From a616126210b2adbb1b1e38bbc8b728dba51311af Mon Sep 17 00:00:00 2001
From: GGOBP <GGOBP@protonmail.ch>
Date: Thu, 3 Sep 2026 09:42:01 +0900
Subject: [PATCH] Validate MPK entry paths before extraction writes

Fixes glendix-labs/mendraw#3
---
 src/mxpak/mpk/zip.gleam |  25 +++++++--
 test/mpk_test.gleam     | 109 +++++++++++++++++++++++++++++++++++++++-
 2 files changed, 128 insertions(+), 6 deletions(-)

diff --git a/src/mxpak/mpk/zip.gleam b/src/mxpak/mpk/zip.gleam
index 9d9c3f9..155384e 100644
--- a/src/mxpak/mpk/zip.gleam
+++ b/src/mxpak/mpk/zip.gleam
@@ -3,6 +3,7 @@
 
 import gleam/list
 import gleam/result
+import gleam/string
 import mxpak/error
 
 /// A typed `ZipEntry` value used by the zip capability.
@@ -15,11 +16,11 @@ pub type ZipEntry {
 pub fn extract(
   zip_binary zip_binary: BitArray,
 ) -> Result(List(ZipEntry), error.Error) {
-  unzip_to_memory(zip_binary)
-  |> result.map(fn(raw_entries) {
-    list.map(raw_entries, fn(entry) {
-      ZipEntry(name: entry.0, content: entry.1)
-    })
+  use raw_entries <- result.try(unzip_to_memory(zip_binary))
+  raw_entries
+  |> list.try_map(fn(entry) {
+    use _ <- result.try(validate_entry_name(entry.0))
+    Ok(ZipEntry(name: entry.0, content: entry.1))
   })
 }
 
@@ -42,6 +43,20 @@ pub fn list_entries(
   list.map(entries, fn(e) { e.name })
 }
 
+/// Rejects archive paths that could escape an extraction root.
+fn validate_entry_name(name name: String) -> Result(Nil, error.Error) {
+  let segments = string.split(name, "/")
+  case
+    name == ""
+    || string.starts_with(name, "/")
+    || string.contains(name, "\\")
+    || list.contains(segments, "..")
+  {
+    True -> Error(error.download("ZIP 엔트리 경로가 안전하지 않습니다: " <> name))
+    False -> Ok(Nil)
+  }
+}
+
 // -- Erlang FFI --
 @external(erlang, "mxpak_zip_ffi", "unzip_to_memory")
 fn unzip_to_memory(
diff --git a/test/mpk_test.gleam b/test/mpk_test.gleam
index fcc62ef..70f7680 100644
--- a/test/mpk_test.gleam
+++ b/test/mpk_test.gleam
@@ -29,7 +29,50 @@ pub fn zip_extract_file_from_invalid_test() -> Nil {
   Nil
 }
 
-/// Verifies parse widget name behavior.
+/// Verifies OTP sanitizes parent-directory entries to in-root names.
+pub fn zip_extract_normalizes_parent_directory_entries_test() -> Nil {
+  let entries = zip.extract(parent_directory_zip_binary()) |> should.be_ok
+  entries
+  |> list.first
+  |> should.equal(
+    Ok(zip.ZipEntry(name: "evil.txt", content: <<"escaped":utf8>>)),
+  )
+  Nil
+}
+
+/// Verifies backslash archive entries are rejected before extraction.
+pub fn zip_extract_rejects_backslash_entries_test() -> Nil {
+  let error_value = zip.extract(backslash_zip_binary()) |> should.be_error
+  error_value
+  |> error.message
+  |> string.contains("..\\evil.txt")
+  |> should.be_true
+  Nil
+}
+
+/// Verifies nested archive entries remain usable.
+pub fn zip_extract_allows_nested_entries_test() -> Nil {
+  let entries = zip.extract(valid_zip_binary()) |> should.be_ok
+  entries
+  |> list.first
+  |> should.equal(
+    Ok(
+      zip.ZipEntry(name: "com/example/Widget.mjs", content: <<
+        "export default 1\n":utf8,
+      >>),
+    ),
+  )
+  Nil
+}
+
+/// Verifies truncated archives fail without crashing.
+pub fn zip_extract_truncated_archive_test() -> Nil {
+  zip.extract(truncated_zip_binary())
+  |> should.be_error
+  Nil
+}
+
+// A stored ZIP archive containing one ../evil.txt entry.
 pub fn parse_widget_name_test() -> Nil {
   let xml = "<widget><name>DataGrid</name></widget>"
   xml.parse_widget_name(xml)
@@ -191,3 +234,67 @@ pub fn metadata_classic_roundtrip_test() -> Nil {
   |> should.be_ok
   Nil
 }
+
+fn parent_directory_zip_binary() -> BitArray {
+  <<
+    0x50, 0x4b, 0x03, 0x04, 0x14, 0x00, 0x00, 0x00, 0x00, 0x00, 0xf4, 0x4c, 0x23,
+    0x5d, 0x5b, 0x0c, 0xf8, 0x92, 0x07, 0x00, 0x00, 0x00, 0x07, 0x00, 0x00, 0x00,
+    0x0b, 0x00, 0x00, 0x00, 0x2e, 0x2e, 0x2f, 0x65, 0x76, 0x69, 0x6c, 0x2e, 0x74,
+    0x78, 0x74, 0x65, 0x73, 0x63, 0x61, 0x70, 0x65, 0x64, 0x50, 0x4b, 0x01, 0x02,
+    0x14, 0x03, 0x14, 0x00, 0x00, 0x00, 0x00, 0x00, 0xf4, 0x4c, 0x23, 0x5d, 0x5b,
+    0x0c, 0xf8, 0x92, 0x07, 0x00, 0x00, 0x00, 0x07, 0x00, 0x00, 0x00, 0x0b, 0x00,
+    0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x80, 0x01, 0x00,
+    0x00, 0x00, 0x00, 0x2e, 0x2e, 0x2f, 0x65, 0x76, 0x69, 0x6c, 0x2e, 0x74, 0x78,
+    0x74, 0x50, 0x4b, 0x05, 0x06, 0x00, 0x00, 0x00, 0x00, 0x01, 0x00, 0x01, 0x00,
+    0x39, 0x00, 0x00, 0x00, 0x30, 0x00, 0x00, 0x00, 0x00, 0x00,
+  >>
+}
+
+// A stored ZIP archive containing one ..\evil.txt entry.
+fn backslash_zip_binary() -> BitArray {
+  <<
+    0x50, 0x4b, 0x03, 0x04, 0x14, 0x00, 0x00, 0x00, 0x00, 0x00, 0x2a, 0x4d, 0x23,
+    0x5d, 0x5b, 0x0c, 0xf8, 0x92, 0x07, 0x00, 0x00, 0x00, 0x07, 0x00, 0x00, 0x00,
+    0x0b, 0x00, 0x00, 0x00, 0x2e, 0x2e, 0x5c, 0x65, 0x76, 0x69, 0x6c, 0x2e, 0x74,
+    0x78, 0x74, 0x65, 0x73, 0x63, 0x61, 0x70, 0x65, 0x64, 0x50, 0x4b, 0x01, 0x02,
+    0x14, 0x03, 0x14, 0x00, 0x00, 0x00, 0x00, 0x00, 0x2a, 0x4d, 0x23, 0x5d, 0x5b,
+    0x0c, 0xf8, 0x92, 0x07, 0x00, 0x00, 0x00, 0x07, 0x00, 0x00, 0x00, 0x0b, 0x00,
+    0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x80, 0x01, 0x00,
+    0x00, 0x00, 0x00, 0x2e, 0x2e, 0x5c, 0x65, 0x76, 0x69, 0x6c, 0x2e, 0x74, 0x78,
+    0x74, 0x50, 0x4b, 0x05, 0x06, 0x00, 0x00, 0x00, 0x00, 0x01, 0x00, 0x01, 0x00,
+    0x39, 0x00, 0x00, 0x00, 0x30, 0x00, 0x00, 0x00, 0x00, 0x00,
+  >>
+}
+
+// A stored ZIP archive containing one nested widget entry.
+fn valid_zip_binary() -> BitArray {
+  <<
+    0x50, 0x4b, 0x03, 0x04, 0x14, 0x00, 0x00, 0x00, 0x00, 0x00, 0xf4, 0x4c, 0x23,
+    0x5d, 0xbc, 0x6c, 0xb4, 0x4d, 0x11, 0x00, 0x00, 0x00, 0x11, 0x00, 0x00, 0x00,
+    0x16, 0x00, 0x00, 0x00, 0x63, 0x6f, 0x6d, 0x2f, 0x65, 0x78, 0x61, 0x6d, 0x70,
+    0x6c, 0x65, 0x2f, 0x57, 0x69, 0x64, 0x67, 0x65, 0x74, 0x2e, 0x6d, 0x6a, 0x73,
+    0x65, 0x78, 0x70, 0x6f, 0x72, 0x74, 0x20, 0x64, 0x65, 0x66, 0x61, 0x75, 0x6c,
+    0x74, 0x20, 0x31, 0x0a, 0x50, 0x4b, 0x01, 0x02, 0x14, 0x03, 0x14, 0x00, 0x00,
+    0x00, 0x00, 0x00, 0xf4, 0x4c, 0x23, 0x5d, 0xbc, 0x6c, 0xb4, 0x4d, 0x11, 0x00,
+    0x00, 0x00, 0x11, 0x00, 0x00, 0x00, 0x16, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+    0x00, 0x00, 0x00, 0x00, 0x00, 0x80, 0x01, 0x00, 0x00, 0x00, 0x00, 0x63, 0x6f,
+    0x6d, 0x2f, 0x65, 0x78, 0x61, 0x6d, 0x70, 0x6c, 0x65, 0x2f, 0x57, 0x69, 0x64,
+    0x67, 0x65, 0x74, 0x2e, 0x6d, 0x6a, 0x73, 0x50, 0x4b, 0x05, 0x06, 0x00, 0x00,
+    0x00, 0x00, 0x01, 0x00, 0x01, 0x00, 0x44, 0x00, 0x00, 0x00, 0x45, 0x00, 0x00,
+    0x00, 0x00, 0x00,
+  >>
+}
+
+fn truncated_zip_binary() -> BitArray {
+  <<
+    0x50, 0x4b, 0x03, 0x04, 0x14, 0x00, 0x00, 0x00, 0x00, 0x00, 0xf4, 0x4c, 0x23,
+    0x5d, 0xbc, 0x6c, 0xb4, 0x4d, 0x11, 0x00, 0x00, 0x00, 0x11, 0x00, 0x00, 0x00,
+    0x16, 0x00, 0x00, 0x00, 0x63, 0x6f, 0x6d, 0x2f, 0x65, 0x78, 0x61, 0x6d, 0x70,
+    0x6c, 0x65, 0x2f, 0x57, 0x69, 0x64, 0x67, 0x65, 0x74, 0x2e, 0x6d, 0x6a, 0x73,
+    0x65, 0x78, 0x70, 0x6f, 0x72, 0x74, 0x20, 0x64, 0x65, 0x66, 0x61, 0x75, 0x6c,
+    0x74, 0x20, 0x31, 0x0a, 0x50, 0x4b, 0x01, 0x02, 0x14, 0x03, 0x14, 0x00, 0x00,
+    0x00, 0x00, 0x00, 0xf4, 0x4c, 0x23, 0x5d, 0xbc, 0x6c, 0xb4, 0x4d, 0x11, 0x00,
+    0x00, 0x00,
+  >>
+}
+/// Verifies parse widget name behavior.