v0.77.0: fork-4 — escrow the offsite restic repo password under R

IdentityBundle gains ResticRepoPassword (rides existing age-under-R
WrapIdentityBundle; custody spike febdc56 proved a recovered value opens the
real repo). POST /escrow/stage-secret (withGuest, scopedFromBody) transiently
stages the controller-pushed password (0600, atomic, NEVER logged), which the
escrow-create ceremony auto-injects then wipes. Adds AttachResticPassword +
StagedResticPasswordPath + WipeStagedResticPassword; EscrowStagePath injectable
for tests. Tests: bundle carries pw byte-exact + not-in-blob + wrong-R fails
closed; stage 0600 + non-secret ack + cross-guest 403 + value-not-in-log.
Additive; PBS-K escrow untouched. NOT yet live-validated (supervised ceremony).

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01PSK5g6qYLknKj8u3QAFEr6

internal/escrow/identity.go

@@ -30,6 +30,47 @@ type IdentityBundle struct {
 	// blobs created before S3 lack it and CANNOT be retro-fitted (R is never retained) — S5 DR
 	// falls back to fresh-key re-registration, which keeps the box's /32 (hub S2 re-key-in-place).
 	WGPrivateKey string `json:"wg_private_key,omitempty"`
+	// ResticRepoPassword is the offsite restic repo password (fork-4). OPTIONAL: escrow blobs created
+	// before fork-4 lack it and CANNOT be retro-fitted (R is never retained). It is the DATA key for the
+	// offsite tier — irreplaceable (unlike the SFTP access key, which is regenerable at DR). The
+	// controller's atomicity gate ensures no offsite ciphertext exists until this is escrowed.
+	ResticRepoPassword string `json:"restic_repo_password,omitempty"`
+}
+
+// StagedResticPasswordPath is the well-known 0600 file where the controller-pushed restic repo password
+// is transiently staged (by the local API) for the escrow-create ceremony to pick up, then wiped. A fixed
+// path so the local-API writer and the CLI ceremony reader agree without threading config through.
+func StagedResticPasswordPath() string {
+	return filepath.Join("/var/lib/felhom-agent", "escrow-stage", "restic_repo_password")
+}
+
+// WipeStagedResticPassword removes the staged restic password (called by the ceremony after a successful
+// escrow-create — the secret now lives only inside the R-wrapped blob). A missing file is a clean no-op.
+func WipeStagedResticPassword() error {
+	if err := os.Remove(StagedResticPasswordPath()); err != nil && !os.IsNotExist(err) {
+		return fmt.Errorf("escrow: wipe staged restic password: %w", err)
+	}
+	return nil
+}
+
+// AttachResticPassword injects the offsite restic repo password from the staged 0600 file into the bundle
+// when it exists (fork-4 escrow-create auto-inject). Returns whether it attached. The VALUE is validated
+// (non-empty) but NEVER logged by callers — log the field NAME only (mirrors AttachWGKey). A missing file
+// is a clean no-attach (pre-fork-4 behavior, byte-compatible bundle).
+func AttachResticPassword(b *IdentityBundle, stagePath string) (bool, error) {
+	raw, err := os.ReadFile(stagePath)
+	if err != nil {
+		if os.IsNotExist(err) {
+			return false, nil
+		}
+		return false, fmt.Errorf("escrow: reading staged restic password: %w", err)
+	}
+	pw := strings.TrimSpace(string(raw))
+	if pw == "" {
+		return false, fmt.Errorf("escrow: staged restic password file %s is empty", stagePath)
+	}
+	b.ResticRepoPassword = pw
+	return true, nil
 }
 
 // AttachWGKey injects the offsite WG private key into the bundle when the key file exists (S3