||OpenSSL 1.0.2 supports SSLv2. If a client attempts to negotiate SSLv2 with a server that is configured to support both SSLv2 and more recent SSL and TLS versions then a check is made for a version rollback attack when unpadding an RSA signature. Clients that support SSL or TLS versions greater than SSLv2 are supposed to use a special form of padding. A server that supports greater than SSLv2 is supposed to reject connection attempts from a client where this special form of padding is present, because this indicates that a version rollback has occurred (i.e. both client and server support greater than SSLv2, and yet this is the version that is being requested). The implementation of this padding check inverted the logic so that the connection attempt is accepted if the padding is present, and rejected if it is absent. This means that such as server will accept a connection if a version rollback attack has occurred. Further the server will erroneously reject a connection if a normal SSLv2 connection attempt is made. Only OpenSSL 1.0.2 servers from version 1.0.2s to 1.0.2x are affected by this issue. In order to be vulnerable a 1.0.2 server must: 1) have configured SSLv2 support at compile time (this is off by default), 2) have configured SSLv2 support at runtime (this is off by default), 3) have configured SSLv2 ciphersuites (these are not in the default ciphersuite list) OpenSSL 1.1.1 does not have SSLv2 support and therefore is not vulnerable to this issue. The underlying error is in the implementation of the RSA_padding_check_SSLv23() function. This also affects the RSA_SSLV23_PADDING padding mode used by various other functions. Although 1.1.1 does not support SSLv2 the RSA_padding_check_SSLv23() function still exists, as does the RSA_SSLV23_PADDING padding mode. Applications that directly call that function or use that padding mode will encounter this issue. However since there is no support for the SSLv2 protocol in 1.1.1 this is considered a bug and not a security issue in that version. OpenSSL 1.0.2 is out of support and no longer receiving public updates. Premium support customers of OpenSSL 1.0.2 should upgrade to 1.0.2y. Other users should upgrade to 1.1.1j. Fixed in OpenSSL 1.0.2y (Affected 1.0.2s-1.0.2x).
In this attack, some asset (information, functionality, identity, etc.) is protected by a finite secret value. The attacker attempts to gain access to this asset by using trial-and-error to exhaustively explore all the possible secret values in the hope of finding the secret (or a value that is functionally equivalent) that will unlock the asset. Examples of secrets can include, but are not limited to, passwords, encryption keys, database lookup keys, and initial values to one-way functions. The key factor in this attack is the attackers' ability to explore the possible secret space rapidly. This, in turn, is a function of the size of the secret space and the computational power the attacker is able to bring to bear on the problem. If the attacker has modest resources and the secret space is large, the challenge facing the attacker is intractable. While the defender cannot control the resources available to an attacker, they can control the size of the secret space. Creating a large secret space involves selecting one's secret from as large a field of equally likely alternative secrets as possible and ensuring that an attacker is unable to reduce the size of this field using available clues or cryptanalysis. Doing this is more difficult than it sounds since elimination of patterns (which, in turn, would provide an attacker clues that would help them reduce the space of potential secrets) is difficult to do using deterministic machines, such as computers. Assuming a finite secret space, a brute force attack will eventually succeed. The defender must rely on making sure that the time and resources necessary to do so will exceed the value of the information. For example, a secret space that will likely take hundreds of years to explore is likely safe from raw-brute force attacks.
An adversary engages in activities to decipher and/or decode protocol information for a network or application communication protocol used for transmitting information between interconnected nodes or systems on a packet-switched data network. While this type of analysis involves the analysis of a networking protocol inherently, it does not require the presence of an actual or physical network. Although certain techniques for protocol analysis benefit from manipulating live 'on-the-wire' interactions between communicating components, static or dynamic analysis techniques applied to executables as well as to device drivers, such as network interface drivers, can also be used to reveal the function and characteristics of a communication protocol implementation. Depending upon the methods used the process may involve observing, interacting, and modifying actual communications occurring between hosts. The goal of protocol analysis is to derive the data transmission syntax, as well as to extract the meaningful content, including packet or content delimiters used by the protocol. This type of analysis is often performed on closed-specification protocols, or proprietary protocols, but is also useful for analyzing publicly available specifications to determine how particular implementations deviate from published specifications.
Encryption Brute Forcing
An attacker, armed with the cipher text and the encryption algorithm used, performs an exhaustive (brute force) search on the key space to determine the key that decrypts the cipher text to obtain the plaintext.