[testrunner] Add SSH runner

IN-824 #comment

Change-Id: Ia8de2e624dbc0a081e35db83677fc66b129f7602
diff --git a/go.sum b/go.sum
index cf60340..2c3692e 100644
--- a/go.sum
+++ b/go.sum
@@ -9,6 +9,7 @@
 github.com/golang/mock v1.1.1/go.mod h1:oTYuIxOrZwtPieC+H1uAHpcLFnEyAGVDL/k47Jfbm0A=
 github.com/golang/protobuf v1.2.0/go.mod h1:6lQm79b+lXiMfvg/cZm0SGofjICqVBUtrP5yJMmIC1U=
 github.com/google/go-cmp v0.2.0/go.mod h1:oXzfMopK8JAjlY9xF4vHSVASa0yLyX7SntLO5aqRK0M=
+github.com/google/pprof v0.0.0-20181206194817-3ea8567a2e57 h1:eqyIo2HjKhKe/mJzTG8n4VqvLXIOEG+SLdDqX7xGtkY=
 github.com/google/pprof v0.0.0-20181206194817-3ea8567a2e57/go.mod h1:zfwlbNMJ+OItoe0UupaVj+oy1omPYYDuagoSzA8v9mc=
 github.com/google/subcommands v0.0.0-20181012225330-46f0354f6315 h1:WW91Hq2v0qDzoPME+TPD4En72+d2Ue3ZMKPYfwR9yBU=
 github.com/google/subcommands v0.0.0-20181012225330-46f0354f6315/go.mod h1:ZjhPrFU+Olkh9WazFPsl27BQ4UPiG37m3yTrtFlrHVk=
@@ -16,6 +17,7 @@
 github.com/google/uuid v1.1.0/go.mod h1:TIyPZe4MgqvfeYDBFedMoGGpEw/LqOeaOT+nhxU+yHo=
 github.com/googleapis/gax-go v2.0.2+incompatible/go.mod h1:SFVmujtThgffbyetf+mdk2eWhX2bMyUtNHzFKcPA9HY=
 github.com/grpc-ecosystem/grpc-gateway v1.5.0/go.mod h1:RSKVYQBd5MCa4OVpNdGskqpgL2+G+NZTnrVHpWWfpdw=
+github.com/ianlancetaylor/demangle v0.0.0-20181102032728-5e5cf60278f6 h1:UDMh68UUwekSh5iP2OMhRRZJiiBccgV7axzUG8vi56c=
 github.com/ianlancetaylor/demangle v0.0.0-20181102032728-5e5cf60278f6/go.mod h1:aSSvb/t6k1mPoxDqO4vJh6VOCGPwU4O0C2/Eqndh1Sc=
 github.com/kisielk/gotool v1.0.0/go.mod h1:XhKaO+MFFWcvkIS/tQcRk01m1F5IRFswLeQ+oQHNcck=
 github.com/matttproud/golang_protobuf_extensions v1.0.1/go.mod h1:D8He9yQNgCq6Z5Ld7szi9bcBfOoFv/3dc6xSMkL2PC0=
@@ -27,6 +29,7 @@
 go.chromium.org/luci v0.0.0-20181218015242-20acb618582d h1:WWlp6PQtC8FyaxytRO5UBYFBDcPOYy6+o7JmcvgLMuU=
 go.chromium.org/luci v0.0.0-20181218015242-20acb618582d/go.mod h1:MIQewVTLvOvc0UioV0JNqTNO/RspKFS0XEeoKrOxsdM=
 go.opencensus.io v0.18.0/go.mod h1:vKdFvxhtzZ9onBp9VKHK8z/sRpBMnKAsufL7wlDrCOA=
+golang.org/x/arch v0.0.0-20181203225421-5a4828bb7045 h1:Pn8fQdvx+z1avAi7fdM2kRYWQNxGlavNDSyzrQg2SsU=
 golang.org/x/arch v0.0.0-20181203225421-5a4828bb7045/go.mod h1:cYlCBUl1MsqxdiKgmc4uh7TxZfWSFLOGSRR090WDxt8=
 golang.org/x/crypto v0.0.0-20181203042331-505ab145d0a9 h1:mKdxBk7AujPs8kU4m80U72y/zjbZ3UcXC7dClwKbUI0=
 golang.org/x/crypto v0.0.0-20181203042331-505ab145d0a9/go.mod h1:6SG95UA2DQfeDnfUPMdvaQW0Q7yPrPDi9nlGo2tz2b4=
diff --git a/testrunner/ssh_runner.go b/testrunner/ssh_runner.go
new file mode 100644
index 0000000..a8e99cb
--- /dev/null
+++ b/testrunner/ssh_runner.go
@@ -0,0 +1,48 @@
+package testrunner
+
+import (
+	"context"
+	"fmt"
+	"io"
+	"strings"
+	"time"
+
+	"golang.org/x/crypto/ssh"
+)
+
+// SSHRunner runs commands over SSH.
+type SSHRunner struct {
+	Timeout time.Duration
+	Session *ssh.Session
+}
+
+func (r *SSHRunner) Run(ctx context.Context, command []string, stdout io.Writer, stderr io.Writer) error {
+	// Set a default timeout if none was given.
+	if r.Timeout == time.Duration(0) {
+		r.Timeout = defaultTimeout
+	}
+
+	r.Session.Stdout = stdout
+	r.Session.Stderr = stderr
+	cmd := strings.Join(command, " ")
+
+	ctx, cancel := context.WithTimeout(ctx, r.Timeout)
+	defer cancel()
+
+	if err := r.Session.Start(cmd); err != nil {
+		return err
+	}
+
+	done := make(chan error)
+	go func() {
+		done <- r.Session.Wait()
+	}()
+
+	select {
+	case err := <-done:
+		return err
+	case <-ctx.Done():
+		r.Session.Signal(ssh.SIGKILL)
+	}
+	return fmt.Errorf("command timed out after %v", r.Timeout)
+}