initial commit

internal/password/password.go

@@ -0,0 +1,90 @@
+package password
+
+import (
+	"crypto/rand"
+	"crypto/subtle"
+	"encoding/base64"
+	"errors"
+	"fmt"
+	"strconv"
+	"strings"
+
+	"golang.org/x/crypto/argon2"
+)
+
+const (
+	memory      = 64 * 1024
+	iterations  = 3
+	parallelism = 2
+	saltLength  = 16
+	keyLength   = 32
+)
+
+func Hash(value string) (string, error) {
+	if len(value) < 12 {
+		return "", errors.New("password must contain at least 12 characters")
+	}
+	return hash(value)
+}
+
+// HashDemo hashes intentionally weak, local-only seed credentials.
+func HashDemo(value string) (string, error) {
+	if value == "" {
+		return "", errors.New("demo password is empty")
+	}
+	return hash(value)
+}
+
+func hash(value string) (string, error) {
+	salt := make([]byte, saltLength)
+	if _, err := rand.Read(salt); err != nil {
+		return "", fmt.Errorf("generate password salt: %w", err)
+	}
+	hash := argon2.IDKey([]byte(value), salt, iterations, memory, parallelism, keyLength)
+	return fmt.Sprintf("$argon2id$v=19$m=%d,t=%d,p=%d$%s$%s",
+		memory, iterations, parallelism,
+		base64.RawStdEncoding.EncodeToString(salt),
+		base64.RawStdEncoding.EncodeToString(hash),
+	), nil
+}
+
+func Verify(encoded, value string) bool {
+	parts := strings.Split(encoded, "$")
+	if len(parts) != 6 || parts[1] != "argon2id" || parts[2] != "v=19" {
+		return false
+	}
+	var parsedMemory uint64
+	var parsedIterations uint64
+	var parsedParallelism uint64
+	for _, setting := range strings.Split(parts[3], ",") {
+		keyValue := strings.SplitN(setting, "=", 2)
+		if len(keyValue) != 2 {
+			return false
+		}
+		number, err := strconv.ParseUint(keyValue[1], 10, 32)
+		if err != nil {
+			return false
+		}
+		switch keyValue[0] {
+		case "m":
+			parsedMemory = number
+		case "t":
+			parsedIterations = number
+		case "p":
+			parsedParallelism = number
+		}
+	}
+	if parsedMemory == 0 || parsedMemory > 256*1024 || parsedIterations == 0 || parsedIterations > 10 || parsedParallelism == 0 || parsedParallelism > 8 {
+		return false
+	}
+	salt, err := base64.RawStdEncoding.DecodeString(parts[4])
+	if err != nil || len(salt) < 8 {
+		return false
+	}
+	expected, err := base64.RawStdEncoding.DecodeString(parts[5])
+	if err != nil || len(expected) < 16 {
+		return false
+	}
+	actual := argon2.IDKey([]byte(value), salt, uint32(parsedIterations), uint32(parsedMemory), uint8(parsedParallelism), uint32(len(expected)))
+	return subtle.ConstantTimeCompare(actual, expected) == 1
+}