README ====== blhc (build log hardening check) is a small tool which checks build logs for missing hardening flags. It's licensed under the GPL 3 or later. Hardening flags enable additional security features in the compiler to prevent e.g. stack overflows, format string vulnerabilities, GOT overwrites, etc. Because most build systems are quite complicated there are many places where compiler flags from the environment might be ignored. The parser verifies that all compiler commands use the correct hardening flags and thus all hardening features are correctly used. It's designed to check build logs generated by Debian's dpkg-buildpackage (or tools using dpkg-buildpackage like pbuilder or sbuild (which is used for the official buildd build logs)) to help maintainers detect missing hardening flags in their packages. At the moment it works only on Debian and derivatives but it should be easily extendable to other systems as well. Patches are welcome. Only gcc is detected as compiler at the moment. If other compilers support hardening flags as well, please report them. For more information about hardening flags have a look at [1]. [1]: https://wiki.debian.org/Hardening DEPENDENCIES ------------ - Perl - Dpkg::Arch - Dpkg::Version - Term::ANSIColor >= 2.01 Bundled with perl. A recent version is only necessary for build logs with ANSI colors which is rare, blhc works fine without if the build log doesn't use colors. Not required for buildd mode. USAGE ----- blhc path/to/log/file blhc can be run directly from the source tree (`bin/blhc`) or copied anywhere on the system. It doesn't have to be explicitly installed. To read the man page use `perldoc bin/blhc`. If there's no output, no flags are missing and the build log is fine. For more examples see the man page. CHECKS ------ blhc checks all compiler lines (lines matching `gcc`) for hardening flags (same as set by `dpkg-buildflags`). If a compiler flag is missing a warning with the missing flags is printed. Consider the following compiler line: gcc -g -O2 -o test test.c blhc generates the following warnings because all hardening flags are missing: CFLAGS missing (-fstack-protector-strong -Wformat -Werror=format-security): gcc -g -O2 -o test test.c CPPFLAGS missing (-D_FORTIFY_SOURCE=2): gcc -g -O2 -o test test.c LDFLAGS missing (-Wl,-z,relro): gcc -g -O2 -o test test.c Preprocessing, linking and compiling is automatically detected: gcc -MM test.c > test.d gcc -E test.c gcc -o test test.o CPPFLAGS missing (-D_FORTIFY_SOURCE=2): gcc -E test.c LDFLAGS missing (-Wl,-z,relro): gcc -o test test.o blhc differentiates the following flags: - CPPFLAGS: preprocessor flags - CFLAGS: C compiler flags - CXXFLAGS: C++ compiler flags - LDFLAGS: linker flags Both '-O2' and '-O3' are recognized as valid, even though only '-O2' is printed in warnings. It handles all file extensions as documented by gcc regarding preprocessing, linking, compiling. The architecture of the build log is automatically detected by looking for the following line (output of dpkg-buildpackage): dpkg-buildpackage: host architecture The available hardening flags are adapted to the architecture because some architectures don't support certain hardening options. Some checks check the build dependencies for certain packages. The following lines are used to get the build dependencies. The first two are used in buildd build logs (the second was used in older logs), the third by pbuilder logs, all are detected: Filtered Buildd-Depends: ... Build-Depends: ... Depends: ... LIMITATIONS ----------- The build log must contain the following line which marks the beginning of the real compile process (output of dpkg-buildpackage): dpkg-buildpackage: ... If it's not present no compiler commands are detected. In case you don't use dpkg-buildpackage but still want to check a build log, adding it as first line should work fine. To prevent false positives when checking debug builds, compiler lines containing '-OO' or '-Og' are considered debug builds and are not checked for '-O2', even though fortification doesn't work without '-O2'. The following non-verbose builds can't be detected: gcc -o test This is not detected because `test` has no file extension. A file extension is required on a compiler line to prevent many false positives. As the build will most likely contain other non-verbose build commands (e.g. `gcc test.c`) which are correctly detected as non-verbose this shouldn't be a problem. Some CMake non-verbose linker commands are also not correctly detected at the moment. blhc still creates a few false positives. Patches to fix them are very welcome as long as they won't cause any false negatives. BUILDD MODE ----------- Buildd mode is enabled if '--buildd' is used. It's designed to check build logs from Debian's buildds. Instead of normal warning messages only tags are printed at the end of the check. See the man page for possible tags. BUGS ---- If you find any bugs not mentioned in this document please report them to with blhc in the subject. AUTHORS ------- Written by Simon Ruderich . Thanks to Bernhard R. Link and Jaria Alto for their valuable input and suggestions. LICENSE ------- blhc is licensed under GPL version 3 or later. Copyright (C) 2012-2023 Simon Ruderich This program is free software: you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation, either version 3 of the License, or (at your option) any later version. This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details. You should have received a copy of the GNU General Public License along with this program. If not, see . // vim: ft=asciidoc