RFC_6594_SSHFP_DNS_records#

__NOTOC__

#2642 Add support for enhanced SSHFP DNS records per RFC 6594

Overview#

IPA supports automatic update of SSHFP DNS records for managed hosts in the ipa-client-install script and in host-* commands. The support is currently limited to the original SSHFP specification from RFC 4255; SSHFP records generated by IPA contain SHA-1 fingerprints of RSA and DSS host keys.

Recently, RFC 6594 was released. It extends the original SSHFP specification with support for SHA-256 fingerprints and ECDSA host keys.

Add support for RFC 6594 SSHFP records to IPA, generate both SHA-1 and SHA-256 fingerprints for RSA, DSS and ECDSA host keys.

Use Cases#

Automatic generation of SSHFP DNS records on IPA client install:

# ipa-client-install
Discovery was successful!
Hostname: host1.example.com
Realm: EXAMPLE.COM
DNS Domain: example.com
IPA Server: ipa.example.com
BaseDN: dc=example,dc=com
Continue to configure the system with these values? [no]: yes
User authorized to enroll computers: admin
Synchronizing time with KDC...
Password for admin@EXAMPLE.COM:
Enrolled in IPA realm EXAMPLE.COM
Created /etc/ipa/default.conf
New SSSD config will be created
Configured /etc/sssd/sssd.conf
Configured /etc/krb5.conf for IPA realm EXAMPLE.COM
| ``trying ``\ ```https://ipa.example.com/ipa/xml`` <https://ipa.example.com/ipa/xml>`__
Hostname (host1.example.com) not found in DNS
DNS server record set to: host1.example.com -> 192.168.1.1
Adding SSH public key from /etc/ssh/ssh_host_rsa_key.pub
Adding SSH public key from /etc/ssh/ssh_host_dsa_key.pub
Forwarding 'host_mod' to server u'``\ ```https://ipa.example.com/ipa/xml`` <https://ipa.example.com/ipa/xml>`__\ ``'
SSSD enabled
Configured /etc/openldap/ldap.conf
NTP enabled
Configured /etc/ssh/ssh_config
Configured /etc/ssh/sshd_config
Client configuration complete.

$ dig host1.example.com SSHFP +short
2 0E04A7E09D037934492108ED5590612416BE736AD1BCAEAE1EA4148E 80C956E2
1 F2A1353FF919AD785B6BD42B588F6236D1F67459
2 3E475EEAF17975C36EE1413DDD659275FDD19C97C2C74A3651BA12F7 52E12A18
1 A308B1B02A8B43CB5192E26FA50280F752BB3A14

Automatic generation of SSHFP DNS records when modifying a host:

$ ipa host-mod host2.example.com --updatedns --sshpubkey='ssh-rsa ``\ ``' --sshpubkey='ssh-dss ``\ ``' --sshpubkey='ecdsa-sha2-nistp256 ``\ ``'
---------------------------------------------
Modified host "host2.example.com"
---------------------------------------------
  Host name: host2.example.com
  Principal name: host/host2.example.com@EXAMPLE.COM
  MAC address: 00:11:22:33:44:55
  SSH public key: ecdsa-sha2-nistp256 ``\ ``,
                  ssh-dss ``\ ``,
                  ssh-rsa
  Keytab: True
  Managed by: host2.example.com
  SSH public key fingerprint: 6C:9F:07:51:63:36:32:8B:ED:CF:8C:4C:5F:F2:BF:AE (ecdsa-sha2-nistp256),
                              07:5D:0D:55:64:62:A3:FE:02:AE:FC:CD:F6:ED:E1:D9 (ssh-dss),
                              8C:C3:27:A8:40:9F:80:01:61:99:D2:25:55:A3:52:30 (ssh-rsa)

$ dig host2.example.com SSHFP +short
2 43FFD792089442F08892CA753059FD8B7FA939E990CE4687A3D1FB75 E0B8F6DE
1 4C2C50EDEAE6BC6107A37EAE7A05694C15CFEC53
1 B1D733A262E29B44A4D8A9FAF4B3B9E78302D1DB
2 E5382308CFD60DE4F0ACF3BCB0366314EECFC71030A28AAF75280041 5FDF81A8
2 545055E921E94128AF6BFE68E6E2804333628F7808B8EAE10E297B11 3270862F
1 DA7A6687AE4B2C242E12A67DACDC67D26E374AD5

Design#

Implement support for SHA-256 fingerprints and ECDSA keys in SSHFP records in the ipapython.ssh module (add new method fingerprint_dns_sha256).

Extend ipa-client-install and the host plugin to add all types of SSHFP records to DNS.

Implementation#

N/A

Feature Managment#

N/A

Major configuration options and enablement#

N/A

Replication#

N/A

Updates and Upgrades#

N/A

Dependencies#

N/A

External Impact#

N/A

RFE Author#

Jan Cholasta

RFC_6594_SSHFP_DNS_records

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