TY  - CHAP
A1  - Müller, Jens
A1  - Brinkmann, Marcus
A1  - Poddebniak, Damian
A1  - Schinzel, Sebastian
A1  - Schwenk, Jörg
T1  - Mailto: Me Your Secrets. On Bugs and Features in Email End-to-End Encryption
T2  - 2020 IEEE Conference on Communications and Network Security (CNS)
N2  - OpenPGP and S/MIME are the two major standards for email end-to-end encryption. We show practical attacks against both encryption schemes in the context of email. First, we present a design flaw in the key update mechanism, allowing a third party to deploy a new key to the communication partners. Second, we show how email clients can be tricked into acting as an oracle for decryption or signing by exploiting their functionality to auto-save drafts. Third, we demonstrate how to exfiltrate the private key, based on proprietary mailto parameters implemented by various email clients. An evaluation shows that 8 out of 20 tested email clients are vulnerable to at least one attack. While our attacks do not target the underlying cryptographic primitives, they raise concerns about the practical security of OpenPGP and S/MIME email applications. Finally, we propose countermeasures and discuss their advantages and disadvantages.
KW  - Cyber Security
KW  - PGP
KW  - S/MIME
Y1  - 2020
U6  - http://dx.doi.org/10.1109/CNS48642.2020.9162218
SP  - 1
EP  - 9
ER  - 
TY  - CHAP
A1  - Müller, Jens
A1  - Ising, Fabian
A1  - Mla­de­nov, Vla­dis­lav
A1  - Mainka, Chris­ti­an
A1  - Schinzel, Sebastian
A1  - Schwenk, Jörg
T1  - Of­fice Do­cu­ment Se­cu­ri­ty and Pri­va­cy
T2  - 14th USE­NIX Work­shop on Of­fen­si­ve Tech­no­lo­gies (WOOT 2020)
N2  - OOXML and ODF are the de facto standard data formats for word processing, spreadsheets, and presentations. Both are XML-based, feature-rich container formats dating back to the early 2000s. In this work, we present a systematic analysis of the capabilities of malicious office documents. Instead of focusing on implementation bugs, we abuse legitimate features of the OOXML and ODF specifications. We categorize our attacks into five classes: (1) Denial-of-Service attacks affecting the host on which the document is processed. (2) Invasion of privacy attacks that track the usage of the document. (3) Information disclosure attacks exfiltrating personal data out of the victim's computer. (4) Data manipulation on the victim's system. (5) Code execution on the victim's machine. We evaluated the reference implementations – Microsoft Office and LibreOffice – and found both of them to be vulnerable to each tested class of attacks. Finally, we propose mitigation strategies to counter these attacks.
KW  - Cyber Security
KW  - Open Document Format
KW  - docx
Y1  - 2020
UR  - https://www.usenix.org/conference/woot20/presentation/muller
PB  - USENIX
ER  -