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package org.bouncycastle.tls;

/**
 * RFC 4347 4.1.2.5 Anti-replay
 * 

* Support fast rejection of duplicate records by maintaining a sliding receive window *

*/ class DTLSReplayWindow { private static final long VALID_SEQ_MASK = 0x0000FFFFFFFFFFFFL; private static final long WINDOW_SIZE = 64L; private long latestConfirmedSeq = -1; private long bitmap = 0; /** * Check whether a received record with the given sequence number should be rejected as a duplicate. * * @param seq the 48-bit DTLSPlainText.sequence_number field of a received record. * @return true if the record should be discarded without further processing. */ boolean shouldDiscard(long seq) { if ((seq & VALID_SEQ_MASK) != seq) { return true; } if (seq <= latestConfirmedSeq) { long diff = latestConfirmedSeq - seq; if (diff >= WINDOW_SIZE) { return true; } if ((bitmap & (1L << diff)) != 0) { return true; } } return false; } /** * Report that a received record with the given sequence number passed authentication checks. * * @param seq the 48-bit DTLSPlainText.sequence_number field of an authenticated record. */ boolean reportAuthenticated(long seq) { if ((seq & VALID_SEQ_MASK) != seq) { throw new IllegalArgumentException("'seq' out of range"); } if (seq <= latestConfirmedSeq) { long diff = latestConfirmedSeq - seq; if (diff < WINDOW_SIZE) { bitmap |= (1L << diff); } return false; } else { long diff = seq - latestConfirmedSeq; if (diff >= WINDOW_SIZE) { bitmap = 1; } else { bitmap <<= (int)diff; // for earlier JDKs bitmap |= 1; } latestConfirmedSeq = seq; return true; } } void reset(long seq) { if ((seq & VALID_SEQ_MASK) != seq) { throw new IllegalArgumentException("'seq' out of range"); } // Discard future records unless sequence number > 'seq' latestConfirmedSeq = seq; bitmap = -1L >>> Math.max(0, 63 - seq); } }




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