client: add support for machine-wide omaha clients

Uses machine id and boot id for user and session respectively, matching
the existing behavior of update_engine.

omaha/client/machine_linux.go

@@ -0,0 +1,75 @@
+// Copyright 2017 CoreOS, Inc.
+//
+// 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.
+
+// +build linux
+
+package client
+
+import (
+	"bytes"
+	"fmt"
+	"io/ioutil"
+)
+
+const (
+	machineIDPath = "/etc/machine-id"
+	bootIDPath    = "/proc/sys/kernel/random/boot_id"
+)
+
+// NewMachineClient creates a machine-wide client, updating applications
+// that may be used by multiple users. On Linux the system's machine id
+// is used as the user id, and boot id is used as the omaha session id.
+func NewMachineClient(serverURL string) (*Client, error) {
+	machineID, err := ioutil.ReadFile(machineIDPath)
+	if err != nil {
+		fmt.Errorf("omaha: failed to read machine id: %v", err)
+	}
+
+	machineID = bytes.TrimSpace(machineID)
+	// Although machineID should be a UUID, it is formatted as a
+	// plain hex string, omitting the normal '-' separators, so it
+	// should be 32 bytes long. It would be nice to reformat it to
+	// add the '-' chars but update_engine doesn't so stick with its
+	// behavior for now.
+	if len(machineID) < 32 {
+		fmt.Errorf("omaha: incomplete machine id: %q",
+			machineID)
+	}
+
+	bootID, err := ioutil.ReadFile(bootIDPath)
+	if err != nil {
+		fmt.Errorf("omaha: failed to read boot id: %v", err)
+	}
+
+	bootID = bytes.TrimSpace(bootID)
+	// unlike machineID, bootID *does* include '-' chars.
+	if len(bootID) < 36 {
+		fmt.Errorf("omaha: incomplete boot id: %q", bootID)
+	}
+
+	c := &Client{
+		apiClient:     newHTTPClient(),
+		clientVersion: "go-omaha",
+		userID:        string(machineID),
+		sessionID:     string(bootID),
+		isMachine:     true,
+		apps:          make(map[string]*AppClient),
+	}
+
+	if err := c.SetServerURL(serverURL); err != nil {
+		return nil, err
+	}
+
+	return c, nil
+}

omaha/client/machine_linux_test.go

@@ -0,0 +1,48 @@
+// Copyright 2017 CoreOS, Inc.
+//
+// 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.
+
+// +build linux
+
+package client
+
+import (
+	"bytes"
+	"io/ioutil"
+	"testing"
+)
+
+// skip test if external file isn't readable
+func readOrSkip(t *testing.T, name string) string {
+	data, err := ioutil.ReadFile(name)
+	if err != nil {
+		t.Skip(err)
+	}
+	return string(bytes.TrimSpace(data))
+}
+
+func TestNewMachine(t *testing.T) {
+	userID := readOrSkip(t, machineIDPath)
+	sessionID := readOrSkip(t, bootIDPath)
+
+	c, err := NewMachineClient("https://example.com")
+	if err != nil {
+		t.Fatal(err)
+	}
+	if c.userID != userID {
+		t.Errorf("%q != %q", c.userID, userID)
+	}
+	if c.sessionID != sessionID {
+		t.Errorf("%q != %q", c.sessionID, sessionID)
+	}
+}