feat: add support for FUSE

cmd/root.go

@@ -24,6 +24,7 @@ import (
 	"net/url"
 	"os"
 	"os/signal"
+	"path/filepath"
 	"strconv"
 	"strings"
 	"syscall"
@@ -241,7 +242,15 @@ func NewCommand(opts ...Option) *Command {
 	cmd.PersistentFlags().StringVar(&c.conf.APIEndpointURL, "sqladmin-api-endpoint", "",
 		"API endpoint for all Cloud SQL Admin API requests. (default: https://sqladmin.googleapis.com)")
 	cmd.PersistentFlags().StringVar(&c.conf.QuotaProject, "quota-project", "",
-		`Specifies the project for Cloud SQL Admin API quota tracking. Must have "serviceusage.service.use" IAM permission.`)
+		`Specifies the project to use for Cloud SQL Admin API quota tracking.
+The IAM principal must have the "serviceusage.services.use" permission
+for the given project. See https://cloud.google.com/service-usage/docs/overview and
+https://cloud.google.com/storage/docs/requester-pays`)
+	cmd.PersistentFlags().StringVar(&c.conf.FUSEDir, "fuse", "",
+		"Mount a directory at the path using FUSE to access Cloud SQL instances.")
+	cmd.PersistentFlags().StringVar(&c.conf.FUSETempDir, "fuse-tmp-dir",
+		filepath.Join(os.TempDir(), "csql-tmp"),
+		"Temp dir for Unix sockets created with FUSE")
 
 	// Global and per instance flags
 	cmd.PersistentFlags().StringVarP(&c.conf.Addr, "address", "a", "127.0.0.1",
@@ -259,11 +268,24 @@ func NewCommand(opts ...Option) *Command {
 }
 
 func parseConfig(cmd *Command, conf *proxy.Config, args []string) error {
-	// If no instance connection names were provided, error.
-	if len(args) == 0 {
+	// If no instance connection names were provided AND FUSE isn't enabled,
+	// error.
+	if len(args) == 0 && conf.FUSEDir == "" {
 		return newBadCommandError("missing instance_connection_name (e.g., project:region:instance)")
 	}
 
+	if conf.FUSEDir != "" {
+		if err := proxy.SupportsFUSE(); err != nil {
+			return newBadCommandError(
+				fmt.Sprintf("--fuse is not supported: %v", err),
+			)
+		}
+	}
+
+	if len(args) == 0 && conf.FUSEDir == "" && conf.FUSETempDir != "" {
+		return newBadCommandError("cannot specify --fuse-tmp-dir without --fuse")
+	}
+
 	userHasSet := func(f string) bool {
 		return cmd.PersistentFlags().Lookup(f).Changed
 	}

cmd/root_linux_test.go

@@ -0,0 +1,73 @@
+// Copyright 2022 Google LLC
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package cmd
+
+import (
+	"os"
+	"path/filepath"
+	"testing"
+
+	"github.com/spf13/cobra"
+)
+
+func TestNewCommandArgumentsOnLinux(t *testing.T) {
+	defaultTmp := filepath.Join(os.TempDir(), "csql-tmp")
+	tcs := []struct {
+		desc        string
+		args        []string
+		wantDir     string
+		wantTempDir string
+	}{
+		{
+			desc:        "using the fuse flag",
+			args:        []string{"--fuse", "/cloudsql"},
+			wantDir:     "/cloudsql",
+			wantTempDir: defaultTmp,
+		},
+		{
+			desc:        "using the fuse temporary directory flag",
+			args:        []string{"--fuse", "/cloudsql", "--fuse-tmp-dir", "/mycooldir"},
+			wantDir:     "/cloudsql",
+			wantTempDir: "/mycooldir",
+		},
+	}
+
+	for _, tc := range tcs {
+		t.Run(tc.desc, func(t *testing.T) {
+			c := NewCommand()
+			// Keep the test output quiet
+			c.SilenceUsage = true
+			c.SilenceErrors = true
+			// Disable execute behavior
+			c.RunE = func(*cobra.Command, []string) error {
+				return nil
+			}
+			c.SetArgs(tc.args)
+
+			err := c.Execute()
+			if err != nil {
+				t.Fatalf("want error = nil, got = %v", err)
+			}
+
+			if got, want := c.conf.FUSEDir, tc.wantDir; got != want {
+				t.Fatalf("FUSEDir: want = %v, got = %v", want, got)
+			}
+
+			if got, want := c.conf.FUSETempDir, tc.wantTempDir; got != want {
+				t.Fatalf("FUSEDir: want = %v, got = %v", want, got)
+			}
+		})
+	}
+}

cmd/root_test.go

@@ -19,6 +19,8 @@ import (
 	"errors"
 	"net"
 	"net/http"
+	"os"
+	"path/filepath"
 	"sync"
 	"testing"
 	"time"
@@ -41,11 +43,16 @@ func TestNewCommandArguments(t *testing.T) {
 		if c.Addr == "" {
 			c.Addr = "127.0.0.1"
 		}
-		if c.Instances == nil {
-			c.Instances = []proxy.InstanceConnConfig{{}}
+		if c.FUSEDir == "" {
+			if c.Instances == nil {
+				c.Instances = []proxy.InstanceConnConfig{{}}
+			}
+			if i := &c.Instances[0]; i.Name == "" {
+				i.Name = "proj:region:inst"
+			}
 		}
-		if i := &c.Instances[0]; i.Name == "" {
-			i.Name = "proj:region:inst"
+		if c.FUSETempDir == "" {
+			c.FUSETempDir = filepath.Join(os.TempDir(), "csql-tmp")
 		}
 		return c
 	}
@@ -520,6 +527,10 @@ func TestNewCommandWithErrors(t *testing.T) {
 			desc: "using an invalid url for sqladmin-api-endpoint",
 			args: []string{"--sqladmin-api-endpoint", "https://user:abc{DEf1=ghi@example.com:5432/db?sslmode=require", "proj:region:inst"},
 		},
+		{
+			desc: "using fuse-tmp-dir without fuse",
+			args: []string{"--fuse-tmp-dir", "/mydir"},
+		},
 	}
 
 	for _, tc := range tcs {

cmd/root_windows_test.go

@@ -0,0 +1,36 @@
+// Copyright 2022 Google LLC
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package cmd
+
+import (
+	"testing"
+
+	"github.com/spf13/cobra"
+)
+
+func TestWindowsDoesNotSupportFUSE(t *testing.T) {
+	c := NewCommand()
+	// Keep the test output quiet
+	c.SilenceUsage = true
+	c.SilenceErrors = true
+	// Disable execute behavior
+	c.RunE = func(*cobra.Command, []string) error { return nil }
+	c.SetArgs([]string{"--fuse"})
+
+	err := c.Execute()
+	if err == nil {
+		t.Fatal("want error != nil, got = nil")
+	}
+}

go.mod

@@ -9,6 +9,7 @@ require (
 	github.com/denisenkom/go-mssqldb v0.12.2
 	github.com/go-sql-driver/mysql v1.6.0
 	github.com/google/go-cmp v0.5.8
+	github.com/hanwen/go-fuse/v2 v2.1.0
 	github.com/jackc/pgx/v4 v4.17.0
 	github.com/spf13/cobra v1.5.0
 	go.opencensus.io v0.23.0

go.sum

@@ -643,6 +643,9 @@ github.com/grpc-ecosystem/grpc-gateway v1.9.0/go.mod h1:vNeuVxBJEsws4ogUvrchl83t
 github.com/grpc-ecosystem/grpc-gateway v1.9.5/go.mod h1:vNeuVxBJEsws4ogUvrchl83t/GYV9WGTSLVdBhOQFDY=
 github.com/grpc-ecosystem/grpc-gateway v1.16.0/go.mod h1:BDjrQk3hbvj6Nolgz8mAMFbcEtjT1g+wF4CSlocrBnw=
 github.com/grpc-ecosystem/grpc-gateway/v2 v2.7.0/go.mod h1:hgWBS7lorOAVIJEQMi4ZsPv9hVvWI6+ch50m39Pf2Ks=
+github.com/hanwen/go-fuse v1.0.0/go.mod h1:unqXarDXqzAk0rt98O2tVndEPIpUgLD9+rwFisZH3Ok=
+github.com/hanwen/go-fuse/v2 v2.1.0 h1:+32ffteETaLYClUj0a3aHjZ1hOPxxaNEHiZiujuDaek=
+github.com/hanwen/go-fuse/v2 v2.1.0/go.mod h1:oRyA5eK+pvJyv5otpO/DgccS8y/RvYMaO00GgRLGryc=
 github.com/hashicorp/consul/api v1.1.0/go.mod h1:VmuI/Lkw1nC05EYQWNKwWGbkg+FbDBtguAZLlVdkD9Q=
 github.com/hashicorp/consul/api v1.12.0/go.mod h1:6pVBMo0ebnYdt2S3H87XhekM/HHrUoTD2XXb/VrZVy0=
 github.com/hashicorp/consul/sdk v0.1.1/go.mod h1:VKf9jXwCTEY1QZP2MOLRhb5i/I/ssyNV1vwHyQBF0x8=
@@ -798,6 +801,8 @@ github.com/kr/pty v1.1.8/go.mod h1:O1sed60cT9XZ5uDucP5qwvh+TE3NnUj51EiZO/lmSfw=
 github.com/kr/text v0.1.0/go.mod h1:4Jbv+DJW3UT/LiOwJeYQe1efqtUx/iVham/4vfdArNI=
 github.com/kr/text v0.2.0 h1:5Nx0Ya0ZqY2ygV366QzturHI13Jq95ApcVaJBhpS+AY=
 github.com/kr/text v0.2.0/go.mod h1:eLer722TekiGuMkidMxC/pM04lWEeraHUUmBw8l2grE=
+github.com/kylelemons/godebug v0.0.0-20170820004349-d65d576e9348/go.mod h1:B69LEHPfb2qLo0BaaOLcbitczOKLWTsrBG9LczfCD4k=
+github.com/kylelemons/godebug v1.1.0 h1:RPNrshWIDI6G2gRW9EHilWtl7Z6Sb1BR0xunSBf0SNc=
 github.com/kylelemons/godebug v1.1.0/go.mod h1:9/0rRGxNHcop5bhtWyNeEfOS8JIWk580+fNqagV/RAw=
 github.com/leodido/go-urn v1.2.0/go.mod h1:+8+nEpDfqqsY+g338gtMEUOtuK+4dEMhiQEgxpxOKII=
 github.com/lib/pq v1.0.0/go.mod h1:5WUZQaWbwv1U+lTReE5YruASi9Al49XbQIvNi/34Woo=

internal/proxy/fuse.go

@@ -0,0 +1,91 @@
+// Copyright 2022 Google LLC
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package proxy
+
+import (
+	"context"
+	"syscall"
+
+	"github.com/hanwen/go-fuse/v2/fs"
+	"github.com/hanwen/go-fuse/v2/fuse"
+	"github.com/hanwen/go-fuse/v2/fuse/nodefs"
+)
+
+// symlink implements a symbolic link, returning the underlying path when
+// Readlink is called.
+type symlink struct {
+	fs.Inode
+	path string
+}
+
+// Readlink implements fs.NodeReadlinker and returns the symlink's path.
+func (s *symlink) Readlink(ctx context.Context) ([]byte, syscall.Errno) {
+	return []byte(s.path), fs.OK
+}
+
+// readme represents a static read-only text file.
+type readme struct {
+	fs.Inode
+}
+
+const readmeText = `
+When applications attempt to open files in this directory, a remote connection
+to the Cloud SQL instance of the same name will be established.
+
+For example, when you run one of the followg commands, the proxy will initiate a
+connection to the corresponding Cloud SQL instance, given you have the correct
+IAM permissions.
+
+	mysql -u root -S "/somedir/project:region:instance"
+
+    # or
+
+	psql "host=/somedir/project:region:instance dbname=mydb user=myuser"
+
+For MySQL, the proxy will create a socket with the instance connection name
+(e.g., project:region:instance) in this directory. For Postgres, the proxy will
+create a directory with the instance connection name, and create a socket inside
+that directory with the special Postgres name: .s.PGSQL.5432.
+
+Listing the contents of this directory will show all instances with active
+connections.
+`
+
+// Getattr implements fs.NodeGetattrer and indicates that this file is a regular
+// file.
+func (*readme) Getattr(ctx context.Context, f fs.FileHandle, out *fuse.AttrOut) syscall.Errno {
+	*out = fuse.AttrOut{Attr: fuse.Attr{
+		Mode: 0444 | syscall.S_IFREG,
+		Size: uint64(len(readmeText)),
+	}}
+	return fs.OK
+}
+
+// Read implements fs.NodeReader and supports incremental reads.
+func (*readme) Read(ctx context.Context, f fs.FileHandle, dest []byte, off int64) (fuse.ReadResult, syscall.Errno) {
+	end := int(off) + len(dest)
+	if end > len(readmeText) {
+		end = len(readmeText)
+	}
+	return fuse.ReadResultData([]byte(readmeText[off:end])), fs.OK
+}
+
+// Open implements fs.NodeOpener and supports opening the README as a read-only
+// file.
+func (*readme) Open(ctx context.Context, mode uint32) (fs.FileHandle, uint32, syscall.Errno) {
+	df := nodefs.NewDataFile([]byte(readmeText))
+	rf := nodefs.NewReadOnlyFile(df)
+	return rf, 0, fs.OK
+}

internal/proxy/fuse_darwin.go

@@ -0,0 +1,41 @@
+// Copyright 2022 Google LLC
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package proxy
+
+import (
+	"errors"
+	"os"
+)
+
+const (
+	macfusePath = "/Library/Filesystems/macfuse.fs/Contents/Resources/mount_macfuse"
+	osxfusePath = "/Library/Filesystems/osxfuse.fs/Contents/Resources/mount_osxfuse"
+)
+
+// SupportsFUSE checks if macfuse or osxfuse are installed on the host by
+// looking for both in their known installation location.
+func SupportsFUSE() error {
+	// This code follows the same strategy as hanwen/go-fuse.
+	// See https://github.com/hanwen/go-fuse/blob/0f728ba15b38579efefc3dc47821882ca18ffea7/fuse/mount_darwin.go#L121-L124.
+
+	// check for macfuse first (newer version of osxfuse)
+	if _, err := os.Stat(macfusePath); err != nil {
+		// if that fails, check for osxfuse next
+		if _, err := os.Stat(osxfusePath); err != nil {
+			return errors.New("failed to find osxfuse or macfuse: verify FUSE installation and try again (see https://osxfuse.github.io).")
+		}
+	}
+	return nil
+}

internal/proxy/fuse_linux.go

@@ -0,0 +1,33 @@
+// Copyright 2022 Google LLC
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package proxy
+
+import (
+	"errors"
+	"os/exec"
+)
+
+// SupportsFUSE checks if the fusermount binary is present in the PATH or a well
+// known location.
+func SupportsFUSE() error {
+	// This code follows the same strategy found in hanwen/go-fuse.
+	// See https://github.com/hanwen/go-fuse/blob/0f728ba15b38579efefc3dc47821882ca18ffea7/fuse/mount_linux.go#L184-L198.
+	if _, err := exec.LookPath("fusermount"); err != nil {
+		if _, err := exec.LookPath("/bin/fusermount"); err != nil {
+			return errors.New("fusermount binary not found in PATH or /bin")
+		}
+	}
+	return nil
+}