Analyzing Golang Malware With Ghidra

Go binaries embed rich metadata in the pclntab (PC Line Table) structure, which maps program counters to function names, source files, and line numbers. Even stripped binaries retain this metadata. The moduledata structure contains pointers to type information, itabs (interface tables), and the pclntab itself. Go strings are stored as a pointer-length pair rather than null-terminated C strings.

Function Recovery in Stripped Binaries

Despite stripping symbol tables, Go binaries retain function names within the pclntab. However, obfuscation tools like garble rename functions to random strings. GoResolver addresses this by computing control-flow graph signatures of obfuscated functions and matching them against a database of known Go standard library and third-party package functions.

Crate/Dependency Extraction

Go's dependency management embeds module paths and version strings in the binary. Extracting these reveals the malware's third-party dependencies (HTTP libraries, encryption packages, C2 frameworks), which provides insight into capabilities without full reverse engineering.

Practical Steps

Step 1: Initial Binary Analysis

#!/usr/bin/env python3
"""Analyze Go binary metadata for malware analysis."""
import struct
import sys
import re


def find_go_build_info(data):
    """Extract Go build information from binary."""
    # Go buildinfo magic: \xff Go buildinf:
    magic = b'\xff Go buildinf:'
    offset = data.find(magic)
    if offset == -1:
        return None

    print(f"[+] Go build info at offset 0x{offset:x}")

    # Extract Go version string nearby
    go_version = re.search(rb'go\d+\.\d+(?:\.\d+)?', data[offset:offset+256])
    if go_version:
        print(f"  Go Version: {go_version.group().decode()}")

    return offset


def find_pclntab(data):
    """Locate the pclntab (PC Line Table) structure."""
    # pclntab magic bytes vary by Go version
    magics = {
        b'\xfb\xff\xff\xff\x00\x00': "Go 1.2-1.15",
        b'\xfa\xff\xff\xff\x00\x00': "Go 1.16-1.17",
        b'\xf1\xff\xff\xff\x00\x00': "Go 1.18-1.19",
        b'\xf0\xff\xff\xff\x00\x00': "Go 1.20+",
    }

    for magic, version in magics.items():
        offset = data.find(magic)
        if offset != -1:
            print(f"[+] pclntab found at 0x{offset:x} ({version})")
            return offset, version

    return None, None


def extract_function_names(data, pclntab_offset):
    """Extract function names from pclntab."""
    if pclntab_offset is None:
        return []

    functions = []
    # Function name strings follow specific patterns
    func_pattern = re.compile(
        rb'(?:main|runtime|fmt|net|os|crypto|encoding|io|sync|'
        rb'syscall|reflect|strings|bytes|path|time|math|sort|'
        rb'github\.com|golang\.org)[/\.][\w/.]+',
    )

    for match in func_pattern.finditer(data):
        name = match.group().decode('utf-8', errors='replace')
        if len(name) > 4 and len(name) < 200:
            functions.append(name)

    return sorted(set(functions))


def extract_go_strings(data):
    """Extract Go-style strings (pointer+length pairs)."""
    # Go strings are not null-terminated; extract readable sequences
    strings = []
    ascii_pattern = re.compile(rb'[\x20-\x7e]{10,}')

    for match in ascii_pattern.finditer(data):
        s = match.group().decode('ascii')
        # Filter for interesting malware strings
        interesting = [
            'http', 'https', 'tcp', 'udp', 'dns',
            'cmd', 'shell', 'exec', 'upload', 'download',
            'encrypt', 'decrypt', 'key', 'token', 'password',
            'c2', 'beacon', 'agent', 'implant', 'bot',
            'mutex', 'persist', 'registry', 'scheduled',
        ]
        if any(kw in s.lower() for kw in interesting):
            strings.append(s)

    return strings


def extract_dependencies(data):
    """Extract Go module dependencies from binary."""
    deps = []
    # Module paths follow pattern: github.com/user/repo
    dep_pattern = re.compile(
        rb'((?:github\.com|gitlab\.com|golang\.org|gopkg\.in|'
        rb'go\.etcd\.io|google\.golang\.org)/[^\x00\s]{5,80})'
    )

    for match in dep_pattern.finditer(data):
        dep = match.group().decode('utf-8', errors='replace')
        deps.append(dep)

    unique_deps = sorted(set(deps))
    return unique_deps


def analyze_go_binary(filepath):
    """Full analysis of Go malware binary."""
    with open(filepath, 'rb') as f:
        data = f.read()

    print(f"[+] Analyzing Go binary: {filepath}")
    print(f"  File size: {len(data):,} bytes")
    print("=" * 60)

    # Build info
    find_go_build_info(data)

    # pclntab
    pclntab_offset, go_version = find_pclntab(data)

    # Functions
    functions = extract_function_names(data, pclntab_offset)
    print(f"\n[+] Recovered {len(functions)} function names")

    # Categorize functions
    categories = {
        "network": [], "crypto": [], "os_exec": [],
        "file_io": [], "main": [], "third_party": [],
    }
    for f in functions:
        if 'net/' in f or 'http' in f.lower():
            categories["network"].append(f)
        elif 'crypto' in f:
            categories["crypto"].append(f)
        elif 'os/exec' in f or 'syscall' in f:
            categories["os_exec"].append(f)
        elif 'os.' in f or 'io/' in f:
            categories["file_io"].append(f)
        elif f.startswith('main.'):
            categories["main"].append(f)
        elif 'github.com' in f or 'golang.org' in f:
            categories["third_party"].append(f)

    for cat, funcs in categories.items():
        if funcs:
            print(f"\n  [{cat}] ({len(funcs)} functions):")
            for fn in funcs[:10]:
                print(f"    {fn}")

    # Dependencies
    deps = extract_dependencies(data)
    print(f"\n[+] Dependencies ({len(deps)}):")
    for dep in deps[:20]:
        print(f"    {dep}")

    # Suspicious strings
    sus_strings = extract_go_strings(data)
    print(f"\n[+] Suspicious strings ({len(sus_strings)}):")
    for s in sus_strings[:20]:
        print(f"    {s}")


if __name__ == "__main__":
    if len(sys.argv) < 2:
        print(f"Usage: {sys.argv[0]} <go_binary>")
        sys.exit(1)
    analyze_go_binary(sys.argv[1])

Step 2: Ghidra Analysis Script

# Ghidra script (run within Ghidra's script manager)
# Save as AnalyzeGoBinary.py in Ghidra scripts directory

# @category MalwareAnalysis
# @description Analyze Go binary structure and recover metadata

def analyze_go_binary_ghidra():
    """Ghidra script for Go binary analysis."""
    from ghidra.program.model.mem import MemoryAccessException

    program = getCurrentProgram()
    memory = program.getMemory()
    listing = program.getListing()

    print("[+] Go Binary Analysis Script")
    print(f"  Program: {program.getName()}")

    # Find pclntab
    pclntab_magics = [
        bytes([0xf0, 0xff, 0xff, 0xff]),  # Go 1.20+
        bytes([0xf1, 0xff, 0xff, 0xff]),  # Go 1.18-1.19
        bytes([0xfa, 0xff, 0xff, 0xff]),  # Go 1.16-1.17
        bytes([0xfb, 0xff, 0xff, 0xff]),  # Go 1.2-1.15
    ]

    for magic in pclntab_magics:
        addr = memory.findBytes(
            program.getMinAddress(), magic, None, True, None
        )
        if addr:
            print(f"[+] pclntab found at {addr}")
            # Create label
            program.getSymbolTable().createLabel(
                addr, "go_pclntab", None,
                ghidra.program.model.symbol.SourceType.ANALYSIS
            )
            break

    # Fix Go string definitions
    # Go strings are ptr+len, not null terminated
    print("[+] Fixing Go string references...")

    # Search for function names containing package paths
    symbol_table = program.getSymbolTable()
    func_count = 0
    for symbol in symbol_table.getAllSymbols(True):
        name = symbol.getName()
        if ('.' in name and
            any(pkg in name for pkg in
                ['main.', 'runtime.', 'net.', 'crypto.', 'os.'])):
            func_count += 1

    print(f"[+] Found {func_count} Go function symbols")


# Execute
analyze_go_binary_ghidra()

Validation Criteria

• Go version and build information extracted from binary
• pclntab located and parsed for function name recovery
• Third-party dependencies identified revealing malware capabilities
• Main package functions enumerated for targeted analysis
• Network, crypto, and OS exec functions categorized
• Ghidra analysis correctly labels Go runtime structures

References

• CUJO AI - Reverse Engineering Go Binaries with Ghidra
• Volexity GoResolver
• Go Reverse Engineering Tool Kit
• SentinelOne AlphaGolang
• Go Binary Reversing Notes