A program to scan TLS based servers and collect X.509 certificates, ciphers and related information. It produces results in JSON format. tls-scan is a single threaded asynchronous/event-based program (powered by libevent) capable of concurrently scan thousands of TLS servers. It can be combined with other tools such as GNU parallel to vertically scale in multi-core machines.

tls-scan helps developers and security engineers to track/test/debug certificates and TLS configurations of servers within their organization.

• Support for TLSv1.3
• TLS and StartTLS protocol support: SMTP, IMAP, POP3, FTPS, SIEVE, NNTP, XMPP, LDAP, RDP, POSTGRES, MYSQL
• Blazing fast - Can operate at scale with the ability to concurrently scan large number of servers (say scan IoT devices at scale)
• Detect SSLv2, SSLv3, TLSv1, TLSv1.1, TLSv1.2, TLSv1.3 versions and ciphers
• ALPN protocol id enumeration
• Cipher and TLS version enumeration
• Extract X.509 certificate fields from the target server and print it in JSON format
• Certificate and host name verification checks
• TLS compression checks
• Session reuse tests
• Certificate revocation checks with stapled OCSP response
• Script friendly output - Can be combined with other tools to analyze the scan results
• Detailed run time stats for tracking progress and performance/charts

This tool is primarily for collecting TLS cipher and X.509 certificate data. The scan output can be easily combined with related tools to identify TLS misconfigurations.

You may either use pre-built binary package or build from the source.

Linux and OSX: https://github.com/prbinu/tls-scan/releases/latest

All you need is build-x86-64.sh (or build-arm64.sh for Linux Arm arch). This script pulls dependent packages - PeterMosmans openssl, libevent and GnuTLS, and build those from the scratch. Since the openssl we use is different from stock openssl, it is linked statically to tls-scan program. The build can take approximately twenty minutes to complete.

Build Pre-requisites :

• autoconf
• automake
• libtool
• pkg-config
• gcc
• make

On Ubuntu:

sudo apt-get update
sudo apt-get install make autoconf automake libtool pkg-config gcc unzip -y

git clone https://github.com/prbinu/tls-scan.git
cd tls-scan

x84_64

./build-x86-64.sh

The newly built tls-scan binary can be found at ./build-root/bin. build-x86-64.sh is a wrapper script that calls ./bootstrap.sh to build all dependent packages. bootstrap.sh also executes the autoreconf -i command to generate configure file. Subsequently it calles the standard ./configure, make && make install.

arm64

./build-arm64.sh

Test :

cd build-root/bin
./tls-scan --connect=yahoo.com --cacert=../etc/tls-scan/ca-bundle.crt --pretty

If you do not have the pre-requisite packages, you can easily install those packages by following the links below:

• xcode-command-line-tools
• how-to-install-autoconf-automake-and-related-tools-on-mac-os-x-from-source

git clone https://github.com/prbinu/tls-scan.git
cd tls-scan
./build-x86-64.sh

The tls-scan binary can be found at ./build-root/bin. Another (easy) option is to use our Docker image to build and run tls-scan on OSX.

Running tls-scan on Mac Apple Silicon (Arm/M1/M2):

Currently no native build support, however you may run tls-scan binary using Rosetta2

Pre-requisite : Docker

Build : Copy the Dockerfile to your machine, and run it:

docker build -t tls-scan .

Test :

docker run --rm tls-scan --connect=example.com:443 --all --pretty

./tls-scan -c search.yahoo.com --all --pretty

{
  "host": "search.yahoo.com",
  "ip": "208.71.45.12",
  "port": 443,
  "elapsedTime": 1600,
  "tlsVersion": "TLSv1.2",
  "cipher": "ECDHE-RSA-AES128-GCM-SHA256 TLSv1.2 Kx=ECDH     Au=RSA  Enc=AESGCM(128) Mac=AEAD",
  "tempPublicKeyAlg": "ECDH prime256v1",
  "tempPublicKeySize": 256,
  "secureRenego": true,
  "compression": "NONE",
  "expansion": "NONE",
  "sessionLifetimeHint": 100800,
  "tlsVersions": [
    "TLSv1",
    "TLSv1_1",
    "TLSv1_2"
  ],
  "x509ChainDepth": 2,
  "verifyCertResult": true,
  "verifyHostResult": true,
  "ocspStapled": true,
  "verifyOcspResult": true,
  "certificateChain": [
  {
    "version": 3,
    "subject": "CN=*.search.yahoo.com; O=Yahoo! Inc.; L=Sunnyvale; ST=CA; C=US",
    "issuer": "CN=DigiCert SHA2 High Assurance Server CA; OU=www.digicert.com; O=DigiCert Inc; C=US",
    "subjectCN": "*.search.yahoo.com",
    "subjectAltName": "DNS:*.search.yahoo.com, DNS:search.yahoo.com, DNS:search.yahoo.net, ...",
    "signatureAlg": "sha256WithRSAEncryption",
    "notBefore": "Dec  9 00:00:00 2016 GMT",
    "notAfter": "Apr 30 12:00:00 2017 GMT",
    "expired": false,
    "serialNo": "0F:45:73:E3:F5:7A:7D:5B:43:57:64:2A:6C:46:F2:1C",
    "keyUsage": "Digital Signature, Key Encipherment critical",
    "extKeyUsage": "TLS Web Server Authentication, TLS Web Client Authentication",
    "publicKeyAlg": "RSA",
    "publicKeySize": 2048,
    "basicConstraints": "CA:FALSE critical",
    "subjectKeyIdentifier": "63:0F:82:DB:F9:B0:64:78:90:C9:16:69:95:84:24:F1:4B:04:6F:E4",
    "sha1Fingerprint": "F7:35:E5:C9:A3:60:62:07:CB:55:74:7E:0F:09:AD:2A:F3:F3:53:F3"
  },  {
    "version": 3,
    "subject": "CN=DigiCert SHA2 High Assurance Server CA; OU=www.digicert.com; O=DigiCert Inc; C=US",
    "issuer": "CN=DigiCert High Assurance EV Root CA; OU=www.digicert.com; O=DigiCert Inc; C=US",
    "subjectCN": "DigiCert SHA2 High Assurance Server CA",
    "signatureAlg": "sha256WithRSAEncryption",
    "notBefore": "Oct 22 12:00:00 2013 GMT",
    "notAfter": "Oct 22 12:00:00 2028 GMT",
    "expired": false,
    "serialNo": "04:E1:E7:A4:DC:5C:F2:F3:6D:C0:2B:42:B8:5D:15:9F",
    "keyUsage": "Digital Signature, Certificate Sign, CRL Sign critical",
    "extKeyUsage": "TLS Web Server Authentication, TLS Web Client Authentication",
    "publicKeyAlg": "RSA",
    "publicKeySize": 2048,
    "basicConstraints": "CA:TRUE, pathlen:0 critical",
    "subjectKeyIdentifier": "51:68:FF:90:AF:02:07:75:3C:CC:D9:65:64:62:A2:12:B8:59:72:3B",
    "sha1Fingerprint": "A0:31:C4:67:82:E6:E6:C6:62:C2:C8:7C:76:DA:9A:A6:2C:CA:BD:8E"
  } ]
}

The scan output can be shoved into tools like Splunk or ELK for analysis.

By passing tls-scan output to JSON command-line parser like jq, you can do realtime filtering on the scan results.

Examples:

Command to filter out hosts that passed certificate and host name verifications:

cat input.txt | tls-scan --port=443  2>/dev/null | \
jq-linux64 -r 'select(.verifyHostResult == true and .verifyCertResult == true) | [.host, .ip, .verifyHost, .verifyCert] | @tsv'

Command to find hosts with expired certificates :

cat input.txt | tls-scan --port=443 --concurrency=500 --timeout=5 2>/dev/null | \
jq-linux64 -r  'select(.certificateChain[].expired == true) | [.host, .ip] | @tsv'

Command to find weak RSA keys :

cat tlscerts.out | \
jq-linux64 -r  'select(.certificateChain[0].publicKeyAlg == "RSA" and .certificateChain[0].publicKeySize < 2048) | [.host, .ip]'

Command to find hosts that support SSLv2 or SSLv3 :

tls-scan --infile=domains.txt --port=443 --version-enum --concurrency=250 --timeout=3 2>/dev/null | \
jq-linux64 -r 'if (.tlsVersions[] | contains("SSL")) == true then [.host, .ip, .tlsVersions[]] else empty end | @tsv'

NOTE: Avoid frequent scan + filter; instead save the scan output to a file and use it to run queries.

• The following ciphers are currently disabled: SRP:PSK

To support old, insecure cipher scans, we are using an old openssl version that doesn't have support for TLS 1.3. So to support TLS 1.3, we need a newer openssl version (v1.1.1+). Since linking two openssl libraries to the same process space doesn't work out of box (duplicate symbols), we chose to use GnuTLS library for TLS 1.3+ support. In short, openssl is used for scanning SSLv2, SSLv3, TLSv1, TLSv1.1 and TLSv1.2 and GnuTLS is used for TLSv1.3.

Collaborators and pull requests are welcome!