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CWE-272 Individual Dictionary Definition (Draft 9)
Weakness ID
| Status: Incomplete 272 (Weakness Base) | | Description | Summary The elevated privilege level required to perform operations such as chroot() should be
dropped immediately after the operation is performed. | | Weakness Ordinality | Primary (Weakness exists independent of other weaknesses) | | Causal Nature | Explicit (This is an explicit weakness resulting from behavior of the developer) | | Common Consequences | Access control: An attacker may be able to access resources with the elevated
privilege that he should not have been able to access. This is particularly likely in
conjunction with another flaw -- e.g., a buffer overflow. | | Potential Mitigations | Very carefully manage the setting, management and handling of privileges. Explicitly
manage trust zones in the software. Follow the principle of least privilege when assigning access rights to entities in a
software system. Design: Ensure that appropriate compartmentalization is built into the system design
and that the compartmentalization serves to allow for and further reinforce privilege
separation functionality. Architects and designers should rely on the principle of least
privilege to decide when it is appropriate to use and to drop system privileges. | Demonstrative
Examples | C/C++ Example: setuid(0); //Do some important stuff
//setuid(old_uid); // Do some non privlidged stuff. Java Example: method() {
AccessController.doPrivileged(new PrivilegedAction() {
public Object run() { //Insert all code here }
});
}
Example 2: The following code calls chroot() to restrict the application to a subset
of the filesystem below APP_HOME in order to prevent an attacker from using the program to
gain unauthorized access to files located elsewhere. The code then opens a file specified
by the user and processes the contents of the file. ...
chroot(APP_HOME);
chdir("/");
FILE* data = fopen(argv[1], "r+");
... Constraining the process inside the application's home directory before opening any
files is a valuable security measure. However, the absence of a call to setuid() with some
non-zero value means the application is continuing to operate with unnecessary root
privileges. Any successful exploit carried out by an attacker against the application can
now result in a privilege escalation attack because any malicious operations will be
performed with the privileges of the superuser. If the application drops to the privilege
level of a non-root user, the potential for damage is substantially reduced. | | Context Notes | The failure to drop system privileges when it is reasonable to do so is not a
vulnerability by itself. It does, however, serve to significantly increase the Severity of other
vulnerabilities. According to the principle of least privilege, access should be allowed only when
it is absolutely necessary to the function of a given system, and only for the minimal necessary
amount of time. Any further allowance of privilege widens the window of time during which a
successful exploitation of the system will provide an attacker with that same privilege. If at all
possible, limit the allowance of system privilege to small, simple sections of code that may be
called atomically. When a program calls a privileged function, such as chroot(), it must first acquire
root privilege. As soon as the privileged operation has completed, the program should drop root
privilege and return to the privilege level of the invoking user. | | Relationships | | | Source Taxonomies | 7 Pernicious Kingdoms - Least Privilege Violation CLASP - Failure to drop privileges when reasonable | | Applicable Platforms | All | | Related Attack Patterns | | CAPEC-ID | Attack Pattern Name |
|---|
| 35 | Leverage Executable Code in Nonexecutable Files | | 17 | Accessing, Modifying or Executing Executable Files | | 76 | Manipulating Input to File System Calls |
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