jvz commented on a change in pull request #173:
URL: https://github.com/apache/mina-sshd/pull/173#discussion_r504049396
##########
File path:
sshd-common/src/main/java/org/apache/sshd/common/cipher/BaseGCMCipher.java
##########
@@ -78,19 +78,25 @@ public void update(byte[] input, int inputOffset, int
inputLen) throws Exception
*/
protected static class CounterGCMParameterSpec extends GCMParameterSpec {
protected final byte[] iv;
+ protected final long initialCounter;
protected CounterGCMParameterSpec(int tLen, byte[] src) {
super(tLen, src);
if (src.length != 12) {
throw new IllegalArgumentException("GCM nonce must be 12
bytes, but given len=" + src.length);
}
iv = src.clone();
+ initialCounter = BufferUtils.getLong(iv, iv.length - Long.BYTES,
Long.BYTES);
}
protected void incrementCounter() {
int off = iv.length - Long.BYTES;
long counter = BufferUtils.getLong(iv, off, Long.BYTES);
- BufferUtils.putLong(Math.addExact(counter, 1L), iv, off,
Long.BYTES);
+ long newCounter = counter + 1L;
+ if (newCounter == initialCounter) {
Review comment:
There doesn't seem to be any harm in adding this check, but the way that
SSH works would force a rekey event well before this counter would ever loop
back to where it started (rekey events happen far more often than every 2^64
packets).
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