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Merge pull request #1769 from SparkiDev/tls13_dh

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TLS 1.3: Always left-pad DH secret to length of prime
This commit is contained in:
toddouska
2018-08-20 09:13:50 -07:00
committed by GitHub
parent 3e08c27512 d104ae39e3
commit c8814a7ee1
1 changed files with 10 additions and 0 deletions
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10
src/tls.c
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@ -6385,6 +6385,16 @@ static int TLSX_KeyShare_ProcessDh(WOLFSSL* ssl, KeyShareEntry* keyShareEntry)
ret = wc_AsyncWait(ret, dhKey.asyncDev, WC_ASYNC_FLAG_NONE);
}
#endif
/* RFC 8446 Section 7.4.1:
* ... left-padded with zeros up to the size of the prime. ...
*/
if (params->p_len > ssl->arrays->preMasterSz) {
word32 diff = params->p_len - ssl->arrays->preMasterSz;
XMEMMOVE(ssl->arrays->preMasterSecret + diff,
ssl->arrays->preMasterSecret, ssl->arrays->preMasterSz);
XMEMSET(ssl->arrays->preMasterSecret, 0, diff);
ssl->arrays->preMasterSz = params->p_len;
}
wc_FreeDhKey(dhKey);
#ifdef WOLFSSL_SMALL_STACK