osbase/net/sshtakeover: fix upload cancelation

This updates sftp to the latest version, which has various improvements.

The previous method of canceling uploads doesn't work anymore, because
Close tries to take a lock already held by ReadFromWithConcurrency.
Even with the previous version of sftp, this wasn't a correct way to
cancel an upload, because it just sent a message to the server to close
the handle, while continuing the upload in the other goroutine.

There is a work in progress v2 of sftp where Close actually can be used
to cancel an upload: https://github.com/pkg/sftp/issues/603

For now, I think the best way to cancel an upload is to make the reader
return an error.

Change-Id: Id70ea7d35526a2a98295168de26469e28fd127dd
Reviewed-on: https://review.monogon.dev/c/monogon/+/4048
Tested-by: Jenkins CI
Reviewed-by: Tim Windelschmidt <tim@monogon.tech>
diff --git a/go.mod b/go.mod
index 6c3213c..71c1751 100644
--- a/go.mod
+++ b/go.mod
@@ -100,7 +100,7 @@
 	github.com/opencontainers/runc v1.2.2
 	github.com/packethost/packngo v0.29.0
 	github.com/pkg/errors v0.9.1
-	github.com/pkg/sftp v1.13.1
+	github.com/pkg/sftp v1.13.8
 	github.com/prometheus/client_golang v1.21.0
 	github.com/prometheus/node_exporter v1.9.0
 	github.com/rivo/uniseg v0.4.7
diff --git a/go.sum b/go.sum
index d828426..baddf28 100644
--- a/go.sum
+++ b/go.sum
@@ -3182,8 +3182,9 @@
 github.com/pkg/errors v0.9.1/go.mod h1:bwawxfHBFNV+L2hUp1rHADufV3IMtnDRdf1r5NINEl0=
 github.com/pkg/profile v1.2.1/go.mod h1:hJw3o1OdXxsrSjjVksARp5W95eeEaEfptyVZyv6JUPA=
 github.com/pkg/sftp v1.10.1/go.mod h1:lYOWFsE0bwd1+KfKJaKeuokY15vzFx25BLbzYYoAxZI=
-github.com/pkg/sftp v1.13.1 h1:I2qBYMChEhIjOgazfJmV3/mZM256btk6wkCDRmW7JYs=
 github.com/pkg/sftp v1.13.1/go.mod h1:3HaPG6Dq1ILlpPZRO0HVMrsydcdLt6HRDccSgb87qRg=
+github.com/pkg/sftp v1.13.8 h1:Xt7eJ/xqXv7s0VuzFw7JXhZj6Oc1zI6l4GK8KP9sFB0=
+github.com/pkg/sftp v1.13.8/go.mod h1:DmvEkvKE2lshEeuo2JMp06yqcx9HVnR7e3zqQl42F3U=
 github.com/pkg/xattr v0.4.1 h1:dhclzL6EqOXNaPDWqoeb9tIxATfBSmjqL0b4DpSjwRw=
 github.com/pkg/xattr v0.4.1/go.mod h1:W2cGD0TBEus7MkUgv0tNZ9JutLtVO3cXu+IBRuHqnFs=
 github.com/pmezard/go-difflib v0.0.0-20151028094244-d8ed2627bdf0/go.mod h1:iKH77koFhYxTK1pcRnkKkqfTogsbg7gZNVY4sRDYZ/4=
@@ -3835,6 +3836,7 @@
 golang.org/x/crypto v0.25.0/go.mod h1:T+wALwcMOSE0kXgUAnPAHqTLW+XHgcELELW8VaDgm/M=
 golang.org/x/crypto v0.26.0/go.mod h1:GY7jblb9wI+FOo5y8/S2oY4zWP07AkOJ4+jxCqdqn54=
 golang.org/x/crypto v0.28.0/go.mod h1:rmgy+3RHxRZMyY0jjAJShp2zgEdOqj2AO7U0pYmeQ7U=
+golang.org/x/crypto v0.31.0/go.mod h1:kDsLvtWBEx7MV9tJOj9bnXsPbxwJQ6csT/x4KIN4Ssk=
 golang.org/x/crypto v0.36.0 h1:AnAEvhDddvBdpY+uR+MyHmuZzzNqXSe/GvuDeob5L34=
 golang.org/x/crypto v0.36.0/go.mod h1:Y4J0ReaxCR1IMaabaSMugxJES1EpwhBHhv2bDHklZvc=
 golang.org/x/exp v0.0.0-20180321215751-8460e604b9de/go.mod h1:CJ0aWSM057203Lf6IL+f9T1iT9GByDxfZKAQTCR3kQA=
@@ -4112,6 +4114,7 @@
 golang.org/x/sync v0.6.0/go.mod h1:Czt+wKu1gCyEFDUtn0jG5QVvpJ6rzVqr5aXyt9drQfk=
 golang.org/x/sync v0.7.0/go.mod h1:Czt+wKu1gCyEFDUtn0jG5QVvpJ6rzVqr5aXyt9drQfk=
 golang.org/x/sync v0.8.0/go.mod h1:Czt+wKu1gCyEFDUtn0jG5QVvpJ6rzVqr5aXyt9drQfk=
+golang.org/x/sync v0.10.0/go.mod h1:Czt+wKu1gCyEFDUtn0jG5QVvpJ6rzVqr5aXyt9drQfk=
 golang.org/x/sync v0.12.0 h1:MHc5BpPuC30uJk597Ri8TV3CNZcTLu6B6z4lJy+g6Jw=
 golang.org/x/sync v0.12.0/go.mod h1:1dzgHSNfp02xaA81J2MS99Qcpr2w7fw1gpm99rleRqA=
 golang.org/x/sys v0.0.0-20180224232135-f6cff0780e54/go.mod h1:STP8DvDyc/dI5b8T5hshtkjS+E42TnysNCUPdjciGhY=
@@ -4314,6 +4317,7 @@
 golang.org/x/sys v0.23.0/go.mod h1:/VUhepiaJMQUp4+oa/7Zr1D23ma6VTLIYjOOTFZPUcA=
 golang.org/x/sys v0.24.0/go.mod h1:/VUhepiaJMQUp4+oa/7Zr1D23ma6VTLIYjOOTFZPUcA=
 golang.org/x/sys v0.26.0/go.mod h1:/VUhepiaJMQUp4+oa/7Zr1D23ma6VTLIYjOOTFZPUcA=
+golang.org/x/sys v0.28.0/go.mod h1:/VUhepiaJMQUp4+oa/7Zr1D23ma6VTLIYjOOTFZPUcA=
 golang.org/x/sys v0.29.0/go.mod h1:/VUhepiaJMQUp4+oa/7Zr1D23ma6VTLIYjOOTFZPUcA=
 golang.org/x/sys v0.31.0 h1:ioabZlmFYtWhL+TRYpcnNlLwhyxaM9kWTDEmfnprqik=
 golang.org/x/sys v0.31.0/go.mod h1:BJP2sWEmIv4KK5OTEluFJCKSidICx8ciO85XgH3Ak8k=
@@ -4349,6 +4353,7 @@
 golang.org/x/term v0.22.0/go.mod h1:F3qCibpT5AMpCRfhfT53vVJwhLtIVHhB9XDjfFvnMI4=
 golang.org/x/term v0.23.0/go.mod h1:DgV24QBUrK6jhZXl+20l6UWznPlwAHm1Q1mGHtydmSk=
 golang.org/x/term v0.25.0/go.mod h1:RPyXicDX+6vLxogjjRxjgD2TKtmAO6NZBsBRfrOLu7M=
+golang.org/x/term v0.27.0/go.mod h1:iMsnZpn0cago0GOrHO2+Y7u7JPn5AylBrcoWkElMTSM=
 golang.org/x/term v0.30.0 h1:PQ39fJZ+mfadBm0y5WlL4vlM7Sx1Hgf13sMIY2+QS9Y=
 golang.org/x/term v0.30.0/go.mod h1:NYYFdzHoI5wRh/h5tDMdMqCqPJZEuNqVR5xJLd/n67g=
 golang.org/x/text v0.0.0-20170915032832-14c0d48ead0c/go.mod h1:NqM8EUOU14njkJ3fqMW+pc6Ldnwhi/IjpwHt7yyuwOQ=
@@ -4376,6 +4381,7 @@
 golang.org/x/text v0.16.0/go.mod h1:GhwF1Be+LQoKShO3cGOHzqOgRrGaYc9AvblQOmPVHnI=
 golang.org/x/text v0.17.0/go.mod h1:BuEKDfySbSR4drPmRPG/7iBdf8hvFMuRexcpahXilzY=
 golang.org/x/text v0.19.0/go.mod h1:BuEKDfySbSR4drPmRPG/7iBdf8hvFMuRexcpahXilzY=
+golang.org/x/text v0.21.0/go.mod h1:4IBbMaMmOPCJ8SecivzSH54+73PCFmPWxNTLm+vZkEQ=
 golang.org/x/text v0.23.0 h1:D71I7dUrlY+VX0gQShAThNGHFxZ13dGLBHQLVl1mJlY=
 golang.org/x/text v0.23.0/go.mod h1:/BLNzu4aZCJ1+kcD0DNRotWKage4q2rGVAg4o22unh4=
 golang.org/x/time v0.0.0-20180412165947-fbb02b2291d2/go.mod h1:tRJNPiyCQ0inRvYxbN9jk5I+vvW/OXSQhTDSoE431IQ=
diff --git a/osbase/net/sshtakeover/sshtakeover.go b/osbase/net/sshtakeover/sshtakeover.go
index 20a70d2..b8fd8b2 100644
--- a/osbase/net/sshtakeover/sshtakeover.go
+++ b/osbase/net/sshtakeover/sshtakeover.go
@@ -79,31 +79,32 @@
 	}
 }
 
+type contextReader struct {
+	r   io.Reader
+	ctx context.Context
+}
+
+func (r *contextReader) Read(p []byte) (n int, err error) {
+	if r.ctx.Err() != nil {
+		return 0, r.ctx.Err()
+	}
+	return r.r.Read(p)
+}
+
 // Upload a given blob to a targetPath on the system.
 func (p *Client) Upload(ctx context.Context, targetPath string, src io.Reader) error {
+	src = &contextReader{r: src, ctx: ctx}
+
 	df, err := p.sc.Create(targetPath)
 	if err != nil {
 		return fmt.Errorf("while creating file on the host: %w", err)
 	}
-
-	doneC := make(chan error, 1)
-
-	go func() {
-		_, err := df.ReadFromWithConcurrency(src, 0)
-		df.Close()
-		doneC <- err
-	}()
-
-	select {
-	case err := <-doneC:
-		if err != nil {
-			return fmt.Errorf("while copying file: %w", err)
-		}
-	case <-ctx.Done():
-		df.Close()
-		return ctx.Err()
+	_, err = df.ReadFromWithConcurrency(src, 0)
+	closeErr := df.Close()
+	if err != nil {
+		return err
 	}
-	return nil
+	return closeErr
 }
 
 // UploadExecutable uploads a given blob to a targetPath on the system