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F-5606: don't enforce DTLS 1.3 2^48-1 epoch cap on the receive side #10627

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F-5606: don't enforce DTLS 1.3 2^48-1 epoch cap on the receive side #10627

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9 changes: 3 additions & 6 deletions src/tls13.c
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Original file line number Diff line number Diff line change
Expand Up @@ -12414,12 +12414,9 @@ static int DoTls13KeyUpdate(WOLFSSL* ssl, const byte* input, word32* inOutIdx,
w64wrapper newEpoch = ssl->dtls13PeerEpoch;
w64Increment(&newEpoch);

/* RFC 9147 Section 4.2.1: the epoch must not exceed 2^48-1. Reject a
* peer KeyUpdate that would advance the receiving epoch past the
* limit. Validate on a local copy so ssl->dtls13PeerEpoch is left
* untouched when the check fails. */
if (w64GT(newEpoch,
w64From32(DTLS13_EPOCH_MAX_HI32, DTLS13_EPOCH_MAX_LO32)))
/* RFC 9147 Section 8: the 2^48-1 cap is sender-only; receivers MUST
* NOT enforce it. Guard only the wrap-to-zero (Section 4.2.1). */
if (w64IsZero(newEpoch))
return BAD_STATE_E;

ssl->dtls13PeerEpoch = newEpoch;
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6 changes: 4 additions & 2 deletions wolfssl/internal.h
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Expand Up @@ -5950,8 +5950,10 @@ enum {
DTLS13_EPOCH_TRAFFIC0 = 3
};

/* RFC 9147 Section 4.2.1: the DTLS 1.3 epoch is a 48-bit value and must not
* exceed 2^48-1. Expressed as the high/low 32-bit halves of a w64wrapper. */
/* Sender-side DTLS 1.3 epoch ceiling: we MUST NOT advance our own epoch past
* 2^48-1 (RFC 9147 Section 4.2.1). This gates only the sending epoch; receivers
* MUST NOT enforce it on the peer epoch (RFC 9147 Section 8). Expressed as the
* high/low 32-bit halves of a w64wrapper. */
#define DTLS13_EPOCH_MAX_HI32 0x0000FFFFU
#define DTLS13_EPOCH_MAX_LO32 0xFFFFFFFFU

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