face: validate NDNLPv2 fragmentation fields before reassembly - #216
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A single incoming NDNLPv2 frame carries attacker-controlled FragCount and FragIndex values that were trusted before allocation: - reassemble() sized its buffer with make(enc.Wire, fragCount), so one small fragment with a huge FragCount forces a proportional memory allocation (e.g. FragCount=1<<40 would exhaust memory). - handleIncomingFrame computed baseSequence = Sequence - FragIndex before validation, underflowing to a huge sequence number when FragIndex > Sequence and polluting a reassembly slot. Reject frames with FragCount == 0, FragCount above the maximum possible for a legal packet (MaxNDNPacketSize, since every fragment carries at least one byte), FragIndex >= FragCount, or FragIndex > Sequence before any reassembly state is allocated. The ring buffer introduced in named-data#96 bounds the number of concurrent reassemblies but not their size.
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Fixes #215
What
FragCount == 0,FragCount > MaxNDNPacketSize,FragIndex >= FragCount,FragIndex > Sequence) inhandleIncomingFramebeforebaseSequenceis computed, and re-check the bounds inreassemblebefore allocating.FragCountno longer allocates;FragIndex > Sequenceno longer underflows or allocates; a normal 2-fragment packet still reassembles and frees its buffer.Evidence
Before (on main):
After (this branch):
Full
go test ./...green.