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R. Wambacher
Asked: 2016-11-09 22:32:10 +0800 CST

Apache user authentication based on LDAP group memberships not working

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i would like to auhenticate and authorize all users of one LDAP group (ApacheDS 2.0.0-20 on Windows, using multiple uniqueMember attributes in the group and the "Require ldap-group" statement in httpd config) for access to a web ressource.

The user which tries to authenticate is also part of this LDAP group and is authorized if i use the "Require valid-user" statement instead of "Require ldap-group" in httpd config.

Setup:

  • Linux based Apache 2.4.23 (from OpenSuse 42.1 Apache Repository)
  • LDAP: MS windows based ApacheDS 2.0.0-20

Group configuration in ApacheDS LDAP:

LDAP group configuration

Excerpt of configuration of httpd:

<AuthnProviderAlias ldap ldapconfig>
        LDAPReferrals Off
        AuthLDAPBindDN "cn=query,ou=users,o=WJWext"
        AuthLDAPBindPassword secretpassword
        AuthLDAPURL "ldap://ldap.hostname:10389/o=WJWext?uid?sub"
</AuthnProviderAlias>

...
LogLevel trace7

<Location /xy>
...
        AuthType Basic
        AuthName "xy"
        AuthBasicProvider ldapconfig
        AuthLDAPGroupAttributeIsDN on
        AuthLDAPGroupAttribute uniqueMember
        AuthLDAPMaxSubGroupDepth 0
        AuthLDAPSubGroupClass groupOfUniqueNames
        Require ldap-group cn=groupname,ou=groups,o=WJWext
...
</Location>

The log file of httpd shows that the user can be authenticated but is not authorized by group:

[Tue Nov 08 21:44:23.601378 2016] [authz_core:debug] [pid 15148] mod_authz_core.c(809): [client a.b.c.d:59427] AH01626: authorization result of Require ldap-group cn=groupname,ou=groups,o=WJWext)
[Tue Nov 08 21:44:23.601415 2016] [authz_core:debug] [pid 15148] mod_authz_core.c(809): [client a.b.c.d:59427] AH01626: authorization result of <RequireAny>: denied (no authenticated user yet)
[Tue Nov 08 21:44:23.601547 2016] [authnz_ldap:debug] [pid 15148] mod_authnz_ldap.c(516): [client a.b.c.d:59427] AH01691: auth_ldap authenticate: using URL ldap://ldap.hostname:10389/o=WJWext?uid?sub
[Tue Nov 08 21:44:23.601590 2016] [authnz_ldap:trace1] [pid 15148] mod_authnz_ldap.c(537): [client a.b.c.d:59427] auth_ldap authenticate: final authn filter is (&(objectclass=*)(uid=hudson))
[Tue Nov 08 21:44:23.615090 2016] [ldap:trace5] [pid 15148] util_ldap.c(1843): [client a.b.c.d:59427] LDC 55e4b4a94070 used for authn, must be rebound
[Tue Nov 08 21:44:23.615236 2016] [authnz_ldap:debug] [pid 15148] mod_authnz_ldap.c(613): [client a.b.c.d:59427] AH01697: auth_ldap authenticate: accepting hudson
[Tue Nov 08 21:44:23.615410 2016] [authz_core:debug] [pid 15148] mod_authz_core.c(809): [client a.b.c.d:59427] AH01626: authorization result of Require ldap-group cn=groupname,ou=groups,o=WJWext:denied

What is somewhat surprising: In the log files and looking at a network traffic trace it seems that there's no search request for gathering the group membership of the user.

Is there any idea what we are doing wrong?

ldap httpd apache-2.4 mod-auth-ldap

1 Answers

  1. In answer to the bounty comment/request, here's the minimum Apache configuration that uses AD authentication and requires group membership, tested on RHEL 7.x which is using mod_authnz_ldap:

    <Directory "/some/path/">
  AuthType Basic
  AuthName "Top Secret"
  AuthBasicProvider ldap
  AuthLDAPURL "ldaps://example.com/dc=EXAMPLE,dc=COM?sAMAccountname"
  AuthLDAPBindDN "CN=apache,OU=Accounts,DC=example,DC=com"
  AuthLDAPBindPassword "password"
  AuthLDAPMaxSubGroupDepth 0
  AuthLDAPSubGroupAttribute member
  AuthLDAPSubGroupClass group
  Require ldap-group CN=example,OU=Groups,DC=example,DC=com
</Directory>

    Tweaking the AuthLDAPMaxSubGroupDepth allows me to use groups that have nested membership but when set to 0 requires my user to be an immediate member of the necessary group.

    In addition to the logs the OP posted, I see this instead of the failure:

    AH01697: auth_ldap authenticate: accepting user
AH01713: auth_ldap authorize: require group: testing for group membership in "CN=example,OU=Groups,DC=example,DC=com"
AH01714: auth_ldap authorize: require group: testing for member: CN=User Name,OU=Accounts,DC=example,DC=com (CN=example,OU=Groups,DC=example,DC=com)
AH01715: auth_ldap authorize: require group: authorization successful (attribute member) [Comparison true (cached)][6 - Compare True]
AH01626: authorization result of Require ldap-group CN=example,OU=Groups,DC=example,DC=com: granted
AH01626: authorization result of <RequireAny>: granted

    Edit: I managed to reproduce the problem using the provider alias syntax, I believe the OP is missing an <AuthzProviderAlias ...> block. I rejigged my example config to look like this:

    <AuthnProviderAlias ldap myldap>
  AuthLDAPURL "ldaps://example.com/dc=EXAMPLE,dc=COM?sAMAccountname"
  AuthLDAPBindDN "CN=apache,OU=Accounts,DC=example,DC=com"
  AuthLDAPBindPassword "password"
</AuthnProviderAlias>

<AuthzProviderAlias ldap-group ldap-group-alias "CN=example,OU=Groups,DC=example,DC=com">
  AuthLDAPURL "ldaps://example.com/dc=EXAMPLE,dc=COM"
  AuthLDAPBindDN "CN=apache,OU=Accounts,DC=example,DC=com"
  AuthLDAPBindPassword "password"
  AuthLDAPMaxSubGroupDepth 0
  AuthLDAPSubGroupAttribute member
  AuthLDAPSubGroupClass group
</AuthzProviderAlias>

<Directory "/some/path/">
  AuthType Basic
  AuthName "Top Secret"
  AuthBasicProvider myldap
  Require ldap-group-alias
</Directory>

    This also works, but you end up duplicating the URL, bind DN & password.

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