/// <summary>
/// Validates whether a <see cref="LocalFileSystemProvider"/> was configured
/// with access restricted to a given <see cref="LocalFileSystemProvider.RootDirectory"/>,
/// and makes sure that the requested <paramref name="file"/> is indeed contained
/// within that folder.
/// </summary>
/// <param name="file">The requested file resource.</param>
/// <param name="submittedFilePath">The path that was submitted in the original request.</param>
/// <param name="context">The currently performed file system operation.</param>
/// <exception cref="ResourceAccessException">If the requested resource is not
/// a descendant of a configured <see cref="LocalFileSystemProvider.RootDirectory"/>.</exception>
/// <exception cref="ArgumentNullException">If <paramref name="file"/>
/// is a null reference.</exception>
private void ValidateFileRequestAccess(FileItem file, string submittedFilePath, FileSystemTask context)
{
if (file == null)
{
throw new ArgumentNullException("file");
}
//if there isn't a restricted custom root, every file resource can be accessed
//(if the path is invalid, this will fail otherwise, depending on the action)
if (RootDirectory == null)
{
return;
}
try {
//if we have a custom root, make sure the resource is indeed a descendant of the root
if (RootDirectory.IsParentOf(file.LocalFile.FullName))
{
return;
}
}
catch (ResourceAccessException e) {
//just bubble a resource access exception
if (e.Resource == null)
{
e.Resource = file.ResourceInfo;
}
throw;
}
catch (Exception e) {
//exceptions can happen in case of invalid file paths
//log detailed info
string error = "Resource request for file [{0}] caused exception when validating against root directory [{1}].";
error = String.Format(error, submittedFilePath, RootDirectory.FullName);
AuditHelper.AuditException(Auditor, e, AuditLevel.Warning, context, AuditEvent.InvalidFilePathFormat, error);
//do not expose too much path information (e.g. absolute paths if disabled)
error = String.Format("Invalid file path: [{0}].", submittedFilePath);
throw new ResourceAccessException(error, e)
{
Resource = file.ResourceInfo, IsAudited = true
};
}
//if none of the above is true, the request is invalid
//log detailed info
string msg = "Resource request for file [{0}] was blocked. The resource is outside the root directory [{1}].";
msg = String.Format(msg, file.ResourceInfo.FullName, RootDirectory.FullName);
Auditor.Audit(AuditLevel.Warning, context, AuditEvent.InvalidResourceLocationRequested, msg);
//do not expose too much path information (e.g. absolute paths if disabled)
msg = String.Format("Invalid file path: [{0}].", submittedFilePath);
throw new ResourceAccessException(msg)
{
Resource = file.ResourceInfo, IsAudited = true
};
}
public void Submitted_Exceptions_Should_Indicate_They_Have_Been_Audited_After_Processing()
{
VfsException e = new ResourceAccessException("hello");
Assert.IsFalse(e.IsAudited);
AuditHelper.AuditException(auditor, e, FileSystemTask.RootFolderInfoRequest);
Assert.IsTrue(e.IsAudited);
}
public void Submitted_Exceptions_Should_Be_Logged()
{
VfsException e = new ResourceAccessException("hello");
AuditHelper.AuditException(auditor, e, FileSystemTask.RootFolderInfoRequest);
Assert.AreEqual(1, auditor.Items.Count);
Assert.AreEqual(FileSystemTask.RootFolderInfoRequest, auditor.Items[0].Context);
}
public void Exceptions_With_Audit_Suppression_Should_Be_Ignored()
{
VfsException e = new ResourceAccessException("hello")
{
SuppressAuditing = true
};
AuditHelper.AuditException(auditor, e, FileSystemTask.RootFolderInfoRequest);
Assert.AreEqual(0, auditor.Items.Count);
}
public void Already_Audited_Exceptions_Should_Not_Be_Audited_Anymore()
{
VfsException e = new ResourceAccessException("hello")
{
IsAudited = true
};
AuditHelper.AuditException(auditor, e, FileSystemTask.RootFolderInfoRequest);
Assert.AreEqual(0, auditor.Items.Count);
}
/// <summary>
/// Provides exception handling and auditing for a given function.
/// </summary>
/// <param name="task">The context, used for auditing exceptions that may occur.</param>
/// <param name="action">The action to be invoked.</param>
/// <param name="errorMessage">Returns an error message in case of an unhandled exception
/// that is not derived from <see cref="VfsException"/>.</param>
/// <param name="auditor">The auditor that receives the exceptions.</param>
/// <returns>The result of the submitted <paramref name="action"/> function.</returns>
public static void SecureAction(FileSystemTask task, Action action, Func <string> errorMessage, IAuditor auditor)
{
try
{
action();
}
catch (VfsException e)
{
//just audit and rethrow VFS exceptions
AuditHelper.AuditException(auditor, e, task);
throw;
}
catch (Exception e)
{
//wrap unhandled exception into VFS exception
var exception = new ResourceAccessException(errorMessage(), e);
AuditHelper.AuditException(auditor, exception, task);
throw exception;
}
}