我正在编写一个程序来帮助我收集有关密码安全性的研究报告的统计数据。我决定在尝试强制使用MD5哈希密码时，使应用程序在多个线程上运行，以显着提高性能。应用程序在单个线程上运行正常，但是当2个线程正在运行时，StackOverFlowException将在TryPass函数中使用“using（MD5 md5Hash = MD5.Create（））”。
// Microsoft's GetMd5Hash function.
static string GetMd5Hash(MD5 md5Hash, string input)
{
// Convert the input string to a byte array and compute the hash.
byte[] data = md5Hash.ComputeHash(Encoding.UTF8.GetBytes(input));
// Create a new Stringbuilder to collect the bytes
// and create a string.
StringBuilder sBuilder = new StringBuilder();
// Loop through each byte of the hashed data
// and format each one as a hexadecimal string.
for (int i = 0; i < data.Length; i++)
{
sBuilder.Append(data[i].ToString("x2"));
}
// Return the hexadecimal string.
return sBuilder.ToString();
}
static bool TryPass(string attempt, string password)
{
using (MD5 md5Hash = MD5.Create())
{
if (GetMd5Hash(md5Hash, attempt) == password)
return true;
else
return false;
}
}
static bool BruteForce(BruteOptions bruteOptions)
{
if (bruteOptions.prefix.Length == 1 && TryPass(bruteOptions.prefix, bruteOptions.password)) // If it's the first in a series, try it.
return true;
for (int i = 0; i < bruteOptions.chars.Length; i++)
{
if (TryPass(bruteOptions.prefix + bruteOptions.chars[i], bruteOptions.password))
{
Console.WriteLine("The password is: " + bruteOptions.prefix + bruteOptions.chars[i]);
return true;
}
if (bruteOptions.prefix.Length + 1 < bruteOptions.maxLength)
if (BruteForce(bruteOptions))
return true;
//Console.WriteLine(prefix + chars[i]);
}
return false;
}
public struct BruteOptions
{
public string password, prefix;
public char[] chars;
public int maxLength;
}
static void OptionBruteForce()
{
Console.WriteLine("-----------------------");
Console.WriteLine("----- Brute-Force -----");
Console.WriteLine("-----------------------");
BruteOptions bruteOptions = new BruteOptions();
bruteOptions.password = ReadString("Enter the MD5 password hash to brute-force: ");
bruteOptions.chars = ReadString("Enter the characters to use: ").ToCharArray();
bruteOptions.maxLength = ReadIntegerRange("Max length of password: ", 1, 16);
bruteOptions.prefix = "";
Stopwatch myStopWatch = Stopwatch.StartNew();
int NUM_THREADS = bruteOptions.chars.Length;
Thread[] workers = new Thread[NUM_THREADS]; // Run a thread for each char.
var countdownEvent = new CountdownEvent(NUM_THREADS);
bool result = false;
// Start workers.
for (int i = 0; i < NUM_THREADS; i++)
{
int index = i;
BruteOptions newBruteOptions = bruteOptions;
newBruteOptions.prefix = bruteOptions.chars[index].ToString();
workers[index] = new Thread(delegate()
{
// Also check single char.
if (BruteForce(bruteOptions))
{
result = true;
// End all other threads.
for (int ii = 0; ii < NUM_THREADS; ii++)
{
if (workers[ii].ThreadState == System.Threading.ThreadState.Running && index != ii) // Ensures we don't prematurely abort this thread.
{
workers[ii].Abort();
countdownEvent.Signal(); // Signal so we can zero it and continue on the UI thread.
}
}
}
// Signal the CountdownEvent.
countdownEvent.Signal();
});
workers[index].Start();
}
// Wait for workers.
countdownEvent.Wait();
if (!result)
Console.WriteLine("No Match.");
Console.WriteLine("Took " + myStopWatch.ElapsedMilliseconds + " Milliseconds");
}
这就是所有相关的代码。任何有关为什么会发生这种情况的见解将不胜感激！我完全难过了。我尝试在初始化每个线程时指定更大的堆栈大小，但没有用。
提前致谢！
答案 0 :(得分：1)
你的static bool BruteForce(BruteOptions bruteOptions)是无限递归的：如果长度允许，它会调用自身，并使用相同的参数：
if (bruteOptions.prefix.Length + 1 < bruteOptions.maxLength)
if (BruteForce(bruteOptions))
bruteOptions保持与函数入口相同。
作为解决方案，您可以使用以下代码：
if (bruteOptions.prefix.Length + 1 < bruteOptions.maxLength)
{
BruteOptions newOptions = bruteOptions;
newOptions.prefix += bruteOptions.chars[i];
if (BruteForce(newOptions))
return true;
}
另外，您将bruteOptions而不是newBruteOptions传递给您在main函数中使用的委托。因此，实际上并没有使用多线程。所有线程都测试相同的密码。将其更改为newBruteOptions。
此外，不要假设有关线程执行顺序的任何信息。您假设所有工作人员都在找到正确的密码时填满，这可能是错误的。然后，您将在此行中获得NullReferenceException：
if (workers[ii].ThreadState == System.Threading.ThreadState.Running && index != ii) // Ensures we don't prematurely abort this thread.
答案 1 :(得分：0)
我猜你的单线程代码看起来有点不同。
我会失去递归。
答案 2 :(得分：0)
只是为了踢，这里是一个没有递归的替代实现，并且更好地利用了作为.Net的一部分提供的语言结构和框架
class Program
{
private static string StringFromIndexPermutation(char[] characters, int[] indexes)
{
var buffer = new char[indexes.Length];
for (var i = 0; i < buffer.Length; ++i)
{
buffer[i] = characters[indexes[i]];
}
return new string(buffer);
}
/// <summary>
/// Increments a set of "digits" in a base "numberBase" number with the MSD at position 0
/// </summary>
/// <param name="buffer">The buffer of integers representing the numeric string</param>
/// <param name="numberBase">The base to treat the digits of the number as</param>
/// <returns>false if the number in the buffer has just overflowed, true otherwise</returns>
private static bool Increment(int[] buffer, int numberBase)
{
for (var i = buffer.Length - 1; i >= 0; --i)
{
if ((buffer[i] + 1) < numberBase)
{
++buffer[i];
return true;
}
buffer[i] = 0;
}
return false;
}
/// <summary>
/// Calculate all the permutations of some set of characters in a string from length 1 to maxLength
/// </summary>
/// <param name="characters">The characters to permute</param>
/// <param name="maxLength">The maximum length of the permuted string</param>
/// <returns>The set of all permutations</returns>
public static IEnumerable<string> Permute(char[] characters, int maxLength)
{
for (var i = 0; i < maxLength; ++i)
{
var permutation = new int[i + 1];
yield return StringFromIndexPermutation(characters, permutation);
while (Increment(permutation, characters.Length))
{
yield return StringFromIndexPermutation(characters, permutation);
}
}
}
static string ReadString(string message)
{
Console.Write(message);
return Console.ReadLine();
}
private static int ReadIntegerRange(string message, int min, int max)
{
Console.Write(message + "({0} - {1})", min, max);
while(true)
{
var test = Console.ReadLine();
int value;
if (int.TryParse(test, out value))
{
return value;
}
}
return -1;
}
static void OptionBruteForce()
{
Console.WriteLine("-----------------------");
Console.WriteLine("----- Brute-Force -----");
Console.WriteLine("-----------------------");
var password = ReadString("Enter the MD5 password hash to brute-force: ");
var chars = ReadString("Enter the characters to use: ").Distinct().ToArray();
var maxLength = ReadIntegerRange("Max length of password: ", 1, 16);
var myStopWatch = Stopwatch.StartNew();
var result = false;
string match = null;
var cancellationTokenSource = new CancellationTokenSource();
var passwordBytes = Encoding.Default.GetBytes(password);
var originalMd5 = MD5.Create();
var passwordHash = originalMd5.ComputeHash(passwordBytes);
var hashAlgGetter = new ConcurrentDictionary<Thread, MD5>();
try
{
Parallel.ForEach(Permute(chars, maxLength), new ParallelOptions
{
CancellationToken = cancellationTokenSource.Token
}, test =>
{
var md5 = hashAlgGetter.GetOrAdd(Thread.CurrentThread, t => MD5.Create());
var data = Encoding.Default.GetBytes(test);
var hash = md5.ComputeHash(data);
if (hash.SequenceEqual(passwordHash))
{
myStopWatch.Stop();
match = test;
result = true;
cancellationTokenSource.Cancel();
}
});
}
catch (OperationCanceledException)
{
}
if (!result)
{
Console.WriteLine("No Match.");
}
else
{
Console.WriteLine("Password is: {0}", match);
}
Console.WriteLine("Took " + myStopWatch.ElapsedMilliseconds + " Milliseconds");
}
static void Main()
{
OptionBruteForce();
Console.ReadLine();
}
}