Gateway server panics on invalid Grpc-Timeout value

[alkapov]

🐛 Bug Report

Server panics when receives request with invalid Grpc-Timeout value.

Let's consider following code from example:

grpc-gateway/examples/internal/proto/examplepb/echo_service.pb.gw.go

Lines 905 to 909 in 1911ac0

	ctx, err = runtime.AnnotateIncomingContext(ctx, mux, req, "/grpc.gateway.examples.internal.proto.examplepb.EchoService/EchoBody", runtime.WithHTTPPathPattern("/v1/example/echo_body"))
	if err != nil {
	runtime.HTTPError(ctx, mux, outboundMarshaler, w, req, err)
	return
	}

runtime.AnnotateIncomingContext may return ctx == nil if err != nil.
But then ctx is passed into runtime.HTTPError(ctx, ...), which in default case calls runtime.DefaultHTTPErrorHandler(ctx, ...), which calls ServerMetadataFromContext(ctx).

The latter tries to get value from that context and panics, given that the context is nil.

grpc-gateway/runtime/context.go

Lines 185 to 188 in 1911ac0

	func ServerMetadataFromContext(ctx context.Context) (md ServerMetadata, ok bool) {
	md, ok = ctx.Value(serverMetadataKey{}).(ServerMetadata)
	return
	}

To Reproduce

1. Clone repo at last revision (tested rev: 1911ac0).
2. Run servers:
   • go run examples/internal/cmd/example-grpc-server/main.go
   • go run examples/internal/cmd/example-gateway-server/main.go
3. Ensure that everything is OK.

   $ curl --location --request POST 'http://127.0.0.1:8080/v1/example/echo_body' \
     --header 'Grpc-Timeout: 1S' \
     --header 'Content-Type: application/json' \
     --data-raw '{"num": 1}'
   # returns
   {"id":"", "num":"1", "status":null}

4. Invalidate Grpc-Timeout and call again.

   $ curl --location --request POST 'http://127.0.0.1:8080/v1/example/echo_body' \
     --header 'Grpc-Timeout: INVALID' \
     --header 'Content-Type: application/json' \
     --data-raw '{"num": 1}'
   # fails
   curl: (52) Empty reply from server

Server log:

2022/07/29 17:34:44 http: panic serving 127.0.0.1:58784: runtime error: invalid memory address or nil pointer dereference
goroutine 30 [running]:
net/http.(*conn).serve.func1()
	/opt/homebrew/Cellar/go/1.18.4/libexec/src/net/http/server.go:1825 +0xb0
panic({0x102d7c8e0, 0x1031ad1a0})
	/opt/homebrew/Cellar/go/1.18.4/libexec/src/runtime/panic.go:844 +0x258
github.com/grpc-ecosystem/grpc-gateway/v2/runtime.ServerMetadataFromContext(...)
	/dev/src/github.com/grpc-ecosystem/grpc-gateway/runtime/context.go:186
github.com/grpc-ecosystem/grpc-gateway/v2/runtime.DefaultHTTPErrorHandler({0x0, 0x0}, 0x14000147508?, {0x102e2c6e0, 0x1031acfa0}, {0x102e2b920?, 0x14000276700}, 0x2?, {0x102e27a28, 0x14000132418})
	/dev/src/github.com/grpc-ecosystem/grpc-gateway/runtime/errors.go:125 +0x50c
github.com/grpc-ecosystem/grpc-gateway/v2/runtime.HTTPError(...)
	/dev/src/github.com/grpc-ecosystem/grpc-gateway/runtime/errors.go:81
github.com/grpc-ecosystem/grpc-gateway/v2/examples/internal/proto/examplepb.RegisterEchoServiceHandlerClient.func6({0x102e2b920, 0x14000276700}, 0x14000240400, 0x14000123000?)
	/dev/src/github.com/grpc-ecosystem/grpc-gateway/examples/internal/proto/examplepb/echo_service.pb.gw.go:1171 +0x278
github.com/grpc-ecosystem/grpc-gateway/v2/runtime.(*ServeMux).ServeHTTP(0x140001b4600, {0x102e2b920, 0x14000276700}, 0x14000240400)
	/dev/src/github.com/grpc-ecosystem/grpc-gateway/runtime/mux.go:386 +0xd8c
net/http.(*ServeMux).ServeHTTP(0x14000251770?, {0x102e2b920, 0x14000276700}, 0x14000240400)
	/opt/homebrew/Cellar/go/1.18.4/libexec/src/net/http/server.go:2462 +0x144
github.com/grpc-ecosystem/grpc-gateway/v2/examples/internal/gateway.allowCORS.func1({0x102e2b920, 0x14000276700}, 0x14000240400)
	/dev/src/github.com/grpc-ecosystem/grpc-gateway/examples/internal/gateway/handlers.go:41 +0x1b8
net/http.HandlerFunc.ServeHTTP(0x0?, {0x102e2b920?, 0x14000276700?}, 0x10277e0d0?)
	/opt/homebrew/Cellar/go/1.18.4/libexec/src/net/http/server.go:2084 +0x3c
net/http.serverHandler.ServeHTTP({0x102e2a758?}, {0x102e2b920, 0x14000276700}, 0x14000240400)
	/opt/homebrew/Cellar/go/1.18.4/libexec/src/net/http/server.go:2916 +0x3fc
net/http.(*conn).serve(0x14000274280, {0x102e2be48, 0x14000250870})
	/opt/homebrew/Cellar/go/1.18.4/libexec/src/net/http/server.go:1966 +0x56c
created by net/http.(*Server).Serve
	/opt/homebrew/Cellar/go/1.18.4/libexec/src/net/http/server.go:3071 +0x450

Expected behavior

Server should return error like that:

{
    "code": 3,
    "message": "invalid grpc-timeout: INVALID",
    "details": []
}

Actual Behavior

Server panics, no response returned.

Your Environment

macOS 12.4
go version go1.18.4 darwin/arm64
repo revision 1911ac0

[johanbrandhorst]

Thank you for this bug report. I consider this a very bad bug so I've gone ahead and submitted a double fix myself in #2823.

[johanbrandhorst]

We've released a fix for this in https://github.com/grpc-ecosystem/grpc-gateway/releases/tag/v2.11.1