Grok LDAP fast
(presented on 2004-06-09)
LDAP presents a distributed tree of information
Writing things down: LDIF
dn: gn=John+sn=Doe,ou=Research & Development,ou=Pe ople,dc=example,dc=com objectClass: addressbookPerson gn: John sn: Doe street: Back alley postOfficeBox: 123 postalCode: 54321 postalAddress: Backstreet st: NY l: New York City c: US
Writing things down: LDIF (2)
dn: gn=John+sn=Smith,ou=Marketing,ou=People, dc=example,dc=com objectClass: addressbookPerson gn: John sn: Smith telephoneNumber: 555-1234 facsimileTelephoneNumber: 555-1235 description: This is a description that can span multi ple lines as long as the non-first lines are inden ted in the LDIF.
Object-oriented look at LDAP entries
A lot of similarities with OO programming languages, but some big differences, too.
An LDAP entry corresponds with an object.
Whereas object are usually instances of a single class, LDAP entries can "implement" multiple objectClasses.
objectClasses can inherit zero, one or many objectClasses, just like programming classes.
objectClasses have a root class, known as
top; many object oriented programming languages have a root class, e.g. named
objectClasses are either
AUXILIARY; entries can only implement one
The objectClasses of an entry can be changed at will; you only need to take care that the entry has all the
MUSTattribute types, and no attribute types outside of the ones that are
Note that e.g. OpenLDAP doesn't implement this.
- Attributes of an entry closely match attributes of objects in programming languages; however, LDAP attributes may have multiple values.
The base DN for the search
A search filter, specifying criteria an entry must fulfill to match.
Scope of the search, either look at the base DN only, only look one level below it, or look at the whole subtree rooted at the base DN.
Size limit of at most how many matching entries to return.
Attributes to return, or none for all attributes the matching entries happen to have.
An example search filter:
Phases of the protocol chat
- Open and bind
- Search (possibly many times)
- Unbind and close
Opening and binding
Doing a search
Doing multiple searches
Unbinding and closing
A complex search filter
(&(objectClass=person) (!(telephoneNumber=*)) (|(cn=*a*b*)(cn=*b*a*)))
objectClasslists all the objectclasses an LDAP entry manifests.
- what attributetypes an entry MUST have
- what attributetypes an entry MAY have
An entry in a phonebook must have a name and a telephone number, and may have a fax number and street address.
a configuration file included in the LDAP server configuration.
a combination of attribute type and object class definitions.
stored as plain text
can be requested over an LDAP connection
attributetype ( 22.214.171.124 NAME ( 'sn' 'surname' ) DESC 'RFC2256: last (family) name(s) for which the entity is known by' SUP name )
Can also contain
- content data type
- comparison and sort mechanism
- substring search mechanism
- whether multiple values are allowed
objectclass ( 126.96.36.199 NAME 'person' DESC 'RFC2256: a person' SUP top STRUCTURAL MUST ( sn $ cn ) MAY ( userPassword $ telephoneNumber $ seeAlso $ description ) )
- Anyone can create their own schema
- Need to be globally unique
- But try to use already existing ones