Harden a file handle validation and add a unit test

[yosuke-wolfssl]

This PR extends the existing handleList infrastructure to validate the requested handle during SFTP operations.
The target functions:

• wolfSSH_SFTP_RecvRead
• wolfSSH_SFTP_RecvWrite
• wolfSSH_SFTP_RecvFSetSTAT
• wolfSSH_SFTP_RecvClose
• wolfSSH_SFTP_RecvFSTAT

These functions do the validation of the requested handle using new helper SFTP_ValidateFileHandle.
SFTP_GetHandleNode, SFTP_AddHandleNode, SFTP_RemoveHandleNode, and SFTP_FreeHandles are not wrapped with WOLFSSH_STOREHANDLE anymore because these are used by this validation logic.
But, WOLFSSH_STOREHANDLE still exists for the original purpose: WOLFSSH_STOREHANDLE gates only name = cur->name in RecvFSTAT. The settings.h auto-defines for FATFS / Nucleus / Harmony / MQX remain meaningful because those platforms pass the filename to their fstat equivalents.

Also, this PR add a unit test for validation helper.

Addressed by f_4232, f_4343, f_4346, f_4349

[Copilot]

Pull request overview

Hardens SFTP file-handle handling on the server. A new helper SFTP_ValidateFileHandle checks both the size of an incoming handle and its presence in the per-session handleList, and is now invoked from RecvRead, RecvWrite, RecvClose, RecvFSTAT, and RecvFSetSTAT. The handle table is no longer gated on WOLFSSH_STOREHANDLE (that macro now only controls whether RecvFSTAT looks up the cached filename), so all server SFTP builds get this validation. A new unit test TestSftpValidateFileHandle covers the helper.

Changes:

• Add SFTP_ValidateFileHandle / SFTP_ValidateFileHandle_ex and call them from the read/write/close/fstat/fsetstat handlers.
• Always compile WS_HANDLE_LIST, handleList, and the SFTP_*HandleNode helpers; restrict WOLFSSH_STOREHANDLE to gating only the cached-name use in RecvFSTAT.
• Add wolfSSH_TestSftpValidateFileHandle test wrapper and TestSftpValidateFileHandle regression test, and re-gate the existing handle test on !NO_WOLFSSH_SERVER instead of WOLFSSH_STOREHANDLE.

Reviewed changes

Copilot reviewed 4 out of 4 changed files in this pull request and generated 1 comment.

File	Description
wolfssh/internal.h	Move WS_HANDLE_LIST definition out of WOLFSSH_STOREHANDLE and unconditionally include handleList in WOLFSSH.
wolfssh/wolfsftp.h	Constify name in SFTP_AddHandleNode; declare wolfSSH_TestSftpValidateFileHandle for unit tests.
src/wolfsftp.c	Introduce validation helpers, replace ad-hoc size checks in SFTP receive paths, and remove WOLFSSH_STOREHANDLE gating around handle-list bookkeeping.
tests/regress.c	Re-gate existing SFTP handle test, add TestSftpValidateFileHandle, and register it in main.

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[wolfSSL-Fenrir-bot]

Fenrir Automated Review — PR #997

Scan targets checked: wolfssh-bugs, wolfssh-src
Findings: 2
1 finding(s) posted as inline comments (see file-level comments below)

Medium (1)

Windows handle cleanup uses CRT close

File: src/wolfsftp.c:4538
Function: SFTP_FreeHandles
Category: API contract violations

SFTP_FreeHandles() closes stored Windows HANDLE values through WCLOSE, which maps to _close(int), so abandoned SFTP file handles are not closed correctly on Windows.

Recommendation: Add a USE_WINDOWS_API branch that copies a HANDLE from cur->handle and calls CloseHandle.

Referenced code: src/wolfsftp.c:4538-4542 (5 lines)

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This review was generated automatically by Fenrir. Findings are non-blocking.

[wolfSSL-Fenrir-bot]

Fenrir Automated Review — PR #997

Scan targets checked: wolfssh-bugs, wolfssh-src
Findings: 1

Medium (1)

Windows cleanup closes stored HANDLEs with the wrong API

File: src/wolfsftp.c:4562
Function: SFTP_FreeHandles
Category: API contract violations

On Windows, RecvOpen stores HANDLE values in handleList, but SFTP_FreeHandles() closes entries as WFD through WCLOSE. Session cleanup leaks open Windows file handles and can pass truncated handle bits to _close.

Recommendation: Add a USE_WINDOWS_API branch that calls CloseHandle(*(HANDLE*)cur->handle) for stored Windows handles.

Referenced code: src/wolfsftp.c:4562-4566 (5 lines)

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This review was generated automatically by Fenrir. Findings are non-blocking.