File:  [NetBSD Developer Wiki] / wikisrc / users / maya.mdwn
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Thu Feb 16 00:06:15 2017 UTC (4 years, 9 months ago) by maya
Branches: MAIN
CVS tags: HEAD
Improve markdown, mention conflict with ASLR.

    1: # Tips for using analyzers on NetBSD #
    2: 
    3: ## Address Sanitizer (+UBsan) (preliminary) ##
    4: 
    5: ASan reports memory violations, and detects many off-by-ones. It seems
    6: to produce very high quality reports.
    7: 
    8: It only needs to be compiled on the resulting binary[1]. It cannot compile
    9: static objects so requires some fiddling with makefiles to disable those.
   10: 
   11: I've been running it on netbsd tests in the following manner[2]:
   12: 
   13:     cd /usr/src/tests/lib/libc
   14:     env USETOOLS=never MK_SSP=no HAVE_SSP=no CFLAGS="-fno-omit-frame-pointer -O0 -g -ggdb -U_FORTIFY_SOURCE -fsanitize=address -fsanitize=undefined" LDFLAGS="-lasan -lubsan" make -j20
   15: 
   16:     env ASAN_OPTIONS=alloc_dealloc_mismatch=0 LD_PRELOAD="/usr/lib/libasan.so /usr/lib/libubsan.so" atf-run
   17: 
   18:     sysctl -w security.pax.aslr.enabled=0 # [3]
   19: 
   20: 1. Seems like this is a cause of worse reports, as in-library functions
   21: are not intercepted.
   22: 
   23: 2. Not even close to canonical commands, should probably be improved.
   24: 
   25: 3. To workaround "Shadow memory range interleaves with an existing memory mapping. ASan cannot proceed correctly". An alternative is to LD_PRELOAD and LD_LIBRARY_PATH an entirely separate libc, ld.elf_so, etc.
   26: 
   27: 4. ASAN_OPTIONS=alloc_dealloc_mismatch=0 is because atf-run itself
   28:     triggers a bug. Should have a look at it so this option doesn't
   29:     need to be disabled.
   30: 
   31: Important note: ASan should not be run on production systems. [It can pose a
   32: security risk](http://www.openwall.com/lists/oss-security/2016/02/17/9).
   33: 
   34: ## Coverity ##
   35: 
   36: Coverity is a static analyzer.
   37: 
   38: You can see a part of its output in coverity-updates@, and a lot more
   39: if you go to the website (sign up with your netbsd email or poke someone
   40: for access).
   41: 
   42: A lot of the reports are about strncpy/strcpy or in code that belongs
   43: to GCC (in the case of userland), you can tackle this by limiting
   44: results to a particular directory (click the folder icon). You can
   45: also sort by issue.
   46: 
   47: Some suggestions for things to focus on, as there are many defects
   48: reported:
   49: - Setuid programs
   50: - Anything kernel
   51: - Stuff that runs as root
   52: - Library or other code you know well already
   53: - Drivers for hardware you actually own and can test
   54: 
   55: Future ideas:
   56: 
   57: - GCC could be told to add ASan flags for all shared objects, making it easier to build world with those flags
   58: - We could run all of NetBSD with ASan for some real world tests.
   59: - ASan for kernel? (subr_kmem.c has some flags which do some of the work, could it do more?)
   60: - Fuzzers are cool.

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