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using System.Security.Cryptography;
using System.Text;
using Agent.Windows.Security;
namespace Agent.Windows.Recovery;
public sealed class TransactionalFileEditor(TaskResourceJournal journal, string backupRoot, long memoryBackupLimitBytes = 16 * 1024 * 1024)
{
public FileEditTransaction Replace(string path, string content, string? expectedSha256 = null) => Replace(path, Encoding.UTF8.GetBytes(content), expectedSha256);
public FileEditTransaction Replace(string path, ReadOnlySpan<byte> content, string? expectedSha256 = null)
{
string canonical = CanonicalPath.Resolve(path, requireExisting: false);
bool existed = File.Exists(canonical);
byte[]? original = existed ? File.ReadAllBytes(canonical) : null;
string originalHash = original is null ? string.Empty : Convert.ToHexString(SHA256.HashData(original));
if (expectedSha256 is not null && !originalHash.Equals(NormalizeHash(expectedSha256), StringComparison.Ordinal))
throw new SandboxPolicyException("file.concurrent_change", "File hash does not match expected_sha256.");
string backupPath = string.Empty;
string inline = string.Empty;
if (original is not null && original.LongLength > memoryBackupLimitBytes)
{
string directory = System.IO.Path.Combine(backupRoot, journal.TaskId.ToString("N"));
Directory.CreateDirectory(directory);
backupPath = System.IO.Path.Combine(directory, Guid.NewGuid().ToString("N") + ".backup");
File.WriteAllBytes(backupPath, original);
}
else if (original is not null) inline = Convert.ToBase64String(original);
string temporary = canonical + ".agent-mcp-" + Guid.NewGuid().ToString("N") + ".tmp";
var data = new Dictionary<string, string>
{
["existed"] = existed.ToString(), ["original_sha256"] = originalHash, ["original_base64"] = inline,
["backup_path"] = backupPath, ["temporary_path"] = temporary
};
Guid entryId = journal.Prepare("file.replace", canonical, data);
File.WriteAllBytes(temporary, content);
string replacementHash = Convert.ToHexString(SHA256.HashData(content));
File.Move(temporary, canonical, overwrite: true);
journal.MarkApplied(entryId, new Dictionary<string, string> { ["replacement_sha256"] = replacementHash });
return new(journal, entryId, canonical, originalHash, replacementHash, backupPath, inline, existed);
}
public FileDeleteTransaction Delete(string path, string? expectedSha256 = null)
{
string canonical = CanonicalPath.Resolve(path);
byte[] original = File.ReadAllBytes(canonical);
string originalHash = Convert.ToHexString(SHA256.HashData(original));
if (expectedSha256 is not null && !originalHash.Equals(NormalizeHash(expectedSha256), StringComparison.Ordinal))
throw new SandboxPolicyException("file.concurrent_change", "File hash does not match expected_sha256.");
string backupPath = string.Empty;
string inline = string.Empty;
if (original.LongLength > memoryBackupLimitBytes)
{
string directory = System.IO.Path.Combine(backupRoot, journal.TaskId.ToString("N"));
Directory.CreateDirectory(directory);
backupPath = System.IO.Path.Combine(directory, Guid.NewGuid().ToString("N") + ".backup");
File.WriteAllBytes(backupPath, original);
}
else inline = Convert.ToBase64String(original);
Guid entryId = journal.Prepare("file.delete", canonical, new Dictionary<string, string>
{
["original_sha256"] = originalHash, ["original_base64"] = inline, ["backup_path"] = backupPath
});
File.Delete(canonical);
journal.MarkApplied(entryId);
return new(journal, entryId, canonical, originalHash, backupPath, inline);
}
private static string NormalizeHash(string hash) => hash.Replace("-", string.Empty, StringComparison.Ordinal).Trim().ToUpperInvariant();
}
public sealed class FileDeleteTransaction(TaskResourceJournal journal, Guid entryId, string path, string originalHash, string backupPath, string originalBase64)
{
private bool _finished;
public void Commit() { if (_finished) return; Cleanup(); journal.MarkCleaned(entryId); _finished = true; }
public void Rollback()
{
if (_finished) return;
if (File.Exists(path)) throw new InvalidOperationException("Rollback refused because the deleted path was recreated.");
byte[] original = backupPath.Length > 0 ? File.ReadAllBytes(backupPath) : Convert.FromBase64String(originalBase64);
if (!Convert.ToHexString(SHA256.HashData(original)).Equals(originalHash, StringComparison.Ordinal)) throw new InvalidDataException("Delete backup hash verification failed.");
File.WriteAllBytes(path, original);
Cleanup(); journal.MarkCleaned(entryId); _finished = true;
}
private void Cleanup()
{
if (backupPath.Length == 0) return;
File.Delete(backupPath);
string? parent = System.IO.Path.GetDirectoryName(backupPath);
if (parent is not null && Directory.Exists(parent) && !Directory.EnumerateFileSystemEntries(parent).Any()) Directory.Delete(parent);
}
}
public sealed class FileEditTransaction(
TaskResourceJournal journal, Guid entryId, string path, string originalHash, string replacementHash,
string backupPath, string originalBase64, bool originallyExisted)
{
private bool _finished;
public void Commit()
{
if (_finished) return;
DeleteBackup();
journal.MarkCleaned(entryId);
_finished = true;
}
public void Rollback()
{
if (_finished) return;
if (!File.Exists(path) || !Hash(path).Equals(replacementHash, StringComparison.Ordinal))
throw new InvalidOperationException("Rollback refused because the replacement file changed after the transaction.");
if (originallyExisted)
{
byte[] original = backupPath.Length > 0 ? File.ReadAllBytes(backupPath) : Convert.FromBase64String(originalBase64);
if (!Convert.ToHexString(SHA256.HashData(original)).Equals(originalHash, StringComparison.Ordinal)) throw new InvalidDataException("Backup hash verification failed.");
string temporary = path + ".rollback-" + Guid.NewGuid().ToString("N") + ".tmp";
File.WriteAllBytes(temporary, original);
File.Move(temporary, path, overwrite: true);
}
else File.Delete(path);
DeleteBackup();
journal.MarkCleaned(entryId);
_finished = true;
}
private void DeleteBackup()
{
if (backupPath.Length == 0) return;
File.Delete(backupPath);
string? parent = System.IO.Path.GetDirectoryName(backupPath);
if (parent is not null && Directory.Exists(parent) && !Directory.EnumerateFileSystemEntries(parent).Any()) Directory.Delete(parent);
}
private static string Hash(string target)
{
using FileStream stream = File.OpenRead(target);
return Convert.ToHexString(SHA256.HashData(stream));
}
}
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