mirror of https://git.matrix.org/git/olm.git
172 lines
4.7 KiB
ReStructuredText
172 lines
4.7 KiB
ReStructuredText
Olm
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===
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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.rst>`_.
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This library also includes an implementation of the Megolm cryptographic
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ratchet, as specified in `<docs/megolm.rst>`_.
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Building
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--------
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To build olm as a shared library run:
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.. code:: bash
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make
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To run the tests run:
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.. code:: bash
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make test
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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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.. code:: bash
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make js
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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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.. code:: bash
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cd android
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./gradlew clean assembleRelease
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To build the Xcode workspace for Objective-C bindings, run:
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.. code:: bash
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cd xcode
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pod install
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open OLMKit.xcworkspace
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To build olm as a static library (which still needs libstdc++ dynamically) run:
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.. code:: bash
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make static
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Release process
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---------------
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First: bump version numbers in ``common.mk``, ``javascript/package.json``,
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``OLMKit.podspec``, and ``android/olm-sdk/build.gradle`` (``versionCode``,
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``versionName`` and ``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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.. code:: 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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Design
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------
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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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~~~~~~~~~~~~~~
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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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~~~~~~~~~~~~~~
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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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~~~~~~
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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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~~~~~~~~~~~~~~~
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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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~~~~~~~~~~~~
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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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------------
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Please see `<CONTRIBUTING.rst>`_ when making contributions to the library.
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Security assessment
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-------------------
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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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-----------
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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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--------------
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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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------------
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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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