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Study the following exploit code taken from a Linux machine and answer the questions below:
echo ''ingreslock stream tcp nowait root /bin/sh sh --I" > /tmp/x;
/usr/sbin/inetd --s /tmp/x;
sleep 10;
/bin/ rm --f /tmp/x AAAA...AAA
In the above exploit code, the command ''/bin/sh sh --I" is given.
What is the purpose, and why is 'sh' shown twice?
Answer : A
What's going on in the above question is the attacker is trying to write to the unix filed /tm/x (his inetd.conf replacement config) -- he is attempting to add a service called ingresslock (which doesnt exist), which is 'apparently' suppose to spawn a shell the given port specified by /etc/services for the service 'ingresslock', ingresslock is a non-existant service, and if an attempt were made to respawn inetd, the service would error out on that line. (he would have to add the service to /etc/services to suppress the error). Now the question is asking about /bin/sh sh -i which produces an error that should read 'sh: /bin/sh: cannot execute binary file', the -i option places the shell in interactive mode and cannot be used to respawn itself.
The programmers on your team are analyzing the free, open source software being used to run FTP services on a server. They notice that there is an excessive number of fgets() and gets() on the source code. These C++ functions do not check bounds.What kind of attack is this program susceptible to?
Answer : A
C users must avoid using dangerous functions that do not check bounds unless they've ensured that the bounds will never get exceeded. A buffer overflow occurs when you write a set of values (usually a string of characters) into a fixed length buffer and write at least one value outside that buffer's boundaries (usually past its end). A buffer overflow can occur when reading input from the user into a buffer, but it can also occur during other kinds of processing in a program.
Symmetric encryption algorithms are known to be fast but present great challenges on the key management side. Asymmetric encryption algorithms are slow but allow communication with a remote host without having to transfer a key out of band or in person. If we combine the strength of both crypto systems where we use the symmetric algorithm to encrypt the bulk of the data and then use the asymmetric encryption system to encrypt the symmetric key, what would this type of usage be known as?
Answer : C
Because of the complexity of the underlying problems, most public-key algorithms involve operations such as modular multiplication and exponentiation, which are much more computationally expensive than the techniques used in most block ciphers, especially with typical key sizes. As a result, public-key cryptosystems are commonly 'hybrid' systems, in which a fast symmetric-key encryption algorithm is used for the message itself, while the relevant symmetric key is sent with the message, but encrypted using a public-key algorithm. Similarly, hybrid signature schemes are often used, in which a cryptographic hash function is computed, and only the resulting hash is digitally signed.
Steven the hacker realizes that the network administrator of XYZ is using syskey to protect organization resources in the Windows 2000 Server. Syskey independently encrypts the hashes so that physical access to the server, tapes, or ERDs is only first step to cracking the passwords. Steven must break through the encryption used by syskey before he can attempt to brute force dictionary attacks on the hashes. Steven runs a program called ''SysCracker'' targeting the Windows 2000 Server machine in attempting to crack the hash used by Syskey. He needs to configure the encryption level before he can launch attach. How many bits does Syskey use for encryption?
Answer : D
SYSKEY is a utility that encrypts the hashed password information in a SAM database using a 128-bit encryption key.
In the context of using PKI, when Sven wishes to send a secret message to Bob, he looks up Bob's public key in a directory, uses it to encrypt the message before sending it off. Bob then uses his private key to decrypt the message and reads it. No one listening on can decrypt the message. Anyone can send an encrypted message to Bob but only Bob can read it. Thus, although many people may know Bob's public key and use it to verify Bob's signature, they cannot discover Bob's private key and use it to forge digital signatures. What does this principle refer to?
Answer : D
PKI uses asymmetric key pair encryption. One key of the pair is the only way to decrypt data encrypted with the other.
