TLS-Scanner

TLS-Scanner is a tool to assist pentesters and security researchers in the evaluation of TLS server and client configurations.

Please note: TLS-Scanner is a research tool intended for TLS developers, pentesters, administrators and researchers. There is no GUI. It is in the first version and may contain some bugs.

Compiling

In order to compile and use TLS-Scanner, you need to run:

$ cd TLS-Scanner
$ git submodule update --init --recursive
$ mvn clean package

Alternatively, if you are in a hurry, you can skip the tests by using:

$ mvn clean package -DskipTests=true

If you want to use TLS-Scanner as a library you need to install it with the following command:

$ mvn clean install

Running

In order to run TLS-Scanner you need to run one of the jar files in the apps/ folder. These can be obtained by compiling the app yourself or by downloading released jar files from GitHub.

$ java -jar apps/TLS-Server-Scanner.jar -connect localhost:4433

TLS-Scanner will evaluate the specified server (here localhost on port 4433), and in the end print a report. The report uses colors to convey the severity of the findings:

• Green: A good result.
• Yellow: A warning, which may be a potential problem.
• Yellow Background: Results where the scanner is unsure whether the target is vulnerable.
• Red: A severe problem, which should be fixed.
• Default color (depending on your terminal, likely black or white): A neutral result, which is neither good nor bad. This includes informational results.
• Blue: The scanner could not scan the server for this specific test. This is likely due to a prerequisite for this test to not being supported.
• Purple: The scanner encountered an error while scanning the server for this specific test. This can be the result of a bug in the scanner, but also due to the server not supporting a required feature.
• Cyan: Used for structuring the report (headings, ...).

Important Parameters

You must specify a host you want to scan with the -connect parameter.

If you want to improve the performance of the scan, you can use the -threads parameter to increase the number of used threads.

Another important parameter for performance reasons is the -scanDetail parameter, which can be used to configure how detailed you want to scan. Possible values ranging from fast to very detailed are: QUICK, NORMAL, DETAILED, ALL.

The detail of the output can be configured with the -reportDetail parameter. In order to see more details about the Guidelines, use -reportDetail ALL.

By default, the results are written to the console only. If you want to have machine-readable output, you can use -outputFile output.json to automatically write the results in a JSON file.

Use Cases

The most important parameters to change are -scanDetail and -reportDetail. In the following, we explain some use cases for these parameters.

Default Scan

For most cases, our default parameter settings are sufficient. This performs a scan with both detail levels set to NORMAL.

Fast Scan

If you want to perform a fast scan and get a quick overview over your system, we recommend to use both detail levels set to QUICK. This limits the extend of some executed probes to lower the runtime and limits the report detail to not include very detailed and technical information.

Detailed Scan

If you want to fully evaluate your system and execute everything that we have, we recommend to use both detail levels set to ALL. This executes all existing probes fully and prints very detailed information for further analysis and evaluation.

Scan Profiles

Instead of (or in addition to) setting parameters like -scanDetail individually, you can bundle which probes to run and which of these parameters to use into a reusable JSON scan profile with the -profile <path/to/profile.json> parameter. It is available on both TlsServerScanner and TlsClientScanner.

A profile is a JSON file with:

• inheritedFromProfiles: paths to other profiles to combine probes from, resolved relative to the directory of the profile file declaring them (an absolute path is used as-is).
• probes: the probes to run, as a map from the fully qualified name of a ProbeType enum class to the list of its constant names to run. This groups probes by type instead of repeating the type for every single probe, while a single profile can still freely combine probes from different ProbeType implementations, e.g. TlsProbeType and QuicProbeType. Each per-type list also accepts "*" (all constants of that type) and "!CONSTANT_NAME" (remove a constant previously added by name or by "*"), processed in order — see Everything.json and demo.json in scan-profiles/ for examples.
• settings (optional): overrides for parameters like -scanDetail, -reportDetail, -postAnalysisDetail, -noColor, -outputFile, -probeTimeout, -parallelProbes, and -threads. Any field left out keeps its normal default (or whatever was passed on the command line). Unlike probes, settings are not inherited — only the settings declared directly on the profile you point -profile at apply, even if it inherits probes from other profiles.

Only the probes resolved from the active profile (and everything it inherits from) are executed; everything else is skipped.

Example, combining a base profile's probes with your own and tuning the scan detail:

base.json:

{
    "probes": {
        "de.rub.nds.tlsscanner.core.constants.TlsProbeType": ["PROTOCOL_VERSION", "CIPHER_SUITE"]
    }
}

quic.json (in the same directory as base.json):

{
    "inheritedFromProfiles": ["base.json"],
    "settings": {
        "scanDetail": "QUICK"
    },
    "probes": {
        "de.rub.nds.tlsscanner.core.constants.QuicProbeType": ["SUPPORTED_VERSIONS"]
    }
}

$ java -jar apps/TLS-Server-Scanner.jar -connect localhost:4433 -profile quic.json

This runs PROTOCOL_VERSION, CIPHER_SUITE, and SUPPORTED_VERSIONS with -scanDetail QUICK.

To see every probe available for a scanner (without connecting to a target), use -listProbes. It prints them grouped by ProbeType class in the exact JSON syntax a profile's probes field expects, so you can copy-paste it straight into a profile:

$ java -jar apps/TLS-Server-Scanner.jar -listProbes
{
  "de.rub.nds.tlsscanner.core.constants.TlsProbeType" : [ "ALPN", "ESNI", "CERTIFICATE", ... ],
  "de.rub.nds.tlsscanner.core.constants.QuicProbeType" : [ "SUPPORTED_VERSIONS", ... ]
}

All Parameters

To get detailed information about all possible parameters, use the -help parameter or execute the jar without any parameters set.

Docker

We provide prebuilt docker images for easy use of the TLS-Server-Scanner.

$ docker run -it --network host ghcr.io/tls-attacker/tlsscanner -connect localhost:4433

The image is made to be used for server-scanning but also contains the other jar files. They can be accessed by altering the entrypoint.

$ docker run -it --network host --entrypoint java ghcr.io/tls-attacker/tlsscanner -jar TLS-Client-Scanner.jar

We also provide you with a Dockerfile, to build the container yourself:

$ docker build . -t tlsscanner
$ docker run -t tlsscanner

Please note: I am by no means familiar with Docker best practices. If you know how to improve the Dockerfile feel free to issue a pull request

Requirement System