Add signature time interval when loading a license (#7)

* Add signature time interval when loading a license, closes #6

* Add example

* Add support for floating

Author: artemlos

README.md

@@ -31,7 +31,7 @@ res = Key.activate(token="WyIyNTU1IiwiRjdZZTB4RmtuTVcrQlNqcSszbmFMMHB3aWFJTlBsWW
                    product_id=3349, key="ICVLD-VVSZR-ZTICT-YKGXL", \
                    machine_code=Helpers.GetMachineCode())
 
-if res[0] == None not Helpers.IsOnRightMachine(res[0]):
+if res[0] == None or not Helpers.IsOnRightMachine(res[0]):
     print("An error occurred: {0}".format(res[1]))
 else:
     print("Success")
@@ -64,11 +64,53 @@ 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())
+    license_key = LicenseKey.load_from_string(pubKey, f.read(), 30)
 
-    if not Helpers.IsOnRightMachine(license_key):
+    if license_key != None not Helpers.IsOnRightMachine(license_key):
         print("NOTE: This license file does not belong to this machine.")
     else:
         print("Feature 1: " + str(license_key.f1))
         print("License expires: " + str(license_key.expires))
 ```
+
+If you want to make sure that the license file is not too old, you can specify the maximum number of days as shown below (after 30 days, this method will return NoneType).
+
+```python
+# read license file from file
+with open('licensefile.skm', 'r') as f:
+    license_key = LicenseKey.load_from_string(pubKey, f.read(), 30)
+    
+    if license_key != None not Helpers.IsOnRightMachine(license_key):
+        print("NOTE: This license file does not belong to this machine.")
+    else:
+        print("Feature 1: " + str(license_key.f1))
+        print("License expires: " + str(license_key.expires))
+```
+
+### Floating licenses
+[Floating licenses](https://help.cryptolens.io/licensing-models/floating) can be enabled by setting the floatingTimeInterval. Optionally, you can also allow customers to exceed the bound by specifying the maxOverdraft.
+
+The code below has a floatingTimeInterval of 300 seconds and maxOverdraft set to 1. To support floating licenses with overdraft, the call to `Helpers.IsOnRightMachine(license, true, true)` needs two boolean flags to be set to true.
+
+```python
+from licensing.models import *
+from licensing.methods import Key, Helpers
+
+pubKey = "<RSAKeyValue><Modulus>sGbvxwdlDbqFXOMlVUnAF5ew0t0WpPW7rFpI5jHQOFkht/326dvh7t74RYeMpjy357NljouhpTLA3a6idnn4j6c3jmPWBkjZndGsPL4Bqm+fwE48nKpGPjkj4q/yzT4tHXBTyvaBjA8bVoCTnu+LiC4XEaLZRThGzIn5KQXKCigg6tQRy0GXE13XYFVz/x1mjFbT9/7dS8p85n8BuwlY5JvuBIQkKhuCNFfrUxBWyu87CFnXWjIupCD2VO/GbxaCvzrRjLZjAngLCMtZbYBALksqGPgTUN7ZM24XbPWyLtKPaXF2i4XRR9u6eTj5BfnLbKAU5PIVfjIS+vNYYogteQ==</Modulus><Exponent>AQAB</Exponent></RSAKeyValue>"
+
+res = Key.activate(token="WyIyNjA1IiwiTjhZQUpIYXJPaVdBV0ozQUlKVC9tamdDbFZDRzhZRHpaU243L2R2eCJd",\
+                   rsa_pub_key=pubKey,\
+                   product_id=3349, key="MTMPW-VZERP-JZVNZ-SCPZM", \
+                   machine_code=Helpers.GetMachineCode(),\
+                   floating_time_interval=300,\
+                   max_overdraft=1)
+
+if res[0] == None or not Helpers.IsOnRightMachine(res[0], is_floating_license=True, allow_overdraft=True):
+    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))
+```

licensing/methods.py

@@ -78,7 +78,7 @@ def GetMachineCode():
 
         return HelperMethods.get_SHA256(":".join(res))
 
-    def IsOnRightMachine(license_key):
+    def IsOnRightMachine(license_key, is_floating_license = False, allow_overdraft=False):
 
         """
         Check if the device is registered with the license key.
@@ -89,10 +89,15 @@ def IsOnRightMachine(license_key):
         if license_key.activated_machines == None:
             return False
 
-        for act_machine in license_key.activated_machines:
-            
-            if current_mid == act_machine.Mid:
+        if is_floating_license:
+            if len(license_key.activated_machines) == 1 and \
+            (license_key.activated_machines[0].Mid[9:] == current_mid or \
+             allow_overdraft and license_key.activated_machines[0].Mid[19:] == current_mid):
                 return True
+        else:
+            for act_machine in license_key.activated_machines:
+                if current_mid == act_machine.Mid:
+                    return True
 
         return False
 

licensing/models.py

@@ -9,6 +9,7 @@
 import base64
 import datetime
 import copy
+import time
 
 from licensing.internal import HelperMethods
 
@@ -60,8 +61,6 @@ def from_response(response):
 
         obj = json.loads(base64.b64decode(response.license_key).decode('utf-8'))
 
-        
-        
         return LicenseKey(obj["ProductId"], obj["ID"], obj["Key"], datetime.datetime.fromtimestamp(obj["Created"]),\
                           datetime.datetime.fromtimestamp(obj["Expires"]), obj["Period"], obj["F1"], obj["F2"], \
                           obj["F3"], obj["F4"],obj["F5"],obj["F6"], obj["F7"], \
@@ -79,12 +78,16 @@ def save_as_string(self):
         res.pop("license_key", None)
         return json.dumps(res)
 
-    def load_from_string(rsa_pub_key, string):
+    def load_from_string(rsa_pub_key, string, signature_expiration_interval = -1):
         """
         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.
+        
+        :param signature_expiration_interval: If the license key was signed,
+        this method will check so that no more than "signatureExpirationInterval" 
+        days have passed since the last activation.
         """
 
         response = Response("","","","")
@@ -100,7 +103,14 @@ def load_from_string(rsa_pub_key, string):
             try:
                 pubKey = RSAPublicKey.from_string(rsa_pub_key)
                 if HelperMethods.verify_signature(response, pubKey):
-                    return LicenseKey.from_response(response)
+                    
+                    licenseKey = LicenseKey.from_response(response)
+                    
+                    if signature_expiration_interval > 0 and \
+                    (licenseKey.sign_date + datetime.timedelta(days=1*signature_expiration_interval) < datetime.datetime.utcnow()):
+                        return None
+                    
+                    return licenseKey
                 else:
                     return None
             except Exception:

setup.py

@@ -2,7 +2,7 @@
 setup(
   name = 'licensing',         # How you named your package folder (MyLib)
   packages = ['licensing'],   # Chose the same as "name"
-  version = '0.4',      # Start with a small number and increase it with every change you make
+  version = '0.5',      # 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