Add support for saving and loading licenses as a string (#4)

* Add support for saving and loading licenses as a string

* Update examples

Author: artemlos

.gitignore

@@ -102,3 +102,4 @@ venv.bak/
 
 # mypy
 .mypy_cache/
+licensefile.skm

README.md

@@ -35,10 +35,38 @@ if res[0] == None:
     print("An error occured: {0}".format(res[1]))
 else:
     print("Success")
+    
+    license_key = res[0]
+    print("Feature 1: " + str(license_key.f1))
+    print("License expires: " + str(license_key.expires))
 ```
 
 * `pubKey` - the RSA public key (can be found [here](https://app.cryptolens.io/docs/api/v3/QuickStart#api-keys), in *API Keys* section).
 * `token` - the access token (can be found [here](https://app.cryptolens.io/docs/api/v3/QuickStart#api-keys), in *API Keys* section).
 * `product_id` - the id of the product can be found on the product page.
 * `key` - the license key to be verified
 * `machine_code` - the unique id of the device (we are working on adding a method similar to `Helpers.GetMachineCode()`).
+
+### Offline activation (saving/loading licenses)
+
+Assuming the license key verification was successful, we can save the result in a file so that we can use it instead of contacting Cryptolens.
+
+```python
+# res is obtained from the code above
+
+if res[0] != None:
+    # saving license file to disk
+    with open('licensefile.skm', 'w') as f:
+        f.write(res[0].save_as_string())
+```
+
+When loading it back, we can use the code below:
+
+```python
+# read license file from file
+with open('licensefile.skm', 'r') as f:
+    license_key = LicenseKey.load_from_string(pubKey, f.read())
+    
+    print("Feature 1: " + str(license_key.f1))
+    print("License expires: " + str(license_key.expires))
+```

licensing/methods.py

@@ -54,7 +54,4 @@ def activate(token, rsa_pub_key, product_id, key, machine_code, fields_to_return
                 else:
                     return (None, "The signature check failed.")
             except Exception:
-                return (None, "The signature check failed.")
-        
-        
-    
+                return (None, "The signature check failed.")

licensing/models.py

@@ -8,6 +8,9 @@
 import json
 import base64
 import datetime
+import copy
+
+from licensing.internal import Helpers
 
 class LicenseKey:
 
@@ -40,7 +43,7 @@ def __init__(self, ProductId, ID, Key, Created, Expires, Period, F1, F2,\
         self.allowed_machines = AllowedMachines
         self.data_objects = DataObjects
         self.sign_date = SignDate
-        self.raw_respone = RawResponse
+        self.raw_response = RawResponse
 
     def from_response(response):
 
@@ -56,6 +59,44 @@ def from_response(response):
                           obj["Customer"], obj["ActivatedMachines"], obj["TrialActivation"], \
                           obj["MaxNoOfMachines"], obj["AllowedMachines"], obj["DataObjects"], \
                           datetime.datetime.fromtimestamp(obj["SignDate"]), response)
+        
+    def save_as_string(self):
+        """
+        Save the license as a string that can later be read by load_from_string.
+        """
+        res = copy.copy(self.raw_response.__dict__)
+        res["licenseKey"] = res["license_key"]
+        res.pop("license_key", None)
+        return json.dumps(res)
+    
+    def load_from_string(rsa_pub_key, string):
+        """
+        Loads a license from a string generated by save_as_string.
+        Note: if an error occurs, None will be returned. An error can occur
+        if the license string has been tampered with or if the public key is
+        incorrectly formatted.
+        """
+        
+        response = Response("","","","")
+        
+        try:
+            response = Response.from_string(string)
+        except Exception as ex:
+            return None
+        
+        if response.result == "1":
+            return None
+        else:
+            try:
+                pubKey = RSAPublicKey.from_string(rsa_pub_key)
+                if Helpers.verify_signature(response, pubKey):
+                    return LicenseKey.from_response(response)
+                else:
+                    return None
+            except Exception:
+                return None
+        
+        
 
 class Response:
 
@@ -66,7 +107,7 @@ def __init__(self, license_key, signature, result, message):
         self.message = message
 
     def from_string(responseString):        
-        obj = json.loads(responseString)        
+        obj = json.loads(responseString)
         return Response(obj["licenseKey"], obj["signature"], obj["result"],obj["message"])
 
 class RSAPublicKey:

setup.py

@@ -2,13 +2,13 @@
 setup(
   name = 'licensing',         # How you named your package folder (MyLib)
   packages = ['licensing'],   # Chose the same as "name"
-  version = '0.2',      # Start with a small number and increase it with every change you make
+  version = '0.3',      # Start with a small number and increase it with every change you make
   license='MIT',        # Chose a license from here: https://help.github.com/articles/licensing-a-repository
   description = 'Client library for Cryptolens licensing Web API.',   # Give a short description about your library
   author = 'Cryptolens AB',                   # Type in your name
   author_email = '[email protected]',      # Type in your E-Mail
   url = 'https://cryptolens.io',   # Provide either the link to your github or to your website
-  download_url = 'https://github.com/Cryptolens/cryptolens-python/archive/v_02.tar.gz',    # I explain this later on
+  download_url = 'https://github.com/Cryptolens/cryptolens-python/archive/v_03.tar.gz',    # I explain this later on
   keywords = ['software licensing', 'licensing library', 'cryptolens'],   # Keywords that define your package best
   install_requires=[            # I get to this in a second
           'pycrypto'

test.py

@@ -6,16 +6,35 @@
 """
 
 from licensing.internal import Helpers
-from licensing.models import Response, RSAPublicKey
+from licensing.models import Response, RSAPublicKey, LicenseKey
 from licensing.methods import Key
 
 pubKey = "<RSAKeyValue><Modulus>sGbvxwdlDbqFXOMlVUnAF5ew0t0WpPW7rFpI5jHQOFkht/326dvh7t74RYeMpjy357NljouhpTLA3a6idnn4j6c3jmPWBkjZndGsPL4Bqm+fwE48nKpGPjkj4q/yzT4tHXBTyvaBjA8bVoCTnu+LiC4XEaLZRThGzIn5KQXKCigg6tQRy0GXE13XYFVz/x1mjFbT9/7dS8p85n8BuwlY5JvuBIQkKhuCNFfrUxBWyu87CFnXWjIupCD2VO/GbxaCvzrRjLZjAngLCMtZbYBALksqGPgTUN7ZM24XbPWyLtKPaXF2i4XRR9u6eTj5BfnLbKAU5PIVfjIS+vNYYogteQ==</Modulus><Exponent>AQAB</Exponent></RSAKeyValue>"
 
-res = Key.activate(token="WyIyNTU1IiwiRjdZZTB4RmtuTVcrQlNqcSszbmFMMHB3aWFJTlBsWW1Mbm9raVFyRyJd",\
+res = Key.activate(token="WyIyNjA1IiwiTjhZQUpIYXJPaVdBV0ozQUlKVC9tamdDbFZDRzhZRHpaU243L2R2eCJd",\
                    rsa_pub_key=pubKey,\
                    product_id=3349, key="ICVLD-VVSZR-ZTICT-YKGXL", machine_code="test")
 
 if res[0] == None:
     print("An error occured: {0}".format(res[1]))
 else:
-    print("Success")
+    print("Success")
+    
+    license_key = res[0]
+    print("Feature 1: " + str(license_key.f1))
+    print("License expires: " + str(license_key.expires))
+    
+    
+if res[0] != None:
+    # saving license file to disk
+    with open('licensefile.skm', 'w') as f:
+        f.write(res[0].save_as_string())
+        
+
+# read license file from file
+with open('licensefile.skm', 'r') as f:
+    license_key = LicenseKey.load_from_string(pubKey, f.read())
+    
+    print("Feature 1: " + str(license_key.f1))
+    print("License expires: " + str(license_key.expires))
+