module-transaction: Add GetUser() method that prompts an user if non-set

We can now finally test this properly both using a mock and through the
interactive module that will do the request for us in various conditions.

cmd/pam-moduler/tests/integration-tester-module/communication_test.go

@@ -29,7 +29,7 @@ func ensureError(t *testing.T, err error, expected error) {
 func ensureEqual(t *testing.T, a any, b any) {
 	t.Helper()
 	if !reflect.DeepEqual(a, b) {
-		t.Fatalf("values mismatch %v vs %v", a, b)
+		t.Fatalf("values mismatch %#v vs %#v", a, b)
 	}
 }
 

cmd/pam-moduler/tests/integration-tester-module/integration-tester-module_test.go

@@ -54,7 +54,8 @@ func (cr *checkedRequest) check(res *Result) error {
 	return cr.r.check(res, cr.exp)
 }
 
-func ensureItem(tx *pam.Transaction, item pam.Item, expected string) error {
+func ensureUser(tx *pam.Transaction, expected string) error {
+	item := pam.User
 	if value, err := tx.GetItem(item); err != nil {
 		return err
 	} else if value != expected {
@@ -152,7 +153,7 @@ func Test_Moduler_IntegrationTesterModule(t *testing.T) {
 					exp: []interface{}{"an-user", nil},
 				}},
 			finish: func(tx *pam.Transaction, l *Listener, ts testState) error {
-				return ensureItem(tx, pam.User, "an-user")
+				return ensureUser(tx, "an-user")
 			},
 		},
 		"set-item-User-preset": {
@@ -167,7 +168,7 @@ func Test_Moduler_IntegrationTesterModule(t *testing.T) {
 					exp: []interface{}{"an-user", nil},
 				}},
 			finish: func(tx *pam.Transaction, l *Listener, ts testState) error {
-				return ensureItem(tx, pam.User, "an-user")
+				return ensureUser(tx, "an-user")
 			},
 		},
 		"set-get-item-User-empty": {
@@ -488,6 +489,59 @@ func Test_Moduler_IntegrationTesterModule(t *testing.T) {
 				return nil
 			},
 		},
+		"get-user-empty-no-conv-set": {
+			expectedError: pam.ErrConv,
+			checkedRequests: []checkedRequest{{
+				r:   NewRequest("GetUser", "who are you? "),
+				exp: []interface{}{"", pam.ErrConv},
+			}},
+			finish: func(tx *pam.Transaction, l *Listener, ts testState) error {
+				return ensureUser(tx, "")
+			},
+		},
+		"get-user-empty-with-conv": {
+			credentials: utils.Credentials{
+				User:            "replying-user",
+				ExpectedMessage: "who are you? ",
+				ExpectedStyle:   pam.PromptEchoOn,
+			},
+			checkedRequests: []checkedRequest{{
+				r:   NewRequest("GetUser", "who are you? "),
+				exp: []interface{}{"replying-user", nil},
+			}},
+			finish: func(tx *pam.Transaction, l *Listener, ts testState) error {
+				return ensureUser(tx, "replying-user")
+			},
+		},
+		"get-user-preset-without-conv": {
+			setup: func(tx *pam.Transaction, l *Listener, ts testState) error {
+				return tx.SetItem(pam.User, "setup-user")
+			},
+			checkedRequests: []checkedRequest{{
+				r:   NewRequest("GetUser", "who are you? "),
+				exp: []interface{}{"setup-user", nil},
+			}},
+			finish: func(tx *pam.Transaction, l *Listener, ts testState) error {
+				return ensureUser(tx, "setup-user")
+			},
+		},
+		"get-user-preset-with-conv": {
+			credentials: utils.Credentials{
+				User:            "replying-user",
+				ExpectedMessage: "No message should have been shown!",
+				ExpectedStyle:   pam.PromptEchoOn,
+			},
+			setup: func(tx *pam.Transaction, l *Listener, ts testState) error {
+				return tx.SetItem(pam.User, "setup-user")
+			},
+			checkedRequests: []checkedRequest{{
+				r:   NewRequest("GetUser", "who are you? "),
+				exp: []interface{}{"setup-user", nil},
+			}},
+			finish: func(tx *pam.Transaction, l *Listener, ts testState) error {
+				return ensureUser(tx, "setup-user")
+			},
+		},
 	}
 
 	for name, tc := range tests {

cmd/pam-moduler/tests/internal/utils/test-utils.go

@@ -1,6 +1,13 @@
 // Package utils contains the internal test utils
 package utils
 
+import (
+	"errors"
+	"fmt"
+
+	"github.com/msteinert/pam/v2"
+)
+
 // Action represents a PAM action to perform.
 type Action int
 
@@ -106,3 +113,43 @@ type SerializableError struct {
 func (e *SerializableError) Error() string {
 	return e.Msg
 }
+
+// Credentials is a test [pam.ConversationHandler] implementation.
+type Credentials struct {
+	User              string
+	Password          string
+	ExpectedMessage   string
+	CheckEmptyMessage bool
+	ExpectedStyle     pam.Style
+	CheckZeroStyle    bool
+	Context           interface{}
+}
+
+// RespondPAM handles PAM string conversations.
+func (c Credentials) RespondPAM(s pam.Style, msg string) (string, error) {
+	if (c.ExpectedMessage != "" || c.CheckEmptyMessage) &&
+		msg != c.ExpectedMessage {
+		return "", errors.Join(pam.ErrConv,
+			&SerializableError{
+				fmt.Sprintf("unexpected prompt: %s vs %s", msg, c.ExpectedMessage),
+			})
+	}
+
+	if (c.ExpectedStyle != 0 || c.CheckZeroStyle) &&
+		s != c.ExpectedStyle {
+		return "", errors.Join(pam.ErrConv,
+			&SerializableError{
+				fmt.Sprintf("unexpected style: %#v vs %#v", s, c.ExpectedStyle),
+			})
+	}
+
+	switch s {
+	case pam.PromptEchoOn:
+		return c.User, nil
+	case pam.PromptEchoOff:
+		return c.Password, nil
+	}
+
+	return "", errors.Join(pam.ErrConv,
+		&SerializableError{fmt.Sprintf("unhandled style: %v", s)})
+}