How to Analyze Binary Files using 'ropper' (with examples)

Ropper is a powerful command-line tool designed for binary analysis, specifically focusing on finding Return Oriented Programming (ROP) gadgets in binary files. ROP gadgets are short instruction sequences ending in a return that are useful for understanding binary’s behavior in terms of security assessments or exploitation. It assists security researchers, reverse engineers, and exploit developers by making it easier to identify and manipulate these gadgets within binary executables.

Use case 1: Listing Gadgets in the Binary File

Code:

ropper --file path/to/binary

Motivation:

Listing all available ROP gadgets in a binary file is an essential first step for reverse engineers and security analysts when performing binary analysis. By understanding what gadgets are available, analysts can get insights into what actions a binary might take when executed. It can also help exploit developers in finding useful instruction sequences for constructing exploits or understanding vulnerabilities in the binary.

Explanation:

• ropper: This is the command-line tool being used.
• --file path/to/binary: This flag specifies the path to the binary file you want to analyze. Ropper uses this file to extract ROP gadgets.

Example Output:

[INFO] Load gadgets from section: LOAD
0x0001c2f9: pop eax; ret;
0x0001c2fa: pop ebx; ret;
0x0001c2fb: mov eax, ebx; ret;
...

The output shows a list of memory addresses followed by the corresponding assembly instructions, which are potential ROP gadgets.

Use case 2: Filtering Gadgets in the Binary File by a Regular Expression

Code:

ropper --file path/to/binary --search regex

Motivation:

Filtering gadgets using regular expressions allows users to hone in on specific instruction patterns that may be of interest for a particular analysis or exploitation goal. For instance, if an analyst is looking for gadgets related to loading immediate values into registers, they can efficiently narrow down their search results using this feature.

Explanation:

• ropper: The command utilized for the analysis.
• --file path/to/binary: Specifies the file to analyze.
• --search regex: This argument lets the user apply a regex search over the discovered gadgets. Replace “regex” with the actual regular expression pattern you wish to use.

Example Output:

[INFO] Search for gadgets: regex
0x0001c2f9: pop eax; ret;
...

The output is similar to the earlier case, but only shows gadgets that match the specified regular expression.

Use case 3: Listing Gadgets of Specified Type in the Binary File

Code:

ropper --file path/to/binary --type rop|job|sys|all

Motivation:

Different types of gadgets serve distinct purposes during reverse engineering or exploiting operations. By specifying the gadget type, users can focus on their specific needs—whether it’s generic ROP gadgets, syscall-related gadgets, or Job control gadgets for different operating systems.

Explanation:

• ropper: The main command.
• --file path/to/binary: Identifies the binary to work with.
• --type rop|job|sys|all: This specifies the type of gadgets to list. “rop” retrieves traditional Return Oriented Programming gadgets, “job” pertains to Job control gadgets, “sys” refers to syscall gadgets, and “all” covers all types of gadgets.

Example Output:

[INFO] Load rop gadgets from section: LOAD
0x0001c2f9: pop eax; ret;
...

Depending upon the type specified, it will list only those gadgets that fall under the chosen criteria.

Use case 4: Excluding Bad Byte Gadgets in the Binary File

Code:

ropper --file path/to/binary --badbytes byte_string

Motivation:

In certain binary exploitation tasks, specific bytes need to be avoided due to constraints or limitations (for example, null bytes in a string/function pointer in buffer overflow exploits). Ropper allows exclusion of such bytes from gadgets, ensuring the selected gadgets do not contain problematic byte sequences.

Explanation:

• ropper: Initiates the gadget search.
• --file path/to/binary: Points to the target binary.
• --badbytes byte_string: Specifies a string of bytes that should be excluded from the gadget selection. Replace “byte_string” with the actual bytes (in hexadecimal) you want to avoid.

Example Output:

[INFO] Exclude gadgets with bad bytes: 00
0x0001c2f9: pop eax; ret;
...

This highlighted listing contains gadgets omitting those instructions having any of the specified bad bytes.

Use case 5: Listing Gadgets Up to the Specified Instruction Count in the Binary File

Code:

ropper --file path/to/binary --inst-count count

Motivation:

Setting a maximum limit on instruction count allows users to focus on shorter, more manageable gadgets which are often more useful and easier to utilize in a single ROP chain. This can help in crafting tighter and more reliable ROP chains for exploitation or analysis.

Explanation:

• ropper: The core command used for finding gadgets.
• --file path/to/binary: Determines the target binary to be processed.
• --inst-count count: Establishes a threshold for the maximum number of instructions in the gadgets to be listed. Replace “count” with the desired number of instructions.

Example Output:

[INFO] List gadgets with instruction count maximum: 2
0x0001c2f9: pop eax; ret;
0x0001c2ff: add ebx, eax; ret;
...

Such output showcases gadgets specifically limited to three or fewer instructions.

Conclusion:

Ropper serves as an invaluable tool for anyone interested in reverse engineering or security analysis of binary files. By utilizing its diverse set of features and configurations, users can delve into the intricacies of binary execution. This guide illustrates various use cases of Ropper, showcasing how the command can be fine-tuned to uncover and analyze specific types of gadgets within binaries effectively.