reverse-skills-max: initial public release (restored, redacted, hardened)

2026-10-20 02:17:15 +03:00
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+# CTF Reverse - Tools Reference
+
+## Table of Contents
+- [GDB](#gdb)
+  - [Basic Commands](#basic-commands)
+  - [PIE Binary Debugging](#pie-binary-debugging)
+  - [One-liner Automation](#one-liner-automation)
+  - [Memory Examination](#memory-examination)
+- [Radare2](#radare2)
+  - [Basic Session](#basic-session)
+  - [r2pipe Automation](#r2pipe-automation)
+- [Ghidra](#ghidra)
+  - [Headless Analysis](#headless-analysis)
+  - [Emulator for Decryption](#emulator-for-decryption)
+  - [MCP Commands](#mcp-commands)
+- [Unicorn Emulation](#unicorn-emulation)
+  - [Basic Setup](#basic-setup)
+  - [Mixed-Mode (64 to 32) Switch](#mixed-mode-64-to-32-switch)
+  - [Register Tracing Hook](#register-tracing-hook)
+  - [Track Register Changes](#track-register-changes)
+- [Python Bytecode](#python-bytecode)
+  - [Disassembly](#disassembly)
+  - [Extract Constants](#extract-constants)
+  - [Pyarmor Static Unpack (1shot)](#pyarmor-static-unpack-1shot)
+- [WASM Analysis](#wasm-analysis)
+  - [Decompile to C](#decompile-to-c)
+  - [Common Patterns](#common-patterns)
+- [Android APK](#android-apk)
+  - [Extraction](#extraction)
+  - [Key Locations](#key-locations)
+  - [Search](#search)
+  - [Flutter APK (Blutter)](#flutter-apk-blutter)
+  - [HarmonyOS HAP/ABC (abc-decompiler)](#harmonyos-hapabc-abc-decompiler)
+- [.NET Analysis](#net-analysis)
+  - [Tools](#tools)
+  - [Two-Stage XOR + AES-CBC Decode Pattern (Codegate 2013)](#two-stage-xor--aes-cbc-decode-pattern-codegate-2013)
+  - [NativeAOT](#nativeaot)
+- [Packed Binaries](#packed-binaries)
+  - [UPX](#upx)
+  - [Custom Packers](#custom-packers)
+  - [PyInstaller](#pyinstaller)
+- [LLVM IR](#llvm-ir)
+  - [Convert to Assembly](#convert-to-assembly)
+- [RISC-V Binary Analysis (EHAX 2026)](#risc-v-binary-analysis-ehax-2026)
+- [Binary Ninja](#binary-ninja)
+- [Decompiler Comparison with dogbolt.org](#decompiler-comparison-with-dogboltorg)
+- [Useful Commands](#useful-commands)
+
+For dynamic instrumentation tools (Frida, angr, lldb, x64dbg), see [tools-dynamic.md](tools-dynamic.md).
+
+---
+
+## GDB
+
+### Basic Commands
+```bash
+gdb ./binary
+run                      # Run program
+start                    # Run to main
+b *0x401234              # Breakpoint at address
+b *main+0x100            # Relative breakpoint
+c                        # Continue
+si                       # Step instruction
+ni                       # Next instruction (skip calls)
+x/s $rsi                 # Examine string
+x/20x $rsp               # Examine stack
+info registers           # Show registers
+set $eax=0               # Modify register
+```
+
+### PIE Binary Debugging
+```bash
+gdb ./binary
+start                    # Forces PIE base resolution
+b *main+0xca            # Relative to main
+b *main+0x198
+run
+```
+
+### One-liner Automation
+```bash
+gdb -ex 'start' -ex 'b *main+0x198' -ex 'run' ./binary
+```
+
+### Memory Examination
+```bash
+x/s $rsi                 # String at RSI
+x/38c $rsi               # 38 characters
+x/20x $rsp               # 20 hex words from stack
+x/10i $rip               # 10 instructions from RIP
+```
+
+---
+
+## Radare2
+
+### Basic Session
+```bash
+r2 -d ./binary           # Open in debug mode
+aaa                      # Analyze all
+afl                      # List functions
+pdf @ main               # Disassemble main
+db 0x401234              # Set breakpoint
+dc                       # Continue
+ood                      # Restart debugging
+dr                       # Show registers
+dr eax=0                 # Modify register
+```
+
+### r2pipe Automation
+```python
+import r2pipe
+r2 = r2pipe.open('./binary', flags=['-d'])
+r2.cmd('aaa')
+r2.cmd('db 0x401234')
+
+for char in range(256):
+    r2.cmd('ood')        # Restart
+    r2.cmd(f'dr eax={char}')
+    output = r2.cmd('dc')
+    if 'correct' in output:
+        print(f"Found: {chr(char)}")
+```
+
+---
+
+## Ghidra
+
+### Headless Analysis
+```bash
+analyzeHeadless /path/to/project tmp -import binary -postScript script.py
+```
+
+### Emulator for Decryption
+```java
+EmulatorHelper emu = new EmulatorHelper(currentProgram);
+emu.writeRegister("RSP", 0x2fff0000);
+emu.writeRegister("RBP", 0x2fff0000);
+
+// Write encrypted data
+emu.writeMemory(dataAddress, encryptedBytes);
+
+// Set function arguments
+emu.writeRegister("RDI", arg1);
+
+// Run until return
+emu.setBreakpoint(returnAddress);
+emu.run(functionEntryAddress);
+
+// Read result
+byte[] decrypted = emu.readMemory(outputAddress, length);
+```
+
+### MCP Commands
+- Recon: `list_functions`, `list_imports`, `list_strings`
+- Analysis: `decompile_function`, `get_xrefs_to`
+- Annotation: `rename_function`, `rename_variable`
+
+---
+
+## Unicorn Emulation
+
+### Basic Setup
+```python
+from unicorn import *
+from unicorn.x86_const import *
+
+mu = Uc(UC_ARCH_X86, UC_MODE_64)
+
+# Map code segment
+mu.mem_map(0x400000, 0x10000)
+mu.mem_write(0x400000, code_bytes)
+
+# Map stack
+mu.mem_map(0x7fff0000, 0x10000)
+mu.reg_write(UC_X86_REG_RSP, 0x7fff0000 + 0xff00)
+
+# Run
+mu.emu_start(start_addr, end_addr)
+```
+
+### Mixed-Mode (64 to 32) Switch
+```python
+# When a 64-bit stub jumps into 32-bit code via retf/retfq:
+# - retf pops 4-byte EIP + 2-byte CS (6 bytes)
+# - retfq pops 8-byte RIP + 8-byte CS (16 bytes)
+
+uc32 = Uc(UC_ARCH_X86, UC_MODE_32)
+# Copy memory regions, then GPRs
+reg_map = {
+    UC_X86_REG_EAX: UC_X86_REG_RAX,
+    UC_X86_REG_EBX: UC_X86_REG_RBX,
+    UC_X86_REG_ECX: UC_X86_REG_RCX,
+    UC_X86_REG_EDX: UC_X86_REG_RDX,
+    UC_X86_REG_ESI: UC_X86_REG_RSI,
+    UC_X86_REG_EDI: UC_X86_REG_RDI,
+    UC_X86_REG_EBP: UC_X86_REG_RBP,
+}
+for e, r in reg_map.items():
+    uc32.reg_write(e, mu.reg_read(r) & 0xffffffff)  # mu = 64-bit emulator from above
+uc32.reg_write(UC_X86_REG_EFLAGS, mu.reg_read(UC_X86_REG_RFLAGS) & 0xffffffff)
+
+# SSE-heavy blobs need XMM registers copied
+for xr in [UC_X86_REG_XMM0, UC_X86_REG_XMM1, UC_X86_REG_XMM2, UC_X86_REG_XMM3,
+           UC_X86_REG_XMM4, UC_X86_REG_XMM5, UC_X86_REG_XMM6, UC_X86_REG_XMM7]:
+    uc32.reg_write(xr, mu.reg_read(xr))
+
+# Run 32-bit, then copy regs/memory back to 64-bit
+```
+
+**Tip:** set `UC_IGNORE_REG_BREAK=1` to silence warnings on unimplemented regs.
+
+### Register Tracing Hook
+```python
+def hook_code(uc, address, size, user_data):
+    if address == TARGET_ADDR:
+        rsi = uc.reg_read(UC_X86_REG_RSI)
+        print(f"0x{address:x}: rsi=0x{rsi:016x}")
+
+mu.hook_add(UC_HOOK_CODE, hook_code)
+```
+
+### Track Register Changes
+```python
+prev_rsi = [None]
+def hook_rsi_changes(uc, address, size, user_data):
+    rsi = uc.reg_read(UC_X86_REG_RSI)
+    if rsi != prev_rsi[0]:
+        print(f"0x{address:x}: RSI changed to 0x{rsi:016x}")
+        prev_rsi[0] = rsi
+
+mu.hook_add(UC_HOOK_CODE, hook_rsi_changes)
+```
+
+---
+
+## Python Bytecode
+
+### Disassembly
+```python
+import marshal, dis
+
+with open('file.pyc', 'rb') as f:
+    f.read(16)  # Skip header (varies by Python version)
+    code = marshal.load(f)
+    dis.dis(code)
+```
+
+### Extract Constants
+```python
+for ins in dis.get_instructions(code):
+    if ins.opname == 'LOAD_CONST':
+        print(ins.argval)
+```
+
+### Pyarmor Static Unpack (1shot)
+
+Repository: `https://github.com/Lil-House/Pyarmor-Static-Unpack-1shot`
+
+```bash
+# Basic usage (recursive processing)
+python /path/to/oneshot/shot.py /path/to/scripts
+
+# Specify pyarmor runtime library explicitly
+python /path/to/oneshot/shot.py /path/to/scripts -r /path/to/pyarmor_runtime.so
+
+# Save outputs to another directory
+python /path/to/oneshot/shot.py /path/to/scripts -o /path/to/output
+```
+
+Notes:
+- `oneshot/pyarmor-1shot` must exist before running `shot.py`.
+- Supported focus: Pyarmor 8.x-9.x (`PY` + six digits header style).
+- Pyarmor 7 and earlier (`PYARMOR` header) are out of scope.
+- Disassembly output is generally reliable; decompiled source is experimental.
+
+---
+
+## WASM Analysis
+
+### Decompile to C
+```bash
+wasm2c checker.wasm -o checker.c
+gcc -O3 checker.c wasm-rt-impl.c -o checker
+```
+
+### Common Patterns
+- `w2c_memory` - Linear memory array
+- `wasm_rt_trap(N)` - Runtime errors
+- Function exports: `flagChecker`, `validate`
+
+---
+
+## Android APK
+
+### Extraction
+```bash
+apktool d app.apk -o decoded/   # Best - decodes XML
+jadx app.apk                     # Decompile to Java
+unzip app.apk -d extracted/      # Simple extraction
+```
+
+### Key Locations
+- `res/values/strings.xml` - String resources
+- `AndroidManifest.xml` - App metadata
+- `classes.dex` - Dalvik bytecode
+- `assets/`, `res/raw/` - Resources
+
+### Search
+```bash
+grep -r "flag\|CTF" decoded/
+strings decoded/classes*.dex | grep -i flag
+```
+
+### Flutter APK (Blutter)
+
+```bash
+# Run Blutter on arm64 build
+python3 blutter.py path/to/app/lib/arm64-v8a out_dir
+```
+
+### HarmonyOS HAP/ABC (abc-decompiler)
+
+Repository: `https://github.com/ohos-decompiler/abc-decompiler`
+
+```bash
+# Extract .hap first to obtain .abc files
+unzip app.hap -d hap_extracted/
+```
+
+Critical startup mode:
+```bash
+# Use CLI entrypoint (avoid java -jar GUI mode)
+java -cp "./jadx-dev-all.jar" jadx.cli.JadxCLI [options] <input>
+```
+
+```bash
+# Basic decompile
+java -cp "./jadx-dev-all.jar" jadx.cli.JadxCLI -d "out" ".abc"
+
+# Recommended for .abc
+java -cp "./jadx-dev-all.jar" jadx.cli.JadxCLI -m simple --log-level ERROR -d "out_abc_simple" ".abc"
+```
+
+Notes:
+- Start with `-m simple --log-level ERROR`.
+- If `auto` fails, retry with `-m simple` first.
+- Errors do not always mean total failure; check `out_xxx/sources/`.
+- Use a fresh output directory per run.
+
+---
+
+## .NET Analysis
+
+### Tools
+- **dnSpy** - Debugging + decompilation (best)
+- **ILSpy** - Decompiler
+- **dotPeek** - JetBrains decompiler
+
+### NativeAOT
+- Look for `System.Private.CoreLib` strings
+- Type metadata present but restructured
+- Search for length-prefixed UTF-16 patterns
+
+### Two-Stage XOR + AES-CBC Decode Pattern (Codegate 2013)
+
+**Pattern:** .NET binary stores an encrypted byte array that undergoes XOR decoding followed by AES-256-CBC decryption. The same key value serves as both the AES key and IV.
+
+**Steps:**
+1. Extract hardcoded byte array and key string from binary (dnSpy/ILSpy)
+2. XOR each byte (may be multi-pass, e.g., `0x25` then `0x58`, equivalent to single `0x7D`)
+3. Base64-decode the XOR result
+4. AES-256-CBC decrypt with `RijndaelManaged` using the extracted key as both Key and IV
+
+```python
+from Crypto.Cipher import AES
+from base64 import b64decode
+
+# Step 1: XOR decode
+data = bytearray(encrypted_bytes)
+for i in range(len(data)):
+    data[i] ^= 0x7D  # Combined XOR key (0x25 ^ 0x58)
+
+# Step 2: Base64 decode
+ct = b64decode(bytes(data))
+
+# Step 3: AES-256-CBC decrypt (same value for key and IV)
+key = b"9e2ea73295c7201c5ccd044477228527"  # Padded to 32 bytes
+cipher = AES.new(key, AES.MODE_CBC, iv=key)
+plaintext = cipher.decrypt(ct)
+```
+
+**Key insight:** When `RijndaelManaged` appears in .NET decompilation, check if Key and IV are set to the same value — this is a common CTF pattern. The XOR stage often serves as a simple obfuscation layer before the real crypto.
+
+---
+
+## Packed Binaries
+
+### UPX
+```bash
+upx -d packed -o unpacked
+strings binary | grep UPX     # Check for UPX signature
+```
+
+### Custom Packers
+1. Set breakpoint after unpacking stub
+2. Dump memory
+3. Fix PE/ELF headers
+
+### PyInstaller
+```bash
+python pyinstxtractor.py binary.exe
+# Look in: binary.exe_extracted/
+```
+
+---
+
+## LLVM IR
+
+### Convert to Assembly
+```bash
+llc task.ll --x86-asm-syntax=intel
+gcc -c task.s -o file.o
+```
+
+---
+
+## RISC-V Binary Analysis (EHAX 2026)
+
+**Pattern (iguessbro):** Statically linked, stripped RISC-V ELF binary. Can't run natively on x86.
+
+**Disassembly with Capstone:**
+```python
+from capstone import *
+
+with open('binary', 'rb') as f:
+    code = f.read()
+
+# RISC-V 64-bit with compressed instruction support
+md = Cs(CS_ARCH_RISCV, CS_MODE_RISCVC | CS_MODE_RISCV64)
+md.detail = True
+
+# Disassemble from entry point (check ELF header for e_entry)
+TEXT_OFFSET = 0x10000  # typical for static RISC-V
+for insn in md.disasm(code[TEXT_OFFSET:], TEXT_OFFSET):
+    print(f"0x{insn.address:x}:\t{insn.mnemonic}\t{insn.op_str}")
+```
+
+**Common RISC-V patterns:**
+- `li a0, N` → load immediate (argument setup)
+- `mv a0, s0` → register move
+- `call offset` → function call (auipc + jalr pair)
+- `beq/bne a0, zero, label` → conditional branch
+- `sd/ld` → 64-bit store/load
+- `addiw` → 32-bit add (W-suffix = word operations)
+
+**Key differences from x86:**
+- No flags register — comparisons are inline with branch instructions
+- Arguments in a0-a7 (not rdi/rsi/rdx)
+- Return value in a0
+- Saved registers s0-s11 (callee-saved)
+- Compressed instructions (2 bytes) mixed with standard (4 bytes) — use `CS_MODE_RISCVC`
+
+**Anti-RE tricks in RISC-V:**
+- Fake flags as string constants (check for `"n0t_th3_r34l"` patterns)
+- Timing anti-brute-force (rdtime instruction)
+- XOR decryption with incremental key: `decrypted[i] = enc[i] ^ (key & 0xFF) ^ 0xA5; key += 7`
+
+**Emulation:** `qemu-riscv64 -L /usr/riscv64-linux-gnu/ ./binary` (needs cross-toolchain sysroot)
+
+---
+
+## Binary Ninja
+
+Interactive disassembler/decompiler with rapid community growth.
+
+**Decompilation outputs:** High-Level Intermediate Language (HLIL), pseudo-C, pseudo-Rust, pseudo-Python.
+
+```bash
+# Open binary
+binaryninja binary
+```
+
+```python
+# Headless analysis (Python API)
+import binaryninja
+bv = binaryninja.open_view("binary")
+for func in bv.functions:
+    print(func.name, hex(func.start))
+    print(func.hlil)  # High-Level IL
+```
+
+**Community plugins:** Available via Plugin Manager (Ctrl+Shift+P → "Plugin Manager").
+
+**Free version:** https://binary.ninja/free/ (cloud-based, limited features).
+
+**Advantages over Ghidra:** Faster startup, cleaner IL representations, better Python API for scripting.
+
+---
+
+## Decompiler Comparison with dogbolt.org
+
+**dogbolt.org** runs multiple decompilers simultaneously on the same binary and shows results side-by-side.
+
+**Supported decompilers:** Hex-Rays (IDA), Ghidra, Binary Ninja, angr, RetDec, Snowman, dewolf, Reko, Relyze.
+
+**When to use:**
+- Decompiler output is confusing — compare with alternatives for clarity
+- One decompiler mishandles a construct — another may get it right
+- Quick triage without installing every tool locally
+- Validate decompiler correctness by cross-referencing outputs
+
+```bash
+# Upload via web interface: https://dogbolt.org/
+# Or use the API:
+curl -F "file=@binary" https://dogbolt.org/api/binaries/
+```
+
+**Key insight:** Different decompilers excel at different constructs. When one produces unreadable output, another often generates clearer pseudocode. Cross-referencing catches decompiler bugs.
+
+---
+
+## Useful Commands
+
+```bash
+# File info
+file binary
+checksec --file=binary
+rabin2 -I binary
+
+# String extraction
+strings binary | grep -iE "flag|secret"
+rabin2 -z binary
+
+# Sections
+readelf -S binary
+objdump -h binary
+
+# Symbols
+nm binary
+readelf -s binary
+
+# Disassembly
+objdump -d binary
+objdump -M intel -d binary
+```