240 lines
7.1 KiB
Markdown
240 lines
7.1 KiB
Markdown
# Olm
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An implementation of the Double Ratchet cryptographic ratchet described by
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https://whispersystems.org/docs/specifications/doubleratchet/, written in C and
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C++11 and exposed as a C API.
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The specification of the Olm ratchet can be found in [docs/olm.md](docs/olm.md).
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This library also includes an implementation of the Megolm cryptographic
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ratchet, as specified in [docs/megolm.md](docs/megolm.md).
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## Building
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To build olm as a shared library run:
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```bash
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cmake . -Bbuild
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cmake --build build
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```
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To run the tests, run:
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```bash
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cd build/tests
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ctest .
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```
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To build olm as a static library (which still needs libstdc++ dynamically) run:
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```bash
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cmake . -Bbuild -DBUILD_SHARED_LIBS=NO
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cmake --build build
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```
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The library can also be used as a dependency with CMake using:
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```cmake
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find_package(Olm::Olm REQUIRED)
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target_link_libraries(my_exe Olm::Olm)
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```
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### Bindings
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To build the JavaScript bindings, install emscripten from https://emscripten.org/ and then run:
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```bash
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make js
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```
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Note that if you run emscripten in a docker container, you need to pass through
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the EMCC_CLOSURE_ARGS environment variable.
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To build the android project for Android bindings, run:
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```bash
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cd android
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./gradlew clean assembleRelease
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```
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To build the Xcode workspace for Objective-C bindings, run:
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```bash
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cd xcode
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pod install
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open OLMKit.xcworkspace
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```
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To build the Python bindings, first build olm as a shared library as above, and
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then run:
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```bash
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cd python
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make
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```
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to make both the Python 2 and Python 3 bindings. To make only one version, use
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``make olm-python2`` or ``make olm-python3`` instead of just ``make``.
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### Using make instead of cmake
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**WARNING:** Using cmake is the preferred method for building the olm library;
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the Makefile may be removed in the future or have functionality removed. In
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addition, the Makefile may make certain assumptions about your system and is
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not as well tested.
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To build olm as a dynamic library, run:
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```bash
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make
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```
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To run the tests, run:
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```bash
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make test
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```
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To build olm as a static library, run:
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```bash
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make static
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```
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## Bindings
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libolm can be used in different environments using bindings. In addition to the
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JavaScript, Python, Java (Android), and Objective-C bindings included in this
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repository, some bindings are (in alphabetical order):
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- [cl-megolm](https://github.com/K1D77A/cl-megolm) (MIT) Common Lisp bindings
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- [dart-olm](https://gitlab.com/famedly/company/frontend/libraries/dart-olm) (AGPLv3) Dart bindings
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- [Dhole/go-olm](https://github.com/Dhole/go-olm) (Apache-2.0) Go bindings
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- [jOlm](https://github.com/brevilo/jolm) (Apache-2.0) Java bindings
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- [libQtOlm](https://gitlab.com/b0/libqtolm/) (GPLv3) Qt bindings
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- [matrix-kt](https://github.com/Dominaezzz/matrix-kt) (Apache-2.0) Kotlin
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library for Matrix, including Olm methods
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- [maunium.net/go/mautrix/crypto/olm](https://github.com/tulir/mautrix-go/tree/master/crypto/olm)
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(Apache-2.0) fork of Dhole/go-olm
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- [nim-olm](https://gitea.com/BarrOff/nim-olm) (MIT) Nim bindings
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- [olm-sys](https://gitlab.gnome.org/BrainBlasted/olm-sys) (Apache-2.0) Rust
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bindings
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Note that bindings may have a different license from libolm, and are *not*
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endorsed by the Matrix.org Foundation C.I.C.
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## Release process
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First: bump version numbers in ``common.mk``, ``CMakeLists.txt``,
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``javascript/package.json``, ``python/olm/__version__.py``, ``OLMKit.podspec``,
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``Package.swift``, and ``android/gradle.properties``.
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Also, ensure the changelog is up to date, and that everything is committed to
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git.
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It's probably sensible to do the above on a release branch (``release-vx.y.z``
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by convention), and merge back to master once the release is complete.
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```bash
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make clean
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# build and test C library
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make test
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# build and test JS wrapper
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make js
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(cd javascript && \
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npm run test && \
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sha256sum olm.js olm_legacy.js olm.wasm > checksums.txt && \
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gpg -b -a -u F75FDC22C1DE8453 checksums.txt && \
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npm publish)
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VERSION=x.y.z
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git tag $VERSION -s
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git push --tags
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# OLMKit CocoaPod release
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# Make sure the version OLMKit.podspec is the same as the git tag
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# (this must be checked before git tagging)
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pod spec lint OLMKit.podspec --use-libraries --allow-warnings
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pod trunk push OLMKit.podspec --use-libraries --allow-warnings
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# Check the pod has been successully published with:
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pod search OLMKit
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```
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Python and JavaScript packages are published to the registry at
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<https://gitlab.matrix.org/matrix-org/olm/-/packages>. The GitLab
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documentation contains instructions on how to set up twine (Python) and npm
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(JavaScript) to upload to the registry.
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## Design
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Olm is designed to be easy port to different platforms and to be easy
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to write bindings for.
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It was originally implemented in C++, with a plain-C layer providing the public
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API. As development has progressed, it has become clear that C++ gives little
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advantage, and new functionality is being added in C, with C++ parts being
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rewritten as the need ariases.
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### Error Handling
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All C functions in the API for olm return ``olm_error()`` on error.
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This makes it easy to check for error conditions within the language bindings.
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### Random Numbers
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Olm doesn't generate random numbers itself. Instead the caller must
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provide the random data. This makes it easier to port the library to different
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platforms since the caller can use whatever cryptographic random number
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generator their platform provides.
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### Memory
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Olm avoids calling malloc or allocating memory on the heap itself.
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Instead the library calculates how much memory will be needed to hold the
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output and the caller supplies a buffer of the appropriate size.
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### Output Encoding
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Binary output is encoded as base64 so that languages that prefer unicode
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strings will find it easier to handle the output.
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### Dependencies
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Olm uses pure C implementations of the cryptographic primitives used by
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the ratchet. While this decreases the performance it makes it much easier
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to compile the library for different architectures.
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## Contributing
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Please see [CONTRIBUTING.md](CONTRIBUTING.md) when making contributions to the library.
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## Security assessment
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Olm 1.3.0 was independently assessed by NCC Group's Cryptography Services
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Practive in September 2016 to check for security issues: you can read all
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about it at
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https://www.nccgroup.com/globalassets/our-research/us/public-reports/2016/november/ncc_group_olm_cryptogrpahic_review_2016_11_01.pdf
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and https://matrix.org/blog/2016/11/21/matrixs-olm-end-to-end-encryption-security-assessment-released-and-implemented-cross-platform-on-riot-at-last/
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## Security issues
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If you think you found a security issue in libolm, any of its bindings or the Olm/Megolm protocols, please follow our [Security Disclosure Policy](https://matrix.org/security-disclosure-policy/) to report.
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## Bug reports
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For non-sensitive bugs, please file bug reports at https://github.com/matrix-org/olm/issues.
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## What's an olm?
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It's a really cool species of European troglodytic salamander.
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http://www.postojnska-jama.eu/en/come-and-visit-us/vivarium-proteus/
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## Legal Notice
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The software may be subject to the U.S. export control laws and regulations
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and by downloading the software the user certifies that he/she/it is
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authorized to do so in accordance with those export control laws and
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regulations.
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