Full Report
Note: Re-write/Re-upload due to dead linksThis write up are my thoughts and steps to statically analyze a given unknown binary. I want to understand the binary to a point where I can freely write about it. So here it is. I'm always open for you pointing
Analysis Summary
This summary is based on a static analysis of an unknown binary, described as a "Poly Bomb" challenge with three phases. The provided text details the analytical steps taken to understand the binary's functionality, particularly focusing on how it processes user input for each phase.
# Tool/Technique: Poly Bomb Binary Analysis (Unknown Malware/Tool)
## Overview
This analysis details the static reverse engineering process performed on an unknown binary, referred to as a "Poly Bomb" challenge, which requires solving three distinct phases by providing specific input to unlock keys. The analysis focuses on deciphering the input validation and transformation logic for each phase.
## Technical Details
- Type: Unknown Executable (CTF/Challenge Binary)
- Platform: Likely Linux (indicated by `chmod +x`)
- Capabilities: Input validation and transformation across three phases.
- First Seen: Analysis performed on the provided Base64 encoded content (date not specified).
## MITRE ATT&CK Mapping
Since this is a static analysis of a challenge binary and not observed malicious activity, direct tactical mappings are speculative, but the binary exhibits characteristics of input validation and execution flow control typical in self-extracting or protected binaries.
- **TA0001 - Initial Access** (If deployed maliciously)
- **TA0004 - Privilege Escalation** (Indirectly, unlocking subsequent steps)
- T1059.004 - Command and Scripting Interpreter: Unix Shell
- **TA0005 - Defense Evasion** (Input validation mechanisms can mimic this)
- T1027 - Obfuscated Files or Information (The core challenge relies on reversing obfuscated logic)
## Functionality
### Core Capabilities (Phase Descriptions)
The binary presents three phases of challenge, each requiring specific input handling:
1. **Phase One:** Involves integer division operations where the result (`eax` = quotient, `edx` = remainder) is manipulated with an input byte (`ecx`). This suggests a byte-by-byte transformation or substitution cipher applied to the input stream over 8 loop iterations.
2. **Phase Two:** Mentioned only in passing ("Wow you solved phase two???"), suggesting a distinct challenge succeeding Phase One.
3. **Phase Three:** Requires the input to be a palindrome (comparing 1st element to $N^{th}$, 2nd to $(N-1)^{th}$, etc., until the middle), must have a length $>4$, and an **uneven number** of characters. Processing involves operations on **lowercase ASCII characters**.
### Advanced Features
The analysis uncovered low-level arithmetic operations used for obfuscating the expected input:
* **Division/Remainder Use:** Utilizing `edx % ecx` logic (remainder after division) incorporated with input bytes to generate transformed bytes.
* **Comparative Logic:** Phase 3 requires specific structural symmetry (palindrome) and length constraints for successful execution flow continuation.
## Indicators of Compromise
*Note: As this is a self-contained analytical challenge, IoCs relate to the potential execution environment, not external infrastructure.*
- File Hashes: Not calculated during this analysis, but the content is derived from: `H4sIADY2B18AA+1af3BURZ7v+REYQkgCRgWJ8u4cPFzCM+GHhAiXBGaAIDNESPyBro/JzEtmjsnM...`
- File Names: `anothah_one.bin` (derived from Base64 file name context).
- Registry Keys: N/A (Likely Linux binary).
- Network Indicators: None observed in the provided analysis excerpt.
- Behavioral Indicators: Attempts to read standard input (`stdin`) repeatedly, performs integer arithmetic on input, checks input symmetry (palindrome check).
## Associated Threat Actors
None associated. This binary appears to be related to a Capture The Flag (CTF) challenge or educational exercise designed for binary analysis practice.
## Detection Methods
Detection relies on recognizing the specific arithmetic patterns or the success/failure strings printed to STDOUT.
- Signature-based detection: Detecting unique strings like "Welcome to the Poly Bomb," "H0Tf00D: eax = eax / edx = edx %," and the exit condition strings.
- Behavioral detection: Monitoring execution flow that relies heavily on iterative mathematical operations combined with user input to modify internal state without obvious external calls (other than standard I/O).
## Mitigation Strategies
N/A for this specific exercise, as the goal is to solve the challenge. In a real-world scenario involving unknown binaries:
- Prevention measures: Execute unknown binaries only in isolated environments (sandboxes or dedicated VMs).
- Hardening recommendations: Strict control over execution permissions and monitoring processes interacting with standard input.
## Related Tools/Techniques
The analysis method employed is standard static reverse engineering:
- Disassembly/Decompilation (Implied, based on reference to offsets like `0x080488f0` and register analysis: `eax`, `edx`, `ecx`).
- String extraction (Identifying instructional text like "Good Luck...").