In affected releases of gRPC-Go, it is possible for an attacker to send HTTP/2 requests, cancel them, and send subsequent requests, which is valid by the HTTP/2 protocol, but would cause the gRPC-Go server to launch more concurrent method handlers than the configured maximum stream limit.
Patches
This vulnerability was addressed by #6703 and has been included in patch releases: 1.56.3, 1.57.1, 1.58.3. It is also included in the latest release, 1.59.0.
Along with applying the patch, users should also ensure they are using the grpc.MaxConcurrentStreams server option to apply a limit to the server's resources used for any single connection.
The HTTP/2 protocol allows clients to indicate to the server that a previous stream should be canceled by sending a RST_STREAM frame. The protocol does not require the client and server to coordinate the cancellation in any way, the client may do it unilaterally. The client may also assume that the cancellation will take effect immediately when the server receives the RST_STREAM frame, before any other data from that TCP connection is processed.
Abuse of this feature is called a Rapid Reset attack because it relies on the ability for an endpoint to send a RST_STREAM frame immediately after sending a request frame, which makes the other endpoint start working and then rapidly resets the request. The request is canceled, but leaves the HTTP/2 connection open.
The HTTP/2 Rapid Reset attack built on this capability is simple: The client opens a large number of streams at once as in the standard HTTP/2 attack, but rather than waiting for a response to each request stream from the server or proxy, the client cancels each request immediately.
The ability to reset streams immediately allows each connection to have an indefinite number of requests in flight. By explicitly canceling the requests, the attacker never exceeds the limit on the number of concurrent open streams. The number of in-flight requests is no longer dependent on the round-trip time (RTT), but only on the available network bandwidth.
In a typical HTTP/2 server implementation, the server will still have to do significant amounts of work for canceled requests, such as allocating new stream data structures, parsing the query and doing header decompression, and mapping the URL to a resource. For reverse proxy implementations, the request may be proxied to the backend server before the RST_STREAM frame is processed. The client on the other hand paid almost no costs for sending the requests. This creates an exploitable cost asymmetry between the server and the client.
Multiple software artifacts implementing HTTP/2 are affected. This advisory was originally ingested from the swift-nio-http2 repo advisory and their original conent follows.
swift-nio-http2 specific advisory
swift-nio-http2 is vulnerable to a denial-of-service vulnerability in which a malicious client can create and then reset a large number of HTTP/2 streams in a short period of time. This causes swift-nio-http2 to commit to a large amount of expensive work which it then throws away, including creating entirely new Channels to serve the traffic. This can easily overwhelm an EventLoop and prevent it from making forward progress.
swift-nio-http2 1.28 contains a remediation for this issue that applies reset counter using a sliding window. This constrains the number of stream resets that may occur in a given window of time. Clients violating this limit will have their connections torn down. This allows clients to continue to cancel streams for legitimate reasons, while constraining malicious actors.
Release Notes
grpc/grpc-go (google.golang.org/grpc)
### [`v1.58.3`](https://togithub.com/grpc/grpc-go/releases/tag/v1.58.3)
[Compare Source](https://togithub.com/grpc/grpc-go/compare/v1.58.2...v1.58.3)
### Security
- server: prohibit more than MaxConcurrentStreams handlers from running at once (CVE-2023-44487)
In addition to this change, applications should ensure they do not leave running tasks behind related to the RPC before returning from method handlers, or should enforce appropriate limits on any such work.
### [`v1.58.2`](https://togithub.com/grpc/grpc-go/releases/tag/v1.58.2): Release 1.58.2
[Compare Source](https://togithub.com/grpc/grpc-go/compare/v1.58.1...v1.58.2)
### Bug Fixes
- balancer/weighted_round_robin: fix ticker leak on update
A new ticker is created every time there is an update of addresses or configuration, but was not properly stopped. This change stops the ticker when it is no longer needed.
Configuration
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This PR contains the following updates:
v1.58.1->v1.58.3GitHub Vulnerability Alerts
GHSA-m425-mq94-257g
Impact
In affected releases of gRPC-Go, it is possible for an attacker to send HTTP/2 requests, cancel them, and send subsequent requests, which is valid by the HTTP/2 protocol, but would cause the gRPC-Go server to launch more concurrent method handlers than the configured maximum stream limit.
Patches
This vulnerability was addressed by #6703 and has been included in patch releases: 1.56.3, 1.57.1, 1.58.3. It is also included in the latest release, 1.59.0.
Along with applying the patch, users should also ensure they are using the
grpc.MaxConcurrentStreamsserver option to apply a limit to the server's resources used for any single connection.Workarounds
None.
References
6703
CVE-2023-44487
HTTP/2 Rapid reset attack
The HTTP/2 protocol allows clients to indicate to the server that a previous stream should be canceled by sending a RST_STREAM frame. The protocol does not require the client and server to coordinate the cancellation in any way, the client may do it unilaterally. The client may also assume that the cancellation will take effect immediately when the server receives the RST_STREAM frame, before any other data from that TCP connection is processed.
Abuse of this feature is called a Rapid Reset attack because it relies on the ability for an endpoint to send a RST_STREAM frame immediately after sending a request frame, which makes the other endpoint start working and then rapidly resets the request. The request is canceled, but leaves the HTTP/2 connection open.
The HTTP/2 Rapid Reset attack built on this capability is simple: The client opens a large number of streams at once as in the standard HTTP/2 attack, but rather than waiting for a response to each request stream from the server or proxy, the client cancels each request immediately.
The ability to reset streams immediately allows each connection to have an indefinite number of requests in flight. By explicitly canceling the requests, the attacker never exceeds the limit on the number of concurrent open streams. The number of in-flight requests is no longer dependent on the round-trip time (RTT), but only on the available network bandwidth.
In a typical HTTP/2 server implementation, the server will still have to do significant amounts of work for canceled requests, such as allocating new stream data structures, parsing the query and doing header decompression, and mapping the URL to a resource. For reverse proxy implementations, the request may be proxied to the backend server before the RST_STREAM frame is processed. The client on the other hand paid almost no costs for sending the requests. This creates an exploitable cost asymmetry between the server and the client.
Multiple software artifacts implementing HTTP/2 are affected. This advisory was originally ingested from the
swift-nio-http2repo advisory and their original conent follows.swift-nio-http2 specific advisory
swift-nio-http2 is vulnerable to a denial-of-service vulnerability in which a malicious client can create and then reset a large number of HTTP/2 streams in a short period of time. This causes swift-nio-http2 to commit to a large amount of expensive work which it then throws away, including creating entirely new
Channels to serve the traffic. This can easily overwhelm anEventLoopand prevent it from making forward progress.swift-nio-http2 1.28 contains a remediation for this issue that applies reset counter using a sliding window. This constrains the number of stream resets that may occur in a given window of time. Clients violating this limit will have their connections torn down. This allows clients to continue to cancel streams for legitimate reasons, while constraining malicious actors.
Release Notes
grpc/grpc-go (google.golang.org/grpc)
### [`v1.58.3`](https://togithub.com/grpc/grpc-go/releases/tag/v1.58.3) [Compare Source](https://togithub.com/grpc/grpc-go/compare/v1.58.2...v1.58.3) ### Security - server: prohibit more than MaxConcurrentStreams handlers from running at once (CVE-2023-44487) In addition to this change, applications should ensure they do not leave running tasks behind related to the RPC before returning from method handlers, or should enforce appropriate limits on any such work. ### [`v1.58.2`](https://togithub.com/grpc/grpc-go/releases/tag/v1.58.2): Release 1.58.2 [Compare Source](https://togithub.com/grpc/grpc-go/compare/v1.58.1...v1.58.2) ### Bug Fixes - balancer/weighted_round_robin: fix ticker leak on update A new ticker is created every time there is an update of addresses or configuration, but was not properly stopped. This change stops the ticker when it is no longer needed.Configuration
📅 Schedule: Branch creation - "" (UTC), Automerge - At any time (no schedule defined).
🚦 Automerge: Disabled by config. Please merge this manually once you are satisfied.
â™» Rebasing: Never, or you tick the rebase/retry checkbox.
🔕 Ignore: Close this PR and you won't be reminded about this update again.
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