.\" $OpenBSD: BIO_new.3,v 1.20 2021/03/12 07:05:35 jmc Exp $ .\" full merge up to: .\" OpenSSL man3/BIO_new.pod fb46be03 Feb 26 11:51:31 2016 +0000 .\" OpenSSL man7/bio.pod 631c37be Dec 12 16:56:50 2017 +0100 .\" partial merge up to: .\" OpenSSL man3/BIO_new.pod e9b77246 Jan 20 19:58:49 2017 +0100 .\" .\" This file was written by Dr. Stephen Henson . .\" Copyright (c) 2000, 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. 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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; .\" 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. .\" .Dd $Mdocdate: March 12 2021 $ .Dt BIO_NEW 3 .Os .Sh NAME .Nm BIO_new , .Nm BIO_up_ref , .Nm BIO_set , .Nm BIO_free , .Nm BIO_vfree , .Nm BIO_free_all .Nd construct and destruct I/O abstraction objects .Sh SYNOPSIS .In openssl/bio.h .Ft BIO * .Fo BIO_new .Fa "const BIO_METHOD *type" .Fc .Ft int .Fo BIO_up_ref .Fa "BIO *a" .Fc .Ft int .Fo BIO_set .Fa "BIO *a" .Fa "const BIO_METHOD *type" .Fc .Ft int .Fo BIO_free .Fa "BIO *a" .Fc .Ft void .Fo BIO_vfree .Fa "BIO *a" .Fc .Ft void .Fo BIO_free_all .Fa "BIO *a" .Fc .Sh DESCRIPTION A .Vt BIO is an I/O abstraction object, hiding many of the underlying I/O details from an application. If an application uses BIOs for its I/O, it can transparently handle SSL connections, unencrypted network connections, and file I/O. .Pp The .Fn BIO_new function constructs a new .Vt BIO using the method .Fa type and sets its reference count to 1. There are two groups of BIO types, source/sink BIOs and filter BIOs. .Pp Source/sink BIOs provide input or consume output. Examples include socket BIOs and file BIOs. .Pp Filter BIOs take data from one BIO and pass it through to another, or to the application, forming a chain of BIOs. The data may be left unmodified (for example by a message digest BIO) or translated (for example by an encryption BIO). The effect of a filter BIO may change according to the I/O operation it is performing: for example an encryption BIO encrypts data if it is written to and decrypts data if it is read from. .Pp Some BIOs (such as memory BIOs) can be used immediately after calling .Fn BIO_new . Others (such as file BIOs) need some additional initialization, and utility functions exists to construct and initialize such BIOs. .Pp Normally the .Fa type argument is supplied by a function which returns a pointer to a .Vt BIO_METHOD . There is a naming convention for such functions: the methods for source/sink BIOs are called .Fn BIO_s_* and those for filter BIOs .Fn BIO_f_* . .Pp .Fn BIO_up_ref increments the reference count of .Fa a by 1. .Pp .Fn BIO_set is a deprecated function to initialize an unused .Vt BIO structure located in static memory or on the stack, to set its method to .Fa type , and to set its reference count to 1. It must not be called on .Vt BIO objects created with .Fn BIO_new , nor on objects that were already used. .Pp .Fn BIO_free and .Fn BIO_vfree decrement the reference count of .Fa a by 1, and if the reference count reaches 0, they destruct the single .Vt BIO .Fa a , which may also have some effect on the underlying I/O structure, for example it may close the file being referred to under certain circumstances. If .Fa a is a .Dv NULL pointer, no action occurs. If .Fn BIO_free is called on a BIO chain, it destructs at most one BIO, resulting in a memory leak. .Pp .Fn BIO_free_all calls .Fn BIO_free on .Fa a and on all following .Vt BIO objects in the chain. As soon as the reference count of a .Vt BIO is still non-zero after calling .Fn BIO_free on it, the function .Fn BIO_free_all returns right away and refrains from freeing the remaining .Vt BIO objects in the chain. It does not halt if an error occurs destructing an individual BIO in the chain. If .Fa a is a .Dv NULL pointer, no action occurs. Calling .Fn BIO_free_all on a single BIO has the same effect as .Fn BIO_vfree . .Pp Common I/O functions are documented in .Xr BIO_read 3 . Forming chains is explained in .Xr BIO_push 3 ; inspecting them is explained in .Xr BIO_find_type 3 . For more details about the different kinds of BIOs, see the individual .Vt BIO_METHOD manual pages. .Sh RETURN VALUES .Fn BIO_new returns a newly constructed .Vt BIO object or .Dv NULL on failure. .Pp .Fn BIO_up_ref , .Fn BIO_set , and .Fn BIO_free return 1 for success or 0 for failure. .Sh EXAMPLES Create a memory BIO: .Pp .Dl BIO *mem = BIO_new(BIO_s_mem()); .Sh SEE ALSO .Xr BIO_ctrl 3 , .Xr BIO_f_base64 3 , .Xr BIO_f_buffer 3 , .Xr BIO_f_cipher 3 , .Xr BIO_f_md 3 , .Xr BIO_f_null 3 , .Xr BIO_f_ssl 3 , .Xr BIO_find_type 3 , .Xr BIO_get_ex_new_index 3 , .Xr BIO_meth_new 3 , .Xr BIO_new_CMS 3 , .Xr BIO_printf 3 , .Xr BIO_push 3 , .Xr BIO_read 3 , .Xr BIO_s_accept 3 , .Xr BIO_s_bio 3 , .Xr BIO_s_connect 3 , .Xr BIO_s_fd 3 , .Xr BIO_s_file 3 , .Xr BIO_s_mem 3 , .Xr BIO_s_null 3 , .Xr BIO_s_socket 3 , .Xr BIO_set_callback 3 , .Xr BIO_set_data 3 , .Xr BIO_should_retry 3 , .Xr BUF_MEM_new 3 , .Xr crypto 3 .Sh HISTORY .Fn BIO_new , .Fn BIO_set , and .Fn BIO_free first appeared in SSLeay 0.6.0. .Fn BIO_free_all first appeared in SSLeay 0.6.6. All these functions have been available since .Ox 2.4 . .Pp .Fn BIO_vfree first appeared in OpenSSL 0.9.6 and has been available since .Ox 2.9 . .Pp .Fn BIO_up_ref first appeared in OpenSSL 1.1.0 and has been available since .Ox 6.3 .