Support to access specific index from the array element

[forgedhallpass]

Note: confirm if accessing a specific index from the array element is possible. if yes, update the docs, if not we can look into adding support for it.

---

• Update existing templates
• Update the documentation

id: testextractors

info:
  name: test extractors
  author: brenocss
  severity: info

requests:
  - method: GET
    path:
      - "{{BaseURL}}"

    extractors:
      - type: regex
        name: multiple
        regex:
          - 'script src="(.*?)">'
        internal: true

      - type: regex
        name: single
        regex:
          - 'UA-49905813-1'
        internal: true

    matchers:
      - type: dsl
        dsl:
          - "print_debug(multiple)"
          - "print_debug(multiple0)"
          - "contains(multiple, 'test')"
        condition: and

• Unable to use DSL functions on extractor that returns an array (multiple results) #1763
• Workflow extractor values in sub templates - indexed? #3766

[Mzack9999]

I don't this is possible without implementing a custom parser, since https://github.com/Knetic/govaluate does not support index access syntax. We could eventually add an helper function like array_pick(multiple, 1) or continue #914

[forgedhallpass]

Since we have _1 etc suffixes, I assume we are already doing manual parsing. Worst case, changing that to regular array access syntax should not be complicated. It's more straight forward for the users and maybe we'll change the underlying library later on to something that supports more complex evaluations out of the box.

[Mzack9999]

govaluate uses [] for escaping purposes, a few alternatives supporting array/slice accessors with brackets:

• https://github.com/d5/tengo
• https://github.com/projectdiscovery/nebula

[Esonhugh]

May my contribution is help to fix this issue.. ?
It's HelperFunction called index and I updated the len function to support getting len of array slice and even map.
index(stringOrSlice any, index int) string

PR reference: projectdiscovery/dsl#50
And it merged
Docs reference: projectdiscovery/nuclei-docs#155
And it merged as well
Now it's available on official website and nuclei binary.

[ehsandeep]

@Esonhugh index function doesn't work for items in the array like the example shared in the issue template, or let me know if you have an example to share?

[Esonhugh]

@Esonhugh index function doesn't work for items in the array like the example shared in the issue template, or let me know if you have an example to share?

Such kind of template in question may need more support. Such as supporting the array for regex multi results.

But it helps solving the condition in #2106 (comment).

index() can get the index of strings slice (more common type of a string array).

refer: https://github.com/projectdiscovery/dsl/blob/156ef2a49eb95f2f9c5757f161c21033a2221a61/dsl.go#L98 :type assert

doc: https://nuclei.projectdiscovery.io/templating-guide/helper-functions/

And I enhanced the len() func to help people to get the whole length of strings slice or other type make something like getting last 2 line in []line possible.