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Windows: fix failure of PowerShell script to create container from a large directory

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we now add a safety factor and extra space to better account for exfat filesystem overhead.
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Mounir IDRASSI 2024-07-27 00:55:22 +02:00
parent 1e92048017
commit 6121ca0239
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GPG Key ID: FC1B00364B3FE937
1 changed files with 33 additions and 5 deletions
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38
contrib/EncryptData.ps1
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@ -23,7 +23,7 @@ The desired path for the VeraCrypt container. If not specified, it defaults to t
.NOTES
Author: Mounir IDRASSI
Email: mounir.idrassi@idrix.fr
Date: July 2023
Date: 26 July 2024
License: This script is licensed under the Apache License 2.0
#>
@ -77,8 +77,10 @@ $veraCryptFormatExe = Join-Path $veracryptPath "VeraCrypt Format.exe"
# Constants used to calculate the size of the exFAT filesystem
$InitialVBRSize = 32KB
$BackupVBRSize = 32KB
$InitialFATSize = 128KB
$ClusterSize = 32KB # TODO : make this configurable
$UpCaseTableSize = 128KB # Typical size
function Get-ExFATSizeRec {
param(
@ -142,7 +144,7 @@ function Get-ExFATSize {
try {
# Initialize total size
$totalSize = $InitialVBRSize + $InitialFATSize
$totalSize = $InitialVBRSize + $BackupVBRSize + $InitialFATSize + $UpCaseTableSize
# Call the recursive function
$totalSize = Get-ExFATSizeRec -Path $Path -TotalSize $totalSize
@ -151,13 +153,24 @@ function Get-ExFATSize {
$totalSize += $ClusterSize
# Calculate the size of the Bitmap Allocation Table
$numClusters = $totalSize / $ClusterSize
$numClusters = [math]::Ceiling($totalSize / $ClusterSize)
$bitmapSize = [math]::Ceiling($numClusters / 8)
$totalSize += $bitmapSize
# Adjust the size of the FAT
$fatSize = $numClusters * 4
$totalSize += $fatSize - $InitialFATSize
# Add safety factor to account for potential filesystem overhead
# For smaller datasets (<100MB), we add 1% or 64KB (whichever is larger)
# For larger datasets (>=100MB), we add 0.1% or 1MB (whichever is larger)
# This scaled approach ensures adequate extra space without excessive overhead
$safetyFactor = if ($totalSize -lt 100MB) {
[math]::Max(64KB, $totalSize * 0.01)
} else {
[math]::Max(1MB, $totalSize * 0.001)
}
$totalSize += $safetyFactor
# Return the minimum disk size needed to store the exFAT filesystem
return $totalSize
@ -171,10 +184,25 @@ function Get-ExFATSize {
# Calculate size of the container
$containerSize = Get-ExFATSize -Path $inputPath
# Convert to MB and round up to the nearest MB
$containerSize = [math]::Ceiling($containerSize / 1MB)
# Add 1 MiB to account for the VeraCrypt headers and reserved areas (256 KiB), plus other overhead
$containerSize += 1
# Add extra space for VeraCrypt headers, reserved areas, and potential alignment requirements
# We use a sliding scale to balance efficiency for small datasets and adequacy for large ones:
# - For very small datasets (<10MB), add 1MB
# - For small to medium datasets (10-100MB), add 2MB
# - For larger datasets (>100MB), add 1% of the total size
# This approach ensures sufficient space across a wide range of dataset sizes
if ($containerSize -lt 10) {
$containerSize += 1 # Add 1 MB for very small datasets
} elseif ($containerSize -lt 100) {
$containerSize += 2 # Add 2 MB for small datasets
} else {
$containerSize += [math]::Ceiling($containerSize * 0.01) # Add 1% for larger datasets
}
# Ensure a minimum container size of 2 MB
$containerSize = [math]::Max(2, $containerSize)
# Specify encryption algorithm, and hash algorithm
$encryption = "AES"