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Fix resumption after HRR

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Commit 6b1bb98fa moved the processing of ClientHello extensions into the
state machine post-processing stage. After processing s->init_num is reset
to 0, so by post-processing we cannot rely on its value. Unfortunately we
were using it to handle the PSK extension. This causes the handshake to
fail.

We were using init_num to figure out the length of ClientHello2 so we can
remove it from the handshake_buffer. The handshake_buffer holds the
transcript of all the messages sent so far. For PSK processing though we
only want to add in a partial ClientHello2. This commit changes things so
we just work out where ClientHello2 starts, working forward from the
beginning of handshake_buffer.

Fixes #2983

Reviewed-by: Rich Salz <rsalz@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/2996)
(cherry picked from commit 77815a026c)
This commit is contained in:
Matt Caswell 2017-03-20 18:03:34 +00:00
parent 7baabf45c4
commit 2c7e64564c
1 changed files with 9 additions and 2 deletions
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11
ssl/statem/extensions.c
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@ -1191,11 +1191,18 @@ int tls_psk_do_binder(SSL *s, const EVP_MD *md, const unsigned char *msgstart,
* ClientHello - which we don't want - so we need to take that bit off.
*/
if (s->server) {
if (hdatalen < s->init_num + SSL3_HM_HEADER_LENGTH) {
PACKET hashprefix, msg;
/* Find how many bytes are left after the first two messages */
if (!PACKET_buf_init(&hashprefix, hdata, hdatalen)
|| !PACKET_forward(&hashprefix, 1)
|| !PACKET_get_length_prefixed_3(&hashprefix, &msg)
|| !PACKET_forward(&hashprefix, 1)
|| !PACKET_get_length_prefixed_3(&hashprefix, &msg)) {
SSLerr(SSL_F_TLS_PSK_DO_BINDER, ERR_R_INTERNAL_ERROR);
goto err;
}
hdatalen -= s->init_num + SSL3_HM_HEADER_LENGTH;
hdatalen -= PACKET_remaining(&hashprefix);
}
if (EVP_DigestUpdate(mctx, hdata, hdatalen) <= 0) {