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CertGraph

A tool to crawl the graph of certificate Alternate Names

CertGraph crawls SSL certificates creating a directed graph where each domain is a node and the certificate alternative names for that domain's certificate are the edges to other domain nodes. New domains are printed as they are found. In Detailed mode upon completion the Graph's adjacency list is printed.

Crawling defaults to collecting certificate by connecting over TCP, however there are multiple drivers that can search Certificate Transparency logs.

This tool was designed to be used for host name enumeration via SSL certificates, but it can also show you a "chain" of trust between domains and the certificates that re-used between them.

Blog post with more information

Usage

Usage of ./certgraph: [OPTION]... HOST...
        https://github.com/lanrat/certgraph
OPTIONS:
  -apex
     for every domain found, add the apex domain of the domain's parent
  -cdn
     include certificates from CDNs
  -censys-appid string
     censys API AppID
  -censys-secret string
     censys API Secret
  -ct-expired
     include expired certificates in certificate transparency search
  -ct-subdomains
     include sub-domains in certificate transparency search
  -depth uint
     maximum BFS depth to go (default 5)
  -details
     print details about the domains crawled
  -dns
     check for DNS records to determine if domain is registered
  -driver string
     driver(s) to use [censys, crtsh, google, http, smtp] (default "http")
  -json
     print the graph as json, can be used for graph in web UI
  -parallel uint
     number of certificates to retrieve in parallel (default 10)
  -regex string
     regex domains must match to be part of the graph
  -sanscap int
     maximum number of uniq apex domains in certificate to include, 0 has no limit (default 80)
  -save string
     save certs to folder in PEM format
  -serve string
     address:port to serve html UI on
  -timeout uint
     tcp timeout in seconds (default 10)
  -updatepsl
     Update the default Public Suffix List
  -verbose
     verbose logging
  -version
     print version and exit

Drivers

CertGraph has multiple options for querying SSL certificates. The driver is responsible for retrieving the certificates for a given domain. Currently there are the following drivers:

http this is the default driver which works by connecting to the hosts over HTTPS and retrieving the certificates from the SSL connection
smtp like the http driver, but connects over port 25 and issues the starttls command to retrieve the certificates from the SSL connection
censys this driver searches Certificate Transparency logs via censys.io. No packets are sent to any of the domains when using this driver. Requires Censys API keys
crtsh this driver searches Certificate Transparency logs via crt.sh. No packets are sent to any of the domains when using this driver
google this is another Certificate Transparency driver that behaves like crtsh but uses the Google Certificate Transparency Lookup Tool

Example

$ ./certgraph -details eff.org
eff.org 0       Good    42E3E4605D8BB4608EB64936E2176A98B97EBF2E0F8F93A64A6640713C7D4325
maps.eff.org    1       Good    42E3E4605D8BB4608EB64936E2176A98B97EBF2E0F8F93A64A6640713C7D4325
https-everywhere-atlas.eff.org  1       Good    42E3E4605D8BB4608EB64936E2176A98B97EBF2E0F8F93A64A6640713C7D4325
httpse-atlas.eff.org    1       Good    42E3E4605D8BB4608EB64936E2176A98B97EBF2E0F8F93A64A6640713C7D4325
atlas.eff.org   1       Good    42E3E4605D8BB4608EB64936E2176A98B97EBF2E0F8F93A64A6640713C7D4325
kittens.eff.org 1       Good    42E3E4605D8BB4608EB64936E2176A98B97EBF2E0F8F93A64A6640713C7D4325

The above output represents the adjacency list for the graph for the root domain eff.org. The adjacency list is in the form: Node Depth Status Cert-Fingerprint

Releases

Pre-compiled releases will occasionally be uploaded to the releases github page. https://github.com/lanrat/certgraph/releases

Docker

CertGraph is an automated build on the Docker Hub!

$ docker run --rm -it lanrat/certgraph example.com
example.com
www.example.net
www.example.org
www.example.com
example.org
example.net
example.edu
www.example.edu

Linux Distributions

Compiling

To compile certgraph you must have a working go 1.16 or newer compiler on your system. To compile for the running system compilation is as easy as running make

certgraph$ make
go build -o certgraph certgraph.go

Alternatively you can use go get to install with this one-liner:

go install github.com/lanrat/certgraph@latest

Web UI

A web UI is provided in the docs folder and is accessible at the github pages url https://lanrat.github.io/certgraph/, or can be run from the embedded web server by calling certgraph --serve 127.0.0.1:8080.

The web UI takes the output provided with the -json flag. The JSON graph can be sent to the web interface as an uploaded file, remote URL, or as the query string using the data variable.

Example 1: eff.org

Example 2: google.com

Example 3: whitehouse.gov

BygoneSSL detection

Self Detection

CertGraph can be used to detect BygoneSSL DoS with the following options. CT-DRIVER can be any Certificate Transparency capable driver. Provide all known input domains you own. If any domains you do not own are printed, then you are vulnerable.

certgraph -depth 1 -driver CT-DRIVER -ct-subdomains -cdn -apex [DOMAIN]...

Bug Bounty

If you want to find a vulnerable site that has a bug bounty, certgraph can be used with the following options and any driver. But you will have better luck with a non Certificate Transparency driver to ensure that the certificates in question are actually in use

certgraph -cdn -dns -apex [DOMAIN]...

And domains that print * Missing DNS for have vulnerable certificates that should be rotated.