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From 3be810287878138e5f72568d1ba1160b5bad22f8 Mon Sep 17 00:00:00 2001
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From: "Daniel P. Berrange" <berrange@redhat.com>
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Date: Thu, 8 Feb 2018 17:50:32 +0100
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Subject: [PATCH 18/27] ui: track how much decoded data we consumed when doing
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 SASL encoding
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MIME-Version: 1.0
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Content-Type: text/plain; charset=UTF-8
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Content-Transfer-Encoding: 8bit
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RH-Author: Daniel P. Berrange <berrange@redhat.com>
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Message-id: <20180208175041.5634-19-berrange@redhat.com>
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Patchwork-id: 78951
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O-Subject: [RHEL-7.5 qemu-kvm PATCH v1 18/27] ui: track how much decoded data we consumed when doing SASL encoding
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Bugzilla: 1527405
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RH-Acked-by: Laszlo Ersek <lersek@redhat.com>
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RH-Acked-by: Gerd Hoffmann <kraxel@redhat.com>
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RH-Acked-by: Miroslav Rezanina <mrezanin@redhat.com>
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From: "Daniel P. Berrange" <berrange@redhat.com>
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When we encode data for writing with SASL, we encode the entire pending output
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buffer. The subsequent write, however, may not be able to send the full encoded
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data in one go though, particularly with a slow network. So we delay setting the
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output buffer offset back to zero until all the SASL encoded data is sent.
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Between encoding the data and completing sending of the SASL encoded data,
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however, more data might have been placed on the pending output buffer. So it
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is not valid to set offset back to zero. Instead we must keep track of how much
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data we consumed during encoding and subtract only that amount.
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With the current bug we would be throwing away some pending data without having
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sent it at all. By sheer luck this did not previously cause any serious problem
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because appending data to the send buffer is always an atomic action, so we
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only ever throw away complete RFB protocol messages. In the case of frame buffer
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updates we'd catch up fairly quickly, so no obvious problem was visible.
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RHEL-7 note: context difference in the last argument to
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vnc_client_io_error() due to downstream lacking commit 04d2529da27d
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("ui: convert VNC server to use QIOChannelSocket", 2015-12-18).
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Signed-off-by: Daniel P. Berrange <berrange@redhat.com>
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Reviewed-by: Darren Kenny <darren.kenny@oracle.com>
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Reviewed-by: Marc-André Lureau <marcandre.lureau@redhat.com>
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Message-id: 20171218191228.31018-6-berrange@redhat.com
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Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>
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(cherry picked from commit 8f61f1c5a6bc06438a1172efa80bc7606594fa07)
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Signed-off-by: Miroslav Rezanina <mrezanin@redhat.com>
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---
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 ui/vnc-auth-sasl.c | 3 ++-
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 ui/vnc-auth-sasl.h | 1 +
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 2 files changed, 3 insertions(+), 1 deletion(-)
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diff --git a/ui/vnc-auth-sasl.c b/ui/vnc-auth-sasl.c
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index f3ad75d..804b8e7 100644
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--- a/ui/vnc-auth-sasl.c
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+++ b/ui/vnc-auth-sasl.c
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@@ -64,6 +64,7 @@ long vnc_client_write_sasl(VncState *vs)
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         if (err != SASL_OK)
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             return vnc_client_io_error(vs, -1, EIO);
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+        vs->sasl.encodedRawLength = vs->output.offset;
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         vs->sasl.encodedOffset = 0;
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     }
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@@ -75,7 +76,7 @@ long vnc_client_write_sasl(VncState *vs)
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     vs->sasl.encodedOffset += ret;
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     if (vs->sasl.encodedOffset == vs->sasl.encodedLength) {
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-        vs->output.offset = 0;
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+        vs->output.offset -= vs->sasl.encodedRawLength;
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         vs->sasl.encoded = NULL;
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         vs->sasl.encodedOffset = vs->sasl.encodedLength = 0;
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     }
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diff --git a/ui/vnc-auth-sasl.h b/ui/vnc-auth-sasl.h
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index 8091d68..4ec6fb5 100644
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--- a/ui/vnc-auth-sasl.h
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+++ b/ui/vnc-auth-sasl.h
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@@ -54,6 +54,7 @@ struct VncStateSASL {
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      */
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     const uint8_t *encoded;
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     unsigned int encodedLength;
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+    unsigned int encodedRawLength;
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     unsigned int encodedOffset;
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     char *username;
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     char *mechlist;
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-- 
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1.8.3.1
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