public byte[] GetDecryptedAssignment(Guid submissionId)
{
SubmissionViewModel submission = _assignmentsService.GetSubmission(submissionId);
FileStream fs = new FileStream(submission.FilePath, FileMode.Open, FileAccess.Read);
MemberViewModel teacher = _membersService.GetMember(submission.Member.TeacherEmail);
byte[] key = CryptographicHelper.AsymmetricDecrypt(
Convert.FromBase64String(submission.SymmetricKey), teacher.PrivateKey);
byte[] iv = CryptographicHelper.AsymmetricDecrypt(
Convert.FromBase64String(submission.SymmetricIV), teacher.PrivateKey);
MemoryStream ms = new MemoryStream();
fs.CopyTo(ms);
byte[] encryptedAssignment = ms.ToArray();
byte[] decryptedAssignment = CryptographicHelper.SymmetricDecrypt(
encryptedAssignment,
key, iv);
return(decryptedAssignment);
}
public override void OnActionExecuting(ActionExecutingContext context)
{
AssignmentsController controller = (AssignmentsController)context.Controller;
ILogger logger = controller.GetLogger();
try
{
var id = Guid.Parse(CryptographicHelper.SymmetricDecrypt(context.ActionArguments["id"].ToString()));
var loggedInUser = context.HttpContext.User.Identity.Name;
IAssignmentsService assignmentsService = (IAssignmentsService)context.HttpContext.RequestServices.GetService(typeof(IAssignmentsService));
if (loggedInUser != assignmentsService.GetSubmission(id).Member.Email&& !context.HttpContext.User.IsInRole("Teacher"))
{
IPHostEntry iphostinfo = Dns.GetHostEntry(Dns.GetHostName());
string ipaddress = Convert.ToString(iphostinfo.AddressList.FirstOrDefault(address => address.AddressFamily == System.Net.Sockets.AddressFamily.InterNetwork));
logger.LogInformation(loggedInUser + " on IP " + ipaddress + " tried to access submission with id " + id + ". Access was denied");
context.Result = new UnauthorizedObjectResult("Access Denied");
}
}
catch (Exception ex)
{
logger.LogInformation("Bad request when user tried to access a file");
context.Result = new BadRequestObjectResult("Bad Request");
}
base.OnActionExecuting(context);
}
public IActionResult ViewSubmission(string id)
{
Guid decryptedId = Guid.Parse(
HttpUtility.UrlDecode(
CryptographicHelper.SymmetricDecrypt(id)));
ViewSubmissionViewModel submission = new ViewSubmissionViewModel();
submission.Submission = _assignmentsService.GetSubmission(decryptedId);
if (User.IsInRole("Teacher"))
{
var checks = CheckForAuthandInt(decryptedId);
if (checks.Item2 == false)
{
ViewData["isAuthentic"] = 0;
}
}
var comments = _assignmentsService.GetComments(decryptedId);
ViewBag.Comments = comments;
return(View(submission));
}
public IActionResult ViewSubmissions(string assigmmentId)
{
Guid decryptedAssignmentId = Guid.Parse(
HttpUtility.UrlDecode(
CryptographicHelper.SymmetricDecrypt(assigmmentId)));
var list = _assignmentsService.GetSubmissions(decryptedAssignmentId);
return(View(list));
}
public IActionResult SubmitAssignment(string id)
{
Guid decryptedId = Guid.Parse(
HttpUtility.UrlDecode(CryptographicHelper.SymmetricDecrypt(id)));
CookieOptions cookieOptions = new CookieOptions();
Response.Cookies.Append("Assignment", id, cookieOptions);
var assignment = _assignmentsService.GetAssignment(decryptedId);
ViewBag.Assignment = assignment;
return(View());
}
public IActionResult Delete(string id)
{
try
{
Guid decryptedId = Guid.Parse(
HttpUtility.UrlDecode(CryptographicHelper.SymmetricDecrypt(id)));
_assignmentsService.DeleteAssignment(decryptedId);
ViewData["info"] = "Assignment deleted";
}catch (Exception ex)
{
ViewData["warning"] = "Error deleting assignment";
}
return(RedirectToAction("Index"));
}
public IActionResult ViewFile(string id)
{
Guid decryptedId = Guid.Parse(HttpUtility.UrlDecode(CryptographicHelper.SymmetricDecrypt(id)));
byte[] decryptedAssignment = GetDecryptedAssignment(decryptedId);
IPHostEntry iphostinfo = Dns.GetHostEntry(Dns.GetHostName());
string ipaddress = Convert.ToString(iphostinfo.AddressList.FirstOrDefault(address => address.AddressFamily == System.Net.Sockets.AddressFamily.InterNetwork));
if (User.IsInRole("Teacher"))
{
_logger.LogInformation("Teacher " + User.Identity.Name + " on IP " + ipaddress + " accessed file of submission " + decryptedId + " on " + DateTime.Now);
}
else if (User.IsInRole("Student"))
{
_logger.LogInformation("Student " + User.Identity.Name + " on IP " + ipaddress + " accessed file of submission " + decryptedId + " on " + DateTime.Now);
}
return(File(decryptedAssignment, "application/pdf"));
}
public Tuple <bool, bool> CheckForAuthandInt(Guid id)
{
bool isDistinct = true;
bool isVerified = true;
SubmissionViewModel submission = _assignmentsService.GetSubmission(id);
var submissions = _assignmentsService.GetSubmissions(submission.Assignment.Id);
MemberViewModel teacher = _membersService.GetMember(submission.Member.TeacherEmail);
byte[] key = CryptographicHelper.AsymmetricDecrypt(
Convert.FromBase64String(submission.SymmetricKey), teacher.PrivateKey);
byte[] iv = CryptographicHelper.AsymmetricDecrypt(
Convert.FromBase64String(submission.SymmetricIV), teacher.PrivateKey);
foreach (SubmissionViewModel sub in submissions)
{
if (sub.FileHash == submission.FileHash && sub.Member.Email != submission.Member.Email)
{
TempData["warning"] += "Assignment is identical to " + sub.Member.Email + "'s assignment!\n";
isDistinct = false;
}
}
if (!CryptographicHelper.VerifySignature(
CryptographicHelper.SymmetricDecrypt(
Convert.FromBase64String(submission.Signature), key, iv),
CryptographicHelper.Hash(GetDecryptedAssignment(id)),
submission.Member.PublicKey))
{
isVerified = false;
}
return(new Tuple <bool, bool>(isDistinct, isVerified));
}
public IActionResult SubmitAssignment(IFormFile file)
{
var assignment = _assignmentsService.GetAssignment(Guid.Parse(CryptographicHelper.SymmetricDecrypt(Request.Cookies["Assignment"])));
ViewBag.Assignment = assignment;
if (file != null)
{
Stream stream = file.OpenReadStream();
int firstByte = stream.ReadByte();
int secondByte = stream.ReadByte();
int thirdByte = stream.ReadByte();
int fourthByte = stream.ReadByte();
stream.Position = 0;
//If the file passes the following check, a submission is created with user credentials
if (firstByte == 37 && secondByte == 80 && thirdByte == 68 && fourthByte == 70 && Path.GetExtension(file.FileName) == ".pdf")
{
SubmissionViewModel submission = new SubmissionViewModel();
submission.Member = _membersService.GetMember(User.Identity.Name);
Tuple <byte[], byte[]> keys = CryptographicHelper.GenerateKeys();
MemberViewModel teacher = _membersService.GetMember(submission.Member.TeacherEmail);
string encryptedKey = Convert.ToBase64String(CryptographicHelper.AsymmetricEncrypt(keys.Item1, teacher.PublicKey));
string encryptedIv = Convert.ToBase64String(CryptographicHelper.AsymmetricEncrypt(keys.Item2, teacher.PublicKey));
submission.SymmetricKey = encryptedKey;
submission.SymmetricIV = encryptedIv;
submission.Assignment = _assignmentsService.GetAssignment(assignment.Id);
string absolutePath = _host.WebRootPath + @"\..\ProtectedFiles\";
string uniqueName = Guid.NewGuid().ToString() + Path.GetExtension(file.FileName);
using (MemoryStream ms = new MemoryStream())
{
stream.CopyTo(ms);
ms.Position = 0;
submission.FileHash = Convert.ToBase64String(CryptographicHelper.Hash(ms.ToArray()));
var signature = CryptographicHelper.GenerateSignature(Convert.FromBase64String(submission.FileHash), submission.Member.PrivateKey);
submission.Signature = Convert.ToBase64String(CryptographicHelper.SymmetricEncrypt(
signature,
keys.Item1, keys.Item2));
System.IO.File.WriteAllBytes(absolutePath + uniqueName,
CryptographicHelper.SymmetricEncrypt(
ms.ToArray(),
keys.Item1,
keys.Item2
)
);
}
submission.FilePath = absolutePath + uniqueName;
_assignmentsService.AddSubmission(submission);
TempData["info"] = "File accepted";
return(RedirectToAction("index"));
}
else
{
TempData["warning"] = "File is not valid, only PDF allowed";
return(View());
}
}
else
{
TempData["warning"] = "Please upload a file";
return(View());
}
}