NXErase

NXErase is a secure deletion utility designed to protect sensitive data from theft, malware, and unauthorized recovery, specifically optimized for the era of Solid State Drives (SSDs), NVMe, and Full Disk Encryption.

While traditional tools (shred, srm, dd) were built for spinning hard drives, NXErase addresses the specific challenges of flash storage (specifically Wear Leveling and Garbage Collection) by combining cryptographic overwriting with hardware-aware command sets to ensure deleted files cannot be retrieved by bad actors.

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📑 Table of Contents

• Why NXErase?
• Key Features
• Installation
• Usage
• Technical Architecture
• Security & Safety Mechanisms
• Limitations
• License

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⚡ Why NXErase? (The NVMe Advantage)

Legacy tools are becoming dangerous placebos on modern hardware. When shred overwrites a file on an SSD, the drive's firmware (Wear Leveling) often writes the new random data to new physical cells to preserve drive health. The original data remains in the old cells until the drive decides to garbage collect them, leaving a window of opportunity for malware or data thieves to recover the information.

NXErase fixes this by using a 3-stage destruction process:

1. Overwrite: Writes cryptographically strong random noise to the logical address.
2. Punch Hole (The SSD Fix): Issues a FALLOC_FL_PUNCH_HOLE syscall. On supported filesystems (Ext4, Btrfs, XFS), this sends an immediate TRIM/DISCARD command to the controller, explicitly marking the physical blocks as invalid/garbage.
3. Obfuscate: Renames the file to a random string before unlinking to hide metadata.

Comparison:

Feature	NXErase	shred / srm	rm
Storage Target	NVMe / SSD / HDD	Spinning HDD	Generic
Method	Crypto Overwrite + TRIM	Overwrite Only	Unlink Only
Recovery Protection	High (Force GC + Obfuscation)	Low on SSD	None
Speed	Multi-threaded (Rayon)	Single-threaded	Instant
Sanitization	Yes (Crypto Erase)	No	No
Immutable Files	Auto-unlocks (chattr -i)	Fails	Fails

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🚀 Key Features

• Parallel Execution: Uses a thread pool (rayon) to wipe thousands of small files instantly, saturating the high command queue depth of modern NVMe drives.
• NVMe Sanitize Mode: Interfaces directly with the drive controller to perform instant Crypto Erase (destroys the internal encryption key) or Block Erase (wipes all NAND).
• Immutable File Handling: Automatically detects chattr +i (locked) files. If run as root, it uses raw IOCTLs to unlock, wipe, and remove them transparently.
• Audit Logging: Optional --log-file produces timestamped logs for compliance and audit trails.
• Memory Safe: Uses streaming iterators to handle directories containing millions of files without crashing system RAM.

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📦 Installation

Prerequisites

• Rust (Cargo): To compile from source.
• nvme-cli: Required only if you plan to use the --sanitize feature.

Build from Source

# 1. Clone the repository
git clone https://github.com/yourusername/nxerase.git
cd nxerase

# 2. Build Release Binary
cargo build --release

# 3. Install to system path
sudo cp target/release/nxerase /usr/local/bin/
sudo chmod +x /usr/local/bin/nxerase

Dependencies (Optional)

If you need the Device Sanitization feature:

# Debian/Ubuntu
sudo apt install nvme-cli

# Fedora
sudo dnf install nvme-cli

# Arch Linux
sudo pacman -S nvme-cli

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🛠 Usage

File Deletion (Standard Mode)

Securely wipe files or directories. Safe to use on mounted filesystems.

# Wipe a single file
nxerase secret.pdf

# Wipe a directory recursively (multi-threaded)
nxerase -r private_photos/

# Wipe with audit logging enabled
nxerase --log-file /var/log/wipe.log sensitive_data/

Device Sanitization (Destructive)

WARNING: This destroys ALL data on the entire drive. Requires root.

# Instant Crypto Erase (Recommended for NVMe)
# This destroys the drive's internal encryption key, making data unrecoverable instantly.
sudo nxerase --sanitize --device /dev/nvme0n1

Command Line Options

Flag Description

-j, --jobs <N>	Number of worker threads (Default: Logical CPU count).

--throttle <MS>	Sleep <MS> milliseconds between 1MB chunks (reduces thermal load).

--no-progress	Disable the interactive progress bar (recommended for scripts).

--allow-hardlinks	Force overwriting of files with multiple hard links.

-n, --dry-run	Simulate the operation without deleting anything.

--log-file <PATH>	Append audit logs to the specified file.

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🧠 Technical Architecture

For every file processed, NXErase performs a rigorous pipeline designed to defeat forensic recovery:

1. TOCTOU Verification: Opens the file using O_NOFOLLOW and verifies Inode/Device IDs to prevent Time-of-Check Time-of-Use race conditions.

2. Unlock: Checks FS_IMMUTABLE_FL via ioctl. If set, clears it (requires root).

3. Overwrite: Fills the file with random data generated by the OS CSPRNG (OsRng).

4. Discard: Calls fallocate with FALLOC_FL_PUNCH_HOLE. This triggers the SSD firmware to mark blocks as garbage immediately.

5. Obfuscate: Renames the file to a random 12-char string (e.g., .tmp_a8z91lx) while holding the file descriptor.

6. Unlink: Removes the obfuscated inode.

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🛡 Security & Safety Mechanisms

NXErase is built with a "Safety First" philosophy:

• Symlink Protection: Explicitly checks lstat and opens with O_NOFOLLOW. It will never follow a symbolic link, preventing accidental deletion of system files.

• Hard Link Detection: By default, it skips files with nlink > 1 to prevent destroying data shared by other file paths (e.g., backups/snapshots).

• Abort-on-Failure: If the Overwrite phase fails (e.g., interruption, I/O error), the tool aborts immediately without deleting the file. This prevents leaving behind "ghost" files that look deleted but still contain recoverable data.

• Network Awareness: Detects and warns if the target is on NFS/SMB/FUSE, where secure deletion guarantees cannot be enforced.

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⚠️ Limitations

1. Physical Guarantee: No software-only tool can guarantee 100% physical erasure on flash storage due to Overprovisioning and bad-block remapping. For Top Secret classification, physical destruction or the --sanitize (firmware) command is required.

2. Journaling Filesystems: Metadata (filenames, timestamps) might persist in the filesystem journal (Ext4/XFS) for a short time, though the file content will be destroyed.

3. LUKS: This tool is most effective when used on a drive with Full Disk Encryption (LUKS). The combination of Overwrite + TRIM on an encrypted volume renders forensic recovery mathematically impossible without the master key.

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📄 License

This project is licensed under the Apache License 2.0. See the LICENSE file for details.