4 blhc (build log hardening check) is a small tool which checks build logs for
5 missing hardening flags. It's licensed under the GPL 3 or later.
7 Hardening flags enable additional security features in the compiler to prevent
8 e.g. stack overflows, format string vulnerabilities, GOT overwrites, etc.
10 Because most build systems are quite complicated there are many places where
11 compiler flags from the environment might be ignored. The parser verifies that
12 all compiler commands use the correct hardening flags and thus all hardening
13 features are correctly used.
15 It's designed to check build logs generated by Debian's dpkg-buildpackage (or
16 tools using dpkg-buildpackage like pbuilder or the official buildd build logs)
17 to help maintainers detect missing hardening flags in their packages.
19 At the moment it works only on Debian and derivatives but it should be easily
20 extendable to other systems as well. Patches are welcome.
22 Only gcc is detected as compiler at the moment. If other compilers support
23 hardening flags as well, please report them.
25 For more information about hardening flags have a look at [1].
27 [1]: https://wiki.debian.org/Hardening
36 - Term::ANSIColor >= 2.01
37 Bundled with perl. A recent version is only necessary for build logs with
38 ANSI colors which is rare, blhc works fine without if the build log
39 doesn't use colors. Not required for buildd mode.
47 blhc can be run directly from the source tree (`bin/blhc`) or copied anywhere
48 on the system. It doesn't have to be explicitly installed. To read the man
49 page use `perldoc bin/blhc`.
51 If there's no output, no flags are missing and the build log is fine.
53 For more examples see the man page.
59 blhc checks all compiler lines (lines matching `gcc`) for hardening flags
60 (same as set by `dpkg-buildflags`). If a compiler flag is missing a warning
61 with the missing flags is printed.
63 Consider the following compiler line:
65 gcc -g -O2 -o test test.c
67 blhc generates the following warnings because all hardening flags are missing:
69 CFLAGS missing (-fstack-protector --param=ssp-buffer-size=4 -Wformat -Wformat-security -Werror=format-security): gcc -g -O2 -o test test.c
70 CPPFLAGS missing (-D_FORTIFY_SOURCE=2): gcc -g -O2 -o test test.c
71 LDFLAGS missing (-Wl,-z,relro): gcc -g -O2 -o test test.c
73 Preprocessing, linking and compiling is automatically detected:
75 gcc -MM test.c > test.d
79 CPPFLAGS missing (-D_FORTIFY_SOURCE=2): gcc -E test.c
80 LDFLAGS missing (-Wl,-z,relro): gcc -o test test.o
82 blhc differentiates the following flags:
84 - CPPFLAGS: preprocessor flags
85 - CFLAGS: C compiler flags
86 - CXXFLAGS: C++ compiler flags
87 - LDFLAGS: linker flags
89 Both '-O2' and '-O3' are recognized as valid, even though only '-O2' is
92 It handles all file extensions as documented by gcc regarding preprocessing,
95 The architecture of the build log is automatically detected by looking for the
96 following line (output of dpkg-buildpackage):
98 dpkg-buildpackage: host architecture <architecture>
100 The available hardening flags are adapted to the architecture because some
101 architectures don't support certain hardening options.
107 The build log must contain the following line which marks the beginning of the
108 real compile process (output of dpkg-buildpackage):
110 dpkg-buildpackage: ...
112 If it's not present no compiler commands are detected. In case you don't use
113 dpkp-buildpackage but still want to check a build log adding it as first line
116 The following non-verbose builds can't be detected:
120 This is not detected because `test` has no file extension. A file extension is
121 required on a compiler line to prevent many false positives. As the build will
122 most likely contain other non-verbose build commands (e.g. `gcc test.c`) which
123 are correctly detected as non-verbose this shouldn't be a problem.
125 Some CMake non-verbose linker commands are also not correctly detected at the
128 blhc still creates a few false positives. Patches to fix them are very welcome
129 as long as they won't cause any false negatives.
135 Buildd mode is enabled if '--buildd' is used. It's designed to check build
136 logs from Debian's buildds.
138 Instead of normal warning messages only tags are printed at the end of the
139 check. See the man page for possible tags.
145 If you find any bugs not mentioned in this document please report them to
146 <simon@ruderich.org> with blhc in the subject.
152 Written by Simon Ruderich <simon@ruderich.org>.
154 Thanks to Bernhard R. Link <brlink@debian.org> and Jaria Alto
155 <jari.aalto@cante.net> for their valuable input and suggestions.
161 blhc is licensed under GPL version 3 or later.
163 Copyright (C) 2012 Simon Ruderich
165 This program is free software: you can redistribute it and/or modify
166 it under the terms of the GNU General Public License as published by
167 the Free Software Foundation, either version 3 of the License, or
168 (at your option) any later version.
170 This program is distributed in the hope that it will be useful,
171 but WITHOUT ANY WARRANTY; without even the implied warranty of
172 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
173 GNU General Public License for more details.
175 You should have received a copy of the GNU General Public License
176 along with this program. If not, see <http://www.gnu.org/licenses/>.