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.\" $NetBSD: ssp.3,v 1.9 2015/12/03 13:11:45 christos Exp $
.\"
.\" SPDX-License-Identifier: BSD-2-Clause
.\"
.\" Copyright (c) 2007 The NetBSD Foundation, Inc.
.\" All rights reserved.
.\"
.\" This code is derived from software contributed to The NetBSD Foundation
.\" by Christos Zoulas.
.\"
.\" 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.
.\"
.\" THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. 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 FOUNDATION 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.
.\"
.\"
.Dd December 3, 2015
.Dt SSP 3
.Os
.Sh NAME
.Nm ssp
.Nd bounds checked libc functions
.Sh LIBRARY
.Lb libssp
.Sh SYNOPSIS
.In ssp/stdio.h
.Ft int
.Fn sprintf "char *str" "const char *fmt" "..."
.Ft int
.Fn vsprintf "char *str" "const char *fmt" "va_list ap"
.Ft int
.Fn snprintf "char *str" "size_t len" "const char *fmt" "..."
.Ft int
.Fn vsnprintf "char *str" "size_t len" "const char *fmt" "va_list ap"
.Ft char *
.Fn fgets "char *str" "int len" "FILE *fp"
.In ssp/string.h
.Ft void *
.Fn memcpy "void *str" "const void *ptr" "size_t len"
.Ft void *
.Fn memmove "void *str" "const void *ptr" "size_t len"
.Ft void *
.Fn memset "void *str" "int val" "size_t len"
.Ft char *
.Fn stpcpy "char *str" "const char *ptr"
.Ft char *
.Fn strcpy "char *str" "const char *ptr"
.Ft char *
.Fn strcat "char *str" "const char *ptr"
.Ft char *
.Fn strncpy "char *str" "const char *ptr" "size_t len"
.Ft char *
.Fn strncat "char *str" "const char *ptr" "size_t len"
.In ssp/strings.h
.Ft void *
.Fn bcopy "const void *ptr" "void *str" "size_t len"
.Ft void *
.Fn bzero "void *str" "size_t len"
.In ssp/unistd.h
.Ft ssize_t
.Fn read "int fd" "void *str" "size_t len"
.Ft int
.Fn readlink "const char * restrict path" "char * restrict str" "size_t len"
.Ft int
.Fn getcwd "char *str" "size_t len"
.Sh DESCRIPTION
When
.Dv _FORTIFY_SOURCE
bounds checking is enabled as described below, the above functions get
overwritten to use the
.Xr __builtin_object_size 3
function to compute the size of
.Fa str ,
if known at compile time,
and perform bounds check on it in order
to avoid data buffer or stack buffer overflows.
If an overflow is detected, the routines will call
.Xr abort 3 .
.Pp
To enable these function overrides the following should be added to the
.Xr clang 1
or
.Xr gcc 1
command line:
.Dq \-D_FORTIFY_SOURCE=1
or
.Dq \-D_FORTIFY_SOURCE=2 .
.Pp
If
.Dv _FORTIFY_SOURCE is set to
.Dv 1
the code will compute the maximum possible buffer size for
.Fa str ,
and if set to
.Dv 2
it will compute the minimum buffer size.
.Sh SEE ALSO
.Xr clang 1 ,
.Xr gcc 1 ,
.Xr __builtin_object_size 3 ,
.Xr stdio 3 ,
.Xr string 3 ,
.Xr security 7
.Sh HISTORY
The
.Nm
library appeared in
.Nx 4.0 .
This version of the
.Nm
library replaced the GNU library of the same name in
.Fx 12.2 .
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