ESA-2012-032: RSA BSAFE(r) 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 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.


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EMC Product Security Response Center

Security_Alert@xxxxxxx

http://www.emc.com/contact-us/contact/product-security-response-center.html

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