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 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 From 15beb4b193b2714d88107e7dffca781798684e7e Mon Sep 17 00:00:00 2001 From: Daiki Ueno Date: Fri, 29 Jan 2021 14:06:32 +0100 Subject: [PATCH] key_share: avoid use-after-free around realloc Signed-off-by: Daiki Ueno --- lib/ext/key_share.c | 12 +++++------- 1 file changed, 5 insertions(+), 7 deletions(-) diff --git a/lib/ext/key_share.c b/lib/ext/key_share.c index ab8abf8fe6..a8c4bb5cff 100644 --- a/lib/ext/key_share.c +++ b/lib/ext/key_share.c @@ -664,14 +664,14 @@ key_share_send_params(gnutls_session_t session, { unsigned i; int ret; - unsigned char *lengthp; - unsigned int cur_length; unsigned int generated = 0; const gnutls_group_entry_st *group; const version_entry_st *ver; /* this extension is only being sent on client side */ if (session->security_parameters.entity == GNUTLS_CLIENT) { + unsigned int length_pos; + ver = _gnutls_version_max(session); if (unlikely(ver == NULL || ver->key_shares == 0)) return 0; @@ -679,16 +679,13 @@ key_share_send_params(gnutls_session_t session, if (!have_creds_for_tls13(session)) return 0; - /* write the total length later */ - lengthp = &extdata->data[extdata->length]; + length_pos = extdata->length; ret = _gnutls_buffer_append_prefix(extdata, 16, 0); if (ret < 0) return gnutls_assert_val(ret); - cur_length = extdata->length; - if (session->internals.hsk_flags & HSK_HRR_RECEIVED) { /* we know the group */ group = get_group(session); if (unlikely(group == NULL)) @@ -736,7 +733,8 @@ key_share_send_params(gnutls_session_t session, } /* copy actual length */ - _gnutls_write_uint16(extdata->length - cur_length, lengthp); + _gnutls_write_uint16(extdata->length - length_pos - 2, + &extdata->data[length_pos]); } else { /* server */ ver = get_version(session); -- GitLab