This attack targets command-line utilities available in a number of
shells. An attacker can leverage a vulnerability found in a command-line
utility to escalate privilege to root.
Attack Execution Flow
Attacker identifies command utilities exposed by
the target host.
On the probing stage, the attacker interacts with
the command utility and observes the results of its
input. The attacker's goal is to uncover a buffer
oveflow in the command utility. For instance the
attacker may find that input data are not properly
validated.
The attacker finds a buffer overflow vulnerability
in the command utility and tries to exploit it. He
crafts malicious code and injects it using the
command utility. The attacker can at worst execute
remote code on the target host.
Attack Prerequisites
The target host exposes a command-line utility to the user.
The command-line utility exposed by the target host has a buffer overflow
vulnerability that can be exploited.
Typical Likelihood of Exploit
Likelihood: High
Methods of Attack
Injection
API Abuse
Examples-Instances
Description
A buffer overflow in the HPUX passwd command allows local users to
gain root privileges via a command-line option.
A buffer overflow in Solaris's getopt command (found in libc)
allows local users to gain root privileges via a long
argv[0].
Attacker Skills or Knowledge Required
Skill or Knowledge Level: Low
An attacker can simply overflow a buffer by inserting a long string
into an attacker-modifiable injection vector. The result can be a
DoS.
High : Exploiting a buffer overflow to inject malicious code into the
stack of a software system or even the heap can require a higher skill
level.
Probing Techniques
Description
The attacker can probe for services available on the target host. Many
services may expose a command utility. For instance Telnet is a service
which can be invoked through a command shell.
Solutions and Mitigations
Carefully review the service's implementation before making it available
to user. For instance you can use manual or automated code review to uncover
vulnerabilities such as buffer overflow.
Use a language or compiler that performs automatic bounds checking.
Use an abstraction library to abstract away risky APIs. Not a complete
solution.
Compiler-based canary mechanisms such as StackGuard, ProPolice and the
Microsoft Visual Studio /GS flag. Unless this provides automatic bounds
checking, it is not a complete solution.
Operational: Use OS-level preventative functionality. Not a complete
solution.
Apply the latest patches to your user exposed services. This may not be a
complete solution, specially against zero day attack.
Do not unnecessarily expose services.
Attack Motivation-Consequences
Scope
Technical Impact
Note
Confidentiality
Access_Control
Authorization
Gain privileges / assume
identity
Confidentiality
Integrity
Availability
Execute unauthorized code or
commands
Integrity
Modify memory
Availability
DoS: crash / exit /
restart
Confidentiality
Read memory
Injection Vector
The user supplied data.
Payload
The buffer overrun by the attacker.
Activation Zone
When the function returns control to the main program, it jumps to the return
address portion of the stack frame. Unfortunately that return address may have
been overwritten by the overflowed buffer and the address may contain a call to
a privileged command or to a malicious code.
Description
