I am searching for C# Code to reproduce the following openssl command.
openssl enc -d -aes-256-cbc -in my_encrypted_file.csv.enc -out my_decrypted_file.csv -pass file:key.bin
Additional information:
The encrypted file in present as byte[]
The key.bin is a byte[] with length of 256 (the key is obtained by a more simple decryption of yet another file, which i managed to realize in C#).
I have been trying out various examples found by searching the web.
The problem is, that all of these examples require an IV (initialization vector). Unfortunately, I don't have an IV and no one on the team knows what this is or how it could be defined.
The openssl command does not seem to need one, so I am a bit confused about this.
Currently, the code, I am trying with, looks as follows:
public static string DecryptAesCbc(byte[] cipheredData, byte[] key)
{
string decrypted;
System.Security.Cryptography.Aes aes = System.Security.Cryptography.Aes.Create();
aes.KeySize = 256;
aes.Key = key;
byte[] iv = new byte[aes.BlockSize / 8];
aes.IV = iv;
aes.Mode = CipherMode.CBC;
ICryptoTransform decipher = aes.CreateDecryptor(aes.Key, aes.IV);
using (MemoryStream ms = new MemoryStream(cipheredData))
{
using (CryptoStream cs = new CryptoStream(ms, decipher, CryptoStreamMode.Read))
{
using (StreamReader sr = new StreamReader(cs))
{
decrypted = sr.ReadToEnd();
}
}
return decrypted;
}
}
The code fails saying that my byte[256] key has the wrong length for this kind of algorithm.
Thanks for any help with this!
Cheers, Mike
The posted OpenSSL statement uses the -pass file: option and thus a passphrase (which is read from a file), see openssl enc. This causes the encryption process to first generate a random 8 bytes salt and then, together with the passphrase, derive a 32 bytes key and 16 bytes IV using the (not very secure) proprietary OpenSSL function EVP_BytesToKey. This function uses several parameters, e.g. a digest and an iteration count. The default digest for key derivation is MD5 and the iteration count is 1. Note that OpenSSL version 1.1.0 and later uses SHA256 as default digest, i.e. depending on the OpenSSL version used to generate the ciphertext, the appropriate digest must be used for decryption. Preceding the ciphertext is a block whose first 8 bytes is the ASCII encoding of Salted__, followed by the 8 bytes salt.
Therefore, the decryption must first determine the salt. Based on the salt, together with the passphrase, key and IV must be derived and then the rest of the encrypted data can be decrypted. Thus, first of all an implementation of EVP_BytesToKey in C# is required, e.g. here. Then a possible implementation could be (using MD5 as digest):
public static string DecryptAesCbc(byte[] cipheredData, string passphrase)
{
string decrypted = null;
using (MemoryStream ms = new MemoryStream(cipheredData))
{
// Get salt
byte[] salt = new byte[8];
ms.Seek(8, SeekOrigin.Begin);
ms.Read(salt, 0, 8);
// Derive key and IV
OpenSslCompat.OpenSslCompatDeriveBytes db = new OpenSslCompat.OpenSslCompatDeriveBytes(passphrase, salt, "MD5", 1);
byte[] key = db.GetBytes(32);
byte[] iv = db.GetBytes(16);
using (Aes aes = Aes.Create())
{
aes.Padding = PaddingMode.PKCS7;
aes.Mode = CipherMode.CBC;
aes.Key = key;
aes.IV = iv;
// Decrypt
ICryptoTransform decipher = aes.CreateDecryptor(aes.Key, aes.IV);
using (CryptoStream cs = new CryptoStream(ms, decipher, CryptoStreamMode.Read))
{
using (StreamReader sr = new StreamReader(cs, Encoding.UTF8))
{
decrypted = sr.ReadToEnd();
}
}
}
}
return decrypted;
}
Note that the 2nd parameter of DecryptAesCbc is the passphrase (as string) and not the key (as byte[]). Also note that StreamReader uses an encoding (UTF-8 by default), which requires compatible data (i.e. text data, but this should be met for csv files). Otherwise (i.e. for binary data as opposed to text data) StreamReader must not be used.
Related
I would like to encrypt data in iOS app with a SymetricKey and the CryptoKit and decrypt on server side with C# in Net Core.
iOS code:
class Security {
static let keyStr = "d5a423f64b607ea7c65b311d855dc48f" //32
static let iv="31348c0987c7" //12
class func encode(_ text:String)->String {
let key=SymmetricKey(data: Security.keyStr.data(using: .utf8)!)
let nonce=try! AES.GCM.Nonce(data: iv.data(using: .utf8)!)
let encrypted=try! AES.GCM.seal(text.data(using: .utf8)!, using: key, nonce: nonce)
return encrypted.combined!.base64EncodedString()
}
}
I pass the result of the encryption to my backend and I would like to decrypt
C# Code:
public string decrypt(string encryptedText)
{
string keyStr = "d5a423f64b607ea7c65b311d855dc48f";
string iv = "31348c0987c7";
string plaintext = "";
Debug.WriteLine(encryptedText);
using (Aes aesAlg = Aes.Create())
{
Debug.WriteLine(AesGcm.IsSupported);
var key = System.Text.Encoding.UTF8.GetBytes(keyStr);
var iV = System.Text.Encoding.UTF8.GetBytes(iv);
aesAlg.Key = key;
aesAlg.IV = iV;
// Create a decryptor to perform the stream transform.
ICryptoTransform decryptor = aesAlg.CreateDecryptor(aesAlg.Key, aesAlg.IV);
// Create the streams used for decryption.
using (MemoryStream msDecrypt = new MemoryStream(Convert.FromBase64String(request.pswd)))
{
using (CryptoStream csDecrypt = new CryptoStream(msDecrypt, decryptor, CryptoStreamMode.Read))
{
using (StreamReader srDecrypt = new StreamReader(csDecrypt))
{
// Read the decrypted bytes from the decrypting stream
// and place them in a string.
plaintext = srDecrypt.ReadToEnd();
}
}
}
}
Debug.WriteLine(plaintext);
}
So for example word: Test gets encrypted as: MzEzNDhjMDk4N2M3CI68IDEJeBR4OFtWO3GPO3TIgos=
When I get to line:
aesAlg.IV = iV;
I get an error "Specified initialization vector (IV) does not match the block size for this algorithm."
It seems as if C# needs byte[16], but in iOS I seem to be stuck with 12.
I got stuck at this point. Any idea greately appreciated.
Thank you.
The posted Swift code applies AES in GCM mode, s. AES.GCM. The posted C# code also uses AES, however not the GCM mode, but the default CBC mode (s. Aes, Mode).
The CBC mode applies a 16 bytes IV, while the GCM mode uses a 12 bytes nonce. That is what the error message is pointing to.
For successful decryption, AES in GCM mode must also be used on the C# side. In .NET AES in GCM mode is supported with the AesGcm class (as of .NET Core 3.0).
Note also that the data given by the Swift code is the Base64 encoding of the concatenation of 12 bytes nonce, ciphertext and 16 bytes tag (in that order), which must be separated in the C# code, where the portions are processed individually.
A possible C# implementation that decrypts the ciphertext generated by the posted Swift code is:
byte[] nonceCiphertextTag = Convert.FromBase64String("MzEzNDhjMDk4N2M3CI68IDEJeBR4OFtWO3GPO3TIgos=");
byte[] key = Encoding.UTF8.GetBytes("d5a423f64b607ea7c65b311d855dc48f");
Span<byte> nonceCiphertextTagSpan = nonceCiphertextTag.AsSpan();
Span<byte> nonce = nonceCiphertextTagSpan[..12];
Span<byte> ciphertext = nonceCiphertextTagSpan[12..^16];
Span<byte> tag = nonceCiphertextTagSpan[^16..];
byte[] plaintext = new byte[ciphertext.Length];
using AesGcm aesGcm = new AesGcm(key);
aesGcm.Decrypt(nonce, ciphertext, tag, plaintext); // throws an 'CryptographicException: The computed authentication tag did not match the input authentication tag' if authentication fails
Console.WriteLine(Encoding.UTF8.GetString(plaintext)); // Test
Edit: An alternative to the native .NET class AesGcm is C#/BouncyCastle. Maybe this is supported in your environment:
using Org.BouncyCastle.Crypto.Engines;
using Org.BouncyCastle.Crypto.Modes;
using Org.BouncyCastle.Crypto.Parameters;
...
byte[] nonceCiphertextTag = Convert.FromBase64String("MzEzNDhjMDk4N2M3CI68IDEJeBR4OFtWO3GPO3TIgos=");
byte[] key = Encoding.UTF8.GetBytes("d5a423f64b607ea7c65b311d855dc48f");
Span<byte> nonceCiphertextTagSpan = nonceCiphertextTag.AsSpan();
byte[] nonce = nonceCiphertextTagSpan[..12].ToArray();
byte[] ciphertextTag = nonceCiphertextTagSpan[12..].ToArray();
GcmBlockCipher gcmBlockCipher = new GcmBlockCipher(new AesEngine());
AeadParameters aeadParameters = new AeadParameters(new KeyParameter(key), 128, nonce);
gcmBlockCipher.Init(false, aeadParameters);
byte[] plaintext = new byte[gcmBlockCipher.GetOutputSize(ciphertextTag.Length)];
int length = gcmBlockCipher.ProcessBytes(ciphertextTag, 0, ciphertextTag.Length, plaintext, 0);
gcmBlockCipher.DoFinal(plaintext, length); // throws an 'InvalidCipherTextException: mac check in GCM failed' if authentication fails
Console.WriteLine(Encoding.UTF8.GetString(plaintext)); // Test
Note that unlike the native AesGcm class, C#/BouncyCastle requires the concatenation of ciphertext and tag, so only the nonce needs to be separated.
Why does this code return the weak key error?
static public byte[] TDESDecrypt(byte[] toDecrypt, byte[] key, CipherMode mode = CipherMode.ECB, PaddingMode padding = PaddingMode.None)
{
TripleDESCryptoServiceProvider tdes = new TripleDESCryptoServiceProvider();
tdes.Key = key;
tdes.Mode = mode;
tdes.Padding = padding;
ICryptoTransform cTransform = tdes.CreateDecryptor();
byte[] resultArray = cTransform.TransformFinalBlock(toDecrypt, 0, toDecrypt.Length);
tdes.Clear();
return resultArray;
}
When I try to execute the line "tdes.Key = key", I get the error
deriveSessionKeyIS System.Security.Cryptography.CryptographicException:
Specified key is a known weak key for TripleDES and cannot be used
Why? The key I'm trying is random, but one of the tested keys, for example, is FB13347FE570DC4FFB13347FE570DC4F. Where is the problem?
You can read in wikipedia for example about what is the weak key in cryptography. For triple DES there is a method (TripleDES.IsWeakKey) which checks triple DES key for weakness. In you case, key FB13347FE570DC4FFB13347FE570DC4F is symmetric in a sense that first 8 bytes of it are exactly equal last 8 bytes. That means if you encrypt something with that key, and then encrypt that encrypted info one more time - you will restore original text (because of how this concrete encryption algorithm works), which is obviously dangerous.
So in short .NET protects you from doing dangerous things resulting in cryptographic weakness. If you will use standard GenerateKey() function to generate key (or just don't set Key explicitly) - weak keys won't be generated.
A bit more information about why that key is weak for triple DES. 3DES is named like this because it essentially uses 3 keys and applies pure DES encryption\decryption with those keys 3 times. Each key is 8 bytes long, so 3DES key size is 8*3 = 24 bytes. However, algorithm also allows for first and third keys to be the same, and as such allows to use 16-byte keys (like in your example). In that case first half of those 16-bytes are used as a third key. This option provides less security but is still viable.
Now, when in your case first half and second half of your 16-bytes key are the same, so all three keys which will be used by 3DES are the same. Given that 3DES works like this:
DES encrypt with 3rd(DES Decrypt with 2nd(DES Encrypt with 1st(plaintext)))
You see that in your case you fall back to using simple DES, which defeats whole purpose of using 3DES in the first place.
It is a weak 3DES key because the additional 8-byte will again be repeated as the last 8-bits. Thus the 3DES encryption has reverted to DES and that is weak.
3DES does three operations, in the most common form of ede the data is first encrypted with the first 8-bytes of the key, then decrypted with the second 8-bytes and finally encrypted with the final 8-bytes (which in this case are the first 8-bytes). Note that after the first two operations the data is back to the original data thus the only encryption that is actually performed is the last encryption and that is 8-bytes which is a 56-bit key. That is a weak 3DES key.
I found this solution on MSDN Forum. This solution works perfectly with weak keys.
With the code from the forum I made this:
using System.Security.Cryptography;
using System.IO;
using System.Reflection;
static class MyDES
{
public static byte[] Encrypt(byte[] data, byte[] key, byte[] IV)
{
MemoryStream mStream = new MemoryStream();
DESCryptoServiceProvider des = new DESCryptoServiceProvider();
des.Mode = CipherMode.ECB;
des.Padding = PaddingMode.None;
CryptoStream cStream = new CryptoStream(mStream,
des.CreateWeakEncryptor(key, IV),
CryptoStreamMode.Write);
cStream.Write(data, 0, data.Length);
cStream.FlushFinalBlock();
byte[] ret = mStream.ToArray();
cStream.Close();
mStream.Close();
return ret;
}
public static byte[] Decrypt(byte[] data, byte[] key, byte[] IV)
{
MemoryStream msDecrypt = new MemoryStream(data);
DESCryptoServiceProvider des = new DESCryptoServiceProvider();
des.Mode = CipherMode.ECB;
des.Padding = PaddingMode.None;
CryptoStream csDecrypt = new CryptoStream(msDecrypt,
des.CreateWeakDecryptor(key, IV),
CryptoStreamMode.Read);
byte[] fromEncrypt = new byte[data.Length];
csDecrypt.Read(fromEncrypt, 0, fromEncrypt.Length);
return fromEncrypt;
}
#region DESCryptoExtensions
public static ICryptoTransform CreateWeakEncryptor(this DESCryptoServiceProvider cryptoProvider, byte[] key, byte[] iv)
{
MethodInfo mi = cryptoProvider.GetType().GetMethod("_NewEncryptor", BindingFlags.NonPublic | BindingFlags.Instance);
object[] Par = { key, cryptoProvider.Mode, iv, cryptoProvider.FeedbackSize, 0 };
ICryptoTransform trans = mi.Invoke(cryptoProvider, Par) as ICryptoTransform;
return trans;
}
public static ICryptoTransform CreateWeakEncryptor(this DESCryptoServiceProvider cryptoProvider)
{
return CreateWeakEncryptor(cryptoProvider, cryptoProvider.Key, cryptoProvider.IV);
}
public static ICryptoTransform CreateWeakDecryptor(this DESCryptoServiceProvider cryptoProvider, byte[] key, byte[] iv)
{
return CreateWeakEncryptor(cryptoProvider, key, iv);
}
public static ICryptoTransform CreateWeakDecryptor(this DESCryptoServiceProvider cryptoProvider)
{
return CreateWeakDecryptor(cryptoProvider, cryptoProvider.Key, cryptoProvider.IV);
}
#endregion
}
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I try to convert this code to php, but i can't and always i get different result in C# and PHP
Here is my C# code for encrypt and decrypt :
private static readonly byte[] initVectorBytes = Encoding.ASCII.GetBytes("1234567812345678");
private const int keysize = 256;
private string pass = "sample";
public static string Encrypt(string plainText, string passPhrase)
{
byte[] plainTextBytes = Encoding.UTF8.GetBytes(plainText);
PasswordDeriveBytes password = new PasswordDeriveBytes(passPhrase, null);
byte[] keyBytes = password.GetBytes(keysize / 8);
RijndaelManaged symmetricKey = new RijndaelManaged();
symmetricKey.Mode = CipherMode.CBC;
ICryptoTransform encryptor = symmetricKey.CreateEncryptor(keyBytes, initVectorBytes);
MemoryStream memoryStream = new MemoryStream();
CryptoStream cryptoStream = new CryptoStream(memoryStream, encryptor, CryptoStreamMode.Write);
cryptoStream.Write(plainTextBytes, 0, plainTextBytes.Length);
cryptoStream.FlushFinalBlock();
byte[] cipherTextBytes = memoryStream.ToArray();
return Convert.ToBase64String(cipherTextBytes);
}
public static string Decrypt(string cipherText, string passPhrase)
{
byte[] cipherTextBytes = Convert.FromBase64String(cipherText);
PasswordDeriveBytes password = new PasswordDeriveBytes(passPhrase, null);
byte[] keyBytes = password.GetBytes(keysize / 8);
RijndaelManaged symmetricKey = new RijndaelManaged();
symmetricKey.Mode = CipherMode.CBC;
ICryptoTransform decryptor = symmetricKey.CreateDecryptor(keyBytes, initVectorBytes);
MemoryStream memoryStream = new MemoryStream(cipherTextBytes);
CryptoStream cryptoStream = new CryptoStream(memoryStream, decryptor, CryptoStreamMode.Read);
byte[] plainTextBytes = new byte[cipherTextBytes.Length];
int decryptedByteCount = cryptoStream.Read(plainTextBytes, 0, plainTextBytes.Length);
return Encoding.UTF8.GetString(plainTextBytes, 0, decryptedByteCount);
}
and this is my php code :
$iv = "1234567812345678";
$out = null;
$key = "sample";
foreach ($iv as $i) { $out .= chr(ord(substr($i,0,1))); }
$res = mcrypt_decrypt(MCRYPT_RIJNDAEL_256, $key, $string, MCRYPT_MODE_CBC, implode($out));
The keys are not the same. C# is extending the key with PasswordDeriveBytes which is a good method. PHP mcrypt is extending they key with nulls. You need the extended (256-bit) keys to be the same.
The padding is not the same. Unencrypted data needs to be a multiple of the block size (128-bits for AES) and if it isn't always that padding must to be added. C# is not specifying any padding and will expect the data to be a multiple of the block size (128-bits). PHP will by default add null padding which is non-standard and will not work for binary data. You need to add common padding, the standard is PKCS#7 (aka PKCS#5), See PKCS#7 padding. C# supports PKCS#5 but for mcrypt you will have to do it in your code (the mcrypt developers were Bozos and did not provide standard padding).
Rijndael supports multiple bock sizes, it is not clear what the C# default block size is. If what you want is AES (it should be) the block size needs to be 128-bits.
Given that the MSDN documentation does not specify defaults it is best to explicitly set the block size, key size, mode and padding.
Your PHP code will not run on PHP 5.6 as the key size is wrong, it must be 32 bytes.
Said that, on previous versions PHP was padding the key with \0's to reach the correct key length, but in C# you're creating derived bytes (what indeed is correct) to get enough bytes for your key, which ends in different keys used on C# and PHP.
As a proof, create a key with 32 bytes (32 chars) and use directly those 32 bytes as key, both in PHP and C#, in that way it should work.
But at the end you will need a common way to derive the bytes both on PHP and C# to finally have a consistent keying code, an example can be to use a SHA-256 hash to generate the key.
I am using a Java based configuration management tool called Zuul which supports encrypting sensitive configuration information using various encryption schemes.
I have configured it to use below scheme for my data
AES (Bouncy Castle)
Name: PBEWITHSHA256AND128BITAES-CBC-BC
Requirements: Bouncy Castle API and JCE Unlimited Strength Policy Files
Hashing Algorithm: SHA256
Hashing Iterations: 1000
Now when reading my configuration data back, I need to decrypt the information before I can use it and the documentation provides below information around this topic.
The encrypted values produced by Jasypt (and thus Zuul) are are prefixed with the salt (usually 8 or 16 bytes depending on the algorithm requirements). They are then Base64 encoded. Decrypting the results goes something like this:
Convert the Base64 string to bytes
Strip off the first 8 or 16 bytes as the salt
Keep the remaining bytes for the encrypted payload
Invoke the KDF function with the salt, iteration count and the password to create the secret key.
Use the secret key to decrypt the encrypted payload
More details here: Zull Encryption wiki
Based on above details, I have written below code (and my knowledge around security is very limited)
public static string Decrypt(string cipher, string password)
{
const int saltLength = 16;
const int iterations = 1000;
byte[] cipherBytes = Convert.FromBase64String(cipher);
byte[] saltBytes = cipherBytes.Take(saltLength).ToArray();
byte[] encryptedBytes = cipherBytes.Skip(saltLength).ToArray();
Rfc2898DeriveBytes key = new Rfc2898DeriveBytes(password, saltBytes, iterations);
byte[] keyBytes = key.GetBytes(16);
AesCryptoServiceProvider aesAlg = new AesCryptoServiceProvider();
aesAlg.KeySize = 256;
aesAlg.BlockSize = 128;
aesAlg.Key = key.GetBytes(aesAlg.KeySize / 8);
aesAlg.IV = key.GetBytes(aesAlg.BlockSize / 8);
ICryptoTransform decryptor = aesAlg.CreateDecryptor(aesAlg.Key, aesAlg.IV);
MemoryStream msDecrypt = new MemoryStream(encryptedBytes);
CryptoStream csDecrypt = new CryptoStream(msDecrypt, decryptor, CryptoStreamMode.Read);
StreamReader srDecrypt = new StreamReader(csDecrypt);
return srDecrypt.ReadToEnd();
}
I configured Zuul to use below password for the encryption
SimplePassword
And now I have an encrypted string given to me by Zuul and I need to decrypt it
p8C9hAHaoo0F25rMueT0+u0O6xYVpGIkjHmWqFJmTOvpV8+cipoDFIUnaOFF5ElQ
When I try to decrypt this string using above code, I get below exception
System.Security.Cryptography.CryptographicException : Padding is invalid and cannot be removed.
As I mentioned earlier, my knowledge around this topic is limited and I am not able to figure out if the information provided in the documentation is not enough, if I am doing something wrong while writing the decryption routine or should I be using bouncy castle for decryption as well.
Any help with this will be much appreciated.
According to Zuul documentation they are deriving both key and iv from the password/salt.
So you should derive 256+128 bits (i.e. 48 bytes), and use first 32 bytes as the key, and next 16 bytes as IV.
And this should be done in one operation, not as consequent calls to key.DeriveBytes.
I resorted to Bouncy Castle for decryption instead since that is used by Zuul as well.
Here is the code that works
public static string Decrypt(string cipher, string password)
{
const int saltLength = 16;
const int iterations = 1000;
const string algSpec = "AES/CBC/NoPadding";
const string algName = "PBEWITHSHA256AND128BITAES-CBC-BC";
byte[] cipherBytes = Convert.FromBase64String(cipher);
byte[] saltBytes = cipherBytes.Take(saltLength).ToArray();
byte[] encryptedBytes = cipherBytes.Skip(saltLength).ToArray();
char[] passwordChars = password.ToCharArray();
Asn1Encodable defParams = PbeUtilities.GenerateAlgorithmParameters(algName, saltBytes, iterations);
IWrapper wrapper = WrapperUtilities.GetWrapper(algSpec);
ICipherParameters parameters = PbeUtilities.GenerateCipherParameters(algName, passwordChars, defParams);
wrapper.Init(false, parameters);
byte[] keyText = wrapper.Unwrap(encryptedBytes, 0, encryptedBytes.Length);
return Encoding.Default.GetString(keyText);
}
I am trying to re-create this openssl command in C#:
openssl enc –e –aes-256-cbc –k SecretPhrase1234 –in profile.xml –out profile.cfg
This encrypted file will then be loaded by a device and the process is described as this:
A lower case –k precedes the secret key, which can be any plain text phrase and is used to generate a random 64-bit salt. Then, in combination with the secret specified with the –k argument, it derives a random 128-bit initial vector, and the actual 256-bit encryption key.
So, in my C# application I need to create a random 64 bit salt using my "SecretPhrase1234". Then I need to derive a 128 bit IV and a 256 bit key. The device already has the secret phrase loaded onto it.
Here is my code:
AesManaged aes = new AesManaged();
// Encrypt the string to an array of bytes.
aes.KeySize = 256;
aes.BlockSize = 128;
aes.Mode = CipherMode.CBC;
Rfc2898DeriveBytes rfc = new Rfc2898DeriveBytes("SecretPhrase1234", 8);
byte[] SALT = rfc.Salt;
PasswordDeriveBytes pdb = new PasswordDeriveBytes("SecretPhrase1234", SALT);
byte[] IV = rfc.GetBytes(aes.BlockSize/8);
//The next line doesn't work
byte[] KEY = pdb.CryptDeriveKey("AES", "SHA1", aes.KeySize, IV);
aes.Key = KEY;
aes.IV = IV;
byte[] encrypted = AESEncryption.EncryptStringToBytes(plainConfig,
aes.Key, aes.IV);
tw.WriteLine(Encoding.ASCII.GetString(encrypted));
tw.Close();
I found a .NET implementation of OPENSSL which perfectly suits my needs. It is here:
openssl using only .NET classes