fix: race in Diff mode crashes Hoverfly (GHSA-qrh4-p6v4-mrfg)#1227
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Diff mode's responsesDiff map had no synchronization, so concurrent proxy requests tripped Go's built-in concurrent-map check and crashed the process with "fatal error: concurrent map read and map write". Add a dedicated sync.RWMutex covering AddDiff, ClearDiff, GetDiff, and GetFilteredDiff. GetDiff now returns a deep snapshot so DiffHandler can iterate the result outside the lock without re-introducing the race. Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>
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Summary
fatal error: concurrent map read and map writeunder concurrent proxy traffic becauseresponsesDiff(incore/hoverfly.go) was a plainmapwith no synchronization. Trivially triggerable: any client with proxy access could send a handful of simultaneous requests and DoS the process. Reported as GHSA-qrh4-p6v4-mrfg.sync.RWMutexnext toresponsesDiff(mirroring thestate.Statepattern) and wrapped all four accessors:AddDiff/ClearDiff(write lock),GetDiff/GetFilteredDiff(read lock).GetDiffnow returns a deep snapshot soDiffHandler.convertToResponseDiffViewcan iterate the result after the lock is released without reintroducing the race.Test plan
go test -race -count=1 -v -run 'Test_Hoverfly_AddDiff|Test_Hoverfly_Diff_ConcurrentAccess|Test_Hoverfly_processRequest_CanHandleResponseDiff' github.com/SpectoLabs/hoverfly/core— all green.Test_Hoverfly_Diff_ConcurrentAccess(32 writer goroutines × 64 readers × 1 clearer × 100 iterations each) — reliably trips Go's map-race check on pre-patch code; passes under-racewith the patch (~110 ms).go vet github.com/SpectoLabs/hoverfly/core— clean.🤖 Generated with Claude Code