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#29 in Debugging

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Used in 2 crates


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Crates.io Documentation codecov License

amd64 aarch64 riscv64 darwin-arm64 fuzzing

CASR: Crash Analysis and Severity Report

CASR – collect crash (or UndefinedBehaviorSanitizer error) reports, triage, and estimate severity. It is based on ideas from exploitable and apport.

CASR is maintained by:


CASR is a set of tools that allows you to collect crash reports in different ways. Use casr-core binary to deal with coredumps. Use casr-san to analyze ASAN reports or casr-ubsan to analyze UBSAN reports. Try casr-gdb to get reports from gdb. Use casr-python to analyze python reports and get report from Atheris. Use casr-java to analyze java reports and get report from Jazzer. Use casr-js to analyze JavaScript reports and get report from Jazzer.js or jsfuzz. Use casr-csharp to analyze C# reports and get report from Sharpfuzz.

Crash report contains many useful information: severity (like exploitable) for x86, x86_64, arm32, aarch64, rv32g, rv64g architectures, OS and package versions, command line, stack trace, register values, disassembly, and even source code fragment where crash appeared. Reports are stored in JSON format. casr-cli is meant to provide TUI for viewing reports and converting them into SARIF report. Reports triage (deduplication, clustering) is done by casr-cluster. Triage is based on stack trace comparison from gdb-command. casr-afl is used to triage crashes found by AFL++ and AFL-based fuzzer Sharpfuzz. casr-libfuzzer can triage crashes found by libFuzzer based fuzzer (C/C++/go-fuzz/Atheris /Jazzer/Jazzer.js/ jsfuzz). casr-dojo allows to upload new and unique CASR reports to DefectDojo (available with dojo feature).

Explanation of severity classes could be found here. You could take a closer look at usage details here.




LibCASR provides API for parsing stacktraces, collecting crash reports, triaging crashes (deduplication and clustering), and estimating severity of crashes.

It can analyze crashes from different sources:

  • AddressSanitizer
  • UndefinedBehaviorSanitizer
  • Gdb output

and program languages:

  • C/C++
  • Rust
  • Go
  • Python
  • Java
  • JavaScript
  • C#

It could be built with exploitable feature for severity estimation crashes collected from gdb. To save crash reports as json use serde feature.


Install runtime dependencies:

$ sudo apt install gdb lsb-release

Install build dependencies when building from source:

$ sudo apt install build-essential clang

Install Rust or update existing Rust installation:

$ rustup update


Download latest Linux 64-bit release or build from source as explained below.

N.B. Current MacOS support is experimental. Some Linux-based code like exploitable and casr-gdb may not properly work. Further contributions are very much welcomed here.

Build from Git repository:

$ git clone https://github.com/ispras/casr
$ cargo update
$ cargo build --release

Or you may just install Casr from crates.io:

$ cargo install casr

Add dojo feature if you want to install casr-dojo (the same for cargo build):

$ cargo install -F dojo casr


Running in Docker: CASR disables address randomization for better deduplication and uses ptrace to run GDB. Thus, Docker should be started with --cap-add=SYS_PTRACE --security-opt seccomp=unconfined.

Create report from coredump:

$ casr-core -f casr/tests/casr_tests/bin/core.test_destAv -e casr/tests/casr_tests/bin/test_destAv -o destAv.casrep

Create report from AddressSanitizer output:

$ clang++ -fsanitize=address -O0 -g casr/tests/casr_tests/test_asan_df.cpp -o test_asan_df
$ casr-san -o asan.casrep -- ./test_asan_df

Create report from UndefinedBehaviorSanitizer output:

$ clang++ -fsanitize=undefined -O0 -g casr/tests/casr_tests/ubsan/test_ubsan.cpp -o test_ubsan
$ casr-ubsan -i casr/tests/casr_tests/ubsan/input1 -o output -- ./test_ubsan @@
$ casr-cli output

Create report from gdb:

$ casr-gdb -o destAv.gdb.casrep -- casr/tests/casr_tests/bin/test_destAv $(printf 'A%.s' {1..200})

Create report from python:

$ casr-python -o python.casrep -- casr/tests/casr_tests/python/test_casr_python.py

Create report from java:

$ casr-java -o java.casrep -- java casr/tests/casr_tests/java/Test1.java

Create report from JavaScript:

$ casr-js -o js.casrep -- node casr/tests/casr_tests/js/test_casr_js.js

Create report from C#:

$ casr-csharp -o csharp.casrep -- dotnet run --project casr/tests/casr_tests/csharp/test_casr_csharp/test_casr_csharp.csproj

View report:

$ casr-cli casr/tests/casr_tests/casrep/test_clustering_san/load_fuzzer_crash-120697a7f5b87c03020f321c8526adf0f4bcc2dc.casrep

View joint statistics about crash clusters:

$ casr-cli casr_reports

Convert reports to SARIF report:

$ casr-cli --sarif out.sarif --tool libfuzzer --source-root /xlnt casr/tests/casr_tests/casrep/test_clustering_san

Create report for program that reads stdin:

$ casr-san --stdin seed -o san_bin.casrep -- ./san_bin

Deduplicate reports:

$ casr-cluster -d casr/tests/casr_tests/casrep/test_clustering_gdb out-dedup

Cluster reports:

$ casr-cluster -c out-dedup out-cluster

Triage crashes after AFL++ fuzzing with casr-afl:

$ cp casr/tests/casr_tests/bin/load_afl /tmp/load_afl
$ cp casr/tests/casr_tests/bin/load_sydr /tmp/load_sydr
$ casr-afl -i casr/tests/casr_tests/casrep/afl-out-xlnt -o casr/tests/tmp_tests_casr/casr_afl_out
$ # You may also additionally generate crash reports for uninstrumented binary with casr-gdb
$ casr-afl -i casr/tests/casr_tests/casrep/afl-out-xlnt -o casr/tests/tmp_tests_casr/casr_afl_out -- /tmp/load_sydr @@

Triage crashes after Sharpfuzz fuzzing with casr-afl:

$ cp -r casr/tests/casr_tests/csharp/test_casr_afl_csharp /tmp/test_casr_afl_csharp
$ cp -r casr/tests/casr_tests/csharp/test_casr_afl_csharp_module /tmp/test_casr_afl_csharp_module
$ dotnet publish /tmp/test_casr_afl_csharp/test_casr_afl_csharp.csproj -c Debug -o /tmp/test_casr_afl_csharp/bin
$ casr-afl -i casr/tests/casr_tests/casrep/afl-out-sharpfuzz -o casr/tests/tmp_tests_casr/casr_afl_csharp_out
$ # You may force your own run arguments using --ignore-cmdline
$ casr-afl --ignore-cmdline -i casr/tests/casr_tests/casrep/afl-out-sharpfuzz -o casr/tests/tmp_tests_casr/casr_afl_csharp_out -- dotnet run --no-build --project /tmp/test_casr_afl_csharp/test_casr_afl_csharp.csproj @@

Triage libFuzzer crashes with casr-libfuzzer:

$ casr-libfuzzer -t 30 -i casr/tests/casr_tests/casrep/libfuzzer_crashes_xlnt -o casr/tests/tmp_tests_casr/casr_libfuzzer_out -- casr/tests/casr_tests/bin/load_fuzzer

Triage Atheris crashes with casr-libfuzzer:

$ unzip casr/tests/casr_tests/python/ruamel.zip
$ casr-libfuzzer -i casr/tests/casr_tests/casrep/atheris_crashes_ruamel_yaml -o casr/tests/tmp_tests_casr/casr_libfuzzer_atheris_out -- casr/tests/casr_tests/python/yaml_fuzzer.py

Triage Jazzer.js crashes with casr-libfuzzer (Jazzer.js installation guide):

$ unzip casr/tests/casr_tests/js/xml2js.zip -d xml2js
$ mkdir -p casr/tests/tmp_tests_casr/xml2js_fuzzer_out
$ cp casr/tests/casr_tests/js/test_casr_libfuzzer_jazzer_js_xml2js.js casr/tests/tmp_tests_casr/xml2js_fuzzer_out/xml2js_fuzzer.js
$ sudo npm install xml2js
$ sudo npm install --save-dev @jazzer.js/core
$ casr-libfuzzer -i ./xml2js -o casr/tests/tmp_tests_casr/xml2js_fuzzer_out/out -- npx jazzer casr/tests/tmp_tests_casr/xml2js_fuzzer_out/xml2js_fuzzer.js

Upload new and unique CASR reports to DefectDojo:

$ echo '[product]' > dojo.toml
$ echo 'name = "xlnt"' >> dojo.toml
$ echo '[engagement]' >> dojo.toml
$ echo "name = \"load_fuzzer $(date -Isec)\"" >> dojo.toml
$ echo '[test]' >> dojo.toml
$ echo 'test_type = "CASR DAST Report"' >> dojo.toml
$ casr-dojo -i casr/tests/casr_tests/casrep/test_clustering_san -u http://localhost:8080 -t 382f5dfdf2a339f7c3bb35442f9deb9b788a98d5 dojo.toml

Fuzzing Crash Triage Pipeline

When you have crashes from fuzzing you may do the following steps:

  1. Create reports for all crashes via casr-san, casr-gdb (if no sanitizers are present), casr-python, casr-java, casr-js, or casr-csharp.
  2. Deduplicate collected crash reports via casr-cluster -d.
  3. Cluster deduplicated crash reports via casr-cluster -c.
  4. Create reports and deduplicate them for all UBSAN errors via casr-ubsan.
  5. View reports from clusters using casr-cli or upload them to DefectDojo with casr-dojo.

If you use AFL++ or AFL-based fuzzer Sharpfuzz, the pipeline (without casr-ubsan and casr-dojo) could be done automatically by casr-afl.

If you use libFuzzer based fuzzer (C/C++/go-fuzz/Atheris /Jazzer/Jazzer.js/ jsfuzz), the pipeline (without casr-ubsan and casr-dojo) could be done automatically by casr-libfuzzer.


Feel free to open issues or PRs (especially pay attention to help wanted issues)! We appreciate your support!

Please follow the next recommendations for your pull requests:

  • compile with stable rust
  • use cargo fmt
  • check the output of cargo clippy --all-features --all --tests
  • run tests cargo test
  • if you have updated usage of any casr tool, you could simply run update_usage.py to change the docs/usage.md file properly

Cite Us

Savidov G., Fedotov A. Casr-Cluster: Crash Clustering for Linux Applications. 2021 Ivannikov ISPRAS Open Conference (ISPRAS), IEEE, 2021, pp. 47-51. DOI: 10.1109/ISPRAS53967.2021.00012 [paper] [slides]

  title = {{{Casr-Cluster}}: Crash Clustering for Linux Applications},
  author = {Savidov, Georgy and Fedotov, Andrey},
  booktitle = {2021 Ivannikov ISPRAS Open Conference (ISPRAS)},
  pages = {47--51},
  year = {2021},
  organization = {IEEE},
  doi = {10.1109/ISPRAS53967.2021.00012},

Andrey Fedotov, Alexey Vishnyakov. CASR: Your Life Vest in a Sea of Crashes. OFFZONE 2023. [slides] [russian video]


Licensed under Apache-2.0.


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