A local copy of OpenSSL from GitHub
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Richard Levitte 2660b7cfba Rework how a build file (Makefile, ...) is produced
The memory footprint of how we produced the Makefile was quite...
important, because we have all the processing in one perl snippet, and
generate the details of the build file by appending to the "magic"
variable $OUT.  The result is that this variable gets to hold the
majority of the build file text, and depending on memory reallocation
strategies for strings, the heap may hold multiple (possibly not just
a few) copies of this string, almost all of them "freed" but still
taking up space.  This has resulted in memory exhaustion.

We therefore change strategy, and generate the build file in two
phases, where the first phase generates the full template using small
perl snippets for each detail, and the second phase processes this
template.  This is much kinder to process memory.

Reviewed-by: Tomas Mraz <tomas@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/15310)
2 years ago
.github fips: remove unnecessary commas to get CI working 2 years ago
Configurations Rework how a build file (Makefile, ...) is produced 2 years ago
VMS VMS documentation fixes 2 years ago
apps apps/cms.c: Simplify make_receipt_request() and load_content_info(() 2 years ago
crypto CMS_get0_SignerInfos(): Prevent spurious error on cms_get0_signed() failure 2 years ago
demos Update copyright year 2 years ago
dev Add make update-fips-checksums to release.sh script 2 years ago
doc Make SMIME_read_CMS_ex() and SMIME_read_ASN1_ex() support binary input 2 years ago
engines e_loader_attic: fix a use after free issue 2 years ago
external/perl Update the bundled external perl module Text-Template to version 1.56 4 years ago
fuzz Add OID for RPKI id-ct-signedChecklist 2 years ago
gost-engine@62583fb222 Updated gost-engine to latest commit from master branch 2 years ago
include Make SMIME_read_CMS_ex() and SMIME_read_ASN1_ex() support binary input 2 years ago
krb5@3195e18f66 Update krb5 module to latest release 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 keymgmt: fix coverity 1484886 unchecked return value 2 years ago
pyca-cryptography@62124e673a updated pyca/cryptography submodule version 2 years ago
test apps/cms.c: Make -sign and -verify handle binary input 2 years ago
tools Move some OpenSSL perl utility functions to OpenSSL::Util 2 years ago
util Move some OpenSSL perl utility functions to OpenSSL::Util 2 years ago
wycheproof@2196000605 add wycheproof submodule 2 years ago
.gitattributes Remove the external BoringSSL test 2 years ago
.gitignore Rework how a build file (Makefile, ...) is produced 2 years ago
.gitmodules add wycheproof submodule 2 years ago
.travis-apt-pin.preferences Fix travis clang-3.9 builds 6 years ago
.travis-create-release.sh Remove all 'make dist' artifacts 5 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
CONTRIBUTING.md Drop Travis 2 years ago
Configure Rework how a build file (Makefile, ...) is produced 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 Add --banner config option 2 years ago
LICENSE.txt Rename NOTES*, README*, VERSION, HACKING, LICENSE to .md or .txt 3 years ago
NEWS.md Add a CHANGES entry for fully pluggable groups 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 Rewrite the HPE NonStop Notes file in Markdown with more explanations. 3 years ago
NOTES-PERL.md Added Perl installation instructions to NOTES-PERL.md for HPE NonStop. 2 years ago
NOTES-UNIX.md Unify the markdown links to the NOTES and README files 2 years ago
NOTES-VALGRIND.md Unify the markdown links to the NOTES and README files 2 years ago
NOTES-VMS.md Reformat some NOTES and README files 2 years ago
NOTES-WINDOWS.md Support DLL builds + Fix C RTL variants 2 years ago
README-ENGINES.md README-ENGINES: fix the link to the provider API README 2 years ago
README-FIPS.md README-FIPS: document the installation of the FIPS provider 2 years ago
README-PROVIDERS.md Add a skeleton README-PROVIDERS file 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 alpha 17 2 years ago
appveyor.yml Simplify AppVeyor configuration 2 years ago
build.info Build resource 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 Rework how a build file (Makefile, ...) is produced 2 years ago
e_os.h Move ossl_sleep() to e_os.h and use it in apps 2 years ago


Welcome to the OpenSSL Project

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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.