What is Birthday Attack against TLS ciphers?
When CBC mode of encryption is used, there is simple birthday attack in which after 2n/2 blocks of data are encrypted with the same key, a collision between two ciphers blocks are expected. A collision in the output would mean that the input is same. This data combined with several conditions (discussed below) can be used to extract plain text of the encrypted data.
Summary of the Vulnerability:
Birthday attacks against TLS ciphers with 64bit block size vulnerability (Sweet32)
Legacy block ciphers having a block size of 64 bits are vulnerable to a practical collision attack when used in CBC mode. All versions of SSL/TLS protocol support cipher suites that use DES, 3DES, IDEA, or RC2 as the symmetric encryption cipher are affected.
Note: This CVE is patched at following versions
Disable and stop using DES, 3DES, IDEA, or RC2 ciphers.
Steps to Fix the Vulnerability:
We will be disabling the Vulnerability from the JRE level so that it is blocked on the Application level. The changes are only involved in java.security file and it will block the ciphers. Changing in the server.xml level shall not be needed once done on JRE level.
- Download the attached java.security file.
- Shut Down Adeptia Connect services.
- Go to ".\AdeptiaConnect\ConnectPortal\jre\lib\security" take backup of existing java.security file and use the one downloaded in Step1.
- Perform the same steps on the Connect Server side by going to ".\AdeptiaConnect\ConnectServer\jre\lib\security" and take backup of existing java.security file and use the one attached below.
- After making the above changes start the Connect Services.
Changes present in the java.security file
- Included 3DES_EDE_CBC algorithm in jdk.tls.disabledAlgorithms on line number 651.
- Removed 3DES_EDE_CBC algorithm from jdk.tls.legacyAlgorithms from line number 708.