CAPEC-67
Alerte pour un CAPEC
Description
Informations
Execution Flow
1) Explore
[Identify target application] The adversary identifies a target application or program to perform the buffer overflow on. In this attack, adversaries look for applications that use syslog() incorrectly.
2) Experiment
[Find injection vector] The adversary identifies an injection vector to deliver the excessive content to the targeted application's buffer. For each user-controllable input that the adversary suspects is vulnerable to format string injection, attempt to inject formatting characters such as %n, %s, etc.. The goal is to manipulate the string creation using these formatting characters.
Technique
- Inject probe payload which contains formatting characters (%s, %d, %n, etc.) through input parameters.
3) Experiment
[Craft overflow content] The adversary crafts the content to be injected. If the intent is to simply cause the software to crash, the content need only consist of an excessive quantity of random data. If the intent is to leverage the overflow for execution of arbitrary code, the adversary will craft a set of content that not only overflows the targeted buffer but does so in such a way that the overwritten return address is replaced with one of the adversaries' choosing which points to code injected by the adversary.
Technique
- The formatting characters %s and %d are useful for observing memory and trying to print memory addresses. If an adversary has access to the log being written to they can observer this output and use it to help craft their attack.
- The formatting character %n is useful for adding extra data onto the buffer.
4) Exploit
[Overflow the buffer] Using the injection vector, the adversary supplies the program with the crafted format string injection, causing a buffer.
Prerequisites
The Syslog function is used without specifying a format string argument, allowing user input to be placed direct into the function call as a format string.Mitigations
The code should be reviewed for misuse of the Syslog function call. Manual or automated code review can be used. The reviewer needs to ensure that all format string functions are passed a static string which cannot be controlled by the user and that the proper number of arguments are always sent to that function as well. If at all possible, do not use the %n operator in format strings. The following code shows a correct usage of Syslog():
The following code shows a vulnerable usage of Syslog():
Related Weaknesses
| Weakness Name | |
|---|---|
| Buffer Copy without Checking Size of Input ('Classic Buffer Overflow') The product copies an input buffer to an output buffer without verifying that the size of the input buffer is less than the size of the output buffer, leading to a buffer overflow. |
|
| Use of Externally-Controlled Format String The product uses a function that accepts a format string as an argument, but the format string originates from an external source. |
|
| Improper Neutralization of Special Elements in Output Used by a Downstream Component ('Injection') The product constructs all or part of a command, data structure, or record using externally-influenced input from an upstream component, but it does not neutralize or incorrectly neutralizes special elements that could modify how it is parsed or interpreted when it is sent to a downstream component. |
|
| Improper Input Validation The product receives input or data, but it does not validate or incorrectly validates that the input has the properties that are required to process the data safely and correctly. |
|
| Integer Overflow to Buffer Overflow The product performs a calculation to determine how much memory to allocate, but an integer overflow can occur that causes less memory to be allocated than expected, leading to a buffer overflow. |
|
| Incorrect Comparison The product compares two entities in a security-relevant context, but the comparison is incorrect, which may lead to resultant weaknesses. |
References
REF-1
Exploiting Software: How to Break CodeG. Hoglund, G. McGraw.
REF-503
Exploiting Format String Vulnerabilitiesscut, team teso.
http://doc.bughunter.net/format-string/exploit-fs.html
REF-504
Auditing binaries for security vulnerabilitiesHalvar Flake.
http://www.blackhat.com/presentations/bh-europe-00/HalvarFlake/HalvarFlake.ppt
REF-505
Fortify Taxonomy of Vulnerabilitieshttps://vulncat.hpefod.com/en
REF-506
Syslog man pagehttp://www.rt.com/man/syslog.3.html
Submission
| Name | Organization | Date | Date Release |
|---|---|---|---|
| CAPEC Content Team | The MITRE Corporation |
Modifications
| Name | Organization | Date | Comment |
|---|---|---|---|
| CAPEC Content Team | The MITRE Corporation | Updated Related_Attack_Patterns | |
| CAPEC Content Team | The MITRE Corporation | Updated References | |
| CAPEC Content Team | The MITRE Corporation | Updated Execution_Flow | |
| CAPEC Content Team | The MITRE Corporation | Updated Taxonomy_Mappings | |
| CAPEC Content Team | The MITRE Corporation | Updated Description, Execution_Flow, Prerequisites, Related_Attack_Patterns | |
| CAPEC Content Team | The MITRE Corporation | Updated Example_Instances | |
| CAPEC Content Team | The MITRE Corporation | Updated Mitigations |
