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From add9b794b9dc697a1b52115c997fcfb6e06bf64c Mon Sep 17 00:00:00 2001
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From: Eric Blake <eblake@redhat.com>
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Date: Mon, 16 Aug 2021 13:43:29 -0500
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Subject: [PATCH] server: reset meta context replies on starttls
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Related to CVE-2021-3716, but not as severe. No compliant client will
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send NBD_CMD_BLOCK_STATUS unless it first negotiates
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NBD_OPT_SET_META_CONTEXT. If an attacker injects a premature
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SET_META_CONTEXT, either the client will never notice (because it
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never uses BLOCK_STATUS), or the client will overwrite the attacker's
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attempt with the client's own SET_META_CONTEXT request after
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encryption is enabled. So I don't class this as having the potential
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to trigger denial-of-service due to any protocol mismatch between
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compliant client and server (I don't care what happens with
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non-compliant clients).
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Fixes: 26455d45 (server: protocol: Implement Block Status "base:allocation".)
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(cherry picked from commit 6c5faac6a37077cf2366388a80862bb00616d0d8)
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(cherry picked from commit 814d8103fb4b581dc01dfd25d2cd81596576f211)
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---
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server/protocol-handshake-newstyle.c | 3 +++
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1 file changed, 3 insertions(+)
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diff --git a/server/protocol-handshake-newstyle.c b/server/protocol-handshake-newstyle.c
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index b94950e2..eb0f3961 100644
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--- a/server/protocol-handshake-newstyle.c
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+++ b/server/protocol-handshake-newstyle.c
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@@ -497,6 +497,9 @@ negotiate_handshake_newstyle_options (void)
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debug ("using TLS on this connection");
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/* Wipe out any cached state. */
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conn->structured_replies = false;
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+ free (conn->exportname_from_set_meta_context);
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+ conn->exportname_from_set_meta_context = NULL;
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+ conn->meta_context_base_allocation = false;
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for_each_backend (b) {
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struct handle *h = get_handle (conn, b->i);
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free (h->default_exportname);
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--
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2.31.1
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