When configuring custom controls, some allow you to define with regular expressions (regex) values. The characters and limitations are:

• Metacharacters Supported by Zscaler

  Metacharacter (POSIX ERE)	Definition	Supported by Zscaler?
  .	Matches any single character	Supported
  []	Matches a single character from those given between the brackets, matches character ranges (e.g., [a-z])	Supported
  [^ ]	Matches a single character not from those given between ^ and ]	Supported
  ^	Matches the starting position within the string	Not Supported
  $	Matches the ending position within the string	Not Supported
  ()	Defines a capture group	Capture groups are not supported. Parentheses can be used for bounding subexpressions.
  \n	References a capture group	Not Supported
  *	Repeats the preceding element 0 or more times	Supported
  {m,n}	Matches the preceding element at least m times and not more than n times. Requires m is less than or equal to n.	Both m and n must be between 0 and 100. A value for n is required, but m can be omitted (0 is assumed).
  ?	Repeats the preceding element 0 or 1 times	Supported
  +	Repeats the preceding element 1 or more times	Supported
  |	Matches either the expression before or the expression after the operator (e.g., "abc|def" matches "abc" or "def")	Supported

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• Shorthand Character Classes Supported by Zscaler

  Character class	Definition	Supported by Zscaler?
  \d	Matches any single character that is a digit (i.e. [0-9])	Supported
  \D	Matches any single character that is a non-digit	Supported
  \s	Matches any single horizontal whitespace character across a single line (i.e. a space " " or tab)	Supported
  \S	Matches any single non-whitespace character	Supported
  \w	Matches any single word character (i.e. ASCII characters [A-Za-z0-9_])	Supported
  \W	Matches any single non-word character	Supported
  \b	Matches any single word boundary	Supported

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• No Nested Repeats

  A repeat of an expression containing a repeat (*, +, ?, or {m,n}) is not supported. The prohibited repeated elements are in red text below:

  Incorrect Usage	Correct Usage
  \d-[A-Z]{2}?X - Matches "5-X" or "5-GAX"	\d-([A-Z][A-Z])?X
  (\d{3}-){1,2}\d{4} - Matches "555-555-5555" or "555-5555" \d{3}-(\d{3}-)?\d{4}	\d{3}-(\d\d\d-)?\d{4}

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• Base Token Requirement

  The regex value must begin with a simple sequence of alphabetic and numeric characters of a known length called the "base token."

  The first part can only include:

  • literal alphabetic characters (e.g., "A")
  • literal numeric characters (e.g., "5")
  • special characters (e.g., "@", "#")
  • classes of only alphabetic characters or numeric characters (e.g., "[A-N]", "\d")
  • bounded repeats (e.g., "{3}", "{1,5}")
  • 8 or fewer branches
  • shorthand characters (e.g., "\b", "\s")

  Shorthand characters can be followed by a special character (e.g., "\b%abc", "\s[%@]abc"). A base token can also have up to two nested shorthand characters (e.g., "\b\sabc", "\b[\s\W]abc").

  The base token must end with an expression that is non-alphanumeric (e.g., ";"), or with the end of the regex value. The following are examples of valid and invalid base tokens (with the prohibited element in red text):

  • The base token must be non-zero length.

  Example - US phone numbers:

  • Incorrect Usage: (1-)?\d{3}-\d{3}-\d{4} - Starts with an optional expression.
  • Incorrect Usage: (CA)-\d{6} - Starts with grouping.
  • Correct Usage: Use multiple values.
    • 1-\d{3}-\d{3}-\d{4} - Starts with a single-number token.
    • \d{3}-\d{3}-\d{4} - Starts with a three-number token.
  • The initial sequence must be all alphabetic characters or all numeric characters. It cannot be both.

  Example - IPv4 Address in dotted-quad notation:

  • Incorrect Usage: [0-9.]{7,15} - Ambiguous mix of numeric characters and punctuation.
  • Correct Usage: \d{1,3}\.\d{1,3}\.\d{1,3}\.\d{1,3} - Starts with 1-3 numeric characters.
  • Each expression after the initial one can match alphanumeric characters only (i.e., becoming part of the base token) or non-alphanumeric characters only (i.e., marking the end of the base token).

  Example - US phone number:

  • Incorrect Usage: \d{3}-?\d{3}-?\d{4} - Second expression is optional.
  • Correct Usage: Use multiple values.
    • \d{10} - Ten numeric characters, no delimiter.
    • \d{3}-\d{3}-\d{4} - Delimited with ‘-’.
  • The entire regex value can match just the base token.

  Example - California driver’s license number:

  • Correct Usage: [A-Za-z]\d{7} - Alphabetic characters followed by 7 numeric characters.
  • Regex values only match at the beginning of a token, i.e., at the first alphabetic or numeric character after a non-alphabetic, non-numeric character.

  Example - California driver’s license number:

  • [A-Za-z]\d{7} - Alphanumeric characters followed by seven numeric characters.
    • Matches: "A1234567", "-B7654321-"
    • Doesn’t Match: "AA1234567"

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