feat(BREAKING): Change CIDRIPv4 validation (#945)

## Fixes Or Enhances

- Mentions #909 
- Disable validation of cidripv4 when ip is not the begining of the
block

Co-authored-by: Martin Kagamino Lehoux <[email protected]>
Co-authored-by: Dean Karn <[email protected]>

Author: 3 people

baked_in.go

@@ -373,9 +373,9 @@ func isMAC(fl FieldLevel) bool {
 
 // isCIDRv4 is the validation function for validating if the field's value is a valid v4 CIDR address.
 func isCIDRv4(fl FieldLevel) bool {
-	ip, _, err := net.ParseCIDR(fl.Field().String())
+	ip, net, err := net.ParseCIDR(fl.Field().String())
 
-	return err == nil && ip.To4() != nil
+	return err == nil && ip.To4() != nil && net.IP.Equal(ip)
 }
 
 // isCIDRv6 is the validation function for validating if the field's value is a valid v6 CIDR address.

validator_test.go

@@ -2575,19 +2575,26 @@ func TestCIDRv4Validation(t *testing.T) {
 		param    string
 		expected bool
 	}{
-		{"10.0.0.0/0", true},
-		{"10.0.0.1/8", true},
-		{"172.16.0.1/16", true},
-		{"192.168.0.1/24", true},
-		{"192.168.255.254/24", true},
+		{"0.0.0.0/0", true},
+		{"10.0.0.0/0", false},
+		{"10.0.0.0/8", true},
+		{"10.0.0.1/8", false},
+		{"172.16.0.0/16", true},
+		{"172.16.0.1/16", false},
+		{"192.168.0.0/24", true},
+		{"192.168.0.1/24", false},
+		{"192.168.255.0/24", true},
+		{"192.168.255.254/24", false},
 		{"192.168.255.254/48", false},
 		{"192.168.255.256/24", false},
-		{"172.16.255.254/16", true},
+		{"172.16.0.0/16", true},
+		{"172.16.255.254/16", false},
 		{"172.16.256.255/16", false},
 		{"2001:cdba:0000:0000:0000:0000:3257:9652/64", false},
 		{"2001:cdba:0000:0000:0000:0000:3257:9652/256", false},
 		{"2001:cdba:0:0:0:0:3257:9652/32", false},
 		{"2001:cdba::3257:9652/16", false},
+		{"172.56.1.0/16", false},
 	}
 
 	validate := New()