Changes between 1.0.2f and 1.0.2g [1 Mar 2016]
* Disable weak ciphers in SSLv3 and up in default builds of OpenSSL.
Builds that are not configured with "enable-weak-ssl-ciphers" will not
provide any "EXPORT" or "LOW" strength ciphers.
[Viktor Dukhovni]
* Disable SSLv2 default build, default negotiation and weak ciphers. SSLv2
is by default disabled at build-time. Builds that are not configured with
"enable-ssl2" will not support SSLv2. Even if "enable-ssl2" is used,
users who want to negotiate SSLv2 via the version-flexible SSLv23_method()
will need to explicitly call either of:
SSL_CTX_clear_options(ctx, SSL_OP_NO_SSLv2);
or
SSL_clear_options(ssl, SSL_OP_NO_SSLv2);
as appropriate. Even if either of those is used, or the application
explicitly uses the version-specific SSLv2_method() or its client and
server variants, SSLv2 ciphers vulnerable to exhaustive search key
recovery have been removed. Specifically, the SSLv2 40-bit EXPORT
ciphers, and SSLv2 56-bit DES are no longer available.
(CVE-2016-0800)
[Viktor Dukhovni]
*) Fix a double-free in DSA code
A double free bug was discovered when OpenSSL parses malformed DSA private
keys and could lead to a DoS attack or memory corruption for applications
that receive DSA private keys from untrusted sources. This scenario is
considered rare.
This issue was reported to OpenSSL by Adam Langley(Google/BoringSSL) using
libFuzzer.
(CVE-2016-0705)
[Stephen Henson]
*) Disable SRP fake user seed to address a server memory leak.
Add a new method SRP_VBASE_get1_by_user that handles the seed properly.
SRP_VBASE_get_by_user had inconsistent memory management behaviour.
In order to fix an unavoidable memory leak, SRP_VBASE_get_by_user
was changed to ignore the "fake user" SRP seed, even if the seed
is configured.
Users should use SRP_VBASE_get1_by_user instead. Note that in
SRP_VBASE_get1_by_user, caller must free the returned value. Note
also that even though configuring the SRP seed attempts to hide
invalid usernames by continuing the handshake with fake
credentials, this behaviour is not constant time and no strong
guarantees are made that the handshake is indistinguishable from
that of a valid user.
(CVE-2016-0798)
[Emilia Käsper]
*) Fix BN_hex2bn/BN_dec2bn NULL pointer deref/heap corruption
In the BN_hex2bn function the number of hex digits is calculated using an
int value |i|. Later |bn_expand| is called with a value of |i * 4|. For
large values of |i| this can result in |bn_expand| not allocating any
memory because |i * 4| is negative. This can leave the internal BIGNUM data
field as NULL leading to a subsequent NULL ptr deref. For very large values
of |i|, the calculation |i * 4| could be a positive value smaller than |i|.
In this case memory is allocated to the internal BIGNUM data field, but it
is insufficiently sized leading to heap corruption. A similar issue exists
in BN_dec2bn. This could have security consequences if BN_hex2bn/BN_dec2bn
is ever called by user applications with very large untrusted hex/dec data.
This is anticipated to be a rare occurrence.
All OpenSSL internal usage of these functions use data that is not expected
to be untrusted, e.g. config file data or application command line
arguments. If user developed applications generate config file data based
on untrusted data then it is possible that this could also lead to security
consequences. This is also anticipated to be rare.
This issue was reported to OpenSSL by Guido Vranken.
(CVE-2016-0797)
[Matt Caswell]
*) Fix memory issues in BIO_*printf functions
The internal |fmtstr| function used in processing a "%s" format string in
the BIO_*printf functions could overflow while calculating the length of a
string and cause an OOB read when printing very long strings.
Additionally the internal |doapr_outch| function can attempt to write to an
OOB memory location (at an offset from the NULL pointer) in the event of a
memory allocation failure. In 1.0.2 and below this could be caused where
the size of a buffer to be allocated is greater than INT_MAX. E.g. this
could be in processing a very long "%s" format string. Memory leaks can
also occur.
The first issue may mask the second issue dependent on compiler behaviour.
These problems could enable attacks where large amounts of untrusted data
is passed to the BIO_*printf functions. If applications use these functions
in this way then they could be vulnerable. OpenSSL itself uses these
functions when printing out human-readable dumps of ASN.1 data. Therefore
applications that print this data could be vulnerable if the data is from
untrusted sources. OpenSSL command line applications could also be
vulnerable where they print out ASN.1 data, or if untrusted data is passed
as command line arguments.
Libssl is not considered directly vulnerable. Additionally certificates etc
received via remote connections via libssl are also unlikely to be able to
trigger these issues because of message size limits enforced within libssl.
This issue was reported to OpenSSL Guido Vranken.
(CVE-2016-0799)
[Matt Caswell]
*) Side channel attack on modular exponentiation
A side-channel attack was found which makes use of cache-bank conflicts on
the Intel Sandy-Bridge microarchitecture which could lead to the recovery
of RSA keys. The ability to exploit this issue is limited as it relies on
an attacker who has control of code in a thread running on the same
hyper-threaded core as the victim thread which is performing decryptions.
This issue was reported to OpenSSL by Yuval Yarom, The University of
Adelaide and NICTA, Daniel Genkin, Technion and Tel Aviv University, and
Nadia Heninger, University of Pennsylvania with more information at
http://cachebleed.info.
(CVE-2016-0702)
[Andy Polyakov]
*) Change the req app to generate a 2048-bit RSA/DSA key by default,
if no keysize is specified with default_bits. This fixes an
omission in an earlier change that changed all RSA/DSA key generation
apps to use 2048 bits by default.
[Emilia Käsper]
a2c5c420a7