II. Code Signing/python/SignatureReader.py

@@ -0,0 +1,67 @@
+#!/usr/bin/env python3
+from asn1crypto.cms import ContentInfo
+import argparse
+import subprocess
+
+def read_file_to_bytes(filename):
+    '''Read a file and return its contents as bytes.'''
+    with open(filename, 'rb') as file:
+        file_contents = file.read()
+    return file_contents
+
+def loadCMS(cms_signature, human_readable=False):
+    '''Returns SignedData information in a human-readable or native format about the CMS Signature loaded from a file.'''
+    # Load the CMS signature using asn1crypto
+    content_info = ContentInfo.load(cms_signature)
+    # Access the SignedData structure
+    cms = content_info['content']
+
+    if human_readable:
+        openssl_cmd = ['openssl', 'cms', '-cmsout', '-print', '-inform', 'DER', '-in', args.load_cms]
+        result = subprocess.run(openssl_cmd, stdout=subprocess.PIPE, stderr=subprocess.PIPE)
+        return result.stdout.decode('utf-8')
+    else:
+        return cms.native
+
+def extractSignature(cms_signature, human_readable=False):
+    '''Return Signature from the CMS Signature'''
+    content_info = ContentInfo.load(cms_signature)
+    # Access the SignedData structure
+    signed_data = content_info['content']
+    # Access the SignerInfo structure
+    signer_info = signed_data['signer_infos'][0]
+    # Extract the signature
+    signature = signer_info['signature']
+   
+    if human_readable:
+        return f"0x{signature.contents.hex()}"
+    else:
+        return signature.native
+
+def extractPubKeyFromCert():
+    openssl_cmd = ['openssl', 'x509', '-inform', 'DER', '-in', args.extract_pubkey, '-pubkey', '-noout']
+    result = subprocess.run(openssl_cmd, stdout=subprocess.PIPE, stderr=subprocess.PIPE)
+    if result.returncode == 0:
+        with open('extracted_pubkey.pem', 'wb') as pubkey_file:
+            pubkey_file.write(result.stdout)
+    else:
+        print("Error:", result.stderr.decode('utf-8'))
+
+# Argument parsing
+parser = argparse.ArgumentParser(description='CMS Signature Loader')
+parser.add_argument('--load_cms', help="Load the DER encoded CMS Signature from the filesystem and print it", metavar='cms_signature.der')
+parser.add_argument('--extract_signature', help="Extract and print the signature part from the DER encoded CMS Signature", metavar='cms_signature.der')
+parser.add_argument('--extract_pubkey', help="Extract public key from the given certificate and save it to extracted_pubkey.pem", metavar='cert_0')
+parser.add_argument('--human', help="Print in human-readable format", action='store_true')
+args = parser.parse_args()
+
+if args.load_cms:
+    cms_signature = read_file_to_bytes(args.load_cms)
+    print(loadCMS(cms_signature, args.human))
+
+if args.extract_signature:
+    cms_signature = read_file_to_bytes(args.extract_signature)
+    print(extractSignature(cms_signature, args.human))
+
+if args.extract_pubkey:
+    extractPubKeyFromCert()