ecfuzzer

Differential fuzzing for elliptic curves

Build

You can build a standalone binary with classic cmake commands

mkdir build
cd build
cmake ..
make

This standalone binary expects one argument, a file name, whose contents will be processed.

You can check out build.sh from oss-fuzz to build a fuzzing binary.

Architecture

List of files :

• main.c : main function for processing one file
• fuzz_ec.c : fuzz target, ie LLVMFuzzerTestOneInput function
• fuzz_ec.h : common structures for modules
• modules : directory with one file per module

Processing

The input buffer must be at least 4 bytes :

• 2 bytes are used to reference the curve (using the reference identifiers from TLS protocol)
• at least 1 byte for two big integers

For each module, the fuzzer will :

• load the curve (if the module does not know the curve, it is ok)
• do a scalar multiplication of first big integer with curve generator
• do a second scalar multiplication of second big integer with point resulting from first multiplication
• check the return code (abort on failure)
• check the result (point coordinates) with the previous module (abort on first difference)