sshutil: lock ${LIMA_HOME}/_config

Signed-off-by: Akihiro Suda <akihiro.suda.cz@hco.ntt.co.jp>

go.mod

@@ -21,6 +21,7 @@ require (
 	github.com/sirupsen/logrus v1.8.1
 	github.com/urfave/cli/v2 v2.3.0
 	github.com/yalue/native_endian v1.0.1
+	golang.org/x/sys v0.0.0-20210630005230-0f9fa26af87c
 	gopkg.in/yaml.v2 v2.4.0
 	gotest.tools/v3 v3.0.3
 )

go.sum

@@ -920,8 +920,9 @@ golang.org/x/sys v0.0.0-20201202213521-69691e467435/go.mod h1:h1NjWce9XRLGQEsW7w
 golang.org/x/sys v0.0.0-20210119212857-b64e53b001e4/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
 golang.org/x/sys v0.0.0-20210124154548-22da62e12c0c/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
 golang.org/x/sys v0.0.0-20210303074136-134d130e1a04/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
-golang.org/x/sys v0.0.0-20210324051608-47abb6519492 h1:Paq34FxTluEPvVyayQqMPgHm+vTOrIifmcYxFBx9TLg=
 golang.org/x/sys v0.0.0-20210324051608-47abb6519492/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
+golang.org/x/sys v0.0.0-20210630005230-0f9fa26af87c h1:F1jZWGFhYfh0Ci55sIpILtKKK8p3i2/krTr0H1rg74I=
+golang.org/x/sys v0.0.0-20210630005230-0f9fa26af87c/go.mod h1:oPkhp1MJrh7nUepCBck5+mAzfO9JrbApNNgaTdGDITg=
 golang.org/x/term v0.0.0-20201126162022-7de9c90e9dd1/go.mod h1:bj7SfCRtBDWHUb9snDiAeCFNEtKQo2Wmx5Cou7ajbmo=
 golang.org/x/term v0.0.0-20210503060354-a79de5458b56 h1:b8jxX3zqjpqb2LklXPzKSGJhzyxCOZSz8ncv8Nv+y7w=
 golang.org/x/term v0.0.0-20210503060354-a79de5458b56/go.mod h1:tfny5GFUkzUvx4ps4ajbZsCe5lw1metzhBm9T3x7oIY=

pkg/lockutil/lockutil.go

@@ -0,0 +1,53 @@
+// From https://github.com/containerd/nerdctl/blob/v0.9.0/pkg/lockutil/lockutil_linux.go
+/*
+   Copyright The containerd Authors.
+
+   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 lockutil
+
+import (
+	"os"
+
+	"github.com/pkg/errors"
+	"github.com/sirupsen/logrus"
+	"golang.org/x/sys/unix"
+)
+
+func WithDirLock(dir string, fn func() error) error {
+	dirFile, err := os.Open(dir)
+	if err != nil {
+		return err
+	}
+	defer dirFile.Close()
+	if err := Flock(dirFile, unix.LOCK_EX); err != nil {
+		return errors.Wrapf(err, "failed to lock %q", dir)
+	}
+	defer func() {
+		if err := Flock(dirFile, unix.LOCK_UN); err != nil {
+			logrus.WithError(err).Errorf("failed to unlock %q", dir)
+		}
+	}()
+	return fn()
+}
+
+func Flock(f *os.File, flags int) error {
+	fd := int(f.Fd())
+	for {
+		err := unix.Flock(fd, flags)
+		if err == nil || err != unix.EINTR {
+			return err
+		}
+	}
+}

pkg/sshutil/sshutil.go

@@ -8,6 +8,7 @@ import (
 	"path/filepath"
 	"strings"
 
+	"github.com/AkihiroSuda/lima/pkg/lockutil"
 	"github.com/AkihiroSuda/lima/pkg/osutil"
 	"github.com/AkihiroSuda/lima/pkg/store"
 	"github.com/AkihiroSuda/lima/pkg/store/filenames"
@@ -51,11 +52,16 @@ func DefaultPubKeys() ([]PubKey, error) {
 		if err := os.MkdirAll(configDir, 0700); err != nil {
 			return nil, errors.Wrapf(err, "could not create %q directory", configDir)
 		}
-		keygenCmd := exec.Command("ssh-keygen", "-t", "ed25519", "-q", "-N", "", "-f",
-			filepath.Join(configDir, filenames.UserPrivateKey))
-		logrus.Debugf("executing %v", keygenCmd.Args)
-		if out, err := keygenCmd.CombinedOutput(); err != nil {
-			return nil, errors.Wrapf(err, "failed to run %v: %q", keygenCmd.Args, string(out))
+		if err := lockutil.WithDirLock(configDir, func() error {
+			keygenCmd := exec.Command("ssh-keygen", "-t", "ed25519", "-q", "-N", "", "-f",
+				filepath.Join(configDir, filenames.UserPrivateKey))
+			logrus.Debugf("executing %v", keygenCmd.Args)
+			if out, err := keygenCmd.CombinedOutput(); err != nil {
+				return errors.Wrapf(err, "failed to run %v: %q", keygenCmd.Args, string(out))
+			}
+			return nil
+		}); err != nil {
+			return nil, err
 		}
 	}
 	entry, err := readPublicKey(filepath.Join(configDir, filenames.UserPublicKey))