A local copy of OpenSSL from GitHub
You cannot select more than 25 topics Topics must start with a letter or number, can include dashes ('-') and can be up to 35 characters long.
Matt Caswell d2015a783e Fix the name constraints code to not assume NUL terminated strings
ASN.1 strings may not be NUL terminated. Don't assume they are.


Reviewed-by: Viktor Dukhovni <viktor@openssl.org>
Reviewed-by: Paul Dale <pauli@openssl.org>
Reviewed-by: David Benjamin <davidben@google.com>
2 years ago
.github CI: remove spurious blank lines 2 years ago
Configurations Use copy.pl to install the fips module on Windows 2 years ago
VMS VMS documentation fixes 2 years ago
apps Get rid of warn_binary 2 years ago
crypto Fix the name constraints code to not assume NUL terminated strings 2 years ago
demos Add config_diagnostics to our configuration files. 2 years ago
dev Ensure ordinals are created during release process 2 years ago
doc Fix documentation referring to 'function code' 2 years ago
engines afalg: add some memory initialisation calls to pacify memory sanitisation. 2 years ago
external/perl Update the bundled external perl module Text-Template to version 1.56 4 years ago
fuzz Update copyright year 2 years ago
gost-engine@62583fb222 Updated gost-engine to latest commit from master branch 2 years ago
include Fix i2v_GENERAL_NAME to not assume NUL terminated strings 2 years ago
krb5@aa9b4a2a64 Update dependencies for krb5 external test 2 years ago
ms Update copyright year 2 years ago
os-dep Move Haiku configuration to separate config file to denote 7 years ago
providers pkcs12: check for zero length digest to avoid division by zero 2 years ago
pyca-cryptography@0034926f2c update pyca-cryptography regression test suite 2 years ago
ssl Fix state name abbreviation 2 years ago
test Fix state name abbreviation 2 years ago
tools Move some OpenSSL perl utility functions to OpenSSL::Util 2 years ago
util Replace CONFIG_NOWAIT env var with -w option 2 years ago
wycheproof@2196000605 add wycheproof submodule 2 years ago
.gitattributes Remove the external BoringSSL test 2 years ago
.gitignore Add wrap.pl to .gitignore 2 years ago
.gitmodules add wycheproof submodule 2 years ago
ACKNOWLEDGEMENTS.md Fix issues reported by markdownlint 3 years ago
AUTHORS.md Add some missing committers to the AUTHORS list 2 years ago
CHANGES.md Add documentation about the multilib postfix and libdir 2 years ago
CONTRIBUTING.md Drop Travis 2 years ago
Configure Replace CONFIG_NOWAIT env var with -w option 2 years ago
FAQ.md doc: introduce some minimalistic markdown without essential changes 3 years ago
HACKING.md Fix many MarkDown issues in {NOTES*,README*,HACKING,LICENSE}.md files 3 years ago
INSTALL.md Replace CONFIG_NOWAIT env var with -w option 2 years ago
LICENSE.txt Rename NOTES*, README*, VERSION, HACKING, LICENSE to .md or .txt 3 years ago
NEWS.md Prepare for 3.0 beta 3 2 years ago
NOTES-ANDROID.md Unify the markdown links to the NOTES and README files 2 years ago
NOTES-DJGPP.md Unify the markdown links to the NOTES and README files 2 years ago
NOTES-NONSTOP.md Document cross-compile considerations for NonStop x86 builds. 2 years ago
NOTES-PERL.md Fix issues found by md-nits 2 years ago
NOTES-UNIX.md Add a clarification to NOTES-UNIX.md 2 years ago
NOTES-VALGRIND.md Unify the markdown links to the NOTES and README files 2 years ago
NOTES-VMS.md Fix issues found by md-nits 2 years ago
NOTES-WINDOWS.md Fix issues found by md-nits 2 years ago
README-ENGINES.md README-ENGINES: fix the link to the provider API README 2 years ago
README-FIPS.md Add migration guide for 3.0 2 years ago
README-PROVIDERS.md Fix issues found by md-nits 2 years ago
README.md Unify the markdown links to the NOTES and README files 2 years ago
SUPPORT.md Fix SUPPORT.md for better readability 3 years ago
VERSION.dat Prepare for 3.0 beta 3 2 years ago
appveyor.yml Simplify AppVeyor configuration 2 years ago
build.info Building: Add necessary dependencies for linker scripts and .rc files 2 years ago
config config: Turn into a simple wrapper 3 years ago
config.com Update copyright year 3 years ago
configdata.pm.in configdata.pm: Allow extra arguments when --query is given. 2 years ago
e_os.h Remove I_CAN_LIVE_WITH_LNK4049 2 years ago


Welcome to the OpenSSL Project

openssl logo

github actions ci badge appveyor badge

OpenSSL is a robust, commercial-grade, full-featured Open Source Toolkit for the Transport Layer Security (TLS) protocol formerly known as the Secure Sockets Layer (SSL) protocol. The protocol implementation is based on a full-strength general purpose cryptographic library, which can also be used stand-alone.

OpenSSL is descended from the SSLeay library developed by Eric A. Young and Tim J. Hudson.

The official Home Page of the OpenSSL Project is www.openssl.org.

Table of Contents


The OpenSSL toolkit includes:

  • libssl an implementation of all TLS protocol versions up to TLSv1.3 (RFC 8446).

  • libcrypto a full-strength general purpose cryptographic library. It constitutes the basis of the TLS implementation, but can also be used independently.

  • openssl the OpenSSL command line tool, a swiss army knife for cryptographic tasks, testing and analyzing. It can be used for

    • creation of key parameters
    • creation of X.509 certificates, CSRs and CRLs
    • calculation of message digests
    • encryption and decryption
    • SSL/TLS client and server tests
    • handling of S/MIME signed or encrypted mail
    • and more...


For Production Use

Source code tarballs of the official releases can be downloaded from www.openssl.org/source. The OpenSSL project does not distribute the toolkit in binary form.

However, for a large variety of operating systems precompiled versions of the OpenSSL toolkit are available. In particular on Linux and other Unix operating systems it is normally recommended to link against the precompiled shared libraries provided by the distributor or vendor.

For Testing and Development

Although testing and development could in theory also be done using the source tarballs, having a local copy of the git repository with the entire project history gives you much more insight into the code base.

The official OpenSSL Git Repository is located at git.openssl.org. There is a GitHub mirror of the repository at github.com/openssl/openssl, which is updated automatically from the former on every commit.

A local copy of the Git Repository can be obtained by cloning it from the original OpenSSL repository using

git clone git://git.openssl.org/openssl.git

or from the GitHub mirror using

git clone https://github.com/openssl/openssl.git

If you intend to contribute to OpenSSL, either to fix bugs or contribute new features, you need to fork the OpenSSL repository openssl/openssl on GitHub and clone your public fork instead.

git clone https://github.com/yourname/openssl.git

This is necessary, because all development of OpenSSL nowadays is done via GitHub pull requests. For more details, see Contributing.

Build and Install

After obtaining the Source, have a look at the INSTALL file for detailed instructions about building and installing OpenSSL. For some platforms, the installation instructions are amended by a platform specific document.

Specific notes on upgrading to OpenSSL 3.0 from previous versions, as well as known issues are available on the OpenSSL 3.0 Wiki page.


Manual Pages

The manual pages for the master branch and all current stable releases are available online.


There is a Wiki at wiki.openssl.org which is currently not very active. It contains a lot of useful information, not all of which is up to date.


OpenSSL is licensed under the Apache License 2.0, which means that you are free to get and use it for commercial and non-commercial purposes as long as you fulfill its conditions.

See the LICENSE.txt file for more details.


There are various ways to get in touch. The correct channel depends on your requirement. see the SUPPORT file for more details.


If you are interested and willing to contribute to the OpenSSL project, please take a look at the CONTRIBUTING file.


A number of nations restrict the use or export of cryptography. If you are potentially subject to such restrictions you should seek legal advice before attempting to develop or distribute cryptographic code.


Copyright (c) 1998-2021 The OpenSSL Project

Copyright (c) 1995-1998 Eric A. Young, Tim J. Hudson

All rights reserved.