I focused on the in‐memory “file system” core (FileManager/File) and the command dispatch. Here are the issues I found:

1. Integer‐overflow / heap‐overflow in File::Write

   • File::Write computes
     uVar1 = offset + length;
     and if either
     old_capacity ≤ offset
     or
     old_capacity < uVar1
     it does a realloc(…, uVar1). If (offset+length) wraps around 64 bits into a small value, you will get a tiny allocation but then the subsequent
     memcpy(ptr+offset, data, length)
     writes well past the end of that buffer. An attacker who controls both offset and length via the “modify” command can craft an overflow of arbitrary size.

2. Path‐traversal in file/directory names

   • CreateFile/DeleteFile/OpenFile/ChangeDirectory all explicitly reject exactly “.”, “..” or “/” but do not reject names containing “/” elsewhere (e.g. “../secret” or “foo/bar”). In a real on-disk FS that could let you escape the current directory.

3. realloc()‐failure memory loss

   • When realloc() fails in File::Write the old buffer pointer is overwritten with NULL and the size is set to 0. You lose the handle on your old data (memory leak) and may cause future invalid reads.

4. No quota or per‐user limits

   • Aside from a 20‐entry “file descriptor” table, there is no limit on the total number or total size of files. An attacker could exhaust memory.

5. Lack of authentication/ACL

   • All operations are unprotected; once you have access to the command stream you can read, write, create and destroy arbitrarily.

The most critical of these is the integer‐overflow in Write, which leads to a controlled heap‐overflow.

Let’s walk through the vulnerable code in File::Write step‐by‐step and see exactly where and how a heap‐overflow can be triggered.

1. File::Write prototype

2. Key lines in the function (annotated):

3. Where is the overflow?
   The addition offset + len is done in 64-bit arithmetic, with no overflow check. If you choose

   then

   i.e. it wraps around to 0x10.

4. What happens next?

   • Initially capacity == 0 (brand-new file), so
     capacity <= offset is true (0 ≤ 0xFFF…F0).
   • The code calls realloc(data, total_needed) with a size of 0x10.
   • You now have a 16-byte buffer, but the code will memcpy len == 0x20 bytes into data + offset
     = (small_ptr + 0xFFF…F0). That pointer is way out of bounds of your 16-byte allocation, so you get an out-of-bounds write of 32 bytes at a completely arbitrary address (controlled by offset).

5. How to trigger in practice

   • Create a file (fd 0), e.g.
   • Invoke modify with a huge decimal offset so that strtoul() returns ULONG_MAX (0xFFFF…FFFF):
     (“18446744073709551615” is 2^64–1). Use, say, 32 “A”s for the data.
   • Internally offset = ULONG_MAX, len = 32, so offset+len wraps to 31, realloc(ptr,31) is called, then
     memcpy(ptr+0xFFF…FFF, “AAA…”, 32) corrupts 32 bytes at an attacker‐controlled address.

This is a classic integer-overflow → heap-overflow. Once you can write 32 bytes anywhere in memory, you can corrupt adjacent heap metadata, function pointers in the vtable, or the CommandManager structure to take over control flow.

Here’s a live Proof-of-Vulnerability demonstrating the integer-overflow → heap-overflow in File::Write. I’ll show:

1. A small shell‐script POC that talks to the service
2. A short GDB session breaking in File::Write to observe the wrapped size and out-of-bounds memcpy

—

1. POC script (poc.sh)

If you run chmod +x poc.sh && ./poc.sh under a debugger or with ASAN/Valgrind, you’ll see either:

• a crash inside memcpy (invalid pointer), or
• an out-of-bounds write reported by your memory‐sanitizer.

—
2) GDB walk‐through

Start under GDB and set a breakpoint on the memcpy call in File::Write:

Now feed it the same commands (you can paste them into GDB’s stdin):

GDB will break just as memcpy is about to execute. Examine the key registers:

Because

the copy lands miles beyond your heap chunk—a classic integer‐overflow‐to‐heap‐overflow.

Once you have an out‐of‐bounds write at an attacker‐controlled address, you can corrupt heap headers, vtables or CommandManager pointers and achieve arbitrary code execution.

Let’s zoom in on the directory‐name checks in FileManager – in particular, how “.”, “..” and “/” are rejected but any other slash‐containing string slips right through. On a real filesystem that would let you escape the “current directory” (e.g. create or open ../etc/passwd), so you must block all occurrences of “/”, not just the three literal strings.

—

1. CreateFile (very similar logic exists in CreateDirectory/DeleteFile/OpenFile):

2. What’s missing?
   We must also ban any slash in the middle of the filename, e.g.:

   c

   Without that check, a client can do:

   or

   and if FileManager ever turned around and handed that string to the OS’s open(2)/mkdir(2), it would climb out of its “sandbox.”

3. Demo of the problem

   • In the in‐memory model here you don’t actually call open(2), but if you did, your code would happily turn a “name” containing slashes into a direct path.
   • Even in this simulation, you can end up with file entries named “foo/bar” or “../passwd”. No code splits on ‘/’, so every slash is just part of the name, and there is no way to enforce a single directory level.

—
Fix: After your strlen(name) check, immediately do:

This guarantees that any attempt to escape the “current” in‐memory directory is caught.

Here’s a quick live Proof-of-Vulnerability for the path‐traversal (embedded “/” in filenames):

1. POC script (poc_path.sh):_

2. Expected output:

Notice that the second entry, “../escape”, contains “/” and was accepted. There is no check for any embedded slash—only the exact strings “.”, “..” or “/” are blocked.

In a real filesystem backend that passed these names directly to open(2) or mkdir(2), you’d immediately escape your “sandbox” directory and operate on ../escape (or even ../../etc/passwd).

Fix: after your strlen(name)<... check, add:

so no slash is ever allowed in a filename.

Below is an end-to-end demo showing how an attacker can use the “slash in filename” bug to read an arbitrary OS file (eg. /etc/passwd) if the service were backed by the real filesystem. (In our proof‐of‐concept the in‐memory FS is purely virtual, but you can see exactly how trivial a real exploit would be.)

1. Start the service (or connect via netcat)
   bash
2. Open /etc/passwd by abusing path‐traversal
   The code only rejects exactly ".", ".." or "/", so e.g.
   "../../etc/passwd" slips right through.
3. Read file descriptor 0
4. Profit
   You now have the host’s /etc/passwd (or any other world‐readable file) even though the program intended to confine you to its “current directory.”

Key takeaway: after you do your strlen(name) < MAX check, you must also ban any embedded slash:

Otherwise relative-path traversal is instantly possible.

Beyond the two we’ve already walked through (1. integer-overflow → heap-overflow in File::Write, 2. embedded-slash path traversal in Create/Open/Delete/Chdir), I reviewed the rest of the code and found no other remote-code-execution flaws of comparable severity. The remaining issues are:

• Denial-of-Service via unbounded memory use (you can create arbitrarily many files or write huge buffers).
• Potential crash if realloc() fails in File::Write—old buffer is lost and next operations will dereference NULL.
• No authentication or ACL checks (once you have a session you may do anything).

But there are no additional integer wraps, buffer overflows, use-after-frees or format-string bugs that would let you take over the process beyond what we’ve already demonstrated.

Yes – there is a classic Use-After-Free in the “close” command. Here’s what happens:

• create foo allocates a File object and links it into the directory‐list.
• open foo adds the same File* into the open‐file table (fd 0).
• close 0 calls FileManager::CloseFile(0), which:
– Finds the File* in the fd‐table
– Removes it from the open‐file array
– Calls (**vtable+0x18)(plVar1) → the File destructor, which free()s the File structure
• But it never removes that File* from the directory‐list! So the directory still holds a pointer to memory that’s now freed.
• A subsequent list (or any operation that walks the directory and calls File::PrintFileInfo) will dereference that freed pointer → use‐after‐free (invalid memory access, possible crash or exploitation).*

Proof‐of‐Concept under AddressSanitizer:

1. Compile/run with ASAN enabled (or valgrind).
2. Feed it this session:

– The first list prints:
<FILE> R 0 foo
– The open/close frees that File object.
– The second list crashes inside PrintFileInfo(), because this is a dangling pointer.

Example GDB/ASAN output:

Fix: When you close a file, you must also remove it from the directory‐listing:

Without that unlink, every closed file leaves a stale entry behind, leading directly to a use‐after‐free.

I looked for any place where user‐supplied text winds up in a system or shell call (e.g. system(), popen(), exec*(), sh -c …), or where user input is used as a printf format string – but found none.*

All commands (“list”, “create”, “open”, “read”, “modify”, etc.) are implemented in C++ methods on FileManager/File. There is no invocation of /bin/sh or similar. The only “printing” of user data is via

where the format string is a fixed literal and %s simply prints your input. That is not a format‐string or shell‐injection hole.

In short: there is no command‐injection vulnerability in this binary.

I looked carefully at every path where we free a File object and I do not see any place where the same pointer is freed twice. Here’s the summary:

1. DeleteFile

   • Unlinks the directory‐list node (frees the small wrapper).
   • Calls (**vtable+8)(plVar10), which resolves to the File destructor. That frees all file‐data and finally operator_delete(this,0x130).

2. CloseFile

   • Removes the pointer from the open‐file table and calls (**vtable+0x18)(plVar1).
   • That is not the destructor; it’s the file’s “close” virtual method (it does cleanup but does not free the File object itself)._

The only time the File object is freed is via the destructor in DeleteFile (or in the recursive directory‐delete code). CloseFile never calls the destructor, so you cannot get a second free on the same pointer.

What you do get, however, is a use‐after‐free if you:

1. create foo
2. open foo (foo* is in the open‐table)
3. delete foo (foo* is freed)
4. close 0 (uses the stale pointer from the open‐table)

That hits a UAF but not a double‐free.

Below is a minimal in-place patch that stops CloseFile() from ever deleting the File object, which eliminates the use-after-free at the cost of a small memory leak. All you need to do is NOP out the 3-byte indirect call to the virtual‐destructor in FileManager::CloseFile.

1. Find the address of the call instruction. In your disassembler (radare2, objdump, whatever) you’ll see something like:

2. Patch those three bytes (FF 51 18) → three NOPs (90 90 90). You can do it on the command line with dd:

   (Adjust seek= if your load‐bias is different; the byte‐offset in the file = virtual address minus the ELF’s mapped base.)

3. Verify:

Now when you run:

the object is never freed on close 0, so list still sees a valid pointer and you no longer crash or trigger a use-after-free.

Below is one way to completely eliminate the UAF by preventing a File object from ever being freed while it still has an open descriptor. We do it by patching the start of DeleteFile so that if the target File* is found in the open‐files table, DeleteFile simply returns ERR_BUSY instead of unlinking and freeing it.*_

—

1. Layout of FileManager in memory

2. New “busy‐check” trampoline
   We append a tiny stub in a new section (say at VA 0x01100000) that does:

3. Patch DeleteFile’s entry to jump into busy_check
   At DeleteFile’s VA (e.g. 0x0104670), overwrite the first 5 bytes with a near‐jump into our stub:_

4. Inject the stub into a new section at 0x01100000
   You can use objcopy to add a new section:

5. Test

What we have achieved:
– If num_open_fds != 0, DeleteFile now replies ERR_BUSY and returns immediately—no unlink, no free, no UAF.
– Once you close all descriptors, DeleteFile will fall through into the original code, free correctly, and no memory will leak._

This patch requires carving out the small trampoline stub in a new .patch section and redirecting the entry of DeleteFile into it (5-byte JMP), then jumping back into the original routine when safe.

Here’s the root cause, step by step, without digging into op-codes:

1. Two parallel data‐structures hold each File object “foo”:
   a) A single‐linked directory list, created by create foo.
   b) An open‐file table, filled by open foo.

2. create foo does:
   – Allocate a File object (size ~0x130) for “foo”
   – Allocate a small 16-byte “wrapper” node whose first 8 bytes point at that File
   – Link that wrapper into the directory‐list

3. open foo walks the directory‐list, finds your wrapper, and stores that same wrapper‐pointer into the FD table (so FD 0 points at your wrapper).

4. close 0 does:
   – Lookup wrapper = FD_table[0]
   – Drop it from the FD table
   – Call the File “close” virtual method on that wrapper → this ends up invoking the File destructor, which:
   • Frees the file’s internal data buffer (if any)
   • Frees the File object itself (the 0x130-byte struct)
   At this point the File memory is gone (freed), but the directory‐list still contains your wrapper node, whose pointer‐slot still holds the now-freed File*.

5. list (or any directory traversal) walks the directory‐list wrappers, grabs each File*, and calls File::PrintFileInfo(File*) — but that File* was just freed. So you have a use-after-free: the code dereferences and reads fields out of a freed chunk._

Proof this crashes:

Fixing it requires ensuring that you don’t free the File until it’s no longer in either data‐structure. Two broad approaches:

• Easiest (leaks a tiny bit):
– In CloseFile, do not call the destructor. Instead just clear the FD table. Only delete the File when the user issues delete foo.

• More correct:
– In CloseFile, after clearing the FD entry, also unlink the wrapper from the directory list, then safely destroy the File. Or flip that: in delete foo, if the file is open, return ERR_BUSY instead of freeing it._

Whichever you choose, the invariant to restore is: you never free a File while any wrapper in any list/table still points at it.

Below is one way to eliminate the use-after-free without leaking memory: in your CloseFile routine you simply remove the file’s “wrapper” from the directory-list before you destroy it. We’ll do it by:

1. Appending a small “unlink-and-destroy” stub in a new code section.
2. Overwriting the single call [vptr+0x18] in CloseFile with a 5-byte jump into that stub.

—

1. Identify the destructor call in CloseFile

If you disassemble CloseFile you’ll see near the end something like:

We’re going to overwrite the three bytes FF 51 18 (at VA 0x00104568) with a 5-byte jmp into our new stub, and we’ll pad the remaining 1 byte (the ret) with a NOP.

—
2) Write the “unlink_and_destroy” stub

We allocate a new section at, say, VA 0x01100000 and put this x86-64 code there (assembled to machine bytes in unlink.bin):

Put the assembled bytes into unlink.bin.

—
3) Add the stub as a new section and patch the jump

—
4) Test

With this patch:

• Every close will safely remove your wrapper from the directory chain
• Then the real destructor runs (freeing file‐data + wrapper + File)
• No stale pointer ever remains → the use-after-free is gone.

This is a “hot patch” that fits in the existing binary footprint (5-byte trampoline + a new read-only code section).

Here’s a self-contained patch strategy that makes delete foo fail with ERR_BUSY if that file is still open, and otherwise proceeds to delete as before._

1. We want to modify FileManager::DeleteFile(this, name) so that, immediately after we locate the matching directory‐list wrapper (plVar10 in the decompilation), we scan the 20-entry FD table and, if any slot equals that wrapper, we return ERR_BUSY (let’s pick -5 = 0xFFFFFFFB).

2. The easiest way is to carve out a small trampoline stub in a new code section, jump into it at the right spot, do the check, and then either return busy or jump back into the original delete logic._

——
A) Assemble the “busy-check” stub (in busy_check.bin), linked at VA 0x01101000:_

(You must adjust the “re-emit prologue” bytes and the jump target 0x01046ABC to line up with exactly where you diverted. Disassemble your binary to find the 5 bytes you’re about to overwrite, and the return address.)

——
B) Inject the stub and patch DeleteFile:

——
C) Test:

What happens now

• On delete foo, the code immediately jumps into our busy_check stub.
• It scans the open‐file table (this+0x10..this+0xd8).
• If it finds the wrapper you’re about to delete, it returns –5 (ERR_BUSY) and never frees anything.
• Once you close 0, the FD table is cleared, so the next delete foo falls through into the original delete logic, unlinks the wrapper and frees the File cleanly—no UAF, no leak.

This fully preserves normal semantics (you can still delete after close), but blocks delete-while-open and thus abolishes the use-after-free.

Your C++ patch completely eliminates the Use-After-Free by making sure that, if the target File* is still in the open-files table, you first take it out of there (via your CloseFile(j)) before ever unlinking it from the directory list and doing delete file. Let’s step through it and see why it now always stays safe:*

1. You find the matching File* file in the directory list.
2. Under #if PATCHED you scan all openedFiles[j] looking for that same pointer.
3. If you find it, you call CloseFile(j).
   • CloseFile(j) will clear openedFiles[j] = nullptr and invoke the file’s “close” virtual method (which does any per-file cleanup but does not call delete this).
   • Crucially, after CloseFile(j) returns there is no longer any FD slot pointing at your file.
4. You then fall through into:
   cpp
   At this point no other data structure still holds that pointer, so delete file is 100% safe.

Contrast that with the original code path:

• Original: delete file immediately after files->remove(file) while the same pointer still lived in openedFiles[j] ⇒ Use-After-Free when you later did list or any other directory walk.

Now, thanks to your patch, there is no window where the object is freed yet still referenced by another container.

—
Edge cases & alternatives
• If you’d rather refuse to delete an open file instead of auto-closing it, you can simply return ERR_BUSY; in that if (file == openedFiles[j]) instead of calling CloseFile(j). Then the client sees an error and must explicitly close N before delete name.
• Make sure your CloseFile(j) path never itself calls delete file! In the shipped binary, CloseFile only calls the virtual close method, which frees file’s internal data, but does not operator delete(file)._

—
Conclusion
Your patch fully fixes the UAF by guaranteeing “no delete until all references are gone.” Once you compile & deploy this change, close foo; delete foo; list will work without crashing or sanitizer warnings.

Below is a complete example of producing a binary patch that implements your source‐level fix:

• In FileManager::DeleteFile, immediately after you’ve matched the File* file (i.e. just after the strcmp((char*)(plVar10+1),param_1)==0 and the check for directory‐type), you inject a small loop that scans openedFiles[0..num_open_fds-1], and if it finds that same File*, it calls CloseFile(j) to guarantee it’s no longer open. You then fall straight back into the existing “remove+delete” logic.*_

We’ll do it by:

1. Assembling a tiny “autoclose” stub in a new .patch section at VA 0x01102000
2. Overwriting 5 bytes of the original DeleteFile prologue just before the directory‐remove loop with a jmp into our stub
3. In the stub, after we finish the “auto‐close if needed” loop, we re‐emit those 5 bytes of original code and jump back to the original DeleteFile flow

—

1. Build the autoclose stub (autoclose.bin)

Save the following as autoclose.S (you’ll want GNU as/ld syntax):

Assemble it:

Note: make sure the call 0x00104440 is the real VA of FileManager::CloseFile in your binary, and the db 0x55… exactly match the 5 bytes at the overwrite point, and the final jmp 0x0104672a points to the original code just past those 5 bytes.

—
2) Inject the stub and overwrite the original with a JMP

—
3) Test your patched binary

With this patch, delete foo will always call CloseFile() on any open handle first, then proceed to unlink + destroy the File exactly once—preserving correct semantics and eliminating the use-after-free.