bitcoin: don't dereference a NULL transaction from a truncated block - #9485
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kwsantiago wants to merge 1 commit into
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bitcoin: don't dereference a NULL transaction from a truncated block#9485kwsantiago wants to merge 1 commit into
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pull_bitcoin_tx_only() returns NULL once the cursor runs out, and the next line writes through it, so a block that ends mid-transaction segfaults lightningd instead of being rejected. The block comes from the chain backend via getrawblockbyheight, so this needs a bitcoind serving a malformed or unparseable block rather than anything a peer can send. Test walks every truncation of the existing test block; it segfaults at 162 bytes without the fix.
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pull_bitcoin_tx_only()returns NULL once the cursor runs out, and the next line writes through it:So a block that ends part-way through a transaction segfaults lightningd rather than being rejected by the
if (!p || len)check a few lines below, which never runs.Reproducer, on master with no other changes: truncating the block already in
run-bitcoin_block_from_hexto 162 bytes is enough.The block arrives from the chain backend through
getrawblockbyheight, so triggering it needs a bitcoind serving a malformed or otherwise unparseable block, not anything a peer can send. It is a crash on bad input from a trusted component rather than a remotely reachable issue, which is why this is a normal pull request.The fix returns NULL the way every other parse failure in this function does. The test walks every truncation of the existing test block, so it covers the header boundary and each transaction boundary rather than one hand-picked length.