private static async Task ReadDebAsync(
string debPath,
string outputDir,
Func <string, string> getEntryPath,
bool shouldExtract)
{
// Debian packages (.deb) are "ar" archives with three files.
//
// 8 bytes for signature (should be "!<arch>\n")
//
// Each section has the following header:
// - 16 bytes for file identifier (ASCII)
// - 12 bytes for file modification timestamp (decimal)
// - 6 bytes for owner ID (decimal)
// - 6 bytes for group ID (decimal)
// - 8 bytes for file mode (octal)
// - 10 bytes for file size (decimal)
// - 2 bytes for ending characters ("`\n")
//
// The three sections are:
// - Package Section
// - Control Section
// - Data Section
//
// We only care about the data section and we expect it to be a .tar.xz.
const int signatureLength = 8;
const int headerLength = 16 + 12 + 6 + 6 + 8 + 10 + 2;
var buffer = new byte[headerLength];
using (var fileStream = new FileStream(debPath, FileMode.Open))
{
var read = fileStream.Read(buffer, 0, signatureLength);
if (read != signatureLength || Encoding.ASCII.GetString(buffer, 0, read) != "!<arch>\n")
{
throw new TorSharpException("The Debian package did not have the expected file signature.");
}
read = fileStream.Read(buffer, 0, headerLength);
var packageSectionHeader = ArFileHeader.Read(buffer);
if (read != headerLength ||
packageSectionHeader.FileSize != 4)
{
throw new TorSharpException("The Debian package did not have the expected package section file header.");
}
fileStream.Position += packageSectionHeader.FileSize;
read = fileStream.Read(buffer, 0, headerLength);
var controlSectionHeader = ArFileHeader.Read(buffer);
fileStream.Position += controlSectionHeader.FileSize;
read = fileStream.Read(buffer, 0, headerLength);
var dataSectionHeader = ArFileHeader.Read(buffer);
var trimmedFileIdentifier = dataSectionHeader.FileIdentifier.TrimEnd();
if (!trimmedFileIdentifier.EndsWith(".tar.xz"))
{
throw new TorSharpException("The Debian package's data section is expected to be a .tar.xz file.");
}
if (fileStream.Position + dataSectionHeader.FileSize != fileStream.Length)
{
throw new TorSharpException("The Debian package's data section is expected to reach the end of the .dev file.");
}
if (!shouldExtract)
{
await ReadTarXzAsync(
fileStream,
outputDir,
getEntryPath,
shouldExtract : false).ConfigureAwait(false);
}
else
{
await ReadTarXzAsync(
fileStream,
outputDir,
getEntryPath,
shouldExtract : true).ConfigureAwait(false);
}
}
}
