201 lines
5.2 KiB
Markdown
201 lines
5.2 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 either:
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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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or:
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```bash
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make
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```
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Using cmake is the preferred method for building the shared library; the
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Makefile may be removed in the future.
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To run the tests when using cmake, 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 run the tests when using make, run:
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```bash
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make test
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```
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To build the JavaScript bindings, install emscripten from http://kripken.github.io/emscripten-site/ 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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To build olm as a static library (which still needs libstdc++ dynamically) run
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either:
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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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or
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```bash
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make static
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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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## 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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and ``android/olm-sdk/build.gradle`` (``versionCode``, ``versionName`` and
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``version``).
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Also, ensure the changelog is up to date, and that everyting 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 && npm run test)
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npm pack javascript
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VERSION=x.y.z
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scp olm-$VERSION.tgz packages@ares.matrix.org:packages/npm/olm/
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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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## 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.trust/us/our-research/matrix-olm-cryptographic-review/
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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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## Bug reports
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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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