Password with libpq

[Tony Reina]

I'm setting my PostgreSQL server to demand md5 encrypted passwords
from users. In my C programs (using libpq as the interface), it's no
big deal to pass the password through PQconnectdb.

However, what about in the general case where my client program
doesn't know if a password is required or not. Is there any libpq
function to query the server if a password is required? Perhaps,
there's a return value for PQconnectdb which would tell me that the
connection failed because of the password? (In which case, I can ask
for the password and try the connection again.)

Thanks.
-Tony

[Tom Lane]

Post by Tony Reina
However, what about in the general case where my client program
doesn't know if a password is required or not. Is there any libpq
function to query the server if a password is required? Perhaps,
there's a return value for PQconnectdb which would tell me that the
connection failed because of the password? (In which case, I can ask
for the password and try the connection again.)

Look into the psql source code; it does essentially this.

regards, tom lane

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[Tony and Bryn Reina]

Thanks Tom. I found the relevant bit of code in the psql files. Looks like
it's just a simple loop that compares the error with the phrase
"fe_sendauth: no password supplied" and then prompts for the password and
tries again. Of course, if someone in the future decides to change the error
message, then the code gets broke. I doubt that's likely however.

-Tony



----- Original Message -----
From: "Tom Lane" <***@sss.pgh.pa.us>
To: "Tony Reina" <***@hotmail.com>
Cc: <pgsql-***@postgresql.org>
Sent: Monday, June 28, 2004 12:12 AM
Subject: Re: [ADMIN] Password with libpq

Post by Tom Lane

Post by Tony Reina
However, what about in the general case where my client program
doesn't know if a password is required or not. Is there any libpq
function to query the server if a password is required? Perhaps,
there's a return value for PQconnectdb which would tell me that the
connection failed because of the password? (In which case, I can ask
for the password and try the connection again.)

Look into the psql source code; it does essentially this.
regards, tom lane

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[Peter Eisentraut]

Post by Tony and Bryn Reina
Thanks Tom. I found the relevant bit of code in the psql files. Looks
like it's just a simple loop that compares the error with the phrase
"fe_sendauth: no password supplied" and then prompts for the password
and tries again. Of course, if someone in the future decides to
change the error message, then the code gets broke. I doubt that's
likely however.

Eventually, we should introduce error codes for this situation.


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