A good use of the UI interface is as a password callback replacement

(for new functions...).  One might still want to be able to pass down
a user-data pointer to be used by the UI.  However, ex_data doesn't
quite cut it, since that means the appropriate index to it might need
to be shared between parts that aren't really related in that sense,
and would require the currently hidden (static) index holders to be
uncovered.  Not a good thing.  Therefore, add the possibility to add a
user-data pointer to a UI.

crypto/ui/ui.h

@@ -129,6 +129,19 @@ int UI_dup_info_string(UI *ui, const char *text);
 int UI_add_error_string(UI *ui, const char *text);
 int UI_dup_error_string(UI *ui, const char *text);
 
+/* The following function is used to store a pointer to user-specific data.
+   Any previous such pointer will be returned and replaced.
+
+   For callback purposes, this function makes a lot more sense than using
+   ex_data, since the latter requires that different parts of OpenSSL or
+   applications share the same ex_data index.
+
+   Note that the UI_OpenSSL() method completely ignores the user data.
+   Other methods may not, however.  */
+void *UI_add_user_data(UI *ui, void *user_data);
+/* We need a user data retrieving function as well.  */
+void *UI_get0_user_data(UI *ui);
+
 /* Return the result associated with a prompt given with the index i. */
 const char *UI_get0_result(UI *ui, int i);
 

crypto/ui/ui_lib.c

@@ -256,6 +256,18 @@ int UI_dup_error_string(UI *ui, const char *text)
 		NULL);
 	}
 
+void *UI_add_user_data(UI *ui, void *user_data)
+	{
+	void *old_data = ui->user_data;
+	ui->user_data = user_data;
+	return old_data;
+	}
+
+void *UI_get0_user_data(UI *ui)
+	{
+	return ui->user_data;
+	}
+
 const char *UI_get0_result(UI *ui, int i)
 	{
 	if (i < 0)

crypto/ui/ui_locl.h

@@ -104,6 +104,7 @@ struct ui_st
 	STACK_OF(UI_STRING) *strings; /* We might want to prompt for more
 					 than one thing at a time, and
 					 with different echoing status.  */
+	void *user_data;
 	CRYPTO_EX_DATA ex_data;
 	};