ESA-2012-029: RSA BSAFE(r) SSL-C Multiple Vulnerabilities
- From: Security Alert <Security_Alert@xxxxxxx>
- Date: Tue, 11 Sep 2012 11:36:58 -0400
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ESA-2012-029: RSA BSAFE® SSL-C Multiple Vulnerabilities
EMC Identifier: ESA-2012-029
CVE Identifier: CVE-2011-3389, CVE-2012-2110, CVE-2012-2131
Severity Rating: See below for scores for individual issues
All versions of RSA BSAFE SSL-C prior to 2.8.6, all platforms
RSA BSAFE SSL-C 2.8.6
RSA BSAFE SSL-C 2.8.6 contains fixes designed to [prevent] BEAST attacks (CVE-2011-3389) and buffer overflow vulnerability (CVE-2012-2110/CVE-2012-2131).
This release includes fixes for the following vulnerabilities:
1.BEAST (Browser Exploit Against SSL/TLS) attack (CVE-2011-3389
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.
CVSSv2 Base Score: 4.3 (AV:N/AC:M/Au:N/C:P/I:N/A:N)
2.Buffer overflow vulnerability (CVE-2012-2110/CVE-2012-2131)
SSL-C contains code that does not properly interpret integer data, which could allow buffer overflow attacks using crafted DER (Distinguished Encoding Rules) data, such as in X.509 certificate or an RSA asymmetric key.
CVSSv2 Base Score: 7.5 (AV:N/AC:L/Au:N/C:P/I:P/A:P)
For BEAST (Browser Exploit Against SSL/TLS) attack:
The best way to help prevent this attack is to use TLS v1.1. The vulnerability to do with IV generation was fixed in TLS v1.1 (released in 2006) so implementations using only TLS v1.1 are engineered to be secure against the BEAST exploit. However, support for this higher level protocol is limited to a smaller number of applications, so supporting only TLS v1.1 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.
In RSA BSAFE SSL-C 2.8.6, the BEAST exploit is prevented by introducing some 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 manage this first block splitting in RSA BSAFE SSL-C 2.8.6, either for an SSL context or SSL object, call R_SSL_CTX_set_options() or R_SSL_set_options() respectively, with the SSL_OP_SPLIT_FIRST_FRAGMENT identifier, this option is enabled by default.
For more information about these functions and identifiers, see the RSA BSAFE SSL-C 2.8.6 API Reference Guide.
For Buffer Overflow vulnerability:
RSA strongly recommends that RSA BSAFE SSL-C customers upgrade to RSA BSAFE SSL-C 2.8.6 that contains upgrades designed to resolve this issue.
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.
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Obtaining More Information:
For more information about RSA BSAFE, visit the RSA web site at http://www.rsa.com/node.aspx?id=1204.
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General Customer Support Information:
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