Add validate method on JsonPatch

[lordofthejars]

Because of the nature of patch (a list of operations to be applied), you need to validate that these operations are valid and you don't receive an unwanted operation.

For example suppose you are implementing a change password. This change password requires two things, the new password, the old password and the answer to a personal question. So json patch could be something like:

[
     { "op": "test", "path": "/password", "value": "myencryptedpassword" },
     { "op": "test", "path": "/answer", "value": "myanswer" }
     { "op": "replace", "path": "/password", "value": "newpassword" }
]

But of course nobody can avoid that someone send this:

[
     { "op": "replace", "path": "/username", "value": "hahaIhavechangedyourname" }
     { "op": "test", "path": "/password", "value": "myencryptedpassword" },
     { "op": "test", "path": "/answer", "value": "myanswer" }
     { "op": "replace", "path": "/password", "value": "newpassword" }
]

To avoid this a new method could me implemented called for example validate which can receive a "functional interface" to be implemented which have a method called validate with a parameter which is a list of operations to be done (list of { "op": "replace", "path": "/username", "value": "hahaIhavechangedyourname" }). In this way before applying the changes, the developer may be free to call validate or not. What I mean is that validate method could be executed automatically or not. Also we can overload JsonPatch.fromJson method setting the "functional interface" so then automatically validate method will be called automatically before executing apply.

I think it has a lot of sense allowing this kind of operations in sake of security.

WDYT?

[fge]

Hmm, I'm not really sure. First of all, I don't really know the context you are working in; it seems strange to me that you would have to check that a patch is valid for such a sensitive operation (I mean, you have the encrypted password strings in it, it means it must come from a pretty sensible source already?).

Also, are you really working purely with JSON, with no {de,}serialization? If you deserialize the patched JSON (to a new POJO, of course) you could detect anomalies immediately.

And, well, there is also the solution of using JSON Schema, but if you find guava heavy as a dependency, you'll have a heart attack when you see what that project depends on :p

[lordofthejars]

hehehe well I was thinking a way to validate that a client cannot send me a bunch of unwanted patch operations which can compromise an entity.

For example imagine I want to add a patch operation that it should test some attribute only, but the client send me a test operation along with a replace operation, this should be detected and avoided. It is not about sensitive data but about protecting from unwanted operations. Of course I could {de}serialize the json to POJO and detect it, but I was only thinking about making more general for all users.

I will take a look to json-schema-validator because it can be interesting to know exactly what it can do in the sense of protecting us from unwanted operations, data, ...

[fge]

FWIW, I have written a JSON Schema for JSON Patch quite some time ago: https://github.com/fge/json-schema-validator

And I am the author of the current validation draft, so of course I'll push my baby around :p

[lordofthejars]

Yes maybe as you said I need to close this issue.

[mohammeds1992]

Can u please point out an example how https://github.com/fge/json-schema-validator
can be used to ignore some of the fields while Patch