[UNIX] Off-by-One Error in realpath (FreeBSD)

From: SecuriTeam (support_at_securiteam.com)
Date: 08/05/03

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      Off-by-One Error in realpath (FreeBSD)
    ------------------------------------------------------------------------

    SUMMARY

    An off-by-one error exists in the C library function realpath(3). This is
    the same bug that was recently found in the
    <http://www.securiteam.com/unixfocus/5ZP010AAUI.html> wu-ftpd ftpd server
    by Janusz Niewiadomski and Janusz Niewiadomski.

    DETAILS

    The OpenBSD ftp daemon does not use realpath(3) in a way that could be
    exploited, however a number of other system binaries also use the
    function. It is not currently known whether this bug results in an
    exploitable security hole on OpenBSD. Since the bug led to an exploitable
    hole in wu-ftpd, it is entirely possible that some program using
    realpath(3) under OpenBSD may be vulnerable to attack. For OpenBSD 3.3
    and higher, the ProPolice stack protector should provide some protection
    from this bug, but this cannot be guaranteed.

    This bug has been fixed in OpenBSD-current as well as the 3.2 and 3.3
    stable branches. Patches are available for OpenBSD 3.2 and 3.3.

    Patch for OpenBSD 3.2:
     <ftp://ftp.OpenBSD.org/pub/OpenBSD/patches/3.2/common/015_realpath.patch>
    ftp://ftp.OpenBSD.org/pub/OpenBSD/patches/3.2/common/015_realpath.patch

    Patch for OpenBSD 3.3:
    <ftp://ftp.OpenBSD.org/pub/OpenBSD/patches/3.3/common/001_realpath.patch>
    ftp://ftp.OpenBSD.org/pub/OpenBSD/patches/3.3/common/001_realpath.patch

    For versions of OpenBSD prior to 3.2, users may simply fetch the current
    revision of realpath.c from:
    <ftp://ftp.OpenBSD.org/pub/OpenBSD/src/lib/libc/stdlib/realpath.c>
    ftp://ftp.OpenBSD.org/pub/OpenBSD/src/lib/libc/stdlib/realpath.c then
    rebuild and install libc with the new realpath.c.

    ADDITIONAL INFORMATION

    The information has been provided by <mailto:Todd.Miller@courtesan.com>
    Todd C. Miller.

    ========================================

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