diff --git a/.github/workflows/tarball.yml b/.github/workflows/tarball.yml
new file mode 100644
index 0000000..fcf61e1
--- /dev/null
+++ b/.github/workflows/tarball.yml
@@ -0,0 +1,105 @@
+name: tarball
+
+on:
+  push:
+    branches: [ master ]
+    paths:
+      - '.github/workflows/build.yml'
+      - '**.go'
+      - 'go.*'
+      - 'Makefile'
+  pull_request:
+    branches: [ master ]
+    paths:
+      - '.github/workflows/build.yml'
+      - '**.go'
+      - 'go.*'
+      - 'Makefile'
+
+jobs:
+  create:
+    strategy:
+      matrix:
+        go-version:
+          - "1.17"
+          - "1.18"
+    runs-on: ubuntu-latest
+    steps:
+    - uses: actions/checkout@v3
+    - uses: actions/setup-go@v3
+      with:
+        go-version: ${{ matrix.go-version }}
+
+    - id: go-cache-paths
+      run: |
+        echo "::set-output name=go-build::$(go env GOCACHE)"
+        echo "::set-output name=go-mod::$(go env GOMODCACHE)"
+        echo "::set-output name=go-version::$(go version | cut -d ' ' -f 3)"
+
+    - name: Go build cache
+      uses: actions/cache@v3
+      with:
+        path: ${{ steps.go-cache-paths.outputs.go-build }}
+        key: ${{ runner.os }}-${{ steps.go-cache-paths.outputs.go-version }}-build-${{ hashFiles('**/go.mod', '**/go.sum') }}
+
+    - name: Go mod cache
+      uses: actions/cache@v3
+      with:
+        path: ${{ steps.go-cache-paths.outputs.go-mod }}
+        key: ${{ runner.os }}-${{ steps.go-cache-paths.outputs.go-version }}-mod-${{ hashFiles('**/go.mod', '**/go.sum') }}
+
+    - name: Install dependencies
+      run: |
+        sudo apt -y update && sudo apt -y install protobuf-compiler
+
+    - name: Create tarball
+      run: |
+        echo "Building with $(nproc) threads"
+        make tarball
+
+    - name: Upload tarball
+      uses: actions/upload-artifact@v2
+      with:
+        name: tarball-${{ matrix.go-version }}
+        path: nextcloud-spreed-signaling*.tar.gz
+
+  test:
+    strategy:
+      matrix:
+        go-version:
+          - "1.17"
+          - "1.18"
+    runs-on: ubuntu-latest
+    needs: [create]
+    steps:
+    - uses: actions/setup-go@v3
+      with:
+        go-version: ${{ matrix.go-version }}
+
+    - name: Install dependencies
+      run: |
+        sudo apt -y update && sudo apt -y install protobuf-compiler
+
+    - name: Download tarball
+      uses: actions/download-artifact@v2
+      with:
+        name: tarball-${{ matrix.go-version }}
+
+    - name: Extract tarball
+      run: |
+        mkdir -p tmp
+        tar xf nextcloud-spreed-signaling*.tar.gz --strip-components=1 -C tmp
+        [ -d "tmp/vendor" ] || exit 1
+
+    - name: Build
+      env:
+        GOPROXY: off
+      run: |
+        echo "Building with $(nproc) threads"
+        make -C tmp build -j$(nproc)
+
+    - name: Run tests
+      env:
+        GOPROXY: off
+      run: |
+        make -C tmp test
diff --git a/Makefile b/Makefile
index b9cc4f6..9065f6f 100644
--- a/Makefile
+++ b/Makefile
@@ -8,11 +8,14 @@ GOOS ?= linux
 GOARCH ?= amd64
 GOVERSION := $(shell "$(GO)" env GOVERSION | sed "s|go||" )
 BINDIR := "$(CURDIR)/bin"
+VENDORDIR := "$(CURDIR)/vendor"
 VERSION := $(shell "$(CURDIR)/scripts/get-version.sh")
 TARVERSION := $(shell "$(CURDIR)/scripts/get-version.sh" --tar)
 PACKAGENAME := github.com/strukturag/nextcloud-spreed-signaling
 ALL_PACKAGES := $(PACKAGENAME) $(PACKAGENAME)/client $(PACKAGENAME)/proxy $(PACKAGENAME)/server
 
+PROTOC_GEN_GRPC_VERSION := v1.2.0
+
 ifneq ($(VERSION),)
 INTERNALLDFLAGS := -X main.version=$(VERSION)
 else
@@ -53,15 +56,14 @@ hook:
 	[ ! -d "$(CURDIR)/.git/hooks" ] || ln -sf "$(CURDIR)/scripts/pre-commit.hook" "$(CURDIR)/.git/hooks/pre-commit"
 
 $(GOPATHBIN)/easyjson:
-	$(GO) get -u -d github.com/mailru/easyjson/...
+	[ "$(GOPROXY)" = "off" ] || $(GO) get -u -d github.com/mailru/easyjson/...
 	$(GO) install github.com/mailru/easyjson/...
 
 $(GOPATHBIN)/protoc-gen-go:
-	$(GO) get -u -d google.golang.org/protobuf/cmd/protoc-gen-go
 	$(GO) install google.golang.org/protobuf/cmd/protoc-gen-go
 
 $(GOPATHBIN)/protoc-gen-go-grpc:
-	$(GO) get -u -d google.golang.org/grpc/cmd/protoc-gen-go-grpc
+	[ "$(GOPROXY)" = "off" ] || $(GO) get -u -d google.golang.org/grpc/cmd/protoc-gen-go-grpc
 	$(GO) install google.golang.org/grpc/cmd/protoc-gen-go-grpc
 
 continentmap.go:
@@ -143,13 +145,34 @@ clean:
 
 build: server proxy
 
-tarball:
+vendor: go.mod go.sum common
+	set -e ;\
+	rm -rf $(VENDORDIR)
+	EASYJSON_DIR=$$($(GO) list -m -f '{{.Dir}}' github.com/mailru/easyjson); \
+	PROTOBUF_DIR=$$($(GO) list -m -f '{{.Dir}}' google.golang.org/protobuf); \
+	$(GO) mod tidy; \
+	$(GO) mod vendor; \
+	mkdir -p $(VENDORDIR)/github.com/mailru/easyjson/; \
+	cp -rf --no-preserve=mode $$EASYJSON_DIR/easyjson/ $(VENDORDIR)/github.com/mailru/easyjson/; \
+	mkdir -p $(VENDORDIR)/google.golang.org/grpc/cmd/protoc-gen-go-grpc/; \
+	cp -rf --no-preserve=mode $(GOPATH)/pkg/mod/google.golang.org/grpc/cmd/protoc-gen-go-grpc@$(PROTOC_GEN_GRPC_VERSION)/* $(VENDORDIR)/google.golang.org/grpc/cmd/protoc-gen-go-grpc/; \
+	cp -rf --no-preserve=mode $$PROTOBUF_DIR/cmd/ $(VENDORDIR)/google.golang.org/protobuf/; \
+	cp -rf --no-preserve=mode $$PROTOBUF_DIR/compiler/ $(VENDORDIR)/google.golang.org/protobuf/; \
+	cp -rf --no-preserve=mode $$PROTOBUF_DIR/types/ $(VENDORDIR)/google.golang.org/protobuf/; \
+
+tarball: vendor
 	git archive \
 		--prefix=nextcloud-spreed-signaling-$(TARVERSION)/ \
-		-o nextcloud-spreed-signaling-$(TARVERSION).tar.gz \
+		-o nextcloud-spreed-signaling-$(TARVERSION).tar \
 		HEAD
+	tar rf nextcloud-spreed-signaling-$(TARVERSION).tar \
+		-C $(CURDIR) \
+		--mtime="$(shell git log -1 --date=iso8601-strict --format=%cd HEAD)" \
+		--transform "s//nextcloud-spreed-signaling-$(TARVERSION)\//" \
+		vendor
+	gzip --force nextcloud-spreed-signaling-$(TARVERSION).tar
 
 dist: tarball
 
 .NOTPARALLEL: %_easyjson.go
-.PHONY: continentmap.go
+.PHONY: continentmap.go vendor
diff --git a/go.mod b/go.mod
index 6f6ab6e..3a3232e 100644
--- a/go.mod
+++ b/go.mod
@@ -21,6 +21,7 @@ require (
 	go.etcd.io/etcd/client/v3 v3.5.4
 	go.etcd.io/etcd/server/v3 v3.5.4
 	google.golang.org/grpc v1.48.0
+	google.golang.org/protobuf v1.28.0
 )
 
 require (
@@ -79,7 +80,6 @@ require (
 	golang.org/x/text v0.3.6 // indirect
 	golang.org/x/time v0.0.0-20211116232009-f0f3c7e86c11 // indirect
 	google.golang.org/genproto v0.0.0-20210602131652-f16073e35f0c // indirect
-	google.golang.org/protobuf v1.28.0 // indirect
 	gopkg.in/natefinch/lumberjack.v2 v2.0.0 // indirect
 	gopkg.in/yaml.v2 v2.4.0 // indirect
 	sigs.k8s.io/yaml v1.2.0 // indirect
diff --git a/vendor_helper_test.go b/vendor_helper_test.go
new file mode 100644
index 0000000..0166898
--- /dev/null
+++ b/vendor_helper_test.go
@@ -0,0 +1,29 @@
+/**
+ * Standalone signaling server for the Nextcloud Spreed app.
+ * Copyright (C) 2022 struktur AG
+ *
+ * @author Joachim Bauch <bauch@struktur.de>
+ *
+ * @license GNU AGPL version 3 or any later version
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU Affero General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU Affero General Public License for more details.
+ *
+ * You should have received a copy of the GNU Affero General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+package signaling
+
+// Import modules that would otherwise not be detected by "go mod vendor".
+import (
+	_ "github.com/mailru/easyjson/bootstrap"
+	_ "github.com/mailru/easyjson/gen"
+	_ "github.com/mailru/easyjson/parser"
+)