fix cookie -- not working

internal/prestashop/config/config.go

@@ -140,15 +140,15 @@ func (c Config) DeriveCookieName(host string) string {
 		return c.PrestaShopCookieName
 	}
 
-	domain := normalizedCookieDomain(host)
+	domain := fallbackCookieHashDomain(host)
 	if domain == "" {
-		domain = normalizedCookieDomain(c.PrestaShopBaseURL)
+		domain = fallbackCookieHashDomain(c.PrestaShopBaseURL)
 	}
 	if domain == "" {
-		domain = normalizedCookieDomain(c.PrestaShopProxyTarget)
+		domain = fallbackCookieHashDomain(c.PrestaShopProxyTarget)
 	}
 
-	sum := md5.Sum([]byte(c.PrestaShopVersion + "PrestaShop" + domain))
+	sum := md5.Sum([]byte(c.PrestaShopVersion + "ps-s1" + domain))
 	return fmt.Sprintf("PrestaShop-%x", sum)
 }
 
@@ -256,6 +256,17 @@ func normalizedCookieDomain(input string) string {
 	return value
 }
 
+func fallbackCookieHashDomain(input string) string {
+	value := normalizedCookieDomain(input)
+	if value == "" {
+		return ""
+	}
+	if net.ParseIP(value) != nil || !strings.Contains(value, ".") {
+		return ""
+	}
+	return value
+}
+
 func dbDSNFromEnv() string {
 	return mysqlDSN(
 		firstNonEmpty(os.Getenv("PRESTASHOP_DB_HOST"), os.Getenv("DB_HOST")),

internal/prestashop/config/config_test.go

@@ -0,0 +1,19 @@
+package config
+
+import (
+	"crypto/md5"
+	"fmt"
+	"testing"
+)
+
+func TestDeriveCookieNameMatchesFallbackPrestashopRule(t *testing.T) {
+	cfg := Config{PrestaShopVersion: "1.7.3"}
+
+	got := cfg.DeriveCookieName("localhost")
+	sum := md5.Sum([]byte("1.7.3" + "ps-s1"))
+	want := fmt.Sprintf("PrestaShop-%x", sum)
+
+	if got != want {
+		t.Fatalf("DeriveCookieName() = %q, want %q", got, want)
+	}
+}