Difference between revisions of "Client certificate authentication ipa"
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We can use [http://www.freeipa.org/page/V4/User_Certificates user certificates] to authenticate our ldap session. | We can use [http://www.freeipa.org/page/V4/User_Certificates user certificates] to authenticate our ldap session. | ||
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</pre> | </pre> | ||
− | == | + | == perl5 example == |
you need the perl-LDAP and perl-IO-Socket-SSL packages for this (fedora/rhel/centos). | you need the perl-LDAP and perl-IO-Socket-SSL packages for this (fedora/rhel/centos). | ||
<pre> | <pre> | ||
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</pre> | </pre> | ||
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+ | == disabling access to the user certificate == | ||
+ | if this certificate (or its key) has been compromised you need to disable its access to the directory. | ||
+ | |||
+ | * revoke it: | ||
+ | <pre> | ||
+ | ipa cert-revoke <serialnr> | ||
+ | </pre> | ||
+ | |||
+ | * remove the seeAlso attribute from the user account. | ||
+ | This is necessary because the DS apparently does not check the revocation status of the certificate. Having revoked it, I can still use it to access the ldap server. Removing the ldap value of seeAlso solves this problem. |
Latest revision as of 01:53, 5 March 2016
We can use user certificates to authenticate our ldap session.
Contents
generate user certificate for user account
Follow instructions in this blog.
Short version:
- create csr (certificate signing request).
I usually create a new directory and name it after the name of the user/host we want to create a certificate for. For user10, create a user10 folder.
Inside this folder, create a text file user10.inf like this:
[ req ] prompt = no encrypt_key = no distinguished_name = dn req_extensions = exts [ dn ] commonName = "user10" [ exts ] subjectAltName=email:user10@yourdomain.tld
- generate a key:
openssl genrsa -out user10.key 2048
- generate the csr:
openssl req -new -key user10.key -out user10.csr -config user10.inf
- verify csr:
openssl req -in user10.csr -text -noout Certificate Request: Data: Version: 0 (0x0) Subject: CN=user10 Subject Public Key Info: Public Key Algorithm: rsaEncryption Public-Key: (2048 bit) Modulus: 00:c2:d2:0c:44:c8:e3:8b:d7:e5:bc:b6:5d:fc:cf: xxxxx Exponent: 65537 (0x10001) Attributes: Requested Extensions: X509v3 Subject Alternative Name: email:user10@yourdomain.tld Signature Algorithm: sha1WithRSAEncryption 05:7b:a7:51:1e:28:25:8d:78:fb:d9:08:43:6d:54:51:db:10: xxxxxxxxxxxxxxxxxxxxx
- request the certificate (as the user self or as an admin user):
$ ipa cert-request user10.csr --principal user10 ....
If everything goes according to plan, you know have a certificate coupled to the user account
$ ipa user-show user10 User login: user10 First name: ipa Last name: user Home directory: /home/user10 Login shell: /bin/sh Email address: user10@yourdomain.tld UID: 1076200013 GID: 1076200013 Certificate: MIIEMjCCAxqgAwIBAgIBDjANBgkqhkiG9w0BAQsFADA5MRcwFQYDVQQKDA5VTklYxxxxxxxxxxxxxxxxxxxxxxxxxxxx== Account disabled: False Password: True Member of groups: ipausers Kerberos keys available: True
- retrieve the certificate:
first we need to get the certificate's serial number.
ipa cert-find ... Serial number (hex): 0xE Serial number: 14 Status: VALID Subject: CN=user10,O=YOURDOMAIN.TLD <pre> So, number 14. <pre> ipa cert-show 14 --out user10.pem
- eventually, verify certificate:
openssl x509 -in user10.pem -noout -text
which will give you all the certificate output on screen.
map certificate to user account
Canonical info:
http://directory.fedoraproject.org/docs/389ds/howto/howto-certmapping.html
- verify /etc/dirsrv/slapd-INSTANCE-NAME/certmap.conf looks like this:
certmap default default #default:DNComps #default:FilterComps e, uid #default:verifycert on #default:CmapLdapAttr certSubjectDN #default:library <path_to_shared_lib_or_dll> #default:InitFn <Init function's name> default:DNComps default:FilterComps uid certmap ipaca CN=Certificate Authority,O=SUB.DOMAIN.TLD ipaca:CmapLdapAttr seeAlso ipaca:verifycert on
As you see, there is a 'default' mapping and an 'ipaca' mapping.
WARNING!!!
Do not modify anything of the ipaca mapping unless you know what you are doing. You risk messing up your pki tomcat service and plenty of things will stop working.
WARNING!!!
As you see, the ipaca mapping is your ipa server PKI. It has a CmapLdapAttr mapping attribute to the ldap object attribute seeAlso.
When I searched a test ipa environment, the only account with a seeAlso attribute was the "DN: uid=pkidbuser,ou=people,o=ipaca" user, with this value: "CN=CA Subsystem,O=SUB.DOMAIN.TLD" (substitute O=SUB.DOMAIN.TLD with your own REALM name, obviously). This is an internal ipa user, do not modify it! We cannot modify this mapping or the PKI subsystem will stop working.
So the solution is quite simple. We need to populate the seeAlso attribute of the user10 account with this value:
cn=user10,o=SUB.DOMAIN.TLD
You can add this value to the seeAlso attribute using your favourite ldap client, like the very nice apache ds studio
configure ldap client
we can easily test this using ldapsearch. We need to set two environment variables in ~/.ldaprc:
TLS_CERT /path/to/user10.pem TLS_KEY /path/to/user10.key
And now search:
$ ldapsearch -h kdc.domain.tld -ZZ -Y EXTERNAL objectclass=person -s sub -b dc=sub,dc=domain,dc=tld cn ... # search result search: 3 result: 0 Success # numResponses: 1002 # numEntries: 1001
And in the log files (/var/log/dirsrv/slapd-INSTANCE-NAME/access) of the ldap server we see this:
[04/Mar/2016:23:34:57 +0100] conn=100 fd=111 slot=111 connection from 192.168.0.124 to 192.168.5.10 [04/Mar/2016:23:34:57 +0100] conn=100 op=0 EXT oid="1.3.6.1.4.1.1466.20037" name="startTLS" [04/Mar/2016:23:34:57 +0100] conn=100 op=0 RESULT err=0 tag=120 nentries=0 etime=0 [04/Mar/2016:23:34:57 +0100] conn=100 TLS1.2 256-bit AES; client CN=user10,O=SUB.DOMAIN.TLD issuer CN=Certificate Authority,O=SUB.DOMAIN.TLD [04/Mar/2016:23:34:57 +0100] conn=100 TLS1.2 client bound as uid=user10,cn=users,cn=accounts,dc=sub,dc=domain,dc=tld [04/Mar/2016:23:34:57 +0100] conn=100 op=1 BIND dn="" method=sasl version=3 mech=EXTERNAL [04/Mar/2016:23:34:57 +0100] conn=100 op=1 RESULT err=0 tag=97 nentries=0 etime=0 dn="uid=user10,cn=users,cn=accounts,dc=sub,dc=domain,dc=tld" [04/Mar/2016:23:34:57 +0100] conn=100 op=2 SRCH base="dc=sub,dc=domain,dc=tld" scope=2 filter="(objectClass=person)" attrs="cn" [04/Mar/2016:23:34:57 +0100] conn=100 op=2 RESULT err=0 tag=101 nentries=1001 etime=0
perl5 example
you need the perl-LDAP and perl-IO-Socket-SSL packages for this (fedora/rhel/centos).
#!/usr/bin/env perl use strict; use warnings; use utf8; use Net::LDAP; my $base = "dc=sub,dc=domain,dc=tld"; my $ldap = Net::LDAP->new( 'kdc.sub.domain.tld', debug => 0 ) || die "$@"; my $msg = $ldap->start_tls( verify => 'require', sslversion => 'tlsv1', clientcert => "/path/to/user10.pem", clientkey => "/path/to/user10.key", ); $msg->code && warn "could not starttls: " . $msg->error; # no bind needed, we are already authenticated! my $search = $ldap->search( base => $base, scope => "sub", filter => "(objectclass=person)", attrs => [ 'uid', ], ); $search->code && warn "failed to get persons: " . $search->error; print "found " . $search->count . " persons\n"; for my $entry ( $search->entries ) { print $entry->get_value('uid'), "\n"; print $entry->dn, "\n"; }
disabling access to the user certificate
if this certificate (or its key) has been compromised you need to disable its access to the directory.
- revoke it:
ipa cert-revoke <serialnr>
- remove the seeAlso attribute from the user account.
This is necessary because the DS apparently does not check the revocation status of the certificate. Having revoked it, I can still use it to access the ldap server. Removing the ldap value of seeAlso solves this problem.