/* -*- mode: c; c-basic-offset: 4; indent-tabs-mode: nil -*- */

/* include/k5-tls.h - internal pluggable interface for TLS */

/*

 * Copyright (C) 2014 by the Massachusetts Institute of Technology.

 * All rights reserved.

 *

 * Redistribution and use in source and binary forms, with or without

 * modification, are permitted provided that the following conditions

 * are met:

 *

 * * Redistributions of source code must retain the above copyright

 *   notice, this list of conditions and the following disclaimer.

 *

 * * Redistributions in binary form must reproduce the above copyright

 *   notice, this list of conditions and the following disclaimer in

 *   the documentation and/or other materials provided with the

 *   distribution.

 *

 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS

 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT

 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS

 * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE

 * COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT,

 * INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES

 * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR

 * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)

 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,

 * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)

 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED

 * OF THE POSSIBILITY OF SUCH DAMAGE.

 */

/*

 * This internal pluggable interface allows libkrb5 to load an in-tree module

 * providing TLS support at runtime.  It is currently tailored for the needs of

 * the OpenSSL module as used for HTTP proxy support.  As an internal

 * interface, it can be changed to fit different implementations and consumers

 * without regard for backward compatibility.

 */

#ifndef K5_TLS_H

#define K5_TLS_H

#include "k5-int.h"

/* An abstract type for localauth module data. */

typedef struct k5_tls_handle_st *k5_tls_handle;

typedef enum {

    DATA_READ, DONE, WANT_READ, WANT_WRITE, ERROR_TLS

} k5_tls_status;

/*

 * Create a handle for fd, where the server certificate must match servername

 * and be trusted according to anchors.  anchors is a null-terminated list

 * using the DIR:/FILE:/ENV: syntax borrowed from PKINIT.  If anchors is null,

 * use the system default trust anchors.

 */

typedef krb5_error_code

(*k5_tls_setup_fn)(krb5_context context, SOCKET fd, const char *servername,

                   char **anchors, k5_tls_handle *handle_out);

/*

 * Write len bytes of data using TLS.  Return DONE if writing is complete,

 * WANT_READ or WANT_WRITE if the underlying socket must be readable or

 * writable to continue, and ERROR_TLS if the TLS channel or underlying socket

 * experienced an error.  After WANT_READ or WANT_WRITE, the operation will be

 * retried with the same arguments even if some data has already been written.

 * (OpenSSL makes this contract easy to fulfill.  For other implementations we

 * might want to change it.)

 */

typedef k5_tls_status

(*k5_tls_write_fn)(krb5_context context, k5_tls_handle handle,

                   const void *data, size_t len);

/*

 * Read up to data_size bytes of data using TLS.  Return DATA_READ and set

 * *len_out if any data is read.  Return DONE if there is no more data to be

 * read on the connection, WANT_READ or WANT_WRITE if the underlying socket

 * must be readable or writable to continue, and ERROR_TLS if the TLS channel

 * or underlying socket experienced an error.

 *

 * After DATA_READ, there may still be pending buffered data to read.  The

 * caller must call this method again with additional buffer space before

 * selecting for reading on the underlying socket.

 */

typedef k5_tls_status

(*k5_tls_read_fn)(krb5_context context, k5_tls_handle handle, void *data,

                  size_t data_size, size_t *len_out);

/* Release a handle.  Do not pass a null pointer. */

typedef void

(*k5_tls_free_handle_fn)(krb5_context context, k5_tls_handle handle);

/* All functions are mandatory unless they are all null, in which case the

 * caller should assume that TLS is unsupported. */

typedef struct k5_tls_vtable_st {

    k5_tls_setup_fn setup;

    k5_tls_write_fn write;

    k5_tls_read_fn read;

    k5_tls_free_handle_fn free_handle;

} *k5_tls_vtable;

#endif /* K5_TLS_H */