0afc94c17a
bottom of the manpages and order them consistently. GNU groff doesn't care about the ordering, and doesn't even mention CAVEATS and SECURITY CONSIDERATIONS as common sections and where to put them. Found by: mdocml lint run Reviewed by: ru
109 lines
3.3 KiB
Groff
109 lines
3.3 KiB
Groff
.\" Copyright (c) 2000 The NetBSD Foundation, Inc.
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.\" All rights reserved.
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.\"
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.\" This file was contributed to The NetBSD Foundation by Allen Briggs.
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.\"
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.\" Redistribution and use in source and binary forms, with or without
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.\" modification, are permitted provided that the following conditions
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.\" are met:
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.\" 1. Redistributions of source code must retain the above copyright
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.\" notice, this list of conditions and the following disclaimer.
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.\" 2. Redistributions in binary form must reproduce the above copyright
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.\" notice, this list of conditions and the following disclaimer in the
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.\" documentation and/or other materials provided with the distribution.
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.\"
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.\" THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
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.\" ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
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.\" TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
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.\" PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
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.\" BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
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.\" CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
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.\" SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
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.\" INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
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.\" CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
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.\" ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
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.\" POSSIBILITY OF SUCH DAMAGE.
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.\"
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.\" $FreeBSD$
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.Dd October 16, 2002
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.Dt FMTCHECK 3
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.Os
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.Sh NAME
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.Nm fmtcheck
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.Nd sanitizes user-supplied
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.Xr printf 3 Ns -style
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format string
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.Sh LIBRARY
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.Lb libc
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.Sh SYNOPSIS
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.In stdio.h
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.Ft const char *
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.Fn fmtcheck "const char *fmt_suspect" "const char *fmt_default"
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.Sh DESCRIPTION
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The
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.Fn fmtcheck
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scans
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.Fa fmt_suspect
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and
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.Fa fmt_default
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to determine if
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.Fa fmt_suspect
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will consume the same argument types as
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.Fa fmt_default
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and to ensure that
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.Fa fmt_suspect
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is a valid format string.
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.Pp
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The
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.Xr printf 3
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family of functions cannot verify the types of arguments that they are
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passed at run-time.
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In some cases, like
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.Xr catgets 3 ,
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it is useful or necessary to use a user-supplied format string with no
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guarantee that the format string matches the specified arguments.
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.Pp
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The
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.Fn fmtcheck
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was designed to be used in these cases, as in:
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.Bd -literal -offset indent
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printf(fmtcheck(user_format, standard_format), arg1, arg2);
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.Ed
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.Pp
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In the check, field widths, fillers, precisions, etc.\& are ignored (unless
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the field width or precision is an asterisk
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.Ql *
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instead of a digit string).
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Also, any text other than the format specifiers
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is completely ignored.
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.Sh RETURN VALUES
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If
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.Fa fmt_suspect
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is a valid format and consumes the same argument types as
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.Fa fmt_default ,
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then the
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.Fn fmtcheck
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will return
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.Fa fmt_suspect .
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Otherwise, it will return
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.Fa fmt_default .
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.Sh SEE ALSO
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.Xr printf 3
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.Sh BUGS
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The
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.Fn fmtcheck
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function does not recognize positional parameters.
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.Sh SECURITY CONSIDERATIONS
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Note that the formats may be quite different as long as they accept the
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same arguments.
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For example,
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.Qq Li "%p %o %30s %#llx %-10.*e %n"
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is compatible with
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.Qq Li "This number %lu %d%% and string %s has %qd numbers and %.*g floats (%n)" .
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However,
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.Qq Li %o
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is not equivalent to
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.Qq Li %lx
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because
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the first requires an integer and the second requires a long.
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