dhcpv6: don't treat zero option as an end-of-payload marker #18625
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nmeum
requested review from
miri64,
haukepetersen,
PeterKietzmann and
cgundogan
as code owners
benpicco
approved these changes
Sep 22, 2022
benpicco
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CI: ready for build
As far as I can tell, no DHCPv6 RFC specifies this option. The handling for the zero option was added in RIOT-OS#17736 by @benpicco to fix issues encountered while trying to retrieve a DHCHPv6 lease. However, I strongly suspect that the zero option was encountered in this case due to an out-of-bounds read performed in RIOT's DHCPv6 client implementation (i.e. the option parsing loop read beyond the packet bounds). This issue was fixed in RIOT-OS#18307 and I strongly suspect that it should also fix the issue @benpicco originally encountered in RIOT-OS#17736. As such, I propose that we remove the if statement which treats the zero option as an end-of-payload marker. Fixes RIOT-OS#18309
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Contribution description
As far as I can tell, no DHCPv6 RFC specifies this option.
The handling for the zero option was added in #17736 by @benpicco to fix issues encountered while trying to retrieve a DHCHPv6 lease. However, I strongly suspect that the zero option was encountered in this case due to an out-of-bounds read performed in RIOT's DHCPv6 client implementation (i.e. the option parsing loop read beyond the packet bounds). This issue was fixed in #18307 and I strongly suspect that it should also fix the issue @benpicco originally encountered in #17736. As such, I propose that we remove the if statement which treats the zero option as an end-of-payload marker.
Testing procedure
@benpicco could you test this with the DHCPv6 server implementation with which you originally encountered the error described in #17736 and report back if you still encounter this error with this PR applied? 🙏
Issues/PRs references
Fixes #18309