Shares: allow any folder, not only ZFS datasets

SMB shares and NFS exports may now point to any existing directory
(USB disks under /mnt or /media, /srv, home folders...) instead of only
ZFS dataset mountpoints. System trees (/etc, /usr, /var, /boot, /proc,
/root, ...) are refused, also after resolving symlinks. The path
suggestions list mounted data filesystems from /proc/self/mounts in
addition to ZFS mountpoints.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

internal/web/server.go

@@ -9,6 +9,7 @@ import (
 	"log"
 	"math"
 	"net/http"
+	"path/filepath"
 	"strings"
 	"sync"
 	"time"
@@ -38,7 +39,10 @@ type Server struct {
 	pages  map[string]*template.Template
 	mux    *http.ServeMux
 
-	dirExists func(string) bool // share path check; replaced in tests
+	// share path checks; replaced in tests
+	dirExists  func(string) bool
+	realPath   func(string) (string, error)
+	readMounts func() string
 
 	mu       sync.Mutex
 	shareErr string // last failed Apply of the share config
@@ -47,7 +51,8 @@ type Server struct {
 func New(cfg *config.Store, st *store.Store, ring *history.Ring, sch *sched.Scheduler, sh *shares.Store) *Server {
 	run := hostrun.Auto()
 	s := &Server{cfg: cfg, st: st, ring: ring, sch: sch, send: alert.SendMail,
-		admin: zfsadm.New(zfsadm.NoInput(run)), shares: sh, shm: shares.New(run), dirExists: statDir, mux: http.NewServeMux()}
+		admin: zfsadm.New(zfsadm.NoInput(run)), shares: sh, shm: shares.New(run),
+		dirExists: statDir, realPath: filepath.EvalSymlinks, readMounts: procMounts, mux: http.NewServeMux()}
 	s.pages = map[string]*template.Template{}
 	layout := template.Must(template.New("layout").Funcs(funcs).ParseFS(assets, "templates/layout.html"))
 	for _, name := range []string{"dashboard", "disk", "zfs", "alerts", "settings", "shares"} {

internal/web/shares.go

@@ -53,21 +53,39 @@ func (s *Server) setApplyErr(e string) {
 	s.mu.Unlock()
 }
 
-// mountpoints lists dataset mountpoints — the only places shares may point to.
-func mountpoints(st sched.Status) []string {
+// pathSuggestions lists ZFS dataset mountpoints plus other mounted data
+// filesystems (USB disks, /mnt, /srv…) for the path input. Any non-system
+// folder may be shared; these are only hints.
+func (s *Server) pathSuggestions(st sched.Status) []string {
+	seen := map[string]bool{}
 	var out []string
-	for _, d := range st.Datasets {
-		if strings.HasPrefix(d.Mountpoint, "/") {
-			out = append(out, d.Mountpoint)
+	add := func(p string) {
+		if strings.HasPrefix(p, "/") && !seen[p] && shares.ValidateNotSystem(p) == nil {
+			seen[p] = true
+			out = append(out, p)
 		}
 	}
+	for _, d := range st.Datasets {
+		add(d.Mountpoint)
+	}
+	for _, p := range shares.ParseMounts(s.readMounts()) {
+		add(p)
+	}
 	sort.Strings(out)
 	return out
 }
 
+func procMounts() string {
+	b, err := os.ReadFile("/proc/self/mounts")
+	if err != nil {
+		return ""
+	}
+	return string(b)
+}
+
 func (s *Server) sharesView(st sched.Status, form smbForm, nform nfsForm) sharesVM {
 	c := s.shares.Get()
-	vm := sharesVM{C: c, Svc: st.Services, Mountpoints: mountpoints(st), Owner: s.shm.Owner, Host: st.Host,
+	vm := sharesVM{C: c, Svc: st.Services, Mountpoints: s.pathSuggestions(st), Owner: s.shm.Owner, Host: st.Host,
 		Form: form, NForm: nform, ApplyErr: s.applyErr(), Squashes: []string{"root", "all", "none"}}
 	if vm.Form.Name == "" && vm.Form.Orig == "" {
 		vm.Form.New, vm.Form.Guest, vm.Form.Browseable, vm.Form.HideSys = true, true, true, true
@@ -147,17 +165,22 @@ func (s *Server) sharesDone(w http.ResponseWriter, r *http.Request, msg, anchor
 	http.Redirect(w, r, "/shares?msg="+url.QueryEscape(msg)+anchor, http.StatusSeeOther)
 }
 
-// pathOK checks that a share path exists and lies inside a ZFS dataset.
-func (s *Server) pathOK(st sched.Status, p string) error {
+// pathOK checks that a share path is an existing, non-system directory, also
+// after resolving symlinks (so /tank/link -> /etc is refused).
+func (s *Server) pathOK(p string) error {
 	if err := shares.ValidatePath(p); err != nil {
 		return err
 	}
-	if !shares.UnderRoots(p, mountpoints(st)) {
-		return errPathOutside
-	}
 	if !s.dirExists(p) {
 		return errPathMissing
 	}
+	rp, err := s.realPath(p)
+	if err != nil {
+		return errPathMissing
+	}
+	if rp != p && shares.ValidateNotSystem(rp) != nil {
+		return strErr("path resolves to " + rp + ", a system directory")
+	}
 	return nil
 }
 
@@ -170,10 +193,7 @@ type strErr string
 
 func (e strErr) Error() string { return string(e) }
 
-const (
-	errPathOutside = strErr("path must be inside a ZFS dataset (see the list of mountpoints)")
-	errPathMissing = strErr("path does not exist or is not a directory")
-)
+const errPathMissing = strErr("path does not exist or is not a directory")
 
 func (s *Server) smbSettings(w http.ResponseWriter, r *http.Request) {
 	if err := r.ParseForm(); err != nil {
@@ -210,7 +230,6 @@ func (s *Server) smbSave(w http.ResponseWriter, r *http.Request) {
 	if len(f.Path) > 1 {
 		f.Path = strings.TrimRight(f.Path, "/")
 	}
-	st := s.sch.Status()
 	sh := shares.SMBShare{Name: f.Name, Path: f.Path, Comment: f.Comment, ReadOnly: f.ReadOnly, Guest: f.Guest,
 		Users: f.Users, Browseable: f.Browseable, HideSysFiles: f.HideSys}
 	if sh.Guest {
@@ -220,7 +239,7 @@ func (s *Server) smbSave(w http.ResponseWriter, r *http.Request) {
 		s.sharesFail(w, r, "Not saved: "+err.Error(), f, nfsForm{})
 		return
 	}
-	if err := s.pathOK(st, sh.Path); err != nil {
+	if err := s.pathOK(sh.Path); err != nil {
 		s.sharesFail(w, r, "Not saved: "+err.Error(), f, nfsForm{})
 		return
 	}
@@ -276,13 +295,12 @@ func (s *Server) nfsSave(w http.ResponseWriter, r *http.Request) {
 	if len(f.Path) > 1 {
 		f.Path = strings.TrimRight(f.Path, "/")
 	}
-	st := s.sch.Status()
 	e := shares.NFSExport{Path: f.Path, Clients: shares.SplitList(f.Clients), ReadOnly: f.ReadOnly, Squash: f.Squash, Async: f.Async}
 	if err := e.Validate(); err != nil {
 		s.sharesFail(w, r, "Not saved: "+err.Error(), smbForm{}, f)
 		return
 	}
-	if err := s.pathOK(st, e.Path); err != nil {
+	if err := s.pathOK(e.Path); err != nil {
 		s.sharesFail(w, r, "Not saved: "+err.Error(), smbForm{}, f)
 		return
 	}

internal/web/shares_test.go

@@ -68,7 +68,7 @@ func TestSharesSMBFlow(t *testing.T) {
 
 	// page lists users and mountpoints, prefills from ?path=
 	body := get(srv, "/shares?path=/tank/data").Body.String()
-	for _, want := range []string{`value="/tank/data"`, `value="data"`, `value="alice"`, "No SMB shares yet"} {
+	for _, want := range []string{`value="/tank/data"`, `value="data"`, `value="alice"`, "No SMB shares yet", `<option value="/mnt/usb">`} {
 		if !strings.Contains(body, want) {
 			t.Errorf("shares page missing %q", want)
 		}
@@ -96,10 +96,14 @@ func TestSharesSMBFlow(t *testing.T) {
 		t.Errorf("share not listed")
 	}
 
-	// refused: duplicate name, path outside pools, non-guest without users, reserved name, unclean path
+	// refused: duplicate name, system dirs, symlink into a system dir, missing dir,
+	// non-guest without users, reserved name, unclean path
 	for _, form := range []url.Values{
 		{"name": {"data"}, "path": {"/tank/data"}, "guest": {"1"}},
 		{"name": {"etc"}, "path": {"/etc"}, "guest": {"1"}},
+		{"name": {"logs"}, "path": {"/var/log"}, "guest": {"1"}},
+		{"name": {"evil"}, "path": {"/srv/evil"}, "guest": {"1"}},
+		{"name": {"nowhere"}, "path": {"/opt/nowhere"}, "guest": {"1"}},
 		{"name": {"priv"}, "path": {"/tank/data"}},
 		{"name": {"global"}, "path": {"/tank/data"}, "guest": {"1"}},
 		{"name": {"gone"}, "path": {"/tank/nope/.."}, "guest": {"1"}},
@@ -125,6 +129,12 @@ func TestSharesSMBFlow(t *testing.T) {
 	if !strings.Contains(f.written(shares.DefaultSMBConf), "valid users = alice") {
 		t.Errorf("smb.conf not regenerated after edit")
 	}
+	// a plain folder outside any ZFS dataset
+	rec = postForm(srv, "/shares/smb/save", url.Values{"name": {"media"}, "path": {"/srv/media"}, "guest": {"1"}, "browseable": {"1"}})
+	if rec.Code != http.StatusSeeOther || !strings.Contains(f.written(shares.DefaultSMBConf), "path = /srv/media") {
+		t.Fatalf("non-ZFS share: %d %s", rec.Code, rec.Body.String())
+	}
+	postForm(srv, "/shares/smb/delete", url.Values{"name": {"media"}})
 	// a user still referenced by a share cannot be deleted
 	rec = postForm(srv, "/shares/users/delete", url.Values{"name": {"alice"}})
 	if rec.Code != 200 || !strings.Contains(rec.Body.String(), "still allowed on share private") || f.has("smbpasswd -x") {
@@ -192,11 +202,17 @@ func TestSharesNFSFlow(t *testing.T) {
 		{"path": {"/tank/data2"}, "clients": {""}, "squash": {"root"}},            // no clients
 		{"path": {"/tank/data2"}, "clients": {"10.0.0.0/33"}, "squash": {"root"}}, // bad cidr
 		{"path": {"/tank/data2"}, "clients": {"*"}, "squash": {"weird"}},          // bad squash
+		{"path": {"/etc"}, "clients": {"*"}, "squash": {"root"}},                  // system dir
 	} {
 		if rec := postForm(srv, "/shares/nfs/save", form); rec.Code != 200 || !strings.Contains(rec.Body.String(), "Not saved") {
 			t.Errorf("form %v accepted", form)
 		}
 	}
+	if rec := postForm(srv, "/shares/nfs/save", url.Values{"path": {"/srv/media"}, "clients": {"*"}, "squash": {"root"}}); rec.Code != http.StatusSeeOther ||
+		!strings.Contains(f.written(shares.DefaultExports), `"/srv/media" *(`) {
+		t.Fatalf("non-ZFS export: %d %s", rec.Code, rec.Body.String())
+	}
+	postForm(srv, "/shares/nfs/delete", url.Values{"path": {"/srv/media"}})
 	body := get(srv, "/shares").Body.String()
 	if !strings.Contains(body, "192.168.101.0/24, pc.lan") || !strings.Contains(body, ":/tank/data") {
 		t.Errorf("export not listed")

internal/web/templates/shares.html

@@ -47,7 +47,7 @@
       <input type="hidden" name="orig" value="{{.Form.Orig}}">
       <div class="form-grid">
         <label>Share name <input name="name" required value="{{.Form.Name}}" placeholder="documents"></label>
-        <label>Path <input name="path" required list="mountpoints" value="{{.Form.Path}}" placeholder="/nas_pool_1_8_gb/documents"></label>
+        <label>Path <input name="path" required list="mountpoints" value="{{.Form.Path}}" placeholder="/nas_pool_1_8_gb/documents or /mnt/usb"></label>
         <label>Comment <input name="comment" value="{{.Form.Comment}}"></label>
         <label class="check"><input type="checkbox" name="read_only" value="1" {{if .Form.ReadOnly}}checked{{end}}> Read-only</label>
         <label class="check"><input type="checkbox" name="guest" value="1" {{if .Form.Guest}}checked{{end}}> Guest access (anyone on the LAN, no password)</label>
@@ -58,6 +58,7 @@
           <span class="checks">{{range .Users}}<label class="check-item"><input type="checkbox" name="users" value="{{.}}" {{if contains $.Data.Form.Users .}}checked{{end}}> {{.}}</label>{{else}}<span class="muted">no SMB users yet — add one below</span>{{end}}</span>
         </div>
       </div>
+      <p class="small muted">Path: any folder on the NAS — a ZFS dataset, a USB disk under /mnt or /media, /srv… System directories (/etc, /usr, /var…) are refused.</p>
       <p class="small muted">Files are read and written as <b>{{.Owner}}</b> regardless of the SMB user, so containers and shares see the same ownership.</p>
       <button type="submit">{{if .Form.New}}Create share{{else}}Save share{{end}}</button>
       {{if not .Form.New}}<a href="/shares" class="small">cancel</a>{{end}}
@@ -118,7 +119,7 @@
     <form method="post" action="/shares/nfs/save" class="ds-form">
       <input type="hidden" name="orig" value="{{.NForm.Orig}}">
       <div class="form-grid">
-        <label>Path <input name="path" required list="mountpoints" value="{{.NForm.Path}}" placeholder="/nas_pool_1_8_gb/documents"></label>
+        <label>Path <input name="path" required list="mountpoints" value="{{.NForm.Path}}" placeholder="/nas_pool_1_8_gb/documents or /mnt/usb"></label>
         <label>Clients <input name="clients" required value="{{.NForm.Clients}}" placeholder="192.168.101.0/24, pc.lan, *"></label>
         <label>Squash
           <select name="squash">
@@ -130,7 +131,7 @@
         <label class="check"><input type="checkbox" name="read_only" value="1" {{if .NForm.ReadOnly}}checked{{end}}> Read-only</label>
         <label class="check"><input type="checkbox" name="async" value="1" {{if .NForm.Async}}checked{{end}}> async writes (faster, less safe on power loss)</label>
       </div>
-      <p class="small muted">Nested datasets under the path are exported too (crossmnt). Clients: host names, IPs, networks like 192.168.101.0/24, or * for everyone.</p>
+      <p class="small muted">Filesystems mounted below the path (nested datasets, disks) are exported too (crossmnt). Clients: host names, IPs, networks like 192.168.101.0/24, or * for everyone.</p>
       <button type="submit">{{if .NForm.New}}Create export{{else}}Save export{{end}}</button>
       {{if not .NForm.New}}<a href="/shares" class="small">cancel</a>{{end}}
     </form>

internal/web/web_test.go

@@ -89,7 +89,18 @@ func newTestServer(t *testing.T) (*Server, *sched.Scheduler, *store.Store) {
 		t.Fatal(err)
 	}
 	srv := New(cfg, st, ring, sc, shs)
-	srv.dirExists = func(p string) bool { return strings.HasPrefix(p, "/tank") || strings.HasPrefix(p, "/tmp_pool") }
+	srv.dirExists = func(p string) bool {
+		return strings.HasPrefix(p, "/tank") || strings.HasPrefix(p, "/tmp_pool") || strings.HasPrefix(p, "/srv")
+	}
+	srv.realPath = func(p string) (string, error) {
+		if p == "/srv/evil" { // symlink into a system directory
+			return "/etc", nil
+		}
+		return p, nil
+	}
+	srv.readMounts = func() string {
+		return "proc /proc proc rw 0 0\n/dev/sda2 / ext4 rw 0 0\ntank/data /tank/data zfs rw 0 0\n/dev/sdc1 /mnt/usb ext4 rw 0 0\n"
+	}
 	return srv, sc, st
 }