crypto-weakness

name	crypto-weakness
description	Cryptographic weakness and insecure crypto implementation hunting in IoT firmware. Use when analyzing encryption implementations, TLS/SSL configurations, key management, random number generation, or any cryptographic operations in embedded device firmware. Triggers on crypto analysis, weak encryption, insecure TLS, or key management tasks.

Cryptographic Weakness Hunting

Find weak or broken cryptographic implementations in IoT firmware.

Workflow

1. Identify crypto library usage
2. Check TLS/SSL configuration
3. Analyze key management
4. Verify random number generation
5. Check for known weak algorithms

Crypto Library Detection

# Check linked crypto libraries
readelf -d <binary> | grep -i "ssl\|crypto\|mbedtls\|wolfssl\|openssl"
ldd <binary> 2>/dev/null | grep -i "ssl\|crypto"

# Find crypto-related strings
strings <binary> | grep -iE "aes|des|rsa|sha|md5|rc4|ssl|tls|encrypt|decrypt|cipher|hmac"

# Check OpenSSL version (often outdated in IoT)
strings <binary> | grep -i "openssl"
find extracted_fs/ -name "libssl*" -o -name "libcrypto*" | xargs strings | grep "OpenSSL"

Weakness Categories

1. Weak Algorithms

Algorithm	Status	Why
MD5	Broken	Collision attacks
SHA-1	Deprecated	Theoretical collisions
DES/3DES	Deprecated	Small key/block size
RC4	Broken	Biased output stream
RSA < 2048-bit	Weak	Factorable
ECB mode	Weak	Pattern preservation

# Search for weak algorithm usage in binaries
strings <binary> | grep -iE "^(md5|des|rc4|ecb)"
# In Ghidra: search for MD5_Init, DES_ecb_encrypt, RC4

2. Hardcoded Keys/IVs

# Search for hex key patterns (16/32 bytes)
strings <binary> | grep -E "^[0-9a-fA-F]{32,64}$"

# Search for base64-encoded keys
strings <binary> | grep -E "^[A-Za-z0-9+/]{22,44}={0,2}$"

# Common hardcoded key indicators in decompiled code:
# key[] = {0x01, 0x02, 0x03, ...}
# iv = "0000000000000000"
# password = "default_key"

3. Weak Random Number Generation

// VULNERABLE patterns in decompiled code:
srand(time(NULL));           // Predictable seed
rand() % range;              // Weak PRNG
getpid() as random source;   // Predictable
time(NULL) for session token; // Guessable

4. TLS/SSL Issues

# Test TLS configuration of running device
nmap --script ssl-enum-ciphers -p 443 <device_ip>

# Check certificate
openssl s_client -connect <device_ip>:443 </dev/null 2>/dev/null | openssl x509 -text

# Look for self-signed certs in firmware
find extracted_fs/ -name "*.pem" -o -name "*.crt" | while read f; do
    echo "=== $f ==="
    openssl x509 -in "$f" -text -noout 2>/dev/null | grep -E "Issuer|Subject|Not After|Signature Algorithm"
done

5. Firmware Update Verification

# Check if firmware updates are signed
# Look for signature verification in update handler
strings <update_binary> | grep -iE "verify|signature|rsa|ecdsa|sha256|digest"

# If no verification → firmware can be replaced with malicious version

CWE References

• CWE-327: Use of a Broken or Risky Cryptographic Algorithm
• CWE-328: Use of Weak Hash
• CWE-330: Use of Insufficiently Random Values
• CWE-326: Inadequate Encryption Strength
• CWE-295: Improper Certificate Validation
• CWE-347: Improper Verification of Cryptographic Signature