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analyze-firmware.md

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Analyze Firmware

After you successfully obtained a firmware dump, it's time to analyze its content.

Quick wins

binwalk is the goto option for quickly analyzing your firmware

  • Identify data

    • binwalk firmware.bin : will give you an overview which contents are found in the dump

    • Example Output:

      DECIMAL       HEXADECIMAL     DESCRIPTION
--------------------------------------------------------------------------------
0             0x0             U-Boot bootloader image, header size: 64 bytes, load address: 0x80800000, entry point: 0x80800000, CRC32: 0xFFFFFFFF
64            0x40            LZMA compressed data, properties: 0x5D, dictionary size: 8388608 bytes, uncompressed size: 524288 bytes
1024          0x400           Linux kernel ARM boot executable zImage (little-endian)
1048576       0x100000        Squashfs filesystem, little endian, version 4.0, compression: lzma, size: 262144 bytes, 1198 inodes, blocksize: 131072 bytes, created: Mon Jan  1 00:00:00 2024

  • Extract Firmware

    • binwalk -e firmware.bin : will try to automatically extract all content => will often give us full root-filesystem.
    • Example:

    Example extraction of a firmware

  • Entropy Analyiss

    • binwalk -E firmware.binThis will give us the entropy of the firmware
      • Note: parts of very high entropy can be sign for compression or encryption being used.
      • Example Output:

    Here we see a blob which might be encrypted or compressed


The strings command can be helpful to quickly find sensitive data like passwords or password hashes:

  • Password Hashes:

    strings firmware.bin | grep -E ':[x$1$5$6]:'

  • Hardcoded Credentials

    strings firmware.bin | grep -i 'password'
strings firmware.bin | grep -i 'user'
strings firmware.bin | grep -i 'admin'
strings firmware.bin | grep -i 'login'

  • Private Keys and Certificates

    strings firmware.bin | grep -i 'PRIVATE KEY'
strings firmware.bin | grep -i 'BEGIN RSA'
strings firmware.bin | grep -i 'BEGIN DSA'

  • API Keys, Tokens, and Secrets

    strings firmware.bin | grep -i 'api_key'
strings firmware.bin | grep -i 'token'
strings firmware.bin | grep -i 'secret'

  • IP Addresses and URLs

    strings firmware.bin | grep -Eo '([0-9]{1,3}\.){3}[0-9]{1,3}'
strings firmware.bin | grep -E 'http://|https://'
strings firmware.bin | grep -i 'ftp'

  • Configuration Files

    strings firmware.bin | grep -i '.conf'
strings firmware.bin | grep -i '.ini'
strings firmware.bin | grep -i '.xml'

  • Encryption Keys and Passwords

    strings firmware.bin | grep -i 'encryption_key'
strings firmware.bin | grep -i 'aes'
strings firmware.bin | grep -i 'des'
strings firmware.bin | grep -i 'key='

  • Version Information

    strings firmware.bin | grep -i 'version'
strings firmware.bin | grep -i 'build'

  • Debug Information

    strings firmware.bin | grep -i 'debug'
strings firmware.bin | grep -i 'trace'
strings firmware.bin | grep -i 'error'
strings firmware.bin | grep -i 'fail'

  • Email Addresses

    strings firmware.bin | grep -E '\b[A-Za-z0-9._%+-]+@[A-Za-z0-9.-]+\.[A-Z|a-z]{2,}\b'

  • Encryption/Decryption Routines

    strings firmware.bin | grep -i 'openssl'
strings firmware.bin | grep -i 'encrypt'
strings firmware.bin | grep -i 'decrypt'

  • Default and Backup Files

    strings firmware.bin | grep -i 'default'
strings firmware.bin | grep -i 'backup'

  • SSH Information

    strings firmware.bin | grep -i 'ssh'
strings firmware.bin | grep -i 'port'

Analysis of bare metal firmware

Todo

Resources: