PostgreSQL authentication quick start

Connecting to PostgreSQL from command line can be a bit confusing.

For starter, just like MySQL, psql command defaults to connecting to socket instead of tcp. To make matter confusing, most PostgreSQL installation defaults to ident (also called peer)authentication for socket connection: it basically matches current user’s username (ssh login, etc) with PostgreSQL equivalent.

So, instead of using this to login from root to PostgreSQL superuser (usually named postgres or pgsql):

# psql -U postgres

you do this (assuming sudo installed):

# sudo -u postgres psql

The configuration for this is located in pg_hba.conf of PostgreSQL data (or config in Debian) directory (/etc/postgresql/$version/main in Debian, /usr/local/pgsql/data in FreeBSD, /opt/PostgreSQL/$version/data in EnterpriseDB PostgreSQL).

To switch to password based authentication for all methods just replace ident (or peer) with md5 in respective lines and reload/restart the service. Don’t forget to set password for postgres user first before changing this otherwise you won’t be able to connect. You can then connect using psql to any user using password.

bcrypt in Debian

WARNING: using method below will lock yourself out when using emergency console since whatever crypt it’s using surely doesn’t understand bcrypt (as I experienced myself). Additionally, this solution won’t add bcrypt support to other applications using crypt interface like proftpd unless it’s started by preloading first (also from my own experience).

As much as Drepper want to pretend bcrypt is wrong solution, it actually gives one benefit: ease of switch to Linux. Some systems use bcrypt by default or configurable to use it. On other case, there might be time where you need system’s (or applications using system’s) crypt to handle bcrypt passwords from external system (usually web applications).

It’s quite difficult to enable bcrypt support in RHEL based distro as there is no libxcrypt and pam_unix2 packages available. Thankfully it’s available in Debian (and derivatives) in package libpam-unix2.

The README.Debian says to modify files in /etc/pam.d but if I remember it correctly, it confused apt PAM handling system or whatever. Fast forward few weeks, I discovered a better way to use it by creating PAM configuration in /usr/share/pam-configs. Since it’s mostly equivalent to normal pam_unix, I just copy and modify the file using this (long-ass) oneliner sed:

sed -e 's/;s/^Name: Unix authentication$/Name: Unix2 authentication/;s/ obscure sha512/ obscure blowfish rounds=8/;s/ nullok_secure//' /usr/share/pam-configs/unix > /usr/share/pam-configs/unix2

Then execute pam-auth-update, select Unix2 authentication and deselect Unix authentication. Don’t forget to update passwords for all other users as well or they won’t be able to login since pam_unix2 doesn’t recognize sha based hashes.

Actually, change all other users password to use md5 first before replacing the PAM with pam_unix2.

Update 2012-04-01: Removed nullok_secure since it isn’t supported.

Update 2012-06-09: Added warning.

Compiling PuTTY for Windows

Because of one awesome bug inflicts eye-cancer when using Consolas font and deactivated “Bold text is a different colour”, I had to recompile PuTTY by hand (more like, by gcc). I initially tried to compile the PuTTYTray one but apparently they successfully mixed C and C++ code and completely broke the build procedure using mingw. Or I missed something obvious.

Anyway, I went back to vanilla PuTTY. As it turns out, compiling using latest mingw’s gcc isn’t a good idea since it removed -mno-cygwin option and therefore broken unless you do some magic edit. Thanks to that, I stopped bothering trying to compile it under Windows and used mingw-gcc for Linux (which is able to produce Windows binary). Here be the steps from beginning. Tested on Debian 6.

apt-get install mingw32 subversion perl
svn co svn:// putty
cd putty
cd windows
make VER="-DSNAPSHOT=$(date '+%Y-%m-%d') -DSVN_REV='$(svnversion)' -DMODIFIED" TOOLPATH=i586-mingw32msvc- -f Makefile.cyg putty.exe

Patch is done before make (duh) and the diff can be found here. If you’re lazy (like me) you can just download the build at my server (link at bottom). Should be virus-free but I guess you can notify me if you encounter one. Built everyday until it breaks.

  • exe: the program
  • sha512: hash of the program
  • zip: both program and its checksum

[ exe | sha512 | zip ]

Debian’s sources.list

I kept forgetting them whenever I need one so I’ll put mine here and be happy:

###### Debian Main Repos
deb squeeze main contrib non-free
#deb-src squeeze main contrib non-free

###### Debian Security Update Repos
deb squeeze/updates main contrib non-free
#deb-src squeeze/updates main contrib non-free

###### Debian General Update Repos
deb squeeze-updates main contrib non-free
#deb-src squeeze-updates main contrib non-free

###### Debian Backports Repos
deb squeeze-backports main contrib non-free
#deb-src squeeze-backports main contrib non-free

###### Dotdeb Repo
#deb squeeze all
#deb-src squeeze all

It should cover mostly used packages and will keep me sane. Also debian-volatile has been replaced with debian-updates (god knows why it’s called like that) since squeeze (6.0) but in case I need to take care a lenny or earlier (derp) machines, this should also be added:

deb lenny/volatile main contrib non-free

Oh and Debian/kFreeBSD within a FreeBSD system is quite funny.

Update 2012-12-27: Use improved CDN.