feat(keys): add --keys flag to dump for cross-host decryption

Consumer side of the cross-host key workflow (pairs with #599).
ApplyDump wires StaticProviders from a dump.json into matching
browsers, so dump --keys f.json -p /copied/data decrypts without
native retrievers.

browser/keydump.go

@@ -1,6 +1,8 @@
 package browser
 
 import (
+	"runtime"
+
 	"github.com/moond4rk/hackbrowserdata/crypto/keyretriever"
 	"github.com/moond4rk/hackbrowserdata/log"
 )
@@ -69,3 +71,56 @@ func groupByInstallation(browsers []Browser) (map[string]*installGroup, []string
 	}
 	return groups, order
 }
+
+// ApplyDump installs master keys from dump onto matching browsers, replacing each browser's default
+// platform-native retrievers with StaticProviders backed by the Dump's bytes. Matching is by
+// (BrowserName, UserDataDir) — the same key BuildDump groups by. When exact match fails (commonly a
+// cross-host path mismatch: Windows backslash vs POSIX, or a relocated User Data dir via -p), falls
+// back to the sole vault for that browser name when one exists. Browsers without a matching vault
+// are warned and left untouched; non-KeyManager browsers (Firefox/Safari) are skipped silently.
+func ApplyDump(browsers []Browser, dump keyretriever.Dump) {
+	if dump.Host.OS != "" && dump.Host.OS != runtime.GOOS {
+		log.Infof("apply-keys: dump created on %s/%s; current host is %s/%s",
+			dump.Host.OS, dump.Host.Arch, runtime.GOOS, runtime.GOARCH)
+	}
+	vaultIndex := make(map[string]*keyretriever.Vault, len(dump.Vaults))
+	vaultsByBrowser := make(map[string][]*keyretriever.Vault)
+	for i := range dump.Vaults {
+		v := &dump.Vaults[i]
+		vaultIndex[v.Browser+"|"+v.UserDataDir] = v
+		vaultsByBrowser[v.Browser] = append(vaultsByBrowser[v.Browser], v)
+	}
+	for _, b := range browsers {
+		km, ok := b.(KeyManager)
+		if !ok {
+			continue
+		}
+		v, found := vaultIndex[b.BrowserName()+"|"+b.UserDataDir()]
+		if !found {
+			if candidates := vaultsByBrowser[b.BrowserName()]; len(candidates) == 1 {
+				v = candidates[0]
+				log.Infof("apply-keys: %s/%s using sole vault for browser (dump path %q != local %q)",
+					b.BrowserName(), b.ProfileName(), v.UserDataDir, b.UserDataDir())
+				found = true
+			}
+		}
+		if !found {
+			log.Warnf("apply-keys: %s/%s no matching vault in dump", b.BrowserName(), b.ProfileName())
+			continue
+		}
+		km.SetKeyRetrievers(keyretriever.Retrievers{
+			V10: maybeStaticProvider(v.Keys.V10),
+			V11: maybeStaticProvider(v.Keys.V11),
+			V20: maybeStaticProvider(v.Keys.V20),
+		})
+	}
+}
+
+// maybeStaticProvider wraps non-empty key bytes as a StaticProvider; an empty/nil key returns nil
+// to preserve the "tier not applicable" signal NewMasterKeys expects.
+func maybeStaticProvider(key []byte) keyretriever.KeyRetriever {
+	if len(key) == 0 {
+		return nil
+	}
+	return keyretriever.NewStaticProvider(key)
+}

browser/keydump_test.go

@@ -36,12 +36,15 @@ func (m *mockBrowser) CountEntries(_ []types.Category) (map[types.Category]int,
 
 type mockChromiumBrowser struct {
 	mockBrowser
-	keys      keyretriever.MasterKeys
-	exportErr error
-	calls     int
+	keys               keyretriever.MasterKeys
+	exportErr          error
+	calls              int
+	receivedRetrievers keyretriever.Retrievers
 }
 
-func (m *mockChromiumBrowser) SetKeyRetrievers(_ keyretriever.Retrievers) {}
+func (m *mockChromiumBrowser) SetKeyRetrievers(r keyretriever.Retrievers) {
+	m.receivedRetrievers = r
+}
 
 func (m *mockChromiumBrowser) ExportKeys() (keyretriever.MasterKeys, error) {
 	m.calls++
@@ -196,6 +199,127 @@ func TestBuildDump_PartialKeys(t *testing.T) {
 	}
 }
 
+func TestApplyDump_Match(t *testing.T) {
+	b := &mockChromiumBrowser{
+		mockBrowser: mockBrowser{name: chromeName, profile: testProfileDefault, userDataDir: testUDD},
+	}
+	dump := keyretriever.Dump{
+		Vaults: []keyretriever.Vault{
+			{Browser: chromeName, UserDataDir: testUDD, Keys: keyretriever.MasterKeys{V10: []byte("v10-from-dump")}},
+		},
+	}
+	ApplyDump([]Browser{b}, dump)
+
+	if b.receivedRetrievers.V10 == nil {
+		t.Fatal("V10 retriever should be set from matching vault")
+	}
+	got, err := b.receivedRetrievers.V10.RetrieveKey(keyretriever.Hints{})
+	if err != nil || string(got) != "v10-from-dump" {
+		t.Errorf("V10.RetrieveKey() = %q, err = %v, want %q", got, err, "v10-from-dump")
+	}
+	if b.receivedRetrievers.V11 != nil {
+		t.Errorf("V11 should be nil (tier not in dump), got %v", b.receivedRetrievers.V11)
+	}
+}
+
+func TestApplyDump_MissingVault(t *testing.T) {
+	b := &mockChromiumBrowser{
+		mockBrowser: mockBrowser{name: chromeName, profile: testProfileDefault, userDataDir: testUDD},
+	}
+	dump := keyretriever.Dump{
+		Vaults: []keyretriever.Vault{
+			{Browser: testEdgeName, UserDataDir: "/edge", Keys: keyretriever.MasterKeys{V10: []byte("v10")}},
+		},
+	}
+	ApplyDump([]Browser{b}, dump)
+
+	if b.receivedRetrievers.V10 != nil {
+		t.Errorf("V10 should remain nil when no matching vault, got %v", b.receivedRetrievers.V10)
+	}
+}
+
+func TestApplyDump_NonKeyManagerSkipped(t *testing.T) {
+	firefox := &mockBrowser{name: firefoxName, profile: "default-release", userDataDir: "/ff"}
+	dump := keyretriever.Dump{
+		Vaults: []keyretriever.Vault{
+			{Browser: firefoxName, UserDataDir: "/ff", Keys: keyretriever.MasterKeys{V10: []byte("v10")}},
+		},
+	}
+	// firefox does not implement KeyManager; ApplyDump must not panic and must not attempt injection.
+	ApplyDump([]Browser{firefox}, dump)
+}
+
+func TestApplyDump_RoundTrip(t *testing.T) {
+	src := &mockChromiumBrowser{
+		mockBrowser: mockBrowser{name: chromeName, profile: testProfileDefault, userDataDir: testUDD},
+		keys:        keyretriever.MasterKeys{V10: []byte("v10-rt"), V20: []byte("v20-rt")},
+	}
+	dump := BuildDump([]Browser{src})
+
+	dst := &mockChromiumBrowser{
+		mockBrowser: mockBrowser{name: chromeName, profile: testProfileDefault, userDataDir: testUDD},
+	}
+	ApplyDump([]Browser{dst}, dump)
+
+	v10, _ := dst.receivedRetrievers.V10.RetrieveKey(keyretriever.Hints{})
+	if string(v10) != "v10-rt" {
+		t.Errorf("V10 round-trip: got %q, want v10-rt", v10)
+	}
+	v20, _ := dst.receivedRetrievers.V20.RetrieveKey(keyretriever.Hints{})
+	if string(v20) != "v20-rt" {
+		t.Errorf("V20 round-trip: got %q, want v20-rt", v20)
+	}
+	if dst.receivedRetrievers.V11 != nil {
+		t.Errorf("V11 should be nil (not in source keys), got %v", dst.receivedRetrievers.V11)
+	}
+}
+
+func TestApplyDump_FallbackOnPathMismatch(t *testing.T) {
+	// Cross-host scenario: dump was created on Windows but is applied on Linux/macOS where the
+	// UserDataDir literally differs. With a single vault for the browser, ApplyDump should still
+	// inject — otherwise the primary cross-host use case fails silently.
+	b := &mockChromiumBrowser{
+		mockBrowser: mockBrowser{name: chromeName, profile: testProfileDefault, userDataDir: "/local/chrome"},
+	}
+	dump := keyretriever.Dump{
+		Vaults: []keyretriever.Vault{
+			{
+				Browser:     chromeName,
+				UserDataDir: `C:\Users\foo\AppData\Local\Google\Chrome\User Data`,
+				Keys:        keyretriever.MasterKeys{V10: []byte("v10-fallback")},
+			},
+		},
+	}
+	ApplyDump([]Browser{b}, dump)
+
+	if b.receivedRetrievers.V10 == nil {
+		t.Fatal("V10 retriever should be set via single-vault fallback")
+	}
+	got, err := b.receivedRetrievers.V10.RetrieveKey(keyretriever.Hints{})
+	if err != nil || string(got) != "v10-fallback" {
+		t.Errorf("V10.RetrieveKey() = %q, err = %v, want %q", got, err, "v10-fallback")
+	}
+}
+
+func TestApplyDump_NoFallbackWhenAmbiguous(t *testing.T) {
+	// Two Chrome vaults in the dump and no exact path match — ApplyDump must not guess which
+	// installation the local browser corresponds to.
+	b := &mockChromiumBrowser{
+		mockBrowser: mockBrowser{name: chromeName, profile: testProfileDefault, userDataDir: "/local/chrome"},
+	}
+	dump := keyretriever.Dump{
+		Vaults: []keyretriever.Vault{
+			{Browser: chromeName, UserDataDir: "/path/a", Keys: keyretriever.MasterKeys{V10: []byte("a")}},
+			{Browser: chromeName, UserDataDir: "/path/b", Keys: keyretriever.MasterKeys{V10: []byte("b")}},
+		},
+	}
+	ApplyDump([]Browser{b}, dump)
+
+	if b.receivedRetrievers.V10 != nil {
+		t.Errorf("V10 should remain nil when fallback is ambiguous, got %v", b.receivedRetrievers.V10)
+	}
+}
+
 func TestBuildDump_GroupingOrderIndependent(t *testing.T) {
 	for _, name := range []string{"p1 first", "p2 first"} {
 		t.Run(name, func(t *testing.T) {

cmd/hack-browser-data/dump.go

@@ -2,12 +2,14 @@ package main
 
 import (
 	"fmt"
+	"os"
 	"path/filepath"
 	"strings"
 
 	"github.com/spf13/cobra"
 
 	"github.com/moond4rk/hackbrowserdata/browser"
+	"github.com/moond4rk/hackbrowserdata/crypto/keyretriever"
 	"github.com/moond4rk/hackbrowserdata/log"
 	"github.com/moond4rk/hackbrowserdata/output"
 	"github.com/moond4rk/hackbrowserdata/types"
@@ -22,6 +24,7 @@ func dumpCmd() *cobra.Command {
 		outputDir    string
 		profilePath  string
 		keychainPw   string
+		keysPath     string
 		compress     bool
 	)
 
@@ -32,13 +35,10 @@ func dumpCmd() *cobra.Command {
   hack-browser-data dump -b chrome -c password,cookie
   hack-browser-data dump -b chrome -f json -d output
   hack-browser-data dump -f cookie-editor
+  hack-browser-data dump --keys dump.json -p /path/to/copied/User\ Data
   hack-browser-data dump --zip`,
 		RunE: func(cmd *cobra.Command, args []string) error {
-			browsers, err := browser.PickBrowsers(browser.PickOptions{
-				Name:             browserName,
-				ProfilePath:      profilePath,
-				KeychainPassword: keychainPw,
-			})
+			browsers, err := selectBrowsers(browserName, profilePath, keychainPw, keysPath)
 			if err != nil {
 				return err
 			}
@@ -86,11 +86,51 @@ func dumpCmd() *cobra.Command {
 	cmd.Flags().StringVarP(&outputDir, "dir", "d", "results", "output directory")
 	cmd.Flags().StringVarP(&profilePath, "profile-path", "p", "", "custom profile dir path, get with chrome://version")
 	cmd.Flags().StringVar(&keychainPw, "keychain-pw", "", "macOS keychain password")
+	cmd.Flags().StringVar(&keysPath, "keys", "", "import master keys from JSON file (from `keys export`), skipping platform retrieval")
 	cmd.Flags().BoolVar(&compress, "zip", false, "compress output to zip")
 
 	return cmd
 }
 
+// selectBrowsers returns wired-up browsers for either platform-native key retrieval (default) or
+// dump-based key injection (when keysPath is non-empty). The dump path uses DiscoverBrowsers so it
+// never triggers a keychain prompt or platform retrievers.
+func selectBrowsers(browserName, profilePath, keychainPw, keysPath string) ([]browser.Browser, error) {
+	if keysPath == "" {
+		return browser.PickBrowsers(browser.PickOptions{
+			Name:             browserName,
+			ProfilePath:      profilePath,
+			KeychainPassword: keychainPw,
+		})
+	}
+
+	if keychainPw != "" {
+		log.Warnf("--keychain-pw is ignored when --keys is set; platform key retrieval is skipped")
+	}
+
+	browsers, err := browser.DiscoverBrowsers(browser.PickOptions{
+		Name:        browserName,
+		ProfilePath: profilePath,
+	})
+	if err != nil {
+		return nil, err
+	}
+
+	f, err := os.Open(keysPath)
+	if err != nil {
+		return nil, fmt.Errorf("open keys file %s: %w", keysPath, err)
+	}
+	defer f.Close()
+
+	dump, err := keyretriever.ReadJSON(f)
+	if err != nil {
+		return nil, fmt.Errorf("read keys file %s: %w", keysPath, err)
+	}
+
+	browser.ApplyDump(browsers, dump)
+	return browsers, nil
+}
+
 // parseCategories converts a comma-separated string into a Category slice.
 // "all" returns all categories.
 func parseCategories(s string) ([]types.Category, error) {

crypto/keyretriever/dump.go

@@ -69,12 +69,16 @@ func (d Dump) WriteJSON(w io.Writer) error {
 	return nil
 }
 
-// ReadJSON parses a Dump from r.
+// ReadJSON parses a Dump from r and rejects schema versions this build cannot interpret —
+// 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
 }

crypto/keyretriever/dump_test.go

@@ -0,0 +1,41 @@
+package keyretriever
+
+import (
+	"bytes"
+	"strings"
+	"testing"
+)
+
+func TestReadJSON_RejectsUnknownVersion(t *testing.T) {
+	input := bytes.NewBufferString(`{"version":"99","created_at":"2026-05-16T00:00:00Z","host":{"os":"linux","arch":"amd64"},"vaults":[]}`)
+	_, err := ReadJSON(input)
+	if err == nil {
+		t.Fatal("ReadJSON should reject unknown version, got nil error")
+	}
+	if !strings.Contains(err.Error(), "unsupported dump version") {
+		t.Errorf("error should mention unsupported version, got: %v", err)
+	}
+}
+
+func TestReadJSON_RejectsMissingVersion(t *testing.T) {
+	input := bytes.NewBufferString(`{"created_at":"2026-05-16T00:00:00Z","host":{"os":"linux","arch":"amd64"},"vaults":[]}`)
+	_, err := ReadJSON(input)
+	if err == nil {
+		t.Fatal("ReadJSON should reject empty version, got nil error")
+	}
+}
+
+func TestReadJSON_AcceptsCurrentVersion(t *testing.T) {
+	d := NewDump()
+	var buf bytes.Buffer
+	if err := d.WriteJSON(&buf); err != nil {
+		t.Fatalf("WriteJSON: %v", err)
+	}
+	parsed, err := ReadJSON(&buf)
+	if err != nil {
+		t.Fatalf("ReadJSON: %v", err)
+	}
+	if parsed.Version != DumpVersion {
+		t.Errorf("Version = %q, want %q", parsed.Version, DumpVersion)
+	}
+}

crypto/keyretriever/static.go

@@ -0,0 +1,23 @@
+package keyretriever
+
+// StaticProvider returns pre-supplied master-key bytes; used by cross-host workflows where keys come
+// from a Dump rather than platform-native retrieval. RetrieveKey ignores Hints and returns the stored
+// bytes verbatim; an empty StaticProvider returns (nil, nil), the "not applicable" signal accepted
+// by NewMasterKeys when a tier was not present in the source Dump.
+type StaticProvider struct {
+	key []byte
+}
+
+// NewStaticProvider wraps key bytes as a KeyRetriever. A nil/empty key produces a provider that
+// reports the tier as unavailable (nil, nil) rather than returning a zero-length key.
+func NewStaticProvider(key []byte) *StaticProvider {
+	return &StaticProvider{key: key}
+}
+
+// RetrieveKey returns the stored key bytes, ignoring Hints.
+func (p *StaticProvider) RetrieveKey(_ Hints) ([]byte, error) {
+	if len(p.key) == 0 {
+		return nil, nil
+	}
+	return p.key, nil
+}