refactor: extract master-key code into masterkey package (#604)

masterkey/dump.go

@@ -0,0 +1,81 @@
+package masterkey
+
+import (
+	"encoding/json"
+	"fmt"
+	"io"
+	"os"
+	"os/user"
+	"runtime"
+	"time"
+)
+
+const DumpVersion = "1"
+
+// Dump is the portable, cross-host container for Chromium master keys — produce it on one host to
+// decrypt copied profile data on another without DPAPI / ABE / Keychain / D-Bus.
+type Dump struct {
+	Version   string    `json:"version"`
+	CreatedAt time.Time `json:"created_at"`
+	Host      Host      `json:"host"`
+	Vaults    []Vault   `json:"vaults"`
+}
+
+// Host OS / Arch always set; Hostname / User best-effort (empty on syscall failure).
+type Host struct {
+	OS       string `json:"os"`
+	Arch     string `json:"arch"`
+	Hostname string `json:"hostname,omitempty"`
+	User     string `json:"user,omitempty"`
+}
+
+// Vault groups profiles sharing master keys (master keys are per-installation, not per-profile).
+type Vault struct {
+	Browser     string     `json:"browser"`
+	UserDataDir string     `json:"user_data_dir"`
+	Profiles    []string   `json:"profiles"`
+	Keys        MasterKeys `json:"keys"`
+}
+
+func NewDump() Dump {
+	return Dump{
+		Version:   DumpVersion,
+		CreatedAt: time.Now().UTC(),
+		Host:      currentHost(),
+		Vaults:    []Vault{},
+	}
+}
+
+func currentHost() Host {
+	h := Host{OS: runtime.GOOS, Arch: runtime.GOARCH}
+	if name, err := os.Hostname(); err == nil {
+		h.Hostname = name
+	}
+	if u, err := user.Current(); err == nil {
+		h.User = u.Username
+	}
+	return h
+}
+
+func (d Dump) WriteJSON(w io.Writer) error {
+	enc := json.NewEncoder(w)
+	enc.SetIndent("", "  ")
+	if err := enc.Encode(d); err != nil {
+		return fmt.Errorf("encode dump: %w", err)
+	}
+	return nil
+}
+
+// ReadJSON parses a Dump and rejects versions this build can't interpret — a silent misparse of a
+// future v2 schema is worse than a clear error.
+func ReadJSON(r io.Reader) (Dump, error) {
+	var d Dump
+	dec := json.NewDecoder(r)
+	if err := dec.Decode(&d); err != nil {
+		return Dump{}, fmt.Errorf("decode dump: %w", err)
+	}
+	if d.Version != DumpVersion {
+		return Dump{}, fmt.Errorf("unsupported dump version %q (this build expects %q)", d.Version, DumpVersion)
+	}
+	return d, nil
+}