The class OSymCryptStream is a class template, using a FBB::CryptType template non-type parameter. Objects of the class FBB::OSymCryptStream<FBB::ENCRYPT> encrypt the information they receive, objects of the class FBB::OSymCryptStream<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 the currently supported cipher algorithms issue the command
openssl list -cipher-algorithms
OSymCryptStream objects read the information to en/decrypt from an external source (e.g., from std::istream objects). The characters that are encrypted or decrypted by OSymCryptStream objects are written to std::ostream objects which are at construction-time specified as ostream references or by filename.
- OSymCryptStream<FBB::ENCRYPT> objects perform encryption;
OSymCryptStream<FBB::DECRYPT> objects perform decryption;
- OSymCryptStream<CryptType> objects write the encrypted or decrypted
characters to outStream;
- 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::OSymCryptStreambuf internally used buffer will hold
inBufSize characters. The default value is the smallest value that
is used. When specifying a smaller bufSize value 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::ostream, all std::ostream members can be used.
The latter two functions throw exceptions if cipherName does not contain the name of a supported cipher algorithm.
//in.seekg(0); // when activated, this won't
//enc << in.rdbuf(); // be processed due to '<< eoi'
Activating those lines will not result in processing the in stream
twice.
#include <iostream>
#include <fstream>
#include <string>
#include <bobcat/osymcryptstream>
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";
cout << "encryption key ? ";
cin >> key;
while (key.size() < 32)
key += key;
string iv = " 0123456789ab" "456";
char cipherName[] =
"AES-256-GCM"
//"AES-256-CBC"
;
ifstream in{ argv[2] };
ofstream out{ argv[3] };
if (*argv[1] == 'e')
{
OSymCryptStream<ENCRYPT> enc{ out, cipherName, key, iv, 100 };
// comment out the above statement and uncomment the next
// to use the constructor expecting a string as 1st arg:
// OSymCryptStream<ENCRYPT> enc{ argv[3], cipherName, key,
// iv, 100 };
enc << in.rdbuf() << eoi;
//in.seekg(0); // when activated, this won't
//enc << in.rdbuf(); // be processed due to '<< eoi'
}
else
{
OSymCryptStream<DECRYPT> decrypt{ out, cipherName, key,
iv, 100 };
// comment out the above statement and uncomment the next
// to use the constructor expecting a string as 1st arg:
// OSymCryptStream<DECRYPT> decrypt{ argv[3], cipherName, key,
// iv, 100 };
decrypt << in.rdbuf() << eoi;
}
}
catch (exception const &exc)
{
cerr << exc.what() << '\n';
}