From mboxrd@z Thu Jan  1 00:00:00 1970
References: <03dd9a6798effc7cf713d579f6bbc0e6@isd.dp.ua>
	<636BFA64-E5C9-417C-AD9E-E6BCEAACB02B@gmail.com>
	<6b9a2d8b5b0dcba57658809a76c2c89f@brasstown.quanstro.net>
From: Don Bailey <don.bailey@gmail.com>
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In-Reply-To: <6b9a2d8b5b0dcba57658809a76c2c89f@brasstown.quanstro.net>
Message-Id: <05BFA886-F720-4783-BC80-56B01AF7A101@gmail.com>
Date: Wed,  5 Jun 2013 07:40:02 -0600
To: Fans of the OS Plan 9 from Bell Labs <9fans@9fans.net>
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Subject: Re: [9fans] lpdaemon
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Not exactly. But, functionally close enough.=20

I skipped commenting on strncpy to ignore the plethora of issues with lpd an=
d focus on the question at hand.

D

On Jun 5, 2013, at 7:20 AM, erik quanstrom <quanstro@quanstro.net> wrote:

> On Wed Jun  5 09:15:11 EDT 2013, don.bailey@gmail.com wrote:
>> The first opportunity to write a nil byte should always be taken.
>> Using sizeof only means that in corner cases memory disclosure may
>> occur between where the nil should be and the end of the array.  While
>> this isn't a security critical app, it is still good coding practice.
>>=20
>> x =3D strlen(info.host) < sizeof info.host ? strlen() : sizeof ;
>> info.host[x] =3D 0;
>=20
> let's start at the beginning.  strncpy is not good coding practice.
> and lpdaemon is not well written by today's standards.  =E2=98=BA
>=20
> however, unless i'm missing something, the code has exactly that.
>=20
> /sys/src/cmd/lp/lpdaemon.c:297,310
>        case 'H':
>            if (ap[1] =3D=3D '\0')
>                strncpy(info.host, "unknown", NAMELEN);
>            else
>                strncpy(info.host, (const char *)&ap[1], NAMELEN);
>            info.host[NAMELEN] =3D '\0';
>            break;
>        case 'P':
>            if (ap[1] =3D=3D '\0')
>                strncpy(info.user, "unknown", NAMELEN);
>            else
>                strncpy(info.user, (const char *)&ap[1], NAMELEN);
>            info.user[NAMELEN] =3D '\0';
>            break;
>=20
> - erik
>=20