CAPEC-37 - Lifting Data Embedded in Client Distributions

An attacker can resort to stealing data embedded in client distributions or client code in order to gain certain information. This information can reveal confidential contents, such as account numbers, or can be used as an intermediate step in a larger attack (such as by stealing keys/credentials).






  • Attack Methods 1
  • Analysis
  • Purposes 2
  • Reconnaissance
  • Exploitation
  • Sec Principles 2
  • Reluctance to Trust
  • Never Assuming that Your Secrets Are Safe
  • Scopes 3
  • Read application data
  • Confidentiality
  • Modify application data
  • Integrity
  • Gain privileges / assume identity
  • Authorization
  • Access_Control
  • Confidentiality

Medium level: The attacker must possess knowledge of client code structure as well as ability to reverse-engineer or decompile it or probe it in other ways. This knowledge is specific to the technology and language used for the client distribution

In order to feasibly execute this class of attacks, some valuable data must be present in client software.

Additionally, this information must be unprotected, or protected in a flawed fashion, or through a mechanism that fails to resist reverse engineering, statistical, cryptanalytic, or other attack.

The attacker must possess access to the client machine or code being exploited. Such access, for this set of attacks, will likely be physical. The attacker will make use of reverse engineering technologies, perhaps for data or to extract functionality from the binary. Such tool use may be as simple as "Strings" or a hex editor. Removing functionality may require the use of only a hex editor, or may require aspects of the toolchain used to construct the application: for instance the Adobe Flash development environment. Attacks of this nature do not require network access or undue CPU, memory, or other hardware-based resources.

Attackers may confine (and succeed with) probing as simple as deleting a cache or data file, or less drastically twiddling its bits and then testing the mutation's effect on an executing client.

At the other extreme, attackers capable of reverse engineering client code will have the ability to remove functionality or identify the whereabouts of sensitive data through white box analysis, such as review of reverse-engineered code.

Never Use Unvalidated Input as Part of a Directive to any Internal Component

Treat the Entire Inherited Process Context as Unvalidated Input

Use Well-Known Cryptography Appropriately and Correctly

Step 1 - Identify Target

Attacker identifies client components to extract information from. These may be binary executables, class files, shared libraries (e.g., DLLs), or other machine code..

Tecnique ID: 1 - Environment(s) env-Local env-Embedded env-ClientServer env-Peer2Peer

Binary file extraction. The attacker extracts binary files from zips, jars, wars, PDFs or other composite formats.

Tecnique ID: 2 - Environment(s) env-Local env-Embedded env-ClientServer env-Peer2Peer

Package listing. The attacker uses a package manifest provided with the software installer, or the filesystem itself, to identify component files suitable for attack.

Indicator ID: 1 - Environment(s) env-Local env-Embedded env-ClientServer env-Peer2Peer

Type: Positive

Proprietary or sensitive data is stored in a location ultimately distributed to end users.

Indicator ID: 2 - Environment(s) env-Web env-ClientServer env-Peer2Peer env-CommProtocol

Type: Negative

Access to binary code is not realistic. For example, in a client-server environment, binary code on the server is presumed to be inscrutable to an attacker unless another vulnerability exposes it.

Security Control ID: 1

Type: Preventative

Obfuscation can make the observation and reverse engineering more difficult. It is only capable of delaying an attacker, however, not preventing a sufficiently motivated and resourced one.

Outcome ID: 1

Type: Success

The attacker identifies one or more files or data in the software to attack.

Step 1 - Apply mining techniques

The attacker then uses a variety of techniques, such as sniffing, reverse-engineering, and cryptanalysis to extract the information of interest..

Tecnique ID: 1 - Environment(s) env-Local env-Embedded env-ClientServer env-Peer2Peer

API Profiling. The attacker monitors the software's use of registry keys or other operating system-provided storage locations that can contain sensitive information.

Tecnique ID: 2 - Environment(s) env-Local env-Embedded

Execution in simulator. The attacker physically removes mass storage from the system and explores it using a simulator, external system, or other debugging harness.

Tecnique ID: 3 - Environment(s) env-Local env-Embedded env-ClientServer env-Peer2Peer

Cryptanalysis. The attacker performs cryptanalysis to identify data in the client component which may be cryptographically significant. (Key material frequently stands out as very high entropy data when compared to other mundane data). Given cryptographically significant data, other analyses are performed (e.g., length, internal structure, etc.) to determine potential algorithms (RSA, ECC, AES, etc.). This process proceeds until the attacker reaches a conclusion about the significance and use of the data.

Tecnique ID: 4 - Environment(s) env-All

Common decoding methods. The attacker applies methods to decode such encodings and compressions as Base64, unzip, unrar, RLE decoding, gzip decompression and so on.

Tecnique ID: 5 - Environment(s) env-All

Common data typing. The attacker looks for common file signatures for well-known file types (JPEG, TIFF, ASN.1, LDIF, etc.). If the signatures match, he attempts decoding in that format.

Indicator ID: 1 - Environment(s) env-Local env-Embedded env-ClientServer env-Peer2Peer

Type: Positive

Well known data types are used and embedded inside the client-accessible code.

Indicator ID: 2 - Environment(s) env-Local env-Embedded env-ClientServer env-Peer2Peer

Type: Inconclusive

Proprietary data encodings are used. Although this incrementally increases the difficulty for an attacker to decode the data, it provides no better protection than well-known data types. Since few software developers are trained in obfuscation and cryptography, most proprietary encodings add little security value.

Security Control ID: 1

Type: Corrective

The software can contain an update mechanism, key management mechanism, or other means of updating proprietary data. Although this can react to a single breach, it is not an effective continuing solution. Many software manufacturers are lured into a repeated update cycle (c.f., satellite TV providers, iPhone) as adversaries break proprietary data protection schemes. Planning to issue corrections is a poor long-term strategy, but it can be an effective stopgap measure until a design-level correction can be made.

Outcome ID: 1

Type: Success

The attacker extracts useful information.

No sensitive or confidential information must be stored in client distributions. This includes content such as passwords or encryption keys. In cases where this is necessary, avoid storing any such information in plaintext

All information arriving from a client must be validated before use.