oracular (3) osymcryptstreambuf.3bobcat.gz
NAME
FBB::OSymCryptStreambuf - std::streambuf performing symmetric en/decryption
SYNOPSIS
#include <bobcat/osymcryptstreambuf>
Linking option: -lbobcat -lcrypto
DESCRIPTION
FBB::OSymCryptStreambuf objects can be used as std::streambuf objects of std::ostream objects, and
encrypt or decrypt information, that is made available via separate std::istream streams.
The class OSymCryptStreambuf is a class template, using a FBB::CryptType template non-type parameter.
Objects of the class FBB::OSymCryptStreambuf<FBB::ENCRYPT> encrypt the information they receive, objects
of the class FBB::OSymCryptStreambuf<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
OSymCryptStreambuf 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 OSymCryptStreambuf 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::OSymCryptBase (public)
The class FBB::OSymCryptBase is an `internal use only’ class, derived from std::streambuf, and therefore
OSymCryptStreambuf is a std::streambuf class.
CONSTRUCTORS
o OSymCryptStreambuf<CryptType>(std::ostream &outStreambuf, 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.
- OSymCryptStreambuf<FBB::ENCRYPT> objects perform encryption;
OSymCryptStreambuf<FBB::DECRYPT> objects perform decryption;
- OSymCryptStreambuf<CryptType> objects write the encrypted or decrypted characters to
outStreambuf;
- 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::OSymCryptStreambufbuf 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 OSymCryptStreambuf<CryptType>(std::string const &outStreambufName, 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::streambuf 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 std::ostream object that uses a OSymCryptStreambuf
streambuf insertion is considered complete. It completes the insertion of information into the
std::ostream specified at construction time as the OSymCryptStreambuf’s first argument. That way,
you don’t have to wait until the OSymCryptStreambuf object’s destructor flushes that stream. The
example provided at the osymcryptstream(3bobcat) man-page illustrates the use of the eoi
manipulator.
EXAMPLE
See the example in the osymcryptstream(3bobcat) man-page. Instead of defining an OSymCryptStream an OSymCryptStreamBuf can be defined, passing its address to a std::ostream which can then be used as the OSymCryptStream used in the example.
FILES
bobcat/osymcryptstreambuf - defines the class interface
SEE ALSO
bobcat(7), isymcryptstream(3bobcat), isymcryptstreambuf(3bobcat), osymcryptstream(3bobcat)
BUGS
None Reported.
BOBCAT PROJECT FILES
o https://fbb-git.gitlab.io/bobcat/: gitlab project page;
o bobcat_6.06.01-x.dsc: detached signature;
o bobcat_6.06.01-x.tar.gz: source archive;
o bobcat_6.06.01-x_i386.changes: change log;
o libbobcat1_6.06.01-x_*.deb: debian package containing the libraries;
o libbobcat1-dev_6.06.01-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).