This change fully addresses CVE-2023-44487 and CVE-2023-39325 for
the API server when the client is unauthenticated.
The changes to util/runtime are required because otherwise a large
number of requests can get blocked on the time.Sleep calls.
For unauthenticated clients (either via 401 or the anonymous user),
we simply no longer allow such clients to hold open http2
connections. They can use http2, but with the performance of http1
(with keep-alive disabled).
Since this change has the potential to cause issues, the
UnauthenticatedHTTP2DOSMitigation feature gate can be disabled to
remove this protection (it is enabled by default). For example,
when the API server is fronted by an L7 load balancer that is set up
to mitigate http2 attacks, unauthenticated clients could force
disable connection reuse between the load balancer and the API
server (many incoming connections could share the same backend
connection). An API server that is on a private network may opt to
disable this protection to prevent performance regressions for
unauthenticated clients.
For all other clients, we rely on the golang.org/x/net fix in
b225e7ca6d
That change is not sufficient to adequately protect against a
motivated client - future changes to Kube and/or golang.org/x/net
will be explored to address this gap.
The Kube API server now uses a max stream of 100 instead of 250
(this matches the Go http2 client default). This lowers the abuse
limit from 1000 to 400.
Signed-off-by: Monis Khan <mok@microsoft.com>
* Add warning handler callback function in shortcut expander
Currently, errors in client-go are propagated back to the callers via
function returns. However, there is no elegant way for just warning users.
For example, when user wants to get a resource with it's short name format
and if there are multiple resources belonging to this short name, we need to
warn user about this ambugity which one is picked and which ones are discarded.
Not only to overcome this particular case mentioned above, but also propose a
way for the possible warnings in the future, this commit adds a warningHandler
callback function in shortcutExpander.
* Add warningPrinter functionality in ConfigFlags
ConfigFlags has neither warning user in a standardized
format functionality nor passing warning callback functions to other upper level
libraries such as client-go.
This commit adds an ability that user can set warningPrinters
according to their IOStreams and this warningPrinters will be used
to raise possible warnings happening not only in cli-runtime but
also in client-go.
* Pass warning callback function in ConfigFlags to shortcutExpander
This commit passes warning callback function to print possible
warnings happened in shortcut expander to warn user in a
standardized format.
* Add integration test for CRDs having ambiguous short names
This commit adds integration test to assure that warning message
related to this ambiguity is printed when resources are being retrieved via their short name
representations in cases where multiple resources have same
short names.
This integration test also ensures that the logic behind which resource
will be selected hasn't been changed which may cause disperancies in
clusters.
* Remove defaultConfigFlag global variable
* Move default config flags initialization into function
* Skip warning for versions of same group/resource
* Run update-vendor
* Warn only once when there are multiple versions registered for ambiguous resource
* Apply gocritic review
* Add multi-resource multi-version ambiguity unit test
