Improve IPv6 validation (#201)

* Improve IPv6 validation
fixes #107

* Add some comments

* Fix ipv4 with double colon

* Fix falsy to long ipv6 result and detect to long parts

* Check for length

* Take empty parts in account

* Reduce length calculation

tests/test_ipv6.py

@@ -5,11 +5,15 @@
 
 
 @pytest.mark.parametrize(('address',), [
+    ('::',),
     ('::1',),
-    ('dead:beef:0:0:0:0:42:1',),
+    ('1::',),
+    ('dead:beef:0:0:0:0000:42:1',),
     ('abcd:ef::42:1',),
     ('0:0:0:0:0:ffff:1.2.3.4',),
     ('::192.168.30.2',),
+    ('0000:0000:0000:0000:0000::',),
+    ('0:a:b:c:d:e:f::',),
 ])
 def test_returns_true_on_valid_ipv6_address(address):
     assert ipv6(address)
@@ -20,7 +24,19 @@ def test_returns_true_on_valid_ipv6_address(address):
     ('abc.0.0.1',),
     ('abcd:1234::123::1',),
     ('1:2:3:4:5:6:7:8:9',),
+    ('1:2:3:4:5:6:7:8::',),
+    ('1:2:3:4:5:6:7::8:9',),
     ('abcd::1ffff',),
+    ('1111:',),
+    (':8888',),
+    (':1.2.3.4',),
+    ('18:05',),
+    (':',),
+    (':1:2:',),
+    (':1:2::',),
+    ('::1:2::',),
+    ('8::1:2::9',),
+    ('02001:0000:1234:0000:0000:C1C0:ABCD:0876',),
 ])
 def test_returns_failed_validation_on_invalid_ipv6_address(address):
     assert isinstance(ipv6(address), ValidationFailure)

validators/ip_address.py

@@ -4,7 +4,7 @@
 @validator
 def ipv4(value):
     """
-    Return whether or not given value is a valid IP version 4 address.
+    Return whether a given value is a valid IP version 4 address.
 
     This validator is based on `WTForms IPAddress validator`_
 
@@ -32,7 +32,7 @@ def ipv4(value):
 @validator
 def ipv4_cidr(value):
     """
-    Return whether or not given value is a valid CIDR-notated IP version 4
+    Return whether a given value is a valid CIDR-notated IP version 4
     address range.
 
     This validator is based on RFC4632 3.1.
@@ -57,7 +57,7 @@ def ipv4_cidr(value):
 @validator
 def ipv6(value):
     """
-    Return whether or not given value is a valid IP version 6 address
+    Return whether a given value is a valid IP version 6 address
     (including IPv4-mapped IPv6 addresses).
 
     This validator is based on `WTForms IPAddress validator`_.
@@ -95,10 +95,6 @@ def ipv6(value):
     else:
         ipv4_groups = []
 
-    max_groups = 6 if ipv4_groups else 8
-    if len(ipv6_groups) > max_groups:
-        return False
-
     count_blank = 0
     for part in ipv6_groups:
         if not part:
@@ -109,20 +105,32 @@ def ipv6(value):
         except ValueError:
             return False
         else:
-            if not 0 <= num <= 65536:
+            if not 0 <= num <= 65536 or len(part) > 4:
                 return False
 
-    if count_blank < 2:
+    max_groups = 6 if ipv4_groups else 8
+    part_count = len(ipv6_groups) - count_blank
+    if count_blank == 0 and part_count == max_groups:
+        # no :: -> must have size of max_groups
+        return True
+    elif count_blank == 1 and ipv6_groups[-1] and ipv6_groups[0] and part_count < max_groups:
+        # one :: inside the address or prefix or suffix : -> filter least two cases
+        return True
+    elif count_blank == 2 and part_count < max_groups and (
+            ((ipv6_groups[0] and not ipv6_groups[-1]) or (not ipv6_groups[0] and ipv6_groups[-1])) or ipv4_groups):
+        # leading or trailing :: or : at end and begin -> filter last case
+        # Check if it has ipv4 groups because they get removed from the ipv6_groups
         return True
-    elif count_blank == 2 and not ipv6_groups[0] and not ipv6_groups[1]:
+    elif count_blank == 3 and part_count == 0:
+        # :: is the address -> filter everything else
         return True
     return False
 
 
 @validator
 def ipv6_cidr(value):
     """
-    Returns whether or not given value is a valid CIDR-notated IP version 6
+    Returns whether a given value is a valid CIDR-notated IP version 6
     address range.
 
     This validator is based on RFC4632 3.1.