c++ - StreamTransformationFilter: invalid PKCS #7 block padding found in AES decryption

Question

I want to use AES-256 encryption/decryption in my C++ code to do that I use cryptoPP library, I have implement encryption and decryption. but I get Error : StreamTransformationFilter: invalid PKCS #7 block padding found Error.

The senario which I test is :

First I encrypt myplaintext then decrypt it --> there is no error here.

Second I decrypt the cipher created above --> here I got the error.

I know that there are same question here but I couldn't solve my problem :(

Here I set iv:

byte iv[16];
string strIv = "162169848599E7C792BF58BFA53D88E6";
memcpy(iv, strIv.data(), strIv.length());

Encryption:

string CryptoAES::Encrypt(string plain, string strkey) {
    cout << "
plain text :" << plain;
    cout << "
 key to encrypt: " <<strkey;
    byte key[AES::MAX_KEYLENGTH];
    memcpy(key, strkey.data(), strkey.length());
    string encodedKey, decodedKey,ciphertextEncode,ciphertext;
    encodedKey.clear();
    decodedKey.clear();
    ciphertextEncode.clear();
    ciphertext.clear();
    StringSource(key, sizeof (key), true, new HexEncoder(new StringSink(encodedKey))); 
    StringSource ssk(encodedKey, true, new HexDecoder(new StringSink(decodedKey)));
    memcpy(key, decodedKey.data(), decodedKey.length());
    CryptoPP::AES::Encryption aesEncryption(key, AES::MAX_KEYLENGTH);
    CryptoPP::CBC_Mode_ExternalCipher::Encryption cbcEncryption(aesEncryption, iv);

    CryptoPP::StreamTransformationFilter stfEncryptor(cbcEncryption, new CryptoPP::StringSink(ciphertext));
    stfEncryptor.Put(reinterpret_cast<const unsigned char*> (plain.c_str()), plain.length() + 1);
    stfEncryptor.MessageEnd();
    StringSource ss(ciphertext, true, new HexEncoder(new StringSink(ciphertextEncode)));
    cout << "
encrypted text: " <<ciphertextEncode;
    return ciphertextEncode;
}

Decryption:

string CryptoAES::Decrypt(string cipher, string strkey) {
    cout <<"
cipher text : "<< cipher;
    cout << "
 key to decrypt: " <<strkey;
    byte key[AES::MAX_KEYLENGTH];
    memcpy(key, strkey.data(), strkey.length());
    string encodedKey, decodedKey,ciphertextDecode,decryptedtext;
    encodedKey.clear();
    decodedKey.clear();
    ciphertextDecode.clear();
    decryptedtext.clear();
    StringSource(key, sizeof (key), true, new HexEncoder(new StringSink(encodedKey))); 
    StringSource ssk(encodedKey, true, new HexDecoder(new StringSink(decodedKey)));
    memcpy(key, decodedKey.data(), decodedKey.length());
    StringSource ss(cipher, true, new HexDecoder(new StringSink(ciphertextDecode)));
    CryptoPP::AES::Decryption aesDecryption(key, AES::MAX_KEYLENGTH);
    CryptoPP::CBC_Mode_ExternalCipher::Decryption cbcDecryption(aesDecryption, iv);

    CryptoPP::StreamTransformationFilter stfDecryptor(cbcDecryption, new CryptoPP::StringSink(decryptedtext));
    stfDecryptor.Put(reinterpret_cast<const unsigned char*> (ciphertextDecode.c_str()), ciphertextDecode.size());
    stfDecryptor.MessageEnd();

    cout <<"
decrypted text: "<<decryptedtext;
    return decryptedtext;
}

result :

plain text :F7ACA191B43AFAF85277DD196FE0441CB7C0901BEC33CB9F38FFAA54CBF219B9
 key to encrypt: 123456
encrypted text: 6FC1BF3108B0590367E6449B6E615CACFDF4DE16EDD05742C873EE4E8A16BA9EC0B8EFAD800F466EE9A6F75202C8800CF4CBDD2620956020D5B0A6A9A8DCEA9EDB5C470527423ACBEEDD0A9C59916C8B
cipher text : 6FC1BF3108B0590367E6449B6E615CACFDF4DE16EDD05742C873EE4E8A16BA9EC0B8EFAD800F466EE9A6F75202C8800CF4CBDD2620956020D5B0A6A9A8DCEA9EDB5C470527423ACBEEDD0A9C59916C8B
 key to decrypt: 123456
decrypted text: F7ACA191B43AFAF85277DD196FE0441CB7C0901BEC33CB9F38FFAA54CBF219B9
cipher text : 6FC1BF3108B0590367E6449B6E615CACFDF4DE16EDD05742C873EE4E8A16BA9EC0B8EFAD800F466EE9A6F75202C8800CF4CBDD2620956020D5B0A6A9A8DCEA9EDB5C470527423ACBEEDD0A9C59916C8B                                                                                                    
 key to decrypt: 123456
exception in proxy server! :( 
    Error : StreamTransformationFilter: invalid PKCS #7 block padding found

EDIT #1: here is the new version of the methods:

IV:

for (int i = 0; i < AES::BLOCKSIZE; i++)
        iv[i] = 0;

encryption:

string CryptoAES::Encrypt(string plain, string strkey) {

    byte key[AES::MAX_KEYLENGTH];
    byte* k = (byte*) strkey.c_str();

    for (int i = 0; i < AES::MAX_KEYLENGTH; i++)
        if (i<sizeof (k))
            key[i] = k[i];
        else
            key[i] = 0;
    string ciphertextEncode,ciphertext;
    cout << "
plain text :" << plain;
    cout << "
 key to encrypt: " <<key;
    ciphertextEncode.clear();
    ciphertext.clear();
    CryptoPP::AES::Encryption aesEncryption(key, AES::MAX_KEYLENGTH);
    CryptoPP::CBC_Mode_ExternalCipher::Encryption cbcEncryption(aesEncryption, iv);

    CryptoPP::StreamTransformationFilter stfEncryptor(cbcEncryption, new CryptoPP::StringSink(ciphertext));
    stfEncryptor.Put(reinterpret_cast<const unsigned char*> (plain.c_str()), plain.length() + 1);
    stfEncryptor.MessageEnd();
    cout << "
encrypted text: " <<ciphertext;
    StringSource ss(ciphertext, true, new HexEncoder(new StringSink(ciphertextEncode)));
    cout << "
encoded encrypted text: " <<ciphertextEncode;
    return ciphertextEncode;
}

Decryption:

string CryptoAES::Decrypt(string cipher, string strkey) {

    byte key[AES::MAX_KEYLENGTH];
    byte* k = (byte*) strkey.c_str();

    for (int i = 0; i < AES::MAX_KEYLENGTH; i++)
        if (i<sizeof (k))
            key[i] = k[i];
        else
            key[i] = 0;
    string ciphertextDecode,decryptedtext;
    cout <<"
cipher text : "<< cipher;
    cout << "
 key to decrypt: " <<key;
    ciphertextDecode.clear();
    decryptedtext.clear();

    StringSource ss(cipher, true, new HexDecoder(new StringSink(ciphertextDecode)));
    cout << "
 cipher decoded: " << ciphertextDecode;
    CryptoPP::AES::Decryption aesDecryption(key, AES::MAX_KEYLENGTH);
    CryptoPP::CBC_Mode_ExternalCipher::Decryption cbcDecryption(aesDecryption, iv);

    CryptoPP::StreamTransformationFilter stfDecryptor(cbcDecryption, new CryptoPP::StringSink(decryptedtext));
    stfDecryptor.Put(reinterpret_cast<const unsigned char*> (ciphertextDecode.c_str()), ciphertextDecode.size());
    stfDecryptor.MessageEnd();

    cout <<"
decrypted text: "<<decryptedtext;
    return decryptedtext;
}

result:

plain text :0C469BEA09DFCAC0A555E74175F1A614F471A5205FEB13A72C2DFFE8C4B52AA4
 key to encrypt: 123456
encrypted text: ?????z?????_???d?0?k????^G?o???zL??Z??fc?L??X???,<X*-R_??x????  ?U$?
encoded encrypted text: D8F68E8E8B7AADB094A5BD5FC117BFBA648130E46BDFA8B6DD0EA35E17478F6FA01AA38E0417B4087A4CAEBB5AB8C466639C4C84F35895C07FB2172C3C582A2D525FFDDC78A9F83FEFA50913E55524C1
cipher text : D8F68E8E8B7AADB094A5BD5FC117BFBA648130E46BDFA8B6DD0EA35E17478F6FA01AA38E0417B4087A4CAEBB5AB8C466639C4C84F35895C07FB2172C3C582A2D525FFDDC78A9F83FEFA50913E55524C1
 key to decrypt: 123456
 cipher decoded: ?????z?????_???d?0?k????^G?o???zL??Z??fc?L??X???,<X*-R_??x???? ?U$?
decrypted text: 0C469BEA09DFCAC0A555E74175F1A614F471A5205FEB13A72C2DFFE8C4B52AA4
cipher text : D8F68E8E8B7AADB094A5BD5FC117BFBA648130E46BDFA8B6DD0EA35E17478F6FA01AA38E0417B4087A4CAEBB5AB8C466639C4C84F35895C07FB2172C3C582A2D525FFDDC78A9F83FEFA50913E55524C1                                                                                               
 key to decrypt: 123456
 cipher decoded: ?????z?????_???d?0?k????^G?o???zL??Z??fc?L??X???,<X*-R_??x???? ?U$?
exception in proxy server! :( 
    StreamTransformationFilter: invalid PKCS #7 block padding found

Answer 1

Finally I solved the problems.

first:

string cipher and string strkey have padding.

second:

The iv[16] value which was share between two methods, is changed! so I set it in each methods.