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CVE-2015-5313: storage: don't allow '/' in filesystem volume names

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The libvirt file system storage driver determines what file to
act on by concatenating the pool location with the volume name.
If a user is able to pick names like "../../../etc/passwd", then
they can escape the bounds of the pool.  For that matter,
virStoragePoolListVolumes() doesn't descend into subdirectories,
so a user really shouldn't use a name with a slash.

Normally, only privileged users can coerce libvirt into creating
or opening existing files using the virStorageVol APIs; and such
users already have full privilege to create any domain XML (so it
is not an escalation of privilege).  But in the case of
fine-grained ACLs, it is feasible that a user can be granted
storage_vol:create but not domain:write, and it violates
assumptions if such a user can abuse libvirt to access files
outside of the storage pool.

Therefore, prevent all use of volume names that contain "/",
whether or not such a name is actually attempting to escape the
pool.

This changes things from:

$ virsh vol-create-as default ../../../../../../etc/haha --capacity 128
Vol ../../../../../../etc/haha created
$ rm /etc/haha

to:

$ virsh vol-create-as default ../../../../../../etc/haha --capacity 128
error: Failed to create vol ../../../../../../etc/haha
error: Requested operation is not valid: volume name '../../../../../../etc/haha' cannot contain '/'

Signed-off-by: Eric Blake <eblake@redhat.com>
(cherry picked from commit 034e47c338)
This commit is contained in:
Eric Blake 2015-12-08 17:46:31 -07:00
parent 614c8d4c6b
commit 02d365dae5
1 changed files with 9 additions and 1 deletions
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10
src/storage/storage_backend_fs.c
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@ -1,7 +1,7 @@
/*
* storage_backend_fs.c: storage backend for FS and directory handling
*
* Copyright (C) 2007-2014 Red Hat, Inc.
* Copyright (C) 2007-2015 Red Hat, Inc.
* Copyright (C) 2007-2008 Daniel P. Berrange
*
* This library is free software; you can redistribute it and/or
@ -1001,6 +1001,14 @@ virStorageBackendFileSystemVolCreate(virConnectPtr conn ATTRIBUTE_UNUSED,
vol->type = VIR_STORAGE_VOL_FILE;
/* Volumes within a directory pools are not recursive; do not
* allow escape to ../ or a subdir */
if (strchr(vol->name, '/')) {
virReportError(VIR_ERR_OPERATION_INVALID,
_("volume name '%s' cannot contain '/'"), vol->name);
return -1;
}
VIR_FREE(vol->target.path);
if (virAsprintf(&vol->target.path, "%s/%s",
pool->def->target.path,