Citrix Systems 9.2 manual Operator Description, Base64 encoding algorithm

92 Citrix NetScaler Policy Configuration and Reference Guide

Encoding and Decoding Text by Applying the

Base64 Encoding Algorithm

The following two operators encode and decode a text string by applying the

Base64 encoding algorithm:

Operators for Encoding and Decoding a Text String by Using Base64 Encoding

Operator	Description
text.B64ENCODE	Encodes the text string (designated by text) by applying the
	Base64 encoding algorithm.
text.B64DECODE	Decodes the Base64-encoded string (designated by text) by
	applying the Base64 decoding algorithm. The operation
	raises an UNDEF if text is not in B64-encoded format.

Refining the Search in a Rewrite Action by Using the EXTEND Operator

The EXTEND operator is used in rewrite actions that specify patterns or pattern sets and target the bodies of HTTP packets. When a pattern match is found, the EXTEND operator extends the scope of the search by a predefined number of bytes on both sides of the matching string. A regular expression can then be used to perform a rewrite on matches in this extended region. Rewrite actions that are configured with the EXTEND operator perform rewrites faster than rewrite actions that evaluate entire HTTP bodies using only regular expressions.

The format of the EXTEND operator is EXTEND(m,n), where m and n are the number of bytes by which the scope of the search is extended before and after the matching pattern, respectively. When a match is found, the new search scope comprises m bytes that immediately precede the matching string, the string itself, and the n bytes that follow the string. A regular expression can then be used to perform a rewrite on a portion of this new string.

The EXTEND operator can be used only if the rewrite action in which it is used fulfills the following requirements:

•The search is performed by using patterns or patterns sets (not regular expressions)

•The rewrite action evaluates only the bodies of HTTP packets.

Additionally, the EXTEND operator can be used only with the following types of rewrite actions:

•replace_all

•insert_after_all