Add a rpc server

This change introduces a remote procedure call server responsible for
handling requests to execute pre-registered procedures using JSON-RPC
2.0 as the transport protocol.

The purpose of this server is to provide a way for a mole process to
provide or be managed by others processes (e.g. some sort of user
interface that will creates/destroy instances of mole and/or collect
data from them).

The rpc server is disable by default. The user can enable it through the
`--rpc` flag. By default, the server will be listening on the localhost
address and on a random free port since a user might have multiple
instance of the program running at the same time on a single machine.
The `--rpc-address` flag can be use to set a specific address.

alias/alias.go

@@ -28,10 +28,13 @@ type Alias struct {
 	SshAgent          string   `toml:"ssh-agent"`
 	Timeout           string   `toml:"timeout"`
 	SshConfig         string   `toml:"config"`
+	Rpc               bool     `toml:"rpc"`
+	RpcAddress        string   `toml:"rpc-address"`
 }
 
+// String parses a Alias object to a string representation.
 func (a Alias) String() string {
-	return fmt.Sprintf("[verbose: %t, insecure: %t, detach: %t, source: %s, destination: %s, server: %s, key: %s, keep-alive-interval: %s, connection-retries: %d, wait-and-retry: %s, ssh-agent: %s, timeout: %s, config: %s]",
+	return fmt.Sprintf("[verbose: %t, insecure: %t, detach: %t, source: %s, destination: %s, server: %s, key: %s, keep-alive-interval: %s, connection-retries: %d, wait-and-retry: %s, ssh-agent: %s, timeout: %s, config: %s, rpc: %t, rpc-address: %s]",
 		a.Verbose,
 		a.Insecure,
 		a.Detach,
@@ -45,12 +48,14 @@ func (a Alias) String() string {
 		a.SshAgent,
 		a.Timeout,
 		a.SshConfig,
+		a.Rpc,
+		a.RpcAddress,
 	)
 }
 
 // Add persists an tunnel alias to the disk
 func Add(alias *Alias) error {
-	mp, err := createDir()
+	mp, err := fsutils.CreateHomeDir()
 	if err != nil {
 		return err
 	}
@@ -174,24 +179,6 @@ func Get(aliasName string) (*Alias, error) {
 	return a, nil
 }
 
-func createDir() (string, error) {
-	mp, err := fsutils.Dir()
-	if err != nil {
-		return "", err
-	}
-
-	if _, err := os.Stat(mp); !os.IsNotExist(err) {
-		return mp, nil
-	}
-
-	err = os.MkdirAll(mp, os.ModePerm)
-	if err != nil {
-		return "", err
-	}
-
-	return mp, nil
-}
-
 //FIXME terrible struct name. Change it.
 type aliases struct {
 	Aliases map[string]*Alias `toml:"aliases"`

alias/alias_test.go

@@ -67,6 +67,10 @@ func TestShow(t *testing.T) {
 		expected := string(expectedBytes)
 
 		output, err := alias.Show(id)
+		if err != nil {
+			t.Errorf("error showing alias %s: %v", id, err)
+		}
+
 		if output != expected {
 			t.Errorf("output doesn't match. Failing the test.")
 		}

alias/testdata/example.toml

@@ -12,3 +12,5 @@ wait-and-retry = "3s"
 ssh-agent = ""
 timeout = "3s"
 config = ""
+rpc = true
+rpc-address = "127.0.0.1:0"

alias/testdata/show.alias.fixture

@@ -15,6 +15,8 @@
     ssh-agent = ""
     timeout = "3s"
     config = ""
+    rpc = true
+    rpc-address = "127.0.0.1:0"
   [aliases.test-env]
     name = "test-env"
     type = "local"
@@ -31,3 +33,5 @@
     ssh-agent = ""
     timeout = "3s"
     config = ""
+    rpc = true
+    rpc-address = "127.0.0.1:0"

alias/testdata/show.alias.test-env.fixture

@@ -13,3 +13,5 @@ wait-and-retry = "3s"
 ssh-agent = ""
 timeout = "3s"
 config = ""
+rpc = true
+rpc-address = "127.0.0.1:0"

alias/testdata/test-env.toml

@@ -12,3 +12,5 @@ wait-and-retry = "3s"
 ssh-agent = ""
 timeout = "3s"
 config = ""
+rpc = true
+rpc-address = "127.0.0.1:0"

cmd/root.go

@@ -47,6 +47,10 @@ provide 0 to never give up or a negative number to disable`)
 	cmd.Flags().DurationVarP(&conf.WaitAndRetry, "retry-wait", "w", 3*time.Second, "time to wait before trying to reconnect to ssh server")
 	cmd.Flags().StringVarP(&conf.SshAgent, "ssh-agent", "A", "", "unix socket to communicate with a ssh agent")
 	cmd.Flags().DurationVarP(&conf.Timeout, "timeout", "t", 3*time.Second, "ssh server connection timeout")
+	cmd.Flags().BoolVarP(&conf.Rpc, "rpc", "", false, "enable the rpc server")
+	cmd.Flags().StringVarP(&conf.RpcAddress, "rpc-address", "", "127.0.0.1:0", `set the network address of the rpc server.
+The default value uses a random free port to listen for requests.
+The full address is kept on $HOME/.mole/<id>.`)
 
 	err := cmd.MarkFlagRequired("server")
 	if err != nil {

fsutils/fsutils.go

@@ -17,3 +17,42 @@ func Dir() (string, error) {
 
 	return mp, nil
 }
+
+// CreateHomeDir creates then returns the location where all mole related files
+// are persisted, including alias configuration and log files.
+func CreateHomeDir() (string, error) {
+
+	home, err := Dir()
+	if err != nil {
+		return "", err
+	}
+
+	if _, err := os.Stat(home); os.IsNotExist(err) {
+		err := os.MkdirAll(home, 0755)
+		if err != nil {
+			return "", err
+		}
+	}
+
+	return home, err
+}
+
+// CreateInstanceDir creates and then returns the location where all files
+// related to a specific mole instance are persisted.
+func CreateInstanceDir(appId string) (string, error) {
+	home, err := Dir()
+	if err != nil {
+		return "", err
+	}
+
+	d := filepath.Join(home, appId)
+
+	if _, err := os.Stat(d); os.IsNotExist(err) {
+		err := os.MkdirAll(d, 0755)
+		if err != nil {
+			return "", err
+		}
+	}
+
+	return d, nil
+}

go.mod

@@ -14,6 +14,7 @@ require (
 	github.com/prometheus/common v0.10.0
 	github.com/sevlyar/go-daemon v0.1.5
 	github.com/sirupsen/logrus v1.6.0
+	github.com/sourcegraph/jsonrpc2 v0.0.0-20200429184054-15c2290dcb37
 	github.com/spf13/cobra v0.0.5
 	github.com/spf13/pflag v1.0.5
 	github.com/spf13/viper v1.3.2

go.sum

@@ -39,6 +39,7 @@ github.com/golang/protobuf v1.3.1/go.mod h1:6lQm79b+lXiMfvg/cZm0SGofjICqVBUtrP5y
 github.com/golang/protobuf v1.3.2/go.mod h1:6lQm79b+lXiMfvg/cZm0SGofjICqVBUtrP5yJMmIC1U=
 github.com/google/go-dap v0.2.0 h1:whjIGQRumwbR40qRU7CEKuFLmePUUc2s4Nt9DoXXxWk=
 github.com/google/go-dap v0.2.0/go.mod h1:5q8aYQFnHOAZEMP+6vmq25HKYAEwE+LF5yh7JKrrhSQ=
+github.com/gorilla/websocket v1.4.1/go.mod h1:YR8l580nyteQvAITg2hZ9XVh4b55+EU/adAjf1fMHhE=
 github.com/hashicorp/golang-lru v0.5.4 h1:YDjusn29QI/Das2iO9M0BHnIbxPeyuCHsjMW+lJfyTc=
 github.com/hashicorp/golang-lru v0.5.4/go.mod h1:iADmTwqILo4mZ8BN3D2Q6+9jd8WM5uGBxy+E8yxSoD4=
 github.com/hashicorp/hcl v1.0.0 h1:0Anlzjpi4vEasTeNFn2mLJgTSwt0+6sfsiTG8qcWGx4=
@@ -98,6 +99,8 @@ github.com/sirupsen/logrus v1.4.2 h1:SPIRibHv4MatM3XXNO2BJeFLZwZ2LvZgfQ5+UNI2im4
 github.com/sirupsen/logrus v1.4.2/go.mod h1:tLMulIdttU9McNUspp0xgXVQah82FyeX6MwdIuYE2rE=
 github.com/sirupsen/logrus v1.6.0 h1:UBcNElsrwanuuMsnGSlYmtmgbb23qDR5dG+6X6Oo89I=
 github.com/sirupsen/logrus v1.6.0/go.mod h1:7uNnSEd1DgxDLC74fIahvMZmmYsHGZGEOFrfsX/uA88=
+github.com/sourcegraph/jsonrpc2 v0.0.0-20200429184054-15c2290dcb37 h1:marA1XQDC7N870zmSFIoHZpIUduK80USeY0Rkuflgp4=
+github.com/sourcegraph/jsonrpc2 v0.0.0-20200429184054-15c2290dcb37/go.mod h1:ZafdZgk/axhT1cvZAPOhw+95nz2I/Ra5qMlU4gTRwIo=
 github.com/spf13/afero v1.1.2/go.mod h1:j4pytiNVoe2o6bmDsKpLACNPDBIoEAkihy7loJ1B0CQ=
 github.com/spf13/cast v1.3.0/go.mod h1:Qx5cxh0v+4UWYiBimWS+eyWzqEqokIECu5etghLkUJE=
 github.com/spf13/cobra v0.0.0-20170417170307-b6cb39589372/go.mod h1:1l0Ry5zgKvJasoi3XT1TypsSe7PqH0Sj9dhYf7v3XqQ=

mole/app.go

@@ -8,7 +8,6 @@ import (
 	"strconv"
 
 	"github.com/davrodpin/mole/fsutils"
-	"github.com/gofrs/uuid"
 	"github.com/hpcloud/tail"
 )
 
@@ -34,26 +33,13 @@ type DetachedInstance struct {
 // NewDetachedInstance returns a new instance of DetachedInstance, making sure
 // the application instance directory is created.
 func NewDetachedInstance(id string) (*DetachedInstance, error) {
-	instanceDir, err := fsutils.Dir()
-	if err != nil {
-		return nil, err
-	}
-
 	if id == "" {
-		u, err := uuid.NewV4()
-		if err != nil {
-			return nil, fmt.Errorf("could not auto generate app instance id: %v", err)
-		}
-		id = u.String()[:8]
+		return nil, fmt.Errorf("application instance id can't be empty")
 	}
 
-	home := filepath.Join(instanceDir, id)
-
-	if _, err := os.Stat(home); os.IsNotExist(err) {
-		err := os.MkdirAll(home, 0755)
-		if err != nil {
-			return nil, err
-		}
+	_, err := fsutils.CreateInstanceDir(id)
+	if err != nil {
+		return nil, err
 	}
 
 	pfl, err := GetPidFileLocation(id)

mole/app_test.go

@@ -43,18 +43,6 @@ func TestDetachedInstanceFileLocations(t *testing.T) {
 
 }
 
-func TestDetachedInstanceGeneratedId(t *testing.T) {
-
-	di, err := mole.NewDetachedInstance("")
-	if err != nil {
-		t.Errorf("error creating a new detached instance: %v", err)
-	}
-
-	if di.Id == "" {
-		t.Errorf("detached instance id is empty")
-	}
-}
-
 func TestDetachedInstanceAlreadyRunning(t *testing.T) {
 	id := "TestDetachedInstanceAlreadyRunning"
 

mole/mole.go

@@ -2,15 +2,21 @@ package mole
 
 import (
 	"fmt"
+	"io/ioutil"
 	"os"
+	"path/filepath"
+	"strconv"
 	"syscall"
 	"time"
 
 	"github.com/davrodpin/mole/alias"
+	"github.com/davrodpin/mole/fsutils"
+	"github.com/davrodpin/mole/rpc"
 	"github.com/davrodpin/mole/tunnel"
-	"github.com/sevlyar/go-daemon"
 
 	"github.com/awnumar/memguard"
+	"github.com/gofrs/uuid"
+	"github.com/sevlyar/go-daemon"
 	log "github.com/sirupsen/logrus"
 	"golang.org/x/crypto/ssh/terminal"
 )
@@ -31,6 +37,8 @@ type Configuration struct {
 	SshAgent          string
 	Timeout           time.Duration
 	SshConfig         string
+	Rpc               bool
+	RpcAddress        string
 }
 
 // ParseAlias translates a Configuration object to an Alias object.
@@ -51,6 +59,8 @@ func (c Configuration) ParseAlias(name string) *alias.Alias {
 		SshAgent:          c.SshAgent,
 		Timeout:           c.Timeout.String(),
 		SshConfig:         c.SshConfig,
+		Rpc:               c.Rpc,
+		RpcAddress:        c.RpcAddress,
 	}
 }
 
@@ -74,6 +84,14 @@ func (c *Client) Start() error {
 	if c.Conf.Detach {
 		var err error
 
+		if c.Conf.Id == "" {
+			u, err := uuid.NewV4()
+			if err != nil {
+				return fmt.Errorf("could not auto generate app instance id: %v", err)
+			}
+			c.Conf.Id = u.String()[:8]
+		}
+
 		ic, err := NewDetachedInstance(c.Conf.Id)
 		if err != nil {
 			log.WithError(err).Errorf("error while creating directory to store mole instance related files")
@@ -90,10 +108,44 @@ func (c *Client) Start() error {
 		}
 	}
 
+	if c.Conf.Id == "" {
+		c.Conf.Id = strconv.Itoa(os.Getpid())
+	}
+
 	if c.Conf.Verbose {
 		log.SetLevel(log.DebugLevel)
 	}
 
+	d, err := fsutils.CreateInstanceDir(c.Conf.Id)
+	if err != nil {
+		log.WithFields(log.Fields{
+			"id": c.Conf.Id,
+		}).WithError(err).Error("error creating directory for mole instance")
+
+		return err
+	}
+
+	log.Infof(">>> %t %s", c.Conf.Rpc, c.Conf.RpcAddress)
+	if c.Conf.Rpc {
+		addr, err := rpc.Start(c.Conf.RpcAddress)
+		if err != nil {
+			return err
+		}
+
+		rd := filepath.Join(d, "rpc")
+
+		err = ioutil.WriteFile(rd, []byte(addr.String()), 0644)
+		if err != nil {
+			log.WithFields(log.Fields{
+				"id": c.Conf.Id,
+			}).WithError(err).Error("error creating file with rpc address")
+
+			return err
+		}
+
+		log.Infof("rpc server address saved on %s", rd)
+	}
+
 	s, err := tunnel.NewServer(c.Conf.Server.User, c.Conf.Server.Address(), c.Conf.Key, c.Conf.SshAgent, c.Conf.SshConfig)
 	if err != nil {
 		log.Errorf("error processing server options: %v\n", err)
@@ -142,7 +194,8 @@ func (c *Client) Start() error {
 	//TODO need to find a way to require the attributes below to be always set
 	// since they are not optional (functionality will break if they are not
 	// set and CLI parsing is the one setting the default values).
-	// That could be done by make them required in the constructor's signature
+	// That could be done by make them required in the constructor's signature or
+	// by creating a configuration struct for a tunnel object.
 	t.ConnectionRetries = c.Conf.ConnectionRetries
 	t.WaitAndRetry = c.Conf.WaitAndRetry
 	t.KeepAliveInterval = c.Conf.KeepAliveInterval
@@ -267,6 +320,10 @@ func (c *Configuration) Merge(al *alias.Alias, givenFlags []string) error {
 
 	c.SshConfig = al.SshConfig
 
+	c.Rpc = al.Rpc
+
+	c.RpcAddress = al.RpcAddress
+
 	return nil
 }
 

mole/mole_test.go

@@ -8,8 +8,6 @@ import (
 )
 
 func TestAliasMerge(t *testing.T) {
-	//keepAliveInterval, _ := time.ParseDuration("5s")
-
 	tests := []struct {
 		alias      *alias.Alias
 		givenFlags []string

rpc/doc.go

@@ -0,0 +1,10 @@
+/*
+Package rpc implements a JSON-RPC 2.0 server that is used to call registered
+procedures.
+
+For more information about JSON-RPC 2.0, please visit:
+
+https://www.jsonrpc.org/specification
+*/
+
+package rpc