PWN Reconnaissance

Overview

The reconnaissance phase gathers critical information about a target binary before exploitation. This includes identifying architecture, protections, interesting strings, symbols, and potential libc version.

Reconnaissance Checklist

1. File type and architecture identification
2. Security protections (checksec)
3. Interesting strings extraction
4. Symbol table analysis
5. Libc identification (if applicable)
6. Seccomp filter detection

Step 1: File Identification

Identify the binary type and architecture:

file ./binary

Expected output interpretation:

Output Contains	Meaning
ELF 64-bit LSB executable	x86_64 architecture
ELF 32-bit LSB executable	x86 (i386) architecture
dynamically linked	Uses shared libraries (libc)
statically linked	Self-contained, no libc exploits
not stripped	Contains debug symbols
stripped	No debug symbols

Step 2: Security Protections

Run checksec to identify protections:

checksec --file=./binary

Or via pwntools:

from pwn import *
elf = ELF('./binary')
print(elf.checksec())

Protection Analysis

Protection	Enabled	Exploitation Impact
RELRO	Partial	GOT overwrite possible
RELRO	Full	No GOT overwrite, use other primitives
Stack Canary	Yes	Must leak or bypass canary
NX	Yes	No shellcode on stack, use ROP/ret2libc
PIE	Yes	Must leak binary base address
FORTIFY	Yes	Some unsafe functions hardened

Step 3: Strings Extraction

Find interesting strings:

strings -n 8 ./binary | grep -iE '(flag|password|secret|admin|shell|bin/sh|/bin)'

Look for:

• Format string specifiers (%s, %x, %n)
• Function names (system, execve)
• File paths (/bin/sh, /flag)
• Potential passwords or keys

Step 4: Symbol Analysis

Extract symbols if not stripped:

nm ./binary | grep -E ' [TtWw] ' | head -30

Or use readelf:

readelf -s ./binary | grep FUNC

Key symbols to note:

• main - Entry point for analysis
• win, flag, shell - Potential win functions
• vuln, vulnerable - Obvious vulnerability hints
• PLT entries for dangerous functions

Check for Win Functions

nm ./binary | grep -iE '(win|flag|shell|backdoor|secret)'

Step 5: PLT/GOT Analysis

Identify imported functions:

objdump -d ./binary | grep '@plt>:' | head -20

Or via pwntools:

from pwn import *
elf = ELF('./binary')
print("PLT entries:", list(elf.plt.keys()))
print("GOT entries:", list(elf.got.keys()))

Dangerous functions to note:

• gets, scanf, strcpy, sprintf - Buffer overflow
• printf, fprintf - Format string (if user-controlled)
• system, execve - Code execution targets

Step 6: Libc Identification

If libc is provided:

strings libc.so.6 | grep -E "^GNU C Library"
file libc.so.6
md5sum libc.so.6

Query libc database with known offsets:

# Using libc-database
./libc-database/find printf <leaked_printf_offset>

# Or online: https://libc.blukat.me/

Step 7: Seccomp Detection

Check for seccomp filters:

seccomp-tools dump ./binary

If seccomp is present, analyze allowed syscalls to determine exploitation constraints (e.g., no execve means ORW - open/read/write approach).

Output Format

## Reconnaissance

### Findings
- Architecture: x86_64, dynamically linked, not stripped
- Protections: Partial RELRO, No Canary, NX enabled, No PIE
- Dangerous functions: gets@plt, printf@plt (potential format string)
- Interesting symbols: main, vuln, win (0x401234)
- Libc: Not provided (infer from remote)

### Commands Run
- file ./binary
- checksec --file=./binary
- strings -n 8 ./binary
- nm ./binary

### Implications
- No PIE: Fixed addresses, direct ROP possible
- NX enabled: Cannot execute shellcode on stack
- gets present: Likely buffer overflow vulnerability
- win function exists: ret2win exploitation possible

### Next Steps
1. Disassemble vuln() and win() functions
2. Identify buffer size in vuln()
3. Calculate offset to return address
4. Craft ret2win payload

Quick Reference Commands

# All-in-one recon
file ./binary && checksec --file=./binary && nm ./binary 2>/dev/null | head -20

# Find dangerous functions
objdump -d ./binary | grep -E '<(gets|strcpy|sprintf|scanf|printf)@plt>'

# Check for win function
nm ./binary 2>/dev/null | grep -iE 'win|flag|shell' || echo "No obvious win function"

Additional Resources

References

• references/protection-bypass.md - Techniques for bypassing each protection
• references/libc-database.md - Using libc-database for identification

Scripts

• scripts/full-recon.sh - Run complete reconnaissance suite