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.\" $OpenBSD: BIO_f_cipher.3,v 1.10 2018/05/02 16:04:35 schwarze Exp $
.\" OpenSSL 186bb907 Apr 13 11:05:13 2015 -0700
.\"
.\" This file was written by Dr. Stephen Henson <steve@openssl.org>.
.\" Copyright (c) 2000, 2003, 2015, 2016 The OpenSSL Project.
.\" All rights reserved.
.\"
.\" Redistribution and use in source and binary forms, with or without
.\" modification, are permitted provided that the following conditions
.\" are met:
.\"
.\" 1. Redistributions of source code must retain the above copyright
.\" notice, this list of conditions and the following disclaimer.
.\"
.\" 2. 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.
.\"
.\" 3. All advertising materials mentioning features or use of this
.\" software must display the following acknowledgment:
.\" "This product includes software developed by the OpenSSL Project
.\" for use in the OpenSSL Toolkit. (http://www.openssl.org/)"
.\"
.\" 4. The names "OpenSSL Toolkit" and "OpenSSL Project" must not be used to
.\" endorse or promote products derived from this software without
.\" prior written permission. For written permission, please contact
.\" openssl-core@openssl.org.
.\"
.\" 5. Products derived from this software may not be called "OpenSSL"
.\" nor may "OpenSSL" appear in their names without prior written
.\" permission of the OpenSSL Project.
.\"
.\" 6. Redistributions of any form whatsoever must retain the following
.\" acknowledgment:
.\" "This product includes software developed by the OpenSSL Project
.\" for use in the OpenSSL Toolkit (http://www.openssl.org/)"
.\"
.\" THIS SOFTWARE IS PROVIDED BY THE OpenSSL PROJECT ``AS IS'' AND ANY
.\" EXPRESSED 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 OpenSSL PROJECT OR
.\" ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
.\" SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
.\" NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
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.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
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.\" ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
.\" OF THE POSSIBILITY OF SUCH DAMAGE.
.\"
.Dd $Mdocdate: May 2 2018 $
.Dt BIO_F_CIPHER 3
.Os
.Sh NAME
.Nm BIO_f_cipher ,
.Nm BIO_set_cipher ,
.Nm BIO_get_cipher_status ,
.Nm BIO_get_cipher_ctx
.Nd cipher BIO filter
.Sh SYNOPSIS
.In openssl/bio.h
.In openssl/evp.h
.Ft const BIO_METHOD *
.Fo BIO_f_cipher
.Fa void
.Fc
.Ft void
.Fo BIO_set_cipher
.Fa "BIO *b"
.Fa "const EVP_CIPHER *cipher"
.Fa "unsigned char *key"
.Fa "unsigned char *iv"
.Fa "int enc"
.Fc
.Ft int
.Fo BIO_get_cipher_status
.Fa "BIO *b"
.Fc
.Ft int
.Fo BIO_get_cipher_ctx
.Fa "BIO *b"
.Fa "EVP_CIPHER_CTX **pctx"
.Fc
.Sh DESCRIPTION
.Fn BIO_f_cipher
returns the cipher BIO method.
This is a filter BIO that encrypts any data written through it,
and decrypts any data read from it.
It is a BIO wrapper for the cipher routines
.Xr EVP_CipherInit 3 ,
.Xr EVP_CipherUpdate 3 ,
and
.Xr EVP_CipherFinal 3 .
.Pp
Cipher BIOs do not support
.Xr BIO_gets 3
or
.Xr BIO_puts 3 .
.Pp
.Xr BIO_flush 3
on an encryption BIO that is being written through
is used to signal that no more data is to be encrypted:
this is used to flush and possibly pad the final block through the BIO.
.Pp
.Fn BIO_set_cipher
sets the cipher of BIO
.Fa b
to
.Fa cipher
using key
.Fa key
and IV
.Fa iv .
.Fa enc
should be set to 1 for encryption and zero for decryption.
.Pp
When reading from an encryption BIO, the final block is automatically
decrypted and checked when EOF is detected.
.Fn BIO_get_cipher_status
is a
.Xr BIO_ctrl 3
macro which can be called to determine
whether the decryption operation was successful.
.Pp
.Fn BIO_get_cipher_ctx
is a
.Xr BIO_ctrl 3
macro which retrieves the internal BIO cipher context.
The retrieved context can be used in conjunction
with the standard cipher routines to set it up.
This is useful when
.Fn BIO_set_cipher
is not flexible enough for the applications needs.
.Pp
When encrypting,
.Xr BIO_flush 3
must be called to flush the final block through the BIO.
If it is not, then the final block will fail a subsequent decrypt.
.Pp
When decrypting, an error on the final block is signalled
by a zero return value from the read operation.
A successful decrypt followed by EOF
will also return zero for the final read.
.Fn BIO_get_cipher_status
should be called to determine if the decrypt was successful.
.Pp
As always, if
.Xr BIO_gets 3
or
.Xr BIO_puts 3
support is needed, then it can be achieved
by preceding the cipher BIO with a buffering BIO.
.Sh RETURN VALUES
.Fn BIO_f_cipher
returns the cipher BIO method.
.Pp
.Fn BIO_get_cipher_status
returns 1 for a successful decrypt and 0 for failure.
.Pp
.Fn BIO_get_cipher_ctx
currently always returns 1.
.Sh SEE ALSO
.Xr BIO_new 3
.Sh HISTORY
.Fn BIO_f_cipher ,
.Fn BIO_set_cipher ,
and
.Fn BIO_get_cipher_status
first appeared in SSLeay 0.6.5 and have been available since
.Ox 2.4 .
.Pp
.Fn BIO_get_cipher_ctx
first appeared in SSLeay 0.9.1 and has been available since
.Ox 2.6 .
|
