Configure LSC on Cisco IP Phone with CUCM

Note: It also only pertains to phones that support SBD. For example, the 7940 and 7960 phones do not support SBD, nor do the 7935, 7936 and 7937 conference phones. For a list of devices that support SBD in your version of CUCM, navigate to Cisco Unified Reporting > System Reports > Unified CM Phone Feature List and run a report on Feature: Security By Default.

The information in this document was created from the devices in a specific lab environment. All of the devices used in this document started with a cleared (default) configuration. If your network is live, make sure that you understand the potential impact of any command.

Background Information

MICs versus LSCs

If you use certificate based authentication for 802.1X or Anyconnect Phone VPN, it is important to understand the difference between MICs and LSCs.

Every Cisco phone comes with a MIC pre-installed at the factory. This certificate is signed by one of the Cisco Manufacturing CA certificates, either by the Cisco Manufacturing CA, Cisco Manufacturing CA SHA2, CAP-RTP-001 or CAP-RTP-002 certificate. When the phone presents this certificate, it proves that it is a valid Cisco phone, but this does not validate that the phone belongs to a specific customer or CUCM cluster. It could potentially be a rogue phone purchased on the open market or brought over from a different site.

LSCs, on the other hand, are intentionally installed on phones by an administrator, and are signed by the CUCM Publisher's CAPF certificate. You would configure 802.1X or Anyconnect VPN to only trust LSCs issued by known CAPF certificate authorities. Basing certificate authentication on LSCs instead of MICs provides you with a much more granular control over which phone devices are trusted.

Configure

Network Topology

These CUCM lab servers were used for this document:

ao115pub - 10.122.138.102 - CUCM Publisher & TFTP server
ao115sub - 10.122.138.103 - CUCM Subscriber & TFTP server

Verify that the CAPF certificate has not expired, nor is about to expire in the near future. Navigate to Cisco Unified OS Administration > Security > Certificate Management, then Find Certificate List where Certificate is exactly CAPF as shown in the image.

Click Common Name in order to open the Certificate Details page. Inspect the Validity From: and To: dates in the Certificate File Data pane in order to determine when the certificate expires, as shown in the image.

If the CAPF certificate has expired, or is soon to expire, regenerate that certificate. Do not move forward with the LSC install process with an expired or soon to expire CAPF certificate. This avoids the need to reissue LSCs in the near future due to CAPF certificate expiration. For information about how to regenerate the CAPF certificate, refer the CUCM Certificate Regeneration/Renewal Process article.

Similarly, if you need to have your CAPF certificate signed by a third party Certificate Authority, you have a choice to make at this stage. Either complete the Certificate Signing Request (CSR) file generation and importation of the signed CAPF certificate now, or continue the configuration with a self-signed LSC for a preliminary test. If you need a third party signed CAPF certificate, it is generally sensible to configure this feature first with a self-signed CAPF certificate, test and verify, and then redeploy LSCs that are signed by a third party signed CAPF certificate. This simplifies later troubleshooting, if tests with the third party signed CAPF certificate fail.

Warning: If you regenerate the CAPF certificate or import a third-party signed CAPF certificate while the CAPF service is activated and started, phones are automatically reset by CUCM. Complete these procedures in a maintenance window when it is acceptable for phones to be reset. For reference, see CSCue55353 - Add warning when regenerating TVS/CCM/CAPF certificate that phones reset.

Note: If your CUCM version supports SBD, this LSC install procedure applies regardless if your CUCM cluster is set to mixed mode or not. SBD is a part of CUCM version 8.0(1) and later. In these versions of CUCM, the ITL files contains the certificate for the CAPF service on the CUCM Publisher. This allows phones to connect to the CAPF service in order to support certificate operations such as Install/Upgrade and Troubleshoot.

In the previous versions of CUCM, it was necessary to configure the cluster for Mixed Mode in order to support certificate operations. As this is no longer necessary, this reduces barriers to the use of LSCs as phone identity certificates for 802.1X authentication or for AnyConnect VPN client authentication.

Run the show itl command on all TFTP servers in the CUCM cluster. Observe that the ITL file does contains a CAPF certificate.

For example, here is an excerpt of the show itl output from the lab CUCM Subscriber ao115sub.

Note: There is an ITL Record entry in this file with a FUNCTION of CAPF.

Note: If your ITL file doesn't have a CAPF entry, log in to your CUCM publisher and confirm the CAPF service is activated. In order to confirm this, navigate to Cisco Unified Serviceability > Tools > Service Activation > CUCM Publisher > Security, then activate the Cisco Certificate Authority Proxy Function Service. If the service was deactivated and you just activated it, navigate to Cisco Unified Serviceability > Tools > Control Center – Feature Services > Server > CM Services, then restart the Cisco TFTP service on all TFTP servers in the CUCM cluster to regenerate the ITL file. Also, ensure that you do not hit CSCuj78330.

Note: After you're done, run the show itl command on all TFTP servers in the CUCM cluster in order to verify that the current CUCM Publisher CAPF certificate is now included in the file.

 ITL Record #:1
 ----
BYTEPOS TAG LENGTH VALUE
------- --- ------ -----
1 RECORDLENGTH 2 727
2 DNSNAME 2
3 SUBJECTNAME 64 CN=CAPF-7f0ae8d7;OU=TAC;O=Cisco Systems;L=Boxborough;ST=MA;C=US
4 FUNCTION 2 CAPF
5 ISSUERNAME 64 CN=CAPF-7f0ae8d7;OU=TAC;O=Cisco Systems;L=Boxborough;ST=MA;C=US
6 SERIALNUMBER 16 64:F2:FE:61:3B:79:C5:D3:62:E2:6D:AB:4A:8B:76:1B
7 PUBLICKEY 270
8 SIGNATURE 256
11 CERTHASH 20 C3 E6 97 D0 8A E1 0B F2 31 EC ED 20 EC C5 BC 0F 83 BC BC 5E
12 HASH ALGORITHM 1 null

 ITL Record #:2
 ----
BYTEPOS TAG LENGTH VALUE
------- --- ------ -----
1 RECORDLENGTH 2 717
2 DNSNAME 2
3 SUBJECTNAME 59 CN=ao115pub;OU=TAC;O=Cisco Systems;L=Boxborough;ST=MA;C=US
4 FUNCTION 2 TVS
5 ISSUERNAME 59 CN=ao115pub;OU=TAC;O=Cisco Systems;L=Boxborough;ST=MA;C=US
6 SERIALNUMBER 16 6B:99:31:15:D1:55:5E:75:9C:42:8A:CE:F2:7E:EA:E8
7 PUBLICKEY 270
8 SIGNATURE 256
11 CERTHASH 20 05 9A DE 20 14 55 23 2D 08 20 31 4E B5 9C E9 FE BD 2D 55 87
12 HASH ALGORITHM 1 null

 ITL Record #:3
 ----
BYTEPOS TAG LENGTH VALUE
------- --- ------ -----
1 RECORDLENGTH 2 1680
2 DNSNAME 2
3 SUBJECTNAME 71 CN=ITLRECOVERY_ao115pub;OU=TAC;O=Cisco Systems;L=Boxborough;ST=MA;C=US
4 FUNCTION 2 System Administrator Security Token
5 ISSUERNAME 71 CN=ITLRECOVERY_ao115pub;OU=TAC;O=Cisco Systems;L=Boxborough;ST=MA;C=US
6 SERIALNUMBER 16 51:BB:2F:1C:EE:80:02:16:62:69:51:9A:14:F6:03:7E
7 PUBLICKEY 270
8 SIGNATURE 256
9 CERTIFICATE 963 DF 98 C1 DB E0 61 02 1C 10 18 D8 BA F7 1B 2C AB 4C F8 C9 D5 (SHA1 Hash HEX)
This etoken was not used to sign the ITL file.

 ITL Record #:4
 ----
BYTEPOS TAG LENGTH VALUE
------- --- ------ -----
1 RECORDLENGTH 2 717
2 DNSNAME 2
3 SUBJECTNAME 59 CN=ao115sub;OU=TAC;O=Cisco Systems;L=Boxborough;ST=MA;C=US
4 FUNCTION 2 TVS
5 ISSUERNAME 59 CN=ao115sub;OU=TAC;O=Cisco Systems;L=Boxborough;ST=MA;C=US
6 SERIALNUMBER 16 65:E5:10:72:E7:F8:77:DA:F1:34:D5:E3:5A:E0:17:41
7 PUBLICKEY 270
8 SIGNATURE 256
11 CERTHASH 20 00 44 54 42 B4 8B 26 24 F3 64 3E 57 8D 0E 5F B0 8B 79 3B BF
12 HASH ALGORITHM 1 null

 ITL Record #:5
 ----
BYTEPOS TAG LENGTH VALUE
------- --- ------ -----
1 RECORDLENGTH 2 1652
2 DNSNAME 2
3 SUBJECTNAME 59 CN=ao115sub;OU=TAC;O=Cisco Systems;L=Boxborough;ST=MA;C=US
4 FUNCTION 2 System Administrator Security Token
5 ISSUERNAME 59 CN=ao115sub;OU=TAC;O=Cisco Systems;L=Boxborough;ST=MA;C=US
6 SERIALNUMBER 16 48:F7:D2:F3:A2:66:37:F2:DD:DF:C4:7C:E6:B9:CD:44
7 PUBLICKEY 270
8 SIGNATURE 256
9 CERTIFICATE 959 20 BD 40 75 51 C0 61 5C 14 0D 6C DB 79 E5 9E 5A DF DC 6D 8B (SHA1 Hash HEX)
This etoken was used to sign the ITL file.

 ITL Record #:6
 ----
BYTEPOS TAG LENGTH VALUE
------- --- ------ -----
1 RECORDLENGTH 2 1652
2 DNSNAME 2
3 SUBJECTNAME 59 CN=ao115sub;OU=TAC;O=Cisco Systems;L=Boxborough;ST=MA;C=US
4 FUNCTION 2 TFTP
5 ISSUERNAME 59 CN=ao115sub;OU=TAC;O=Cisco Systems;L=Boxborough;ST=MA;C=US
6 SERIALNUMBER 16 48:F7:D2:F3:A2:66:37:F2:DD:DF:C4:7C:E6:B9:CD:44
7 PUBLICKEY 270
8 SIGNATURE 256
9 CERTIFICATE 959 20 BD 40 75 51 C0 61 5C 14 0D 6C DB 79 E5 9E 5A DF DC 6D 8B (SHA1 Hash HEX)

 ITL Record #:7
 ----
BYTEPOS TAG LENGTH VALUE
------- --- ------ -----
1 RECORDLENGTH 2 1031
2 DNSNAME 9 ao115sub
3 SUBJECTNAME 62 CN=ao115sub-EC;OU=TAC;O=Cisco Systems;L=Boxborough;ST=MA;C=US
4 FUNCTION 2 TFTP
5 ISSUERNAME 62 CN=ao115sub-EC;OU=TAC;O=Cisco Systems;L=Boxborough;ST=MA;C=US
6 SERIALNUMBER 16 53:CC:1D:87:BA:6A:28:BD:DA:22:B2:49:56:8B:51:6C
7 PUBLICKEY 97
8 SIGNATURE 103
9 CERTIFICATE 651 E0 CF 8A B3 4F 79 CE 93 03 72 C3 7A 3F CF AE C3 3E DE 64 C5 (SHA1 Hash HEX)

The ITL file was verified successfully.

With the CAPF entry confirmed as an entry in the ITL, you can complete a certificate operation on a phone. In this example, a 2048 bit RSA certificate is installed by use of Null String authentication.

On the phone, verify that an LSC is not yet installed as shown in the image. For example, on a 79XX series phone, navigate to Settings > 4 - Security Configuration > 4 - LSC.

Open the phone configuration page for your phone. Navigate to Cisco Unified CM Administration > Device > Phone.

Enter these details to the CAPF Information section of the phone’s configuration, as shown in the image:

For Certificate Operation, select Install/Upgrade
For Authentication Mode, select By Null String
For this example, leave the Key Order, RSA Key Size (Bits) and EC Key Size (Bits) set to the system defaults.
For Operation Completes By, enter a date and time that is at least one hour in to the future.

Save your configuration changes, then Apply Config.

The LSC status on the phone changes to Pending as shown in the image.

The phone generates keys as shown in the image.

The phone resets, and when the reset completes, the phone LSC status changes to Installed as shown in the image.

This is also visible under Status Messages in the phone as shown in the image.

Verify

Use this section in order to confirm that your configuration works properly.

In order to verify LSC certificate installation on multiple phones, refer the Generate CAPF Report section of Security Guide for Cisco Unified Communications Manager, Release 11.0(1). Alternatively, you may view the same data within the CUCM Administration web interface by use of the Find Phones by LSC Status or Authentication String procedure.

In order to obtain copies of the LSC certificates installed in phones, refer the How to retrieve certificates from Cisco IP phonesarticle.

Troubleshoot

This section provides information you can use in order to troubleshoot your configuration.

No valid CAPF server

The LSC fails to install. The phone’s Status Messages show No valid CAPF server. This indicates that there is no CAPF entry in the ITL file. Verify that the CAPF service was activated, and then restart the TFTP Service. Verify that the ITL file contains a CAPF certificate after the restart, reset the phone to pick up the latest ITL file, and then retry your certificate operation. If the CAPF server entry in the phone's security settings menu displays as hostname or fully qualified domain name, confirm the phone is able to resolve the entry to an IP address.

LSC: Connection Failed

The LSC fails to install. The phone’s Status Messages show LSC: Connection Failed. This may indicate one of these conditions:

A mismatch between the CAPF certificate in ITL file and the current certificate, the CAPF service is in use.
The CAPF service is stopped or deactivated.
The phone cannot reach the CAPF service over the network.

Verify the CAPF service is activated, restart the CAPF service, restart TFTP services clusterwide, reset the phone to pick up the latest ITL file, and then retry your certificate operation. If the problem persists, take a packet capture from the phone and the CUCM Publisher, and analyze in order to see if there is bidirectional communication on port 3804, the default CAPF service port. If not, there may be a network issue.

LSC: Failed

The LSC fails to install. The phone’s Status Messages show LSC: Failed. The Phone Configuration web page shows Certificate Operation Status: Upgrade Failed: User Initiated Request Late/Timedout. This indicates that the Operation Completes By time and date have expired or are in the past. Enter a date and time that is at least one hour in to the future, and then retry your certificate operation.

Related Information

These documents provide more information on the use of LSCs in the context for AnyConnect VPN client authentication and 802.1X authentication.

There is also an advanced type of LSC configuration, in which the LSC certificates are signed directly by a third party Certificate Authority, not the CAPF certificate.

For details, refer: CUCM Third-Party CA-Signed LSCs Generation and Import Configuration Example