Citrix ADC

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SSL offloading configuration

June 15, 2021

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To configure SSL offloading, you must enable SSL processing on the Citrix ADC appliance. Configure an SSL based virtual server that will intercept SSL traffic, decrypt the traffic, and forward it to a service that is bound to the virtual server. To secure time-sensitive traffic, such as media streaming, you can configure a DTLS virtual server. To enable SSL offloading, you must import a valid certificate and key and bind the pair to the virtual server.

Enable SSL

To process SSL traffic, you must enable SSL processing. You can configure SSL based entities, such as virtual servers and services, without enabling SSL processing, but they do not work until SSL processing is enabled.

Enable SSL processing by using the CLI

At the command prompt, type:

enable ns feature ssl show ns feature

Example:

             enable ns feature SSL Done show ns feature Feature Acronym Status ------- ------- ------ 1) Web Logging WL OFF 2) Surge Protection SP ON 3) Load Balancing LB ON . . . 9) SSL Offloading SSL ON . . . 24) NetScaler Push push OFF Done 
            

Enable SSL processing by using the GUI

Navigate toSystem > Settingsand, in the Modes and Features group, selectConfigure Basic Features, and selectSSL Offloading.

Configure services

On the Citrix ADC appliance, a service represents a physical server or an application on a physical server. Once configured, services are in the disabled state until the appliance can reach the physical server on the network and monitor its status.

Add a service by using the CLI

在命令提示符下,键入以下命令to add a service and verify the configuration:

add service  ( | )   show service

Example:

             add service sslsvc 198.51.100.225 SSL 443 Done sh ssl service sslsvc Advanced SSL configuration for Back-end SSL Service sslsvc: DH: DISABLED DH Private-Key Exponent Size Limit: DISABLED Ephemeral RSA: DISABLED Session Reuse: ENABLED Timeout: 300 seconds Cipher Redirect: DISABLED SSLv2 Redirect: DISABLED ClearText Port: 0 Server Auth: DISABLED SSL Redirect: DISABLED Non FIPS Ciphers: DISABLED SNI: DISABLED OCSP Stapling: DISABLED SSLv2: DISABLED SSLv3: ENABLED TLSv1.0: ENABLED TLSv1.1: ENABLED TLSv1.2: ENABLED TLSv1.3: DISABLED Send Close-Notify: YES Strict Sig-Digest Check: DISABLED Zero RTT Early Data: ??? DHE Key Exchange With PSK: ??? Tickets Per Authentication Context: ??? ECC Curve: P_256, P_384, P_224, P_521 1) Cipher Name: DEFAULT_BACKEND Description: Default cipher list for Backend SSL session Done 
            

Modify or remove a service by using the CLI

To modify a service, use the set service command, which is just like using the add service command, except that you enter the name of an existing service. To remove a service, use the rm service command, which accepts only the argument.

Configure a service by using the GUI

Navigate toTraffic Management > Load Balancing > Services, create a service, and specify the protocol as SSL.

SSL virtual server configuration

Secure sessions require establishing a connection between the client and an SSL-based virtual server on the Citrix ADC appliance. The SSL virtual server intercepts SSL traffic, decrypts it and processes it before sending it to services that are bound to the virtual server.

Note:的SSL virtual server is marked as down on the Citrix ADC appliance until a valid certificate / key pair and at least one service are bound to it. An SSL based virtual server is a load balancing virtual server of protocol type SSL or SSL_TCP. The load balancing feature must be enabled on the Citrix ADC appliance.

Add an SSL-based virtual server by using the CLI

在命令提示符下,键入以下命令to create an SSL-based virtual server and verify the configuration:

add lb vserver  (serviceType)   show ssl vserver

Example:

             add lb vserver sslvs SSL 192.0.2.240 443 Done sh ssl vserver sslvs Advanced SSL configuration for VServer sslvs: DH: DISABLED DH Private-Key Exponent Size Limit: DISABLED Ephemeral RSA: ENABLED Refresh Count: 0 Session Reuse: ENABLED Timeout: 120 seconds Cipher Redirect: DISABLED SSLv2 Redirect: DISABLED ClearText Port: 0 Client Auth: DISABLED SSL Redirect: DISABLED Non FIPS Ciphers: DISABLED SNI: DISABLED OCSP Stapling: DISABLED HSTS: DISABLED HSTS IncludeSubDomains: NO HSTS Max-Age: 0 SSLv2: DISABLED SSLv3: ENABLED TLSv1.0: ENABLED TLSv1.1: ENABLED TLSv1.2: ENABLED TLSv1.3: DISABLED Push Encryption Trigger: Always 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 ECC Curve: P_256, P_384, P_224, P_521 1) Cipher Name: DEFAULT Description: Default cipher list with encryption strength >= 128bit Done 
            

Modify or remove an SSL-based virtual server by using the CLI

修改SSL的负载平衡特性virtual server, use theset lb vservercommand, which is just like using theadd lb vservercommand, except that you enter the name of an existing virtual server. To modify the SSL properties of an SSL-based virtual server, use theset ssl vserver命令。有关更多信息,请参见“SSL与启示l server parameters” section later in this page.

To remove an SSL virtual server, use therm lb vservercommand, which accepts only theargument.

Configure an SSL-based virtual server by using the GUI

Navigate toTraffic Management > Load Balancing > Virtual Servers, create a virtual server, and specify the protocol as SSL.

Bind services to the SSL virtual server

的ADC appliance forwards decrypted SSL data to servers in the network, when services representing these physical servers are bound to the virtual server that receives the SSL data.

Because the link between the Citrix ADC appliance and the physical server is typically secure, data transfer between the appliance and the physical server can be unencrypted. However, you can provide end-to end-encryption by encrypting data transfer between the appliance and the server. For details, seeConfigure SSL offloading with end-to-end encryption.

Note:Enable the load balancing feature on the Citrix ADC appliance before you bind services to the SSL based virtual server.

Bind a service to a virtual server by using the CLI

在命令提示符下,键入以下命令to bind the service to the virtual server and verify the configuration:

bind lb vserver   show lb vserver

Example:

             绑定磅vserver sslvs sslsvc sh磅vserver党卫军lvs sslvs (192.0.2.240:443) - SSL Type: ADDRESS State: DOWN[Certkey not bound] Last state change was at Wed May 2 11:43:04 2018 Time since last state change: 0 days, 00:13:21.150 Effective State: DOWN Client Idle Timeout: 180 sec Down state flush: ENABLED Disable Primary Vserver On Down : DISABLED Appflow logging: ENABLED No. of Bound Services : 1 (Total) 0 (Active) Configured Method: LEASTCONNECTION BackupMethod: ROUNDROBIN Mode: IP Persistence: NONE Vserver IP and Port insertion: OFF Push: DISABLED Push VServer: Push Multi Clients: NO Push Label Rule: none L2Conn: OFF Skip Persistency: None Listen Policy: NONE IcmpResponse: PASSIVE RHIstate: PASSIVE New Service Startup Request Rate: 0 PER_SECOND, Increment Interval: 0 Mac mode Retain Vlan: DISABLED DBS_LB: DISABLED Process Local: DISABLE Traffic Domain: 0 TROFS Persistence honored: ENABLED Retain Connections on Cluster: NO 1) sslsvc (198.51.100.225: 443) - SSL State: DOWN Weight: 1 Done 
            

Unbind a service from a virtual server by using the CLI

At the command prompt, type the following command:

unbind lb vserver

Example:

unbind lb vserver sslvs sslsvc Done

Bind a service to a virtual server by using the GUI

Navigate toTraffic Management > Load Balancing > Virtual Servers.
Open a virtual server, and click in the Services section to bind a service to the virtual server.

Configure an SNI virtual server for secure hosting of multiple sites

Virtual hosting is used by web servers to host more than one domain name with the same IP address. The appliance supports hosting of multiple secure domains by offloading SSL processing from the Web servers using transparent SSL services or virtual server-based SSL offloading. However, when multiple websites are hosted on the same virtual server, the SSL handshake is completed before the expected host name is sent to the virtual server. As a result, the appliance cannot determine which certificate to present to the client after a connection is established. This problem is resolved by enabling Server Name Indication (SNI) on the virtual server. SNI is a Transport Layer Security (TLS) extension used by the client to provide the host name during handshake initiation. The Citrix ADC appliance compares this host name to the common name and, if it does not match, compares it to the subject alternative name (SAN). If the name matches, the appliance presents the corresponding certificate to the client.

A wildcard SSL Certificate helps enable SSL encryption on multiple subdomains if the domains are controlled by the same organization and share the second-level domain name. For example, a wildcard certificate issued to a sports network using the common name “*.sports.net” can be used to secure domains, such as “login.sports.net” and “help.sports.net” but not “login.ftp.sports.net.”

Notes:

On a Citrix ADC appliance, only domain name, URL, and email ID DNS entries in the SAN field are compared.
If an existing certificate-key pair (for example,certkey A) is bound to an SSL virtual server, and a second certificate-key pair (for example,certkey B) is added using SNI and bound to the same virtual server,certkey Amust also be configured as-SNICert. If a Client Hello message includes an SNI extension with the domain name ofcertkey Aand the preceding configuration is not in place, TLS connections to the domains in (certkey A) do not work.

You can bind multiple server certificates to a single SSL virtual server or transparent service using the -SNICert option. These certificates are issued by the virtual server or service if SNI is enabled on the virtual server or service. You can enable SNI at any time.

Bind multiple server certificates to a single SSL virtual server by using the CLI

在命令提示符下,键入以下命令to configure SNI and verify the configuration:

             set ssl vserver @ [-SNIEnable ( ENABLED | DISABLED )] bind ssl vserver @ -certkeyName  -SNICert show ssl vserver  
            

To bind multiple server certificates to a transparent service by using the CLI, replacevserverwithserviceandvservernamewithservicenamein the preceding commands.

Note:Create the SSL service with the-clearTextPort 80option.

Bind multiple server certificates to a single SSL virtual server by using the GUI

Navigate toTraffic Management > Load Balancing > Virtual Servers.
Open an SSL virtual server and, in Certificates, click Server Certificate.
Add a certificate or select a certificate from the list, and select Server Certificate for SNI.
In Advanced Settings, click SSL Parameters.
Select SNI Enable.

Support for SNI on the back-end service

Note: SNI is not supported on a DTLS back-end service.

的Citrix ADC appliance supports Server Name Indication (SNI) at the back end. That is, the common name is sent as the server name in the client hello to the back-end server for successful completion of the handshake. In addition to helping meet federal system integrator customer security requirements, this enhancement provides the advantage of using only one port instead of opening hundreds of different IP addresses and ports on a firewall.

Federal system integrator customer security requirements include support for Active Directory Federation Services (ADFS) 3.0 in 2012R2 and WAP servers. This requires supporting SNI at the back end on a Citrix ADC appliance.

Note:

For SNI to work, the server name in the client hello must match the host name configured on the back-end service that is bound to an SSL virtual server. For example, if the host name of the back end server is www.mail.example.com, the SNI-enabled back-end service must be configured with the server name ashttps://www.mail.example.com, and this host name must match the server name in the client hello.

Configure SNI on the back-end service by using the CLI

At the command prompt, type:

             添加服务<名称> < IP > < serviceType > add lb vserver     bind lb vserver   set ssl service  -SNIEnable ENABLED -commonName  
            

Example:

             add service service_ssl 198.51.100.100 SSL 443 add lb vserver ssl-vs 203.0.113.200 SSL 443 bind lb vserver ssl-vs service_ssl set ssl service service_ssl -SNIEnable ENABLED –commonName www.example.com 
            

Configure SNI on the back-end service by using the GUI

Navigate toTraffic Management>Load Balancing>Services.
Select an SSL service, and inAdvanced Settings, selectSSL Parameters.
SelectSNI Enable.

Bind a secure monitor to an SNI-enabled back-end service

You can also bind secure monitors of type HTTP-ECV or TCP-ECV to the back-end services that support SNI. To do so, the custom header in the monitor must be set to the server name that is sent as the SNI extension in the client hello.

Configure and bind a secure monitor to an SNI-enabled back-end service by using the CLI

At the command prompt, type:

add lb monitor   set lb monitor   -customHeaders  bind service  -monitorName

Example:

             add monitor https-ecv-mon http-ecv Done set monitor https-ecv-mon HTTP-ECV -customHeaders "Host: example.com\r\n" Done bind service ssl_service –monitorName https-ecv 
            

Configure and bind a secure monitor to an SNI-enabled back-end service by using the GUI

Navigate toTraffic Management>Load Balancing>Monitor.
Add a monitor of typeHTTP-ECVorTCP-ECV, and specify aCustom Header.
ClickCreate.
Navigate toTraffic Management>Load Balancing>Services.
Select an SSL service and clickEdit.
InMonitors, clickAdd Binding, select the monitor created in step 3, and clickBind.

Add or update a certificate-key pair

Caution:If while adding a certificate-key pair, you add a certificate file with the same name as an existing certificate file but with different content, the original certificate file is overwritten with no warning. This action might cause issues after the appliance is restarted because the original certificate file is no longer available in the /nsconfig/ssl directory.

Note:

If you don’t have an existing certificate and key, seeCreate a certificate.

To create an ECDSA certificate-key pair, clickCreate an ECDSA certificate-key pair.

From release 12.1 build 50.x, the password of the private key used while adding an SSL certificate-key pair is now saved using a unique encryption key for each Citrix ADC appliance.

For any SSL transaction, the server needs a valid certificate and the corresponding private and public key pair. The SSL data is encrypted with the server’s public key, which is available through the server’s certificate. Decryption requires the corresponding private key.

Because the Citrix ADC appliance offloads SSL transactions from the server, the server’s certificate and private key must be present on the appliance, and the certificate must be paired with its corresponding private key. This certificate-key pair must then be bound to the virtual server that processes the SSL transactions.

Note:从11.0版本,默认证书Citrix ADC appliance is 2048 bits. In earlier builds, the default certificate was 512 bits or 1024 bits. After upgrading to release 11.0, you must delete all your old certificate-key pairs starting with “ns-“, and then restart the appliance to automatically generate a 2048-bit default certificate.

Both the certificate and the key must be in local storage on the Citrix ADC appliance before they can be added to the appliance. If your certificate or key file is not on the appliance, upload it to the appliance before you create the pair.

Important:Certificates and keys are stored in the /nsconfig/ssl directory by default. If your certificates or keys are stored in any other location, you must provide the absolute path to the files on the Citrix ADC appliance. The Citrix ADC FIPS appliances do not support external keys (non-FIPS keys). On a FIPS appliance, you cannot load keys from a local storage device such as a hard disk or flash memory. The FIPS keys must be present in the Hardware Security Module (HSM) of the appliance.

On a Citrix ADC MPX appliance and a Citrix ADC FIPS appliance, only RSA private keys are supported. On a VPX virtual appliance, both RSA and DSA private keys are supported. On an SDX appliance if SSL chips are assigned to an instance, then only RSA private keys are supported. However, if SSL chips are not assigned to an instance, then both RSA and DSA private keys are supported. In all the cases, you can bind a CA certificate with either RSA or DSA keys.

Set the notification period and enable the expiry monitor to issue a prompt before the certificate expires.

的Citrix ADC appliance supports the following input formats of the certificate and the private-key files:

PEM - Privacy Enhanced Mail
DER - Distinguished Encoding Rule
PFX - Personal Information Exchange

的software automatically detects the format. Therefore, you are no longer required to specify the format in the inform parameter. If you do specify the format (correct or incorrect), the software ignores it. The format of the certificate and the key file must be the same.

Note:A certificate must be signed by using one of the following hash algorithms:

MD5
SHA-1
SHA-224
SHA-256
SHA-384 (supported only on the front end)
SHA-512 (supported only on the front end)

An MPX appliance supports certificates of 512 or more bits, up to the following sizes:

4096-bit server certificate on the virtual server
4096-bit client certificate on the service
4096-bit CA certificate (includes intermediate and root certificates)
4096-bit certificate on the back-end server
4096-bit client certificate (if client authentication is enabled on the virtual server)

A VPX virtual appliance supports certificates of 512 or more bits, up to the following sizes:

4096-bit server certificate on the virtual server
4096-bit client certificate on the service
4096-bit CA certificate (includes intermediate and root certificates)
4096-bit certificate on the back-end server
2048-bit client certificate (if client authentication is enabled on the virtual server)

Note

A Citrix ADC SDX appliance supports certificates of 512 or more bits. Each Citrix ADC VPX instance hosted on the appliance supports the certificate sizes listed earlier for a VPX virtual appliance. However, if an SSL chip is assigned to an instance, that instance supports the certificate sizes supported by an MPX appliance.

Add a certificate-key pair by using the CLI

在命令提示符下,键入以下命令to add a certificate-key pair and verify the configuration:

             add ssl certKey  -cert [(-key  [-password]) | -fipsKey ] [-inform ( DER | PEM )] [] [-expiryMonitor ( ENABLED | DISABLED ) [-notificationPeriod ]] show ssl certKey [] 
            

Example:

             添加ssl certKey sslckey cert server_cert。pem关键server_key.pem -password ssl -expiryMonitor ENABLED -notificationPeriod 30 Done Note: For FIPS appliances, replace -key with -fipskey show ssl certKey sslckey Name: sslckey Status: Valid, Days to expiration:8418 Version: 3 Serial Number: 01 Signature Algorithm: md5WithRSAEncryption Issuer: C=US,ST=SJ,L=SJ,O=NS,OU=NSSSL,CN=www.root.com Validity Not Before: Jul 15 02:25:01 2005 GMT Not After : Nov 30 02:25:01 2032 GMT Subject: C=US,ST=SJ,L=SJ,O=NS,OU=NSSSL,CN=www.server.com Public Key Algorithm: rsaEncryption Public Key size: 2048 Done 
            

Update or remove a certificate-key pair by using the CLI

To modify the expiry monitor or notification period in a certificate-key pair, use theset ssl certkey命令。To replace the certificate or key in a certificate-key pair, use theupdate ssl certkey命令。的update ssl certkeycommand has an extra parameter for overriding the domain check. For both commands, enter the name of an existing certificate-key pair. To remove an SSL certificate-key pair, use therm ssl certkeycommand, which accepts only theargument.

Example:

             set ssl certKey  [-expiryMonitor ( ENABLED | DISABLED ) [-notificationPeriod ]] update ssl certKey  [-cert  [-password]] [-key  | -fipsKey ] [-inform ] [-noDomainCheck] 
            

Add or update a certificate-key pair by using the GUI

Navigate toTraffic Management > SSL > Certificates, and configure a certificate-key pair.

Bind the certificate-key pair to the SSL virtual server

An SSL certificate is an integral element of the SSL encryption and decryption process. The certificate is used during an SSL handshake to establish the identity of the SSL server.

的certificate being used for processing SSL transactions must be bound to the virtual server that receives the SSL data. If you have multiple virtual servers receiving SSL data, a valid certificate-key pair must be bound to each of them.

You can use a valid, existing SSL certificate that you have uploaded to the Citrix ADC appliance. As an alternative for testing purposes, you can create your own SSL certificate on the appliance. Intermediate certificates created by using a FIPS key on the appliance cannot be bound to an SSL virtual server.

As a part of the SSL handshake, in the certificate request message during client authentication, the server lists the distinguished names (DNs) of all the certificate authorities (CAs) bound to the server from which it accepts a client certificate. If you do not want the DN name of a specific CA certificate to be sent to the SSL client, set the skipCA flag. This setting indicates that the particular CA certificate’s distinguished name must not be sent to the SSL client.

For details on how to create your own certificate, seeManaging Certificates.

Note: Citrix recommends that you use only valid SSL certificates issued by a trusted certificate authority.

Bind an SSL certificate-key pair to a virtual server by using the CLI

在命令提示符下,键入以下命令to bind an SSL certificate-key pair to a virtual server and verify the configuration:

- bind ssl vserver  -certkeyName  -CA -skipCAName - show ssl vserver

Example:

             bind ssl vs vs1 -certkeyName cert2 -CA -skipCAName Done sh ssl vs vs1 Advanced SSL configuration for VServer vs1: DH: DISABLED Ephemeral RSA: ENABLED Refresh Count: 0 Session Reuse: ENABLED Timeout: 120 seconds Cipher Redirect: DISABLED SSLv2 Redirect: DISABLED ClearText Port: 0 Client Auth: DISABLED SSL Redirect: DISABLED Non FIPS Ciphers: DISABLED SNI: DISABLED OCSP Stapling: DISABLED HSTS: DISABLED IncludeSubDomains: NO HSTS Max-Age: 0 SSLv2: DISABLED SSLv3: ENABLED TLSv1.0: ENABLED TLSv1.1: DISABLED TLSv1.2: DISABLED Push Encryption Trigger: Always Send Close-Notify: YES Strict Sig-Digest Check: DISABLED ECC Curve: P_256, P_384, P_224, P_521 1) CertKey Name: cert1 CA Certificate OCSPCheck: Optional CA_Name Sent 2) CertKey Name: cert2 CA Certificate OCSPCheck: Optional CA_Name Skipped 1) Cipher Name: DEFAULT Description: Default cipher list with encryption strength >= 128bit Done 
            

Unbind an SSL certificate-key pair from a virtual server by using the CLI

If you try to unbind a certificate-key pair from a virtual server by using theunbind ssl certKey command, an error message appears because the syntax of the command has changed. At the command prompt, type the following command:

unbind ssl vserver  -certkeyName

Example:

unbind ssl vserver vssl -certkeyName sslckey

Bind an SSL certificate-key pair to a virtual server by using the GUI

Navigate toTraffic Management > Load Balancing > Virtual Servers.
Open an SSL virtual server and, in Advanced Settings, click SSL Certificate.
Bind a server certificate or CA certificate to the virtual server. To add a server certificate as an SNI certificate, select Server Certificate for SNI.

SSL virtual server parameters

You can set the advanced SSL configuration for an SSL virtual server. Many of these parameters can also be set in an SSL profile. For information about the parameters that can be set in an SSL profile, seeSSL profile parameters.

Set SSL virtual server parameters by using the CLI

At the command prompt, type:

             set ssl vserver @ [-clearTextPort ] [-dh ( ENABLED |DISABLED ) -dhFile ] [-dhCount ][-dhKeyExpSizeLimit ( ENABLED | DISABLED )] [-eRSA ( ENABLED | DISABLED) [-eRSACount ]] [-sessReuse ( ENABLED | DISABLED )[-sessTimeout ]] [-cipherRedirect ( ENABLED | DISABLED ) [-cipherURL ]] [-sslv2Redirect ( ENABLED | DISABLED )[-sslv2URL ]] [-clientAuth ( ENABLED | DISABLED ) [-clientCert ( Mandatory | Optional )]] [-sslRedirect ( ENABLED | DISABLED )][-redirectPortRewrite ( ENABLED | DISABLED )] [-ssl2 ( ENABLED | DISABLED )] [-ssl3 ( ENABLED | DISABLED )] [-tls1 ( ENABLED | DISABLED )] [-tls11 ( ENABLED | DISABLED )] [-tls12 ( ENABLED | DISABLED )][-tls13 ( ENABLED | DISABLED )] [-SNIEnable ( ENABLED | DISABLED )][-ocspStapling ( ENABLED | DISABLED )] [-pushEncTrigger ] [-sendCloseNotify ( YES | NO )] [-dtlsProfileName ] [-sslProfile ] [-HSTS ( ENABLED | DISABLED )][-maxage ] [-IncludeSubdomains ( YES | NO )][-strictSigDigestCheck ( ENABLED | DISABLED )] [-zeroRttEarlyData (ENABLED | DISABLED )] [-tls13SessionTicketsPerAuthContext ] [-dheKeyExchangeWithPsk ( YES | NO )] 
            

Diffie-Hellman (DH) parameters

If you are using ciphers on the appliance that require a DH key exchange to set up the SSL transaction, enable DH key exchange on the appliance and configure other settings based on your network.

To list the ciphers for which DH parameters must be set by using the CLI, type: sh cipher DH.

To list the ciphers for which DH parameters must be set by using the configuration utility, navigate toTraffic Management > SSL > Cipher Groups, and double-clickDH.

For details on how to enable DH key exchange, seeGenerate a Diffie-Hellman (DH) key.

Configure DH parameters by using the CLI

在命令提示符下,键入以下命令to configure DH parameters and verify the configuration:

- `set ssl vserver  -dh

Example:

             set ssl vserver vs-server -dh ENABLED -dhFile /nsconfig/ssl/ns-server.cert -dhCount 1000 Done show ssl vserver vs-server Advanced SSL configuration for VServer vs-server: DH: ENABLED Ephemeral RSA: ENABLED Refresh Count: 1000 Session Reuse: ENABLED Timeout: 120 seconds Cipher Redirect: DISABLED SSLv2 Redirect: DISABLED ClearText Port: 0 Client Auth: DISABLED SSL Redirect: DISABLED Non FIPS Ciphers: DISABLED SNI: DISABLED OCSP Stapling: DISABLED HSTS: DISABLED HSTS IncludeSubDomains: NO HSTS Max-Age: 0 SSLv2: DISABLED SSLv3: ENABLED TLSv1.0: ENABLED TLSv1.2: ENABLED TLSv1.2: ENABLED 1) Cipher Name: DEFAULT Description: Predefined Cipher Alias Done 
            

Configure DH Parameters by using the GUI

Navigate toTraffic Management > Load Balancing > Virtual Servers, and open a virtual server.
In the SSL Parameters section, select Enable DH Param, and specify a refresh count and file path.

Ephemeral RSA

Ephemeral RSA allows export clients to communicate with the secure server even if the server certificate does not support export clients (1024-bit certificate). If you want to prevent export clients from accessing the secure web object or resource, you need to disable ephemeral RSA key exchange.

By default, this feature is enabled on the Citrix ADC appliance, with the refresh count set to zero (infinite use).

Note:

的ephemeral RSA key is automatically generated when you bind an export cipher to an SSL or TCP-based SSL virtual server or service. When you remove the export cipher, the eRSA key is not deleted but reused later when another export cipher is bound to an SSL or TCP-based SSL virtual server or service. The eRSA key is deleted when the system restarts.

Configure Ephemeral RSA by using the CLI

在命令提示符下,键入以下命令to configure ephemeral RSA and verify the configuration:

set ssl vserver  -eRSA (enabled | disabled) -eRSACount  show ssl vserver

Example:

             set ssl vserver vs-server -eRSA ENABLED -eRSACount 1000 Done show ssl vserver vs-server Advanced SSL configuration for VServer vs-server: DH: DISABLED Ephemeral RSA: ENABLED Refresh Count: 1000 Session Reuse: ENABLED Timeout: 120 seconds Cipher Redirect: DISABLED SSLv2 Redirect: DISABLED ClearText Port: 0 Client Auth: DISABLED SSL Redirect: DISABLED Non FIPS Ciphers: DISABLED SNI: DISABLED OCSP Stapling: DISABLED HSTS: DISABLED HSTS IncludeSubDomains: NO HSTS Max-Age: 0 SSLv2: DISABLED SSLv3: ENABLED TLSv1.0: ENABLED TLSv1.2: ENABLED TLSv1.2: ENABLED 1) Cipher Name: DEFAULT Description: Predefined Cipher Alias Done 
            

Configure Ephemeral RSA by using the GUI

Navigate toTraffic Management > Load Balancing > Virtual Servers, and open a virtual server.
In theSSL Parameterssection, selectEnable Ephemeral RSA, and specify a refresh count.

Session reuse

For SSL transactions, establishing the initial SSL handshake requires CPU-intensive public key encryption operations. Most handshake operations are associated with the exchange of the SSL session key (client key exchange message). When a client session is idle for some time and is then resumed, the SSL handshake is typically conducted all over again. With session reuse enabled, session key exchange is avoided for session resumption requests received from the client.

在Citrix ADC applian启用会话重用ce by default. Enabling this feature reduces server load, improves response time, and increases the number of SSL transactions per second (TPS) that the server can support.

Configure session reuse by using the CLI

在命令提示符下,键入以下命令to configure session reuse and verify the configuration:

             set ssl vserver  -sessReuse ( ENABLED | DISABLED ) -sessTimeout  show ssl vserver  
            

Example:

             set ssl vserver vs-ssl -sessreuse enabled -sesstimeout 600 Done show ssl vserver vs-ssl Advanced SSL configuration for VServer vs-ssl: DH: DISABLED Ephemeral RSA: ENABLED Refresh Count: 1000 Session Reuse: ENABLED Timeout: 600 seconds Cipher Redirect: DISABLED SSLv2 Redirect: DISABLED ClearText Port: 0 Client Auth: DISABLED SSL Redirect: DISABLED Non FIPS Ciphers: DISABLED SNI: DISABLED OCSP Stapling: DISABLED HSTS: DISABLED HSTS IncludeSubDomains: NO HSTS Max-Age: 0 SSLv2: DISABLED SSLv3: ENABLED TLSv1.0: ENABLED TLSv1.2: ENABLED TLSv1.2: ENABLED 1) CertKey Name: Auth-Cert-1 Server Certificate 1) Cipher Name: DEFAULT Description: Predefined Cipher Alias Done 
            

Configure session reuse by using the GUI

Navigate toTraffic Management > Load Balancing > Virtual Servers, and open a virtual server.
In the SSL Parameters section, select Enable Session Reuse, and specify a time for which to keep the session active.

SSL protocol settings

的Citrix ADC appliance supports the SSLv3, TLSv1, TLSv1.1, and TLSv1.2 protocols. These protocols can be set on the appliance as required by your deployment and the type of clients that connect to the appliance.

TLS协议版本1.0,1.1,和1.2 secure than older versions of the TLS/SSL protocol. However, to support legacy systems, many TLS implementations maintain backward compatibility with the SSLv3 protocol. In an SSL handshake, the highest protocol version common to the client and the SSL virtual server configured on the Citrix ADC appliance is used.

In the first handshake attempt, a TLS client offers the highest protocol version that it supports. If the handshake fails, the client offers a lower protocol version. For example, if a handshake with TLS version 1.1 is not successful, the client attempts to renegotiate by offering the TLSv1.0 protocol. If that attempt is unsuccessful, the client reattempts with the SSLv3 protocol. A “man in the middle” (MITM) attacker can break the initial handshake and trigger renegotiation with the SSLv3 protocol, and then exploit a vulnerability in SSLv3. To mitigate such attacks, you can disable SSLv3 or not allow renegotiation using a downgraded protocol. However, this approach might not be practical if your deployment includes legacy systems. An alternative is to recognize a signaling cipher suite value (TLS_FALLBACK_SCSV) in the client request.

A TLS_FALLBACK_SCSV value in a client hello message indicates to the virtual server that the client has previously attempted to connect with a higher protocol version and that the current request is a fallback. If the virtual server detects this value, and it supports a version higher than the one indicated by the client, it rejects the connection with a fatal alert. If a TLS_FALLBACK_SCSV is not included in the client hello message, or if the protocol version in the client hello is the highest protocol version supported by the virtual server, the handshake succeeds.

Configure SSL protocol support by using the CLI

在命令提示符下,键入以下命令to configure SSL protocol support and verify the configuration:

             set ssl vserver  -ssl2 ( ENABLED | DISABLED ) -ssl3 ( ENABLED | DISABLED ) -tls1 ( ENABLED | DISABLED ) -tls11 ( ENABLED | DISABLED ) -tls12 ( ENABLED | DISABLED ) show ssl vserver  
            

Example:

             set ssl vserver vs-ssl -tls11 ENABLED -tls12 ENABLED Done sh ssl vs vs-ssl Advanced SSL configuration for VServer vs-ssl: DH: DISABLED Ephemeral RSA: ENABLED Refresh Count: 0 Session Reuse: ENABLED Timeout: 120 seconds Cipher Redirect: DISABLED SSLv2 Redirect: DISABLED ClearText Port: 0 Client Auth: DISABLED SSL Redirect: DISABLED Non FIPS Ciphers: DISABLED SNI: DISABLED SSLv2: DISABLED SSLv3: ENABLED TLSv1.0: ENABLED TLSv1.1: ENABLED TLSv1.2: ENABLED Push Encryption Trigger: Always Send Close-Notify: YES 1 bound certificate: 1) CertKey Name: mycert Server Certificate 1 configured cipher: 1) Cipher Name: DEFAULT Description: Predefined Cipher Alias Done 
            

Configure SSL protocol support by using the GUI

Navigate toTraffic Management > Load Balancing > Virtual Servers, and open a virtual server.
In the SSL Parameters section, select a protocol to enable.

Close-notify

A close-notify is a secure message that indicates the end of SSL data transmission. A close-notify setting is required at the global level. This setting applies to all virtual servers, services, and service groups. For information about the global setting, see theGlobal SSL parameterssection later in this page.

In addition to the global setting, you can set the close-notify parameter at the virtual server, service, or service group level. You therefore have the flexibility of setting the parameter for one entity and unsetting it for another entity. However, make sure that you set this parameter at the global level. Otherwise, the setting at the entity level does not apply.

Configure the close-notify parameter at the entity level by using the CLI

At the command prompt, type any of the following commands to configure the close-notify parameter and verify the configuration:

To configure the close-notify parameter at the virtual server level, type:

set ssl vserver  -sendCloseNotify ( YES | NO ) show ssl vserver

To configure the close-notify parameter at the service level, type:

set ssl service  -sendCloseNotify ( YES | NO ) show ssl service

To configure the close-notify parameter at the service group level, type:

             设置ssl serviceGroup < serviceGroupName > -sendCloseNotify ( YES | NO ) show ssl serviceGroup  
            

Example:

set ssl vserver sslvsvr -sendCloseNotify YES Done

Configure a close-notify parameter at the entity level by using the GUI

Navigate toTraffic Management > Load Balancing > Virtual Servers, and open a virtual server.
In theSSL Parameterssection, selectSend Close-Notify.

Global SSL parameters

Advanced customization of your SSL configuration addresses specific issues. You can use theset ssl parametercommand or the configuration utility to specify the following:

Quantum size to be used for SSL transactions.
CRL memory size.
OCSP cache size.
Deny SSL renegotiation.
Set the PUSH flag for decrypted, encrypted, or all records.
Drop requests if the client initiates the handshake for one domain and sends an HTTP request for another domain.
Set the time after which encryption is triggered. Note: The time that you specify applies only if you use theset ssl vservercommand or the configuration utility to set timer-based encryption.

Configure global SSL parameters by using the CLI

在命令提示符下,键入以下命令to configure advanced SSL settings and verify the configuration:

             set ssl parameter [-quantumSize ] [-crlMemorySizeMB ] [-strictCAChecks (YES | NO)] [-sslTriggerTimeout ] [-sendCloseNotify (YES | NO)] [-encryptTriggerPktCount ] [-denySSLReneg ] [-insertionEncoding (Unicode|UTF-8)] [-ocspCacheSize ][- pushFlag ] [- dropReqWithNoHostHeader (YES | NO)] [-pushEncTriggerTimeout ] show ssl parameter 
            

Example:

             set ssl parameter -quantumSize 8 -crlMemorySizeMB 256 -strictCAChecks no -sslt iggerTimeout 100 -sendClosenotify no -encryptTriggerPktCount 45 -denySSLReneg no -insertionEncoding unicode -ocspCacheSize 10 -pushFlag 3 -dropReqWithNoHostHeader YES -pushEncTriggerTimeout 100 ms Done show ssl parameter Advanced SSL Parameters ----------------------- SSL quantum size: 8 kB Max CRL memory size: 256 MB Strict CA checks: NO Encryption trigger timeout 100 mS Send Close-Notify NO Encryption trigger packet count: 45 Deny SSL Renegotiation NO Subject/Issuer Name Insertion Format: Unicode OCSP cache size: 10 MB Push flag: 0x3 (On every decrypted and encrypted record) Strict Host Header check for SNI enabled SSL sessions: YES PUSH encryption trigger timeout 100 ms Done 
            

Configure global SSL parameters by using the GUI

Navigate toTraffic Management > SSLand, in the Settings group, selectChange advanced SSLsettings.

PUSH flag based encryption trigger mechanism

的encryption trigger mechanism that is based on the PSH TCP flag now enables you to do the following:

Merge consecutive packets in which the PSH flag is set into a single SSL record, or ignore the PSH flag.
Perform timer-based encryption, in which the time-out value is set globally by using theset ssl parameter -pushEncTriggerTimeout 命令。

Configure PUSH flag-based encryption by using the CLI

在命令提示符下,键入以下命令to configure PUSH flag-based encryption and verify the configuration:

set ssl vserver  [-pushEncTrigger ] show ssl vserver

Example:

             set ssl vserver vserver1 -pushEncTrigger always Done sh ssl vserver vserver1 Advanced SSL configuration for VServer vserver1: DH: DISABLED DH Private-Key Exponent Size Limit: DISABLED Ephemeral RSA: ENABLED Refresh Count: 0 Session Reuse: ENABLED Timeout: 120 seconds Cipher Redirect: DISABLED SSLv2 Redirect: DISABLED ClearText Port: 0 Client Auth: DISABLED SSL Redirect: DISABLED Non FIPS Ciphers: DISABLED SNI: DISABLED OCSP Stapling: DISABLED HSTS: DISABLED HSTS IncludeSubDomains: NO HSTS Max-Age: 0 SSLv2: DISABLED SSLv3: ENABLED TLSv1.0: ENABLED TLSv1.1: ENABLED TLSv1.2: ENABLED TLSv1.3: DISABLED Push Encryption Trigger: Always 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 ECC Curve: P_256, P_384, P_224, P_521 1) Cipher Name: DEFAULT Description: Default cipher list with encryption strength >= 128bit Done 
            

Configure PUSH flag-based encryption by using the GUI

Navigate toTraffic Management > Load Balancing > Virtual serversand open an SSL virtual server.
In theSSL Parameterssection, from thePUSH Encryption Triggerlist, select a value.

Support for TLS1.2 signature hash algorithm

的Citrix ADC appliance is completely TLS1.2 signature hash extension compliant.

In an SSL handshake, a client sends a list of supported signature hash (sighash) algorithms. The client uses the “signature_algorithms” extension to indicate to the server whichsighashalgorithm pairs might be used in the SSL handshake messages (SKE and CCV). The “extension_data” field of this extension contains a “supported_signature_algorithms” value in the Client Hello message. The SSL handshake proceeds if the server supports one of thesesighashalgorithms. If the server does not support any of these algorithms, the connection is dropped.

Similarly, if the server requests a client certificate for client authentication, the Certificate Request message contains a “supported_signature_algorithms” value. The client certificate is selected based on thissighashalgorithm.

Note:

的Citrix ADC appliance acts as a server to a client and as a client to the back-end server.

Previously, the appliance supported only RSA-SHA1 and RSA-SHA256 on the front end, and RSA-MD5, RSA-SHA1, and RSA-SHA256 on the back end. In addition, the VPX appliance supported DSA-SHA1 on the front end and back end.

的MPX/SDX/VPX appliance supports the followingsighashcombinations. On an SDX appliance, if an SSL chip is assigned to a VPX instance, the cipher support of an MPX appliance applies. Otherwise, the normal cipher support of a VPX instance applies.

On a VPX instance:
- RSA-MD5
- RSA-SHA1
- RSA-SHA224
- RSA-SHA256
- RSA-SHA384
- RSA-SHA512
- DSA-SHA1
- DSA-SHA224
- DSA-SHA256
- DSA-SHA384
- DSA-SHA512
On an MPX/SDX appliance with N3 chips:
- RSA-MD5
- RSA-SHA1
- RSA-SHA224
- RSA-SHA256
- RSA-SHA384
- RSA-SHA512
- ECDSA-SHA1
- ECDSA-SHA224
- ECDSA-SHA256
- ECDSA-SHA384
- ECDSA-SHA512
On an MPX/SDX appliance without N3 chips:
- RSA-MD5
- RSA-SHA1
- RSA-SHA224
- RSA-SHA256
- RSA-SHA384
- RSA-SHA512

By default, all thesighashalgorithms are enabled. However, you can enable only a fewsighashalgorithms by using the following command:

             set ssl parameter -sigDigestType  Parameters sigDigestType Signature digest algorithms supported by the appliance. The platform determines the list of algorithms supported by default. On VPX: RSA-MD5 RSA-SHA1 RSA-SHA224 RSA-SHA256 RSA-SHA384 RSA- SHA512 DSA-SHA1 DSA-SHA224 DSA-SHA256 DSA-SHA384 DSA-SHA512 On MPX with N3 cards: RSA-MD5 RSA-SHA1 RSA-SHA224 RSA- SHA256 RSA-SHA384 RSA-SHA512 ECDSA-SHA1 ECDSA-SHA224 ECDSA- SHA256 ECDSA-SHA384 ECDSA-SHA512 Other MPX Platforms: RSA-MD5 RSA-SHA1 RSA-SHA224 RSA-SHA256 RSA-SHA384 RSA- SHA512. set ssl parameter -sigDigestType RSA-SHA224 RSA-SHA256 RSA-SHA384 RSA-SHA512 
            

Validate the peer certificate

According to RFC 5246, the peer certificate must be signed using one of thesighashalgorithms included in the Client Hello extension. To do so, use the strictSigDigestCheck parameter. Depending on thesighashlist sent by the client, if you enable strictSigDigestCheck, the appliance returns a certificate signed by one of thesighashalgorithms mentioned in the Client Hello extension. If the peer does not have a proper certificate, the connection is dropped. If this parameter is disabled,sighashis not checked in the peer certificate.

You can configure a strict signature digest check on an SSL virtual server and service. If you enable this parameter on an SSL virtual server, the server certificate sent by the server must be signed by one of thesighashalgorithms listed in the Client Hello extension. If client authentication is enabled, then the client certificate received by the server must be signed using one of thesighashalgorithms listed in the certificate request sent by the server.

If you enable this parameter on an SSL service, the server certificate received by the client must be signed by one of thesighashalgorithms listed in the Client Hello extension. The client certificate must be signed using one of thesighashalgorithms listed in the certificate request message.

If the default profile is enabled, you can use it to configure a strict signature digest check on an SSL virtual server, SSL service, and SSL profile.

Configure strict signature digest check on an SSL virtual server, service, or profile by using the CLI

At the command prompt, type:

             set ssl vserver  -strictSigDigestCheck ( ENABLED | DISABLED ) set ssl service  -strictSigDigestCheck ( ENABLED | DISABLED ) set ssl profile -strictSigDigestCheck ( ENABLED | DISABLED ) Parameters strictSigDigestCheck Check whether peer entity certificate is signed using one of the signature-hash algorithms supported by the Citrix ADC appliance. Possible values: ENABLED, DISABLED Default: DISABLED 
            

Example:

             set ssl vserver v1 –strictSigDigestCheck Enabled set ssl service s1 –strictSigDigestCheck Enabled set ssl profile p1 –strictSigDigestCheck Enabled 
            

Important:

If DH, ECDHE, or ECDSA ciphers are configured on the appliance, the SKE message must be signed using one of thesighashcommon to the client list and the list configured on the appliance. If there is no commonsighash, the connection is dropped.

的official version of this content is in English. Some of the Citrix documentation content is machine translated for your convenience only. Citrix has no control over machine-translated content, which may contain errors, inaccuracies or unsuitable language. No warranty of any kind, either expressed or implied, is made as to the accuracy, reliability, suitability, or correctness of any translations made from the English original into any other language, or that your Citrix product or service conforms to any machine translated content, and any warranty provided under the applicable end user license agreement or terms of service, or any other agreement with Citrix, that the product or service conforms with any documentation shall not apply to the extent that such documentation has been machine translated. Citrix will not be held responsible for any damage or issues that may arise from using machine-translated content.

SSL offloading configuration

June 15, 2021

Contributed by:

June 15, 2021

Contributed by:

SSL offloading configuration

Enable SSL

Enable SSL processing by using the CLI

Enable SSL processing by using the GUI

Configure services

Add a service by using the CLI

Modify or remove a service by using the CLI

Configure a service by using the GUI

SSL virtual server configuration

Add an SSL-based virtual server by using the CLI

Modify or remove an SSL-based virtual server by using the CLI

Configure an SSL-based virtual server by using the GUI

Bind services to the SSL virtual server

Bind a service to a virtual server by using the CLI

Unbind a service from a virtual server by using the CLI

Bind a service to a virtual server by using the GUI

Configure an SNI virtual server for secure hosting of multiple sites

Bind multiple server certificates to a single SSL virtual server by using the CLI

Bind multiple server certificates to a single SSL virtual server by using the GUI

Support for SNI on the back-end service

Configure SNI on the back-end service by using the CLI

Configure SNI on the back-end service by using the GUI

Bind a secure monitor to an SNI-enabled back-end service

Configure and bind a secure monitor to an SNI-enabled back-end service by using the CLI

Configure and bind a secure monitor to an SNI-enabled back-end service by using the GUI

Add or update a certificate-key pair

Add a certificate-key pair by using the CLI

Update or remove a certificate-key pair by using the CLI

Add or update a certificate-key pair by using the GUI

Bind the certificate-key pair to the SSL virtual server

Bind an SSL certificate-key pair to a virtual server by using the CLI

Unbind an SSL certificate-key pair from a virtual server by using the CLI

Bind an SSL certificate-key pair to a virtual server by using the GUI

SSL virtual server parameters

Set SSL virtual server parameters by using the CLI

Diffie-Hellman (DH) parameters

Configure DH parameters by using the CLI

Configure DH Parameters by using the GUI

Ephemeral RSA

Configure Ephemeral RSA by using the CLI

Configure Ephemeral RSA by using the GUI

Session reuse

Configure session reuse by using the CLI

Configure session reuse by using the GUI

SSL protocol settings

Configure SSL protocol support by using the CLI

Configure SSL protocol support by using the GUI

Close-notify

Configure the close-notify parameter at the entity level by using the CLI

Configure a close-notify parameter at the entity level by using the GUI

Global SSL parameters

Configure global SSL parameters by using the CLI

Configure global SSL parameters by using the GUI

PUSH flag based encryption trigger mechanism

Configure PUSH flag-based encryption by using the CLI

Configure PUSH flag-based encryption by using the GUI

Support for TLS1.2 signature hash algorithm

Validate the peer certificate

Configure strict signature digest check on an SSL virtual server, service, or profile by using the CLI

In this article