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FIPS 186-4 section 5 "The RSA Digital Signature Algorithm", subsection 5.5 "PKCS #1" says: "For RSASSA-PSS […] the length (in bytes) of the salt (sLen) shall satisfy 0 <= sLen <= hLen, where hLen is the length of the hash function output block (in bytes)." Introduce a new option RSA_PSS_SALTLEN_AUTO_DIGEST_MAX and make it the default. The new value will behave like RSA_PSS_SALTLEN_AUTO, but will not use more than the digest length when signing, so that FIPS 186-4 is not violated. This value has two advantages when compared with RSA_PSS_SALTLEN_DIGEST: (1) It will continue to do auto-detection when verifying signatures for maximum compatibility, where RSA_PSS_SALTLEN_DIGEST would fail for other digest sizes. (2) It will work for combinations where the maximum salt length is smaller than the digest size, which typically happens with large digest sizes (e.g., SHA-512) and small RSA keys. J.-S. Coron shows in "Optimal Security Proofs for PSS and Other Signature Schemes. Advances in Cryptology – Eurocrypt 2002, volume 2332 of Lecture Notes in Computer Science, pp. 272 – 287. Springer Verlag, 2002." that longer salts than the output size of modern hash functions do not increase security: "For example,for an application in which at most one billion signatures will be generated, k0 = 30 bits of random salt are actually sufficient to guarantee the same level of security as RSA, and taking a larger salt does not increase the security level." Signed-off-by: Clemens Lang <cllang@redhat.com> Reviewed-by: Dmitry Belyavskiy <beldmit@gmail.com> Reviewed-by: Tomas Mraz <tomas@openssl.org> (Merged from https://github.com/openssl/openssl/pull/19724) |
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Welcome to the OpenSSL Project
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
Overview
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...
Download
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.
- Notes for UNIX-like platforms
- Notes for Android platforms
- Notes for Windows platforms
- Notes for the DOS platform with DJGPP
- Notes for the OpenVMS platform
- Notes on Perl
- Notes on Valgrind
Specific notes on upgrading to OpenSSL 3.0 from previous versions can be found in the migration_guide(7ossl) manual page.
Documentation
Manual Pages
The manual pages for the master branch and all current stable releases are available online.
Wiki
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.
License
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.
Support
There are various ways to get in touch. The correct channel depends on your requirement. See the SUPPORT file for more details.
Contributing
If you are interested and willing to contribute to the OpenSSL project, please take a look at the CONTRIBUTING file.
Legalities
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
Copyright (c) 1998-2022 The OpenSSL Project
Copyright (c) 1995-1998 Eric A. Young, Tim J. Hudson
All rights reserved.