我正在尝试使用crypto++库执行AES解密。我有一个加密的文件，其前8个字节为文件长度，后16个字节为初始化向量，其余数据为感兴趣的数据。我也有密钥的字符串表示形式（我使用SHA256对其进行哈希处理）
尝试执行AES解密时出现以下错误：
StreamTransformationFilter: invalid PKCS #7 block padding found
我正在使用以下c ++代码：
std::string keyStr = "my_key";
std::string infilePath = "my/file/path";
CryptoPP::SHA256 hash;
unsigned char digest[CryptoPP::SHA256::DIGESTSIZE];
hash.CalculateDigest( digest, reinterpret_cast<const unsigned char*>(&keyStr[0]), keyStr.length() );
auto key = CryptoPP::SecByteBlock(digest, CryptoPP::SHA256::DIGESTSIZE);
std::ifstream fin(infilePath, std::ifstream::binary);
// First 8 bytes is the file size
std::vector<char> fileSizeVec(8);
fin.read(fileSizeVec.data(), fileSizeVec.size());
// Read the next 16 bytes to get the initialization vector
std::vector<char> ivBuffer(16);
fin.read(ivBuffer.data(), ivBuffer.size());
CryptoPP::SecByteBlock iv(reinterpret_cast<const unsigned char*>(ivBuffer.data()), ivBuffer.size());
// Create a CBC decryptor
CryptoPP::CBC_Mode<CryptoPP::AES>::Decryption decryption;
decryption.SetKeyWithIV(key, sizeof(key), iv);
CryptoPP::StreamTransformationFilter decryptor(decryption);
std::vector<char> buffer(CHUNK_SIZE, 0);
while(fin.read(buffer.data(), buffer.size())) {
CryptoPP::SecByteBlock tmp(reinterpret_cast<const unsigned char*>(buffer.data()), buffer.size());
decryptor.Put(tmp, tmp.size());
}
decryptor.MessageEnd();
size_t retSize = decryptor.MaxRetrievable();
std::vector<char> decryptedBuff;
decryptedBuff.resize(retSize);
decryptor.Get(reinterpret_cast<CryptoPP::byte*>(decryptedBuff.data()), decryptedBuff.size());
我不确定是什么给了我错误。我正在处理以下python代码。当我使用相同的输入文件运行python代码时，它会成功解密该文件。
def decrypt_file(in_filename, out_filename=None):
key = hashlib.sha256(PASSWORD).digest()
"""loads and returns the embedded model"""
chunksize = 24 * 1024
if not out_filename:
out_filename = os.path.splitext(in_filename)[0]
with open(in_filename, 'rb') as infile:
# get the initial 8 bytes with file size
tmp = infile.read(8)
iv = infile.read(16)
decryptor = AES.new(key, AES.MODE_CBC, iv)
string = b''
# with open(out_filename, 'wb') as outfile:
while True:
chunk = infile.read(chunksize)
if len(chunk) == 0:
break
string += decryptor.decrypt(chunk)
return string
除了解决错误外，我还喜欢一些关于如何改进的通用c ++编码反馈。
谢谢！
编辑：
好像我没有一直读完输入文件（因为最后一块的长度小于CHUNK_SIZE）。现在，以下代码读取了整个文件，但是仍然出现相同的问题。我还确认了IV和key与python代码产生的结果完全匹配。
// Get the length of the file in bytes
fin.seekg (0, fin.end);
size_t fileLen = fin.tellg();
fin.seekg (0, fin.beg);
std::vector<char> buffer(CHUNK_SIZE, 0);
size_t readSize = CHUNK_SIZE;
while(fin.read(buffer.data(), readSize)) {
CryptoPP::SecByteBlock tmp(reinterpret_cast<const unsigned char*>(buffer.data()), CHUNK_SIZE);
decryptor.Put(tmp, tmp.size());
std::fill(buffer.begin(), buffer.end(), 0);
size_t bytesReamining = fileLen - fin.tellg();
readSize = CHUNK_SIZE < bytesReamining ? CHUNK_SIZE : bytesReamining;
if (!readSize)
break;
}
}
请注意，我同时以CryptoPP::SecByteBlock tmp(reinterpret_cast<const unsigned char*>(buffer.data()), CHUNK_SIZE);
和CryptoPP::SecByteBlock tmp(reinterpret_cast<const unsigned char*>(buffer.data()), readSize);（将CHUNK_SIZE垫与0一起使用）
答案 0 :(得分：1)
我有一个加密的文件，其前8个字节为文件长度，后16个字节为初始化向量，其余数据为感兴趣的数据...
我想我会简单地介绍一下，并向您展示一种使用Crypto ++库做事的简便方法。键和iv进行了硬编码以简化代码。该示例不需要推导。顺便说一句，如果Python拥有它，则应考虑使用HKDF来推导AES密钥和iv。 HKDF具有可证明的安全性。
Crypto ++为您处理分块。您不需要显式执行它；请参阅Crypto ++ Wiki上的Pumping Data。
我认为，由于使用了没有MAC的CBC模式，Python代码中存在潜在的填充预言。您可能会考虑添加MAC或使用Authenticated Encryption操作模式。
#include "cryptlib.h"
#include "filters.h"
#include "osrng.h"
#include "modes.h"
#include "files.h"
#include "aes.h"
#include "hex.h"
#include <string>
#include <iostream>
const std::string infilePath = "test.dat";
int main(int argc, char* argv[])
{
using namespace CryptoPP;
const byte key[16] = {
1,2,3,4, 1,2,3,4, 1,2,3,4, 1,2,3,4
};
const byte iv[16] = {
8,7,6,5, 8,7,6,5, 8,7,6,5, 8,7,6,5
};
const byte data[] = // 70 characters
"Now is the time for all good men to come to the aide of their country.";
HexEncoder encoder(new FileSink(std::cout));
std::string message;
// Show parameters
{
std::cout << "Key: ";
StringSource(key, 16, true, new Redirector(encoder));
std::cout << std::endl;
std::cout << "IV: ";
StringSource(iv, 16, true, new Redirector(encoder));
std::cout << std::endl;
std::cout << "Data: ";
StringSource(data, 70, true, new Redirector(encoder));
std::cout << std::endl;
}
// Write sample data
{
FileSink outFile(infilePath.c_str());
word64 length = 8+16+70;
outFile.PutWord64(length, BIG_ENDIAN_ORDER);
outFile.Put(iv, 16);
CBC_Mode<AES>::Encryption enc;
enc.SetKeyWithIV(key, 16, iv, 16);
StringSource(data, 70, true, new StreamTransformationFilter(enc, new Redirector(outFile)));
}
// Read sample data
{
FileSource inFile(infilePath.c_str(), true /*pumpAll*/);
word64 read, l;
read = inFile.GetWord64(l, BIG_ENDIAN_ORDER);
if (read != 8)
throw std::runtime_error("Failed to read length");
SecByteBlock v(16);
read = inFile.Get(v, 16);
if (read != 16)
throw std::runtime_error("Failed to read iv");
CBC_Mode<AES>::Decryption dec;
dec.SetKeyWithIV(key, 16, v, 16);
SecByteBlock d(l-8-16);
StreamTransformationFilter f(dec, new ArraySink(d, d.size()));
inFile.CopyTo(f);
f.MessageEnd();
std::cout << "Key: ";
StringSource(key, 16, true, new Redirector(encoder));
std::cout << std::endl;
std::cout << "IV: ";
StringSource(v, 16, true, new Redirector(encoder));
std::cout << std::endl;
std::cout << "Data: ";
StringSource(d, d.size(), true, new Redirector(encoder));
std::cout << std::endl;
message.assign(reinterpret_cast<const char*>(d.data()), d.size());
}
std::cout << "Message: ";
std::cout << message << std::endl;
return 0;
}
运行程序会导致：
$ g++ test.cxx ./libcryptopp.a -o test.exe
$ ./test.exe
Key: 01020304010203040102030401020304
IV: 08070605080706050807060508070605
Data: 4E6F77206973207468652074696D6520666F7220616C6C20676F6F64206D656E20746F2063
6F6D6520746F207468652061696465206F6620746865697220636F756E7472792E
Key: 01020304010203040102030401020304
IV: 08070605080706050807060508070605
Data: 4E6F77206973207468652074696D6520666F7220616C6C20676F6F64206D656E20746F2063
6F6D6520746F207468652061696465206F6620746865697220636F756E7472792E
Message: Now is the time for all good men to come to the aide of their country.
在此堆栈溢出问题之前，Crypto ++库未提供PutWord64和GetWord64。与Python之类的库进行互操作对项目很重要，因此在Commit 6d69043403a9和Commit 8260dd1e81c3处添加了它们。它们将成为Crypto ++ 8.3版本的一部分。
如果您使用的是Crypto ++ 8.2或更低版本，则可以使用以下代码执行64位读取。
word64 length;
word32 h, l;
inFile.GetWord32(h, BIG_ENDIAN_ORDER);
inFile.GetWord32(l, BIG_ENDIAN_ORDER);
length = ((word64)h << 32) | l;
这是此示例中使用的数据文件。
$ hexdump -C test.dat
00000000 00 00 00 00 00 00 00 5e 08 07 06 05 08 07 06 05 |.......^........|
00000010 08 07 06 05 08 07 06 05 b0 82 79 ee a6 d8 8a 0e |..........y.....|
00000020 a6 b3 a4 7e 63 bd 9a bc 0e e4 b6 be 3e eb 36 64 |...~c.......>.6d|
00000030 72 cd ba 91 8d e0 d3 c5 cd 64 ae c0 51 de a7 c9 |r........d..Q...|
00000040 1e a8 81 6d c0 d5 42 2a 17 5a 19 62 1e 9c ab fd |...m..B*.Z.b....|
00000050 21 3d b0 8f e2 b3 7a d4 08 8d ec 00 e0 1e 5e 78 |!=....z.......^x|
00000060 56 6d f5 3e 8c 5f fe 54 |Vm.>._.T|
答案 1 :(得分：0)
看起来该问题与填充有关。相反，我改用了StringSource，只有在我将CryptoPP::BlockPaddingSchemeDef::BlockPaddingScheme::ZEROS_PADDING指定为StreamTransformationFilter
这是任何有兴趣的人的工作代码：
void Crypto::decryptFileAES(CryptoPP::SecByteBlock key, std::string infilePath) {
std::ifstream fin(infilePath, std::ifstream::binary);
// Get the length of the file in bytes
fin.seekg (0, fin.end);
size_t fileLen = fin.tellg();
fin.seekg (0, fin.beg);
// First 8 bytes is the file size
std::vector<char> fileSizeVec(8);
fin.read(fileSizeVec.data(), fileSizeVec.size());
// Read the first 16 bytes to get the initialization vector
std::vector<char> ivBuffer(16);
fin.read(ivBuffer.data(), ivBuffer.size());
CryptoPP::SecByteBlock iv(reinterpret_cast<const unsigned char*>(ivBuffer.data()), ivBuffer.size());
// Create a CBC decryptor
CryptoPP::CBC_Mode<CryptoPP::AES>::Decryption decryption;
decryption.SetKeyWithIV(key, sizeof(key), iv);
size_t bytesReamining = fileLen - fin.tellg();
std::vector<char> buffer(bytesReamining);
if(!fin.read(buffer.data(), bytesReamining)) {
throw std::runtime_error("Unable to read file");
}
std::string decryptedText;
CryptoPP::StringSource ss(reinterpret_cast<const unsigned char*>(buffer.data()), buffer.size(), true,
new CryptoPP::StreamTransformationFilter(decryption,
new CryptoPP::StringSink(decryptedText), CryptoPP::BlockPaddingSchemeDef::BlockPaddingScheme::ZEROS_PADDING));
std::cout << decryptedText << std::endl;
}