Advanced Expressions Evaluating Text | Citrix Systems 9.2 specification

CHAPTER 4

Advanced Expressions: Evaluating

Text

You can configure an advanced expression to examine text in a request or a response. For example, a expression can perform string matching on the following types of data:

•An HTTP header type

•An HTTP header value

•A user or group name in an HTTP request

•A file type in a URL

•A string in an HTTP POST body

You can configure text expressions to be case sensitive or case insensitive and to use or ignore spaces.You can also configure complex expressions for text, for example, by skipping x number of bytes before starting a search of a POST body or by finding a string that occurs after the end of another string.

The rest of this chapter discusses the expression prefixes that extract text and the operations that you can perform on the extracted text.

In This Chapter

About Text Expressions

Expression Prefixes for Text

Operations on Text

Complex Operations on Text

Note: You can apply complex functions to text expressions. For example, you can transform a text string to a name-value list. Or, you can perform a match against a pattern or set of patterns. For information on these advanced text expressions, see “Advanced Expressions: String Sets, String Patterns, and Data Formats,” on page 157.

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Citrix Systems 9.2 manual Advanced Expressions Evaluating Text

Contents

Citrix NetScaler Citrix NetScaler Policy Configuration and Reference Guide Copyright and Trademark Notice Contents Chapter Converting Text to Hexadecimal Format Contents Citrix NetScaler Policy Configuration and Reference Guide Contents Vii Blocking Access by Robots Accommodating Browser Dependent ContentBlocking Access to Inline Images Reducing Web Server Redirects About This Guide Preface Citrix NetScaler Policy Configuration and Reference Guide Preface New in This ReleaseAudience Convention Meaning Boldface Formatting ConventionsFormatting Conventions To view the documentation Getting Service and SupportRelated Documentation To provide feedback from the Knowledge Center home Documentation Feedback Advanced and Classic Policies Introduction to Policies Expressions Basic Components of an Advanced or a Classic Policy Benefits of Using Advanced Policies NetScaler Feature, Policy Type, and Policy Usage How Different NetScaler Features Use PoliciesChapter Introduction to Policies and Expressions DNS Authorization Authorization policies authorize usersAssociated cache server AAA Traffic Classic Authorization policies, however, can be Access ClassicAbout Actions and Profiles Functions Feature Use of an Action Use of a Profile Use of Actions and Profiles in Different NetScaler FeaturesPre-Authentication. Uses Authorization. Uses Allow Server About Policy Bindings About Evaluation Order of Policies About Advanced Expressions Advanced and Classic ExpressionsOrder of Evaluation Based on Traffic Flow About Classic Expressions Chapter Before You Proceed Citrix NetScaler Policy Configuration and Reference Guide Configuring Advanced Policies Argument Specifies Creating or Modifying an Advanced PolicyAdvanced-Policy Parameters Following is an example of a Rewrite policy and action Policy Configuration Examples Binding Advanced Policies Feature-Specific Differences in Policy BindingsFeature-Specific Bindings for Advanced Policies NetScalers integrated Policies Global default Responder function Policy labelProvide rules for modifying Address of the incoming Bind Points and Order of Evaluation Entries in a Policy Bank Advanced Policy Evaluation Across FeaturesChapter Configuring Advanced Policies Optional Evaluation Order Within a Policy BankFormat of Each Entry in a Policy Bank How Policy Evaluation Ends Example How Features Use Actions After Policy EvaluationBinding a Policy Globally Details pane, click Feature Name policy manager Binding a Policy to a Virtual Server Displaying Policy Bindings Unbinding an Advanced Policy Unbind responder global policyName Creating a Policy Label Creating Policy Labels To create a policy label by using the configuration utility Binding a Policy to a Policy Label Configuring a Policy Label or Virtual Server Policy BankEntries in a Policy Bank Attribute Description Example Configuring a Policy Label Choices are Integrated Caching, Rewrite, or Responder Configure Virtual Server dialog box click the Policies tab Configuring a Policy Bank for a Virtual Server Chapter Configuring Advanced Policies At the NetScaler command prompt, for the Responder, type Configuring and Binding Policies with the Policy Manager Click Regenerate Priorities To remove unused policies by using the Policy Manager Citrix NetScaler Policy Configuration and Reference Guide Configuring Advanced Expressions Getting Started Basic Elements of an Advanced Expression Expression Characteristics Prefixes Http.res.header.myheader Features Content Switching Feature Types of Expression Prefix Used in the FeatureSingle-Element Expressions Operations Operation Determines whether or not Basic Operations on Expression PrefixesBasic Operations for Expressions Basic Types of Operations Configuring Advanced Expressions Getting StartedCompound Advanced Expressions Parentheses in Compound Expressions Booleans in Compound ExpressionsCompound Operations for Strings String-Based Operations for Compound Advanced Expressions Logical operations on strings Arithmetic Operations for Compound Advanced Expressions Compound Operations for Numbers Expression on the right Num % numReturns 12 binary Result of applying the ~ operator is -11 a binary 1110011 Whole expression evaluates to 8 binary Binary 1100 and numeric.expression2 returns 10 binaryRight-side number argument number of bits Following example assumes that numeric.expression1 returns Integer Value Following is an example Number .ADDNumber .SUB Integer Number value Following is an example Integer Integer argument Following is an example Number .LENumber .LT Binary value of 10 is 1010, and the result of applying 1110011, 32 bits total with all ones to the left Result of applying the Bitneg operator is -11 a binaryExpression as an argument rather than an integer Assumes that numeric.expression returns 12 binary Caret performs a similar function to BITXOR, but takes Bitxor operator to the entire expression is 6 binaryAnother expression as an argument rather than an integer Number.LSHIFT Double .ADDi Number.RSHIFTValue represented by double Parameters Value represented by double is greater than or equal to Double .GEiDouble .GTi Value represented by double is greater than the argument Classic Expressions in Advanced Expressions Configuring Advanced Expressions in a Policy Following is an example of configuring a caching policy HTTP.REQ.BODY1000.BETWEENthis,that Click Advanced Expressions Configuring Named Advanced Expressions Chapter Citrix NetScaler Policy Configuration and Reference Guide Advanced Expressions Evaluating Text About Operations on Text About Text Expressions Chapter Advanced Expressions Evaluating Text Compounding and Precedence in Text ExpressionsCategories of Text Expressions Guidelines for Text Expressions Expression Prefixes for Text in Http Requests and Responses Expression Prefixes for TextHttp Expression Prefixes that Return Text Prefix Description Myhost.com8080, the domain is myhost.com Returns the domain name part of the host name. ForReturns incorrect results if the host name has an IP Address. For information on expressions for IP URL LISTT,.COUNT LISTT,. IGNOREEMPTYELEMENTS.COUNT HTTP.REQ.USER.EXTERNALGROUPS HTTP.REQ.USER.GROUPS For example, the following expression returns a Returns a list of internal groups to which the userUser belongs HTTP.REQ.USER.INTERNALGROUPS Group Returns the Http version listed in the request Default value of 80 or 443 for Https connectionsReturns a portion of the Http response body. Integer argument Expression Prefixes for VPNs and Clientless VPN and Clientless VPN Description Expression VPN and Clientless VPN Expression Prefixes that Return Text When evaluating this header By default, is not considered an empty elementEvaluates the server portion of the host name Extracts a slash- / separated list from the path Evaluates the protocol in the URL Extracts a name-value list, using the =Delimiters from the query string in a URL This method ignores the empty elements in a Hostname List delimiter is a comma , the following list Ignores empty elements in a list. For example, ifHas an empty element following a=10 Evaluating this header Example, the following list contains an empty Ignores empty elements in a name-value list. ForElement after a=10 As another example, consider the following http Is case insensitive Results in Boolean True if the host nameFollowing expression returns True Evaluates the server part of the host name For example, if the delimiter in a list is , This method ignores the empty elements in a listEntry a=10 Consider the following header Preceding example, the element following Example, the following list uses a semicolon=11 is not considered an empty element Evaluating the same header Basic Operations on Text Operations on TextBasic Operations on Text Returns a Boolean True value if the target contains Operations for Controlling Case Sensitivity Operations for Calculating the Length of a StringOperations on Case Sensitivity of Text Basic Text Operation Description Operations on the Length of a String Complex Operations on TextOperations on Strings Based on a Character Count Case Operation Description Basic Operations on a Portion of a String Operations on a Portion of a StringCharacter Count Operation Description Object of 0 length Object is greater than or equal to the sum starting string Returns a Boolean True value if the length of the textMatches starting string, and if the suffix of the target Matches ending string Operation Description Converting Text to a Hash Value Base64 encoding algorithm Operator DescriptionApplying the Base64 decoding algorithm. The operation Raises an Undef if text is not in B64-encoded format Converting Text to Hexadecimal Format Citrix NetScaler Policy Configuration and Reference Guide Advanced Expressions Working with Dates, Times, and Numbers Format of Dates and Times in an Expression Expressions for the NetScaler System Time Dates and Times in a Rewrite Action NetScaler Time Description Operation Expressions that Return NetScaler System Dates and Times Advanced Expressions Working with Dates, Times, and Numbers Is equal to the time argument Scheduled reboot, and returns an integerSys.time.leGMT 2006 True in this example False depending on the current timezone Time2 Expressions for SSL Certificate Dates True SSL Certificate Operation Description 10h 15m 30s, and it is the first Sunday of the month For example, if the current time is GMT 2005 MayYou can specify the following evaluation results for This example are in parentheses Extracts the last hour that the certificate is valid Closest boot time is in the past, the integer isReturns a Boolean True if the time precedes or is Equal to the time argument If it is in the future, the integer is positive System time and the specified time and returns anExtracts the last weekday that the certificate is valid To give the weekday in the time value Time1, time2 arguments. Both the time1, time2 Returns a Boolean True if the time value is betweenArguments must be fully specified LOCAL, and time2 must be bigger than time1 After or equal to the time argument Returns a Boolean True if the time is greater thanResults are in parentheses Returns a Boolean True if the time occurs after Returns the current month as an integer from Extracts the last minute that the certificate is validReturns the number of seconds between the current NetScaler system time and the specified time as an Returns the current second as an integer from 0 to Extracts the last second that the certificate is valid6 Saturday Element of time from time2, it is assumed to have Prefixes That Evaluate Http Date Headers Expressions for Http Request and Response Dates 111 Citrix NetScaler Policy Configuration and Reference Guide Advanced Expressions Parsing HTTP, TCP, and UDP Data About Evaluating the Payload Body About Evaluating Http and TCP Payload 115 Expressions for Http Headers Http Header Prefix Description Prefixes for Http HeadersPrefixes That Extract Http Headers Advanced Expressions Parsing HTTP, TCP, and UDP Data As a slash- / separated list. Multiple Returns the value of Path field of the cookieFirst instance is returned For example, the following is a cookie with Operate as a comma-separated list Returns the value of Port field of the cookieFrom Set-Cookie Customer = ABC PATH=/a/b/c PORT= 80 First cookie with the specified name. For Returns the value of the Domain fieldExample, the following expression returns a DOMAIN=.xyz.com From the cookie Set-Cookie Customer Named cookie as a , separated list. For Operations That Evaluate Http Headers Operations for Http HeadersReturns the value of Version field of the nth Header type exists Following is an example of request with two headers Any instance of the header valueFollowing returns a Boolean True Does not concatenate the different values Instance to the first STR stringFollowing is an example of a request Following extracts the string def from the last Occurs instance number of places before the final Or a response. This operation returns the header thatUsed in bidirectional policies Instance number argument cannot exceed Operations for Cache-Control Headers Prefixes for Cache-Control HeadersPrefixes That Extract Cache-Control Headers Cannot exceed Http Header Operation Description Operations That Evaluate Cache-Control Headers127 Has the value Max-Stale Has the value Min-FreshHas the value Must-Revalidate Has the value No-Transform Expressions for Extracting Segments of URLs Prefixes That Extract URLs Expressions for Numeric Http Payload Data Other Than DatesPrefixes That Evaluate Http Request or Response Length URL Prefix Description Html or XML Operation Description Operations That Evaluate Html and XML EncodingReturns the response status code Specifies how to treat the plus character +. Where xx is a hex-based representationConverts unsafe URL characters to %xx values Read-only operation Where the colon is the Ascii equivalent With the character Y where XXX representsDecoded to http//, where the colon is Where WW and XX represent two distinct GET Operation Description Expressions for TCP, UDP, and Vlan DataPrefixes that Extract TCP and UDP Data MX mail exchanger. This DNS record describes Enables locating the domain name that isDomain and the priority for each server NS. This is a name server record that includes a XPath and Json Expression Prefixes that Return Text XPath and Json Expressions XPath string conversion routine Or a string. Node-sets are converted toFile Book creator person Namename , titletitle Json file and returns a Boolean True if That are enclosed by /Book a node-set For example, consider the following JsonFirst 1000 bytes of the body of the Json File and returns the corresponding string MARKUPxp%/Book/creator% Text.XPATHWITHBytes of the body Citrix NetScaler Policy Configuration and Reference Guide About SSL and Certificate Expressions Advanced Expressions Parsing SSL Certificates Returns the SSL client certificate in the current Prefixes for Text-Based SSL and Certificate DataSSL transaction SSL cryptographic cipher is exportable Advanced Expressions Parsing SSL Certificates Prefixes for Numeric Data in SSL CertificatesExpressions for SSL Certificates Based on the preceding Issuer definition Issuer in the certificate as a name-value list. AnReturns a Boolean True if the client has an SSL Returns the Distinguished Name DN An Authority Key Identifier extension Returns the Issuer Distinguished NameCertificate as a name-value list. An equals sign = is the delimiter for the name and the value False IGNOREEMPTYELEMENTS.COUNT CLIENT.SSL.CLIENTCERT.ISSUER Citrix NetScaler Policy Configuration and Reference Guide Expressions for IP Addresses and IP Subnets Operations for IPV4 Addresses Prefixes for IPV4 Addresses and IP SubnetsPrefixes That Evaluate IP and MAC Addresses Operations on IPV4 Addresses Qual1.qual2.qual3.qual4.qual5.qual6 About IPv6 Expressions IPv6 Expression Prefixes that Return Text Expression Prefixes for IPv6 AddressesIP header Returns the IPv6 address in the source field of the IP IPv6 Operation Description Operations for IPV6 PrefixesOperations That Evaluate IPv6 Addresses Prefixes for MAC Addresses Expressions for MAC AddressesOperations for MAC Addresses Prefixes That Evaluate MAC Addresses 155 Expressions for Numeric Client and Server DataPrefixes That Evaluate Numeric Client and Server Data Citrix NetScaler Policy Configuration and Reference Guide Matching Text With Strings in a Set Matching Operators Description Operators That Use a Pattern SetPatternsetname To patternsetname Setname Name Configuring a Pattern Set 161 At a NetScaler command prompt, type Add policy patset myPatSet 163 Matching Text With a Pattern 165 Basic Characteristics of Regular ExpressionsOperations for Regular Expressions Regular expression argument. If the regular Selects text that precedes the string that matchesFrom text/plain Expression does not match any text in the target Settextmodeignorecase Regular Expression Operation Description Text following the string that matches Insensitive, multi-line match, where the dotHeader value. The header instances are matched From the last to the first Following example selects NS-CACHE-9.0 Transforming Text and Numbers into Different Data TypesFirst Typecasting Operations Are ignored If the current text mode is Ignorecase and you specifyAs the delimiter, an uppercase P is not treated as a Delimiter Urlencoded by default Hostname path? query, and the text mode is set toTreats a numeric string like an IP address For example, the following policy matches Http requests String, adds 4 to the number, and inserts an Http header Following policy extracts a numeric portion of a queryFor example, this policy would extract 4444 from Following Http response header HTTP.REQ.COOKIE.TYPECASTHTTPHEADERT HTTP.REQ.SETCOOKIEHTTP.REQ.COOKIE.TYPECASTHTTPHEADER That you specify in a name argument Converts the designated text to a multi-line Http headerFor example, the following expression converts MyHeader to InHeader Betweengmt 2004, GMT 2006 True Eqgmt 2005 True Time value argument tEqgmt 2005 Dec False EQLocal 2005 May True or FALSE, depending on Gtgmt 2005 Jan True Gtgmt 2004 TrueGTLocal 2005 May True or FALSE, depending on Gtgmt 8h True Legmt 2005 Dec True Legmt 2006 TrueLELocal 2005 May True or FALSE, depending on Legmt 8h False Time is in the future scheduled reboot time, the integer is Most recent reboot or the number of seconds to the nextValue as an integer that ranges from 0 to Value as an integer that ranges from 1 January to Time1 and time2 Double to an integer Extracts the year from the current system time and returnsTransforms the double-precision number represented by Expressions for Controlling the Traffic Rate Advanced Policies Controlling Rate of TrafficAbout Policies that Monitor the Traffic Rate Configuring Policies That Control the Traffic Rate Chapter About Http Callout Policies About Calling Out to an External Application 187 Following is an example of a response Parameter Specifies Configuring an Http Callout PolicyElements in an Http Callout Policy Server mutually Attribute-based Http Method httpMethodExpression that derives the value. Examples URL stem expression urlStemExpr Expression to 8191 characters Example, if you configure a return type of text, the resultNetScaler does not check the validity of this request. You Must manually validate the request 191 Examples To modify a callout policy using the NetScaler command line To view a callout policy using the NetScaler command line To delete a callout policy using the NetScaler command lineInvoking an Http Callout Policy 193 If the return type is NUM, the following expression is valid 195 Citrix NetScaler Policy Configuration and Reference Guide Where Classic Policies Are Used Configuring Classic Policies Expressions Http Auditing of user access Configuring Classic Policies and Expressions Click Policies Viewing Classic Policies 201 Configuring a Classic Policy To create a classic policy using the NetScaler command line At the command line, type 203 Configuring a Classic Expression REQ.IP.SOURCEIP == 200.0.0.0 -netmask 205 Flow Type.protocol.qualifier.operator.value.header Name 207 Binding a Classic Policy Configure Virtual Server dialog box, click the Policies tab 209 Creating Named Classic Expressions Citrix NetScaler Policy Configuration and Reference Guide Expression Prefix Descriptions Expressions ReferenceAdvanced Expressions Citrix NetScaler Policy Configuration and Reference Guide Appendix a Expressions Reference Operates on the Vlan through which the current Expression Prefixes for Text in Http Ignores spaces in the data. See the table Http Appendix a Expressions Reference 217 Obtains the Expires field of the cookie as a date Appendix a Expressions Reference 219 SERVER.INTERFACE.ID.EQLA/1 Appendix a Expressions Reference 221 Ignores spaces in the data. For an example, see VPNs, on Appendix a Expressions Reference 223 Expression Element Definition Classic ExpressionsOperators Appendix a Expressions Reference 225 General Expressions REQ.HTTP.URLQUERYLEN REQ.SSL.CLIENT.CERT.ISSUERREQ.SSL REQ.SSL.CLIENT.CERT Appendix a Expressions Reference 227 Actual Expression Definition Client Security ExpressionsExpression Element Expression Definition Network-Based ExpressionsAppendix a Expressions Reference 229 File System Expressions Date/Time ExpressionsTime Date Appendix a Expressions Reference 231 Built-In Named Expressions General Always returns a value of False Appendix a Expressions Reference 233 Nstrue Nsurlpathbin NsfarclientNsmsexcel Nsmsie Nsmsppt Nsmsword Appendix a Expressions Reference 235 Built-InNamed Expressions Anti-VirusBuilt-InNamed Expressions Personal Firewall Any version of Norton Internet Security Built-InNamed Expressions Client SecurityExpression Definition Norton Internet Security Expression Type Sample Expressions Summary Examples of Advanced Expressions and PoliciesExamples of Advanced Expressions Look for a particular file type in an Content-Type headerHttp request based on the file Extension Purpose Example Examples of Advanced Expressions and Policies This policy uses To https// in all URLsResponder functionality Modify a URL to redirect Through unchanged Limit the numberCheck the client IP NS-Client header Remove old headers fromRequest and insert an NS-Client header, Request, insert anThen modify the insert Header action so that Citrix NetScaler Policy Configuration and Reference Guide Redirecting an External URL to an Internal URL Tutorial Examples of Advanced Policies for Rewrite Bind the policy globally Redirecting Http to Https Redirecting a QueryAppendix C 247 Removing Unwanted Headers 249 Reducing Web Server RedirectsMasking the Server Header Add rewrite policy polmask-server true actmask-server Tutorial Examples of Classic Policies Citrix NetScaler Policy Configuration and Reference Guide Appendix D Tutorial Examples of Classic Policies 253 REQ.HTTP.HEADER URL Contains string Appendix D Tutorial Examples of Classic Policies 255 Application Firewall Policy to Protect Scripted Web Pages DNS Policy to Drop Packets from Specific IPs Add dns policy polddosdrop SSL Policy to Require Valid Client Certificates Citrix NetScaler Policy Configuration and Reference Guide Migration of Apache modrewrite Rules to Advanced Policies NetScaler solution for converting a URL Apache modrewrite solution for converting a URLConverting URL Variations into Canonical URLs Converting Host Name Variations to Canonical Host Names NetScaler solution for moving the document root Apache modrewrite solution for moving the document rootMoving a Document Root Appendix E Working with Structured Home Directories Moving Home Directories to a New Web Server NetScaler solution for structured home directories Apache modrewrite solution for structured home directoriesNetScaler solution for redirection if a URL is wrong method Redirecting Invalid URLs to Other Web Servers Rewriting a URL Based on Time NetScaler solution for rewriting a URL based on the time 265 Redirecting to a New File Name Invisible to the UserRedirecting to New File Name User-Visible URL Apache modrewrite solution for browser-specific settings Accommodating Browser Dependent Content 267 Blocking Access by Robots Creating Extensionless Links Blocking Access to Inline ImagesNetScaler solution for blocking access to an inline image NetScaler policy for adding a .php extension to all requests 269 Redirecting a Working URI to a New Format Apache modrewrite solution NetScaler solution using regular expressions NetScaler solutionNetScaler solution using pattern sets Ensuring That a Secure Server Is Used for Selected Pages Bind patset pat1 page4 Bind patset pat1 page5 Operators for Extracting and Evaluating Numeric Data New Advanced Expression Operators in This ReleaseNew Operators for Extracting and Evaluating Numeric Data Number.TYPECASTIPADDRESSAT Operators Operation Operators for Extracting and Evaluating TextNew Operators for Evaluating Text Operators for the Client and ipv6 Expression Prefixes Operators for Extracting and Evaluating Http DataNew Operators for Extracting and Evaluating Http data Operators for Client and ipv6 Expression Prefixes Operators for Evaluating Groups to Which a User Belongs XPath and Json Operators for Evaluating XML and Json DataXPath and Json Operators for Evaluating XML and Json Text Operators for Evaluating Groups to Which a User Belongs Index Introduction to 224 migration to advanced RES.VLANID Index 279 CLIENT.ETHER.DSTMAC HTTP.RES.SETCOOKIE2.COOKIEname, i Index Omain 82 VPN.CLIENTLESSHOSTURL.HOSTNAME.E Authkeyid Citrix NetScaler Policy Configuration and Reference Guide Index Useinvocationresult VPN 65 Character 57 ? character Citrix NetScaler Policy Configuration and Reference Guide