Source URL: https://blog.apnic.net/2021/11/18/vulnerabilities-show-why-starttls-should-be-avoided-if-possible/
Source: Hacker News
Title: Vulnerabilities show why STARTTLS should be avoided if possible
Feedly Summary: Comments
AI Summary and Description: Yes
Summary: The text discusses vulnerabilities associated with STARTTLS in email communications, highlighting both client-side and server-side flaws. It emphasizes the importance of transitioning to implicit TLS to counter these vulnerabilities and suggests best practices for email service operators. This research is particularly relevant for professionals in the security field who must manage risks associated with email protocols.
Detailed Description:
The text details a study on vulnerabilities related to the STARTTLS protocol used in email communications. Here are the major points:
– **STARTTLS Overview**: STARTTLS is an encryption method that upgrades an unencrypted connection to an encrypted one, commonly used with email protocols like SMTP, IMAP, and POP3.
– **Vulnerability Research**: Collaborative research revealed over 40 vulnerabilities in various software products involving STARTTLS, affecting both client-side and server-side implementations.
– **Opportunistic Security Risks**: The text describes how the opportunistic use of STARTTLS can lead to vulnerabilities, where a client may connect unencrypted if encrypted options are not available, exposing users to attacks.
– **Command Injection Flaw**: A specific vulnerability dating back to 2011 was reiterated, where plaintext commands can be injected into seemingly secure connections. Major email providers like GMX and Yandex were found susceptible to this vulnerability.
– #### Command Injection Example:
– The attacker can inject commands to authorize their email address and capture victim credentials through misinterpreted commands in a STARTTLS context.
– **Response Injection Vulnerabilities**: Similar vulnerabilities allow attackers to forge responses, manipulating mailbox content by exploiting response injection.
– **PREAUTH and STARTTLS Incompatibility**: A serious issue is outlined regarding the IMAP protocol’s PREAUTH feature, which can conflict with STARTTLS, encouraging unprotected connections from certain email clients.
– **Recommendation for Implicit TLS**: The research recommends using implicit TLS instead of STARTTLS to avoid the risks presented by the state transition in STARTTLS. Implicit TLS provides built-in encryption without the need for a transitional state.
– **Implementation Challenges**: While transitioning to implicit TLS is ideal, existing server operators may face user base challenges, as users would need to reconfigure their settings.
– **Future Client Recommendations**: The text advocates for future mail client development to exclusively use implicit TLS to enhance security practices without user intervention.
– **Server-to-Server STARTTLS Issues**: The document briefly touches on challenges related to server-to-server email communication using STARTTLS, noting the lack of secure, implicit methods for these connections, thus necessitating careful auditing of implementations.
– **Importance of Securing Implementations**: The text notes emerging standards like MTA-STS and DANE aimed at addressing the traditional weaknesses in opportunistically configured STARTTLS.
Overall, this analysis emphasizes the critical nature of securing email communication protocols and proposes practical recommendations for enhancing email security frameworks, which is highly relevant for security and compliance professionals managing email infrastructures.