e4d99eb9b0
This commits adds a basic infrastructure to support Address Space Randomization (ASR). In a nutshell, using the already imported ASR LLVM pass, multiple versions can be generated for the same system service, each with a randomized, different address space layout. Combined with the magic instrumentation for state transfer, a system service can be live updated into another ASR-randomized version at runtime, thus providing live rerandomization. Since MINIX3 is not yet capable of running LLVM linker passes, the ASR-randomized service binaries have to be pregenerated during crosscompilation. These pregenerated binaries can then be cycled through at runtime. This patch provides the basic proof-of-concept infrastructure for both these parts. In order to support pregeneration, the clientctl host script has been extended with a "buildasr" command. It is to be used after building the entire system with bitcode and magic support, and will produce a given number of ASR-randomized versions of all system services. These services are placed in /usr/service/asr in the image that is generated as final step by the "buildasr" command. In order to support runtime updating, a new update_asr(8) command has been added to MINIX3. This command attempts to live-update the running system services into their next ASR-randomized versions. For now, this command is not run automatically, and thus must be invoked manually. Technical notes: - For various reasons, magic instrumentation is x86-only for now, and ASR functionality is therefore to be used on x86 only as well. - The ASR-randomized binaries are placed in numbered subdirectories so as not to have to change their actual program names, which are assumed to be static in various places (system.conf, procfs). - The root partition is typically too small to contain all the produced binaries, which is why we introduce /usr/service. There is a symlink from /service/asr to /usr/service/asr for no other reason than to let userland continue to assume that all services are reachable through /service. - The ASR count field (r_asr_count/ASRcount) maintained by RS is not used within RS in any way; it is only passed through procfs to userland in order to allow update_asr(8) to keep track of which version is currently loaded without having to maintain own state. - Ideally, pre-instrumentation linking of a service would remove all its randomized versions. Currently, the user is assumed not to perform ASR instrumentation and then recompile system services without performing ASR instrumentation again, as the randomized binaries included in the image would then be stale. This aspect has to be improved later. - Various other issues are flagged in the comments of the various parts of this patch. Change-Id: I093ad57f31c18305591f64b2d491272288aa0937
52 lines
1.5 KiB
Groff
52 lines
1.5 KiB
Groff
.Dd September 7, 2015
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.Dt UPDATE_ASR 8
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.Os
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.Sh NAME
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.Nm update_asr
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.Nd perform ASR rerandomization on system services
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.Sh SYNOPSYS
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.Nm
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.Op Fl v
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.Op Ar labels
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.Sh DESCRIPTION
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The
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.Nm
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utility performs one cycle of system service live
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ASR (Address Space Randomization) rerandomization.
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By default, the utility will attempt to update all system services.
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If a space-separated list of service
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.Ar labels
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is given, only those services are updated.
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.Pp
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Updates require the presence of at least two precreated ASR binaries for the
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service: the original service binary, and at least one rerandomized ASR binary
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for the service.
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The update consists of selecting the next on-disk ASR binary for the service,
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and performing a live update from the current service into the selected new
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version.
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The selection takes place in a round-robin fashion, so once the script has
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gone through all rerandomized ASR binaries, it will revert to the original
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service binary, and then continue with the first rerandomized ASR binary
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again, and so on.
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.Pp
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The following options are available:
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.Bl -tag -width Ds
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.It Fl v
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Enable verbose mode.
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.El
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.Sh SEE ALSO
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.Xr service 8
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.Sh AUTHORS
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The
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.Nm
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utility was written by
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.An David van Moolenbroek
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.Aq david@minix3.org .
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.Sh BUGS
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Failures are silently ignored.
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Some failures are expected, since not all services are necessarily quiescent
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and therefore ready to be updated.
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.Pp
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As of writing, no infrastructure exists to perform ASR updates automatically,
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and no infrastructure exists to create new rerandomized binaries at runtime.
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