Re: [web-devel] [Yesod] Re: Next version of WAI: cleaning house

24 Jul 2013

      What I'm looking for as far as use case is "I want to do X, and if you put
Y in the Request value, I could do X better." For example, "If I knew that
a request was insecure, I could automatically redirect to the secure URL."
My reasoning here is that, for all such use cases I've heard, determining
if it's a secure connection from the Request value is wrong. In this case,
you have to run two Warp servers anyway, one over HTTP and one over HTTPS.
So the more logical thing would be to just have two separate applications,
one with the redirect logic and one without.

And you're probably right; I can't think of any handlers that can't
determine if they were connected to securely. But again, my concern is
about including misleading information in Request which, given its lack of
reliability, can't really be used. If there *are* real use cases that I'm
not thinking of, that's a different story.

On Wed, Jul 24, 2013 at 6:36 PM, davean  wrote:
...
I explicitly described a scenario in my email. Can you tell me more about
what you want me to describe? Unless you consider my Vault alternative as
not in the Request.
Not sure what backend couldn't reliably tell whether *it* was connected to
securely. None can make claims about other steps in the chain (Which is
also exactly why we need this value).
-davean
On Wed, Jul 24, 2013 at 11:29 AM, Michael Snoyman wrote:
...
My concern is that, by throwing in as much information as possible in
Request, we'll essentially be diluting the meaning of the values there. My
approach was to only include values in Request that can be reliably
reported by all backends, or at the very least would clearly be nonsense
for certain backends[1]. My big concern is making it easy to write
incorrect code. My question is: what is a concrete example where you would
want the isSecure field in Request? If you're talking about a case where
you're using warp-tls and no reverse proxies, then you can tell your
application (via a config parameter, for example) that this is the case.
Maybe I just don't have the right mental model for what people are
expecting for WAI. I want to understand the use cases better, so please
keep up the discussion :).
[1] Example: wai-test clearly has to provide a fake IP address for the
remote end of the connection.
On Wed, Jul 24, 2013 at 6:10 PM, davean  wrote:
...
Clients directly accessing the server also makes sense when you have
tens of thousands of open connections at a time (that would be me). The
proxy overhead is just silly.
As for HTTPS, isSecure is interesting when using something like warp-tls
so as to handle insecure connections more elegantly. While the server can't
know about if a proxy received a secure connection it can know if it did.
This is even interesting when using a proxy since if the proxy is on
another system it should still connect with HTTPS for a large number of
threat models. Of course one may put that in the Vault.
And don't forget CDN updates where connections that were being sent as
HTTPS start being sent as HTTP due to the CDN operator's error. Perhaps you
still want to serve most connections when they come in as HTTP from the
CDN, send a warning to the ops team, and deny some requests as too
sensitive? Plenty of cases here.
This isn't about the entire history of the connection, it is about
conveying the webserver's information to the app so the app writer can make
appropriate choices to figure out what the history actually is given their
specific situation.
-davean
PS: The below happens BTW:
client <-> their work's proxy <-> their ISP's proxy <-> CDN <->
provider's proxy <-> final HTTP server
That is forwarded 4 times. Of course someone in there can also be lying.
I've even seen some pretty clever goes at forging X-Forward-Fors through
(or around) proxies.
On Wed, Jul 24, 2013 at 9:59 AM, Federico Mastellone wrote:
...
Wai should provide "a common protocol for communication between web
applications and web servers.", using proxies, load balancers or not. I
use Wai in a small setup (measured by clients), where clients access the
server directly. I was even going to request support for client
certificates.
Because some fields are unknown when running behind Amazon ELB I don't
think they should be taken out of the Wai interface. In that case, that
fields could be Nothing, False, etc. I think it would be great to write an
Application that can be run with any Wai compatible server, and maybe later
warp supports this fields behind a reverse proxy.
On 24/07/2013, at 09:23, Michael Snoyman  wrote:
On Wed, Jul 24, 2013 at 3:08 PM, Kazu Yamamoto  wrote:
...
Michael,
...
I'm definitely not talking about removing the peer information.
Request has
a remoteHost field which is of type SockAddr, and therefore provides
both
remote IP address and port number (the latter, as you mention, being
mostly
useless).
Please understand that I'm not opposing your opinion. I'm just trying
to interpret user's opinions.
I appreciate the input, I just wanted to clarify my proposal.
...
...
I'm not sure what you mean by telling if communication is encrypted
using
the headers + IP address, can you clarify?
Suppose a Yesod application receives X-Forwarded-For:.
A bad client can insert X-Forwarded-For:. But if an IP address is
provided and the application knows the IP address of the proxy, the
application can tell whether or not the IP address can be trusted.
I'm not sure that there is a standard header field to tell HTTPS.
But if the proxy and the application shares such field:
- The application can truct the field according peer's IP address
- The application can tell the outside HTTP is encrypted
Correct me if I misunderstand.
I'd never considered checking the IP address of the proxy. When I've
used X-Forwarded-For, I've always made sure to set up a firewall to ensure
the *only* connections come from the reverse proxy, and then
x-forwarded-for can be trusted.
As far as determining secure/insecure, it seems like Amazon's ELB sets
x-forwarded-proto[1]. Not sure if that's a well accepted standard, but it
seems useful.
Michael
[1]
http://docs.aws.amazon.com/ElasticLoadBalancing/latest/DeveloperGuide/Termin...
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