Annotation of wikisrc/pkgsrc/hardening.mdwn, revision 1.3
1.1 khorben 1: [[!meta title="Hardening pkgsrc"]]
2:
3: [pkgsrc](http://www.pkgsrc.org/) supports a number of mechanisms that are meant
4: to improve the security of compiled binaries. They can be individually enabled
5: in `mk.conf`, and consist of:
6:
7: * `PKGSRC_MKPIE`: forces the creation of PIE (Position Independent
8: Executables) when supported on the current platform. This option is necessary
9: to fully leverage ASLR as a mitigation for security vulnerabilities.
10: * `PKGSRC_USE_FORTIFY`: allows substitute wrappers to be used for commonly used
11: functions that do not bounds checking regularly - but could in some cases.
12: * `PKGSRC_USE_RELRO`: this also makes the exploitation of some security
13: vulnerabilities more difficult in some cases.
14: * `PKGSRC_USE_SSP`: enables stack-smashing protection (again, on supported
15: platforms)
16:
1.2 khorben 17: # Caveats
18:
19: ## Problems with `PKGSRC_MKPIE`
20:
21: ### No support for cwrappers
22:
23: As of the time of this article `PKGSRC_MKPIE` is not supported by
24: `pkgtools/cwrappers` (`USE_CWRAPPERS` in `mk.conf`).
25:
26: ### Packages failing to build
27:
28: A number of packages may fail to build with this option enabled. The failures
29: are often related to the absence of the "-fPIC" compilation flag when building
30: libraries or executables (or ideally "-fPIE" in the latter case). This flag is
31: added to the `CFLAGS` already, but requires the package to actually support it.
32:
33: #### How to fix
34:
35: These instructions are meant as a reference only; they likely need to be adapted
36: for many packages individually.
37:
38: For packages using `Makefiles`:
39:
40: MAKE_FLAGS+= CFLAGS=${CFLAGS:Q}
41: MAKE_FLAGS+= LDFLAGS=${LDFLAGS:Q}
42:
43: For packages using `Imakefiles`:
44:
45: MAKE_FLAGS+= CCOPTIONS=${CFLAGS:Q}
46: MAKE_FLAGS+= LOCAL_LDFLAGS=${LDFLAGS:Q}
47:
48: ### Run-time crashes
49:
50: Some programs may fail to run, or crash at random times once built as PIE. Two
51: scenarios are essentially possible:
52:
53: * actual bug in the program crashing, exposed thanks to ASLR/mprotect;
54: * bug in the implementation of ASLR/mprotect in the Operating System.
55:
1.3 ! khorben 56: ## Problems with `PKGSRC_USE_SSP`
! 57:
! 58: ### Packages failing to build
! 59:
! 60: The stack-smashing protection provided by this option does not work for some
! 61: programs. The two most common situations in which this happens are:
! 62:
! 63: * the program makes use of the `alloca(3)` library call (memory allocator on the
! 64: stack)
! 65: * the program allocates variables on the stack, with the size determined at
! 66: run-time.
! 67:
! 68: Both cases will require a modification to the program, or disabling this feature
! 69: for part or all of the build.
! 70:
! 71: ### Run-time crashes
! 72:
! 73: Just like with `PKGSRC_MKPIE` above, this feature may cause some programs to
! 74: crash, usually indicating an actual bug in the program. The fix will typically
! 75: involve patching the original program.
! 76:
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