TLS (SSL) sockets, key generation, encryption, decryption, signing, verification and KDFs using the OS crypto libraries. Does not require a compiler, and relies on the OS for patching. Works on Windows, OS X and Linux/BSD.
A compilation-free, always up-to-date encryption library for Python that works on Windows, OS X, Linux and BSD. Supports the following versions of Python: 2.6, 2.7, 3.2, 3.3, 3.4, 3.5, 3.6, 3.7, 3.8, 3.9, 3.10 and pypy.
- Supported Operating Systems
- Why Another Python Crypto Library?
- Related Crypto Libraries
- Current Release
- Continuous Integration
- CI Tasks
Supported Operating Systems
The library integrates with the encryption library that is part of the operating system. This means that a compiler is never needed, and OS security updates take care of patching vulnerabilities. Supported operating systems include:
- Windows XP or newer
- OS X 10.7 or newer
- Tested on:
- OS X 10.7
- OS X 10.8
- OS X 10.9
- OS X 10.10
- OS X 10.11
- OS X 10.11 with OpenSSL 1.1.0
- macOS 10.12
- macOS 10.13 with LibreSSL 2.2.7
- macOS 10.14
- macOS 10.15
- macOS 10.15 with OpenSSL 3.0
- macOS 11
- macOS 12
- Linux or BSD
- Uses one of:
- Tested on:
- Arch Linux with OpenSSL 1.0.2
- OpenBSD 5.7 with LibreSSL
- Ubuntu 10.04 with OpenSSL 0.9.8
- Ubuntu 12.04 with OpenSSL 1.0.1
- Ubuntu 15.04 with OpenSSL 1.0.1
- Ubuntu 16.04 with OpenSSL 1.0.2 on Raspberry Pi 3 (armhf)
- Ubuntu 18.04 with OpenSSL 1.1.x (amd64, arm64, ppc64el)
- Ubuntu 22.04 with OpenSSL 3.0 (amd64)
OS X 10.6 will not be supported due to a lack of available cryptographic primitives and due to lack of vendor support.
Currently the following features are implemented. Many of these should only be used for integration with existing/legacy systems. If you don't know which you should, or should not use, please see Learning.
- TLSv1.x socket wrappers
- Certificate verification performed by OS trust roots
- Custom CA certificate support
- SNI support (except Windows XP)
- Session reuse via IDs/tickets
- Modern cipher suites (RC4, DES, anon and NULL ciphers disabled)
- Weak DH parameters and certificate signatures rejected
- SSLv3 disabled by default, SSLv2 unimplemented
- CRL/OCSP revocation checks consistenty disabled
- Exporting OS trust roots
- PEM-formatted CA certs from the OS for OpenSSL-based code
- AES (128, 192, 256), CBC mode, PKCS7 padding
- AES (128, 192, 256), CBC mode, no padding
- TripleDES 3-key, CBC mode, PKCS5 padding
- TripleDes 2-key, CBC mode, PKCS5 padding
- DES, CBC mode, PKCS5 padding
- RC2 (40-128), CBC mode, PKCS5 padding
- RC4 (40-128)
- RSA PKCSv1.5
- RSA OAEP (SHA1 only)
- Generating public/private key pairs
- RSA (1024, 2048, 3072, 4096 bit)
- DSA (1024 bit on all platforms - 2048, 3072 bit with OpenSSL 1.x or Windows 8)
- EC (secp256r1, secp384r1, secp521r1 curves)
- Generating DH parameters
- Signing and verification
- RSA PKCSv1.5
- RSA PSS
- Loading and normalizing DER and PEM formatted keys
- RSA public and private keys
- DSA public and private keys
- EC public and private keys
- X.509 Certificates
- PKCS#12 archives (
- Key derivation
- PKCS#12 KDF
- Random byte generation
The feature set was largely driven by the technologies used related to generating and validating X.509 certificates. The various CBC encryption schemes and KDFs are used to load encrypted private keys, and the various RSA padding schemes are part of X.509 signatures.
For modern cryptography not tied to an existing system, please see the Modern Cryptography section of the docs.
Please note that this library does not include modern block modes such as CTR and GCM due to lack of support from both OS X and OpenSSL 0.9.8.
Why Another Python Crypto Library?
In short, the existing cryptography libraries for Python didn't fit the needs of a couple of projects I was working on. Primarily these are applications distributed to end-users who aren't programmers, that need to handle TLS and various technologies related to X.509 certificates.
If your system is not tied to AES, TLS, X.509, or related technologies, you probably want more modern cryptography.
Depending on your needs, the cryptography package may be a good (or better) fit.
Some things that make oscrypto unique:
- No compiler needed, ever. No need to pre-compile shared libraries. Just distribute the Python source files, any way you want.
- Uses the operating system's crypto library - does not require OpenSSL on Windows or OS X.
- Relies on the operating system for security patching. You don't need to rebuild all of your apps every time there is a new TLS vulnerability.
- Intentionally limited in scope to crypto primitives. Other libraries built upon it deal with certificate path validation, creating certificates and CSRs, constructing CMS structures.
- Built on top of a fast, pure-Python ASN.1 parser, asn1crypto.
- TLS functionality uses the operating system's trust list/CA certs and is pre-configured with sane defaults
- Public APIs are simple and use strict type checks to avoid errors
Some downsides include:
- Does not currently implement:
- standalone DH key exchange
- various encryption modes such as GCM, CCM, CTR, CFB, OFB, ECB
- key wrapping
- Non-TLS functionality is architected for dealing with data that fits in memory and is available all at once
- Developed by a single developer
Related Crypto Libraries
oscrypto is part of the modularcrypto family of Python packages:
1.2.1 - changelog
- Python 2.6, 2.7, 3.2, 3.3, 3.4, 3.5, 3.6, 3.7, 3.8, 3.9, 3.10 or pypy
- OpenSSL/LibreSSL if on Linux¹
¹ On Linux,
ctypes.util.find_library() is used to located OpenSSL. Alpine Linux does not have an appropriate install by default for
find_library() to work properly. Instead,
oscrypto.use_openssl() must be called with the path to the OpenSSL shared libraries.
pip install oscrypto
oscrypto is licensed under the terms of the MIT license. See the LICENSE file for the exact license text.
Various combinations of platforms and versions of Python are tested via:
Tests are written using
unittest and require no third-party packages.
Depending on what type of source is available for the package, the following commands can be used to run the test suite.
When working within a Git working copy, or an archive of the Git repository, the full test suite is run via:
python run.py tests
To run only some tests, pass a regular expression as a parameter to
python run.py tests aes
To run tests multiple times, in order to catch edge-case bugs, pass an integer
tests. If combined with a regular expression for filtering, pass the
repeat count after the regular expression.
python run.py tests 20 python run.py tests aes 20
To run tests using a custom build of OpenSSL, or to use OpenSSL on Windows or
python run.py use_openssl=/path/to/libcrypto.so,/path/to/libssl.so tests
To run tests forcing the use of ctypes, even if cffi is installed, add
python run.py use_ctypes=true tests
To run tests using the legacy Windows crypto functions on Windows 7+, add
python run.py use_winlegacy=true tests
To skip tests that require an internet connection, add
python run.py skip_internet=true tests
PyPi Source Distribution
When working within an extracted source distribution (aka
PyPi, the full test suite is run via:
python setup.py test
The following env vars can control aspects of running tests:
Force OpenSSL Shared Library Paths
Setting the env var
OSCRYPTO_USE_OPENSSL to a string in the form:
will force use of specific OpenSSL shared libraries.
This also works on Mac and Windows to force use of OpenSSL instead of using native crypto libraries.
Force Use of ctypes
By default, oscrypto will use the
cffi module for FFI if it is installed.
To use the slightly slower, but more widely-tested,
ctypes FFI layer, set
the env var
Force Use of Legacy Windows Crypto APIs
On Windows 7 and newer, oscrypto will use the CNG backend by default.
To force use of the older CryptoAPI, set the env var
Skip Tests Requiring an Internet Connection
Some of the TLS tests require an active internet connection to ensure that various "bad" server certificates are rejected.
To skip tests requiring an internet connection, set the env var
When the package has been installed via pip (or another method), the package
oscrypto_tests may be installed and invoked to run the full test suite:
pip install oscrypto_tests python -m oscrypto_tests
To install the package used for linting, execute:
pip install --user -r requires/lint
The following command will run the linter:
python run.py lint
Support for code coverage can be installed via:
pip install --user -r requires/coverage
Coverage is measured by running:
python run.py coverage
To install the packages requires to generate the API documentation, run:
pip install --user -r requires/api_docs
The documentation can then be generated by running:
python run.py api_docs
To install the necessary packages for releasing a new version on PyPI, run:
pip install --user -r requires/release
Releases are created by:
Making a git tag in semver format
Running the command:
python run.py release
Existing releases can be found at https://pypi.python.org/pypi/oscrypto.
A task named
deps exists to download and stage all necessary testing
dependencies. On posix platforms,
curl is used for downloads and on Windows
Net.WebClient is used. This configuration sidesteps issues
related to getting pip to work properly and messing with
the version of Python being used.
ci task runs
lint (if flake8 is available for the version of Python) and
tests if coverage is not available for the version of Python).
If the current directory is a clean git working copy, the coverage data is
submitted to codecov.io.
python run.py deps python run.py ci
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