Tuesday, 9 September 2014

SASL/DIGEST-MD5 with OpenLDAP-2.4.39

In order to authenticate users with Digest-MD5 the first choice to do is either store passwords in a file (sasldb2) on ldap server or into directory. The olcSaslAuxprops attribute in cn=config defines the path to follow.

Passwords in salsdb2

Start with:
sudo apt-get install sasl2-bin
than create a user:
sudo saslpasswd2 -c francesco
(script prompts for password and confirm password)
sudo chown openldap /etc/sasldb2
Modify cn=config with the following:
dn: cn=config
changetype: modify
replace: olcSaslAuxprops
olcSaslAuxprops: sasldb
create a map for the user:
dn: cn=config
changetype: modify
delete: olcAuthzRegexp
olcAuthzRegexp: "uid=francesco,cn=digest-md5,cn=auth" "cn=joe,dc=example,dc=org"
The entry cn=joe,dc=example,dc=org can be created later, or not created at all, if you simply need a principal to fulfill a ACL rule.
Restart OpenLDAP in order to apply olcAuthzRegexp (required by mine experience on Debian, OpenLDAP-2.4.39).
Test with:
ldapwhoami -U francesco -H ldapi:/// -Y DIGEST-MD5
SASL/DIGEST-MD5 authentication started
Please enter your password: 
SASL username: francesco
SASL data security layer installed.
Type the password choosed in the saslpasswd2 step. If by chance you are logged is as 'francesco', the -U francesco switch can be omitted.

Passwords in directory

Create the joe user:
dn: cn=joe,dc=unimore,dc=it
objectClass: inetOrgPerson
cn: joe
sn: user
uid: joe
description: Just plain Joe
userPassword: joesecret
Rollback the olcSaslAuxprops if you changed it (if not, this step is not necessary as it is the default):
dn: cn=config
changetype: modify
replace: olcSaslAuxprops
olcSaslAuxprops: slapd
Add the olcAuthzRegexp rules to map the MD5-DIGEST username to a directory entry, and you are ready:
ldapwhoami -U francesco -H ldapi:/// -Y DIGEST-MD5
then type the joe's password (joesecret in this example).
  • "client response doesn't match what we generated (tried bogus)" means you typed the wrong password.
  • "generic failure: unable to canonify user and get auxprops" could be either userPassword is not CLEARTEXT or userPassword is not readable by joe user (because of ACLs).
You are not going to do much with MD5-DIGEST without reading: OpenLDAP docs about Mapping Authentication Identities

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