feat(sidecar): enforce per-user BasePath on all filesystem mutations

Folder create/rename/delete/move, photo move, heap convert, and file
rename now reject paths outside the caller's BasePath (403). Sources
resolved via PhotoPrism UIDs are re-checked in movePhotoFiles. The
USER_BASEPATHS reconciler also sets upload_path so client-app uploads
land inside the user's subtree.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

sidecar/auth.go

@@ -2,6 +2,8 @@ package main
 
 import (
 	"net/http"
+	"path/filepath"
+	"strings"
 
 	"github.com/gin-gonic/gin"
 )
@@ -85,3 +87,35 @@ func ctxBasePath(c *gin.Context) string {
 	}
 	return s
 }
+
+// userScopeRoot returns the absolute directory the session may mutate:
+// ORIGINALS_ROOT/<BasePath> for scoped users, the whole originals root for
+// admins (empty BasePath). Lexical join only — callers compare it against
+// paths built the same way from cfg.OriginalsRoot.
+func userScopeRoot(c *gin.Context, cfg *Config) string {
+	base := strings.Trim(ctxBasePath(c), "/")
+	if base == "" {
+		return cfg.OriginalsRoot
+	}
+	return filepath.Join(cfg.OriginalsRoot, base)
+}
+
+// requireUserScope guards an already-root-resolved absolute path against
+// the caller's BasePath. PhotoPrism scopes what a session can *see* by
+// BasePath, but the sidecar's filesystem endpoints accept raw paths, so
+// every mutation must re-check that boundary here. `strict` additionally
+// rejects the scope root itself — renaming/deleting/moving the user's own
+// base folder would detach their library from auth_users.base_path.
+// Writes the 403 response and returns false when out of bounds.
+func requireUserScope(c *gin.Context, cfg *Config, abs string, strict bool) bool {
+	scope := userScopeRoot(c, cfg)
+	if !sameOrUnder(abs, scope) {
+		c.JSON(http.StatusForbidden, gin.H{"error": "path outside your library"})
+		return false
+	}
+	if strict && abs == scope {
+		c.JSON(http.StatusForbidden, gin.H{"error": "cannot modify your library root"})
+		return false
+	}
+	return true
+}

sidecar/auth_test.go

@@ -0,0 +1,50 @@
+package main
+
+import (
+	"net/http/httptest"
+	"path/filepath"
+	"testing"
+
+	"github.com/gin-gonic/gin"
+)
+
+func scopeCtx(basePath string) *gin.Context {
+	gin.SetMode(gin.TestMode)
+	c, _ := gin.CreateTestContext(httptest.NewRecorder())
+	c.Set("basePath", basePath)
+	return c
+}
+
+func TestRequireUserScope(t *testing.T) {
+	cfg := &Config{OriginalsRoot: filepath.FromSlash("/originals")}
+	abs := func(rel string) string { return filepath.Join(cfg.OriginalsRoot, filepath.FromSlash(rel)) }
+
+	cases := []struct {
+		name     string
+		basePath string
+		path     string
+		strict   bool
+		want     bool
+	}{
+		{"admin sees root", "", cfg.OriginalsRoot, false, true},
+		{"admin anywhere", "", abs("bob/x"), false, true},
+		{"admin strict rejects root", "", cfg.OriginalsRoot, true, false},
+		{"scoped inside own tree", "alice", abs("alice/2024"), false, true},
+		{"scoped own root non-strict", "alice", abs("alice"), false, true},
+		{"scoped own root strict", "alice", abs("alice"), true, false},
+		{"scoped other user", "alice", abs("bob/2024"), false, false},
+		{"scoped sibling prefix", "alice", abs("alice2/2024"), false, false},
+		{"scoped originals root", "alice", cfg.OriginalsRoot, false, false},
+		{"nested base path", "family/alice", abs("family/alice/x"), false, true},
+		{"nested base path parent", "family/alice", abs("family"), false, false},
+	}
+	for _, tc := range cases {
+		t.Run(tc.name, func(t *testing.T) {
+			c := scopeCtx(tc.basePath)
+			if got := requireUserScope(c, cfg, tc.path, tc.strict); got != tc.want {
+				t.Errorf("requireUserScope(base=%q, path=%q, strict=%v) = %v, want %v",
+					tc.basePath, tc.path, tc.strict, got, tc.want)
+			}
+		})
+	}
+}

sidecar/handlers_folders.go

@@ -47,6 +47,9 @@ func handleFolderCreate(cfg *Config, pp *ppClient) gin.HandlerFunc {
 			c.JSON(http.StatusBadRequest, gin.H{"error": "invalid path"})
 			return
 		}
+		if !requireUserScope(c, cfg, abs, true) {
+			return
+		}
 		if _, err := os.Stat(abs); err == nil {
 			c.JSON(http.StatusConflict, gin.H{"error": "already exists"})
 			return
@@ -92,6 +95,9 @@ func handleFolderRename(cfg *Config, pp *ppClient) gin.HandlerFunc {
 			c.JSON(http.StatusBadRequest, gin.H{"error": "invalid path"})
 			return
 		}
+		if !requireUserScope(c, cfg, oldAbs, true) {
+			return
+		}
 		st, err := os.Stat(oldAbs)
 		if err != nil || !st.IsDir() {
 			c.JSON(http.StatusBadRequest, gin.H{"error": "not a directory"})
@@ -142,6 +148,9 @@ func handleFolderDelete(cfg *Config, pp *ppClient) gin.HandlerFunc {
 			c.JSON(http.StatusBadRequest, gin.H{"error": "refuse to delete root"})
 			return
 		}
+		if !requireUserScope(c, cfg, abs, true) {
+			return
+		}
 		st, err := os.Stat(abs)
 		if err != nil || !st.IsDir() {
 			c.JSON(http.StatusBadRequest, gin.H{"error": "not a directory"})

sidecar/handlers_heap.go

@@ -90,6 +90,9 @@ func handleHeapConvert(cfg *Config, pp *ppClient) gin.HandlerFunc {
 			c.JSON(http.StatusBadRequest, gin.H{"error": "invalid targetFolder"})
 			return
 		}
+		if !requireUserScope(c, cfg, targetAbs, false) {
+			return
+		}
 		// Pull the heap's membership via the q=album:UID query (count=1000
 		// covers every realistic heap). We only need the UID list here — the
 		// search's Files array is trimmed and drops videos, so we re-resolve
@@ -124,7 +127,7 @@ func handleHeapConvert(cfg *Config, pp *ppClient) gin.HandlerFunc {
 			return
 		}
 
-		moved, copied, errs, err := movePhotoFiles(cfg, pp, token, photos, targetAbs, subfolder, mode)
+		moved, copied, errs, err := movePhotoFiles(cfg, pp, token, photos, targetAbs, subfolder, mode, userScopeRoot(c, cfg))
 		if err != nil {
 			c.JSON(http.StatusInternalServerError, gin.H{"error": err.Error()})
 			return
@@ -167,7 +170,10 @@ func handleHeapConvert(cfg *Config, pp *ppClient) gin.HandlerFunc {
 // and handlePhotosMove (UID-list scoped); both resolve `photos` differently
 // but move them identically. Returns per-photo errors in `errs`; the returned
 // top-level error is only for a fatal precondition (subfolder mkdir failed).
-func movePhotoFiles(cfg *Config, pp *ppClient, token string, photos []heapPhoto, targetAbs, subfolder, mode string) (moved, copied int, errs []heapErr, err error) {
+// `scopeAbs` is the caller's userScopeRoot — source files outside it fail
+// per-photo, so a UID that resolves outside the user's BasePath (however
+// PhotoPrism came to return it) can't be used to pull files across users.
+func movePhotoFiles(cfg *Config, pp *ppClient, token string, photos []heapPhoto, targetAbs, subfolder, mode, scopeAbs string) (moved, copied int, errs []heapErr, err error) {
 	destAbs := targetAbs
 	if subfolder != "" {
 		destAbs = filepath.Join(targetAbs, subfolder)
@@ -234,8 +240,8 @@ func movePhotoFiles(cfg *Config, pp *ppClient, token string, photos []heapPhoto,
 		for _, f := range group {
 			srcRel := f.Name
 			srcAbs := filepath.Join(cfg.OriginalsRoot, srcRel)
-			if !sameOrUnder(srcAbs, cfg.OriginalsRoot) {
-				failure = "path escapes originals"
+			if !sameOrUnder(srcAbs, scopeAbs) {
+				failure = "path outside your library"
 				break
 			}
 			st, statErr := os.Stat(srcAbs)

sidecar/handlers_move.go

@@ -56,6 +56,9 @@ func handlePhotosMove(cfg *Config, pp *ppClient) gin.HandlerFunc {
 			c.JSON(http.StatusBadRequest, gin.H{"error": "invalid targetFolder"})
 			return
 		}
+		if !requireUserScope(c, cfg, targetAbs, false) {
+			return
+		}
 
 		// Resolve each photo's FULL file list via the single-photo endpoint
 		// rather than the /photos search (see resolvePhotosFull) — the search
@@ -67,7 +70,7 @@ func handlePhotosMove(cfg *Config, pp *ppClient) gin.HandlerFunc {
 			return
 		}
 
-		moved, copied, errs, err := movePhotoFiles(cfg, pp, token, photos, targetAbs, subfolder, mode)
+		moved, copied, errs, err := movePhotoFiles(cfg, pp, token, photos, targetAbs, subfolder, mode, userScopeRoot(c, cfg))
 		if err != nil {
 			c.JSON(http.StatusInternalServerError, gin.H{"error": err.Error()})
 			return
@@ -148,6 +151,9 @@ func handleFolderMove(cfg *Config, pp *ppClient) gin.HandlerFunc {
 			c.JSON(http.StatusBadRequest, gin.H{"error": "invalid path"})
 			return
 		}
+		if !requireUserScope(c, cfg, oldAbs, true) {
+			return
+		}
 		st, err := os.Stat(oldAbs)
 		if err != nil || !st.IsDir() {
 			c.JSON(http.StatusBadRequest, gin.H{"error": "not a directory"})
@@ -158,6 +164,9 @@ func handleFolderMove(cfg *Config, pp *ppClient) gin.HandlerFunc {
 			c.JSON(http.StatusBadRequest, gin.H{"error": "invalid targetParent"})
 			return
 		}
+		if !requireUserScope(c, cfg, targetParentAbs, false) {
+			return
+		}
 		// Can't move a folder into itself or one of its own descendants.
 		if sameOrUnder(targetParentAbs, oldAbs) {
 			c.JSON(http.StatusBadRequest, gin.H{"error": "cannot move a folder into itself"})

sidecar/handlers_rename.go

@@ -97,6 +97,9 @@ func handleRename(cfg *Config, pp *ppClient) gin.HandlerFunc {
 			c.JSON(http.StatusBadRequest, gin.H{"error": "path escapes originals root"})
 			return
 		}
+		if !requireUserScope(c, cfg, oldAbs, false) {
+			return
+		}
 		st, err := os.Stat(oldAbs)
 		if err != nil || !st.Mode().IsRegular() {
 			c.JSON(http.StatusNotFound, gin.H{"error": "file missing on disk"})

sidecar/users.go

@@ -86,12 +86,15 @@ func reconcileUserBasepaths(ppDSN, originalsRoot string, mapping map[string]stri
 			// ACL kicks in even if the directory is created later.
 		}
 
+		// upload_path rides along with base_path so anything a client app
+		// uploads (WebDAV sync apps, PhotoPrism's own UI) lands inside the
+		// user's library subtree instead of the shared originals root.
 		res := db.Exec(`UPDATE auth_users
-			SET base_path = ?
+			SET base_path = ?, upload_path = ?
 			WHERE user_name = ?
-			  AND COALESCE(base_path, '') <> ?
+			  AND (COALESCE(base_path, '') <> ? OR COALESCE(upload_path, '') <> ?)
 			  AND deleted_at IS NULL`,
-			path, username, path)
+			path, path, username, path, path)
 		if res.Error != nil {
 			slog.Error("user-basepath: update failed", "user", username, "err", res.Error)
 			continue