Provided by: libbobcat-dev_6.03.02-2_amd64 
NAME
FBB::OSymCryptStream - std::ostream performing symmetric en/decryption
SYNOPSIS
#include <bobcat/osymcryptstream>
Linking option: -lbobcat -lcrypto
DESCRIPTION
FBB::OSymCryptStream objects can be used to encrypt or decrypt information, that is
available on separate std::istream streams.
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.
NAMESPACE
FBB
All constructors, members, operators and manipulators, mentioned in this man-page, are
defined in the namespace FBB.
INHERITS FROM
FBB::OSymCryptStreambuf (private),
std::istream
CONSTRUCTORS
o OSymCryptStream<CryptType>(std::ostream &outStream, std::string const &cipherName,
std::string const &key, std::string const &iv, size_t inBufSize = 100):
This constructor defines a std::streambuf encrypting or decrypting the characters
it receives.
- 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;
o OSymCryptStream<CryptType>(std::string const &outStreamName, std::string const
&cipherName, std::string const &key, std::string const &iv, size_t inBufSize =
100):
Same constructor as the previous one, but this constructor’s first parameter
specifies the name of the file to receive the encrypted or decrypted characters.
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,
INHERITED MEMBERS
Since the class is publicly derived from std::ostream, all std::ostream members can be
used.
MEMBER FUNCTIONS
o static std::string errorMsg():
If an openssl function fails an exception is thrown mentioning the name of the
failing function. In those cases the function errorMsg can be called returning a
std::string containing the openssl error code (returned by ERR_get_error) and its
textual representation (returned by ERR_error_string). If the reported error code
is zero, then in fact no error has occurred and the exception was spuriously
reported;
o static size_t keyLength(std::string const &cipherName):
returns the minimum key length required for cipher cipherName;
o static size_t ivLength(std::sting const &cipherName):
returns the minimum length of the initialization vector that is required for cipher
cipherName.
The latter two functions throw exceptions if cipherName does not contain the name of a
supported cipher algorithm.
MANIPULATOR
o std::ostream &FBB::eoi(std::ostream &out):
By inserting the eoi manipulator into an OSymCryptStream object insertion is
considered complete. It completes the insertion of information into the
std::ostream specified at construction time as the OSymCryptStream’s first
argument. That way, you don’t have to wait until the OSymCryptStream object’s
destructor flushes that stream. In the following example using the eoi manipulator
is illustrated in the (commented out lines near line 40):
//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.
EXAMPLE
#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’;
}
FILES
bobcat/osymcryptstream - defines the class interface
SEE ALSO
bobcat(7), isymcryptstream(3bobcat), isymcryptstreambuf(3bobcat),
osymcryptstreambuf(3bobcat)
BUGS
None Reported.
BOBCAT PROJECT FILES
o https://fbb-git.gitlab.io/bobcat/: gitlab project page;
o bobcat_6.03.02-x.dsc: detached signature;
o bobcat_6.03.02-x.tar.gz: source archive;
o bobcat_6.03.02-x_i386.changes: change log;
o libbobcat1_6.03.02-x_*.deb: debian package containing the libraries;
o libbobcat1-dev_6.03.02-x_*.deb: debian package containing the libraries, headers
and manual pages;
BOBCAT
Bobcat is an acronym of `Brokken’s Own Base Classes And Templates’.
COPYRIGHT
This is free software, distributed under the terms of the GNU General Public License
(GPL).
AUTHOR
Frank B. Brokken (f.b.brokken@rug.nl).