TLSv1.3 protocol support as defined in RFC 8446

The Citrix ADC VPX and Citrix ADC MPX appliances now support the TLSv1.3 protocol, specified in RFC 8446.

Notes:

• 从13.0版本构建71。x和后,TLS1.3 hardware acceleration is supported on the following platforms:

  • MPX 5900
  • MPX/SDX 8900
  • MPX/SDX 15000
  • MPX/SDX 15000-50G
  • MPX/SDX 26000
  • MPX/SDX 26000-50S

  • MPX/SDX 26000-100G

  • Software-only support for the TLSv1.3 protocol is available on all other Citrix ADC MPX and SDX appliances except Citrix ADC FIPS appliances.

• TLSv1.3 is only supported with the enhanced profile. To enable the enhanced profile, seeEnable the enhanced profile.

• To use TLS1.3, you must use a client that conforms to the RFC 8446 specification.

Supported Citrix ADC features

The following SSL features are supported:

1. TLSv1.3 cipher suites:
   • TLS1.3-AES256-GCM-SHA384 (0x1302)
   • TLS1.3_CHACHA20_POLY1305_SHA256 (0x1303)
   • TLS1.3-AES128_GCM-SHA256 (0x1301)
2. ECC curves for ephemeral Diffie-Hellman key exchange:
   • P_256
   • P_384
   • P_521

3. Abbreviated handshakes when ticket-based session resumption is enabled

4. 0-RTT early application data

5. Optional or mandatory certificate-based client authentication, with support for OCSP and CRL validation of client certificates

6. Server name extension: server certificate selection by using SNI

7. Application protocol negotiation (ALPN) by using the application_level_protocol_negotiation extension.

8. OCSP stapling

9. Log messages and AppFlow records are produced for TLSv1.3 handshakes.

10. Optional logging of TLS 1.3 traffic secrets by thenstracepacket capture utility.

11. Interoperability with TLS clients implementing RFC 8446. For example, Mozilla Firefox, Google Chrome, and OpenSSL.

Supported browsers

The following browser versions are supported and compatible with the Citrix ADC implementation oF TLS 1.3 protocol:

• Google Chrome - Version 72.0.3626.121 (Official Build) (64-bit)
• Mozilla Firefox - 65.0.2 (64-bit)
• Opera - Version:58.0.3135.79

配置

TLSv1.3 is disabled by default on an SSL profile.

Add an SSL profile by using the CLI

At the command prompt, type:

add ssl profile  

Example:

添加ssl配置tls13profile sh tls13p ssl配置文件rofile 1) Name: tls13profile (Front-End) SSLv3: DISABLED TLSv1.0: ENABLED TLSv1.1: ENABLED TLSv1.2: ENABLED TLSv1.3: DISABLED Client Auth: DISABLED Use only bound CA certificates: DISABLED Strict CA checks: NO Session Reuse: ENABLED Timeout: 120 seconds DH: DISABLED DH Private-Key Exponent Size Limit: DISABLED Ephemeral RSA: ENABLED Refresh Count: 0 Deny SSL Renegotiation ALL Non FIPS Ciphers: DISABLED Cipher Redirect: DISABLED SSL Redirect: DISABLED Send Close-Notify: YES Strict Sig-Digest Check: DISABLED Zero RTT Early Data: DISABLED DHE Key Exchange With PSK: NO Tickets Per Authentication Context: 1 Push Encryption Trigger: Always PUSH encryption trigger timeout: 1 ms SNI: DISABLED OCSP Stapling: DISABLED Strict Host Header check for SNI enabled SSL sessions: NO Push flag: 0x0 (Auto) SSL quantum size: 8 kB Encryption trigger timeout 100 mS Encryption trigger packet count: 45 Subject/Issuer Name Insertion Format: Unicode SSL Interception: DISABLED SSL Interception OCSP Check: ENABLED SSL Interception End to End Renegotiation: ENABLED SSL Interception Maximum Reuse Sessions per Server: 10 Session Ticket: DISABLED HSTS: DISABLED HSTS IncludeSubDomains: NO HSTS Max-Age: 0 ECC Curve: P_256, P_384, P_224, P_521 1) Cipher Name: DEFAULT Priority :1 Description: Predefined Cipher Alias Done 

Add an SSL profile by using the GUI

1. Navigate toSystem > Profiles. SelectSSL Profiles.
2. ClickAddand specify a name for the profile.

3. InProtocol, selectTLSv13.

   

4. ClickOK.

Bind an SSL profile to an SSL virtual server by using the CLI

At the command prompt, type:

set ssl vserver  -sslProfile  

Example:

set ssl vserver ssl-vs -sslProfile tls13profile

Bind an SSL profile to an SSL virtual server by using the GUI

1. Navigate toTraffic Management > Load Balancing > Virtual Servers, and select an SSL virtual server.
2. InAdvanced Settings, clickSSL Profile.
3. Select the TLSv1.3 profile created earlier.
4. ClickOK.
5. ClickDone.

SSL profile parameters for TLSv1.3 protocol

1. Enable or disable TLS1.3 parameters in an SSL profile.

   tls13: State of TLSv1.3 protocol support for the SSL profile.

   Possible values: ENABLED, DISABLED

   Default value: DISABLED

   set ssl profile tls13profile -tls13 enable 

   set ssl profile tls13profile -tls13 disable 

2. Set number of session tickets issued.

   tls13SessionTicketsPerAuthContext: Number of tickets the SSL virtual server issues when TLS1.3 is negotiated, ticket-based resumption is enabled, and either (1) a handshake completes or (2) client authentication completes after the handshake.

   This value can be increased to enable clients to open multiple parallel connections using a fresh ticket for each connection.

   No tickets are sent if resumption is disabled.

   Default value: 1

   Minimum value: 1

   Maximum value: 10

   set ssl profile tls13profile -tls13sessionTicketsPerAuthContext 1 set ssl profile tls13profile -tls13sessionTicketsPerAuthContext 10 

3. Set DH key exchange

   dheKeyExchangeWithPsk: Specifies whether an SSL virtual server requires a DHE key exchange to occur when a preshared key is accepted during a TLS 1.3 session resumption handshake. A DHE key exchange ensures forward secrecy, even if ticket keys are compromised, at the expense of extra resources required to carry out theDHEkey exchange.

   Available settings work as follows, if session ticket is enabled:

   YES: DHE key exchange is required when a pre-shared key is accepted, regardless of whether the client supports the key exchange. The handshake is aborted with a fatal alert, if the client does not support DHE key exchange when offering a pre-shared key.

   NO: DHE key exchange is performed when a pre-shared key is accepted, only if requested by the client.

   Possible values: YES, NO

   Default value: NO

   set ssl profile tls13profile dheKeyExchangeWithPsk yes set ssl profile tls13profile dheKeyExchangeWithPsk no 

4. Enable or disable 0-RTT early data acceptance

   zeroRttEarlyData: State of TLS 1.3 early application data. Applicable settings work as follows:

   ENABLED: Early application data might be processed before the handshake is complete. DISABLED: Early application data is ignored.

   Possible values: ENABLED, DISABLED

   Default value: DISABLED

   set ssl profile tls13profile -zeroRttEarlyData ENABLED set ssl profile tls13profile -zeroRttEarlyData DISABLED 

Default cipher group

The default cipher group includes TLS1.3 ciphers.

sh cipher DEFAULT 1) Cipher Name: TLS1-AES-256-CBC-SHA Priority : 1 Description: SSLv3 Kx=RSA Au=RSA Enc=AES(256) Mac=SHA1 HexCode=0x0035 2) Cipher Name: TLS1-AES-128-CBC-SHA Priority : 2 Description: SSLv3 Kx=RSA Au=RSA Enc=AES(128) Mac=SHA1 HexCode=0x002f … … 27) Cipher Name: TLS1.3-AES256-GCM-SHA384 Priority : 27 Description: TLSv1.3 Kx=any Au=any Enc=AES-GCM(256) Mac=AEAD HexCode=0x1302 28) Cipher Name: TLS1.3_CHACHA20_POLY1305_SHA256 Priority : 28 Description: TLSv1.3 Kx=any Au=any Enc=CHACHA20/POLY1305(256) Mac=AEAD HexCode=0x1303 29) Cipher Name: TLS1.3-AES128_GCM-SHA256 Priority : 29 Description: TLSv1.3 Kx=any Au=any Enc=AES-GCM(128) Mac=AEAD HexCode=0x1301 Done 

Limitations

• On the Citrix ADC MPX platform, TLSv1.3 processing is not offloaded to crypto hardware.
• TLSv1.3 is not supported on the back end.
• TLSv1.3 is not supported on a Citrix Secure Web Gateway appliance and on a Citrix ADC FIPS appliance.

Operational considerations

TLS 1.3 draft version compatibility note: A Citrix ADC appliance implements the RFC 8446 variant of the TLS 1.3 protocol (as opposed to earlier draft versions of the protocol). Use a TLS 1.3 client that supports RFC 8446 (or an interoperable draft # - 26, 27 or 28) to complete a TLS 1.3 handshake with a Citrix ADC appliance. Clients and servers that implement different draft versions of the TLS 1.3 protocol might not interoperate with each other.

Security restrictions

TLSv1.3 server operators must keep in mind the following security restrictions for backward compatibility outlined in RFC 8446. The default configuration on a NetScaler appliance is compliant with these restrictions. However, a NetScaler appliance does not enforce that these rules are adhered to.

• The security of RC4 cipher suites is considered insufficient as described in RFC7465. Implementations must not offer or negotiate RC4 cipher suites for any version of TLS.

• Old versions of TLS allowed the use of low strength ciphers. Ciphers with a strength less than 112 bits must not be offered or negotiated for any version of TLS.

• The security of SSL 3.0 [SSLv3] is considered insufficient as described in RFC7568, and must not be negotiated. Disable SSLv3 when TLSv1.3 is enabled (SSLv3 is disabled by default.)

• The security of SSL 2.0 [SSLv2] is considered insufficient as described in RFC6176, and must not be negotiated. Disable SSLv2 when TLS 1.3 is enabled (SSLv2 is disabled by default.)

Note:

For information about troubleshooting protocols that run over TLS1.3, seeDecrypting TLS1.3 traffic from packet trace.