How to Cross Compile OpenSSL a Step by Step Guide

Introduction

This tutorial will show how to cross compile the OpenSSL software on an GNU Linux embedded platform.

Overview of the project

The OpenSSL Project is a collaborative effort to develop a robust, commercial-grade, full-featured, and Open Source toolkit implementing the Secure Sockets Layer (SSL v2/v3) and Transport Layer Security (TLS v1) protocols as well as a full-strength general purpose cryptography library. The project is managed by a worldwide community of volunteers that use the Internet to communicate, plan, and develop the OpenSSL toolkit and its related documentation.

OpenSSL is based on the excellent SSLeay library developed by Eric A. Young and Tim J. Hudson. The OpenSSL toolkit is licensed under an Apache-style licence, which basically means that you are free to get and use it for commercial and non-commercial purposes subject to some simple license conditions.

To find out more about OpenSSL and its components see the project's website http://www.openssl.org.

Download

OpenSSL software releases can be found at: http://www.openssl.org/source/.

The latest available release by the time of writing of this tutorial is 0.9.8g (October 19th 2007).

To download this release, just type the following command:

wget http://www.openssl.org/source/openssl-0.9.8g.tar.gz

Environment Setup

The host machine will be a PC with a GNU Linux distribution installed.
The embedded platform might be constructed on top of one of the following architectures:

arm.
mips.
mipsel.
ppc.
sparc.

Prerequisites

To cross compile the OpenSSL project, you need either a cross compiler, or an emulated Linux running on top of a virtualization software such as QEMU, matching your specific targeted platform.

In order to build yourself such a cross compiler, at crosstool page we introduced the way to build a C,C++ 4.1 GNU compiler for an ARM platform.

Also, hackers will be interested finding all the details to setup an ARM Debian system on their traditional Ubuntun distro following the indications quoted in this other arm-debian-on-ubuntu.

The OpenSSL project does not need any specific dependencies.

The Cross compilation process

Option 1: Using a cross compiler

Assumptions
During the process, we will assume the cross toolchain is called xxx-yyy-linux-gnu, meaning that the gcc, g++, ar, ..., ld utilities are prefixed by xxx-yyy-linux-gnu. For example, for this toolchain the C compiler is called xxx-yyy-linux-gnu-gcc.

We will also assume that the bin, include, lib and libexec folders of the cross toolchain are accessible through the PATH variable environment in order to work with the compilers from any place in the file system.

Finally, we suppose it is intalled in the following folder: /opt/crosstool/gcc-4.1.2-glibc-2.3.2/xxx-yyy-linux-gnu.

Organization

As mentioned above:

The release being cross compiled is: 0.9.8g
The tar.gz file will then be extracted under: /opt/external_packages/openssl/0.9.8g/source
The results of the compilation will be stored under: /opt/external_packages/openssl/0.9.8g/compiled/xxx-yyy-linux-gnu

The files resulting from the cross compilation are listed here (the content of the man folder is intentionaly not displayed):



.:
   total 40
   drwxr-xr-x 2 root root 4096 2008-03-07 12:33 bin
   drwxr-xr-x 2 root root 4096 2008-03-07 12:33 certs
   drwxr-xr-x 3 root root 4096 2008-03-07 12:33 include
   drwxr-xr-x 4 root root 4096 2008-03-07 12:33 lib
   drwxr-xr-x 6 root root 4096 2008-03-07 12:32 man
   drwxr-xr-x 2 root root 4096 2008-03-07 12:33 misc
   -rw-r--r-- 1 root root 9374 2008-03-07 12:33 openssl.cnf
   drwxr-xr-x 2 root root 4096 2008-03-07 12:33 private


./bin:
   total 1624
   -rwxr-xr-x 1 root root    3648 2008-03-07 12:33 c_rehash
   -rwxr-xr-x 1 root root 1650844 2008-03-07 12:33 openssl


./certs:
   total 0


./include:
   total 4
   drwxr-xr-x 2 root root 4096 2008-03-07 12:33 openssl


./include/openssl:
   total 1336
   -rw-r--r-- 1 root root   5372 2008-03-07 12:33 aes.h
   -rw-r--r-- 1 root root  46728 2008-03-07 12:33 asn1.h
   -rw-r--r-- 1 root root  18956 2008-03-07 12:33 asn1_mac.h
   -rw-r--r-- 1 root root  27838 2008-03-07 12:33 asn1t.h
   -rw-r--r-- 1 root root  30772 2008-03-07 12:33 bio.h
   -rw-r--r-- 1 root root   5073 2008-03-07 12:33 blowfish.h
   -rw-r--r-- 1 root root  33035 2008-03-07 12:33 bn.h
   -rw-r--r-- 1 root root   4565 2008-03-07 12:33 buffer.h
   -rw-r--r-- 1 root root   4349 2008-03-07 12:33 cast.h
   -rw-r--r-- 1 root root   1601 2008-03-07 12:33 comp.h
   -rw-r--r-- 1 root root   4080 2008-03-07 12:33 conf_api.h
   -rw-r--r-- 1 root root   9484 2008-03-07 12:33 conf.h
   -rw-r--r-- 1 root root  22121 2008-03-07 12:33 crypto.h
   -rw-r--r-- 1 root root  10724 2008-03-07 12:33 des.h
   -rw-r--r-- 1 root root  18226 2008-03-07 12:33 des_old.h
   -rw-r--r-- 1 root root   8372 2008-03-07 12:33 dh.h
   -rw-r--r-- 1 root root  10474 2008-03-07 12:33 dsa.h
   -rw-r--r-- 1 root root  16252 2008-03-07 12:33 dso.h
   -rw-r--r-- 1 root root   6146 2008-03-07 12:33 dtls1.h
   -rw-r--r-- 1 root root    540 2008-03-07 12:33 ebcdic.h
   -rw-r--r-- 1 root root   4609 2008-03-07 12:33 ecdh.h
   -rw-r--r-- 1 root root  10578 2008-03-07 12:33 ecdsa.h
   -rw-r--r-- 1 root root  21389 2008-03-07 12:33 ec.h
   -rw-r--r-- 1 root root  37839 2008-03-07 12:33 engine.h
   -rw-r--r-- 1 root root   9632 2008-03-07 12:33 e_os2.h
   -rw-r--r-- 1 root root  12493 2008-03-07 12:33 err.h
   -rw-r--r-- 1 root root  35620 2008-03-07 12:33 evp.h
   -rw-r--r-- 1 root root   4368 2008-03-07 12:33 hmac.h
   -rw-r--r-- 1 root root   4364 2008-03-07 12:33 idea.h
   -rw-r--r-- 1 root root   7642 2008-03-07 12:33 krb5_asn.h
   -rw-r--r-- 1 root root   5927 2008-03-07 12:33 kssl.h
   -rw-r--r-- 1 root root   7429 2008-03-07 12:33 lhash.h
   -rw-r--r-- 1 root root   3897 2008-03-07 12:33 md2.h
   -rw-r--r-- 1 root root   4661 2008-03-07 12:33 md4.h
   -rw-r--r-- 1 root root   4661 2008-03-07 12:33 md5.h
   -rw-r--r-- 1 root root  33396 2008-03-07 12:33 objects.h
   -rw-r--r-- 1 root root 113729 2008-03-07 12:33 obj_mac.h
   -rw-r--r-- 1 root root  23795 2008-03-07 12:33 ocsp.h
   -rw-r--r-- 1 root root   6308 2008-03-07 12:33 opensslconf.h
   -rw-r--r-- 1 root root   3751 2008-03-07 12:33 opensslv.h
   -rw-r--r-- 1 root root   6446 2008-03-07 12:33 ossl_typ.h
   -rw-r--r-- 1 root root   2863 2008-03-07 12:33 pem2.h
   -rw-r--r-- 1 root root  27927 2008-03-07 12:33 pem.h
   -rw-r--r-- 1 root root  12677 2008-03-07 12:33 pkcs12.h
   -rw-r--r-- 1 root root  16333 2008-03-07 12:33 pkcs7.h
   -rw-r--r-- 1 root root   6150 2008-03-07 12:33 pq_compat.h
   -rw-r--r-- 1 root root   3519 2008-03-07 12:33 pqueue.h
   -rw-r--r-- 1 root root   5251 2008-03-07 12:33 rand.h
   -rw-r--r-- 1 root root   4294 2008-03-07 12:33 rc2.h
   -rw-r--r-- 1 root root   3707 2008-03-07 12:33 rc4.h
   -rw-r--r-- 1 root root   4284 2008-03-07 12:33 ripemd.h
   -rw-r--r-- 1 root root  18202 2008-03-07 12:33 rsa.h
   -rw-r--r-- 1 root root 126893 2008-03-07 12:33 safestack.h
   -rw-r--r-- 1 root root   7329 2008-03-07 12:33 sha.h
   -rw-r--r-- 1 root root   3744 2008-03-07 12:33 ssl23.h
   -rw-r--r-- 1 root root  10716 2008-03-07 12:33 ssl2.h
   -rw-r--r-- 1 root root  22283 2008-03-07 12:33 ssl3.h
   -rw-r--r-- 1 root root  82501 2008-03-07 12:33 ssl.h
   -rw-r--r-- 1 root root   4418 2008-03-07 12:33 stack.h
   -rw-r--r-- 1 root root  26481 2008-03-07 12:33 store.h
   -rw-r--r-- 1 root root  19456 2008-03-07 12:33 symhacks.h
   -rw-r--r-- 1 root root  18121 2008-03-07 12:33 tls1.h
   -rw-r--r-- 1 root root   4117 2008-03-07 12:33 tmdiff.h
   -rw-r--r-- 1 root root   4300 2008-03-07 12:33 txt_db.h
   -rw-r--r-- 1 root root   3439 2008-03-07 12:33 ui_compat.h
   -rw-r--r-- 1 root root  16418 2008-03-07 12:33 ui.h
   -rw-r--r-- 1 root root  47946 2008-03-07 12:33 x509.h
   -rw-r--r-- 1 root root  29980 2008-03-07 12:33 x509v3.h
   -rw-r--r-- 1 root root  20782 2008-03-07 12:33 x509_vfy.h


./lib:
   total 2540
   drwxr-xr-x 2 root root    4096 2008-03-07 12:33 engines
   -rw-r--r-- 1 root root 2200932 2008-03-07 12:33 libcrypto.a
   -rw-r--r-- 1 root root  379740 2008-03-07 12:33 libssl.a
   drwxr-xr-x 2 root root    4096 2008-03-07 12:33 pkgconfig


./lib/engines:
   total 0


./lib/pkgconfig:
   total 12
   -rw-r--r-- 1 root root 278 2008-03-07 12:33 libcrypto.pc
   -rw-r--r-- 1 root root 293 2008-03-07 12:33 libssl.pc
   -rw-r--r-- 1 root root 303 2008-03-07 12:33 openssl.pc


./misc:
   total 28
   -rwxr-xr-x 1 root root 5679 2008-03-07 12:33 CA.pl
   -rwxr-xr-x 1 root root 3758 2008-03-07 12:33 CA.sh
   -rwxr-xr-x 1 root root  119 2008-03-07 12:33 c_hash
   -rwxr-xr-x 1 root root  152 2008-03-07 12:33 c_info
   -rwxr-xr-x 1 root root  112 2008-03-07 12:33 c_issuer
   -rwxr-xr-x 1 root root  110 2008-03-07 12:33 c_name


./private:
   total 0

Cross Compiling

Step 1

Install the OpenSSL software by untaring it in /opt/external_packages/openssl/0.9.8g/source folder and then cd to this directory.

Note:
All the directories and files listed below must be moved from the openssl-0.9.8g folder
to its parent folder (/opt/external_packages/openssl/0.9.8g/source).

Directories and files:

   apps                                     Configure  include        INSTALL.W32      makevms.com   PROBLEMS       tools
   bugs                                     crypto     INSTALL        INSTALL.W64      ms            README         util
   certs                                    demos      install.com    INSTALL.WCE      Netware       README.ASN1    VMS
   ChangeLog.0_9_7-stable_not-in-head       doc        INSTALL.DJGPP  LICENSE          NEWS          README.ENGINE
   ChangeLog.0_9_7-stable_not-in-head_FIPS  engines    INSTALL.MacOS  MacOS            openssl.doxy  shlib
   CHANGES                                  e_os2.h    INSTALL.NW     Makefile         openssl.spec  ssl
   CHANGES.SSLeay                           e_os.h     INSTALL.OS2    Makefile.org     os2           test
   config                                   FAQ        INSTALL.VMS    Makefile.shared  perl          times

Step 2

We want to cross compile OpenSSL with the following options:

NO_CAMELLIA
NO_GMP
NO_MDC2
NO_RC5
NO_RFC3779
NO_SEED
NO_TLSEXT
IDEA
RC2, RC4
DES
AES

Step 3

There is no need to type configure, a Makefile is already existing. We just need to edit it and change it with way:

INSTALLTOP=/opt/external_packages/openssl/0.9.8g/compiled/xxx-yyy-linux-gnu
OPENSSLDIR=/opt/external_packages/openssl/0.9.8g/compiled/xxx-yyy-linux-gnu
CC= xxx-yyy-linux-gnu-gcc
AR=xxx-yyy-linux-gnu-ar $(ARFLAGS) r
RANLIB= xxx-yyy-linux-gnu-ranlib

Step 4

To compile and install the OpenSSL project, type successively make and make install. You should find the directories and files listed above under /opt/external_packages/openssl/0.9.8g/compiled/xxx-yyy-linux-gnu/.

Option 2: Using QEMU

This section is not yet available.

Download

arm-openssl-0.9.8g-tar.gz

You may consult this section if you want to download the OpenSSL software already cross compiled for your target platform if it is available. You can also contribute to expand the crosscompile.org community by uploading your own results in the case a given platform is not already supported.

Supported platforms

arm-unknown-linux-gnu

Written by David Sayada.

Edit History Last Modified March 10, 2008

crosscompile.org

cross compilation guides, reference manuals, how to's, etc.

How to Cross Compile OpenSSL a Step by Step Guide

Introduction

Overview of the project

Download

Environment Setup

Prerequisites

The Cross compilation process

Option 1: Using a cross compiler

Organization

Cross Compiling

Step 1

Step 2

Step 3

Step 4

Option 2: Using QEMU

Download

Supported platforms