pam/integration-tests/exec: Use a file to pass very long arguments

pam/integration-tests/cmd/exec-client/client.go

@@ -11,6 +11,7 @@ import (
 	"os"
 	"reflect"
 	"regexp"
+	"strings"
 
 	"github.com/godbus/dbus/v5"
 	"github.com/msteinert/pam/v2"
@@ -23,6 +24,7 @@ var (
 	pamFlags      = flag.Int64("flags", 0, "pam flags")
 	serverAddress = flag.String("server-address", "", "the dbus connection address to use to communicate with module")
 	logFile       = flag.String("client-log", "", "the file where to save logs")
+	argsFile      = flag.String("client-args-file", "", "the file where arguments are saved")
 )
 
 func main() {
@@ -78,6 +80,15 @@ func mainFunc() error {
 		log.SetOutput(f)
 	}
 
+	if argsFile != nil && *argsFile != "" {
+		log.Debug(context.TODO(), "Reading arguments from %s", *argsFile)
+		ca, err := os.ReadFile(*argsFile)
+		if err != nil {
+			return err
+		}
+		args = append(args, strings.Split(string(ca), "\t")...)
+	}
+
 	actionFlags := pam.Flags(0)
 	if pamFlags != nil {
 		actionFlags = pam.Flags(*pamFlags)

pam/integration-tests/exec_test.go

@@ -850,6 +850,17 @@ func getModuleArgs(t *testing.T, clientPath string, args []string) []string {
 	if clientPath != "" {
 		moduleArgs = append(moduleArgs, "--", clientPath)
 		moduleArgs = append(moduleArgs, "-client-log", logFile)
+
+		if len(strings.Join(append(moduleArgs, args...), " ")) > 768 {
+			// FIXME: If the number of arguments is too big, we may break old PAM.
+			// This is not required anymore when we can use libpam 1.6.0 in CI:
+			// https://github.com/linux-pam/linux-pam/pull/658
+			clientArgsPath := filepath.Join(t.TempDir(), "client-args-file")
+			require.NoError(t, os.WriteFile(clientArgsPath, []byte(strings.Join(args, "\t")), 0600),
+				"Setup: Creation of client args file failed")
+			saveArtifactsForDebugOnCleanup(t, []string{clientArgsPath})
+			return append(moduleArgs, "-client-args-file", clientArgsPath)
+		}
 	}
 	return append(moduleArgs, args...)
 }