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refactor: replace manual TAR parser with SharpCompress for OVA reading

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System.Formats.Tar is not available as a standalone NuGet backport for
netstandard2.0/net48. Use SharpCompress 0.38.0 on all targets for a
single, well-tested code path that handles GNU long filenames, PAX
extended headers, and other TAR variants correctly.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
This commit is contained in:
Clint Branham
2026-03-20 13:16:08 -05:00
parent b19911ef06
commit 6a03be4af2
2 changed files with 11 additions and 125 deletions
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src/PSProxmoxVE.Core/Models/Vms/OvfMetadata.cs
+8 -125
View File
@@ -78,144 +78,27 @@ namespace PSProxmoxVE.Core.Models.Vms
}
/// <summary>
/// Extracts the .ovf XML content from a TAR archive.
/// Uses System.Formats.Tar on .NET 9+ and manual TAR parsing on older frameworks.
/// Extracts the .ovf XML content from a TAR archive using SharpCompress.
/// </summary>
private static string? ExtractOvfFromTar(string tarPath)
{
#if NET7_0_OR_GREATER
return ExtractOvfUsingSystemTar(tarPath);
#else
return ExtractOvfManualTar(tarPath);
#endif
}
#if NET7_0_OR_GREATER
private static string? ExtractOvfUsingSystemTar(string tarPath)
{
using var stream = File.OpenRead(tarPath);
using var reader = new System.Formats.Tar.TarReader(stream);
using var reader = SharpCompress.Readers.ReaderFactory.Open(stream);
System.Formats.Tar.TarEntry? entry;
while ((entry = reader.GetNextEntry()) != null)
while (reader.MoveToNextEntry())
{
if (entry.Name.EndsWith(".ovf", StringComparison.OrdinalIgnoreCase) && entry.DataStream != null)
if (!reader.Entry.IsDirectory &&
reader.Entry.Key != null &&
reader.Entry.Key.EndsWith(".ovf", StringComparison.OrdinalIgnoreCase))
{
using var sr = new StreamReader(entry.DataStream, Encoding.UTF8, detectEncodingFromByteOrderMarks: true, bufferSize: 4096, leaveOpen: true);
using var entryStream = reader.OpenEntryStream();
using var sr = new StreamReader(entryStream, Encoding.UTF8);
return sr.ReadToEnd();
}
}
return null;
}
#else
/// <summary>
/// Minimal TAR reader for netstandard2.0/net48.
/// TAR format: 512-byte header per file, name at offset 0 (100 bytes), size at offset 124 (12 bytes octal),
/// followed by file data padded to 512-byte boundary.
/// </summary>
private static string? ExtractOvfManualTar(string tarPath)
{
using var stream = File.OpenRead(tarPath);
var header = new byte[512];
while (true)
{
var bytesRead = ReadFull(stream, header, 0, 512);
if (bytesRead < 512)
break;
// Check for end-of-archive (two zero blocks)
if (IsZeroBlock(header))
break;
// Extract name (offset 0, 100 bytes)
var name = ReadNullTerminatedString(header, 0, 100);
// Extract size (offset 124, 12 bytes, octal)
var sizeStr = ReadNullTerminatedString(header, 124, 12).Trim();
long size = 0;
if (!string.IsNullOrEmpty(sizeStr))
{
try { size = Convert.ToInt64(sizeStr, 8); }
catch { size = 0; }
}
// Check for GNU/POSIX long name prefix (offset 345, 155 bytes)
var prefix = ReadNullTerminatedString(header, 345, 155);
if (!string.IsNullOrEmpty(prefix))
name = prefix + "/" + name;
if (name.EndsWith(".ovf", StringComparison.OrdinalIgnoreCase) && size > 0)
{
var data = new byte[size];
var dataRead = ReadFull(stream, data, 0, (int)size);
if (dataRead < size)
throw new InvalidOperationException("Unexpected end of OVA archive while reading .ovf entry.");
return Encoding.UTF8.GetString(data);
}
// Skip past the file data (padded to 512-byte boundary)
if (size > 0)
{
var paddedSize = ((size + 511) / 512) * 512;
SkipBytes(stream, paddedSize);
}
}
return null;
}
private static int ReadFull(Stream stream, byte[] buffer, int offset, int count)
{
int totalRead = 0;
while (totalRead < count)
{
int read = stream.Read(buffer, offset + totalRead, count - totalRead);
if (read == 0) break;
totalRead += read;
}
return totalRead;
}
private static void SkipBytes(Stream stream, long count)
{
if (stream.CanSeek)
{
stream.Seek(count, SeekOrigin.Current);
}
else
{
var buf = new byte[Math.Min(count, 8192)];
long remaining = count;
while (remaining > 0)
{
int toRead = (int)Math.Min(remaining, buf.Length);
int read = stream.Read(buf, 0, toRead);
if (read == 0) break;
remaining -= read;
}
}
}
private static bool IsZeroBlock(byte[] block)
{
for (int i = 0; i < block.Length; i++)
{
if (block[i] != 0) return false;
}
return true;
}
private static string ReadNullTerminatedString(byte[] buffer, int offset, int maxLength)
{
int end = offset;
int limit = offset + maxLength;
while (end < limit && buffer[end] != 0)
end++;
return Encoding.ASCII.GetString(buffer, offset, end - offset);
}
#endif
/// <summary>
/// Parses OVF XML and extracts VM metadata.
src/PSProxmoxVE.Core/PSProxmoxVE.Core.csproj
+3
View File
@@ -19,16 +19,19 @@
<ItemGroup Condition="'$(TargetFramework)' == 'netstandard2.0'">
<PackageReference Include="Newtonsoft.Json" Version="13.0.3" />
<PackageReference Include="System.Text.Json" Version="8.0.5" />
<PackageReference Include="SharpCompress" Version="0.38.0" />
</ItemGroup>
<ItemGroup Condition="'$(TargetFramework)' == 'net48'">
<PackageReference Include="Newtonsoft.Json" Version="13.0.3" />
<PackageReference Include="System.Text.Json" Version="8.0.5" />
<PackageReference Include="SharpCompress" Version="0.38.0" />
<Reference Include="System.Net.Http" />
</ItemGroup>
<ItemGroup Condition="'$(TargetFramework)' == 'net9.0'">
<PackageReference Include="Newtonsoft.Json" Version="13.0.3" />
<PackageReference Include="SharpCompress" Version="0.38.0" />
</ItemGroup>
</Project>