git clone "https://boringssl.googlesource.com/boringssl"
The standalone CMake build is primarily intended for developers. If embedding BoringSSL into another project with a pre-existing build system, see INCORPORATING.md.
Unless otherwise noted, build tools must at most five years old, matching Abseil guidelines. If in doubt, use the most recent stable version of each tool.
CMake 3.12 or later is required.
A recent version of Perl is required. On Windows, Active State Perl has been reported to work, as has MSYS Perl. Strawberry Perl also works but it adds GCC to PATH
, which can confuse some build tools when identifying the compiler (removing C:\Strawberry\c\bin
from PATH
should resolve any problems). If Perl is not found by CMake, it may be configured explicitly by setting PERL_EXECUTABLE
.
Building with Ninja instead of Make is recommended, because it makes builds faster. On Windows, CMake's Visual Studio generator may also work, but it not tested regularly and requires recent versions of CMake for assembly support.
On Windows only, NASM is required. If not found by CMake, it may be configured explicitly by setting CMAKE_ASM_NASM_COMPILER
.
Compilers for C11 and C++14, or later, are required. On Windows, MSVC from Visual Studio 2019 or later with Windows 10 SDK 2104 or later are supported, but using the latest versions is recommended. Recent versions of GCC (6.1+) and Clang should work on non-Windows platforms, and maybe on Windows too.
The most recent stable version of Go is required. Note Go is exempt from the five year support window. If not found by CMake, the go executable may be configured explicitly by setting GO_EXECUTABLE
.
On x86_64 Linux, the tests have an optional libunwind dependency to test the assembly more thoroughly.
Using Ninja (note the ‘N’ is capitalized in the cmake invocation):
cmake -GNinja -B build ninja -C build
Using Make (does not work on Windows):
cmake -B build make -C build
You usually don't need to run cmake
again after changing CMakeLists.txt
files because the build scripts will detect changes to them and rebuild themselves automatically.
Note that the default build flags in the top-level CMakeLists.txt
are for debugging—optimisation isn't enabled. Pass -DCMAKE_BUILD_TYPE=Release
to cmake
to configure a release build.
If you want to cross-compile then there is an example toolchain file for 32-bit Intel in util/
. Wipe out the build directory, run cmake
like this:
cmake -B build -DCMAKE_TOOLCHAIN_FILE=../util/32-bit-toolchain.cmake -GNinja
If you want to build as a shared library, pass -DBUILD_SHARED_LIBS=1
. On Windows, where functions need to be tagged with dllimport
when coming from a shared library, define BORINGSSL_SHARED_LIBRARY
in any code which #include
s the BoringSSL headers.
In order to serve environments where code-size is important as well as those where performance is the overriding concern, OPENSSL_SMALL
can be defined to remove some code that is especially large.
See CMake's documentation for other variables which may be used to configure the build.
It's possible to build BoringSSL with the Android NDK using CMake. Recent versions of the NDK include a CMake toolchain file which works with CMake 3.6.0 or later. This has been tested with version r16b of the NDK.
Unpack the Android NDK somewhere and export ANDROID_NDK
to point to the directory. Then run CMake like this:
cmake -DANDROID_ABI=armeabi-v7a \ -DANDROID_PLATFORM=android-19 \ -DCMAKE_TOOLCHAIN_FILE=${ANDROID_NDK}/build/cmake/android.toolchain.cmake \ -GNinja -B build
Once you've run that, Ninja should produce Android-compatible binaries. You can replace armeabi-v7a
in the above with arm64-v8a
and use API level 21 or higher to build aarch64 binaries.
For other options, see the documentation in the toolchain file.
To debug the resulting binaries on an Android device with gdb
, run the commands below. Replace ARCH
with the architecture of the target device, e.g. arm
or arm64
.
adb push ${ANDROID_NDK}/prebuilt/android-ARCH/gdbserver/gdbserver \ /data/local/tmp adb forward tcp:5039 tcp:5039 adb shell /data/local/tmp/gdbserver :5039 /path/on/device/to/binary
Then run the following in a separate shell. Replace HOST
with the OS and architecture of the host machine, e.g. linux-x86_64
.
${ANDROID_NDK}/prebuilt/HOST/bin/gdb target remote :5039 # in gdb
To build for iOS, pass -DCMAKE_OSX_SYSROOT=iphoneos
and -DCMAKE_OSX_ARCHITECTURES=ARCH
to CMake, where ARCH
is the desired architecture, matching values used in the -arch
flag in Apple's toolchain.
Passing multiple architectures for a multiple-architecture build is not supported.
BoringSSL's build system has experimental support for adding a custom prefix to all symbols. This can be useful when linking multiple versions of BoringSSL in the same project to avoid symbol conflicts.
In order to build with prefixed symbols, the BORINGSSL_PREFIX
CMake variable should specify the prefix to add to all symbols, and the BORINGSSL_PREFIX_SYMBOLS
CMake variable should specify the path to a file which contains a list of symbols which should be prefixed (one per line; comments are supported with #
). In other words, cmake -B build -DBORINGSSL_PREFIX=MY_CUSTOM_PREFIX -DBORINGSSL_PREFIX_SYMBOLS=/path/to/symbols.txt
will configure the build to add the prefix MY_CUSTOM_PREFIX
to all of the symbols listed in /path/to/symbols.txt
.
It is currently the caller's responsibility to create and maintain the list of symbols to be prefixed. Alternatively, util/read_symbols.go
reads the list of exported symbols from a .a
file, and can be used in a build script to generate the symbol list on the fly (by building without prefixing, using read_symbols.go
to construct a symbol list, and then building again with prefixing).
This mechanism is under development and may change over time. Please contact the BoringSSL maintainers if making use of it.
ARM, unlike Intel, does not have a userspace instruction that allows applications to discover the capabilities of the processor. Instead, the capability information has to be provided by a combination of compile-time information and the operating system.
BoringSSL determines capabilities at compile-time based on __ARM_NEON
, __ARM_FEATURE_AES
, and other preprocessor symbols defined in Arm C Language Extensions (ACLE). These values are usually controlled by the -march
flag. You can also define any of the following to enable the corresponding ARM feature, but using the ACLE symbols via -march
is recommended.
OPENSSL_STATIC_ARMCAP_NEON
OPENSSL_STATIC_ARMCAP_AES
OPENSSL_STATIC_ARMCAP_SHA1
OPENSSL_STATIC_ARMCAP_SHA256
OPENSSL_STATIC_ARMCAP_PMULL
The resulting binary will assume all such features are always present. This can reduce code size, by allowing the compiler to omit fallbacks. However, if the feature is not actually supported at runtime, BoringSSL will likely crash.
BoringSSL will additionally query the operating system at runtime for additional features, e.g. with getauxval
on Linux. This allows a single binary to use newer instructions when present, but still function on CPUs without them. But some environments don't support runtime queries. If building for those, define OPENSSL_STATIC_ARMCAP
to limit BoringSSL to compile-time capabilities. If not defined, the target operating system must be known to BoringSSL.
The implementations of some algorithms require a trade-off between binary size and performance. For instance, BoringSSL's fastest P-256 implementation uses a 148 KiB pre-computed table. To optimize instead for binary size, pass -DOPENSSL_SMALL=1
to CMake or define the OPENSSL_SMALL
preprocessor symbol.
There are two sets of tests: the C/C++ tests and the blackbox tests. For former are built by Ninja and can be run from the top-level directory with go run util/all_tests.go
. The latter have to be run separately by running go test
from within ssl/test/runner
.
Both sets of tests may also be run with ninja -C build run_tests
, but CMake 3.2 or later is required to avoid Ninja's output buffering.