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Diffstat (limited to 'lib/libc/string/strcat.3')
| -rw-r--r-- | lib/libc/string/strcat.3 | 159 |
1 files changed, 159 insertions, 0 deletions
diff --git a/lib/libc/string/strcat.3 b/lib/libc/string/strcat.3 new file mode 100644 index 0000000..298c865 --- /dev/null +++ b/lib/libc/string/strcat.3 @@ -0,0 +1,159 @@ +.\" 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 +.Sh STANDARDS +The +.Fn strcat +and +.Fn strncat +functions +conform to +.St -isoC . |
