194 lines
6.5 KiB
Diff
194 lines
6.5 KiB
Diff
From ae3fb4def811f5bc42563128e8fae0a4288584d1 Mon Sep 17 00:00:00 2001
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From: "Richard W.M. Jones" <rjones@redhat.com>
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Date: Tue, 13 Jun 2023 20:01:05 +0100
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Subject: [PATCH 03/15] tar: Implement tar-limit
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This can be used to ensure that the tar filter does not read
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indefinite amounts of input when opening the tar file.
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See: https://github.com/kubevirt/containerized-data-importer/pull/2748#issuecomment-1589852102
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---
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filters/tar/nbdkit-tar-filter.pod | 24 +++++++++++-
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tests/Makefile.am | 2 +
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filters/tar/tar.c | 10 +++++
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tests/test-tar-limit.sh | 65 +++++++++++++++++++++++++++++++
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4 files changed, 99 insertions(+), 2 deletions(-)
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create mode 100755 tests/test-tar-limit.sh
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diff --git a/filters/tar/nbdkit-tar-filter.pod b/filters/tar/nbdkit-tar-filter.pod
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index eb0cfd4ab..a3c2d1328 100644
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--- a/filters/tar/nbdkit-tar-filter.pod
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+++ b/filters/tar/nbdkit-tar-filter.pod
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@@ -4,8 +4,9 @@ nbdkit-tar-filter - read and write files inside tar files without unpacking
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=head1 SYNOPSIS
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- nbdkit file FILENAME.tar --filter=tar tar-entry=PATH_INSIDE_TAR
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- [tar=TAR_COMMAND]
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+ nbdkit file FILENAME.tar
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+ --filter=tar tar-entry=PATH_INSIDE_TAR
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+ [tar=TAR_COMMAND] [tar-limit=SIZE]
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=head1 EXAMPLES
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@@ -83,6 +84,25 @@ The path of the file inside the tarball to serve. This parameter is
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required. It must exactly match the name stored in the tarball, so
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use S<C<tar tf filename.tar>>
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+=item [B<tar-limit=>]SIZE
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+
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+When opening the tar file we have to locate the file (C<tar-entry>)
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+inside the tarball. Because tar files do not have a central index we
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+must iterate over the tar file to find the entry, and that may be
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+costly (especially with untrusted tar files). In the worst case where
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+C<tar-entry> starts near the end of the file we may have to iterate
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+over the whole tar file. If this is a problem you may set
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+C<tar-limit> to some smaller value, eg:
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+
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+ nbdkit -r curl https://example.com/file.tar \
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+ --filter=tar tar-entry=disk.img \
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+ tar-limit=10M
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+
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+which ensures no more than 10 megabytes are read before we give up and
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+reject the tar file (sending an error back to the NBD client).
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+
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+The default is 0 meaning no limit.
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+
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=item B<tar=gtar>
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=item B<tar=>/PATH/TO/GTAR
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diff --git a/tests/Makefile.am b/tests/Makefile.am
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index 6694e409e..f2912aa93 100644
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--- a/tests/Makefile.am
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+++ b/tests/Makefile.am
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@@ -1957,11 +1957,13 @@ TESTS += \
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test-tar.sh \
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test-tar-info.sh \
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test-tar-info-xz.sh \
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+ test-tar-limit.sh \
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$(NULL)
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EXTRA_DIST += \
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test-tar.sh \
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test-tar-info.sh \
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test-tar-info-xz.sh \
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+ test-tar-limit.sh \
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$(NULL)
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# truncate filter tests.
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diff --git a/filters/tar/tar.c b/filters/tar/tar.c
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index f3adb2c46..efe47684d 100644
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--- a/filters/tar/tar.c
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+++ b/filters/tar/tar.c
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@@ -53,6 +53,7 @@
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#include "utils.h"
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static const char *entry; /* File within tar (tar-entry=...) */
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+static int64_t tar_limit = 0;
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static const char *tar_program = "tar";
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/* Offset and size within tarball.
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@@ -76,6 +77,12 @@ tar_config (nbdkit_next_config *next, nbdkit_backend *nxdata,
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entry = value;
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return 0;
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}
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+ else if (strcmp (key, "tar-limit") == 0) {
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+ tar_limit = nbdkit_parse_size (value);
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+ if (tar_limit == -1)
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+ return -1;
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+ return 0;
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+ }
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else if (strcmp (key, "tar") == 0) {
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tar_program = value;
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return 0;
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@@ -98,6 +105,7 @@ tar_config_complete (nbdkit_next_config_complete *next,
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#define tar_config_help \
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"tar-entry=<FILENAME> (required) The path inside the tar file to serve.\n" \
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+ "tar-limit=SIZE Limit on reading to find entry.\n" \
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"tar=<PATH> Path of the tar binary."
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static int
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@@ -197,6 +205,8 @@ calculate_offset_of_entry (nbdkit_next *next)
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copysize = next->get_size (next);
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if (copysize == -1)
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return -1;
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+ if (tar_limit > 0 && copysize > tar_limit)
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+ copysize = tar_limit;
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/* Run the tar command. */
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nbdkit_debug ("%s", cmd);
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diff --git a/tests/test-tar-limit.sh b/tests/test-tar-limit.sh
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new file mode 100755
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index 000000000..168f2c497
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--- /dev/null
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+++ b/tests/test-tar-limit.sh
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@@ -0,0 +1,65 @@
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+#!/usr/bin/env bash
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+# nbdkit
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+# Copyright Red Hat
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+#
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+# Redistribution and use in source and binary forms, with or without
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+# modification, are permitted provided that the following conditions are
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+# met:
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+#
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+# * Redistributions of source code must retain the above copyright
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+# notice, this list of conditions and the following disclaimer.
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+#
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+# * Redistributions in binary form must reproduce the above copyright
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+# notice, this list of conditions and the following disclaimer in the
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+# documentation and/or other materials provided with the distribution.
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+#
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+# * Neither the name of Red Hat nor the names of its contributors may be
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+# used to endorse or promote products derived from this software without
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+# specific prior written permission.
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+#
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+# THIS SOFTWARE IS PROVIDED BY RED HAT AND CONTRIBUTORS ''AS IS'' AND
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+# ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO,
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+# THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A
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+# PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL RED HAT OR
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+# CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
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+# SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
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+# LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF
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+# USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
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+# ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
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+# OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
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+# OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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+# SUCH DAMAGE.
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+
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+# Test the tar filter and tar-limit filter.
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+
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+source ./functions.sh
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+set -e
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+set -x
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+
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+requires test -f disk
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+requires tar --version
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+requires test -f disk
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+requires_nbdinfo
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+
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+tar_bad=tar-limit-bad.tar
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+tar_good=tar-limit-good.tar
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+tar_filler=tar-limit-filler.img
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+files="$tar_bad $tar_good $tar_filler"
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+rm -f $files
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+cleanup_fn rm -f $files
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+
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+# Create two tar files, one where the disk is located before an
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+# arbitrary boundary and one after.
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+truncate -s 1M $tar_filler
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+tar cf $tar_good disk
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+tar cf $tar_bad $tar_filler disk
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+
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+# Check we can read the good disk and reject the bad disk.
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+cmd="nbdkit -U - file --filter=tar tar-entry=disk tar-limit=131072"
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+
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+$cmd $tar_good --run 'nbdinfo "$uri"'
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+
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+if $cmd $tar_bad --run 'nbdinfo "$uri"' ; then
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+ echo "ERROR: $0: expected $tar_bad to fail"
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+ exit 1
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+fi
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--
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2.41.0
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