Remove one use of IDENT_USERNAME_MAX

It seems to me that using IDENT_USERNAME_MAX for peer authentication is
some kind of historical leftover and not really appropriate or useful,
so I propose the attached cleanup.

--
Peter Eisentraut http://www.2ndQuadrant.com/
PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services

Hello.

At Sat, 26 Oct 2019 08:55:03 +0200, Peter Eisentraut <peter(dot)eisentraut(at)2ndquadrant(dot)com> wrote in
> IDENT_USERNAME_MAX is the maximum length of the information returned
> by an ident server, per RFC 1413. Using it as the buffer size in peer
> authentication is inappropriate. It was done here because of the
> historical relationship between peer and ident authentication. But
> since it's also completely useless code-wise, remove it.

In think one of the reasons for the coding is the fact that *pw is
described to be placed in the static area, which can be overwritten by
succeeding calls to getpw*() functions. I think we can believe
check_usermap() never calls them but I suppose that some comments
needed..

regards.

--
Kyotaro Horiguchi
NTT Open Source Software Center

Kyotaro Horiguchi <horikyota(dot)ntt(at)gmail(dot)com> writes:
> At Sat, 26 Oct 2019 08:55:03 +0200, Peter Eisentraut <peter(dot)eisentraut(at)2ndquadrant(dot)com> wrote in
>> IDENT_USERNAME_MAX is the maximum length of the information returned
>> by an ident server, per RFC 1413. Using it as the buffer size in peer
>> authentication is inappropriate. It was done here because of the
>> historical relationship between peer and ident authentication. But
>> since it's also completely useless code-wise, remove it.

> In think one of the reasons for the coding is the fact that *pw is
> described to be placed in the static area, which can be overwritten by
> succeeding calls to getpw*() functions.

Good point ... so maybe pstrdup instead of using a fixed-size buffer?

regards, tom lane

On 2019-10-28 14:45, Tom Lane wrote:
> Kyotaro Horiguchi <horikyota(dot)ntt(at)gmail(dot)com> writes:
>> At Sat, 26 Oct 2019 08:55:03 +0200, Peter Eisentraut <peter(dot)eisentraut(at)2ndquadrant(dot)com> wrote in
>>> IDENT_USERNAME_MAX is the maximum length of the information returned
>>> by an ident server, per RFC 1413. Using it as the buffer size in peer
>>> authentication is inappropriate. It was done here because of the
>>> historical relationship between peer and ident authentication. But
>>> since it's also completely useless code-wise, remove it.
>
>> In think one of the reasons for the coding is the fact that *pw is
>> described to be placed in the static area, which can be overwritten by
>> succeeding calls to getpw*() functions.
>
> Good point ... so maybe pstrdup instead of using a fixed-size buffer?

Maybe. Or we just decide that check_usermap() is not allowed to call
getpw*(). It's just a string-matching routine, so it doesn't have any
such business anyway.

--
Peter Eisentraut http://www.2ndQuadrant.com/
PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services

Peter Eisentraut <peter(dot)eisentraut(at)2ndquadrant(dot)com> writes:
> On 2019-10-28 14:45, Tom Lane wrote:
>> Kyotaro Horiguchi <horikyota(dot)ntt(at)gmail(dot)com> writes:
>>> In think one of the reasons for the coding is the fact that *pw is
>>> described to be placed in the static area, which can be overwritten by
>>> succeeding calls to getpw*() functions.

>> Good point ... so maybe pstrdup instead of using a fixed-size buffer?

> Maybe. Or we just decide that check_usermap() is not allowed to call
> getpw*(). It's just a string-matching routine, so it doesn't have any
> such business anyway.

I'm okay with that as long as you add a comment describing this
assumption.

regards, tom lane

On 2019-10-29 15:34, Tom Lane wrote:
> Peter Eisentraut <peter(dot)eisentraut(at)2ndquadrant(dot)com> writes:
>> On 2019-10-28 14:45, Tom Lane wrote:
>>> Kyotaro Horiguchi <horikyota(dot)ntt(at)gmail(dot)com> writes:
>>>> In think one of the reasons for the coding is the fact that *pw is
>>>> described to be placed in the static area, which can be overwritten by
>>>> succeeding calls to getpw*() functions.
>
>>> Good point ... so maybe pstrdup instead of using a fixed-size buffer?
>
>> Maybe. Or we just decide that check_usermap() is not allowed to call
>> getpw*(). It's just a string-matching routine, so it doesn't have any
>> such business anyway.
>
> I'm okay with that as long as you add a comment describing this
> assumption.

Committed with a pstrdup(). That seemed more consistent with other code
in that file.

--
Peter Eisentraut http://www.2ndQuadrant.com/
PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services