feat: split out agent executable

This allows for a smaller agent executable
that uses less (locked) memory.

Refactor the package `pago` into a number of packages
to enable separating the agent.

Stop locking memory in the main pago executable
when contacting the agent.
It potentially confuses the user's security expectations
because operations without an agent don't do it.

v0.10.0

Author: dbohdan

.gitignore

@@ -1,5 +1,6 @@
 /attic/
 /cmd/pago/pago
+/cmd/pago-agent/pago-agent
 /dist/
 /help
 /pago

README.md

@@ -68,6 +68,7 @@ Once Go is installed on your system, run the following command:
 
 ```
 go install dbohdan.com/pago/cmd/pago@latest
+go install dbohdan.com/pago/cmd/pago-agent@latest
 ```
 
 Shell completion files for Bash and fish are available in [`completions/`](completions/).
@@ -185,6 +186,11 @@ pago show foo/bar
 # Start manually.
 pago agent start
 
+# By default, the agent locks its memory to prevent secrets from being written to swap.
+# You may need to run `ulimit -l 100000` to let it lock enough memory.
+# Alternatively, you can disable this feature with the flag `--no-mlock`.
+pago agent start --no-mlock
+
 # Run without an agent.
 pago -s '' show foo/bar
 
@@ -194,6 +200,8 @@ pago agent stop
 
 ### Environment variables
 
+- `PAGO_AGENT`:
+  The agent executable path
 - `PAGO_CLIP`:
   The command to use to copy the password to the clipboard.
   The default differs by platform.
@@ -208,6 +216,9 @@ pago agent stop
   Whether to use Git
 - `PAGO_LENGTH`:
   The default length of random passwords
+- `PAGO_MLOCK`:
+  Whether the agent should lock its memory using [mlockall(2)](https://pubs.opengroup.org/onlinepubs/9799919799/functions/mlockall.html) to prevent secrets from being written to swap.
+  `0` to disable.
 - `PAGO_PATTERN`:
   The default character pattern (regular expression) for random passwords
 - `PAGO_SOCK`:

Taskfile.yml

@@ -1,8 +1,9 @@
 version: '3'
 
 vars:
-  cmd_dir: cmd/pago
   ext: '{{if eq OS "windows"}}.exe{{end}}'
+  pago_agent_dir: cmd/pago-agent
+  pago_dir: cmd/pago
 
 env:
   CGO_ENABLED: 0
@@ -21,34 +22,46 @@ tasks:
     desc: 'Build all components'
     deps:
       - build_pago
+      - build_pago_agent
 
   build_pago:
-    dir: '{{.cmd_dir}}'
+    dir: '{{.pago_dir}}'
     desc: 'Build the pago binary'
     cmds:
       - cmd: go build -trimpath
     sources:
       - '*.go'
-      - '../../*.go'
+      - '../**/*.go'
     generates:
       - pago
 
+  build_pago_agent:
+    dir: '{{.pago_agent_dir}}'
+    desc: 'Build the pago agent binary'
+    cmds:
+      - cmd: go build -trimpath
+    sources:
+      - '*.go'
+      - '../**/*.go'
+    generates:
+      - pago-agent
+
   clean:
-    dir: '{{.cmd_dir}}'
     desc: 'Clean up binaries'
     cmds:
-      - rm -f pago pago.exe
+      - rm -f {{.pago_dir}}/pago{{.ext}} {{.pago_agent_dir}}/pago-agent{{.ext}}
 
   release:
     desc: 'Prepare a release'
     deps:
       - build_pago
     cmds:
-      - VERSION=$({{.cmd_dir}}/pago{{.ext}} version) go run script/release.go
+      - VERSION=$({{.pago_dir}}/pago{{.ext}} version) go run script/release.go
 
   test:
     desc: 'Run tests'
     deps:
       - build_pago
+      - build_pago_agent
     cmds:
       - go test ./...

cmd/pago/agent.go renamed to agent/agent.go

@@ -1,11 +1,9 @@
-//go:build !windows
-
 // pago - a command-line password manager.
 //
 // License: MIT.
 // See the file LICENSE.
 
-package main
+package agent
 
 import (
 	"bytes"
@@ -19,136 +17,56 @@ import (
 	"syscall"
 
 	"dbohdan.com/pago"
+	"dbohdan.com/pago/crypto"
 
 	"filippo.io/age"
 	"github.com/tidwall/redcon"
 	"github.com/valkey-io/valkey-go"
 )
 
-var defaultSocket = filepath.Join(defaultCacheDir, agentSocketPath)
-
-func (cmd *RestartCmd) Run(config *Config) error {
-	if config.Verbose {
-		printRepr(cmd)
-	}
-
-	if err := pago.LockMemory(); err != nil {
-		return err
-	}
-
-	_, _ = messageAgent(config.Socket, "SHUTDOWN")
-
-	identitiesText, err := decryptIdentities(config.Identities)
-	if err != nil {
-		return err
-	}
-
-	return startAgentProcess(config.Socket, identitiesText)
-}
-
-func (cmd *RunCmd) Run(config *Config) error {
-	if config.Verbose {
-		printRepr(cmd)
-	}
-
-	if err := pago.LockMemory(); err != nil {
-		return err
-	}
-
-	return runAgent(config.Socket)
-}
-
-func (cmd *StartCmd) Run(config *Config) error {
-	if config.Verbose {
-		printRepr(cmd)
-	}
-
-	if err := pago.LockMemory(); err != nil {
-		return err
-	}
-
-	if err := pingAgent(config.Socket); err == nil {
-		return fmt.Errorf("found agent responding on socket")
-	}
-
-	identitiesText, err := decryptIdentities(config.Identities)
-	if err != nil {
-		return err
-	}
-
-	return startAgentProcess(config.Socket, identitiesText)
-}
-
-func (cmd *StatusCmd) Run(config *Config) error {
-	if config.Verbose {
-		printRepr(cmd)
-	}
-
-	err := pingAgent(config.Socket)
-	if err == nil {
-		fmt.Println("Ping successful")
-		os.Exit(0)
-	} else {
-		fmt.Println("Failed to ping agent")
-		os.Exit(1)
-	}
-
-	return nil
-}
-
-func (cmd *StopCmd) Run(config *Config) error {
-	if config.Verbose {
-		printRepr(cmd)
-	}
-
-	_, err := messageAgent(config.Socket, "SHUTDOWN")
-	return err
-}
-
-func startAgentProcess(agentSocket, identitiesText string) error {
-	// The agent is the same executable.
-	exe, err := os.Executable()
-	if err != nil {
-		return fmt.Errorf("failed to get executable path: %v", err)
+func StartProcess(executable string, mlock bool, socket, identitiesText string) error {
+	mlockFlag := "--mlock"
+	if !mlock {
+		mlockFlag = "--no-mlock"
 	}
 
-	cmd := exec.Command(exe, "agent", "run", "--socket", agentSocket)
+	cmd := exec.Command(executable, "run", mlockFlag, "--socket", socket)
 
 	// Start the process in the background.
 	if err := cmd.Start(); err != nil {
 		return fmt.Errorf("failed to start agent: %v", err)
 	}
 
-	_ = os.Remove(agentSocket)
+	_ = os.Remove(socket)
 	// Don't wait for the process to finish.
 	go func() {
 		_ = cmd.Wait()
 	}()
 
-	if err := waitUntilAvailable(agentSocket, waitForSocket); err != nil {
+	if err := pago.WaitUntilAvailable(socket, pago.WaitForSocket); err != nil {
 		return fmt.Errorf("timed out waiting for agent socket")
 	}
 
-	_, err = messageAgent(agentSocket, "IDENTITIES", identitiesText)
+	_, err := Message(socket, "IDENTITIES", identitiesText)
 	return err
 }
 
-func runAgent(agentSocket string) error {
-	if err := pingAgent(agentSocket); err == nil {
+func Run(socket string) error {
+	if err := Ping(socket); err == nil {
 		return fmt.Errorf("found agent responding on socket")
 	}
 
-	socketDir := filepath.Dir(agentSocket)
-	if err := os.MkdirAll(socketDir, dirPerms); err != nil {
+	socketDir := filepath.Dir(socket)
+	if err := os.MkdirAll(socketDir, pago.DirPerms); err != nil {
 		return fmt.Errorf("failed to create socket directory: %v", err)
 	}
 
-	os.Remove(agentSocket)
+	os.Remove(socket)
 
 	identities := []age.Identity{}
 	srv := redcon.NewServerNetwork(
 		"unix",
-		agentSocket,
+		socket,
 		func(conn redcon.Conn, cmd redcon.Command) {
 			switch strings.ToUpper(string(cmd.Args[0])) {
 
@@ -162,7 +80,7 @@ func runAgent(agentSocket string) error {
 
 				// Decrypt the data.
 				reader := bytes.NewReader(encryptedData)
-				decryptedReader, err := wrapDecrypt(reader, identities...)
+				decryptedReader, err := crypto.WrapDecrypt(reader, identities...)
 				if err != nil {
 					conn.WriteError("ERR failed to decrypt: " + err.Error())
 					return
@@ -218,22 +136,22 @@ func runAgent(agentSocket string) error {
 			return
 		}
 
-		if err := os.Chmod(agentSocket, filePerms); err != nil {
-			exitWithError("failed to set permissions on agent socket: %v", err)
+		if err := os.Chmod(socket, pago.FilePerms); err != nil {
+			pago.ExitWithError("failed to set permissions on agent socket: %v", err)
 		}
 	}()
 
 	return srv.ListenServeAndSignal(errc)
 }
 
-func messageAgent(agentSocket string, args ...string) (string, error) {
+func Message(socket string, args ...string) (string, error) {
 	// Check socket security.
-	if err := checkSocketSecurity(agentSocket); err != nil {
+	if err := checkSocketSecurity(socket); err != nil {
 		return "", fmt.Errorf("socket security check failed: %v", err)
 	}
 
 	// Connect to the server.
-	opts, err := valkey.ParseURL("unix://" + agentSocket)
+	opts, err := valkey.ParseURL("unix://" + socket)
 	if err != nil {
 		return "", fmt.Errorf("failed to parse socket URL: %v", err)
 	}
@@ -269,23 +187,23 @@ func messageAgent(agentSocket string, args ...string) (string, error) {
 	return string(result), nil
 }
 
-func pingAgent(agentSocket string) error {
-	_, err := messageAgent(agentSocket)
+func Ping(socket string) error {
+	_, err := Message(socket)
 	return err
 }
 
-func decryptWithAgent(agentSocket string, data []byte) (string, error) {
-	return messageAgent(agentSocket, "DECRYPT", valkey.BinaryString(data))
+func Decrypt(socket string, data []byte) (string, error) {
+	return Message(socket, "DECRYPT", valkey.BinaryString(data))
 }
 
-func checkSocketSecurity(agentSocket string) error {
-	info, err := os.Stat(agentSocket)
+func checkSocketSecurity(socket string) error {
+	info, err := os.Stat(socket)
 	if err != nil {
 		return fmt.Errorf("failed to stat socket: %v", err)
 	}
 
 	// Check socket permissions.
-	if info.Mode().Perm() != filePerms {
+	if info.Mode().Perm() != pago.FilePerms {
 		return fmt.Errorf("incorrect socket permissions: %v", info.Mode().Perm())
 	}