon2Threads))
 		name = fmt.Sprintf("%s(%d/%d/%d)", *algo, *argon2Time, *argon2Mem, *argon2Threads)
 	case "scrypt":
 		h = pwhash.NewScryptWithParams(*scryptN, *scryptR, *scryptP)

pwhash/argon2.go

@@ -6,15 +6,15 @@ import (
 	"encoding/hex"
 	"errors"
 	"fmt"
-	"log"
 	"strconv"
 	"strings"
 
 	"golang.org/x/crypto/argon2"
 )
 
-var (
-	argonKeyLen  uint32 = 32
+const (
+	argonLegacyKeySize  = 32
+	argonDefaultKeySize = 16
 	argonSaltLen        = 16
 )
 
@@ -29,9 +29,11 @@ type argon2PasswordHash struct {
 
 // newArgon2PasswordHash returns an Argon2i-based PasswordHash using the
 // specified parameters for time, memory, and number of threads.
-func newArgon2PasswordHash(time, mem uint32, threads uint8, codec argon2Codec) PasswordHash {
+func newArgon2PasswordHash(kind string, keySize int, time, mem uint32, threads uint8, codec argon2Codec) PasswordHash {
 	return &argon2PasswordHash{
 		params: argon2Params{
+			KeySize: keySize,
+			Kind:    kind,
 			Time:    time,
 			Memory:  mem,
 			Threads: threads,
@@ -41,8 +43,8 @@ func newArgon2PasswordHash(time, mem uint32, threads uint8, codec argon2Codec) P
 }
 
 // NewArgon2 returns an Argon2i-based PasswordHash using the default parameters.
-func NewArgon2() PasswordHash {
-	return NewArgon2WithParams(
+func NewArgon2Legacy() PasswordHash {
+	return NewArgon2LegacyWithParams(
 		defaultArgon2Params.Time,
 		defaultArgon2Params.Memory,
 		defaultArgon2Params.Threads,
@@ -51,8 +53,8 @@ func NewArgon2() PasswordHash {
 
 // NewArgon2WithParams returns an Argon2i-based PasswordHash using the
 // specified parameters for time, memory, and number of threads.
-func NewArgon2WithParams(time, mem uint32, threads uint8) PasswordHash {
-	return newArgon2PasswordHash(time, mem, threads, &a2Codec{})
+func NewArgon2LegacyWithParams(time, mem uint32, threads uint8) PasswordHash {
+	return newArgon2PasswordHash(kindArgon2I, argonLegacyKeySize, time, mem, threads, &a2LegacyCodec{})
 }
 
 // NewArgon2Std returns an Argon2i-based PasswordHash that conforms
@@ -65,12 +67,12 @@ func NewArgon2Std() PasswordHash {
 	)
 }
 
-// NewArgon2StdWithParams returns an Argon2i-based PasswordHash using
+// NewArgon2StdWithParams returns an Argon2id-based PasswordHash using
 // the specified parameters for time, memory, and number of
-// threads. This will use the string encoding ("$argon2$") documented
+// threads. This will use the string encoding ("$argon2id$") documented
 // in the argon2 reference implementation.
 func NewArgon2StdWithParams(time, mem uint32, threads uint8) PasswordHash {
-	return newArgon2PasswordHash(time, mem, threads, &argon2StdCodec{})
+	return newArgon2PasswordHash(kindArgon2ID, argonDefaultKeySize, time, mem, threads, &argon2StdCodec{})
 }
 
 // ComparePassword returns true if the given password matches the
@@ -80,28 +82,53 @@ func (s *argon2PasswordHash) ComparePassword(encrypted, password string) bool {
 	if err != nil {
 		return false
 	}
-	dk2 := argon2.Key([]byte(password), salt, params.Time, params.Memory, params.Threads, argonKeyLen)
+
+	dk2 := params.hash(password, salt)
 	return subtle.ConstantTimeCompare(dk, dk2) == 1
 }
 
 // Encrypt the given password with the Argon2 algorithm.
 func (s *argon2PasswordHash) Encrypt(password string) string {
 	salt := getRandomBytes(argonSaltLen)
-	dk := argon2.Key([]byte(password), salt, s.params.Time, s.params.Memory, s.params.Threads, argonKeyLen)
+	dk := s.params.hash(password, salt)
 	return s.codec.encodeArgon2Hash(s.params, salt, dk)
 }
 
+const (
+	kindArgon2I  = "argon2i"
+	kindArgon2ID = "argon2id"
+)
+
 type argon2Params struct {
+	Kind    string
+	KeySize int
 	Time    uint32
 	Memory  uint32
 	Threads uint8
 }
 
+func (p argon2Params) hash(password string, salt []byte) []byte {
+	if p.KeySize == 0 {
+		panic("key size is 0")
+	}
+
+	switch p.Kind {
+	case kindArgon2I:
+		return argon2.Key([]byte(password), salt, p.Time, p.Memory, p.Threads, uint32(p.KeySize))
+	case kindArgon2ID:
+		return argon2.IDKey([]byte(password), salt, p.Time, p.Memory, p.Threads, uint32(p.KeySize))
+	default:
+		panic("unknown argon2 hash kind")
+	}
+}
+
 // Default Argon2 parameters are tuned for a high-traffic
 // authentication service (<1ms per operation).
 var defaultArgon2Params = argon2Params{
+	Kind:    kindArgon2ID,
+	KeySize: 16,
 	Time:    1,
-	Memory:  4 * 1024,
+	Memory:  64 * 1024,
 	Threads: 4,
 }
 
@@ -110,13 +137,14 @@ type argon2Codec interface {
 	decodeArgon2Hash(string) (argon2Params, []byte, []byte, error)
 }
 
-type a2Codec struct{}
+// Argon2i legacy encoding, do not use.
+type a2LegacyCodec struct{}
 
-func (*a2Codec) encodeArgon2Hash(params argon2Params, salt, dk []byte) string {
+func (*a2LegacyCodec) encodeArgon2Hash(params argon2Params, salt, dk []byte) string {
 	return fmt.Sprintf("$a2$%d$%d$%d$%x$%x", params.Time, params.Memory, params.Threads, salt, dk)
 }
 
-func (*a2Codec) decodeArgon2Hash(s string) (params argon2Params, salt []byte, dk []byte, err error) {
+func (*a2LegacyCodec) decodeArgon2Hash(s string) (params argon2Params, salt []byte, dk []byte, err error) {
 	if !strings.HasPrefix(s, "$a2$") {
 		err = errors.New("not an Argon2 password hash")
 		return
@@ -128,6 +156,8 @@ func (*a2Codec) decodeArgon2Hash(s string) (params argon2Params, salt []byte, dk
 		return
 	}
 
+	params.Kind = kindArgon2I
+
 	var i uint64
 
 	if i, err = strconv.ParseUint(parts[0], 10, 32); err != nil {
@@ -149,16 +179,36 @@ func (*a2Codec) decodeArgon2Hash(s string) (params argon2Params, salt []byte, dk
 	if err != nil {
 		return
 	}
+
 	dk, err = hex.DecodeString(parts[4])
+	if err != nil {
+		return
+	}
+
+	params.KeySize = len(dk)
+	switch len(dk) {
+	case 16, 24, 32:
+	default:
+		err = errors.New("bad key size")
+	}
+
 	return
 }
 
+// Standard Argon2 encoding as per the reference implementation in
+// https://github.com/P-H-C/phc-winner-argon2/blob/4ac8640c2adc1257677d27d3f833c8d1ee68c7d2/src/encoding.c#L242-L252
 type argon2StdCodec struct{}
 
+const argon2HashVersionStr = "v=19"
+
 func (*argon2StdCodec) encodeArgon2Hash(params argon2Params, salt, dk []byte) string {
 	encSalt := base64.RawStdEncoding.EncodeToString(salt)
 	encDK := base64.RawStdEncoding.EncodeToString(dk)
-	return fmt.Sprintf("$argon2i$v=19$m=%d,t=%d,p=%d$%s$%s", params.Memory, params.Time, params.Threads, encSalt, encDK)
+	return fmt.Sprintf(
+		"$%s$%s$m=%d,t=%d,p=%d$%s$%s",
+		params.Kind, argon2HashVersionStr,
+		params.Memory, params.Time, params.Threads,
+		encSalt, encDK)
 }
 
 func parseArgon2HashParams(s string) (params argon2Params, err error) {
@@ -182,7 +232,7 @@ func parseArgon2HashParams(s string) (params argon2Params, err error) {
 			i, err = strconv.ParseUint(kv[1], 10, 8)
 			params.Threads = uint8(i)
 		default:
-			err = errors.New("unknown parameter in hash")
+			err = fmt.Errorf("unknown parameter '%s' in hash", kv[0])
 		}
 		if err != nil {
 			return
@@ -192,30 +242,46 @@ func parseArgon2HashParams(s string) (params argon2Params, err error) {
 }
 
 func (*argon2StdCodec) decodeArgon2Hash(s string) (params argon2Params, salt []byte, dk []byte, err error) {
-	if !strings.HasPrefix(s, "$argon2i$") {
+	var kind string
+	switch {
+	case strings.HasPrefix(s, "$argon2i$"):
+		kind = kindArgon2I
+	case strings.HasPrefix(s, "$argon2id$"):
+		kind = kindArgon2ID
+	default:
 		err = errors.New("not an Argon2 password hash")
 		return
 	}
 
-	parts := strings.SplitN(s[9:], "$", 4)
-	if len(parts) != 4 {
+	parts := strings.SplitN(s, "$", 6)
+	if len(parts) != 6 {
 		err = errors.New("bad encoding")
 		return
 	}
-	if parts[0] != "v=19" {
+	if parts[2] != argon2HashVersionStr {
 		err = errors.New("bad argon2 hash version")
 		return
 	}
 
-	params, err = parseArgon2HashParams(parts[1])
+	params, err = parseArgon2HashParams(parts[3])
 	if err != nil {
 		return
 	}
-	if salt, err = base64.RawStdEncoding.DecodeString(parts[2]); err != nil {
+	params.Kind = kind
+
+	if salt, err = base64.RawStdEncoding.DecodeString(parts[4]); err != nil {
+		return
+	}
+	if dk, err = base64.RawStdEncoding.DecodeString(parts[5]); err != nil {
 		return
 	}
-	dk, err = base64.RawStdEncoding.DecodeString(parts[3])
 
-	log.Printf("params: %+v", params)
+	params.KeySize = len(dk)
+	switch len(dk) {
+	case 16, 24, 32:
+	default:
+		err = errors.New("bad key size")
+	}
+
 	return
 }

pwhash/password.go

@@ -18,7 +18,6 @@
 //
 //	go test -bench=Argon2 -run=none . 2>&1 | \
 //	    awk '/^Bench/ {ops=1000000000 / $3; print $1 " " ops " ops/sec"}'
-//
 package pwhash
 
 import (
@@ -53,8 +52,9 @@ var prefixRegistry = map[string]PasswordHash{
 	"$5$":        NewSystemCrypt(),
 	"$6$":        NewSystemCrypt(),
 	"$s$":        NewScrypt(),
-	"$a2$":      NewArgon2(),
+	"$a2$":       NewArgon2Legacy(),
 	"$argon2i$":  NewArgon2Std(),
+	"$argon2id$": NewArgon2Std(),
 }
 
 // ComparePassword returns true if the given password matches the
@@ -65,6 +65,7 @@ func ComparePassword(encrypted, password string) bool {
 			return h.ComparePassword(encrypted, password)
 		}
 	}
+
 	return false
 }
 
@@ -73,7 +74,7 @@ func ComparePassword(encrypted, password string) bool {
 var DefaultEncryptAlgorithm PasswordHash
 
 func init() {
-	DefaultEncryptAlgorithm = NewArgon2()
+	DefaultEncryptAlgorithm = NewArgon2Std()
 }
 
 // Encrypt will encrypt a password with the default algorithm.

pwhash/password_test.go

@@ -5,8 +5,8 @@ import (
 	"testing"
 )
 
-func TestArgon2(t *testing.T) {
-	testImpl(t, NewArgon2())
+func TestArgon2Legacy(t *testing.T) {
+	testImpl(t, NewArgon2Legacy())
 }
 
 func TestArgon2Std(t *testing.T) {
@@ -65,7 +65,7 @@ func testImpl(t *testing.T, h PasswordHash) {
 	}
 }
 
-func TestStandardArgon2Password(t *testing.T) {
+func TestStandardArgon2IPassword(t *testing.T) {
 	enc := "$argon2i$v=19$m=32768,t=4,p=1$DG0B56zlrrx+VMVaM6wvsw$8iV+HwTKmofjrb+q9I2zZGQnGXzXtiIXv8VdHdvbbX8"
 	pw := "idontmindbirds"
 	if !ComparePassword(enc, pw) {
@@ -73,6 +73,15 @@ func TestStandardArgon2Password(t *testing.T) {
 	}
 }
 
+func TestStandardArgon2IDPassword(t *testing.T) {
+	// python3 -c 'from argon2 import PasswordHasher ; print(PasswordHasher().hash("idontmindbirds"))'
+	enc := "$argon2id$v=19$m=102400,t=2,p=8$7hQLBrHoxYxRO0R8km62pA$Dv5+BCctW4nCrxsy5C9JBg"
+	pw := "idontmindbirds"
+	if !ComparePassword(enc, pw) {
+		t.Fatal("comparison failed")
+	}
+}
+
 func BenchmarkArgon2(b *testing.B) {
 	var testParams []argon2Params
 	for iTime := 1; iTime <= 5; iTime++ {
@@ -93,7 +102,7 @@ func BenchmarkArgon2(b *testing.B) {
 	for _, tp := range testParams {
 		name := fmt.Sprintf("%d/%d/%d", tp.Time, tp.Memory, tp.Threads)
 		b.Run(name, func(b *testing.B) {
-			h := NewArgon2WithParams(tp.Time, tp.Memory, tp.Threads)
+			h := NewArgon2StdWithParams(tp.Time, tp.Memory, tp.Threads)
 			encPw := h.Encrypt(goodPw)
 
 			b.ResetTimer()