feat: seed secure demo merchant identity

internal/identity/password.go

@@ -0,0 +1,56 @@
+package identity
+
+import (
+	"crypto/rand"
+	"crypto/subtle"
+	"encoding/base64"
+	"errors"
+	"fmt"
+	"strings"
+
+	"golang.org/x/crypto/argon2"
+)
+
+const (
+	argonMemory      = 64 * 1024
+	argonIterations  = 3
+	argonParallelism = 2
+	argonSaltLength  = 16
+	argonKeyLength   = 32
+)
+
+func HashPassword(password string) (string, error) {
+	if len(password) < 12 {
+		return "", errors.New("identity: password must contain at least 12 characters")
+	}
+	salt := make([]byte, argonSaltLength)
+	if _, err := rand.Read(salt); err != nil {
+		return "", fmt.Errorf("generating password salt: %w", err)
+	}
+	hash := argon2.IDKey([]byte(password), salt, argonIterations, argonMemory, argonParallelism, argonKeyLength)
+	return fmt.Sprintf("$argon2id$v=19$m=%d,t=%d,p=%d$%s$%s", argonMemory, argonIterations,
+		argonParallelism, base64.RawStdEncoding.EncodeToString(salt), base64.RawStdEncoding.EncodeToString(hash)), nil
+}
+
+func VerifyPassword(password, encoded string) bool {
+	parts := strings.Split(encoded, "$")
+	if len(parts) != 6 || parts[1] != "argon2id" || parts[2] != "v=19" {
+		return false
+	}
+	var memory uint32
+	var iterations uint32
+	var parallelism uint8
+	if _, err := fmt.Sscanf(parts[3], "m=%d,t=%d,p=%d", &memory, &iterations, &parallelism); err != nil {
+		return false
+	}
+	salt, err := base64.RawStdEncoding.DecodeString(parts[4])
+	if err != nil {
+		return false
+	}
+	expected, err := base64.RawStdEncoding.DecodeString(parts[5])
+	if err != nil || len(expected) == 0 {
+		return false
+	}
+	actual := argon2.IDKey([]byte(password), salt, iterations, memory, parallelism, uint32(len(expected)))
+	return subtle.ConstantTimeCompare(actual, expected) == 1
+}