Category Archives: Exploitation

SMEP: What is It, and How to Beat It on Linux

On May 16, 2011, Fenghua Yu submitted a series of patches to the upstream Linux kernel implementing support for a new Intel CPU feature: Supervisor Mode Execution Protection (SMEP). This feature is enabled by toggling a bit in the cr4 register, and the result is the CPU will generate a fault whenever ring0 attempts to execute code from a page marked with the user bit.

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Breaking LibTIFF

In this post I’ll be providing details on a vulnerability I discovered in libtiff, which was recently made public with CVE-2010-2067. libtiff is linked into a wide range of applications, including browsers, document viewers, file browsers, and image software, and it might even be possible to leverage this bug to achieve code execution on embedded devices.

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Integer overflow in (CVE-2010-0830)

A month or so ago, I reported an integer overflow vulnerability in (the linker/loader included with glibc) that could be exploited to achieve arbitrary code execution. The catch is, the vulnerability is triggered in the processing of a maliciously crafted ELF binary, so the actual potential for exploitation in real life is minimal. In many cases, invoking on an untrusted binary results in the execution of that binary, so in practice this should never be done. However, there are some options that can be used with that should not result in code execution, such as the case … Continue reading

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I wanted to share a neat little trick I discovered while playing with gcc’s FORTIFY_SOURCE feature.

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Controlling uninitialized memory with LD_PRELOAD

In this post, I’ll be describing a technique that allows a local Linux user to exercise a degree of control over uninitialized memory on the stack when executing a program.

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Exploiting nano

A number of standard Linux utilities have been documented as being unsafe to run as root on untrusted input, from a security standpoint. For example, the ldd utility, designed to enumerate the dynamic library dependencies of executables, has documented behavior that may result in execution of arbitrary code when run on untrusted binaries [1]. The popular text editor, nano, is another example of a program that is unsafe to run as root on untrusted input. I hope to demonstrate that many of the assumptions users make in regards to security no longer apply in the scenario of running as root … Continue reading

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