Istio allow only specific IP CIDR and deny rest - istio

Question

I have a requirement where-in I would like to allow certain CIDR ranges to be able to access my service, rest all should be denied.
I have tried the Istio IP Whitelisting/Blacklisting as mentioned in the official Istio documentation.
For example 10.0.0.2/16 should get allowed and rest should be denied. This doesn't seem to work.
apiVersion: config.istio.io/v1alpha2
kind: handler
metadata:
name: whitelistip
spec:
compiledAdapter: listchecker
params:
# providerUrl: ordinarily black and white lists are maintained
# externally and fetched asynchronously using the providerUrl.
overrides: ["10.0.0.2/16"] # overrides provide a static list
blacklist: true
entryType: IP_ADDRESSES
---
apiVersion: config.istio.io/v1alpha2
kind: instance
metadata:
name: sourceip
spec:

Answer 1

So basically the istio 1.5.0 was released few days ago and if we check the istio docs white/black list are deprecated now.
Denials and White/Black Listing (Deprecated)
But there is actually a good news because there is new example for authorization on ingress gateway which should answer your question.
I am not able to get the real client IP hence not able to block/allow using authorization policy or IP based whitelisting.
Based on this new example which I tested myself if you want to see you'r source ip you have to change istio-ingressgateway externalTrafficPolicy from Cluster to Local.
Update the ingress gateway to set externalTrafficPolicy: local to preserve the original client source IP on the ingress gateway using the following command:
kubectl patch svc istio-ingressgateway -n istio-system -p '{"spec":{"externalTrafficPolicy":"Local"}}'
And the allow example
The following example creates the authorization policy, ingress-policy, for the Istio ingress gateway. The following policy sets the action field to ALLOW to allow the IP addresses specified in the ipBlocks to access the ingress gateway. IP addresses not in the list will be denied. The ipBlocks supports both single IP address and CIDR notation.
apiVersion: security.istio.io/v1beta1
kind: AuthorizationPolicy
metadata:
name: ingress-policy
namespace: istio-system
spec:
selector:
matchLabels:
app: istio-ingressgateway
action: ALLOW
rules:
- from:
- source:
ipBlocks: ["1.2.3.4", "5.6.7.0/24", "$CLIENT_IP"]
I hope this answer your question. Let me know if you have any more questions.

Answer 2

Other solution in Istio 1.5:
Configure external traffic:
kubectl patch svc istio-ingressgateway -n istio-system -p '{"spec":{"externalTrafficPolicy":"Local"}}'
Or in Helm installation:
--set gateways.istio-ingressgateway.externalTrafficPolicy
And you can use in any namespace like this:
apiVersion: security.istio.io/v1beta1
kind: AuthorizationPolicy
metadata:
name: whitelist
namespace: foo
spec:
action: ALLOW
rules:
- from:
- source:
namespaces: ["istio-system"]
when:
- key: request.headers[X-Envoy-External-Address]
values: ["1.2.3.4/24"] #Ip to allow
selector:
matchLabels:
app: httpbin