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Date:      Sun, 18 Feb 2018 03:38:53 +0000
From:      bugzilla-noreply@freebsd.org
To:        freebsd-bugs@FreeBSD.org
Subject:   [Bug 225996] tftpd(8): tftpd doesn't abort on a WRQ access violation
Message-ID:  <bug-225996-8@https.bugs.freebsd.org/bugzilla/>

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https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=3D225996

            Bug ID: 225996
           Summary: tftpd(8): tftpd doesn't abort on a WRQ access
                    violation
           Product: Base System
           Version: CURRENT
          Hardware: Any
                OS: Any
            Status: New
          Severity: Affects Some People
          Priority: ---
         Component: bin
          Assignee: freebsd-bugs@FreeBSD.org
          Reporter: asomers@FreeBSD.org

On a WRQ (write request) tftpd checks whether the client has access permiss=
ion
for the file in question.  If not, then the write is prevented.  However, t=
ftpd
doesn't reply with an ERROR packet, nor does it abort.  Instead, it tries to
receive the packet anyway.  The bug is in tftp_wrq() at line 543.  There is=
 no
error handling for ecode !=3D 0.

The symptom is slightly different depending on the nature of the error.  If=
 the
target file is nonexistent and tftpd lacks permission to create it, then tf=
tpd
will willingly receive the file, but not write it anywhere.  If the file ex=
ists
but is not writable, then tftpd will fail to ACK to WRQ.

tftp> put small.txt nonexistent
Try 1, didn't receive answer from remote.
Sent 7 bytes during 5.1 seconds in 1 blocks
tftp> put small.txt small.txt
Timeout #1 on ACK 1
Timeout #3 on ACK 1
Timeout #5 send ACK 1 giving up

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