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!14 [sync] PR-8: Add --bind-fd and --ro-bind-fd to let you bind a O_PATH fd for flatpak fix CVE-2024-42472

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From: @openeuler-sync-bot 
Reviewed-by: @overweight 
Signed-off-by: @overweight
This commit is contained in:
openeuler-ci-bot 2024-08-20 02:18:47 +00:00 committed by Gitee
commit 48df42482b
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2 changed files with 120 additions and 1 deletions
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115
backport-Add--bind-fd-and--ro-bind-fd-to-let-you-bind-a-O_PATH-fd.patch Normal file
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@ -0,0 +1,115 @@
From a253257cd298892da43e15201d83f9a02c9b58b5 Mon Sep 17 00:00:00 2001
From: Alexander Larsson <alexl@redhat.com>
Date: Tue, 18 Jun 2024 10:20:36 +0200
Subject: [PATCH] Add --bind-fd and --ro-bind-fd to let you bind a O_PATH fd.
Origin: https://github.com/containers/bubblewrap/commit/a253257cd298892da43e15201d83f9a02c9b58b5
This is useful for example if you for some reason don't have the real
path. It is also a way to make bind-mounts race-free (i.e. to have the
mount actually be the thing you wanted to be mounted, avoiding issues
where some other process replaces the target in parallel with the bwrap
launch.
Unfortunately due to some technical details we can't actually directly
mount the dirfd, as they come from different user namespace which is not
permitted, but at least we can delay resolving the fd to a path as much as
possible, and then validate after mount that we actually mounted the right
thing.
Signed-off-by: Alexander Larsson <alexl@redhat.com>
---
bubblewrap.c | 50 +++++++++++++++++++++++++++++++++++++++++++++++
tests/test-run.sh | 6 ++++++
2 files changed, 56 insertions(+)
diff --git a/bubblewrap.c b/bubblewrap.c
index c414bb06..bc75da47 100644
--- a/bubblewrap.c
+++ b/bubblewrap.c
@@ -341,6 +341,8 @@ usage (int ecode, FILE *out)
" --dev-bind-try SRC DEST Equal to --dev-bind but ignores non-existent SRC\n"
" --ro-bind SRC DEST Bind mount the host path SRC readonly on DEST\n"
" --ro-bind-try SRC DEST Equal to --ro-bind but ignores non-existent SRC\n"
+ " --bind-fd FD DEST Bind open directory or path fd on DEST\n"
+ " --ro-bind-fd FD DEST Bind open directory or path fd read-only on DEST\n"
" --remount-ro DEST Remount DEST as readonly; does not recursively remount\n"
" --exec-label LABEL Exec label for the sandbox\n"
" --file-label LABEL File label for temporary sandbox content\n"
@@ -1231,6 +1233,30 @@ setup_newroot (bool unshare_pid,
(op->type == SETUP_RO_BIND_MOUNT ? BIND_READONLY : 0) |
(op->type == SETUP_DEV_BIND_MOUNT ? BIND_DEVICES : 0),
0, 0, source, dest);
+
+ if (op->fd >= 0)
+ {
+ struct stat fd_st, mount_st;
+
+ /* When using bind-fd, there is a race condition between resolving the fd as a magic symlink
+ * and mounting it, where someone could replace what is at the symlink target. Ideally
+ * we would not even resolve the symlink and directly bind-mount from the fd, but unfortunately
+ * we can't do that, because its not permitted to bind mount a fd from another user namespace.
+ * So, we resolve, mount and then compare fstat+stat to detect the race. */
+
+ if (fstat(op->fd, &fd_st) != 0)
+ die_with_error("Can't stat fd %d", op->fd);
+ if (lstat(dest, &mount_st) != 0)
+ die_with_error("Can't stat mount at %s", dest);
+
+ if (fd_st.st_ino != mount_st.st_ino ||
+ fd_st.st_dev != mount_st.st_dev)
+ die_with_error("Race condition binding dirfd");
+
+ close(op->fd);
+ op->fd = -1;
+ }
+
break;
case SETUP_REMOUNT_RO_NO_RECURSIVE:
@@ -1874,6 +1900,30 @@ parse_args_recurse (int *argcp,
if (strcmp(arg, "--dev-bind-try") == 0)
op->flags = ALLOW_NOTEXIST;
+ argv += 2;
+ argc -= 2;
+ }
+ else if (strcmp (arg, "--bind-fd") == 0 ||
+ strcmp (arg, "--ro-bind-fd") == 0)
+ {
+ int src_fd;
+ char *endptr;
+
+ if (argc < 3)
+ die ("--bind-fd takes two arguments");
+
+ src_fd = strtol (argv[1], &endptr, 10);
+ if (argv[1][0] == 0 || endptr[0] != 0 || src_fd < 0)
+ die ("Invalid fd: %s", argv[1]);
+
+ if (strcmp(arg, "--ro-bind-fd") == 0)
+ op = setup_op_new (SETUP_RO_BIND_MOUNT);
+ else
+ op = setup_op_new (SETUP_BIND_MOUNT);
+ op->source = xasprintf ("/proc/self/fd/%d", src_fd);
+ op->fd = src_fd;
+ op->dest = argv[2];
+
argv += 2;
argc -= 2;
}
diff --git a/tests/test-run.sh b/tests/test-run.sh
index 6151f1a8..8d063b57 100755
--- a/tests/test-run.sh
+++ b/tests/test-run.sh
@@ -565,4 +565,10 @@ $RUN --argv0 right sh -c 'echo $0' > stdout
assert_files_equal stdout reference
echo "ok - environment manipulation"
+echo "foobar" > file-data
+$RUN --proc /proc --dev /dev --bind / / --bind-fd 100 /tmp cat /tmp/file-data 100< . > stdout
+assert_file_has_content stdout foobar
+
+echo "ok - bind-fd"
+
echo "ok - End of test"

6
bubblewrap.spec
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@ -1,10 +1,11 @@
Name: bubblewrap
Version: 0.8.0
Release: 1
Release: 2
Summary: Core execution tool for unprivileged containers
License: LGPLv2+
URL: https://github.com/projectatomic/bubblewrap
Source0: https://github.com/containers/bubblewrap/releases/download/v%{version}/bubblewrap-%{version}.tar.xz
Patch0: backport-Add--bind-fd-and--ro-bind-fd-to-let-you-bind-a-O_PATH-fd.patch
BuildRequires: autoconf automake libtool gcc libcap-devel
BuildRequires: pkgconfig(libselinux) libxslt docbook-style-xsl
@ -40,6 +41,9 @@ if ! test -x configure; then NOCONFIGURE=1 ./autogen.sh; fi
%{_mandir}/man1/*
%changelog
* Fri Aug 16 2024 wangkai <13474090681@163.com> - 0.8.0-2
- Add --bind-fd and --ro-bind-fd to let you bind a O_PATH fd for flatpak fix CVE-2024-42472
* Wed Nov 22 2023 konglidong <konglidong@uniontech.com> - 0.8.0-1
- Update version to 0.8.0