Re: [quicwg/base-drafts] Import HTTP/2 Security Considerations (#3531)

[ianswett <[e-mail]>]

ianswett commented on this pull request.



> +the origin server in the Cache-Control header field. However, this can cause
+issues if a single server hosts more than one tenant.  For example, a server
+might offer multiple users each a small portion of its URI space.
+
+Where multiple tenants share space on the same server, that server MUST ensure
+that tenants are not able to push representations of resources that they do not
+have authority over.  Failure to enforce this would allow a tenant to provide a
+representation that would be served out of cache, overriding the actual
+representation that the authoritative tenant provides.
+
+Pushed responses for which an origin server is not authoritative (see
+{{connection-reuse}}) MUST NOT be used or cached.
+
+## Denial-of-Service Considerations
+
+An HTTP/3 connection can demand a greater commitment of resources to operate

I'm not sure I know why this would be true, particularly for HTTP/2 vs HTTP/3?

> +might be done by setting multiple undefined SETTINGS parameters, unknown frame
+types, or unknown stream types.  Note, however, that some uses are entirely
+legitimate, such as optional-to-understand extensions and padding to increase
+resistance to traffic analysis.
+
+Header compression also offers some opportunities to waste processing resources;
+see Section 7 of [QPACK] for more details on potential abuses.
+
+All these features -- i.e., server push, unknown protocol elements, field
+compression -- have legitimate uses.  These features become a burden only when
+they are used unnecessarily or to excess.
+
+An endpoint that doesn't monitor this behavior exposes itself to a risk of
+denial-of-service attack.  Implementations SHOULD track the use of these
+features and set limits on their use.  An endpoint MAY treat activity that is
+suspicious as a connection error ({{errors}}) of type H3_EXCESSIVE_LOAD.

It might be worth calling out that this could close valid connections and cause requests to fail?

> +All these features -- i.e., server push, unknown protocol elements, field
+compression -- have legitimate uses.  These features become a burden only when
+they are used unnecessarily or to excess.
+
+An endpoint that doesn't monitor this behavior exposes itself to a risk of
+denial-of-service attack.  Implementations SHOULD track the use of these
+features and set limits on their use.  An endpoint MAY treat activity that is
+suspicious as a connection error ({{errors}}) of type H3_EXCESSIVE_LOAD.
+
+### Limits on Field Section Size
+
+A large field section ({{request-response}}) can cause an implementation to
+commit a large amount of state.  Header fields that are critical for routing can
+appear toward the end of a header field section, which prevents streaming of the
+header field section to its ultimate destination.  This ordering and other
+reasons, such as ensuring cache correctness, mean that an endpoint might need to

In my experience, this is quite likely a requirement, not just a might.  So I'd be inclined to make this stronger(ie: "likely needs to..."

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