slice 8C Phase A: agent disk endpoints + data-bearing classifier gate + mkfs (v0.12.0)

internal/storage: mkfs executor (Format, device-pinned, narrow FELHOM_FORMAT
sudoers) + data-bearing device inspection (InspectDevice/DeviceProbe via
blkid+lsblk; conservative — ambiguous=data-bearing). internal/localapi: /disks
(+ data-bearing flag), /disks/assign (EnsureMount), /disks/eject (Unmount +
dependent guests), /disks/format. SECURITY CENTERPIECE: the agent inspects the
device itself; data-bearing format -> ClassStorageWipe gate -> pending_signature
refused; the caller's claim is never trusted. Additive (no controller change yet).

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

internal/storage/validate.go

@@ -25,6 +25,16 @@ var (
 	// smartctl is run against. Anything else is refused.
 	reSMARTDevice = regexp.MustCompile(`^/dev/(sd[a-z]+|nvme[0-9]+n[0-9]+|hd[a-z]+|vd[a-z]+)$`)
 
+	// Block device for inspection / mkfs: a raw disk OR a partition under /dev. Like the SMART
+	// whitelist but also allows the trailing partition number (sda1, nvme0n1p2, vdb3). No
+	// by-* symlinks, no device-mapper, no traversal. This is the mkfs/inspect target — it is
+	// validated AND the agent device-inspects it before any destructive decision (8C).
+	reBlockDevice = regexp.MustCompile(`^/dev/(sd[a-z]+[0-9]*|nvme[0-9]+n[0-9]+(p[0-9]+)?|hd[a-z]+[0-9]*|vd[a-z]+[0-9]*)$`)
+
+	// Filesystem types the agent will mkfs. Deliberately tiny — the sudoers mkfs entries are
+	// per-fstype binaries (mkfs.ext4 / mkfs.xfs), so this set MUST match those entries.
+	reFSType = regexp.MustCompile(`^(ext4|xfs)$`)
+
 	// LVM VG / pool names: LVM permits [A-Za-z0-9._+-]; we forbid leading '-' (would look
 	// like a flag) and cap the length.
 	reLVMName = regexp.MustCompile(`^[A-Za-z0-9_+.][A-Za-z0-9_+.-]*$`)
@@ -106,6 +116,25 @@ func ValidateSMARTDevice(device string) error {
 	return nil
 }
 
+// ValidateBlockDevice accepts only a raw disk or partition path under /dev (the mkfs / inspect
+// target). The same strict-whitelist discipline as ValidateSMARTDevice: no symlinks, no
+// device-mapper, no traversal — refused before any command is built.
+func ValidateBlockDevice(device string) error {
+	if !reBlockDevice.MatchString(device) {
+		return fmt.Errorf("storage: refusing to operate on non-whitelisted block device %q", device)
+	}
+	return nil
+}
+
+// ValidateFSType accepts only a filesystem type the agent is configured to mkfs (ext4|xfs). The
+// set MUST match the per-fstype sudoers entries.
+func ValidateFSType(fstype string) error {
+	if !reFSType.MatchString(fstype) {
+		return fmt.Errorf("storage: unsupported filesystem type %q (want ext4|xfs)", fstype)
+	}
+	return nil
+}
+
 // ValidateLVMName accepts an LVM VG or LV (pool) name.
 func ValidateLVMName(name string) error {
 	if name == "" {