net/http, x/net/http2: rapid stream resets can cause excessive work (CVE-2023-39325)

[neild]

A malicious HTTP/2 client which rapidly creates requests and
immediately resets them can cause excessive server resource consumption.
While the total number of requests is bounded to the
http2.Server.MaxConcurrentStreams setting, resetting an in-progress
request allows the attacker to create a new request while the existing
one is still executing.

HTTP/2 servers now bound the number of simultaneously executing
handler goroutines to the stream concurrency limit. New requests
arriving when at the limit (which can only happen after the client
has reset an existing, in-flight request) will be queued until a
handler exits. If the request queue grows too large, the server
will terminate the connection.

This issue is also fixed in golang.org/x/net/http2 v0.17.0,
for users manually configuring HTTP/2.

The default stream concurrency limit is 250 streams (requests)
per HTTP/2 connection. This value may be adjusted using the
golang.org/x/net/http2 package; see the Server.MaxConcurrentStreams
setting and the ConfigureServer function.

This is CVE-2023-39325 and Go issue https://go.dev/issue/63417.
This is also tracked by CVE-2023-44487.

---

This is a PRIVATE issue for CVE-2023-39325, tracked in http://b/303836512.

/cc @golang/security and @golang/release

[neild]

@gopherbot please open backport issues

[gopherbot]

Backport issue(s) opened: #63426 (for 1.20), #63427 (for 1.21).

Remember to create the cherry-pick CL(s) as soon as the patch is submitted to master, according to https://go.dev/wiki/MinorReleases.

[gopherbot]

Change https://go.dev/cl/534215 mentions this issue: http2: limit maximum handler goroutines to MaxConcurrentStreams

[gopherbot]

Change https://go.dev/cl/534235 mentions this issue: [release-branch.go1.21] net/http: regenerate h2_bundle.go

[gopherbot]

Change https://go.dev/cl/534255 mentions this issue: [release-branch.go1.20] net/http: regenerate h2_bundle.go

[dmitshur]

Reopening to track bundling into the main tree, for Go 1.22.

[gopherbot]

Change https://go.dev/cl/534295 mentions this issue: all: pull in x/net v0.17.0 and its dependencies

[gopherbot]

Change https://go.dev/cl/534218 mentions this issue: [internal-branch.go1.21-vendor] http2: limit maximum handler goroutines to MaxConcurrentStreams

[gopherbot]

Change https://go.dev/cl/534236 mentions this issue: [internal-branch.go1.20-vendor] http2: limit maximum handler goroutines to MaxConcurrentStreams

[gopherbot]

Change https://go.dev/cl/534297 mentions this issue: [release-branch.go1.20] all: tidy dependency versioning after release

[gopherbot]

Change https://go.dev/cl/534415 mentions this issue: [release-branch.go1.21] all: tidy dependency versioning after release

[tuk2]

The issue with HTTP/2 rapid reset is still active. When an HTTP/2 server is attacked using rapid resets, it results in memory leaks (up to peak memory usage). This problem is especially noticeable when using net/http/httputil (reverse proxy). IMPORTANT: The memory leak occurs ONLY during rapid reset attacks.

[tuk2]

@bradfitz