mirror of
https://git.FreeBSD.org/src.git
synced 2024-12-23 11:18:54 +00:00
165 lines
4.4 KiB
Groff
165 lines
4.4 KiB
Groff
.\" Copyright (c) 1990, 1991, 1993
|
|
.\" The Regents of the University of California. All rights reserved.
|
|
.\"
|
|
.\" This code is derived from software contributed to Berkeley by
|
|
.\" Chris Torek and the American National Standards Committee X3,
|
|
.\" on Information Processing Systems.
|
|
.\"
|
|
.\" 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 acknowledgement:
|
|
.\" This product includes software developed by the University of
|
|
.\" California, Berkeley and its contributors.
|
|
.\" 4. Neither the name of the University nor the names of its contributors
|
|
.\" may be used to endorse or promote products derived from this software
|
|
.\" without specific prior written permission.
|
|
.\"
|
|
.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS 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 REGENTS 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.
|
|
.\"
|
|
.\" @(#)strcat.3 8.1 (Berkeley) 6/4/93
|
|
.\" $FreeBSD$
|
|
.\"
|
|
.Dd June 4, 1993
|
|
.Dt STRCAT 3
|
|
.Os
|
|
.Sh NAME
|
|
.Nm strcat
|
|
.Nd concatenate strings
|
|
.Sh LIBRARY
|
|
.Lb libc
|
|
.Sh SYNOPSIS
|
|
.In string.h
|
|
.Ft char *
|
|
.Fn strcat "char * restrict s" "const char * restrict append"
|
|
.Ft char *
|
|
.Fn strncat "char * restrict s" "const char * restrict append" "size_t count"
|
|
.Sh DESCRIPTION
|
|
The
|
|
.Fn strcat
|
|
and
|
|
.Fn strncat
|
|
functions
|
|
append a copy of the null-terminated string
|
|
.Fa append
|
|
to the end of the null-terminated string
|
|
.Fa s ,
|
|
then add a terminating
|
|
.Ql \e0 .
|
|
The string
|
|
.Fa s
|
|
must have sufficient space to hold the result.
|
|
.Pp
|
|
The
|
|
.Fn strncat
|
|
function
|
|
appends not more than
|
|
.Fa count
|
|
characters from
|
|
.Fa append ,
|
|
and then adds a terminating
|
|
.Ql \e0 .
|
|
.Sh RETURN VALUES
|
|
The
|
|
.Fn strcat
|
|
and
|
|
.Fn strncat
|
|
functions
|
|
return the pointer
|
|
.Fa s .
|
|
.Sh SECURITY CONSIDERATIONS
|
|
The
|
|
.Fn strcat
|
|
function is easily misused in a manner
|
|
which enables malicious users to arbitrarily change
|
|
a running program's functionality through a buffer overflow attack.
|
|
(See
|
|
the FSA.)
|
|
.Pp
|
|
Avoid using
|
|
.Fn strcat .
|
|
Instead, use
|
|
.Fn strncat
|
|
or
|
|
.Fn strlcat
|
|
and ensure that no more characters are copied to the destination buffer
|
|
than it can hold.
|
|
.Pp
|
|
Note that
|
|
.Fn strncat
|
|
can also be problematic.
|
|
It may be a security concern for a string to be truncated at all.
|
|
Since the truncated string will not be as long as the original,
|
|
it may refer to a completely different resource
|
|
and usage of the truncated resource
|
|
could result in very incorrect behavior.
|
|
Example:
|
|
.Bd -literal
|
|
void
|
|
foo(const char *arbitrary_string)
|
|
{
|
|
char onstack[8];
|
|
|
|
#if defined(BAD)
|
|
/*
|
|
* This first strcat is bad behavior. Do not use strcat!
|
|
*/
|
|
(void)strcat(onstack, arbitrary_string); /* BAD! */
|
|
#elif defined(BETTER)
|
|
/*
|
|
* The following two lines demonstrate better use of
|
|
* strncat().
|
|
*/
|
|
(void)strncat(onstack, arbitrary_string,
|
|
sizeof(onstack) - strlen(onstack) - 1);
|
|
#elif defined(BEST)
|
|
/*
|
|
* These lines are even more robust due to testing for
|
|
* truncation.
|
|
*/
|
|
if (strlen(arbitrary_string) + 1 >
|
|
sizeof(onstack) - strlen(onstack))
|
|
err(1, "onstack would be truncated");
|
|
(void)strncat(onstack, arbitrary_string,
|
|
sizeof(onstack) - strlen(onstack) - 1);
|
|
#endif
|
|
}
|
|
.Ed
|
|
.Sh SEE ALSO
|
|
.Xr bcopy 3 ,
|
|
.Xr memccpy 3 ,
|
|
.Xr memcpy 3 ,
|
|
.Xr memmove 3 ,
|
|
.Xr strcpy 3 ,
|
|
.Xr strlcat 3 ,
|
|
.Xr strlcpy 3
|
|
.Rs
|
|
.%T "The FreeBSD Security Architecture"
|
|
.Re
|
|
(See
|
|
.Pa "/usr/share/doc/{to be decided}" . )
|
|
.Sh STANDARDS
|
|
The
|
|
.Fn strcat
|
|
and
|
|
.Fn strncat
|
|
functions
|
|
conform to
|
|
.St -isoC .
|