Tuesday, October 19, 2021

Shadow Attacks … the smallest attack vector ever

In July 2020, we introduced a novel attack class called Shadow Attacks. In our recent research, we discovered a new variant of the attack which relies only on an Incremental Update containing a malicious trailer.
A proof-of-concept exploit working on Foxit (Version: 11.0.1.49938) can be downloaded here.

Thursday, June 10, 2021

ALPACA: Application Layer Protocol Confusion-Analyzing and Mitigating Cracks in TLS Authentication

In cooperation with the university Paderborn and Münster University of Applied Sciences, we discovered a new flaw in the specification of TLS. The vulnerability is called ALPACA and exploits a weakness in the authentication of TLS for cross-protocol attacks. The attack allows an attacker to steal cookies or perform cross-site-scripting (XSS) if the specific conditions for the attack are met.

Monday, May 31, 2021

Security Analysis in an OpenID Connect Lab Environment

In this post, Christian Fries shows an approach to unveil security flaws in OpenID Connect Certified implementations with well-known attack methods. One goal of the master's thesis Security Analysis of Real-Life OpenID Connect Implementations was to provide a platform for developers and security researchers to test implementations in a reproducible and maintainable OIDC lab environment.

We included six OpenID Provider (OP) and eight Relying Party (RP) services in the lab environment. For the comprehensive security analysis, we tested the implementations against eleven Relying Party attacks and seven OpenID Provider attacks in different variations with our tool PrOfESSOS. In addition, we carried out manual tests as well. We have disclosed twelve implementation flaws and reported them to the developers in a responsible disclosure process.

Two developer teams fixed (✔) the vulnerabilities before the deadline of the master's thesis. One Redirect URI Manipulation vulnerability was rejected (✖). This particular case can be permissible for only one registered URI for reasons of interoperability and fault tolerance. We informed three further development teams (✦).

Name Vulnerability Fixed CVE
MITREid Connect PKCE Downgrade Attack
mod auth openidc ID Spoofing, JWKS Spoofing
node oidc-provider Redirect URI Manipulation
OidcRP Replay Attack
phpOIDC Message Flow Confusion, ID Spoofing, Key Confusion
pyoidc Replay Attack, Signature Manipulation, Token Recipient Confusion CVE-2020-26244

We explain the method of how we have archived this result in the following sections.

Monday, May 24, 2021

Attacks on PDF Certification

In recent years, we have presented How to Spoof PDF Signatures and Shadow Attacks: Hiding and Replacing Content in Signed PDFs, which describe attacks on PDF signatures under various attack scenarios. The attacks focused on so-called approval signatures. However, in addition to signing PDFs, the PDF specification also specifies the certification of documents, also known as certification signatures.

To close this research gap, we performed an extensive analysis of the security of PDF certification. In doing so, we developed the Evil Annotation Attack (EAA), as well as the Sneaky Signature Attack (SSA). The attack idea exploits the flexibility of PDF certification, which allows signing or adding annotations to certified documents under different permission levels. Our practical evaluation shows that an attacker could change the visible content in 15 of 26 viewer applications by using EAA and in 8 applications using SSA by using PDF specification compliant exploits. We improved both attacks’ stealthiness with applications’ implementation issues and found only two applications secure to all attacks.

We responsibly disclosed all affected vendors. Together with the CERT-Bund (BSI), we supported the vendors in developing suitable countermeasures. The attacks are documented in CVE-2020-35931, CVE-2021-28545 and CVE-2021-28546.
Full results are available in our papervulnerability report and on our website.

Wednesday, February 24, 2021

Security and Privacy of Social Logins (III): Privacy in Single Sign-On Protocols

 This post is the second out of three blog posts summarizing my (Louis Jannett) research on the design, security, and privacy of real-world Single Sign-On (SSO) implementations. It is based on my master's thesis that I wrote between April and October 2020 at the Chair for Network and Data Security.

We structured this blog post series into three parts according to the research questions of my master's thesis: Single Sign-On Protocols in the Wild, PostMessage Security in Single Sign-On, and Privacy in Single Sign-On Protocols.

Overview

Part I: Single Sign-On Protocols in the Wild

Although previous work uncovered various security flaws in SSO, it did not work out uniform protocol descriptions of real-world SSO implementations. We summarize our in-depth analyses of Apple, Google, and Facebook SSO. We also refer to the sections of the thesis that provide more detailed insights into the protocol flows and messages.
It turned out that the postMessage API is commonly used in real-world SSO implementations. We introduce the reasons for this and propose security best practices on how to implement postMessage in SSO. Further, we present vulnerabilities on top-visited websites that caused DOM-based XSS and account takeovers due to insecure use of postMessage in SSO.

Part III: Privacy in Single Sign-On Protocols

Identity Providers (IdPs) use "zero-click" authentication flows to automatically sign in the user on the Service Provider (SP) once it is logged in on the IdP and has consented. We show that these flows can harm user privacy and enable new targeted deanonymization attacks of the user's identity.

Monday, February 22, 2021

Security and Privacy of Social Logins (II): PostMessage Security in Single Sign-On

This post is the second out of three blog posts summarizing my (Louis Jannett) research on the design, security, and privacy of real-world Single Sign-On (SSO) implementations. It is based on my master's thesis that I wrote between April and October 2020 at the Chair for Network and Data Security.

We structured this blog post series into three parts according to the research questions of my master's thesis: Single Sign-On Protocols in the Wild, PostMessage Security in Single Sign-On, and Privacy in Single Sign-On Protocols.

Overview

Part I: Single Sign-On Protocols in the Wild

Although previous work uncovered various security flaws in SSO, it did not work out uniform protocol descriptions of real-world SSO implementations. We summarize our in-depth analyses of Apple, Google, and Facebook SSO. We also refer to the sections of the thesis that provide more detailed insights into the protocol flows and messages.
It turned out that the postMessage API is commonly used in real-world SSO implementations. We introduce the reasons for this and propose security best practices on how to implement postMessage in SSO. Further, we present vulnerabilities on top-visited websites that caused DOM-based XSS and account takeovers due to insecure use of postMessage in SSO.

Part III: Privacy in Single Sign-On Protocols (coming soon)

Identity Providers (IdPs) use "zero-click" authentication flows to automatically sign in the user on the Service Provider (SP) once it is logged in on the IdP and has consented. We show that these flows can harm user privacy and enable new targeted deanonymization attacks of the user's identity.

Saturday, February 20, 2021

Security and Privacy of Social Logins (I): Single Sign-On Protocols in the Wild

This post is the first out of three blog posts summarizing my (Louis Jannett) research on the design, security, and privacy of real-world Single Sign-On (SSO) implementations. It is based on my master's thesis that I wrote between April and October 2020 at the Chair for Network and Data Security.

We structured this blog post series into three parts according to the research questions of my master's thesis: Single Sign-On Protocols in the Wild, PostMessage Security in Single Sign-On, and Privacy in Single Sign-On Protocols.

Overview

Part I: Single Sign-On Protocols in the Wild

Although previous work uncovered various security flaws in SSO, it did not work out uniform protocol descriptions of real-world SSO implementations. We summarize our in-depth analyses of Apple, Google, and Facebook SSO. We also refer to the sections of the thesis that provide more detailed insights into the protocol flows and messages.
It turned out that the postMessage API is commonly used in real-world SSO implementations. We introduce the reasons for this and propose security best practices on how to implement postMessage in SSO. Further, we present vulnerabilities on top-visited websites that caused DOM-based XSS and account takeovers due to insecure use of postMessage in SSO.

Part III: Privacy in Single Sign-On Protocols (coming soon)

Identity Providers (IdPs) use "zero-click" authentication flows to automatically sign in the user on the Service Provider (SP) once it is logged in on the IdP and has consented. We show that these flows can harm user privacy and enable new targeted deanonymization attacks of the user's identity.

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