RESTful and HTTP APIs in Pyramid Transcripts
Chapter: Authenticated services
Lecture: Isolating the API auth features

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0:01 As we saw, having all this header parsing, database querying, API
0:04 at the beginning of every one of our functions is super bad,
0:08 now we could slightly improve this by putting this into a function, right,
0:12 we could come over here and say extract a method
0:15 and if I grab the right stuff and it didn't really like these return values
0:18 I could store those values and check it, whatever, right,
0:22 I could make this work no problem.
0:24 But, we can do better than this,
0:26 so let's go add a new section of our web app here
0:29 let's go to infrastructure and over in this section,
0:32 we'll probably end up with a number of other things
0:35 but for now, let's just put a thing we're going to call auth.
0:38 And that method that we wrote, let's say def parse_api_key,
0:44 so let's break this into two things, request okay,
0:48 so let's go over here and cut this out for a minute,
0:54 so what do we have, we have auth header, again, spelling matters,
0:59 so we are going to get the authorization, if not this, we're going to return,
1:02 let's make a copy really quick of this,
1:07 so we're going to return none, no auth header.
1:10 Actually, I am wondering if we should maybe pass the error message back as well,
1:14 so let's go over here and say none and error is no auth header.
1:20 Let's go over here and say none, and the reason is invalid here
1:26 got to import this, this is going to be none and the reason is invalid auth key,
1:31 and then finally, here we're going to return a user,no error
1:35 so we're going to say given request let's go find the API key here,
1:41 so it has to live in authorization thing, there's none of that obviously
1:46 we have no user and the error is this, if it's invalid, no user error is this.
1:51 No user, no user and the error is this,
1:54 otherwise, we found these and there are no errors,
1:57 so that's how we're going to use this little bit here.
1:59 Now, we don't really need this anymore,
2:01 the next thing I want to do is I would like to be able to go over here
2:04 and just go something like this, at require auth, API auth, okay.
2:10 So what we're going to do is build a decorator,
2:14 just a basic decorator that we can wrap on this
2:16 and it's going to intercept the call here, and it won't even let it get to it,
2:20 if there's no authorization, right,
2:23 it's going to manage all the stuff that you saw us do,
2:25 and we go back here and turn this back off,
2:27 because we're not going to need this anymore,
2:30 instead we're going to have this
2:32 So, how do we do that? Let's start really simple,
2:35 so decorators are just functions, okay,
2:37 and decorators are just functions that take a function,
2:40 what function are they going to take, the thing that you put them before
2:43 so in our example here, if I say at this, let's be a little more explicit up here,
2:50 so let's say this, [typing code] import that as auth, okay,
3:01 so let's make it kind of explicit where it's coming from
3:04 @ auth.require.api_auth, okay,
3:06 so it's going to take this function
3:09 and that is a function that takes one thing, a request
3:12 and it returns a response, so we need to tell this thing to return a function
3:17 which takes a request and returns a response, right,
3:20 so I am going to come down here
3:23 and we'll have a def wrapped takes a request
3:27 and it returns some kind of response,
3:30 and often this will just be by delegating to this inner function,
3:35 this wrapped function here, I am going to need to return wrapped, without calling it,
3:40 now let's just do a print, before the wrapped func
3:45 and let's go ahead and try to print it here maybe it will tell us what it is func ;
3:49 okay, so do we have it over here, we do, and restart,
3:56 before the wrap function and here are all autos at this address perfect,
4:00 now did it work, did it still run— it did, look, down here at the bottom,
4:04 we've got all this stuff, and that part happened right here,
4:11 this is the actual execution of that API call.
4:14 So this before part came before, then right,
4:19 here's where we can do that validation
4:21 so we'll say user error equals parse api key with this request,
4:27 and we'll say if error then return response from pyramid
4:35 with a status just like before, 403, and the body being the error, like so.
4:44 Now, maybe this car, remember what we had up here
4:47 is we had a little print statement, print listing cars for
4:53 we give a name here, we said . format(
4:56 what is the user, what if we actually need to provide the user,
5:00 not just make sure they can call it or don't call it,
5:04 so we can do that step right here, before we call the function
5:07 but we have already verified there is a user, we can say request.api_user = user.
5:14 Now, we could plug into the pyramid all stuff and try to make that user
5:19 but I kind of feel like just making it super explicit like this is the user;
5:23 So let's go over here, you can choose to do that however you want
5:29 and this has to be
5:32 again put back request now that we want to use it
5:34 an the idea is, if this lets the function run there will be a user,
5:39 if there's no user, this function doesn't run,
5:41 so you don't need to worry about whether or not this is there,
5:44 right, it's going to be there; now let's try this again,
5:46 this should be awesome, are you ready?
5:49 I'm over here, who is our user, this is the authorization I believe I got it for jeff
5:52 and first of all, let's not send it, see what happens,
5:55 boom 403 forbidden no auth header,
5:59 so you could say like maybe a nicer message,
6:04 like you must specify an authorization header, something like this,
6:11 but whatever the error is, there is no auth header,
6:14 now if I pass it in, and maybe I get this wrong
6:17 I'll put an extra f on the end, first of all let's mess this up
6:20 make the api thing wrong, so it's invalid,
6:23 make it valid, now it's valid but the value corresponds to no user,
6:27 there's no user with that account, take the f off,
6:29 now, so notice, none of this crashed, right,
6:32 this was never run at all, because the outer shell was guarding it, right
6:41 this required auth API that we created is guarding it
6:44 now it should pass through that, and on the way through
6:47 it should set the API user to jeff, let's try—
6:50 boom, so it works fine over in our log files, well ''log files'', in our print
6:56 we have listing cars for jeff, what do you guys think, is that killer or what?
7:00 So just to review, we come over here, we wrote two functions
7:04 one that knows how to suck this authorization header apart,
7:07 break it into its pieces and give us the API key,
7:09 and then there's a very very simple decorator
7:12 that takes basically right here what turns out to be the thing that gets executed,
7:16 wrapping around the API call, it checks for the user
7:20 and if there's no user, return error, don't ever call the function,
7:24 but if it is good, set the API user and call the function.