adelton

mod_lookup_identity

Apache module to lookup user and retrieve additional information about the authenticated user.

Download mod_lookup_identity-0.9.8.tar.gz, the latest release. See the source repository.

The module supports lookup of the user identifier based on certificate via SSSD D-Bus call org.freedesktop.sssd.infopipe.Users.FindByCertificate, setting up the r->user request structure.

It also allows retrieval of list of group names the user belongs to using org.freedesktop.sssd.infopipe.GetUserGroups call and any custom attributes configured in /etc/sssd/sssd.conf using with org.freedesktop.sssd.infopipe.GetUserAttr call. It also retrieves the GECOS information using the getpwnam call. The retrieved values get stored in notes/environment variables.

The sssd-dbus package needs to be installed and the ifp service enabled in the [sssd] section of /etc/sssd/sssd.conf.

The module needs to be loaded into Apache's configuration file like /etc/httpd/conf/httpd.conf with directive like

LoadModule lookup_identity_module modules/mod_lookup_identity.so

User Lookup

By default, no user identifier lookup is enabled. Directive

LookupUserByCertificate On
enables the lookup. It uses the original internal r->user value as input, so the typical setup for example with mod_ssl will be
SSLVerifyClient require
SSLUserName SSL_CLIENT_CERT
LookupUserByCertificate On
when mod_ssl puts the certificate to the username field and then mod_lookup_identity replaces it with user identifier found with org.freedesktop.sssd.infopipe.Users.FindByCertificate. If no user is found based on the certificate, the r->user value is cleared. Make sure the FakeBasicAuth is not enable in SSLOptions or the r->user will not be set.

SSSD version 1.13 or higher is needed for LookupUserByCertificate functionality.

Retrieving Group Membership and Attributes

For the custom attributes fetching, caching of non-POSIX attributes needs to be enabled in the [domain/*] section of /etc/sssd/sssd.conf, configuration ldap_user_extra_attrs, and the attributes also need to be enabled in the [ifp] section using the user_attributes configuration option.

Example of sssd.conf:

[domain/example.com]
...
ldap_user_extra_attrs = mail, telephoneNumber, givenname, sn

[sssd]
services = nss, pam, ssh, ifp

[ifp]
allowed_uids = apache, root
user_attributes = +mail, +telephoneNumber, +givenname, +sn

The default behaviour can be changed with the following directives:

LookupOutput where_to_store_results

Specifies if the lookups will be done at all and where the results of the lookup will be stored. Possible values are:

  • None: Disable the lookup altogether
  • Notes: Sets the Apache notes table only
  • Env: Sets environment variables only
  • Headers: Sets HTTP request headers, for use by proxy setups
  • Headers-Base64: Sets HTTP request headers with values Base64-encoded, for use by proxy setups

The default is Notes and Env.

LookupUserGECOS name

Name of the note and/or environment variable for the GECOS value. If prefixed with '+' sign, it is set only if the note/environment variable is not set yet, otherwise the value is overwritten.

Example:

LookupUserGECOS REMOTE_USER_FULLNAME

Example:

LookupUserGECOS +REMOTE_USER_GECOS

Default is REMOTE_USER_GECOS.

LookupUserGroups name [separator]

Name of the note and/or environment variable for the list of groups retrieved using the org.freedesktop.sssd.infopipe.GetUserGroups call, and optionally separator for multiple groups.

If the separator is specified, it is used to concatenate multiple groups in single string value of the note/environment variable. If the separator is not specified, only one group is set.

Example: if user alice is member of groups staff and student, option

LookupUserGroups REMOTE_USER_GROUPS :
will set value of REMOTE_USER_GROUPS to staff:student (or student:staff, depending on the order returned by the sssd dbus call). If the option is
LookupUserGroups REMOTE_USER_GROUPS
the value will be either staff or student (the first in the list returned by the sssd dbus call; order not to be relied on).

When

LookupOutput headers-base64
is specified, the values are encoded individually and then concatenated. For the staff and student values example,
LookupUserGroups REMOTE-USER-GROUPS :
will produce c3RhZmY=:c3R1ZGVudA==.

When prefixed with '+' sign and the note/environment variable already has some value set, behaviour differs depending on whether the optional separator is specified or not. If it is, the string with separator-separated values is appended after separator to existing value. If separator is not specified, existing value is preserved.

Example: when user alice is member of groups staff and student, and the environment variable REMOTE_USER_GROUPS already has value anonymous set (by Apache configuration or by some module that was invoked before mod_lookup_identity), directive

LookupUserGroups +REMOTE_USER_GROUPS :
will set the value to anonymous:staff:student (or anonymous:student:staff). On the other hand,
LookupUserGroups +REMOTE_USER_GROUPS
would leave the value unchanged at anonymous.

By default, groups are not retrieved.

LookupUserGroupsIter name

The number of groups the user is a member of (as returned by the org.freedesktop.sssd.infopipe.GetUserGroups call) will be stored in note/environment variable <name>_N and individual values in <name>_1 .. <name>_<<name>_N>. This allows for safe retrieval of groups without the separator clashing with the values.

Example: if user alice is member of groups staff and student, optio

LookupUserGroupsIter REMOTE_USER_GROUP
will set
  • REMOTE_USER_GROUP_N=2
  • REMOTE_USER_GROUP_1=staff
  • REMOTE_USER_GROUP_2=student
(or the values of REMOTE_USER_GROUP_1 and REMOTE_USER_GROUP_2 will be flipped).

When

LookupOutput headers-base64
is specified and assuming
LookupUserGroupsIter REMOTE-USER-GROUP
the HTTP header values will be
  • REMOTE-USER-GROUP-N=2
  • REMOTE-USER-GROUP-1=c3RhZmY=
  • REMOTE-USER-GROUP-2=c3R1ZGVudA==

Note that the numerical <name>_N is not Base64-encoded.

If user is not a member of any group, the <name>_N value will be set to 0.

When the name is prefixed with '+' sign, existing values are preserved and new values added to the list. Thus, if alice is member of groups staff and student and REMOTE_USER_GROUP_N already has value 2 set and the directive is

LookupUserGroupsIter +REMOTE_USER_GROUP
the module will set values of REMOTE_USER_GROUP_3 and REMOTE_USER_GROUP_4 and will update REMOTE_USER_GROUP_N to value 4. The module will however not check/fix the consistency of existing values; if REMOTE_USER_GROUP_N is set to value 2 prior to invocation of mod_lookup_identity, it will not check if REMOTE_USER_GROUP_1 and REMOTE_USER_GROUP_2 are set to match REMOTE_USER_GROUP_N.

By default, groups are not retrieved.

LookupUserAttr the_attribute name [separator]

Name of the attribute to be retrieved using the org.freedesktop.sssd.infopipe.GetUserAttr call and name of the note and/or environment variable where the value will be stored, and optionally separator for multivalued results.

If the separator is specified, it is used to concatenate multiple values in single string value of the note/environment variable. If the separator is not specified, only one value is set.

Example:

LookupUserAttr mail REMOTE_USER_MAIL
will retrieve one value from the mail attribute (from potentially multivalued attribute) and store them to note/environment variable REMOTE_USER_MAIL.

Directive

LookupUserAttr mail REMOTE_USER_MAIL ", "
will retrieve all the values and store them as comma-separated string. The same way as with LookupUserGroups, headers-base64 will first Base64 encode and then concatenate.

When the name is prefixed with '+' sign, similar to LookupUserGroups it will only set the value if not set yet, or append to existing value if separator is specified: when

LookupUserAttr team +REMOTE_USER_TEAMS ", "
is configured and REMOTE_USER_ORGS is already set to IT and the sssd dbus returned values Helpdesk and Support, the resulting value will be IT, Helpdek, Support.

Multiple LookupUserAttr lines can be used to retrieve multiple attributes.

By default, no user attributes are retrieved.

LookupUserAttrIter the_attribute name

The number of attribute values for the user (as returned by the org.freedesktop.sssd.infopipe.GetUserAttr call) will be stored in note/environment variable <name>_N and individual values in <name>_1 .. <name>_<<name>_N>. This allows for safe retrieval of multivalued attributes without the separator clashing with the values.

Example: if user alice has multivalued custom attribute office_no with values M314 and P005,

LookupUserAttrIter office_no REMOTE_USER_OFFICE
will cause the following notes/environment variables to be set:
  • REMOTE_USER_OFFICE_N=2
  • REMOTE_USER_OFFICE_1=M314
  • REMOTE_USER_OFFICE_2=P005

When the '+' sign is used, behaviour matches the behaviour of LookupUserGroupsIter -- the list formed by _N and _# variables is appended to.

Multiple LookupUserAttr lines can be used to retrieve multiple attributes.

By default, no user attributes are retrieved.

LookupDbusTimeout miliseconds
Default: 5000 (== 5 s).

Please note that LookupUserGroups and LookupUserGroupsIter, as well as LookupUserAttr and LookupUserAttrIter for single attribute can be configured with the same note/environment variable name. For example,

LookupUserGroups REMOTE_USER_GROUPS :
LookupUserGroupsIter REMOTE_USER_GROUP
can be set at the same time and for user with two groups, all the following values will be set:
  • REMOTE_USER_GROUPS=staff:student
  • REMOTE_USER_GROUP_N=2
  • REMOTE_USER_GROUP_1=staff
  • REMOTE_USER_GROUP_2=student

Building from sources

When building from sources, command

apxs -i -a -c $(pkg-config --cflags dbus-1) $(pkg-config --libs dbus-1) \
    -Wc,"-Wall -pedantic -std=c99" mod_lookup_identity.c
should build and install the module.

If the available version of sssd does not provide or is not configured to provide the ifp dbus service, compile with

apxs -DNO_USER_ATTR -i -a -c -Wc,"-Wall -pedantic -std=c99" mod_lookup_identity.c
In that case, the LookupUserAttr functionality will not be compiled in and will not be available.

License

Copyright 2013--2016 Jan Pazdziora

Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
You may obtain a copy of the License at

    http://www.apache.org/licenses/LICENSE-2.0

Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or
implied.
See the License for the specific language governing permissions and
limitations under the License.