Обсуждение: retrieving information about password from MS Access front-end

Am Sonntag, den 12.06.2005, 23:12 +0200 schrieb Zlatko Matić:
> How could I retrieve information about actual user password, if md5
> method is set in pg_hba.conf ?
> I want to create VBA procedure that compares value in text box with
> actual password to determine if it is the same. As the password is
> encrypted (md5) I can't read it from pg_shaddow system table. How to
> retrieve decrypted value from pg_shaddow? Or at least, how to transfer
> value from text-box (MS Access) to Postgres so that Postgres can
> determine whether those two values are the same ?

You cant. md5 really is a hash, not encryption (there is no decryption)
You would just try to connect - postgres will tell you if the password
is wrong.

Hi,

On 6/13/05, Zlatko Matić <zlatko.matic1@sb.t-com.hr> wrote:
> I want to create VBA procedure that compares value in text box with actual
> password to determine if it is the same. As the password is encrypted (md5)
> I can't read it from pg_shaddow system table. How to retrieve decrypted
> value from pg_shaddow?

It's (practically) impossible to decrypt a MD5 hashed password.

> Or at least, how to transfer value from text-box (MS Access) to Postgres
> so that Postgres can determine whether those two values
> are the same ?

You need to MD5 hash the input passsword and compare hashed input
password with the one in pg_shadow. For instance:

-- $1 for password input.
SELECT usernm FROM recs WHERE passwd = md5($1)

Furthermore, it'll bring some potential security problems to be able
to access pg_shadow which requires db admin permissions.

Regards.

Thanks.
----- Original Message -----
From: "Volkan YAZICI" <volkan.yazici@gmail.com>
To: "Zlatko Matić" <zlatko.matic1@sb.t-com.hr>
Cc: <pgsql-general@postgresql.org>; <pgsql-interfaces@postgresql.org>
Sent: Monday, June 13, 2005 8:47 AM
Subject: Re: [GENERAL] [INTERFACES] retrieving information about password
from MS Access front-end


> Hi,
>
> On 6/13/05, Zlatko Matić <zlatko.matic1@sb.t-com.hr> wrote:
>> I want to create VBA procedure that compares value in text box with
>> actual
>> password to determine if it is the same. As the password is encrypted
>> (md5)
>> I can't read it from pg_shaddow system table. How to retrieve decrypted
>> value from pg_shaddow?
>
> It's (practically) impossible to decrypt a MD5 hashed password.
>
>> Or at least, how to transfer value from text-box (MS Access) to Postgres
>> so that Postgres can determine whether those two values
>> are the same ?
>
> You need to MD5 hash the input passsword and compare hashed input
> password with the one in pg_shadow. For instance:
>
> -- $1 for password input.
> SELECT usernm FROM recs WHERE passwd = md5($1)
>
> Furthermore, it'll bring some potential security problems to be able
> to access pg_shadow which requires db admin permissions.
>
> Regards.
>
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