cgosqlite: add optional hook to verify ColumnBlob bytes are unmodified #124
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If a hook is given, then a `runtime.AddCleanup` is registered for the []byte returned from ColumnBlob that verifies whether it's been modified. If so, the hook function is called with the corresponding query. Also, add tests to confirm that this works as expected. Updates tailscale/corp#35671 Signed-off-by: Andrew Dunham <[email protected]>
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Not sure we want to do this, but @raggi mentioned this in Slack and I figured it'd be interesting to try out 😃 I'm going to run this commit against the full corp testsuite and see what happens. |
raggi
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Jan 7, 2026
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Yeah, I mean I'm not sure if we have a strong reason to believe this is where we need to dig but if we did this a sampling way (some portion of queries) it might give some signal.
bradfitz
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Jan 7, 2026
| // TODO: We use uintptr instead of []byte to avoid keeping the slice alive | ||
| // (which would prevent the cleanup from running); is that right? | ||
| type blobCheckArg struct { | ||
| original []byte // copy of original data |
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Or instead of this bytes.Clone, maybe store a https://pkg.go.dev/hash/fnv#New64a hash of the original data?
bradfitz
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Jan 7, 2026
| // can ensure they've run. | ||
| checkRun := make(chan struct{}, 10_000) // high enough to never block | ||
| blobCheckHook = func() { | ||
| checkRun <- struct{}{} |
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select {
case checkRun <- struct{}{}:
default:
panic("checkRun unexpectedly full")
}
bradfitz
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Jan 7, 2026
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If a hook is given, then a
runtime.AddCleanupis registered for the []byte returned from ColumnBlob that verifies whether it's been modified. If so, the hook function is called with the corresponding query. Also, add tests to confirm that this works as expected.Updates tailscale/corp#35671