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An issue was discovered in Xen through 4.14.x. Neither xenstore implementation does any permission checks when reporting a xenstore watch event. A guest administrator can watch the root xenstored node, which will cause notifications for every created, modified, and deleted key. A guest administrator can also use the special watches, which will cause a notification every time a domain is created and destroyed. Data may include: number, type, and domids of other VMs; existence and domids of driver domains; numbers of virtual interfaces, block devices, vcpus; existence of virtual framebuffers and their backend style (e.g., existence of VNC service); Xen VM UUIDs for other domains; timing information about domain creation and device setup; and some hints at the backend provisioning of VMs and their devices. The watch events do not contain values stored in xenstore, only key names. A guest administrator can observe non-sensitive domain and device lifecycle events relating to other guests. This information allows some insight into overall system configuration (including the number and general nature of other guests), and configuration of other guests (including the number and general nature of other guests' devices). This information might be commercially interesting or might make other attacks easier. There is not believed to be exposure of sensitive data. Specifically, there is no exposure of VNC passwords, port numbers, pathnames in host and guest filesystems, cryptographic keys, or within-guest data.
CVSS 3.1 Base Score 2.3. CVSS Attack Vector: local. CVSS Attack Complexity: low. CVSS Vector: (CVSS:3.1/AV:L/AC:L/PR:H/UI:N/S:U/C:L/I:N/A:N).
CVSS 2.0 Base Score 2.1. CVSS Attack Vector: local. CVSS Attack Complexity: low. CVSS Vector: (AV:L/AC:L/Au:N/C:P/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.ExploitPedia is constantly evolving. Sign up to receive a notification when we release additional functionality.
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