--- 1/draft-ietf-uta-tls-attacks-03.txt 2014-09-28 11:14:38.176854373 -0700 +++ 2/draft-ietf-uta-tls-attacks-04.txt 2014-09-28 11:14:38.200854954 -0700 @@ -1,21 +1,21 @@ uta Y. Sheffer Internet-Draft Porticor Intended status: Informational R. Holz -Expires: March 13, 2015 TUM +Expires: April 1, 2015 TUM P. Saint-Andre &yet - September 9, 2014 + September 28, 2014 Summarizing Current Attacks on TLS and DTLS - draft-ietf-uta-tls-attacks-03 + draft-ietf-uta-tls-attacks-04 Abstract Over the last few years there have been several serious attacks on TLS, including attacks on its most commonly used ciphers and modes of operation. This document summarizes these attacks, with the goal of motivating generic and protocol-specific recommendations on the usage of TLS and DTLS. Status of This Memo @@ -26,21 +26,21 @@ Internet-Drafts are working documents of the Internet Engineering Task Force (IETF). Note that other groups may also distribute working documents as Internet-Drafts. The list of current Internet- Drafts is at http://datatracker.ietf.org/drafts/current/. Internet-Drafts are draft documents valid for a maximum of six months and may be updated, replaced, or obsoleted by other documents at any time. It is inappropriate to use Internet-Drafts as reference material or to cite them other than as "work in progress." - This Internet-Draft will expire on March 13, 2015. + This Internet-Draft will expire on April 1, 2015. Copyright Notice Copyright (c) 2014 IETF Trust and the persons identified as the document authors. All rights reserved. This document is subject to BCP 78 and the IETF Trust's Legal Provisions Relating to IETF Documents (http://trustee.ietf.org/license-info) in effect on the date of publication of this document. Please review these documents @@ -49,73 +49,78 @@ include Simplified BSD License text as described in Section 4.e of the Trust Legal Provisions and are provided without warranty as described in the Simplified BSD License. Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 2. Attacks on TLS . . . . . . . . . . . . . . . . . . . . . . . 3 2.1. SSL Stripping . . . . . . . . . . . . . . . . . . . . . . . 3 2.2. STARTTLS Command Injection Attack (CVE-2011-0411) . . . . . 3 - 2.3. BEAST (CVE-2011-3389) . . . . . . . . . . . . . . . . . . . 3 + 2.3. BEAST (CVE-2011-3389) . . . . . . . . . . . . . . . . . . . 4 2.4. Lucky Thirteen (CVE-2013-0169) . . . . . . . . . . . . . . 4 2.5. Attacks on RC4 . . . . . . . . . . . . . . . . . . . . . . 4 2.6. Compression Attacks: CRIME, TIME and BREACH . . . . . . . . 4 2.7. Certificate Attacks . . . . . . . . . . . . . . . . . . . . 5 2.8. Diffie-Hellman Parameters . . . . . . . . . . . . . . . . . 5 2.9. Renegotiation (CVE-2009-3555) . . . . . . . . . . . . . . . 5 2.10. Triple Handshake (CVE-2014-1295) . . . . . . . . . . . . . 5 - 2.11. Virtual Host Confusion . . . . . . . . . . . . . . . . . . 5 + 2.11. Virtual Host Confusion . . . . . . . . . . . . . . . . . . 6 2.12. Denial of Service . . . . . . . . . . . . . . . . . . . . . 6 2.13. Implementation Issues . . . . . . . . . . . . . . . . . . . 6 - 3. Applicability to DTLS . . . . . . . . . . . . . . . . . . . . 6 - 4. Security Considerations . . . . . . . . . . . . . . . . . . . 6 + 3. Applicability to DTLS . . . . . . . . . . . . . . . . . . . . 7 + 4. Security Considerations . . . . . . . . . . . . . . . . . . . 7 5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 7 6. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 7 7. Informative References . . . . . . . . . . . . . . . . . . . 7 Appendix A. Appendix: Change Log . . . . . . . . . . . . . . . . 10 - A.1. draft-ietf-uta-tls-attacks-03 . . . . . . . . . . . . . . . 10 - A.2. draft-ietf-uta-tls-attacks-02 . . . . . . . . . . . . . . . 10 - A.3. draft-ietf-uta-tls-attacks-01 . . . . . . . . . . . . . . . 10 - A.4. draft-ietf-uta-tls-attacks-00 . . . . . . . . . . . . . . . 11 + A.1. draft-ietf-uta-tls-attacks-04 . . . . . . . . . . . . . . . 10 + A.2. draft-ietf-uta-tls-attacks-03 . . . . . . . . . . . . . . . 10 + A.3. draft-ietf-uta-tls-attacks-02 . . . . . . . . . . . . . . . 11 + A.4. draft-ietf-uta-tls-attacks-01 . . . . . . . . . . . . . . . 11 + A.5. draft-ietf-uta-tls-attacks-00 . . . . . . . . . . . . . . . 11 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 11 1. Introduction Over the last few years there have been several major attacks on TLS [RFC5246], including attacks on its most commonly used ciphers and modes of operation. Details are given in Section 2, but suffice it to say that both AES-CBC and RC4, which together make up for most current usage, have been seriously attacked in the context of TLS. - This situation motivated the creation of the UTA working group, which - is tasked with the creation of generic and protocol-specific - recommendations for the use of TLS and DTLS. + This situation was one of the motivations for the creation of the UTA + working group, which is tasked with the creation of generic and + protocol-specific recommendations for the use of TLS and DTLS. "Attacks always get better; they never get worse" (ironically, this saying is attributed to the NSA). This list of attacks describes our knowledge as of this writing. It seems likely that new attacks will be invented in the future. For a more detailed discussion of the attacks listed here, the interested reader is referred to [Attacks-iSec]. 2. Attacks on TLS This section lists the attacks that motivated the current recommendations. This is not intended to be an extensive survey of TLS's security. While there are widely deployed mitigations for some of the attacks listed below, we believe that their root causes necessitate a more systemic solution. + When such an identifier exists for an attack, we have included its + CVE (Common Vulnerabilities and Exposures) ID. CVE [CVE] is an + extensive, industry-wide database of software vulnerabilities. + 2.1. SSL Stripping Various attacks attempt to remove the use of SSL/TLS altogether, by modifying unencrypted protocols that request the use of TLS, specifically modifying HTTP traffic and HTML pages as they pass on the wire. These attacks are known collectively as SSL Stripping and were first introduced by Moxie Marlinspike [SSL-Stripping]. In the context of Web traffic, these attacks are only effective if the client initially accesses a Web server using HTTP. A commonly used mitigation is HTTP Strict Transport Security (HSTS) [RFC6797]. @@ -200,23 +205,23 @@ The use of RSA certificates often involves exploitable timing issues [Brumley03] (CVE-2003-0147), unless the implementation takes care to explicitly eliminate them. A recent certificate fuzzing tool [Brubaker2014using] uncovered numerous vulnerabilities in different TLS libraries, related to certificate validation. 2.8. Diffie-Hellman Parameters - TLS allows to define ephemeral Diffie-Hellman and Elliptic Curve - Diffie-Hellman parameters in its respective key exchange modes. This - results in an attack detailed in [Cross-Protocol]. In addition, + TLS allows the definition of ephemeral Diffie-Hellman and Elliptic + Curve Diffie-Hellman parameters in its respective key exchange modes. + This results in an attack detailed in [Cross-Protocol]. In addition, clients that do not properly verify the received parameters are exposed to man in the middle (MITM) attacks. Unfortunately the TLS protocol does not require this verification, see [RFC6989] for the IPsec analogy. 2.9. Renegotiation (CVE-2009-3555) A major attack on the TLS renegotiation mechanism applies to all current versions of the protocol. The attack and the TLS extension that resolves it are described in [RFC5746]. @@ -244,25 +249,26 @@ turned on by default. However the risk of malicious clients and coordinated groups of clients ("botnets") mounting denial of service attacks is still very real. TLS adds another vector for computational attacks, since a client can easily (with little computational effort) force the server to expend relatively large computational work. It is known that such attacks have in fact been mounted. 2.13. Implementation Issues - Even when the protocol is fully specified, the are very common issues - that often plague implementations. In particular, the integration of - higher-level protocols, TLS and its PKI-based authentication is the - source of misunderstandings and implementation "shortcuts". An - extensive survey of these issues can be found in [Georgiev2012]. + Even when the protocol is fully specified, there are very common + issues that often plague implementations. In particular, when + integrating into higher-level protocols, TLS and its PKI-based + authentication are sometimes the source of misunderstandings and + implementation "shortcuts". An extensive survey of these issues can + be found in [Georgiev2012]. o Implementations may omit validation of the server certificate altogether. For example, this is true of the default implementation of HTTP client libraries in Python 2 (see e.g. CVE-2013-2191). o Implementations may not validate the server identity. This validation typically amounts to matching the protocol-level server name with the certificate's Subject Alternative Name field. Note: historically, although incorrect, this information is also often @@ -343,20 +349,23 @@ [I-D.ietf-tls-prohibiting-rc4] Popov, A., "Prohibiting RC4 Cipher Suites", draft-ietf- tls-prohibiting-rc4-00 (work in progress), July 2014. [I-D.ietf-tls-encrypt-then-mac] Gutmann, P., "Encrypt-then-MAC for TLS and DTLS", draft- ietf-tls-encrypt-then-mac-03 (work in progress), July 2014. + [CVE] MITRE, , "Common Vulnerabilities and Exposures", + . + [CBC-Attack] AlFardan, N. and K. Paterson, "Lucky Thirteen: Breaking the TLS and DTLS Record Protocols", IEEE Symposium on Security and Privacy , 2013. [BEAST] Rizzo, J. and T. Duong, "Browser Exploit Against SSL/TLS", 2011, . [CRIME] Rizzo, J. and T. Duong, "The CRIME Attack", EKOparty @@ -441,47 +450,51 @@ implementations", 2014. [Delignat14] Delignat-Lavaud, A. and K. Bhargavan, "Virtual Host Confusion: Weaknesses and Exploits", Black Hat 2014, 2014. Appendix A. Appendix: Change Log Note to RFC Editor: please remove this section before publication. -A.1. draft-ietf-uta-tls-attacks-03 +A.1. draft-ietf-uta-tls-attacks-04 + + o Implemented AD review comments. + +A.2. draft-ietf-uta-tls-attacks-03 o Implemented WG Last Call comments. o Virtual host confusion. o STARTTLS command injection. o Added CVE numbers. -A.2. draft-ietf-uta-tls-attacks-02 +A.3. draft-ietf-uta-tls-attacks-02 o Added implementation issues ("most dangerous code"), renegotiation, triple handshake. o Added text re: mitigation of Lucky13. o Added applicability to DTLS. -A.3. draft-ietf-uta-tls-attacks-01 +A.4. draft-ietf-uta-tls-attacks-01 o Added SSL Stripping, attacks related to certificates, Diffie Hellman parameters and denial of service. o Expanded on RC4 attacks, thanks to Andrei Popov. -A.4. draft-ietf-uta-tls-attacks-00 +A.5. draft-ietf-uta-tls-attacks-00 o Initial version, extracted from draft-sheffer-tls-bcp-01. Authors' Addresses Yaron Sheffer Porticor 29 HaHarash St. Hod HaSharon 4501303 Israel @@ -491,12 +504,15 @@ Ralph Holz Technische Universitaet Muenchen Boltzmannstr. 3 Garching 85748 Germany Email: holz@net.in.tum.de Peter Saint-Andre &yet + P.O. Box 787 + Parker, CO 80134 + USA - Email: ietf@stpeter.im + Email: peter@andyet.com