GNU bug report logs - #30535
Output buffer overwritten when CR in file

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Package: grep; Severity: wishlist; Reported by: Wayne Gemmell <wayne@HIDDEN>; merged with #30652; dated Mon, 19 Feb 2018 17:31:02 UTC; Maintainer for grep is bug-grep@HIDDEN.
Merged 30535 30652. Request was from Paul Eggert <eggert@HIDDEN> to control <at> debbugs.gnu.org. Full text available.
Removed tag(s) notabug. Request was from Paul Eggert <eggert@HIDDEN> to control <at> debbugs.gnu.org. Full text available.
Added tag(s) notabug. Request was from Paul Eggert <eggert@HIDDEN> to control <at> debbugs.gnu.org. Full text available.
Severity set to 'wishlist' from 'normal' Request was from Paul Eggert <eggert@HIDDEN> to control <at> debbugs.gnu.org. Full text available.

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From: Wayne Gemmell <wayne@HIDDEN>
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Message-ID: <CA+z1FeKfut0Pq2CjB9x6UWJk=phro91N9cJUXae6LgRbJoc9GQ@HIDDEN>
Subject: Re: bug#30535: Output buffer overwritten when CR in file
To: Paul Eggert <eggert@HIDDEN>
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Hi Paul

That is exactly what I am getting. It is probably acting quite correctly,
the problem is that the shell executing those control characters is both
confusing and a possible security risk. I've tried this in ksh, dash, bash
and zsh and they all execute the control characters.

I think that they should be suppressed or escaped by default and a flag
should be provided to allow them to be passed out unescaped. Maybe this has
become a feature request...



On Mon, 19 Feb 2018 at 22:13 Paul Eggert <eggert@HIDDEN> wrote:

> Wayne Gemmell wrote:
> > I would expect the CR to be output verbatim
>
> It is output verbatim, just as you expect. For example:
>
> $ printf 'messag1\rlogin\rmask' >test.log
> 503-day $ grep --color=never login test.log | od -c
> 0000000   m   e   s   s   a   g   1  \r   l   o   g   i   n  \r   m   a
> 0000020   s   k  \n
> 0000023
>
-- 
Regards
Wayne

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<div dir=3D"ltr">Hi Paul<div><br></div><div>That is exactly what I am getti=
ng. It is probably acting quite correctly, the problem is that the shell ex=
ecuting those control characters is both confusing and a possible security =
risk. I&#39;ve tried this in ksh, dash, bash and zsh and they all execute t=
he control characters.=C2=A0</div><div><br></div><div>I think that they sho=
uld be suppressed or escaped by default and a flag should be provided to al=
low them to be passed out unescaped. Maybe this has become a feature reques=
t...</div><div><br><div><br></div></div></div><br><div class=3D"gmail_quote=
"><div dir=3D"ltr">On Mon, 19 Feb 2018 at 22:13 Paul Eggert &lt;<a href=3D"=
mailto:eggert@HIDDEN">eggert@HIDDEN</a>&gt; wrote:<br></div><bloc=
kquote class=3D"gmail_quote" style=3D"margin:0 0 0 .8ex;border-left:1px #cc=
c solid;padding-left:1ex">Wayne Gemmell wrote:<br>
&gt; I would expect the CR to be output verbatim<br>
<br>
It is output verbatim, just as you expect. For example:<br>
<br>
$ printf &#39;messag1\rlogin\rmask&#39; &gt;test.log<br>
503-day $ grep --color=3Dnever login test.log | od -c<br>
0000000=C2=A0 =C2=A0m=C2=A0 =C2=A0e=C2=A0 =C2=A0s=C2=A0 =C2=A0s=C2=A0 =C2=
=A0a=C2=A0 =C2=A0g=C2=A0 =C2=A01=C2=A0 \r=C2=A0 =C2=A0l=C2=A0 =C2=A0o=C2=A0=
 =C2=A0g=C2=A0 =C2=A0i=C2=A0 =C2=A0n=C2=A0 \r=C2=A0 =C2=A0m=C2=A0 =C2=A0a<b=
r>
0000020=C2=A0 =C2=A0s=C2=A0 =C2=A0k=C2=A0 \n<br>
0000023<br>
</blockquote></div>-- <br><div dir=3D"ltr" class=3D"gmail_signature" data-s=
martmail=3D"gmail_signature"><div dir=3D"ltr">Regards<div>Wayne</div></div>=
</div>

--f403045ebc7aa01dff05659fd602--
Information forwarded to bug-grep@HIDDEN:
bug#30535; Package grep. Full text available.

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Subject: Re: bug#30535: Output buffer overwritten when CR in file
To: Wayne Gemmell <wayne@HIDDEN>, 30535 <at> debbugs.gnu.org
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Wayne Gemmell wrote:
> I would expect the CR to be output verbatim

It is output verbatim, just as you expect. For example:

$ printf 'messag1\rlogin\rmask' >test.log
503-day $ grep --color=never login test.log | od -c
0000000   m   e   s   s   a   g   1  \r   l   o   g   i   n  \r   m   a
0000020   s   k  \n
0000023
Information forwarded to bug-grep@HIDDEN:
bug#30535; Package grep. Full text available.

Message received at submit <at> debbugs.gnu.org:


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Subject: Output buffer overwritten when CR in file
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--089e082ef7481d5b77056591a0da
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Hi

I have an issue with files that contain carriage returns. I have log files
that contain user input which sometime has carriage returns. The EOL
characters are fine so I can't throw mac2unix at the problem.

The issue is that when grep outputs the CR it follows the CR to the
beginning of the output buffer and overwrites the contents of the output
buffer.

E.g. the file, test.log with the following contents.

messag1^Mlogin^Mmask

The following command
$>/grep --color=never login test.log
Outputs as follows
$>maskng1

This seems like a security concern as you may be able to mask activity in
logs just by inserting CR in place. It would be superficial but it would
fool basic grep based logfile processing.

I would expect the CR to be output verbatim so as not to confuse the reader
of the output.


-- 
Regards
Wayne

--089e082ef7481d5b77056591a0da
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<div dir=3D"ltr">Hi<div><br></div><div>I have an issue with files that cont=
ain carriage returns. I have log files that contain user input which someti=
me has carriage returns. The EOL characters are fine so I can&#39;t throw m=
ac2unix at the problem.=C2=A0</div><div><br></div><div>The issue is that wh=
en grep outputs the CR it follows the CR to the beginning of the output buf=
fer and overwrites the contents of the output buffer.=C2=A0</div><div><br><=
/div><div>E.g. the file, test.log with the following contents.=C2=A0</div><=
div><br></div><div><div>messag1^Mlogin^Mmask</div></div><div><br></div><div=
>The following command</div><div>$&gt;/grep --color=3Dnever login test.log<=
/div><div>Outputs as follows<br></div><div>$&gt;maskng1<br></div><div><br><=
/div><div>This seems like a security concern as you may be able to mask act=
ivity in logs just by inserting CR in place. It would be superficial but it=
 would fool basic grep based logfile processing.=C2=A0</div><div><br></div>=
<div>I would expect the CR to be output verbatim so as not to confuse the r=
eader of the output.=C2=A0</div><div><br></div><div><br></div></div>-- <br>=
<div dir=3D"ltr" class=3D"gmail_signature" data-smartmail=3D"gmail_signatur=
e"><div dir=3D"ltr">Regards<div>Wayne</div></div></div>

--089e082ef7481d5b77056591a0da--
Acknowledgement sent to Wayne Gemmell <wayne@HIDDEN>:
New bug report received and forwarded. Copy sent to bug-grep@HIDDEN. Full text available.
Report forwarded to bug-grep@HIDDEN:
bug#30535; Package grep. Full text available.
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