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
- 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.