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Cisco Unified Communications Manager Security Guide, Release 7.0(1)
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Index
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Preface
- Security Basics
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Security for Cisco Unified IP Phones and Cisco Unity Voice-Messaging Ports
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Phone Security Overview
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Configuring a Phone Security Profile
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Configuring Secure-Indication Tone
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Using the Certificate Authority Proxy Function
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Configuring Encrypted Phone Configuration Files
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Configuring Digest Authentication for the SIP Phone
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Phone Hardening
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Configuring Secure Conference Resources
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Configuring Voice-Messaging Ports for Security
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- Security for Cisco CTI, JTAPI, and TAPI Applications
- Security for SRST References, Trunks, Gateways, and CUMA Servers
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Feedback
Table Of Contents
Configuring Encrypted Phone Configuration Files
Understanding Encryption of the Phone Configuration File
Symmetric Key Encryption with Phone Public Key
Configuration Tips for Encrypted Configuration Files
Encryption Configuration File Configuration Checklist
Enabling Phone Configuration File Encryption
Configuring Manual Key Distribution
Manual Key Distribution Configuration Settings
Entering the Symmetric Key on the Phone
Verifying That an LSC or MIC Certificate Is Installed
Verifying That the Phone Configuration File Is Encrypted
Disabling Encryption for the Phone Configuration Files
Excluding Digest Credentials from Phone Configuration File Download
Where to Find More Information
Configuring Encrypted Phone Configuration Files
After you configure security-related settings, the phone configuration file contains sensitive information, such as digest passwords and phone administrator passwords. To ensure privacy of the configuration file, you must configure the configuration files for encryption.
This chapter contains information on the following topics:
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Understanding Encryption of the Phone Configuration File
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Understanding Encryption of the Phone Configuration File
To secure digest credentials and secured passwords in phone downloads from Cisco Unified Communications Manager, you must enable the TFTP Encrypted Config option in the Phone Security Profile Configuration window and perform additional tasks in Cisco Unified Communications Manager Administration.
After you enable the TFTP Encrypt Config option, configure the required parameters in Cisco Unified Communications Manager Administration and the phone and restart required services in Cisco Unified Serviceability, the TFTP server
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If the phone supports encrypted phone configuration files and if you performed the necessary tasks for phone configuration file encryption, the phone requests an encrypted version of the configuration file.
Warning
Some phones do not support encrypted phone configuration files, as described in "Supported Phone Models" section. The phone model and protocol determine the method that the system uses to encrypt the configuration file. Supported methods rely on Cisco Unified Communications Manager functionality and a firmware load that supports encrypted configuration files. If you downgrade the phone firmware load to a version that does not support encrypted configuration files, the TFTP server offers an unencrypted configuration file that provides minimal configuration settings, and the phone may not perform as expected.
To ensure that you maintain the privacy of the key information, Cisco strongly recommends that you perform the tasks that are associated with encrypted phone configuration files in a secure environment.
Cisco Unified Communications Manager supports the following methods:
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The information in the "Manual Key Distribution" and "Symmetric Key Encryption with Phone Public Key" sections assumes that you configured Mixed Mode and that you enabled the TFTP Encrypted Config parameter in Cisco Unified Communications Manager Administration.
Manual Key Distribution
Tip
With manual key distribution, a 128- or 256-bit symmetric key, which is stored in the Cisco Unified Communications Manager database, encrypts the phone configuration file after the phone resets. To determine the key size for your phone model, see "Supported Phone Models" section.
To encrypt the configuration file, the administrator can either manually enter the key into or prompt Cisco Unified Communications Manager to generate the key in the Phone Configuration window. After the key exists in the database, the administrator or user must enter the key into the phone by accessing the user interface on the phone; the phone stores the key in flash as soon as you press the Accept softkey. After the key is entered, the phone requests an encrypted configuration file after it is reset. After the required tasks occur, the symmetric key uses RC4 or AES 128 encryption algorithms to encrypt the configuration file. To determine which phones use the RC4 or AES 128 encryption algorithms, see "Supported Phone Models" section.
When the phone contains the symmetric key, the phone always requests the encrypted configuration file. Cisco Unified Communications Manager downloads the encrypted configuration file to the phone, which the TFTP server signs. Not all phone types validate the signer of the configuration file; see "Supported Phone Models" section for more information.
The phone decrypts the file contents by using the symmetric key that is stored in flash. If decryption fails, the configuration file does not get applied to the phone.
Tip
Symmetric Key Encryption with Phone Public Key
Tip
For more information about The Certificate Authority Proxy Function (CAPF), see "Certificate Authority Proxy Function Overview" section on page 7-1. The Certificate Authority Proxy Function (CAPF) authenticates Cisco Unified IP Phones to Cisco Unified Communications Manager and issues phone certificates (LSCs).If the phone contains a manufacturing-installed certificate (MIC) or a locally significant certificate (LSC), the phone contains a public and private key pair, which are used for PKI encryption.
If you are using this method for the first time, the phone compares the MD5 hash of the phone certificate in the configuration file to the MD5 hash of the LSC or MIC. If the phone does not identify a problem, the phone requests an encrypted configuration file from the TFTP server after the phone resets. If the phone identifies a problem, for example, the hash does not match, the phone does not contain a certificate, or the MD5 value is blank, the phone attempts to initiate a session with CAPF unless the CAPF authentication mode equals By Authentication String (in which case, you must manually enter the string). CAPF extracts the phone public key from the LSC or MIC, generates a MD5 hash, and stores the values for the public key and certificate hash in the Cisco Unified Communications Manager database. After the public key gets stored in the database, the phone resets and requests a new configuration file.
After the public key exists in the database and the phone resets, the symmetric key encryption process begins after the database notifies TFTP that the public key exists for the phone. The TFTP server generates a 128-bit symmetric key, which encrypts the configuration file with the Advanced Encryption Standard (AES) 128 encryption algorithm. Then, the phone public key encrypts the symmetric key, which it includes in the signed envelope header of the configuration file. The phone validates the file signing, and, if the signature is valid, the phone uses the private key from the LSC or MIC to decrypt the encrypted symmetric key. The symmetric key then decrypts the file contents.
Every time that you update the configuration file, the TFTP server automatically generates a new key to encrypt the file.
Tip
If the TFTP Encrypted Config setting is enabled but the phone requests an unencrypted configuration file for some reason, the TFTP server offers an unencrypted file that contains minimal configuration settings. After the phone receives the minimum configuration, the phone can detect error conditions, such as key mismatch, and may start a session with CAPF to synchronize the phone public key with the Cisco Unified Communications Manager database. If the error condition is resolved, the phone requests an encrypted configuration file the next time that it resets.
Supported Phone Models
You can encrypt the phone configuration file for the following Cisco Unified IP Phones:
Configuration Tips for Encrypted Configuration Files
Cisco recommends that you enable the TFTP Encrypted Config flag to secure confidential data in phone downloads. For phones that do not have PKI capabilities, you must also configure a symmetric key in Cisco Unified Communications Manager Administration and in the phone. If the symmetric key is missing from either the phone or Cisco Unified Communications Manager or if a mismatch occurs when the TFTP Encrypted Config flag is set, the phone cannot register.
Consider the following information when you configure encrypted configuration files in Cisco Unified Communications Manager Administration:
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With this method, you send the digest credentials to the phone in an unencrypted configuration file. After the credentials are in the phone, Cisco recommends that you keep the TFTP file encryption setting disabled and enable the TFTP Exclude Digest Credential in Configuration File flag on the corresponding security profile window, which will exclude digest credentials from future downloads.
After digest credentials exist in these phones and an incoming file does not contain digest credentials, the existing credentials remain in place. The digest credentials remain intact until the phone is factory reset or new credentials (including blanks) are received.
If you change digest credentials for a phone or end user, temporarily disable the Exclude Digest Credentials flag on the corresponding security profile window to download the new digest credentials to the phone.Encryption Configuration File Configuration Checklist
Use Table 8-1 to guide you through the configuration process for encrypted configuration files in Cisco Unified Communications Manager Administration.
Table 8-1 Encryption Configuration File Configuration Checklist
Step 1
Verify that the Cluster Security Mode is configured for Mixed Mode.
Note
Step 2
Check the TFTP Encrypted Config check box in the Phone Security Profile. Be sure to apply the profile to the phone.
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Step 3
Determine which phones support manual key distribution and which phones support symmetric key encryption with phone public key (PKI encryption).
Step 4
If your phone supports manual key distribution, perform the manual key distribution tasks.
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If your phone supports manual key distribution, enter the symmetric key on the phone; reset the phone.
Step 6
If your phone supports the method, symmetric key encryption with phone public key (PKI encryption), verify that a manufacture-installed certificate (MIC) or locally significant certificate (LSC) exists in the phone.
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Enabling Phone Configuration File Encryption
The TFTP server queries the database when it builds the configuration file. If the phone security profile that is applied to the phone has the TFTP encrypted configuration flag set, the TFTP server builds an encrypted configuration file.
To access the TFTP encryption flag, find the appropriate device security profile for the phone, as described in "Finding a Phone Security Profile" section on page 5-2. Check the TFTP Encrypted Config check box to enable configuration file encryption.
Additional Information
See the "Related Topics" section
Configuring Manual Key Distribution
To determine whether your phone supports manual key distribution, see "Supported Phone Models" section.
The following procedure assumes that
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Procedure
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Additional Information
See the "Related Topics" section.
Manual Key Distribution Configuration Settings
Table 8-2 describes the manual distribution configuration settings in the Phone Configuration window.
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Entering the Symmetric Key on the Phone
Follow this procedure to enter the symmetric key on the phone after you configure manual key distribution in Cisco Unified Communications Manager Administration.
Procedure
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The phone accepts the password.
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The phone accepts the encryption key.
Step 7
After the phone resets, the phone requests encrypted configuration files.
Verifying That an LSC or MIC Certificate Is Installed
This procedure applies to Cisco Unified IP Phones that use PKI encryption. To determine whether your phone supports the method, symmetric key encryption with phone public key (PKI encryption), see the "Supported Phone Models" section.
The following procedure assumes that the phone exists in the Cisco Unified Communications Manager database and that you enabled the TFTP Encrypted Config parameter in Cisco Unified Communications Manager Administration.
Procedure
Step 1
Tip
You can also verify that an LSC or MIC exists in the phone by checking the security configuration at the phone. Refer to the Cisco Unified IP Phone administration guides for Cisco Unified IP Phones that support this version of Cisco Unified Communications Manager for more information.Step 2
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Additional Information
See the "Related Topics" section.
Verifying That the Phone Configuration File Is Encrypted
When the phone configuration file is encrypted, it uses the following format:
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To access the configuration file at the phone, refer to the Cisco Unified IP Phone administration guides for Cisco Unified IP Phones that support encryption and this Cisco Unified Communications Manager release for more information.
Disabling Encryption for the Phone Configuration Files
To disable encryption for the phone configuration files, you must uncheck the TFTP Encrypted Config check box in the phone security profile in Cisco Unified Communications Manager Administration and save your change.
Warning
After you update the setting, the encryption keys for the phone remain in the Cisco Unified Communications Manager database.
Cisco Unified IP Phones 7911G, 7931G (SCCP only), 7941G, 7941G-GE, 7942G, 7945G, 7961G, 7961G-GE, 7962G, 7965G, 7970G, 7971G, 7971G-GE, and 7975G request an encrypted file (.enc.sgn file) when the encrypted configuration setting gets updated to false, the phone requests an unencrypted, signed file (.sgn file).
If Cisco Unified IP Phones 7940G/7960G/7905G/7912G (SIP only) request an encrypted file when the encryption configuration setting gets updated to False, administrators must remove the symmetric key from the phone GUI so the phone requests an unencrypted configuration file the next time that it is reset.
Tip
Excluding Digest Credentials from Phone Configuration File Download
To exclude digest credentials from the configuration file that is sent to phones after the initial configuration, check the TFTP Exclude Digest Credentials in Configuration File check box for the security profile that is applied to the phone. Only Cisco Unified IP Phones 7905G, 7912G, 7940G, and 7960G (SIP only) support this option.
You may need to uncheck this check box to update the configuration file for changes to digest credentials. See the "Configuration Tips for Encrypted Configuration Files" section for more information.
Additional Information
See the "Related Topics" section.
Where to Find More Information
Related Topics
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Related Cisco documentation
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