msa-agent/internal/config/config_test.go

package config

import (
	"fmt"
	"os"
	"path/filepath"
	"strings"
	"syscall"
	"testing"
)

// The interesting property is not that a good file parses, it is that a bad one is refused at boot.
// An agent that starts half-configured sits there answering nothing, and "why does nothing work" is
// much harder to diagnose than a service that will not start.
func valid() File {
	return File{
		NodeID:     "nd_7f3a9c2e",
		RelayURL:   "https://relay.example",
		AgentToken: "tok",
		LocalPort:  8788,
		SignKey:    "AAAA",
		KxKey:      "AAAA",
		AuditPath:  "/var/log/msa-agent/audit.log",
		Devices:    []Device{{ID: "ap_5b1d0000", SignKey: "AAAA"}},
	}
}

func TestValidateAcceptsACompleteFile(t *testing.T) {
	if err := valid().Validate(false); err != nil {
		t.Fatalf("a complete file was refused: %v", err)
	}
}

// Pair mode relaxes exactly one rule: an empty device list is the starting state of a node that
// has not been paired yet, not a misconfiguration. Every other field still validates, because a
// pair-mode agent with a broken nodeId pairs successfully and then commands nothing.
func TestPairModeRelaxesOnlyTheDeviceList(t *testing.T) {
	cfg := valid()
	cfg.Devices = nil
	if err := cfg.Validate(true); err != nil {
		t.Fatalf("pair mode refused an empty device list: %v", err)
	}
	cfg.NodeID = "node-1"
	if err := cfg.Validate(true); err == nil {
		t.Fatal("pair mode accepted a malformed nodeId")
	}
}

func TestSaveRoundTripsAndIsSixHundred(t *testing.T) {
	path := filepath.Join(t.TempDir(), "config.json")
	cfg := valid()
	if err := Save(path, cfg); err != nil {
		t.Fatalf("Save: %v", err)
	}
	info, err := os.Stat(path)
	if err != nil {
		t.Fatal(err)
	}
	if info.Mode().Perm() != 0o600 {
		t.Fatalf("saved config mode is %v, want 0600", info.Mode().Perm())
	}
	reloaded, err := Load(path)
	if err != nil {
		t.Fatalf("Load after Save: %v", err)
	}
	if reloaded.NodeID != cfg.NodeID || len(reloaded.Devices) != 1 ||
		reloaded.Devices[0].SignKey != cfg.Devices[0].SignKey {
		t.Fatalf("round-trip lost fields: %+v", reloaded)
	}
}

// A rewrite must keep the file's owner. The deployment document tells the operator to run --pair
// with sudo while the installed config belongs to the msa-agent user; without preserving ownership
// the rename would leave a root-owned 0600 file that the systemd unit cannot read, so the pairing
// would look successful and the node would come up unable to load its own configuration.
//
// The test cannot become root, so it asserts the property that is observable without privileges:
// the owner after a save is the same as the owner before it, and the temp file does not survive.
func TestSavePreservesTheFileOwner(t *testing.T) {
	path := filepath.Join(t.TempDir(), "config.json")
	cfg := valid()
	if err := Save(path, cfg); err != nil {
		t.Fatalf("first Save: %v", err)
	}
	before := owner(t, path)
	// A second save goes through the ownership-preserving path. The inode necessarily changes — the
	// write is a temp file plus a rename — so what is compared is the owner, which is the thing the
	// rename would otherwise reset.
	cfg.Devices = append(cfg.Devices, Device{
		ID: "ap_second0001", SignKey: cfg.Devices[0].SignKey, RelayToken: strings.Repeat("b", 48),
	})
	if err := Save(path, cfg); err != nil {
		t.Fatalf("second Save: %v", err)
	}
	after := owner(t, path)
	if before != after {
		t.Fatalf("the rewrite changed the owner from %v to %v", before, after)
	}
	if _, err := os.Stat(path + ".tmp"); !os.IsNotExist(err) {
		t.Fatal("a temp file was left behind")
	}
	reloaded, err := Load(path)
	if err != nil {
		t.Fatalf("Load after rewrite: %v", err)
	}
	if len(reloaded.Devices) != 2 {
		t.Fatalf("the rewrite lost a device: %d", len(reloaded.Devices))
	}
}

// A save must not be able to write a file that the next boot would refuse: the validation runs
// before the rename, so a caller building a device list with a bad id gets an error, not a
// corrupted file.
func TestSaveRefusesAnInvalidFile(t *testing.T) {
	path := filepath.Join(t.TempDir(), "config.json")
	cfg := valid()
	cfg.Devices[0].ID = "not-an-app-id"
	if err := Save(path, cfg); err == nil {
		t.Fatal("saved a device list the loader would refuse")
	}
	if _, err := os.Stat(path); !os.IsNotExist(err) {
		t.Fatal("a failed save left a file behind")
	}
}

func TestValidateNamesEveryMissingField(t *testing.T) {
	cases := map[string]func(*File){
		"nodeId":    func(c *File) { c.NodeID = "" },
		"relayUrl":  func(c *File) { c.RelayURL = "" },
		"token":     func(c *File) { c.AgentToken = "" },
		"signKey":   func(c *File) { c.SignKey = "" },
		"kxKey":     func(c *File) { c.KxKey = "" },
		"auditPath": func(c *File) { c.AuditPath = "" },
		"devices":   func(c *File) { c.Devices = nil },
		"badNode":   func(c *File) { c.NodeID = "node-1" },
		"badApp":    func(c *File) { c.Devices[0].ID = "phone" },
		"noSignKey": func(c *File) { c.Devices[0].SignKey = "" },
		"port0":     func(c *File) { c.LocalPort = 0 },
		"portHigh":  func(c *File) { c.LocalPort = 70000 },
		"duplicate": func(c *File) { c.Devices = append(c.Devices, c.Devices[0]) },
	}
	for name, mutate := range cases {
		cfg := valid()
		mutate(&cfg)
		if err := cfg.Validate(false); err == nil {
			t.Errorf("%s: a broken config was accepted", name)
		}
	}
}

// There is no host field, and this test is what keeps it that way: a "localHost" entry would be the
// one setting able to turn the agent into a LAN pivot.
func TestThereIsNoHostField(t *testing.T) {
	raw := []byte(`{"nodeId":"nd_7f3a9c2e","relayUrl":"https://r","agentToken":"t","localHost":"10.0.0.5",
		"localPort":8788,"signKey":"AAAA","kxKey":"AAAA","auditPath":"/tmp/a.log",
		"devices":[{"id":"ap_5b1d0000","signKey":"AAAA"}]}`)
	path := filepath.Join(t.TempDir(), "config.json")
	if err := os.WriteFile(path, raw, 0o600); err != nil {
		t.Fatal(err)
	}
	cfg, err := Load(path)
	if err != nil {
		t.Fatal(err)
	}
	// The unknown field is ignored, and the port is all the agent knows about the local service.
	if cfg.LocalPort != 8788 {
		t.Fatalf("localPort is %d", cfg.LocalPort)
	}
}

func TestLoadReportsMissingAndMalformedFiles(t *testing.T) {
	if _, err := Load(filepath.Join(t.TempDir(), "absent.json")); err == nil {
		t.Fatal("a missing file was accepted")
	}
	path := filepath.Join(t.TempDir(), "broken.json")
	if err := os.WriteFile(path, []byte("{"), 0o600); err != nil {
		t.Fatal(err)
	}
	if _, err := Load(path); err == nil {
		t.Fatal("a malformed file was accepted")
	}
}

// owner reads the uid and gid of a path, which is what a rewrite must preserve.
func owner(t *testing.T, path string) string {
	t.Helper()
	info, err := os.Stat(path)
	if err != nil {
		t.Fatal(err)
	}
	stat, ok := info.Sys().(*syscall.Stat_t)
	if !ok {
		t.Skip("stat_t is not available on this platform")
	}
	return fmt.Sprintf("%d:%d", stat.Uid, stat.Gid)
}