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strlcpy() and strlcat() by Todd Miller <Todd.Miller@courtesan.com>, v…

…ia openbsd
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lukem
lukem committed Sep 8, 1999
1 parent a2bca40 commit e44c7d20cffdbc86629af5a381c835f256a41101
Showing with 286 additions and 0 deletions.
  1. +71 −0 lib/libc/string/strlcat.c
  2. +147 −0 lib/libc/string/strlcpy.3
  3. +68 −0 lib/libc/string/strlcpy.c
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+/* $OpenBSD: strlcat.c,v 1.2 1999/06/17 16:28:58 millert Exp $ */
+
+/*
+ * Copyright (c) 1998 Todd C. Miller <Todd.Miller@courtesan.com>
+ * 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. The name of the author may not be used to endorse or promote products
+ * derived from this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED ``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 AUTHOR 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.
+ */
+
+#if defined(LIBC_SCCS) && !defined(lint)
+static char *rcsid = "$OpenBSD: strlcat.c,v 1.2 1999/06/17 16:28:58 millert Exp $";
+#endif /* LIBC_SCCS and not lint */
+
+#include <sys/types.h>
+#include <string.h>
+
+/*
+ * Appends src to string dst of size siz (unlike strncat, siz is the
+ * full size of dst, not space left). At most siz-1 characters
+ * will be copied. Always NUL terminates (unless siz == 0).
+ * Returns strlen(src); if retval >= siz, truncation occurred.
+ */
+size_t strlcat(dst, src, siz)
+ char *dst;
+ const char *src;
+ size_t siz;
+{
+ register char *d = dst;
+ register const char *s = src;
+ register size_t n = siz;
+ size_t dlen;
+
+ /* Find the end of dst and adjust bytes left but don't go past end */
+ while (*d != '\0' && n-- != 0)
+ d++;
+ dlen = d - dst;
+ n = siz - dlen;
+
+ if (n == 0)
+ return(dlen + strlen(s));
+ while (*s != '\0') {
+ if (n != 1) {
+ *d++ = *s;
+ n--;
+ }
+ s++;
+ }
+ *d = '\0';
+
+ return(dlen + (s - src)); /* count does not include NUL */
+}
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+.\" $OpenBSD: strlcpy.3,v 1.6 1999/09/04 02:22:46 pjanzen Exp $
+.\"
+.\" Copyright (c) 1998 Todd C. Miller <Todd.Miller@courtesan.com>
+.\" 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. The name of the author may not be used to endorse or promote products
+.\" derived from this software without specific prior written permission.
+.\"
+.\" THIS SOFTWARE IS PROVIDED ``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 AUTHOR 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 June 22, 1998
+.Dt STRLCPY 3
+.Os
+.Sh NAME
+.Nm strlcpy ,
+.Nm strlcat
+.Nd size-bounded string copying and concatenation
+.Sh SYNOPSIS
+.Fd #include <string.h>
+.Ft size_t
+.Fn strlcpy "char *dst" "const char *src" "size_t size"
+.Ft size_t
+.Fn strlcat "char *dst" "const char *src" "size_t size"
+.Sh DESCRIPTION
+The
+.Fn strlcpy
+and
+.Fn strlcat
+functions copy and concatenate strings respectively. They are designed
+to be safer, more consistent, and less error prone replacements for
+.Xr strncpy 3
+and
+.Xr strncat 3 .
+Unlike those functions,
+.Fn strlcpy
+and
+.Fn strlcat
+take the full size of the buffer (not just the length) and guarantee to
+NUL-terminate the result (as long as
+.Fa size
+is larger than 0). Note that you should include a byte for the NUL in
+.Fa size .
+.Pp
+The
+.Fn strlcpy
+function copies up to
+.Fa size
+- 1 characters from the NUL-terminated string
+.Fa src
+to
+.Fa dst ,
+NUL-terminating the result.
+.Pp
+The
+.Fn strlcat
+function appends the NUL-terminated string
+.Fa src
+to the end of
+.Fa dst .
+It will append at most
+.Fa size
+- strlen(dst) - 1 bytes, NUL-terminating the result.
+.Sh RETURN VALUES
+The
+.Fn strlcpy
+and
+.Fn strlcat
+functions return the total length of the string they tried to
+create. For
+.Fn strlcpy
+that means the length of
+.Fa src .
+For
+.Fn strlcat
+that means the initial length of
+.Fa dst
+plus
+the length of
+.Fa src .
+While this may seem somewhat confusing it was done to make
+truncation detection simple.
+.Sh EXAMPLES
+The following code fragment illustrates the simple case:
+.Bd -literal -offset indent
+char *s, *p, buf[BUFSIZ];
+
+\&...
+
+(void)strlcpy(buf, s, sizeof(buf));
+(void)strlcat(buf, p, sizeof(buf));
+.Ed
+.Pp
+To detect truncation, perhaps while building a pathname, something
+like the following might be used:
+.Bd -literal -offset indent
+char *dir, *file, pname[MAXPATHNAMELEN];
+
+\&...
+
+if (strlcpy(pname, dir, sizeof(pname)) >= sizeof(pname))
+ goto toolong;
+if (strlcat(pname, file, sizeof(pname)) >= sizeof(pname))
+ goto toolong;
+.Ed
+.Pp
+Since we know how many characters we copied the first time, we can
+speed things up a bit by using a copy instead on an append:
+.Bd -literal -offset indent
+char *dir, *file, pname[MAXPATHNAMELEN];
+size_t n;
+
+\&...
+
+n = strlcpy(pname, dir, sizeof(pname));
+if (n >= sizeof(pname))
+ goto toolong;
+if (strlcpy(pname + n, file, sizeof(pname) - n) >= sizeof(pname) - n)
+ goto toolong;
+.Ed
+.Pp
+However, one may question the validity of such optimizations, as they
+defeat the whole purpose of
+.Fn strlcpy
+and
+.Fn strlcat .
+As a matter of fact, the first version of this manual page got it wrong.
+.Sh SEE ALSO
+.Xr snprintf 3 ,
+.Xr strncat 3 ,
+.Xr strncpy 3
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+/* $OpenBSD: strlcpy.c,v 1.4 1999/05/01 18:56:41 millert Exp $ */
+
+/*
+ * Copyright (c) 1998 Todd C. Miller <Todd.Miller@courtesan.com>
+ * 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. The name of the author may not be used to endorse or promote products
+ * derived from this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED ``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 AUTHOR 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.
+ */
+
+#if defined(LIBC_SCCS) && !defined(lint)
+static char *rcsid = "$OpenBSD: strlcpy.c,v 1.4 1999/05/01 18:56:41 millert Exp $";
+#endif /* LIBC_SCCS and not lint */
+
+#include <sys/types.h>
+#include <string.h>
+
+/*
+ * Copy src to string dst of size siz. At most siz-1 characters
+ * will be copied. Always NUL terminates (unless siz == 0).
+ * Returns strlen(src); if retval >= siz, truncation occurred.
+ */
+size_t strlcpy(dst, src, siz)
+ char *dst;
+ const char *src;
+ size_t siz;
+{
+ register char *d = dst;
+ register const char *s = src;
+ register size_t n = siz;
+
+ /* Copy as many bytes as will fit */
+ if (n != 0 && --n != 0) {
+ do {
+ if ((*d++ = *s++) == 0)
+ break;
+ } while (--n != 0);
+ }
+
+ /* Not enough room in dst, add NUL and traverse rest of src */
+ if (n == 0) {
+ if (siz != 0)
+ *d = '\0'; /* NUL-terminate dst */
+ while (*s++)
+ ;
+ }
+
+ return(s - src - 1); /* count does not include NUL */
+}

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