Built-in authentication

See also "Authentication on web interface".

The built-in authentication mechanism provides authentication for user of web interface (WWSympa) using their e-mail addresses and passwords. It is enabled by default.

Requirements

• To use bcrypt hash (see below), you have to install the Crypt-Eksblowfish Perl module. It is recommended.

Sympa configuration

• Make sure that user_table paragraph in auth.conf exists. It enables default authentication.

  If this paragraph is omitted, built-in authentication is disabled.

In sympa.conf, following parameters are available:

• password_case

  If set to be insensitive, storing and checking password will be case-insensitive.

  Note that, once you set this parameter, you should not change it. Or all user passwords may be invalidated.

• password_hash

  Information of users are stored in database table user_table. This parameter specifies a method to generate password hash. Currently these values are possible:

  • md5

    Uses MD5 digest algorithm.

  • bcrypt

    Uses bcrypt hash function.

  Note

  • The bcrypt hash was introduced on Sympa 6.2.26. See also "History of password storage format of Sympa" below.

• password_hash_update

  If this parameter is set to 1 any supported password hash type (currently md5 or bcrypt) that does not match the current setting of password_hash is updated to the current hash type upon successful login.

  For instance, if password_hash_update is 1 and password_hash has been set to bcrypt, Sympa will update an MD5 password hash to a bcrypt hash on successful login.

  If this parameter is set to 0, only the hash type specified by the password_hash parameter is available. All previously set passwords are effectively invalidated.

  The default value is 1, which is intended to support a graceful transition to a new hash type over a period of time.

• bcrypt_cost

  This parameter controls cost of hash stretching by bcrypt hash function. Available value is a positive integer less than or equal to 99. 12 is used by default.

Upgrading password storage on earlier version

If you are planning to upgrade Sympa, you may have to upgrade password storage. Check "Upgrading notes" to know if upgrading is possible.

To perform upgrade, basically:

1. Stop web interface (See also "Stopping services").

2. Update Sympa configuration. See "Sympa configuration" and "Requirements" for details.

3. Run upgrade_sympa_password.pl:

   # upgrade_sympa_password.pl
   

4. Restart web interface (See also "Starting services").

Upgrading on large site

A note for sites with thousands of users that intend to upgrade to the bcrypt password hashes.

The bcrypt algorithm is designed to be CPU-intensive as a defense against password hash cracking. The default bcrypt_cost setting of 12 has been measured to consume approximately 250 milliseconds of CPU time on a typical 3.2GHz CPU. At that speed a site with 1000 users would take 250 seconds to upgrade hashes, while a site with 100,000 users would take nearly 7 hours.

If the estimated time required to upgrade passwords is a concern, it is possible to precalculate hashes in advance. (This process is only advised for large Sympa installations with small upgrade windows.)

• Create an alternate configuration file that uses the intended new hash, e.g. sympa.conf.bcrypt

  # cp -p /etc/sympa/sympa.conf /etc/sympa/sympa.conf.bcrypt
  

• Run upgrade_sympa_password.pl using the intended new config file. The --cache option specifies the path where hashes will be stored, and the --noupdateuser option prevents updating the user database.

  # upgrade_sympa_password.pl --config /etc/sympa/sympa.conf.bcrypt \
                              --cache /root/sympa.hashes \
                              --noupdateuser >&/tmp/precalc.log
  

• During the final upgrade, put the new config file in place and use the precalculated hashes to save time:

  # cp -p /etc/sympa/sympa.conf /etc/sympa/sympa.conf.old
  # cp -p /etc/sympa/sympa.conf.bcrypt /etc/sympa/sympa.conf
  # upgrade_sympa_password.pl --cache /root/sympa.hashes >& /tmp/upgrade.log
  

• Remember to remove the precalculated hashes once done with them.

  # rm /root/sympa.hashes
  

History of password storage format of Sympa

On very early versions of Sympa, passwords of users were stored in database table as plain text.

As of Sympa 3.1 (2001), passwords were stored as encrypted form with RC4 reversible encryption algorithm.

Sympa 6.0 (2009) adopted MD5 digest algorithm for newly created password.

Sympa 6.2.26 (2018) adopted bcrypt hash function using randomly generated salt.