mirror of https://github.com/openssl/openssl.git
2139145b72
The drbg's lock must be held across calls to RAND_DRBG_generate() to prevent simultaneous modification of internal state. This was observed in practice with simultaneous SSL_new() calls attempting to seed the (separate) per-SSL RAND_DRBG instances from the global rand_drbg instance; this eventually led to simultaneous calls to ctr_BCC_update() attempting to increment drbg->bltmp_pos for their respective partial final block, violating the invariant that bltmp_pos < 16. The AES operations performed in ctr_BCC_blocks() makes the race window quite easy to trigger. A value of bltmp_pos greater than 16 induces catastrophic failure in ctr_BCC_final(), with subtraction overflowing and leading to an attempt to memset() to zero a very large range, which eventually reaches an unmapped page and segfaults. Provide the needed locking in get_entropy_from_parent(), as well as fixing a similar issue in RAND_priv_bytes(). There is also an unlocked call to RAND_DRBG_generate() in ssl_randbytes(), but the requisite serialization is already guaranteed by the requirements on the application's usage of SSL objects, and no further locking is needed for correct behavior. In that case, leave a comment noting the apparent discrepancy and the reason for its safety (at present). Reviewed-by: Paul Dale <paul.dale@oracle.com> Reviewed-by: Kurt Roeckx <kurt@roeckx.be> Reviewed-by: Rich Salz <rsalz@openssl.org> (Merged from https://github.com/openssl/openssl/pull/4328) |
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README
OpenSSL 1.1.1-dev
Copyright (c) 1998-2016 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 optimisation 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'
- Any "Configure" options that you selected during compilation of the
library if applicable (see INSTALL)
- 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.