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A flaw was found in the Linux kernel's memory deduplication mechanism. The max page sharing of Kernel Samepage Merging (KSM), added in Linux kernel version 4.4.0-96.119, can create a side channel. When the attacker and the victim share the same host and the default setting of KSM is "max page sharing=256", it is possible for the attacker to time the unmap to merge with the victim's page. The unmapping time depends on whether it merges with the victim's page and additional physical pages are created beyond the KSM's "max page share". Through these operations, the attacker can leak the victim's page.
CVSS 3.1 Base Score 6.5. CVSS Attack Vector: adjacent_network. CVSS Attack Complexity: low. CVSS Vector: (CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N).
The following code checks validity of the supplied username and password and notifies the user of a successful or failed login.
}}print "Login Successful";print "Login Failed - incorrect password";print "Login Failed - unknown username";In the above code, there are different messages for when an incorrect username is supplied, versus when the username is correct but the password is wrong. This difference enables a potential attacker to understand the state of the login function, and could allow an attacker to discover a valid username by trying different values until the incorrect password message is returned. In essence, this makes it easier for an attacker to obtain half of the necessary authentication credentials.
While this type of information may be helpful to a user, it is also useful to a potential attacker. In the above example, the message for both failed cases should be the same, such as:
"Login Failed - incorrect username or password"Non-uniform processing time causes timing channel.
Suppose a hardware IP for implementing an encryption routine works fine per se, but the time taken to output the result of the encryption routine depends on a certain relationship between the input plaintext and the key (e.g., suppose, if the plaintext is similar to the key, it would run very fast).In the example above, an attacker can vary the inputs and, depending on the seen differences between processing times (different plaintexts take different time), can infer certain information about the key.
If the actual processing time was different for different plaintexts, artificial delays can be introduced to ensured all plaintexts take equal time to execute, even though the timing was internally different.The following Java code uses input from an HTTP request to create a file name. The programmer has not considered the possibility that an attacker could provide a file name such as "../../tomcat/conf/server.xml", which causes the application to delete one of its own configuration files.
rFile.delete();The following code uses input from the command line to determine which file to open and echo back to the user. If the program runs with privileges and malicious users can create soft links to the file, they can use the program to read the first part of any file on the system.
cout << s;The kind of resource the data affects indicates the kind of content that may be dangerous. For example, data containing special characters like period, slash, and backslash, are risky when used in methods that interact with the file system. (Resource injection, when it is related to file system resources, sometimes goes by the name "path manipulation.") Similarly, data that contains URLs and URIs is risky for functions that create remote connections.
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