TLS/SSL and crypto library
3ff98f5581
Improve handling of low entropy at start up from /dev/urandom by waiting for a read(2) call on /dev/random to succeed. Once one such call has succeeded, a shared memory segment is created and persisted as an indicator to other processes that /dev/urandom is properly seeded. This does not fully prevent against attacks weakening the entropy source. An attacker who has control of the machine early in its boot sequence could create the shared memory segment preventing detection of low entropy conditions. However, this is no worse than the current situation. An attacker would also be capable of removing the shared memory segment and causing seeding to reoccur resulting in a denial of service attack. This is partially mitigated by keeping the shared memory alive for the duration of the process's existence. Thus, an attacker would not only need to have called call shmctl(2) with the IPC_RMID command but the system must subsequently enter a state where no instances of libcrypto exist in any process. Even one long running process will prevent this attack. The System V shared memory calls used here go back at least as far as Linux kernel 2.0. Linux kernels 4.8 and later, don't have a reliable way to detect that /dev/urandom has been properly seeded, so a failure is raised for this case (i.e. the getentropy(2) call has already failed). Reviewed-by: Bernd Edlinger <bernd.edlinger@hotmail.de> (Merged from https://github.com/openssl/openssl/pull/9595) [manual merge] |
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OpenSSL 1.1.1d-dev
Copyright (c) 1998-2019 The OpenSSL Project
Copyright (c) 1995-1998 Eric A. Young, Tim J. Hudson
All rights reserved.
DESCRIPTION
-----------
The OpenSSL Project is a collaborative effort to develop a robust,
commercial-grade, fully featured, and Open Source toolkit implementing the
Transport Layer Security (TLS) protocols (including SSLv3) as well as a
full-strength general purpose cryptographic library.
OpenSSL is descended from the SSLeay library developed by Eric A. Young
and Tim J. Hudson. The OpenSSL toolkit is licensed under a dual-license (the
OpenSSL license plus the SSLeay license), which means that you are free to
get and use it for commercial and non-commercial purposes as long as you
fulfill the conditions of both licenses.
OVERVIEW
--------
The OpenSSL toolkit includes:
libssl (with platform specific naming):
Provides the client and server-side implementations for SSLv3 and TLS.
libcrypto (with platform specific naming):
Provides general cryptographic and X.509 support needed by SSL/TLS but
not logically part of it.
openssl:
A command line tool that 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...
INSTALLATION
------------
See the appropriate file:
INSTALL Linux, Unix, Windows, OpenVMS, ...
NOTES.* INSTALL addendums for different platforms
SUPPORT
-------
See the OpenSSL website www.openssl.org for details on how to obtain
commercial technical support. Free community support is available through the
openssl-users email list (see
https://www.openssl.org/community/mailinglists.html for further details).
If you have any problems with OpenSSL then please take the following steps
first:
- Download the latest version from the repository
to see if the problem has already been addressed
- Configure with no-asm
- Remove compiler optimization flags
If you wish to report a bug then please include the following information
and create an issue on GitHub:
- OpenSSL version: output of 'openssl version -a'
- Configuration data: output of 'perl configdata.pm --dump'
- OS Name, Version, Hardware platform
- Compiler Details (name, version)
- Application Details (name, version)
- Problem Description (steps that will reproduce the problem, if known)
- Stack Traceback (if the application dumps core)
Just because something doesn't work the way you expect does not mean it
is necessarily a bug in OpenSSL. Use the openssl-users email list for this type
of query.
HOW TO CONTRIBUTE TO OpenSSL
----------------------------
See CONTRIBUTING
LEGALITIES
----------
A number of nations restrict the use or export of cryptography. If you
are potentially subject to such restrictions you should seek competent
professional legal advice before attempting to develop or distribute
cryptographic code.