=pod

=head1 NAME

UI,

UI_new, UI_new_method, UI_free, UI_add_input_string, UI_dup_input_string,

UI_add_verify_string, UI_dup_verify_string, UI_add_input_boolean,

UI_dup_input_boolean, UI_add_info_string, UI_dup_info_string,

UI_add_error_string, UI_dup_error_string, UI_construct_prompt,

UI_add_user_data, UI_dup_user_data, UI_get0_user_data, UI_get0_result,

UI_get_result_length,

UI_process, UI_ctrl, UI_set_default_method, UI_get_default_method,

UI_get_method, UI_set_method, UI_OpenSSL, UI_null - user interface

=head1 SYNOPSIS

 #include <openssl/ui.h>

 typedef struct ui_st UI;

 UI *UI_new(void);

 UI *UI_new_method(const UI_METHOD *method);

 void UI_free(UI *ui);

 int UI_add_input_string(UI *ui, const char *prompt, int flags,

                         char *result_buf, int minsize, int maxsize);

 int UI_dup_input_string(UI *ui, const char *prompt, int flags,

                         char *result_buf, int minsize, int maxsize);

 int UI_add_verify_string(UI *ui, const char *prompt, int flags,

                          char *result_buf, int minsize, int maxsize,

                          const char *test_buf);

 int UI_dup_verify_string(UI *ui, const char *prompt, int flags,

                          char *result_buf, int minsize, int maxsize,

                          const char *test_buf);

 int UI_add_input_boolean(UI *ui, const char *prompt, const char *action_desc,

                          const char *ok_chars, const char *cancel_chars,

                          int flags, char *result_buf);

 int UI_dup_input_boolean(UI *ui, const char *prompt, const char *action_desc,

                          const char *ok_chars, const char *cancel_chars,

                          int flags, char *result_buf);

 int UI_add_info_string(UI *ui, const char *text);

 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);

 char *UI_construct_prompt(UI *ui_method,

        const char *object_desc, const char *object_name);

 void *UI_add_user_data(UI *ui, void *user_data);

 int UI_dup_user_data(UI *ui, void *user_data);

 void *UI_get0_user_data(UI *ui);

 const char *UI_get0_result(UI *ui, int i);

 int UI_get_result_length(UI *ui, int i);

 int UI_process(UI *ui);

 int UI_ctrl(UI *ui, int cmd, long i, void *p, void (*f)());

 void UI_set_default_method(const UI_METHOD *meth);

 const UI_METHOD *UI_get_default_method(void);

 const UI_METHOD *UI_get_method(UI *ui);

 const UI_METHOD *UI_set_method(UI *ui, const UI_METHOD *meth);

 UI_METHOD *UI_OpenSSL(void);

 const UI_METHOD *UI_null(void);

=head1 DESCRIPTION

UI stands for User Interface, and is general purpose set of routines to

prompt the user for text-based information.  Through user-written methods

(see L<UI_create_method(3)>), prompting can be done in any way

imaginable, be it plain text prompting, through dialog boxes or from a

cell phone.

All the functions work through a context of the type UI.  This context

contains all the information needed to prompt correctly as well as a

reference to a UI_METHOD, which is an ordered vector of functions that

carry out the actual prompting.

The first thing to do is to create a UI with UI_new() or UI_new_method(),

then add information to it with the UI_add or UI_dup functions.  Also,

user-defined random data can be passed down to the underlying method

through calls to UI_add_user_data() or UI_dup_user_data().  The default

UI method doesn't care about these data, but other methods might.  Finally,

use UI_process() to actually perform the prompting and UI_get0_result()

and UI_get_result_length() to find the result to the prompt and its length.

A UI can contain more than one prompt, which are performed in the given

sequence.  Each prompt gets an index number which is returned by the

UI_add and UI_dup functions, and has to be used to get the corresponding

result with UI_get0_result() and UI_get_result_length().

UI_process() can be called more than once on the same UI, thereby allowing

a UI to have a long lifetime, but can just as well have a short lifetime.

The functions are as follows:

UI_new() creates a new UI using the default UI method.  When done with

this UI, it should be freed using UI_free().

UI_new_method() creates a new UI using the given UI method.  When done with

this UI, it should be freed using UI_free().

UI_OpenSSL() returns the built-in UI method (note: not necessarily the

default one, since the default can be changed.  See further on).  This

method is the most machine/OS dependent part of OpenSSL and normally

generates the most problems when porting.

UI_null() returns a UI method that does nothing.  Its use is to avoid

getting internal defaults for passed UI_METHOD pointers.

UI_free() removes a UI from memory, along with all other pieces of memory

that's connected to it, like duplicated input strings, results and others.

If B<ui> is NULL nothing is done.

UI_add_input_string() and UI_add_verify_string() add a prompt to the UI,

as well as flags and a result buffer and the desired minimum and maximum

sizes of the result, not counting the final NUL character.  The given

information is used to prompt for information, for example a password,

and to verify a password (i.e. having the user enter it twice and check

that the same string was entered twice).  UI_add_verify_string() takes

and extra argument that should be a pointer to the result buffer of the

input string that it's supposed to verify, or verification will fail.

UI_add_input_boolean() adds a prompt to the UI that's supposed to be answered

in a boolean way, with a single character for yes and a different character

for no.  A set of characters that can be used to cancel the prompt is given

as well.  The prompt itself is divided in two, one part being the

descriptive text (given through the I<prompt> argument) and one describing

the possible answers (given through the I<action_desc> argument).

UI_add_info_string() and UI_add_error_string() add strings that are shown at

the same time as the prompt for extra information or to show an error string.

The difference between the two is only conceptual.  With the builtin method,

there's no technical difference between them.  Other methods may make a

difference between them, however.

The flags currently supported are B<UI_INPUT_FLAG_ECHO>, which is relevant for

UI_add_input_string() and will have the users response be echoed (when

prompting for a password, this flag should obviously not be used, and

B<UI_INPUT_FLAG_DEFAULT_PWD>, which means that a default password of some

sort will be used (completely depending on the application and the UI

method).

UI_dup_input_string(), UI_dup_verify_string(), UI_dup_input_boolean(),

UI_dup_info_string() and UI_dup_error_string() are basically the same

as their UI_add counterparts, except that they make their own copies

of all strings.

UI_construct_prompt() is a helper function that can be used to create

a prompt from two pieces of information: an description and a name.

The default constructor (if there is none provided by the method used)

creates a string "Enter I<description> for I<name>:".  With the

description "pass phrase" and the file name "foo.key", that becomes

"Enter pass phrase for foo.key:".  Other methods may create whatever

string and may include encodings that will be processed by the other

method functions.

UI_add_user_data() adds a user data pointer for the method to use at any

time.  The builtin UI method doesn't care about this info.  Note that several

calls to this function doesn't add data, it replaces the previous blob

with the one given as argument.

UI_dup_user_data() duplicates the user data and works as an alternative

to UI_add_user_data() when the user data needs to be preserved for a longer

duration, perhaps even the lifetime of the application.  The UI object takes

ownership of this duplicate and will free it whenever it gets replaced or

the UI is destroyed.  UI_dup_user_data() returns 0 on success, or -1 on memory

allocation failure or if the method doesn't have a duplicator function.

UI_get0_user_data() retrieves the data that has last been given to the

UI with UI_add_user_data() or UI_dup_user_data.

UI_get0_result() returns a pointer to the result buffer associated with

the information indexed by I.

UI_get_result_length() returns the length of the result buffer associated with

the information indexed by I.

UI_process() goes through the information given so far, does all the printing

and prompting and returns the final status, which is -2 on out-of-band events

(Interrupt, Cancel, ...), -1 on error and 0 on success.

UI_ctrl() adds extra control for the application author.  For now, it

understands two commands: B<UI_CTRL_PRINT_ERRORS>, which makes UI_process()

print the OpenSSL error stack as part of processing the UI, and

B<UI_CTRL_IS_REDOABLE>, which returns a flag saying if the used UI can

be used again or not.

UI_set_default_method() changes the default UI method to the one given.

This function is not thread-safe and should not be called at the same time

as other OpenSSL functions.

UI_get_default_method() returns a pointer to the current default UI method.

UI_get_method() returns the UI method associated with a given UI.

UI_set_method() changes the UI method associated with a given UI.

=head1 NOTES

The resulting strings that the built in method UI_OpenSSL() generate

are assumed to be encoded according to the current locale or (for

Windows) code page.

For applications having different demands, these strings need to be

converted appropriately by the caller.

For Windows, if the OPENSSL_WIN32_UTF8 environment variable is set,

the built-in method UI_OpenSSL() will produce UTF-8 encoded strings

instead.

=head1 RETURN VALUES

UI_new() and UI_new_method() return a valid B<UI> structure or NULL if an error

occurred.

UI_add_input_string(), UI_dup_input_string(), UI_add_verify_string(),

UI_dup_verify_string(), UI_add_input_boolean(), UI_dup_input_boolean(),

UI_add_info_string(), UI_dup_info_string(), UI_add_error_string()

and UI_dup_error_string() return a positive number on success or a value which

is less than or equal to 0 otherwise.

UI_construct_prompt() returns a string or NULL if an error occurred.

UI_dup_user_data() returns 0 on success or -1 on error.

UI_get0_result() returns a string or NULL on error.

UI_get_result_length() returns a positive integer or 0 on success; otherwise it

returns -1 on error.

UI_process() returns 0 on success or a negative value on error.

UI_ctrl() returns a mask on success or -1 on error.

UI_get_default_method(), UI_get_method(), UI_OpenSSL(), UI_null() and

UI_set_method() return either a valid B<UI_METHOD> structure or NULL

respectively.

=head1 HISTORY

The UI_dup_user_data() function was added in OpenSSL 1.1.1.

=head1 COPYRIGHT

Copyright 2001-2018 The OpenSSL Project Authors. All Rights Reserved.

Licensed under the OpenSSL license (the "License").  You may not use

this file except in compliance with the License.  You can obtain a copy

in the file LICENSE in the source distribution or at

L<https://www.openssl.org/source/license.html>.

=cut