Merge pull request #22 from mkb79/issue-3

decrypt license voucher with example

Author: mkb79

examples/download_books_aax.py

@@ -58,7 +58,6 @@ def download_file(url):
 
     auth = audible.FileAuthenticator(
         filename="FILENAME",
-        encryption="json",
         password=password
     )
     client = audible.Client(auth)

examples/download_books_aaxc.py

@@ -1,18 +1,20 @@
+import json
 import pathlib
-import shutil
 
 import audible
 import httpx
+from audible.aescipher import decrypt_voucher_from_licenserequest
 
 
-# files downloaded via this script can't be converted at this moment
+# files downloaded via this script can be converted
 # audible uses a new format (aaxc instead of aax)
 # more informations and workaround here:
 # https://github.com/mkb79/Audible/issues/3
+# especially: https://github.com/mkb79/Audible/issues/3#issuecomment-705262614
 
 
-# get download link(s) for book
-def _get_download_link(asin, quality):
+# get license response for book
+def get_license_response(client, asin, quality):
     try:
         response = client.post(
             f"content/{asin}/licenserequest",
@@ -22,16 +24,21 @@ def _get_download_link(asin, quality):
                 "quality": quality
             }
         )
-        return response['content_license']['content_metadata']['content_url']['offline_url']
+        return response
     except Exception as e:
         print(f"Error: {e}")
         return
 
 
+def get_download_link(license_response):
+    return license_response["content_license"]["content_metadata"]["content_url"]["offline_url"]
+
+
 def download_file(url, filename):
-    r = httpx.get(url)
-    with open(filename, 'wb') as f:
-        shutil.copyfileobj(r.iter_raw, f)
+    with httpx.stream("GET", url) as r:
+        with open(filename, 'wb') as f:
+            for chunck in r.iter_bytes():
+                f.write(chunck)
     return filename
 
 
@@ -40,24 +47,33 @@ def download_file(url, filename):
 
     auth = audible.FileAuthenticator(
         filename="FILENAME",
-        encryption="json",
         password=password
     )
-    client = audible.AudibleAPI(auth)
+    client = audible.Client(auth)
 
     books = client.get(
-        path="0.0/library/books",
+        path="library",
         params={
-            "purchaseAfterDate": "01/01/1970"
-        }
-    )["books"]["book"]
-
-    for book in books:
-        asin = book['asin']
-        title = book['title'] + f"( {asin}).aaxc"
-        dl_link = _get_download_link(asin, quality="Extreme")
-        if dl_link:
+            "response_groups": "product_attrs",
+            "num_results": "999"
+            }
+    )
+
+    for book in books["items"]:
+        asin = book["asin"]
+        title = book["title"] + f"( {asin}).aaxc"
+        lr = get_license_response(client, asin, quality="Extreme")
+
+        if lr:
+            # download book
+            dl_link = get_download_link(lr)
             filename = pathlib.Path.cwd() / "audiobooks" / title
             print(f"download link now: {dl_link}")
             status = download_file(dl_link, filename)
-            print(f"downloaded file: {status}")
+            print(f"downloaded file: {status} to {filename}")
+
+            # save voucher
+            voucher_file = filename.with_suffix(".json")
+            decrypted_voucher = decrypt_voucher_from_licenserequest(auth, lr)
+            voucher_file.write_text(json.dumps(decrypted_voucher, indent=4))
+            print(f"saved voucher to: {voucher_file}")

src/audible/aescipher.py

@@ -231,3 +231,52 @@ def remove_file_encryption(source, target, password, **kwargs):
     crypter = AESCipher(password, **kwargs)
     decrypted = crypter.from_file(source_file, encryption=encryption)
     pathlib.Path(target).write_text(decrypted)
+
+
+def _decrypt_voucher(device_serial_number, customer_id, device_type, asin, voucher):
+    # https://github.com/mkb79/Audible/issues/3#issuecomment-705262614
+    buf = (device_type + device_serial_number + customer_id + asin).encode("ascii")
+    digest = sha256(buf).digest()
+    key = digest[0:16]
+    iv = digest[16:]
+
+    # decrypt "voucher" using AES in CBC mode with no padding
+    plaintext = aes_cbc_decrypt(key, iv, voucher).rstrip("\x00")
+    return json.loads(plaintext)
+
+
+def decrypt_voucher_from_licenserequest(auth, license_response):
+    """Decrypt the voucher from licenserequest response
+
+    :param auth: An instance of an `Authenticator` clsss
+    :type auth: audible.FileAuthenticator, audible.LoginAuthenticator
+    :param license_response: The response content from a successful http 
+        `POST` request to api endpoint /1.0/content/{asin}/licenserequest
+    :type license_response: dict
+    :returns: The decryptes license voucher with needed key and iv
+    :rtype: dict
+
+    .. note::
+        A device registration is needed to use the auth instance for a 
+        license request and to obtain the needed device data
+    
+    """
+    # device data
+    device_info = auth.device_info
+    device_serial_number = device_info["device_serial_number"]
+    device_type = device_info["device_type"]
+
+    # user data
+    customer_id = auth.customer_info["user_id"]
+
+    # book specific data
+    asin = license_response["content_license"]["asin"]
+    encrypted_voucher = base64.b64decode(license_response["content_license"]["license_response"])
+
+    return _decrypt_voucher(
+        device_serial_number=device_serial_number,
+        customer_id=customer_id,
+        device_type=device_type,
+        asin=asin,
+        voucher=encrypted_voucher
+    )

src/audible/auth.py

@@ -65,8 +65,8 @@ def refresh_website_cookies(
 
     raw_cookies = resp_dict["response"]["tokens"]["cookies"]
     website_cookies = dict()
-    for domain in raw_cookies:
-        for cookie in raw_cookies[domain]:
+    for cookies_domain in raw_cookies:
+        for cookie in raw_cookies[cookies_domain]:
             website_cookies[cookie["Name"]] = cookie["Value"].replace(r'"',
                                                                       r'')