Kali Linux

xnLinkFinder : A Python Tool Used To Discover Endpoints And Potential Parameters

xnLinkFinder is a tool used to discover endpoints (and potential parameters) for a given target. It can find them by:

crawling a target (pass a domain/URL)
crawling multiple targets (pass a file of domains/URLs)
searching files in a given directory (pass a directory name)
get them from a Burp project (pass location of a Burp XML file)
get them from an OWASP ZAP project (pass location of a ZAP ASCII message file)
processing a waymore results directory (searching archived response files from waymore -mode R and also requesting URLs from waymore.txt and the original URLs from index.txt – see waymore README.md)

The python script is based on the link finding capabilities of my Burp extension GAP. As a starting point, I took the amazing tool LinkFinder by Gerben Javado, and used the Regex for finding links, but with additional improvements to find even more.

Installation

xnLinkFinder supports Python 3.

$ git clone https://github.com/xnl-h4ck3r/xnLinkFinder.git
$ cd xnLinkFinder
$ sudo python setup.py install

Usage

Arg	Long Arg	Description
-i	–input	Input a: URL, text file of URLs, a Directory of files to search, a Burp XML output file or an OWASP ZAP output file.
-o	–output	The file to save the Links output to, including path if necessary (default: output.txt). If set to `cli` then output is only written to STDOUT. If the file already exist it will just be appended to (and de-duplicated) unless option `-ow` is passed.
-op	–output-params	The file to save the Potential Parameters output to, including path if necessary (default: parameters.txt). If set to `cli` then output is only written to STDOUT (but not piped to another program). If the file already exist it will just be appended to (and de-duplicated) unless option `-ow` is passed.
-ow	–output-overwrite	If the output file already exists, it will be overwritten instead of being appended to.
-sp	–scope-prefix	Any links found starting with `/` will be prefixed with scope domains in the output instead of the original link. If the passed value is a valid file name, that file will be used, otherwise the string literal will be used.
-spo	–scope-prefix-original	If argument `-sp` is passed, then this determines whether the original link starting with `/` is also included in the output (default: false)
-sf	–scope-filter	Will filter output links to only include them if the domain of the link is in the scope specified. If the passed value is a valid file name, that file will be used, otherwise the string literal will be used.
-c	–cookies †	Add cookies to pass with HTTP requests. Pass in the format `'name1=value1; name2=value2;'`
-H	–headers †	Add custom headers to pass with HTTP requests. Pass in the format `'Header1: value1; Header2: value2;'`
-ra	–regex-after	RegEx for filtering purposes against found endpoints before output (e.g. `/api/v[0-9]\.[0-9]\*` ). If it matches, the link is output.
-d	–depth †	The level of depth to search. For example, if a value of 2 is passed, then all links initially found will then be searched for more links (default: 1). This option is ignored for Burp files because they can be huge and consume lots of memory. It is also advisable to use the `-sp` (`--scope-prefix`) argument to ensure a request to links found without a domain can be attempted.
-p	–processes †	Basic multithreading is done when getting requests for a URL, or file of URLs (not a Burp file). This argument determines the number of processes (threads) used (default: 25)
-x	–exclude	Additional Link exclusions (to the list in `config.yml`) in a comma separated list, e.g. `careers,forum`
-orig	–origin	Whether you want the origin of the link to be in the output. Displayed as `LINK-URL [ORIGIN-URL]` in the output (default: false)
-t	–timeout †	How many seconds to wait for the server to send data before giving up (default: 10 seconds)
-inc	–include	Include input (`-i`) links in the output (default: false)
-u	–user-agent †	What User Agents to get links for, e.g. `-u desktop mobile`
-insecure	†	Whether TLS certificate checks should be disabled when making requests (delfault: false)
-s429	†	Stop when > 95 percent of responses return 429 Too Many Requests (default: false)
-s403	†	Stop when > 95 percent of responses return 403 Forbidden (default: false)
-sTO	†	Stop when > 95 percent of requests time out (default: false)
-sCE	†	Stop when > 95 percent of requests have connection errors (default: false)
-m	–memory-threshold	The memory threshold percentage. If the machines memory goes above the threshold, the program will be stopped and ended gracefully before running out of memory (default: 95)
-mfs	–max-file-size †	The maximum file size (in bytes) of a file to be checked if -i is a directory. If the file size os over, it will be ignored (default: 500 MB). Setting to 0 means no files will be ignored, regardless of size..
-replay-proxy	†	For active link finding with URL (or file of URLs), replay the requests through this proxy.
-ascii-only		Whether links and parameters will only be added if they only contain ASCII characters. This can be useful when you know the target is likely to use ASCII characters and you also get a number of false positives from binary files for some reason.
-v	–verbose	Verbose output
-vv	–vverbose	Increased verbose output
	–version	Show current version number.
-h	–help	show the help message and exit

† NOT RELEVANT FOR INPUT OF DIRECTORY, BURP XML FILE OR OWASP ZAP FILE

config.yml

The config.yml file has the keys which can be updated to suit your needs:

linkExclude – A comma separated list of strings (e.g. .css,.jpg,.jpeg etc.) that all links are checked against. If a link includes any of the strings then it will be excluded from the output. If the input is a directory, then file names are checked against this list.
contentExclude – A comma separated list of strings (e.g. text/css,image/jpeg,image/jpg etc.) that all responses Content-Type headers are checked against. Any responses with the these content types will be excluded and not checked for links.
fileExtExclude – A comma separated list of strings (e.g. .zip,.gz,.tar etc.) that all files in Directory mode are checked against. If a file has one of those extensions it will not be searched for links.
regexFiles – A list of file types separated by a pipe character (e.g. php|php3|php5 etc.). These are used in the Link Finding Regex when there are findings that aren’t obvious links, but are interesting file types that you want to pick out. If you add to this list, ensure you escape any dots to ensure correct regex, e.g. js\.map
respParamLinksFound † – Whether to get potential parameters from links found in responses: True or False
respParamPathWords † – Whether to add path words in retrieved links as potential parameters: True or False
respParamJSON † – If the MIME type of the response contains JSON, whether to add JSON Key values as potential parameters: True or False
respParamJSVars † – Whether javascript variables set with var, let or const are added as potential parameters: True or False
respParamXML † – If the MIME type of the response contains XML, whether to add XML attributes values as potential parameters: True or False
respParamInputField † – If the MIME type of the response contains HTML, whether to add NAME and ID attributes of any INPUT fields as potential parameters: True or False
respParamMetaName † – If the MIME type of the response contains HTML, whether to add NAME attributes of any META tags as potential parameters: True or False

† IF THESE ARE NOT FOUND IN THE CONFIG FILE THEY WILL DEFAULT TO True

Examples

Find Links from a specific target – Basic

python3 xnLinkFinder.py -i target.com

Find Links from a specific target – Detailed

Ideally, provide scope prefix (-sp) with the primary domain (including schema), and a scope filter (-sf) to filter the results only to relevant domains (this can be a file or in scope domains). Also, you can pass cookies and customer headers to ensure you find links only available to authorised users. Specifying the User Agent (-u desktop mobile) will first search for all links using desktop User Agents, and then try again using mobile user agents. There could be specific endpoints that are related to the user agent given. Giving a depth value (-d) will keep sending request to links found on the previous depth search to find more links.

python3 xnLinkFinder.py -i target.com -sp target_prefix.txt -sf target_scope.txt -spo -inc -vv -H 'Authorization: Bearer XXXXXXXXXXXXXX' -c 'SessionId=MYSESSIONID' -u desktop mobile -d 10

Find Links from a list of URLs – Basic

If you have a file of JS file URLs for example, you can look for links in those:

python3 xnLinkFinder.py -i target_js.txt

Find Links from a files in a directory – Basic

If you have a files, e.g. JS files, HTTP responses, etc. you can look for links in those:

python3 xnLinkFinder.py -i ~/Tools/waymore/results/target.com

NOTE: Sub directories are also checked. The -mfs option can be specified to skip files over a certain size.

Find Links from a Burp project – Basic

In Burp, select the items you want to search by highlighting the scope for example, right clicking and selecting the Save selected items. Ensure that the option base64-encode requests and responses option is checked before saving. To get all links from the file (even with HUGE files, you’ll be able to get all the links):

python3 xnLinkFinder.py -i target_burp.xml

NOTE: xnLinkFinder makes the assumption that if the first line of the file passed with -i starts with <?xml then you are trying to process a Burp file.

Find Links from a Burp project – Detailed

Ideally, provide scope prefix (-sp) with the primary domain (including schema), and a scope filter (-sf) to filter the results only to relevant domains.

python3 xnLinkFinder.py -i target_burp.xml -o target_burp.txt -sp https://www.target.com -sf target.* -ow -spo -inc -vv

Find Links from an OWASP ZAP project – Basic

In ZAP, select the items you want to search by highlighting the History for example, clicking menu Report and selecting Export Messages to File.... This will let you save an ASCII text file of all requests and responses you want to search. To get all links from the file (even with HUGE files, you’ll be able to get all the links):

python3 xnLinkFinder.py -i target_zap.txt

NOTE: xnLinkFinder makes the assumption that if the first line of the file passed with -i is in the format ==== 99 ========== for example, then you are trying to process an OWASP ZAP ASCII text file.

Find Links from a Waymore results directory

The waymore tool can be used to get URLs from various third party APIs, and also download archived responses from archive.org (Wayback Machine). Passing a waymore results directory to xnLinKFinder will search the contents of archived responses, and also request URLs from waymore.txt and also the archived URLs from index.txt and get more links from those responses.

python3 xnLinkFinder.py -i ~/Tools/waymore/results/target.com

NOTE: It is passed as a normal directory, but xnLinkFinder will determine it is a waymore results directory and process respectively.

Piping to other Tools

You can pipe xnLinkFinder to other tools. Any errors are sent to stderr and any links found are sent to stdout. The output file is still created in addition to the links being piped to the next program. However, potential parameters are not piped to the next program, but they are still written to file. For example:

python3 xnLinkFinder.py -i redbull.com -sp https://redbull.com -sf rebbull.* -d 3 | unfurl keys | sort -u

You can also pass the input through stdin instead of -i.

cat redbull_subs.txt | python3 xnLinkFinder.py -sp https://redbull.com -sf rebbull.* -d 3

NOTE: You can’t pipe in a Burp or ZAP file, these must be passed using -i.

Recommendations and Notes

Always use the Scope Prefix argument -sp. This can be one scope domain, or a file containing multiple scope domains. Below are examples of the format used (no path should be included, and no wildcards used. Schema is optional, but will default to http): http://www.target.com https://target-payments.com https://static.target-cdn.com If a link is found that has no domain, e.g. /path/to/example.js then giving passing -sp http://www.target.com will result in teh output http://www.target.com/path/to/example.js and if Depth (-d) is >1 then a request will be able to be made to that URL to search for more links. If a file of domains are passed using -sp then the output will include each domain followed by /path/to/example.js and increase the chance of finding more links.
If you use -sp but still want the original link of /path/to/example.js (without a domain) additionally returned in the output, the pass the argument -spo.
Always use the Scope Filter argument -sf. This will ensure that only relevant domains are returned in the output, and more importantly if Depth (-d) is >1 then out of scope targets will not be searched for links or parameters. This can be one scope domain, or a file containing multiple scope domains. Below are examples of the format used (no schema or path should be included): target.* target-payments.com static.target-cdn.com THIS IS FOR FILTERING THE LINKS DOMAIN ONLY.
If you want to filter the final output in any way, use -ra. It’s always a good idea to use https://regex101.com/ to check your Regex expression is going to do what you expect.
Use the -v option to have a better idea of what the tool is doing.
If you have problems, use the -vv option which may show errors that are occurring, which can possibly be resolved, or you can raise as an issue on github.
Pass cookies (-c), headers (-H) and regex (-ra) values within single quotes, e.g. -ra '/api/v[0-9]\.[0-9]\*'
Set the -o option to give a specific output file name for Links, rather than the default of output.txt. If you plan on running a large depth of searches, start with 2 with option -v to check what is being returned. Then you can increase the Depth, and the new output will be appended to the existing file, unless you pass -ow.
Set the -op option to give a specific output file name for Potential Parameters, rather than the default of parameters.txt. Any output will be appended to the existing file, unless you pass -ow.
If using a high Depth (-d) be wary of some sites using dynamic links so will it will just keep finding new ones. If no new links are being found, then xnlLinkFinder will stop searching. Providing the Stop flags (s429, s403, sTO, sCE) should also be considered.
If you are finding a large number of links (especially if the Depth (-d value is high), and have limited resources, the program will stop when it reaches the memory Threshold (-m) value and end gracefully with data intact before getting killed.
If you decide to cancel xnLinkFinder (using Ctrl-C) in the middle of running, be patient and any gathered data will be saved before ending gracefully.
Using the -orig option will show the URL where the link was found. This can mean you have duplicate links in the output if the same link was found on multiple sources, but it will suffixed with the origin URL in square brackets.
When making requests, xnLinkFinder will use a random User-Agent from the current group, which defaults to desktop. If you have a target that could have different links for different user agent groups, the specify -u desktop mobile for example (separate with a space). The mobile user agent option is an combination of mobile-apple, mobile-android and mobile-windows.
When -i has been set to a directory, the contents of the files in the root of that directory will be searched for links. Files in sub-directories are not searched. Any files that are over the size set by -mfs (default: 500 MB) will be skipped.
When using the -replay-proxy option, sometimes requests can take longer. If you start seeing more Request Timeout errors (you’ll see errors if you use -v or -vv options) then consider using -t to raise the timeout limit.
If you know a target will only have ASCII characters in links and parameters then consider passing -ascii-only. This can eliminate a number of false positives that can sometimes get returned from binary data.
If you pass a waymore results directory, it is worth passing the -d/--depth argument to search any extra links found from URL requests and also the -u/--user-agent if you think there could be different content found, e.g. -u desktop mobile.

Issues

If you come across any problems at all, or have ideas for improvements, please feel free to raise an issue on Github. If there is a problem, it will be useful if you can provide the exact command you ran and a detailed description of the problem. If possible, run with -vv to reproduce the problem and let me know about any error messages that are given.