The class ISymCryptStream is a class template, using a FBB::CryptType template non-type parameter. Objects of the class FBB::ISymCryptStream<FBB::ENCRYPT> encrypt the information they receive, objects of the class FBB::ISymCryptStream<FBB::DECRYPT> decrypt the information they receive.
All symmetric encryption methods defined by the OpenSSL library that can be selected by name may be used to en/decrypt information. To select a particular encryption method an identifier is passed to the constructor. E.g., "aes-256-gcm". For an overview of the currently supported cipher algorithms issue the command
openssl list -cipher-algorithms
ISymCryptStream objects read the information to en/decrypt from std::istream objects, which are at construction-time specified as istream references or by filename. The characters that are thereupon extracted or read from ISymCryptStream objects are en/decrypted, and could, e.g., be written to some output stream.
- ISymCryptStream<FBB::ENCRYPT> objects perform encryption;
ISymCryptStream<FBB::DECRYPT> objects perform decryption;
- ISymCryptStream<CryptType> objects receive the characters to encrypt
or decrypt from inStream;
- The encryption method to use is specified by the cipherName
parameter. E.g., "AES-256-GCM";
- The symmetric key to use is specified by the key parameter;
- The initialization vector is specified by the iv parameter;
- The FBB::ISymCryptStreambuf internally used buffer will hold
inBufSize characters. The default value is the smallest value that
is used. When specifying a smaller bufSize value than the default
value then the default value is used;
If the construction fails an exception is thrown, mentioning the openssl function that failed to complete (see also errorMsg below).
The move constructor is available, the copy constructor and assignment operators are not available,
Since the class is publicly derived from std::istream, all std::istream members can be used.
The latter two functions throw exceptions if cipherName does not contain the name of a supported cipher algorithm.
#include <iostream>
#include <fstream>
#include <string>
#include <bobcat/isymcryptstream>
#include <bobcat/isymcryptstreambuf>
using namespace std;
using namespace FBB;
int main(int argc, char **argv)
try
{
if (argc == 1)
{
cout << "arg[1]: e - encrypt, d - decrypt,\n"
"arg[2]: file to process, arg[3]: processed file\n";
return 0;
}
string key = "0123456789abcdef0123456789abcdef";
string iv = " 0123456789ab" "456";
char cipherName[] =
"AES-256-GCM"
//"AES-256-CBC"
;
ifstream in = Exception::factory<ifstream>(argv[2]);
ofstream out{ argv[3] };
ISymCryptStreambuf<ENCRYPT> encbuf{ in, cipherName, key, iv, 100 };
if (*argv[1] == 'e')
{
ISymCryptStream<ENCRYPT> enc{ in, cipherName, key, iv, 100 };
// comment out the previous line and uncomment the next
// to use the constructor expecting a string as 1st arg:
// ISymCryptStream<ENCRYPT> enc{ argv[2], cipherName, key,
// iv, 100};
out << enc.rdbuf();
}
else
{
ISymCryptStream<DECRYPT> decrypt{ in, cipherName, key, iv, 100 };
// comment out the previous line and uncomment the next
// to use the constructor expecting a string as 1st arg:
// ISymCryptStream<DECRYPT> decrypt{ argv[2], cipherName, key,
// iv, 100 };
out << decrypt.rdbuf();
}
}
catch (exception const &exc)
{
cerr << exc.what() << '\n';
}