ESA-2012-032: RSA BSAFE® Micro Edition Suite Security Update for BEAST (Browser Exploit Against SSL/TLS) attacks

[Security Alert <Security_Alert@xxxxxxx>]

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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 (MES) except 4.0.5 and 3.2.6, all 
platforms
 
Unaffected Products:
RSA BSAFE MES 4.0.5, 3.2.6
 
Summary: 
RSA BSAFE Micro Edition Suite contains updates designed to help 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.
 
In MES, the way to prevent the BEAST exploit is to introduce some unknown data 
into the encryption scheme, prior to the attackers inserted plain text data. 
This is done as follows:
 
1.     After the first encrypted record is sent, any plaintext to be encrypted 
is split into two blocks of plaintext. The blocks of data are then sent as two 
encrypted records; the first encrypted record contains the first byte of data 
and the second encrypted record 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 of plaintext.
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.
 
NOTE: In this release of MES, the mitigation for the BEAST exploit is enabled 
by default. No code changes are required to protect against it.
 
In special cases, if required, the BEAST exploit mitigation, either for an SSL 
context or SSL object can be disabled by calling 
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_NO_BEAST_MITIGATION 
identifier.
 
Note the following about first block splitting:
·         Splitting only occurs for negotiated cipher suites that use CBC mode.
·         Handshake packets are not split. Only application data packets are 
split.
·         Blocks of plaintext are split for each subsequent call to write data 
to the SSL connection after the first write is sent.
 
For more information about these functions and identifiers, see the RSA BSAFE 
MES API Reference Guide.
 
Obtaining Downloads: 
To request your upgrade of the software, please call your local support 
telephone number (contact phone numbers are available at 
http://www.emc.com/support/rsa/contact/phone-numbers.htm) for most expedient 
service. 

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.

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 More Information:
For more information about RSA products, visit the RSA web site at 
http://www.rsa.com.

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.emc.com/support/rsa/index.htm

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.emc.com/support/rsa/eops/index.htm

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.

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Sincerely,
RSA Customer Support
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