Implement concurrency in GPG agent server

deploy/piv-agent.service

@@ -2,4 +2,4 @@
 Description=piv-agent service
 
 [Service]
-ExecStart=piv-agent serve --debug --agent-types=ssh=0;gpg=1
+ExecStart=piv-agent serve --agent-types=ssh=0;gpg=1

internal/assuan/assuan_test.go

@@ -2,6 +2,7 @@ package assuan_test
 
 import (
 	"bytes"
+	"context"
 	"crypto"
 	"crypto/ecdsa"
 	"encoding/hex"
@@ -153,7 +154,7 @@ func TestSign(t *testing.T) {
 				}
 			}
 			// start the state machine
-			if err := a.Run(); err != nil {
+			if err := a.Run(context.Background()); err != nil {
 				tt.Fatal(err)
 			}
 			// check the responses
@@ -226,7 +227,7 @@ func TestKeyinfo(t *testing.T) {
 				}
 			}
 			// start the state machine
-			if err := a.Run(); err != nil {
+			if err := a.Run(context.Background()); err != nil {
 				tt.Fatal(err)
 			}
 			// check the responses
@@ -349,7 +350,7 @@ func TestDecryptRSAKeyfile(t *testing.T) {
 				}
 			}
 			// start the state machine
-			if err := a.Run(); err != nil {
+			if err := a.Run(context.Background()); err != nil {
 				tt.Fatal(err)
 			}
 			// check the responses
@@ -447,7 +448,7 @@ func TestSignRSAKeyfile(t *testing.T) {
 				}
 			}
 			// start the state machine
-			if err := a.Run(); err != nil {
+			if err := a.Run(context.Background()); err != nil {
 				tt.Fatal(err)
 			}
 			// check the responses
@@ -533,7 +534,7 @@ func TestReadKey(t *testing.T) {
 				}
 			}
 			// start the state machine
-			if err := a.Run(); err != nil {
+			if err := a.Run(context.Background()); err != nil {
 				tt.Fatal(err)
 			}
 			// check the responses

internal/assuan/run.go

@@ -2,18 +2,24 @@ package assuan
 
 import (
 	"bytes"
+	"context"
 	"fmt"
 	"io"
 )
 
 // Run the event machine loop
-func (a *Assuan) Run() error {
+func (a *Assuan) Run(ctx context.Context) error {
 	// register connection
 	if err := a.Occur(connect); err != nil {
 		return fmt.Errorf("error handling connect: %w", err)
 	}
 	var e Event
 	for {
+		// check for cancellation
+		if err := ctx.Err(); err != nil {
+			return err
+		}
+		// get the next command. returns at latest after conn deadline expiry.
 		line, err := a.reader.ReadBytes(byte('\n'))
 		if err != nil {
 			if err == io.EOF {

internal/server/gpg.go

@@ -12,6 +12,8 @@ import (
 	"go.uber.org/zap"
 )
 
+const connTimeout = 4 * time.Minute
+
 // GPG represents a gpg-agent server.
 type GPG struct {
 	log           *zap.Logger
@@ -39,26 +41,31 @@ func (g *GPG) Serve(ctx context.Context, l net.Listener, exit *time.Ticker,
 	timeout time.Duration) error {
 	// start serving connections
 	conns := accept(g.log, l)
-	g.log.Debug("accepted gpg-agent connection")
 	for {
 		select {
 		case conn, ok := <-conns:
 			if !ok {
 				return fmt.Errorf("listen socket closed")
 			}
+			g.log.Debug("accepted gpg-agent connection")
 			// reset the exit timer
 			exit.Reset(timeout)
-			// if the client stops responding for 300 seconds, give up.
-			if err := conn.SetDeadline(time.Now().Add(300 * time.Second)); err != nil {
+			// if the client takes too long, give up
+			if err := conn.SetDeadline(time.Now().Add(connTimeout)); err != nil {
 				return fmt.Errorf("couldn't set deadline: %v", err)
 			}
 			// init protocol state machine
 			a := assuan.New(conn, g.log, g.pivKeyService, g.gpgKeyService)
-			// run the protocol state machine to completion
-			// (client severs connection)
-			if err := a.Run(); err != nil {
-				return err
-			}
+			// this goroutine will exit by either:
+			// * client severs connection (the usual case)
+			// * conn deadline reached (client stopped responding)
+			//   err will be non-nil in this case.
+			go func() {
+				// run the protocol state machine to completion
+				if err := a.Run(ctx); err != nil {
+					g.log.Error("gpg-agent error", zap.Error(err))
+				}
+			}()
 		case <-ctx.Done():
 			return nil
 		}

internal/server/ssh.go

@@ -42,7 +42,7 @@ func (s *SSH) Serve(ctx context.Context, a *ssh.Agent, l net.Listener,
 			s.log.Debug("start serving SSH connection")
 			if err := agent.ServeAgent(a, conn); err != nil {
 				if errors.Is(err, io.EOF) {
-					s.log.Debug("finish serving connection")
+					s.log.Debug("finish serving SSH connection")
 					continue
 				}
 				return fmt.Errorf("ssh Serve error: %w", err)