RsaCtfTool

RSA attack tool (mainly for ctf) - retreive private key from weak public key and/or uncipher data

Ganapati
3262
654
Python

RsaCtfTool

Test
lint_python
CodeQL
GitHub issues

GitHub forks
GitHub stars
GitHub license
GitHub contributors

This tool is an utility designed to decrypt data from weak public keys and attempt to recover the corresponding private key. Also this tool offers a comprehensive range of attack options, enabling users to apply various strategies to crack the encryption.
The RSA security, at its core, relies on the complexity of the integer factorization problem. This project serves as a valuable resource by combining multiple integer factorization algorithms, effectively enhancing the overall decryption capabilities.
Please note that this tool is primarily intended for educational purposes. It is essential to manage your expectations, as not every key can be broken within a reasonable timeframe. The complexity of the encryption algorithm may present significant challenges.
It is essential to highlight that the tool, exclusively supports the RSA textbook semiprime composite modulus rather than composite multiprimes. This constraint is embedded upstream in the pycrypto library (see TODO). While this limitation exists, the tool still offers a powerful set of features for attacking RSA keys with semiprime composite modulus.

For an advanced integer factorization tool please use msieve, yafu, or cado-nfs.

This tool is meant for educational purposes. For those participating in CTFs, please do the following first:

  • Learn the basics of RSA math and understand number theory, modular arithmetic, integer factorization and the fundamental theorem of arithmetic.
  • Read the code in this repository to understand what it does and how it works and suggest improvements by sending pull requests.
  • Avoid copy-pasting and running the tool without understanding the underlying math, as knowing the math is more valuable than knowing how to run the tool.

We hope this tool enhances your understanding of RSA encryption and serves as a valuable resource for exploring the intricacies of integer factorization. Use it responsibly and within the bounds of applicable laws and regulations.

Attacks provided:

Usage

usage: RsaCtfTool [-h] [--publickey PUBLICKEY] [--output OUTPUT] [--timeout TIMEOUT] [--createpub] [--dumpkey] [--ext] [--decryptfile DECRYPTFILE] [--decrypt DECRYPT]
                     [--verbosity {CRITICAL,ERROR,WARNING,DEBUG,INFO}] [--private] [--tests] [--ecmdigits ECMDIGITS] [-n N] [-p P] [-q Q] [-e E] [--key KEY]
                     [--password PASSWORD] [--show-factors SHOW_FACTORS]
                     [--attack {SQUFOF,XYXZ,binary_polinomial_factoring,brent,comfact_cn,cube_root,ecm,ecm2,factordb,fermat_numbers_gcd,fibonacci_gcd,highandlowbitsequal,mersenne_pm1_gcd,mersenne_primes,neca,nonRSA,noveltyprimes,pastctfprimes,pisano_period,pollard_p_1,primorial_pm1_gcd,qicheng,roca,siqs,small_crt_exp,smallfraction,smallq,system_primes_gcd,wolframalpha,wiener,boneh_durfee,euler,pollard_rho,williams_pp1,partial_q,partial_d,londahl,z3_solver,dixon,lehmer,fermat,hart,common_factors,common_modulus,same_n_huge_e,hastads,lattice,lehman,carmichael,qs,classical_shor,all} [{SQUFOF,XYXZ,binary_polinomial_factoring,brent,comfact_cn,cube_root,ecm,ecm2,factordb,fermat_numbers_gcd,fibonacci_gcd,highandlowbitsequal,mersenne_pm1_gcd,mersenne_primes,neca,nonRSA,noveltyprimes,pastctfprimes,pisano_period,pollard_p_1,primorial_pm1_gcd,qicheng,roca,siqs,small_crt_exp,smallfraction,smallq,system_primes_gcd,wolframalpha,wiener,boneh_durfee,euler,pollard_rho,williams_pp1,partial_q,partial_d,londahl,z3_solver,dixon,lehmer,fermat,hart,common_factors,common_modulus,same_n_huge_e,hastads,lattice,lehman,carmichael,qs,classical_shor,factorial_pm1_gcd,lucas_gcd,all} ...]]
                     [--sendtofdb] [--isconspicuous] [--isroca] [--convert_idrsa_pub] [--check_publickey] [--partial]

Installation

Virtual environment run (Preferred method)

Setup the venv

apt install python3-virtualenv
virtualenv venv
source venv/bin/activate
pip install git+https://github.com/RsaCtfTool/RsaCtfTool

Run

source venv/bin/activate
RsaCtfTool <arguments>
# See running section for examples.

Requirements

  • python3.9
  • GMPY2
  • PyCrypto
  • Requests
  • Libnum
  • SageMath : optional but advisable
  • Sage binaries

Docker run

docker build -t rsactftool/rsactftool .
docker run -it --rm -v $PWD:/data rsactftool/rsactftool <arguments>

Sagemath installing

If you also want the optional SageMath , you need to do

sudo dnf install sagemath
pip3 install -r "optional-requirements.txt"

MacOS-specific Instructions

If pip3 install -r "requirements.txt" fails to install requirements accessible within the environment, the following command may work.

easy_install `cat requirements.txt`

If you installed gmpy2 with homebrew(brew install gmp), you might have to point clang towards the header files with this command:
CFLAGS=-I/opt/homebrew/include LDFLAGS=-L/opt/homebrew/lib pip3 install -r requirements.txt

Optional to factor roca keys upto 512 bits, Install neca:

You can follow the instructions at : https://www.mersenneforum.org/showthread.php?t=23087

Runing

Mode 1 : Attack RSA (specify --publickey or n and e)

  • publickey : public rsa key to crack. You can import multiple public keys with wildcards.
  • decrypt : cipher message to decrypt
  • private : display private rsa key if recovered

Mode 2 : Create a Public Key File Given n and e (specify --createpub)

  • n : modulus
  • e : public exponent

Mode 3 : Dump the public and/or private numbers (optionally including CRT parameters in extended mode) from a PEM/DER format public or private key (specify --dumpkey)

  • key : the public or private key in PEM or DER format

Decrypt file

RsaCtfTool --publickey ./key.pub --decryptfile ./ciphered\_file

Print private key

RsaCtfTool --publickey ./key.pub --private

Attempt to break multiple public keys with common factor attacks or individually- use quotes around wildcards to stop bash expansion

RsaCtfTool --publickey "*.pub" --private

Optionally send the results back to factordb

RsaCtfTool --publickey "*.pub" --private --sendtofdb

Generate a public key

RsaCtfTool --createpub -n 7828374823761928712873129873981723...12837182 -e 65537

Dump the parameters from a key

RsaCtfTool --dumpkey --key ./key.pub

Check a given private key for conspicuousness

RsaCtfTool --key examples/conspicuous.priv --isconspicuous

Factor with ECM when you know the approximate length in digits of a prime

RsaCtfTool --publickey key.pub --ecmdigits 25 --verbose --private

For more examples, look at the test.sh file

Attack private keys with partial bits of Q known

RsaCtfTool --attack partial_q --key examples/masked.pem

Attack private keys with partial bits of D known

RsaCtfTool --attack partial_d --key examples/partial_d.pem

Convert idrsa.pub to pem format

RsaCtfTool --convert_idrsa_pub --publickey $HOME/.ssh/id_rsa.pub

Check if a given key or keys are roca

RsaCtfTool --isroca --publickey "examples/*.pub"

TODO (aka. Help wanted !)

  • Implement a test method for each attack.
  • Assign the correct algorithm complexity in Big O notation for each attack.
  • Support multiprime RSA, the project currently supports textbook RSA.
  • Wanted feature: Ransomware decrypter.

Contributing

  • Please read the CONTRIBUTING.md guideline for the bare minimum acceptable PRs.
  • Also please read the CODE_OF_CONDUCT.md, any contribution of any user not honoring it will ignored and the user blocked, good manners are paramount.

Licensing

  • The original project was released under the GPLv3 license. This code has been relicensed under the MIT License.

Thanks to all our Contributors

🔼 Back to top