generic CMP client

This is a generic Certificate Management Protocol (CMP) client library with a high-level API and associated CLI-based demo client, tests, and documentation.

Purpose

The purpose of this software is to provide a high-level API on top of the detailed CMP (and CRMF) API of OpenSSL since version 3.0. It can be used with OpenSSL and with the intermediate CMP library CMPforOpenSSL providing the latest CMP features defined in CMP Updates .

The high-level API is on the one hand convenient to use for application programmers and on the other hand complete and flexible enough to cover the major certificate management use cases. The library supports developing CMP clients that adhere to the Lightweight CMP Profile (LCMPP) , which is geared towards simple and interoperable industrial use. The software also provides a command-line interface (CLI) that is handy for interactive exploration of using CMP in a PKI.

Status and changelog

See the CHANGELOG.md file in the top-level directory.

Documentation

The Generic CMP client API specification and CLI documentation are available in the doc folder.

The Doxygen documentation of the underlying Security Utilities library is available via a link in its README file.

Prerequisites

This software should work with any flavor of Linux, including Cygwin, also on a virtual machine or the Windows Subsystem for Linux (WSL).

The following network and development tools are needed or recommended.

• Git (for getting the software, tested with versions 2.7.2, 2.11.0, 2.20, 2.30.2)
• CMake (for using CMakeLists.txt, tested with versions 3.18.4 and 3.26.3)
• GNU make (tested with versions 4.1, 4.2.1, 4.3)
• GNU C compiler (gcc, tested with versions 5.4.0, 7.3.0, 8.3.0, 10.0.1, 10.2.1)
• wget (for running the demo, tested with versions 1.17, 1.18, 1.20, 1.21)
• Perl (for running the tests, tested with version 5.32.1)

The following OSS components are used.

• OpenSSL development edition; supported versions: 1.1.1, 3.0, 3.1
• Security Utilities (libsecutils)
• CMPforOpenSSL, a CMP+CRMF+HTTP extension to OpenSSL, needed when using OpenSSL 1.x or if the latest CMP features not yet available in OpenSSL are required, which can be indicated by setting the environment variable USE_LIBCMP.

For instance, on a Debian system the prerequisites may be installed simply as follows:

sudo apt install cmake libssl-dev libc-dev linux-libc-dev

while apt install git make gcc wget usually is not needed as far as these tools are pre-installed.

As a sanity check you can execute in a shell:

git clone [email protected]:siemens/genCMPClient.git
cd genCMPClient
make -f OpenSSL_version.mk

This should output on the console something like

cc [...] OpenSSL_version.c -lcrypto -o OpenSSL_version
OpenSSL 3.0.8 7 Feb 2023 (0x30000080)

You might need to set the variable OPENSSL_DIR first as described below, e.g.,

export OPENSSL_DIR=/usr

Getting the software

For accessing the code repositories on GitHub you may need an SSH client with suitable credentials or an HTTP proxy set up, for instance:

export https_proxy=http://proxy.example.com:8080

You can clone the git repository and its submodules with

git clone [email protected]:siemens/genCMPClient.git
cd genCMPClient
make -f Makefile_v1 get_submodules  

This will fetch also the underlying CMPforOpenSSL extension to OpenSSL if needed and the Security Utilities (libsecutils) library.

For using the project as a git submodule, do for instance the following in the directory where you want to integrate it:

git submodule add [email protected]:siemens/gencmpclient.git

When you later want to update your local copy of all relevant repositories it is sufficient to invoke

make update

Configuring and building

The generic CMP client (as well as its underlying libraries) assumes that OpenSSL is already installed, including the C header files needed for development (as provided by, e.g., the Debian/Ubuntu package libssl-dev).

By default any OpenSSL installation available on the system is used. Set the optional environment variable OPENSSL_DIR to specify the absolute (or relative to ../) path of the OpenSSL installation to use, e.g.:

export OPENSSL_DIR=/usr

In case its libraries are in a different location, set also OPENSSL_LIB, e.g.:

export OPENSSL_LIB=/lib/x86_64-linux-gnu<

The needed value may be obtained by

ldd `which openssl` | grep libcrypto.so | awk '{print $3}' | sed 's#/[^/]*$##'

Define the environment variable USE_LIBCMP for using the latest CMP features and fixes, which implies use of the intermediate library libcmp. When using OpenSSL version 1.x, this is ensured automatically. When using OpenSSL version 3.0 or 3.1 and USE_LIBCMP is not defined, the new CMP features defined in CMP Updates and the Lightweight CMP Profile will not be supported.

From the underlying Security Utilities library the following environment variables are inherited.

• When SECUTILS_USE_ICV is set, configuration files are expected to be integrity protected with an Integrity Check Value (ICV), which may be produced using util/icvutil.
• Use of the UTA library can be enabled by setting SECUTILS_USE_UTA.
• The TLS-related functions may be disabled by setting SECUTILS_NO_TLS.

When using CMake, cmake must be (re-)run after setting or unsetting environment variables.

Since genCMPClient version 2, it is recommended to use CMake to produce the Makefile, for instance as follows:

cmake .

For backward compatibility it is also possible to use instead of CMake pre-defined Makefile_v1; to this end symlink it to Makefile:

ln -s Makefile_v1 Makefile

or use for instance make -f Makefile_v1.

By default Makefile_v1 behaves as if

OPENSSL_DIR=/usr

was given, such that the OpenSSL headers will be searched for in /usr/include and its shared objects in /usr/lib (or /usr/bin for Cygwin).

When using CMake, cmake must be (re-)run after setting or unsetting environment variables.

When using Makefile_v1, you may specify via the environment variable OUT_DIR where the produced libraries (e.g., libgencmp.so*, libcmp.so*, and libsecutils.so*) shall be placed. It defaults to the base directory of the respective library. If the environment variable BIN_DIR is not empty, the the CLI application cmpClient will be built and placed in BIN_DIR. If the variable is unset, . is used by default. For all path variables, relative paths such as . are interpreted relative to the directory of the genCMPClient module. The CC environment variable may be set as needed; it defaults to gcc. For further details on optional environment variables, see the Makefile_v1 and Makefile_src.

Build the software with

make

By default, builds are done in Debug mode. For Release mode use -DCMAKE_BUILD_TYPE=Release or NDEBUG=1. For switching to Debug mode, use -DCMAKE_BUILD_TYPE=Debug and unset NDEBUG.

The result is in, for instance, ./libgencmp.so.2.0. This also builds all required dependencies (such as libsecutils/libsecutils.so.2.0 and cmpossl/libcmp.so.2.0) and an application (./cmpClient) that is intended for demonstration, test, and exploration purposes.

Installing and uninstalling

The software can be installed with, e.g.,

sudo make install

and uninstalled with

sudo make uninstall

The destination is /usr, unless specified otherwise by DESTDIR or ROOTFS.

Building Debian packages

This repository can build the following Debian and source packages.

• libgencmp - the shared library
• libgencmp-dev - development headers and documentation
• cmpclient - simple command-line application with its documentation
• libgencmp*Source.tar.gz -- source tarball

The recommended way is to use CPack with the files produced by CMake as follows:

make deb

Alternatively, Makefile_v1 may be used like this:

make -f Makefile_v1 deb

In this case, the resulting packages are placed in the parent directory (../), and the following dependencies need to be installed:

• debhelper (needed for dh)
• devscripts (needed for debuild)
• libssl-dev
• libsecutils-dev
• libcmp-dev (if used)

The Debian packages may be installed for instance as follows:

sudo dpkg -i libgencmp*deb cmpclient_*.deb

Using the demo client

The CMP demo client is implemented in src/cmpClient.c as part of the CLI.

For simple test invocations the Insta Certifier Demo CA server may be used, for instance as follows:

openssl ecparam -genkey -name prime256v1 -out test.key.pem
./cmpClient -config "" -server pki.certificate.fi:8700/pkix/ \
  -recipient "/C=FI/O=Insta Demo/CN=Insta Demo CA" \
  -secret pass:insta -ref 3078 \
  -cmd cr -newkey test.key.pem -subject "/CN=test" -certout test.cert.pem
openssl x509 -noout -text -in test.cert.pem

As the CMP client interacts via HTTP with an external CMP server, depending on your network you may need to set the environment variable http_proxy.

A demo making use of all supported CMP commands can be executed with

make -f Makefile_v1 demo   

Among others, successful execution should produce a new certificate at creds/operational.crt. You can view this certificate for instance by executing

openssl x509 -noout -text -in creds/operational.crt

Using the CLI-based client

The Command-Line Interface (CLI) of the CMP client is implemented in src/cmpClient.c. It supports most of the features of the genCMPClient library. The CLI use with the available options are documented in cmpClient.pod.

CLI-based tests using the external Insta Demo CA may be invoked using

make -f Makefile_v1 test_Insta

where the PROXY environment variable may be used to override the default in order to reach the Insta Demo CA.

Using the library in own applications

For building the library (and optionally the CLI application) as part of other builds, it is recommended to use Debian packages or CMake.

Another possibility is to use Makefile_v1, for instance as given in the example outer Makefile.mk.

For compiling applications using the library, you will need to #include the header file genericCMPClient.h and add the directories include and libsecutils/include to your C headers path. When the intermediate library libcmp is used, you need to add also the directory cmpossl/include/cmp, define the C macro USE_LIBCMP, and make sure that any OpenSSL header files included have the same version as the one used to build libcmp.

For linking you will need to refer the linker to the CMP and Security Utilities libraries, e.g., -lsecutils -lgencmp. When the intermediate library libcmp is used, -lcmp is needed additionally. Add the directories (e.g., with the linker option -L) where they can be found. See also the environment variable OUT_DIR. Consider using also linker options like -Wl,-rpath=. for helping the Linux loader find the libraries at run time.

Also make sure that the OpenSSL libraries (typically referred to via -lssl -lcrypto) are in your library path and (the version of) the libraries found there by the linker match the header files found by the compiler.

All this is already done for the cmp client application.

Disclaimer

This software including associated documentation is provided ‘as is’. Effort has been spent on quality assurance, but there are no guarantees.

License

This work is licensed under the terms of the Apache Software License 2.0. See the LICENSE.txt file in the top-level directory.

SPDX-License-Identifier: Apache-2.0