UNIX BUILD NOTES

Security

To help make your Bitcoin Core installation more secure by making certain attacks impossible to exploit even if a vulnerability is found, binaries are hardened by default. This can be disabled with:

Hardening Flags:

./configure --enable-hardening
./configure --disable-hardening

Hardening enables the following features: Position Independent Executable: Build position independent code to take advantage of Address Space Layout Randomization offered by some kernels. Attackers who can cause execution of code at an arbitrary memory location are thwarted if they don't know where anything useful is located. The stack and heap are randomly located by default, but this allows the code section to be randomly located as well. On an AMD64 processor where a library was not compiled with -fPIC, this will cause an error such as: "relocation R_X86_64_32 against `......' can not be used when making a shared object;"
To test that you have built PIE executable, install scanelf, part of paxutils, and use: scanelf -e ./bitcoin

• The output should contain:
  TYPE ET_DYN
• Non-executable Stack: If the stack is executable then trivial stack-based buffer overflow exploits are possible if vulnerable buffers are found. By default, Bitcoin Core should be built with a non-executable stack, but if one of the libraries it uses asks for an executable stack or someone makes a mistake and uses a compiler extension which requires an executable stack, it will silently build an executable without the non-executable stack protection.

To verify that the stack is non-executable after compiling use: scanelf -e ./bitcoin
The output should contain: STK/REL/PTL RW- R-- RW-
The STK RW- means that the stack is readable and writeable but not executable.

Disable-wallet mode

When the intention is to run only a P2P node without a wallet, Bitcoin Core may be compiled in disable-wallet mode with:

./configure --disable-wallet
In this case there is no dependency on Berkeley DB 4.8 and SQLite.

Mining is also possible in disable-wallet mode using the getblocktemplate RPC call.

Additional Configure Flags

A list of additional configure flags can be displayed with:

./configure --help

Setup and Build Example: Arch Linux

This example lists the steps necessary to setup and build a command line only, non-wallet distribution of the latest changes on Arch Linux:

pacman -S git base-devel boost libevent python
git clone https://github.com/bitcoin/bitcoin.git
cd bitcoin/
./autogen.sh
./configure --disable-wallet --without-gui --without-miniupnpc
make check

Note: Enabling wallet support requires either compiling against a Berkeley DB newer than 4.8 (package db) using --with-incompatible-bdb, or building and depending on a local version of Berkeley DB 4.8. The readily available Arch Linux packages are currently built using --with-incompatible-bdb according to the PKGBUILD. As mentioned above, when maintaining portability of the wallet between the standard Bitcoin Core distributions and independently built node software is desired, Berkeley DB 4.8 must be used.

ARM Cross-compilation

These steps can be performed on, for example, an Ubuntu VM. The depends system will also work on other Linux distributions, however the commands for installing the toolchain will be different.
Make sure you install the build requirements mentioned above. Then, install the toolchain and curl:

sudo apt-get install g++-arm-linux-gnueabihf curl