fix(reader): allow KOReader downloads from filesystem root

Preserve the filesystem root during destination normalization so valid downloads reach the transfer callback. Report local preflight failures accurately and cover root publishing and traversal rejection.

Closes #1177

koreader-plugin/bookorbit.koplugin/bookorbit_catalog.lua

@@ -832,7 +832,10 @@ function BookOrbitCatalog:showServerError(err)
 end
 
 function BookOrbitCatalog:errorText(err)
-    if isAuthError(err) then
+    local transfer_error = CatalogUtil.transferErrorText(err)
+    if transfer_error then
+        return transfer_error
+    elseif isAuthError(err) then
         return _("BookOrbit login failed. Check your KOReader credentials.")
     elseif type(err) == "number" then
         return T(_("BookOrbit server error (%1)."), err)

koreader-plugin/bookorbit.koplugin/bookorbit_catalog_util.lua

@@ -386,6 +386,15 @@ function CatalogUtil.safeFilenameBase(detail)
     return base
 end
 
+function CatalogUtil.transferErrorText(err)
+    if err == "unsafe_destination" then
+        return _("The download destination is outside the selected folder.")
+    elseif err == "temp_dir_failed" then
+        return _("Could not create a temporary download folder in the selected folder.")
+    end
+    return nil
+end
+
 function CatalogUtil.coverLabel(book)
     local lines = {}
     local title = book and book.title or _("Untitled")

koreader-plugin/bookorbit.koplugin/bookorbit_download_transfer.lua

@@ -31,11 +31,14 @@ Transfer.TEMP_DIR_NAME = TEMP_DIR_NAME
 Transfer.POLL_INTERVAL = POLL_INTERVAL
 
 local function normalize(path)
-    return tostring(path or ""):gsub("\\", "/"):gsub("/+", "/"):gsub("/$", "")
+    local normalized = tostring(path or ""):gsub("\\", "/"):gsub("/+", "/")
+    if normalized == "/" then return normalized end
+    return normalized:gsub("/$", "")
 end
 
 function Transfer.tempDir(root)
-    return normalize(root) .. "/" .. TEMP_DIR_NAME
+    local normalized_root = normalize(root)
+    return (normalized_root ~= "/" and normalized_root or "") .. "/" .. TEMP_DIR_NAME
 end
 
 function Transfer.ensureTempDir(root)
@@ -52,7 +55,11 @@ function Transfer.isInsideRoot(root, path)
     local normalized_root = normalize(root)
     local normalized_path = normalize(path)
     if normalized_root == "" or normalized_path == "" then return false end
-    if normalized_path:sub(1, #normalized_root + 1) ~= normalized_root .. "/" then return false end
+    if normalized_root == "/" then
+        if normalized_path == "/" or normalized_path:sub(1, 1) ~= "/" then return false end
+    elseif normalized_path:sub(1, #normalized_root + 1) ~= normalized_root .. "/" then
+        return false
+    end
     for segment in normalized_path:gmatch("[^/]+") do
         if segment == ".." then return false end
     end

koreader-plugin/bookorbit.koplugin/main.lua

@@ -48,7 +48,7 @@ local BookOrbitProgressSync = require("bookorbit_progress_sync")
 local BookOrbitSweep = require("bookorbit_sweep")
 local BookOrbitUpdater = require("bookorbit_updater")
 
-local PLUGIN_VERSION = "1.5.0"
+local PLUGIN_VERSION = "1.5.1"
 
 local SYNC_STRATEGY = {
     PROMPT = 1,

koreader-plugin/spec/bookorbit_catalog_transfer_error_test.lua

@@ -0,0 +1,42 @@
+local function identity(value)
+    return value
+end
+
+package.loaded["gettext"] = identity
+package.loaded["document/documentregistry"] = {
+    hasProvider = function()
+        return true
+    end,
+}
+package.loaded["util"] = {
+    fixUtf8 = identity,
+}
+package.loaded["ffi/util"] = {
+    template = function(value)
+        return value
+    end,
+}
+
+package.path = "koreader-plugin/bookorbit.koplugin/?.lua;" .. package.path
+
+local CatalogUtil = require("bookorbit_catalog_util")
+
+local function assertEqual(actual, expected, label)
+    if actual ~= expected then
+        error(string.format("%s: expected %s, got %s", label, tostring(expected), tostring(actual)))
+    end
+end
+
+assertEqual(
+    CatalogUtil.transferErrorText("unsafe_destination"),
+    "The download destination is outside the selected folder.",
+    "unsafe destinations are reported as local path failures"
+)
+assertEqual(
+    CatalogUtil.transferErrorText("temp_dir_failed"),
+    "Could not create a temporary download folder in the selected folder.",
+    "temporary directory failures are reported as local filesystem failures"
+)
+assertEqual(CatalogUtil.transferErrorText("network_error"), nil, "network errors keep the existing connection message")
+
+print("bookorbit_catalog_transfer_error_test.lua: ok")

koreader-plugin/spec/bookorbit_download_transfer_test.lua

@@ -10,7 +10,10 @@ package.loaded["ui/uimanager"] = {
     end,
 }
 
-local directories = { ["/downloads/.bookorbit-tmp"] = true }
+local directories = {
+    ["/.bookorbit-tmp"] = true,
+    ["/downloads/.bookorbit-tmp"] = true,
+}
 local files = {}
 local now = 1000
 package.loaded["libs/libkoreader-lfs"] = {
@@ -66,10 +69,16 @@ end
 -- Destination containment is checked before anything is written and again
 -- before the publishing rename.
 assertEqual(Transfer.isInsideRoot("/downloads", "/downloads/Books/a.epub"), true, "a path under the root is authorized")
+assertEqual(Transfer.isInsideRoot("/downloads", "/downloads/The Shards.epub"), true,
+    "a file directly under the download root is authorized")
 assertEqual(Transfer.isInsideRoot("/downloads", "/elsewhere/a.epub"), false, "a path outside the root is rejected")
 assertEqual(Transfer.isInsideRoot("/downloads", "/downloads/../etc/passwd"), false, "traversal is rejected")
 assertEqual(Transfer.isInsideRoot("/downloads", "/downloads"), false, "the root itself is not a destination")
 assertEqual(Transfer.tempDir("/downloads"), "/downloads/.bookorbit-tmp", "temporaries live under the destination root")
+assertEqual(Transfer.isInsideRoot("/", "/The Shards.epub"), true, "the filesystem root supports a direct book destination")
+assertEqual(Transfer.isInsideRoot("/", "/Standalone/The Shards.epub"), true, "the filesystem root supports nested destinations")
+assertEqual(Transfer.isInsideRoot("/", "/../etc/passwd"), false, "the filesystem root still rejects traversal")
+assertEqual(Transfer.tempDir("/"), "/.bookorbit-tmp", "the filesystem root gets one temporary directory separator")
 
 -- Leftovers from a killed run are removed, and the sweep stays bounded.
 files["/downloads/.bookorbit-tmp/bo_1_1.part"] = { size = 10, modified = 1 }
@@ -141,6 +150,25 @@ runScheduled()
 assertEqual(#scheduled, 0, "a poll that fires after completion does not reschedule itself")
 assertEqual(#observed, 1, "no progress is reported once the transfer returned")
 
+-- A user-selected filesystem root used to normalize to an empty string and
+-- reject the destination before perform could start the HTTP request.
+local root_request_started = false
+local root_completed = Transfer.run{
+    root = "/",
+    destination = "/The Shards.epub",
+    generation = 5,
+    expected_bytes = 2089926,
+    is_current = function() return true end,
+    perform = function(download_opts)
+        root_request_started = true
+        files[download_opts.temp_path] = { size = 2089926, modified = now }
+        return { temp_path = download_opts.temp_path, bytes = 2089926 }
+    end,
+}
+assertEqual(root_request_started, true, "the reported book reaches the HTTP transfer callback")
+assertEqual(root_completed, true, "the reported book publishes under a filesystem-root download folder")
+assertEqual(files["/The Shards.epub"] ~= nil, true, "the reported book is published at the requested destination")
+
 -- A cancelled generation discards a late child result instead of publishing it.
 renames = {}
 removed = {}