TUN-5277: Ensure cloudflared binary is FIPS compliant on linux amd64

Makefile

@@ -3,14 +3,6 @@ MSI_VERSION   := $(shell git tag -l --sort=v:refname | grep "w" | tail -1 | cut
 #MSI_VERSION expects the format of the tag to be: (wX.X.X). Starts with the w character to not break cfsetup.
 #e.g. w3.0.1 or w4.2.10. It trims off the w character when creating the MSI.
 
-ifeq ($(FIPS), true)
-	GO_BUILD_TAGS := $(GO_BUILD_TAGS) fips
-endif
-
-ifneq ($(GO_BUILD_TAGS),)
-	GO_BUILD_TAGS := -tags $(GO_BUILD_TAGS)
-endif
-
 ifeq ($(NIGHTLY), true)
 	DEB_PACKAGE_NAME := cloudflared-nightly
 	NIGHTLY_FLAGS := --conflicts cloudflared --replaces cloudflared
@@ -19,7 +11,19 @@ else
 endif
 
 DATE          := $(shell date -u '+%Y-%m-%d-%H%M UTC')
-VERSION_FLAGS := -ldflags='-X "main.Version=$(VERSION)" -X "main.BuildTime=$(DATE)"'
+VERSION_FLAGS := -X "main.Version=$(VERSION)" -X "main.BuildTime=$(DATE)"
+
+LINK_FLAGS :=
+ifeq ($(FIPS), true)
+	LINK_FLAGS := -linkmode=external -extldflags=-static $(LINK_FLAGS)
+	# Prevent linking with libc regardless of CGO enabled or not.
+	GO_BUILD_TAGS := $(GO_BUILD_TAGS) osusergo netgo fips
+endif
+
+LDFLAGS := -ldflags='$(VERSION_FLAGS) $(LINK_FLAGS)'
+ifneq ($(GO_BUILD_TAGS),)
+	GO_BUILD_TAGS := -tags "$(GO_BUILD_TAGS)"
+endif
 
 IMPORT_PATH   := github.com/cloudflare/cloudflared
 PACKAGE_DIR   := $(CURDIR)/packaging
@@ -83,14 +87,12 @@ clean:
 cloudflared:
 ifeq ($(FIPS), true)
 	$(info Building cloudflared with go-fips)
-	-test -f fips/fips.go && mv fips/fips.go fips/fips.go.linux-amd64
+	cp -f fips/fips.go.linux-amd64 cmd/cloudflared/fips.go
-	mv fips/fips.go.linux-amd64 fips/fips.go
 endif
-
+	GOOS=$(TARGET_OS) GOARCH=$(TARGET_ARCH) go build -v -mod=vendor $(GO_BUILD_TAGS) $(LDFLAGS) $(IMPORT_PATH)/cmd/cloudflared
-	GOOS=$(TARGET_OS) GOARCH=$(TARGET_ARCH) go build -v -mod=vendor $(GO_BUILD_TAGS) $(VERSION_FLAGS) $(IMPORT_PATH)/cmd/cloudflared
-
 ifeq ($(FIPS), true)
-	mv fips/fips.go fips/fips.go.linux-amd64
+	rm -f cmd/cloudflared/fips.go
+	./check-fips.sh cloudflared
 endif
 
 .PHONY: container
@@ -100,10 +102,10 @@ container:
 .PHONY: test
 test: vet
 ifndef CI
-	go test -v -mod=vendor -race $(VERSION_FLAGS) ./...
+	go test -v -mod=vendor -race $(LDFLAGS) ./...
 else
 	@mkdir -p .cover
-	go test -v -mod=vendor -race $(VERSION_FLAGS) -coverprofile=".cover/c.out" ./...
+	go test -v -mod=vendor -race $(LDFLAGS) -coverprofile=".cover/c.out" ./...
 	go tool cover -html ".cover/c.out" -o .cover/all.html
 endif
 

build-packages.sh

@@ -1,6 +1,9 @@
 VERSION=$(git describe --tags --always --dirty="-dev" --match "[0-9][0-9][0-9][0-9].*.*")
 echo $VERSION
+
+# Avoid depending on C code since we don't need it.
 export CGO_ENABLED=0
+
 # This controls the directory the built artifacts go into
 export ARTIFACT_DIR=built_artifacts/
 mkdir -p $ARTIFACT_DIR
@@ -14,10 +17,15 @@ for arch in ${windowsArchs[@]}; do
 done
 
 
-export FIPS=true
+# amd64 is last because we override settings for it
-linuxArchs=("amd64" "386" "arm" "arm64")
+linuxArchs=("386" "arm" "arm64" "amd64")
 export TARGET_OS=linux
 for arch in ${linuxArchs[@]}; do
+    if [ "${arch}" = "amd64" ]; then
+        export FIPS=true
+        # For BoringCrypto to link, we need CGO enabled. Otherwise compilation fails.
+        export CGO_ENABLED=1
+    fi
     export TARGET_ARCH=$arch
     make cloudflared-deb
     mv cloudflared\_$VERSION\_$arch.deb $ARTIFACT_DIR/cloudflared-linux-$arch.deb
@@ -37,4 +45,3 @@ for arch in ${linuxArchs[@]}; do
     # finally move the linux binary as well.
     mv ./cloudflared $ARTIFACT_DIR/cloudflared-linux-$arch
 done
-

cfsetup.yaml

@@ -1,5 +1,5 @@
 pinned_go: &pinned_go go=1.17-1
-pinned_go_fips: &pinned_go_fips go-boring=1.16.6-6
+pinned_go_fips: &pinned_go_fips go-boring=1.16.6-7
 
 build_dir: &build_dir /cfsetup_build
 default-flavor: buster
@@ -41,7 +41,6 @@ stretch: &stretch
       - wget https://github.com/sudarshan-reddy/msitools/releases/download/v0.101b/wixl -P /usr/local/bin
       - chmod a+x /usr/local/bin/wixl
     post-cache:
-      - export FIPS=true
       - ./build-packages.sh
   github-release-pkgs:
     build_dir: *build_dir

check-fips.sh

@@ -0,0 +1,15 @@
+# Pass the path to the executable to check for FIPS compliance
+exe=$1
+
+if [ "$(go tool nm "${exe}" | grep -c '_Cfunc__goboringcrypto_')" -eq 0 ]; then
+    # Asserts that executable is using FIPS-compliant boringcrypto
+    echo "${exe}: missing goboring symbols" >&2
+    exit 1
+fi
+if [ "$(go tool nm "${exe}" | grep -c 'crypto/internal/boring/sig.FIPSOnly')" -eq 0 ]; then
+    # Asserts that executable is using FIPS-only schemes
+    echo "${exe}: missing fipsonly symbols" >&2
+    exit 1
+fi
+
+echo "${exe} is FIPS-compliant"