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revocation: fix integer underflow infinite loop bug in sha chain

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* `i := toDerive - 1` created an unsigned integer, the last loop
iteration subtracted from zero causing this to underflow creating an
infinite loop
* Instead, initialized `i` as an int, and cast to uint as needed
This commit is contained in:
Olaoluwa Osuntokun 2015-12-21 15:47:36 -06:00
parent d7fba0e89d
commit 06bad8ba42
1 changed files with 3 additions and 3 deletions
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6
revocation/shachain.go
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@ -72,11 +72,11 @@ func derive(from, to uint64, startingHash [32]byte) [32]byte {
numBranches := from ^ to
toDerive := uint64(math.Log2(float64(numBranches))) // uh.....
for i := toDerive - 1; i >= 0; i-- {
if (numBranches>>i)&1 == 1 {
for i := int(toDerive - 1); i >= 0; i-- {
if (numBranches>>uint(i))&1 == 1 {
// Flip the ith bit, then hash the current state to
// advance down the tree.
nextHash[i/8] ^= (1 << (i % 8))
nextHash[i/8] ^= (1 << (uint(i) % 8))
nextHash = sha256.Sum256(nextHash[:])
}
}