# 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](https://www.certificate-transparency.org/) 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](https://lanrat.com/certgraph/)
## Usage
```console
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
-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](https://search.censys.io/certificates). 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](https://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](https://transparencyreport.google.com/https/certificates)
## Example
```console
$ ./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](https://github.com/lanrat/certgraph/releases)
Pre-compiled releases will occasionally be uploaded to the [releases github page](https://github.com/lanrat/certgraph/releases). [https://github.com/lanrat/certgraph/releases](https://github.com/lanrat/certgraph/releases)
### [Docker](https://hub.docker.com/r/lanrat/certgraph/)
CertGraph is an automated build on the Docker Hub!
```console
$ 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
* [BlackArch](https://blackarch.org)
* [Kali Linux](https://www.kali.org/)
## 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
```console
certgraph$ make
go build -o certgraph certgraph.go
```
Alternatively you can use `go get` to install with this one-liner:
```console
go get -u github.com/lanrat/certgraph
```
## [Web UI](https://lanrat.github.io/certgraph/)
A web UI is provided in the docs folder and is accessible at the github pages url [https://lanrat.github.io/certgraph/](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](https://lanrat.github.io/certgraph/?data=https://gist.githubusercontent.com/lanrat/8187d01793bf3e578d76495182654206/raw/c49741b5206d81935febdf563452cc4346381e52/eff.json)
[](https://lanrat.github.io/certgraph/?data=https://gist.githubusercontent.com/lanrat/8187d01793bf3e578d76495182654206/raw/c49741b5206d81935febdf563452cc4346381e52/eff.json)
### [Example 2: google.com](https://lanrat.github.io/certgraph/?data=https://gist.githubusercontent.com/lanrat/1ab1e78aaf5798049650d8d8ad7b58a1/raw/426d3a2498626014cb5ba2856ad0899787e4103f/google.json)
[](https://lanrat.github.io/certgraph/?data=https://gist.githubusercontent.com/lanrat/1ab1e78aaf5798049650d8d8ad7b58a1/raw/426d3a2498626014cb5ba2856ad0899787e4103f/google.json)
### [Example 3: whitehouse.gov](https://lanrat.github.io/certgraph/?data=https://gist.githubusercontent.com/lanrat/96c47dfee0faaaad633cc830b7e3b997/raw/3c79fed837cb3202e220de21d2a8eb128f4bbd9f/whitehouse.json)
[](https://lanrat.github.io/certgraph/?data=https://gist.githubusercontent.com/lanrat/96c47dfee0faaaad633cc830b7e3b997/raw/3c79fed837cb3202e220de21d2a8eb128f4bbd9f/whitehouse.json)
## BygoneSSL detection
### Self Detection
CertGraph can be used to detect [BygoneSSL](https://insecure.design) 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.
```console
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
```console
certgraph -cdn -dns -apex [DOMAIN]...
```
And domains that print `* Missing DNS for` have vulnerable certificates that should be rotated.