OpenPGP in C++

Copyright (c) 2013 - 2019 Jason Lee @ calccrypto at gmail.com

Please see LICENSE file for the license.

Also:

• contrib/cmake/FindGMP.cmake is by Jack Poulson from Elemental and is licened under the BSD License. It was changed slightly to remove a debug message.
• Some of CMakeLists.txt was taken from the Kitware CMake wiki RPath handling page.
• The code for incorporating Google Test into CMake was taken from the Google Test README, and modified slightly.

With much help from

• Alex Stapleton (OpenPGP-SDK)
• Auston Sterling - Massive amounts of debugging and programming help
• D-o-c - Key merging and elliptic curve parsing
• GeorgeKalovyrnas - Got me to rewrite S2K3::run that solves 2 problems at once (#44)
• Herbert Hanewinkel (hanewin.net)
• Jon Callas (RFC 4880)
• kaie - Found lots of bugs that were caused by knowledge gaps (#43)
• Many people on the StackExchange network
• mugwort-rc - Tons of testing code, code style updates, and bugfixes
• pgpdump.net
• PortablePGP

IMPORTANT

This library was not written for actual use.

Rather, it was meant for learning about the internals of PGP can easily use/add a few std::couts to see the internal workings.

So if you choose to use it in a real setting where secrecy is required, do so at your own risk.

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This is a C++ implementation of the majority of RFC 4880, the OpenPGP Message Format.

The purpose of this library is to help clear up the mess that is RFC 4880. It is extremely vague at best, and it took me a long time to figure out most of it. No one should have to go through that.

This library allows for the modification of PGP packets, such as providing incorrect checksums and public key values. That was done on purpose. I used it to test keys I created with known working values. What others do with this capability is none of my concern or responsibility.

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Building

Tools

• A C++ compiler with C++11 support
• CMake 3.6+

Libraries

• GMP (https://gmplib.org/)
• bzip2 (http://www.bzip.org/)
• zlib (http://www.zlib.net/)
• OpenSSL (https://www.openssl.org/) (optional)

Build

mkdir build
cd build
cmake ..
make
<make test>
make install

CMake Configuration Options

The boolean GPG_COMPATIBLE flag can be used to make this library gpg compatible when gpg does not follow the standard. By default this is set to False.

The boolean USE_OPENSSL flag can be used to replace the hashing and random number generation code with OpenSSL implementations. USE_OPENSSL_HASH and USE_OPENSSL_RNG can be used to independently replace the hashing or the random number generator. If OpenSSL is not found, CMake will default back to the original implementation. All three are disabled by default.

Usage

This library should be relatively straightforward to use: Simply #include "OpenPGP.h".

If you do not wish to include everything at once, #include whatever functions are needed:

Feature	Header	Namespace
key generation	keygen.h	OpenPGP::KeyGen
key revocation	revoke.h	OpenPGP::Revoke
encrypt	encrypt.h	OpenPGP::Encrypt
decrypt	decrypt.h	OpenPGP::Decrypt
sign	sign.h	OpenPGP::Sign
verify	verify.h	OpenPGP::Verify

Multiple classes inherit from the abstract base class PGP in order to make differentiating PGP block types better in code:

PGP block type	Description
DetachedSignature	detached signatures for files
Key	base class for OpenPGP key types
PublicKey	holds public keys; inherits Key
SecretKey	holds private keys; inherits Key
Message	holds OpenPGP Messages
RevocationCertificate	holds revocation certificates

All these different types are able to read in any PGP data, but will cause problems when used. The meaningful function in these PGP objects is provided to make sure that the packet sequence contained is meaningful.

CleartextSignature does not inherit from PGP and cannot read non-Cleartext Signature data.

All data structures have some standard functions:

Function	Description
read	reads data without the header information
show	displays the data in human readable form like the way pgpdump.net does it.
raw	returns a string of packet data without the header information
write	returns a string of the entire data, including the header.
clone	returns a pointer to a deep copy of the object (mainly used for moving PGP data around).
Ptr	a typedef for std::shared_ptr<T> for the class where the typedef is found.

operator= and the copy constructor have been overloaded for the data structures that need deep copy.

Command Line Interface

The cli/main.cpp file provides a simple command line tool that uses modules from the cli/modules directory to provide functionality. These can be used as examples on how to use the functions. A lot of the output was based on/inspired by pgpdump.net and GPG.

Note: Keyrings were not implemented. Rather, individual keys are read from the directory used as arguments to functions.