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Cap the scrypt cost parameter to avoid OOM.

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akwizgran
2021-02-08 11:32:03 +00:00
parent 6e3a7d8d0c
commit d796eff0f6
1 changed files with 14 additions and 2 deletions
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16
bramble-core/src/main/java/org/briarproject/bramble/crypto/ScryptKdf.java
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@@ -9,14 +9,16 @@ import java.util.logging.Logger;
import javax.inject.Inject;
import static java.lang.Math.min;
import static java.util.logging.Level.INFO;
import static java.util.logging.Logger.getLogger;
import static org.briarproject.bramble.util.LogUtils.logDuration;
import static org.briarproject.bramble.util.LogUtils.now;
class ScryptKdf implements PasswordBasedKdf {
private static final Logger LOG =
Logger.getLogger(ScryptKdf.class.getName());
getLogger(ScryptKdf.class.getName());
private static final int MIN_COST = 256; // Min parameter N
private static final int MAX_COST = 1024 * 1024; // Max parameter N
@@ -33,10 +35,20 @@ class ScryptKdf implements PasswordBasedKdf {
@Override
public int chooseCostParameter() {
// Scrypt uses at least 128 * N * r bytes of memory. Don't use more
// than half of the JVM's max heap size or we may run out of memory.
// https://blog.filippo.io/the-scrypt-parameters/
long maxMemory = Runtime.getRuntime().maxMemory();
long maxCost = min(MAX_COST, maxMemory / BLOCK_SIZE / 256);
if (LOG.isLoggable(INFO) && maxCost < MAX_COST) {
LOG.info("Max cost capped at " + maxCost
+ " due to max heap size " + maxMemory);
}
// Increase the cost from min to max while measuring performance
int cost = MIN_COST;
while (cost * 2 <= MAX_COST && measureDuration(cost) * 2 <= TARGET_MS)
while (cost * 2 <= maxCost && measureDuration(cost) * 2 <= TARGET_MS) {
cost *= 2;
}
if (LOG.isLoggable(INFO))
LOG.info("KDF cost parameter " + cost);
return cost;