Summary

This is a proof-of-concept exploit of the PortSmash microarchitecture attack, tracked by CVE-2018-5407.

Setup

Prerequisites

A CPU featuring SMT (e.g. Hyper-Threading) is the only requirement.

This exploit code should work out of the box on Skylake and Kaby Lake. For other SMT architectures, customizing the strategies and/or waiting times in spy is likely needed.

OpenSSL

Download and install OpenSSL 1.1.0h or lower:

cd /usr/local/src
wget https://www.openssl.org/source/openssl-1.1.0h.tar.gz
tar xzf openssl-1.1.0h.tar.gz
cd openssl-1.1.0h/
export OPENSSL_ROOT_DIR=/usr/local/ssl
./config -d shared --prefix=$OPENSSL_ROOT_DIR --openssldir=$OPENSSL_ROOT_DIR -Wl,-rpath=$OPENSSL_ROOT_DIR/lib
make -j8
make test
sudo checkinstall --strip=no --stripso=no --pkgname=openssl-1.1.0h-debug --provides=openssl-1.1.0h-debug --default make install_sw

If you use a different path, you'll need to make changes to Makefile and sync.sh.

Tooling

freq.sh

Turns off frequency scaling and TurboBoost.

sync.sh

Sync trace through pipes. It has two victims, one of which should be active at a time:

1. The stock openssl running dgst command to produce a P-384 signature.
2. A harness ecc that calls scalar multiplication directly with a known key. (Useful for profiling.)

The script will generate a P-384 key pair in secp384r1.pem if it does not already exist.

The script outputs data.bin which is what openssl dgst signed, and you should be able to verify the ECDSA signature data.sig afterwards with

openssl dgst -sha512 -verify secp384r1.pem -signature data.sig data.bin

In the ecc tool case, data.bin and secp384r1.pem are meaningless and data.sig is not created.

For the taskset commands in sync.sh, the cores need to be two logical cores of the same physical core; sanity check with

$ grep '^core id' /proc/cpuinfo
core id		: 0
core id		: 1
core id		: 2
core id		: 3
core id		: 0
core id		: 1
core id		: 2
core id		: 3

So the script is currently configured for logical cores 3 and 7 that both map to physical core 3 (core_id).

spy

Measurement process that outputs measurements in timings.bin. To change the spy strategy, check the port defines in spy.h. Only one strategy should be active at build time.

Note that timings.bin is actually raw clock cycle counter values, not latencies. Look in parse_raw_simple.py to understand the data format if necessary.

ecc

Victim harness for running OpenSSL scalar multiplication with known inputs. Example:

./ecc M 4 deadbeef0123456789abcdef00000000c0ff33

Will execute 4 consecutive calls to EC_POINT_mul with the given hex scalar.

parse_raw_simple.py

Quick and dirty hack to view 1D traces. The top plot is the raw trace. Everything below is a different digital filter of the raw trace for viewing purposes. Zoom and pan are your friends here.

You might have to adjust the CEIL variable if the plots are too aggressively clipped.

Python packages:

sudo apt-get install python-numpy python-matplotlib

Usage

Turn off frequency scaling:

./freq.sh

Make sure everything builds:

make clean
make

Take a measurement:

./sync.sh

View the trace:

python parse_raw_simple.py timings.bin

You can play around with one victim at a time in sync.sh. Sample output for the openssl dgst victim is in parse_raw_simple.png.

Credits

• Alejandro Cabrera Aldaya (Universidad Tecnológica de la Habana (CUJAE), Habana, Cuba)
• Billy Bob Brumley (Tampere University of Technology, Tampere, Finland)
• Sohaib ul Hassan (Tampere University of Technology, Tampere, Finland)
• Cesar Pereida García (Tampere University of Technology, Tampere, Finland)
• Nicola Tuveri (Tampere University of Technology, Tampere, Finland)