FATFS Ready in wolfSSH 1.4.21
wolfSSH 1.4.21 is now available, and this release focuses on making FATFS-backed SFTP deployments easier to ship, test, and maintain. Since tagging v1.4.20-stable, we invested in reliability improvements, developer tooling, and CI coverage that harden FATFS integration for embedded SSH gateways, industrial control systems, and secure file transfer clients. This article captures the highlights so you can take advantage of the new capabilities immediately.
Key FATFS improvements in wolfSSH 1.4.21
- Reliable builds: Compiler fixes revive FATFS configurations that previously stalled with missing macros or mismatched function signatures.
- Linux reference design: A new sample project demonstrates FATFS using a disk image so you can validate wolfsftp behavior on any developer workstation or CI runner.
- Continuous testing: A GitHub Actions workflow automates end-to-end FATFS validation, from provisioning wolfSSL to verifying file integrity inside the mounted image.
- Lean source management: FATFS source bundles are now cached instead of committed, keeping our repository lightweight while staying in sync with upstream ff15a.
- Warning-free code: We eliminated type warnings that triggered -Werror, keeping embedded toolchains clean.
Hardening the compile path
The fixes remove the sharp edges developers hit when enabling WOLFSSH_FATFS. We corrected the WRENAME wrapper signature, added the missing WFFLUSH macro, and automatically define WOLFSSH_STOREHANDLE so SFTP handles are persisted correctly. We also gated POSIX-oriented setters (setstat and related helpers) when FATFS is active, aligning the build with the capabilities of the filesystem abstraction. Combined with the NO_FILESYSTEM compatibility tweak in port.h, FATFS-enabled builds now succeed without manual patching.
FATFS on Linux in minutes
Need a quick way to evaluate FATFS behavior without hardware? The new ide/Linux-FATFS/ reference design spins up a FATFS volume stored inside fatfs_image.img. The example mounts the image during startup, runs wolfsftp operations, then unmounts it cleanly when you exit. Follow the README to download the upstream FATFS 0.15a package, copy in ffconf.h, and compile the shared library. Pair it with the recommended configuration flags to build wolfSSH 1.4.21 with FATFS support:
LD_LIBRARY_PATH=ide/Linux-FATFS ./configure \
--enable-sftp \
CFLAGS="-DWOLFSSH_FATFS -Iide/Linux-FATFS/source -DSTDIN_FILENO=0 -DPRINTF=printf" \
LDFLAGS="-Lide/Linux-FATFS -lfatfs"
This workflow mirrors the one we run in CI and gives firmware teams a reproducible baseline for regression testing embedded SFTP transfers.
Automated FATFS validation in GitHub Actions
To keep wolfSSH 1.4.21 release-ready, we added a dedicated GitHub Actions pipeline. The job installs dependencies, builds wolfSSL with FATFS-friendly options (–disable-filesystem), compiles the Linux example library, and then drives wolfsftp through a scripted session that transfers a randomly generated test file. The workflow finishes by mounting the FATFS image, verifying checksums, and reporting any mismatch as a failure. Subsequent updates turned FATFS into a cached download step so each run pulls a pristine archive from elm-chan.org without inflating the repository size. This CI coverage catches regressions long before they reach production firmware.
Eliminating compiler warnings
Customer feedback in April flagged a pointer-type warning that tripped -Werror in production builds. Casting the WMALLOC return value to FIL* resolves the diagnostic and keeps FATFS parity with our other storage back ends. The warning fix is small but essential for downstream projects that enforce zero-warning policies.
Why FATFS matters for embedded SFTP
Many embedded systems rely on FATFS to expose removable media or NAND flash as a POSIX-like filesystem. By tightening FATFS support in wolfSSH 1.4.21, we enable secure SFTP transfers directly on microcontrollers and RTOS platforms without porting a full filesystem stack. The result is faster development cycles, leaner firmware images, and consistent behavior across desktop validation and on-target deployments.
Stay in touch
wolfSSH 1.4.21 is live today, and we welcome feedback on these FATFS enhancements. If you have additional scenarios to test—or if you need assistance tailoring wolfSSH for your hardware—reach out at support@wolfssl.com. For commercial licensing, evaluation builds, or professional services, contact sales@wolfssl.com.
Continue the conversation
Now that 1.4.21 is released, subscribe to the wolfSSL newsletter and follow our blog for more deep dives into embedded SSH, SFTP optimization, and cryptography for resource-constrained devices. We look forward to seeing what you build with wolfSSH 1.4.21 and its upgraded FATFS toolkit.
If you have questions about any of the above, please contact us at facts@wolfssl.com or call us at +1 425 245 8247.
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