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Merged
GG-O-BP merged 1 commit into from
Sep 3, 2026
Merged

Validate MPK entry paths before extraction writes #3

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25 changes: 20 additions & 5 deletions src/mxpak/mpk/zip.gleam
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Original file line number Diff line number Diff line change
Expand Up @@ -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.
Expand All @@ -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))
})
}

Expand All @@ -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(
Expand Down
109 changes: 108 additions & 1 deletion test/mpk_test.gleam
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Original file line number Diff line number Diff line change
Expand Up @@ -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)
Expand Down Expand Up @@ -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.
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