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AUSCERT External Security Bulletin Redistribution
ESB-2012.0867
ESA-2012-032: RSA BSAFE® Micro Edition Suite Security Update
for BEAST (Browser Exploit Against SSL/TLS) attacks
12 September 2012
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AusCERT Security Bulletin Summary
---------------------------------
Product: RSA BSAFE Micro Edition Suite
Publisher: EMC
Operating System: Windows
Solaris
Red Hat
HP-UX
Impact/Access: Access Privileged Data -- Remote with User Interaction
Resolution: Patch/Upgrade
CVE Names: CVE-2011-3389
Reference: ESB-2012.0866
ESB-2012.0458
ESB-2012.0044
ESB-2011.1126
ESB-2011.1041
ESB-2011.1032
ESB-2011.0979
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ESA-2012-032: RSA BSAFE® Micro Edition Suite Security Update for BEAST
(Browser Exploit Against SSL/TLS) attacks
EMC Identifier: ESA-2012-032
CVE Identifier: CVE-2011-3389
Severity Rating: CVSS v2 Base Score: 4.3 (AV:N/AC:M/Au:N/C:P/I:N/A:N)
Affected Products:
All versions of RSA BSAFE Micro Edition Suite prior to 4.0, all platforms
Unaffected Products:
RSA BSAFE Micro Edition Suite 4.0 and higher
Summary:
RSA BSAFE Micro Edition Suite contains updates designed to prevent BEAST
attacks (CVE-2011-3389)
Details:
There is a known vulnerability in SSLv3 and TLS v1.0 to do with how the
Initialization Vector (IV) is generated. For symmetric key algorithms in CBC
mode, the IV for the first record is generated using keys and secrets set
during the SSL or TLS handshake. All subsequent records are encrypted using
the ciphertext block from the previous record as the IV. With symmetric key
encryption in CBC mode, plain text encrypted with the same IV and key
generates the same cipher text, which is why having a variable IV is
important.
The BEAST exploit uses this SSLv3 and TLS v1.0 vulnerability by allowing an
attacker to observe the last ciphertext block, which is the IV, then replace
this with an IV of their choice, inject some of their own plain text data,
and when this new IV is used to encrypt the data, the attacker can guess the
plain text data one byte at a time.
Recommendation:
The best way to help prevent this attack is to use TLS v1.1 or higher. The
vulnerability to do with IV generation was fixed in TLS v1.1 (released in
2006) so implementations using only TLS v1.1 or v1.2 are engineered to be
secure against the BEAST exploit. However, support for these higher level
protocols is limited to a smaller number of applications, so supporting only
TLS v1.1 or v1.2 might cause interoperability issues.
A second solution is to limit the negotiated cipher suites to exclude those
that do not require symmetric key algorithms in CBC mode. However, this
substantially restricts the number of cipher suites that can be negotiated.
That is, only cipher suites with NULL encryption or cipher suites with
streaming encryption algorithms (the RC4 algorithm) could be negotiated,
which might result in reduced security.
For customers who cannot or should not implement either of these two methods,
RSA BSAFE Micro Edition Suite 4.0 introduces a new feature called first block
splitting. First block splitting prevents the BEAST exploit by introducing
unknown data into the encryption scheme prior to the attackers inserted plain
text data. This is done as follows:
1. The first plain text block to be encrypted is split into two blocks.
The first block contains the first byte of the data, the second block contains
the rest.
2. A MAC is generated from the one byte of data, the MAC key, and an
increasing counter. This MAC is included in the first block.
3. The one byte of data, along with the MAC, is encrypted and becomes
the IV for the next block. Because the IV is now essentially random data, it
is impossible for an attacker to predict it and replace it with one of their
own.
To implement first block splitting in RSA BSAFE Micro Edition Suite 4.0,
either for an SSL context or SSL object, call R_SSL_CTX_set_options_by_type()
or R_SSL_set_options_by_type() respectively, with the SSL_OP_TYPE_SECURITY
option type and the SSL_OP_SPLIT_FIRST_FRAGMENT identifier.
For more information about these functions and identifiers, see the RSA BSAFE
Micro Edition Suite API Reference Guide.
Severity Rating:
For an explanation of Severity Ratings, refer to the Knowledge Base Article,
Security Advisories Severity Rating at
https://knowledge.rsasecurity.com/scolcms/knowledge.aspx?solution=a46604.
RSA recommends all customers take into account both the base score and any
relevant temporal and environmental scores which may impact the potential
severity associated with particular security vulnerability.
Obtaining Documentation:
To obtain RSA documentation, log on to RSA SecurCare Online at
https://knowledge.rsasecurity.com and click Products in the top navigation
menu. Select the specific product whose documentation you want to obtain.
Scroll to the section for the product version that you want and click the set
link.
Obtaining More Information:
For more information about RSA BSAFE, visit the RSA web site at
http://www.rsa.com/node.aspx?id=1204.
Getting Support and Service:
For customers with current maintenance contracts, contact your local RSA
Customer Support center with any additional questions regarding this RSA
SecurCare Note. For contact telephone numbers or e-mail addresses, log on to
RSA SecurCare Online at https://knowledge.rsasecurity.com, click Help &
Contact, and then click the Contact Us - Phone tab or the Contact Us - Email
tab.
General Customer Support Information:
http://www.rsa.com/node.aspx?id=1264
RSA SecurCare Online:
https://knowledge.rsasecurity.com
EOPS Policy:
RSA has a defined End of Primary Support policy associated with all major
versions. Please refer to the link below for additional details.
http://www.rsa.com/node.aspx?id=2575
SecurCare Online Security Advisories
RSA, The Security Division of EMC, distributes SCOL Security Advisories in
order to bring to the attention of users of the affected RSA products
important security information. RSA recommends that all users determine the
applicability of this information to their individual situations and take
appropriate action. The information set forth herein is provided "as is"
without warranty of any kind. RSA disclaim all warranties, either express or
implied, including the warranties of merchantability, fitness for a particular
purpose, title and non-infringement. In no event shall RSA or its suppliers be
liable for any damages whatsoever including direct, indirect, incidental,
consequential, loss of business profits or special damages, even if RSA or its
suppliers have been advised of the possibility of such damages. Some states do
not allow the exclusion or limitation of liability for consequential or
incidental damages so the foregoing limitation may not apply.
About RSA SecurCare Notes & Security Advisories Subscription
RSA SecurCare Notes & Security Advisories are targeted e-mail messages that
RSA sends you based on the RSA product family you currently use. If you'd like
to stop receiving RSA SecurCare Notes & Security Advisories, or if you'd like
to change which RSA product family Notes & Security Advisories you currently
receive, log on to RSA SecurCare Online at
https://knowledge.rsasecurity.com/scolcms/help.aspx?_v=view3. Following the
instructions on the page, remove the check mark next to the RSA product family
whose Notes & Security Advisories you no longer want to receive. Click the
Submit button to save your selection.
EMC Product Security Response Center
Security_Alert@EMC.COM
http://www.emc.com/contact-us/contact/product-security-response-center.html
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