PCAPs or it didn't happen

In the wake of the recently disclosed vulnerability in OpenSSL v3.0 through v3.0.6 (CVE-2022-3602), we have looked into how an exploitation attempt appears 'on the wire'. This repository contains PCAPs of various exploitation scenarios, as well as detection rules for Suricata.

Also included is a PCAP containing the exchange of a legitimate certificate with a punycode-encoded e-mail address in the subject alternative name. We used this pcap to test whether rules do not trigger false positive on certificates that only have a short subject alternative name, instead of a very long one that we would expect in an exploitation attempt.

We have used the following resources to create PCAP files containing traffic that triggers the OpenSSL CVE-2022-3602 bug:

• https://github.com/DataDog/security-labs-pocs
• https://github.com/colmmacc/CVE-2022-3602

The following Suricata signatures was written to detect the OpenSSL CVE-2022-3602 bug:

alert tls any any -> any any (msg:"FOX-SRT - Exploit - Possible SpookySSL Certificate Observed (CVE-2022-3602)"; \
    flow:established; \
    content:"|2b 06 01 05 05 07 08 09|"; fast_pattern; \
    content:"|06 03 55 1d 1e|"; content:"xn--"; \
    content:!"|81|"; distance:-6; within:1; byte_test:2,>=,500,-6,relative; \
    classtype:attempted-user; threshold:type limit,track by_src,count 1,seconds 3600; \
    reference:url,www.openssl.org/news/secadv/20221101.txt; \
    reference:url,https://github.com/fox-it/spookyssl-pcaps; \
    metadata:ids suricata; \
    metadata:created_at 2022-11-02; sid:21004268; rev:3;)

To break down the content matches:

• |2b 06 01 05 05 07 08 09| -- Detects the type-id: 1.3.6.1.5.5.7.8.9 (id-pkix.8.9) (id-on-SmtpUTF8Mailbox)
• |06 03 55 1d 1e| -- Detects Extension Id: 2.5.29.30 (id-ce-nameConstraints) (nameConstraints extension)
• "xn--" -- Detects punycode, in combination with size of the punycode value using a byte_test keyword:
  • byte_test:2,>=,500,-6,relative;

We also explicitly check for small punycode values, in that case the signature should not trigger using:

• content:!"|81|"; distance:-6; within:1;

The network signatures will not work for sessions using TLSv1.3 as the Certificates are then encrypted.

You can also see a reset packet in the spookyssl-windowscrash.pcap due to the client crashing.