CVE-2008-0166 的 16 年 - Debian OpenSSL 漏洞

DKIM and Debian OpenSSL bug: DKIM allows signing emails with a DNS TXT record key. Many hosts are vulnerable to the 2008 Debian OpenSSL bug through badkeys scan, including notable names.
- Vulnerable keys count: Out of 355,055 TXT records with valid RSA keys (only 2 Ed25519 keys), 855 were vulnerable (around 0.24%), with 777 having identical keys and 22 unique vulnerable keys. 21 additional vulnerable keys found through other methods.
- Most keys from one company: 777 identical keys were mostly configured as a CNAME to a host of Cakemail. Tried to disclose to Cakemail but got no response.
- Reason for using old keys: DKIM has no key rotation requirement. Companies configured DKIM TXT records in 2007 and didn't change them.
BIMI: A moneymaking scheme by certificate authorities. Allows publishing a logo in SVG format in emails. Gmail shows some logos. There is no cryptographic connection between the certificate and DKIM key.
- Example with entrust.com: Has a vulnerable 1024-bit RSA DKIM key and a BIMI default record. Can sign emails with dkimsign and show a BIMI logo. Entrust is one of two companies selling BIMI certificates.
- Security problems: The specification has obvious design flaws with unclear explanations.
Security advice: Email providers and developers should not implement BIMI. Mail servers can implement BIMI troll mode by inserting a "say no to BIMI" logo.
Tool for checking: The latest version of badkeys can scan DKIM keys directly. It can be installed via pip and has parameters like --dkim and --dkim-dns.
Personal note: Published the page on May 12th (one day early as the Debian OpenSSL bug was announced on May 13th, 2008). Offers help with email security and other topics on related websites.