Scan a binary file, try to find x509 der certificates, then dump to files.

cert.py

import OpenSSL.crypto as crypto
import sys


def progress_bar(current, total):
    """Print a progress bar to the console."""
    progress = float(current) / float(total)
    bar_length = 40
    filled_length = int(round(bar_length * progress))
    bar = '=' * filled_length + '-' * (bar_length - filled_length)
    sys.stdout.write('\r%s/%s [%s] %.2f%%' % (current, total, bar, progress * 100))
    sys.stdout.flush()


# 读取DER格式的X.509数字证书文件
with open(sys.argv[1], 'rb') as cert_file:
    cert_data = cert_file.read()

scan_count = 0

print("Scan start.")
while True:
    #check if scan is over.
    if len(cert_data) <= scan_count:
        print("\nScan over.")
        exit(0)
    # print(f"trying offset:{scan_count}",)

    # show the progress_bar 
    progress_bar(scan_count, len(cert_data))

    try_cert = cert_data[scan_count:]
    if try_cert[:2] != b'\x30\x82':
        # print(f"trying offset:{scan_count}",)
        scan_count += 1
        continue


    try:

        # 解析X.509数字证书
        x509_cert = crypto.load_certificate(crypto.FILETYPE_ASN1, try_cert)
        # 读取证书信息
        subject = x509_cert.get_subject()
        issuer = x509_cert.get_issuer()
        serial_number = x509_cert.get_serial_number()
        not_before = x509_cert.get_notBefore()
        not_after = x509_cert.get_notAfter()
        public_key = x509_cert.get_pubkey()

        # 输出证书信息
        print('Subject:', subject)
        print('Issuer:', issuer)
        print('Serial number:', serial_number)
        print('Not before:', not_before)
        print('Not after:', not_after)
        print('Public key:', public_key)
   


        cert_binary_data = crypto.dump_certificate(crypto.FILETYPE_ASN1, x509_cert)
        cert_size = len(cert_binary_data)
        with open(f"cert@{scan_count}.der","wb") as f:
            f.write(cert_binary_data)
        scan_count=scan_count + cert_size
    except Exception as e:
        #print(e)
        #print("Failed.")
        scan_count = scan_count + 1