FIPS Library and Android
This document will provide instructions for building the OpenSSL FIPS Object Module and OpenSSL FIPS Capable library for Android devices. The FIPS Object Module provides validated cryptography, and the FIPS Capable Library uses the validated cryptography. As an OpenSSL developer, you will use the library the same as in the past – except you must call FIPS_mode_set to enter FIPS mode and engage the validated cryptography. If you are not doing business in US Federal and don't need FIPS validated cryptography, then see Android wiki page.
The FIPS Object Module, fipscanister.o, is a sequestered container of object code and data built from source code. The sources, object code and data are strictly controlled by the OpenSSL FIPS 140-2 Security Policy. No changes can be made to the procedure for building the FIPS Object Module, and no changes can be made to the sources. If you need to make changes to the FIPS Object Module, you will need to engage the OpenSSL Foundation for a separate validation.
The FIPS Capable Library is comprised of libcrypto and libssl. They are the same libraries you have been using for years. The FIPS Capable Library is tolerant of changes to procedures and source code. You are allowed to modify them within reason, as long as the changes do not adversely affect the FIPS Object Module.
This guide is intended to be informative and easy to use. In case of discrepancies between this document and the OpenSSL FIPS Security Policy, the Security Policy will prevail. You can download the Security Policy from http://www.openssl.org/docs/fips/.
The script setenv-android.sh is sourced. Sourcing ensures the variables set in the script are available to other scripts that are run later in the process. If you shell does not provide the source command, then use . ./setenv-android.sh (note the leading dot).
The instructions that follow depend upon a properly configured Android NDK and SDK. The NDK is used to compile programs and link the OpenSSL library; while SDK tools are used to push programs to a device. Be sure ANDROID_NDK_ROOT and ANDROID_SDK_ROOT are set properly, and the SDK's tools and platform-tools are available.
Executive Summary
Use the following commands to build and install the OpenSSL FIPS Object Module and OpenSSL FIPS Capable library. Before running the commands download openssl-1.0.1e.tar.gz, openssl-fips-2.0.5.tar.gz and setenv-android.sh; place the files in the same directory (the 'root' directory mentioned below); ensure ANDROID_NDK_ROOT is set; and verify setenv-android.sh suites your taste. ANDROID_API and ANDROID_TOOLCHAIN will be set by the setenv-android.sh script. The files can be obtained from http://www.openssl.org/source/, http://openssl.com/fips/2.0/platforms/android/, and below (see Downloads section).
Prepare the OpenSSL Sources
# From the 'root' directory $ rm -rf openssl-fips-2.0.5/ $ rm -rf openssl-1.0.1e/ $ tar xzf openssl-fips-2.0.5.tar.gz $ tar xzf openssl-1.0.1e.tar.gz $ chmod a+x setenv-android.sh
Build the FIPS Object Module
# From the 'root' directory $ . ./setenv-android.sh $ cd openssl-fips-2.0.5/ $ ./config $ make $ sudo make install # Execute after install $ sudo -E cp $FIPS_SIG /usr/local/ssl/fips-2.0/bin $ sudo -E mv /usr/local/ssl/fips-2.0/ /usr/local/ssl/$ANDROID_API
Build the FIPS Capable Library
# From the 'root' directory $ . ./setenv-android.sh $ cd openssl-1.0.1e/ $ perl -pi -e 's/install: all install_docs install_sw/install: install_docs install_sw/g' Makefile.org $ ./config fips shared no-ssl2 no-ssl3 no-comp no-hw no-engine --openssldir=/usr/local/ssl/$ANDROID_API \ --with-fipsdir=/usr/local/ssl/$ANDROID_API --with-fipslibdir=/usr/local/ssl/$ANDROID_API/lib/ $ make depend $ make all $ sudo -E make install CC=$ANDROID_TOOLCHAIN/arm-linux-androideabi-gcc RANLIB=$ANDROID_TOOLCHAIN/arm-linux-androideabi-ranlib
OpenSSL FIPS Components
While the Executive Summary provided the whirlwind instructions for building and installing the OpenSSL library, this sections provides detailed instructions. There are six steps to building the FIPS Object Module and FIPS Capable Library for use in various projects, and they are listed below. Projects range from simple NDK based command line programs to Android activities using the JNI bridge.
- Acquire the required files
- Adjust the cross-compilation script
- Prepare the OpenSSL sources
- Set the Incore utility PATH
- Build the FIPS Object Module
- Build the FIPS Capable Library
Acquire the Required Files
First, obtain the base files from http://www.openssl.org/source/:
- openssl-1.0.1e.tar.gz
- openssl-fips-2.0.5.tar.gz
Next, acquire the auxiliary files which can be obtained from below (see Downloads section) or http://openssl.com/fips/2.0/platforms/android/. You won't need all the files from the location.
In addition to the required and auxiliary files, there are two test programs available. Download them from below (see Downloads section) or http://openssl.com/fips/2.0/platforms/android/.
openssl-fips-2.0.5.tar.gz includes the FIPS Object Module. openssl-1.0.1e.tar.gz includes the FIPS Capable Library. setenv-android.sh is used to set the cross-compilation environment. fips_hmac.c is used to test the static and dynamic libraries on the device.
After collecting the required files, your working directory will look similar to below.
android-openssl-fips $ ls -l -rw-r--r-- 1 2718 Jun 23 17:54 fips_hmac.c -rw-r--r-- 1 4459777 Jun 15 03:32 openssl-1.0.1e.tar.gz -rw-r--r-- 1 1442754 Jun 23 16:37 openssl-fips-2.0.5.tar.gz -rwxr-xr-x 1 6760 Jun 23 01:52 setenv-android.sh
Adjust the Cross-Compile Script
setenv-android.sh is used to set the cross-compilation environment. Open the script an ensure the following match your needs. If you are using android-ndk-r8e, android-14, and ANDROID_NDK_ROOT is set, then the script should be ready to use as-is.
- _ANDROID_NDK – the version of the NDK. For example, android-ndk-r8e
- _ANDROID_ARCH – the architecture. For example, arch-arm or arch-x86
- _ANDROID_EABI – the version of the EABI tools. For example, arm-linux-androideabi-4.6, arm-linux-androideabi-4.8, x86-4.6 or x86-4.8
- _ANDROID_API – the API level. For example, android-14 or android-18
You should also set ANDROID_SDK_ROOT and ANDROID_NDK_ROOT. The environmental variables are used internally by the Android platform tools and scripts. For details, see Recommended NDK Directory?.
Additional environmental variables which are set by setenv-android.sh and used by Configure and config include the following. You should not need to change them.
- MACHINE – set to armv7
- RELEASE – set to 2.6.37
- SYSTEM – set to android
- ARCH – set to arm
- CROSS_COMPILE – set to arm-linux-androideabi-
- ANDROID_DEV – set to $ANDROID_NDK_ROOT/platforms/$_ANDROID_API/arch-arm/usr
- HOSTCC – set to gcc
Prepare the OpenSSL Sources
Remove stale versions of the OpenSSL FIPS Object Module and FIPS Capable library, and then unpack fresh files. Also ensure the script is executable.
$ rm -rf openssl-fips-2.0.5/ $ rm -rf openssl-1.0.1e/ $ tar xzf openssl-fips-2.0.5.tar.gz $ tar xzf openssl-1.0.1e.tar.gz $ chmod a+x setenv-android.sh
Set the Incore Utility Path
The incore utility is a shell script used by fipsld to embed the FIPS Object Module's expected fingerprint in the OpenSSL shared object or program. The script is located in openssl-fips-2.0.5/util, and you must ensure incore can be found by fipsld.
Since openssl-fips-2.0.5/util is probably not included as one of the directories in the search list specified by the PATH environment variable, the OpenSSL library allows you to specify its path via FIPS_SIG. Export FIPS_SIG as follows by executing find from your working directory. Below, the root directory (PWD) is /home/user/android-openssl-fips/.
$ export FIPS_SIG=`find $PWD -name incore` $ echo $FIPS_SIG /home/user/android-openssl-fips/openssl-fips-2.0.5/util/incore
If incore is already installed in a known location, you can use it from there instead:
$ export FIPS_SIG=`find /usr/local/ssl -name incore` $ echo $FIPS_SIG /usr/local/ssl/android-14/bin/incore
Build the FIPS Object Module
The FIPS Object Module provides the validated cryptography for the OpenSSL library. This section of the document will guide you through the creation of the FIPS Object Module. The Module is governed by the FIPS 140-2 program requirements and you cannot deviate from the OpenSSL FIPS 140-2 Security Policy during any stage during handling, from acquisition, through building, to installation.
The FIPS Object Module build procedures use the cross-compilation tools supplied in the NDK. It does not use Android.mk and friends. A shell script is used to set the environment for the cross-compilation, and you might need to adjust the script to suit your taste.
To compile the FIPS Object Module for the embedded platform, perform the following steps. You cannot specify any arguments to config or make. Note the leading '.' when running the setenv-android.sh script. If you have any errors from the script, then you should fix them before proceeding.
$ . ./setenv-android.sh $ cd openssl-fips-2.0.5/ $ ./config $ make
After make completes, verify fipscanister.o was built for the embedded architecture.
$ find . -name fipscanister.o ./fips/fipscanister.o $ readelf -h ./fips/fipscanister.o | grep -i 'class\|machine' Class: ELF32 Machine: ARM
Finally, install the library. You must run make install without arguments.
$ sudo make install
After installing the FIPS Object Module, the four files of interest can be found in the lib/ directory.
$ ls /usr/local/ssl/fips-2.0/lib/ fipscanister.o fipscanister.o.sha1 fips_premain.c fips_premain.c.sha1
Once installed, you are outside the scope of FIPS 140-2 and allowed to move the library as long as it remains protected.
$ sudo mv /usr/local/ssl/fips-2.0/ /usr/local/ssl/android-14 $ ls /usr/local/ssl/ android-14
The android-14 is the API level you are building for, and is needed if you have multiple OpenSSL libraries installed (for example, you might have macosx, iphoneos, and android-14 in /usr/local/ssl). You can retrieve the API level from ANDROID_API, which was set in the setenv-android.sh script:
$ echo $ANDROID_API android-14
Finally, copy incore into the installation directory. This will allow you to delete the temporary folders in your working area (openssl-fips-2.0.5 and openssl-1.0.1e) once the libraries are installed.
$ find . -name incore ./util/incore $ sudo cp ./util/incore /usr/local/ssl/android-14/bin/ $ ls /usr/local/ssl/android-14/bin/ fipsld fips_standalone_sha1 incore
Build the FIPS Capable Library
The FIPS Capable Library is a standard OpenSSL distribution that can use the validated cryptography provided by the FIPS Object Module. This section of the document will guide you through the creation of the the FIPS Capable Library. You are allowed to modify the FIPS Capable Library within reason, as long as it does not adversely affect the FIPS Object Module.
The FIPS Capable version of the library can operate with or without FIPS validated cryptography. It handles all the details of operation while in FIPS mode after you successfully call FIPS_mode_set. If you don't call FIPS_mode_set, the library will still operate as expected; but it will not be using validated cryptography. Its recommended that you build the shared object since Android will load and link it out of the box. If you build a static library, then you will have to build a wrapper shared object around the static archive.
The FIPS Capable Makefile (and Makefile.org) needs its install rule modified. The install rule includes the all target, which causes items to be built during install. A bug in the process when running as root results in an empty signature for the shared object (the signature is a string of zeros).
To build the FIPS Capable library, you must issue config fips, but other options are up to you. Some suggested options for configure include: shared, no-ssl2, no-ssl3, no-comp, no-hw, and no-engine. shared will build and install both the shared object and static archive. You should specify --openssldir, --with-fipsdir and --with-fipslibdir to ensure the FIPS Capable build system finds components from the FIPS Object Module.
Begin building the FIPS Capable library by setting the cross-compilation environment. Note the leading '.' when running the setenv-android.sh script. If you have any errors from the script, then you should fix them before proceeding.
$ . ./setenv-android.sh $ cd openssl-1.0.1e/
Next, fix the makefile and run configure.
$ perl -pi -e 's/install: all install_docs install_sw/install: install_docs install_sw/g' Makefile.org $ ./config fips shared no-ssl2 no-ssl3 no-comp no-hw no-engine --openssldir=/usr/local/ssl/android-14/ \ --with-fipsdir=/usr/local/ssl/android-14/ --with-fipslibdir=/usr/local/ssl/android-14/lib/
Then run make depend and make all:
$ make depend $ make all
After make completes, verify libcrypto.a and libssl.a were built for the embedded architecture.
$ find . -name libcrypto.a ./libcrypto.a $ readelf -h ./libcrypto.a | grep -i 'class\|machine' | head -2 Class: ELF32 Machine: ARM
Finally, install the library. The makefile's install rule uses both CC and RANLIB, so you will need to fully specify the command variables on the command line (during install, sudo drops the user's path). You must also use sudo's -E option; otherwise ANDROID_TOOLCHAIN will be empty and tools such as arm-linux-androideabi-gcc and arm-linux-androideabi-ranlib will not be found.
$ sudo -E make install CC=$ANDROID_TOOLCHAIN/arm-linux-androideabi-gcc RANLIB=$ANDROID_TOOLCHAIN/arm-linux-androideabi-ranlib
Testing the OpenSSL Libraries
Testing the installation consists of building a sample program, installing it with adb, and then running the program using a remote shell. Both the static and dynamic version of the OpenSSL library can be tested using fips_hmac, which is a test program to calculate a hmac over the files given as arguments.
The test program is built in a cross-compilation environment, just like the FIPS Object Module and FIPS Capable library. To begin, set the Android environment and verify ANDROID_SYSROOT. Note the leading '.' when running the setenv-android.sh script. If you have any errors from the script, then you should fix them before proceeding.
$ . ./setenv-android.sh $ echo $ANDROID_SYSROOT /opt/android-ndk-r8e/platforms/android-14/arch-arm
Linking with the shared object is easiest. That's because the FIPS Capable library build process takes care of a number of items for you, including running fipsld on the shared object. The downside to dynamic linking is you have to push the program and shared object to the device and modify the loader path before executing.
The command below compiles fips_hmac.c using ANDROID_SYSROOT and the shared object (libcrypto.so). ANDROID_SYSROOT specifies the location of Android's headers and libraries, and is set using setenv-android.sh.
$ arm-linux-androideabi-gcc --sysroot="$ANDROID_SYSROOT" -I/usr/local/ssl/android-14/include \ fips_hmac.c -o fips_hmac.exe /usr/local/ssl/android-14/lib/libcrypto.so
There's no need to run fipsld on a program which dynamically links to the OpenSSL library.
Once the program is built, push it to the device and execute it. The hashes produced by the test program will vary with the files being digested.
# Copy the program and shared library to the Android device $ adb push fips_hmac.exe /data/local/tmp/ 303 KB/s (18548 bytes in 0.059s) $ adb push libcrypto.so.1.0.0 /data/local/tmp 1106 KB/s (2154620 bytes in 1.900s) # Execute the program on the Android device $ adb shell shell@android: $ cd /data/local/tmp shell@android: $ LD_LIBRARY_PATH=./; ./fips_hmac.exe -v fips_hmac.exe FIPS mode enabled f178788e8a439dbaaa760ef774e8d92e01d2440e
Linking with the Static Archive
Linking against the static library is more challenging. That's because you have to set two variables – CC and FIPSLD_CC and compile with the modified CC. They must be exported because fipsld uses them in child shells. Behind the scenes, fipsld will compile and link fips_premain.c, modify the libcrypto archive, assemble the final program, and embed the fingerprint.
$ export CC=`find /usr/local/ssl/$ANDROID_API -name fipsld` $ echo $CC /usr/local/ssl/android-14/bin/fipsld $ export FIPSLD_CC="$ANDROID_TOOLCHAIN/arm-linux-androideabi-gcc" $ echo $FIPSLD_CC /opt/android-ndk-r8e/toolchains/arm-linux-androideabi-4.6/prebuilt/linux-x86/bin/arm-linux-androideabi-gcc
Finally, compile and link as normal using CC. The command below compiles fips_hmac.c using ANDROID_SYSROOT and the static archive (libcrypto.a). ANDROID_SYSROOT specifies the location of Android's headers and libraries, and is set using setenv-android.sh.
$ $CC --sysroot="$ANDROID_SYSROOT" -I/usr/local/ssl/android-14/include fips-test.c \
-o fips-test.exe /usr/local/ssl/android-14/lib/libcrypto.a
You can use fipsld to create an object file rather than compile and link. In this case, fipsld will simply pass all arguments to arm-linux-androideabi-gcc.
$ $CC --sysroot="$ANDROID_SYSROOT" -I/usr/local/ssl/android-14/include -c fips-test.c
Once the program is built, push it to the device and execute it. The hashes produced by the test program will vary with the files being digested.
# Copy the program to the Android device $ adb push fips_hmac.exe /data/local/tmp 1099 KB/s (1462276 bytes in 1.298s) # Execute the program on the Android device $ adb shell shell@android: $ cd /data/local/tmp shell@android: $ fips_hmac.exe -v fips_hmac.exe FIPS mode enabled a7518364fbba32cca0df974ee646e8a13833eb3d
Using OpenSSL on Android often involves JNI and the platform's version of OpenSSL or BoringSSL. The platform likely loaded the system's version of libssl.so and libcrypto.so at boot during Zygote initialization. Due to issues with the loader and symbol resolution, customary LD_LIBRARY_PATH tricks do not work for most applications. And changing the build to output different library names, like libmyssl.so and libmycrypto.so, to avoid clashes does not work either.
The solution to the namespace and symbol resolution problems is to wrap the static version of the OpenSSL library in a separate dynamic library or shared object provided by you. To do so, write a small C wrapper library with references to functions you need from the OpenSSL library. You don't need to wrap all the functions.
Your wrapper.c might look as follows (also see GCC's Visibility page):
#if __GNUC__ >= 4
#define DLL_PUBLIC __attribute__ ((visibility ("default")))
#define DLL_LOCAL __attribute__ ((visibility ("hidden")))
#else
#define DLL_PUBLIC
#define DLL_LOCAL
#endif
DLL_PUBLIC void My_OpenSSL_add_all_algorithms() {
return (void)OpenSSL_add_all_algorithms();
}
DLL_PUBLIC void My_SSL_load_error_strings() {
return (void)SSL_load_error_strings();
}
...
Then, compile the source file into a shared object. A typical command line might look as follows.
$ export OPENSSL_ANDROID = /usr/local/ssl/android-14 $ $(CC) wrapper.c -fPIC -shared -I$(OPENSSL_ANDROID)/include -fvisibility=hidden -Wl,--exclude-libs,ALL \ -Wl,-Bstatic -lcrypto -lssl -L$(OPENSSL_ANDROID)/lib -o wrapper.so -Wl,-Bdynamic
-fvisibility=hidden works as you expect, and -Wl,--exclude-libs,ALL means your library does not re-export other linked library symbols. Only the functions marked with DLL_PUBLIC will be exported and callable through JNI.
The -Wl,-Bstatic tells the linker to use the static version of the OpenSSL library for the Library. After it and the -Wl,-Bdynamic tells the linker to use dynamic linking for anything else it might need, like libc.
Then use your shared object in place of OpenSSL.
Miscellaneous
The following lists some miscellaneous items we are aware.
FIPS Object Module
Once the FIPS Object Module and FIPS Capable Library are installed, you can safely delete the source directories. The headers, libraries and programs (such as fipsld and incore) are located in sub-directories of /usr/local/ssl/<platform>.
If you don't care about FIPS 140-2 and just want to build the library for Android, then see OpenSSL and Android.
Position Independent Code
The NDK supplies headers for each major platform - for example, API 18, API 14, API 9, API 8, and API 5. If you are building for Android 4.2 (API 17), Android 4.1 (API 16) and Android 4.0 (API 14), then you would use the NDK's API 14 (android-14 platform).
Specify the full library name when calling Java's System.load. That is, call System.load(“libcrypto.so.1.0.0”). Also note that some Android routines expect the prefix of “lib” and suffix of “so”, so you might have to rename the library.
Some versions of the Android Java system loader will load the system's version of the OpenSSL library, even though you built and included a copy with your application. In this case, you might need to write a wrapper shared object and link to the static version of the OpenSSL library. See, for example, "Unable to find native library" error in Native Activity app.
If you compile with -fPIE and -pie, then you will core dump unless using Android 4.1 and above. Logcat shows the linker (/system/bin/linker) is the problem.
shell@android: $ ./fips_hmac.exe -v fips_hmac.exe [2] + Stopped (signal) ./fips_hmac.exe -v fips_hmac.exe [1] - Segmentation fault ./fips_hmac.exe -v fips_hmac.exe
When building the OpenSSL library for Android, take care to specify -mfloat-abi=softfp. If you specify -mfloat-abi=hard or -mhard-float (even if the hardware support a floating point unit), then the entropy estimate passed through the Java VM to RAND_add will always be 0.0f. See Hard-float and JNI for details.
Static Library Linking
Using -Bstatic and -Bshared can cause link problems on occasion. For example, see Android: error when trying to compile wrapper for openssl library libcrypto.a. To avoid the problem with the linker, specify the full path to the static archive (for example, /usr/local/ssl/android-14/lib/libcrypto.a). If you suspect the wrong OpenSSL library is being linked, then use the fully qualified archive path.
Downloads
OpenSSL FIPS Library and Android Guide - this page as a PDF document.
OpenSSL-FIPS-Android.tar.gz - Roll-up of the files provided on this page.
setenv-android.sh - script to set Android cross-compile environment.
fips_hmac.c - test program to mac files given as program arguments.
fips-test.c - test program to dump critical FIPS parameters.
