[libvirt] [PATCH v4 09/11] security: Label the external swtpm with SELinux labels

[Stefan Berger]

On 05/15/2018 12:13 PM, Marc Hartmayer wrote:
> On Tue, May 15, 2018 at 05:50 PM +0200, Stefan Berger <stefanb at linux.vnet.ibm.com> wrote:
>> On 05/15/2018 11:45 AM, Stefan Berger wrote:
>>> On 05/15/2018 11:38 AM, Marc Hartmayer wrote:
>>>> On Thu, May 10, 2018 at 11:57 PM +0200, Stefan Berger
>>>> <stefanb at linux.vnet.ibm.com> wrote:
>>>>> In this patch we label the swtpm process with SELinux labels. We
>>>>> give it the
>>>>> same label as the QEMU process has. We label its state directory and
>>>>> files
>>>>> as well. We restore the old security labels once the swtpm has
>>>>> terminated.
>>>>>
>>>>> The file and process labels now look as follows:
>>>>>
>>>>> Directory: /var/lib/libvirt/swtpm
>>>>>
>>>>> [root at localhost swtpm]# ls -lZ
>>>>> total 4
>>>>> rwx------. 2 tss  tss system_u:object_r:svirt_image_t:s0:c254,c932
>>>>> 4096 Apr  5 16:46 testvm
>>>>>
>>>>> [root at localhost testvm]# ls -lZ
>>>>> total 8
>>>>> -rw-r--r--. 1 tss tss system_u:object_r:svirt_image_t:s0:c254,c932
>>>>> 3648 Apr  5 16:46 tpm-00.permall
>>>>>
>>>>> The log in /var/log/swtpm/libvirt/qemu is labeled as follows:
>>>>>
>>>>> -rw-r--r--. 1 tss tss system_u:object_r:svirt_image_t:s0:c254,c932
>>>>> 2237 Apr  5 16:46 vtpm.log
>>>>>
>>>>> [root at localhost 485d0004-a48f-436a-8457-8a3b73e28567]# ps auxZ |
>>>>> grep swtpm | grep ctrl | grep -v grep
>>>>> system_u:system_r:svirt_t:s0:c254,c932 tss 25664 0.0  0.0 28172
>>>>> 3892 ?        Ss   16:57   0:00 /usr/bin/swtpm socket --daemon
>>>>> --ctrl
>>>>> type=unixio,path=/var/run/libvirt/qemu/swtpm/testvm-swtpm.sock,mode=0660
>>>>> --tpmstate dir=/var/lib/libvirt/swtpm/testvm/tpm1.2 --log
>>>>> file=/var/log/swtpm/libvirt/qemu/testvm-swtpm.log
>>>>>
>>>>> [root at localhost 485d0004-a48f-436a-8457-8a3b73e28567]# ps auxZ |
>>>>> grep qemu | grep tpm | grep -v grep
>>>>> system_u:system_r:svirt_t:s0:c254,c932 qemu 25669 99.0  0.0 3096704
>>>>> 48500 ?    Sl   16:57   3:28 /bin/qemu-system-x86_64 [..]
>>>>>
>>>>> Signed-off-by: Stefan Berger <stefanb at linux.vnet.ibm.com>
>>>>> ---
>>>>>    src/libvirt_private.syms        |   2 +
>>>>>    src/qemu/qemu_tpm.c             |  24 +++++-
>>>>>    src/security/security_driver.h  |   7 ++
>>>>>    src/security/security_manager.c |  36 +++++++++
>>>>>    src/security/security_manager.h |   6 ++
>>>>>    src/security/security_selinux.c | 164
>>>>> ++++++++++++++++++++++++++++++++++++++++
>>>>>    src/security/security_stack.c   |  40 ++++++++++
>>>>>    7 files changed, 278 insertions(+), 1 deletion(-)
>>>>>
>>>>> diff --git a/src/libvirt_private.syms b/src/libvirt_private.syms
>>>>> index 75b8932..2ce67e7 100644
>>>>> --- a/src/libvirt_private.syms
>>>>> +++ b/src/libvirt_private.syms
>>>>> @@ -1319,6 +1319,7 @@ virSecurityManagerRestoreImageLabel;
>>>>>    virSecurityManagerRestoreInputLabel;
>>>>>    virSecurityManagerRestoreMemoryLabel;
>>>>>    virSecurityManagerRestoreSavedStateLabel;
>>>>> +virSecurityManagerRestoreTPMLabels;
>>>>>    virSecurityManagerSetAllLabel;
>>>>>    virSecurityManagerSetChardevLabel;
>>>>>    virSecurityManagerSetChildProcessLabel;
>>>>> @@ -1333,6 +1334,7 @@ virSecurityManagerSetProcessLabel;
>>>>>    virSecurityManagerSetSavedStateLabel;
>>>>>    virSecurityManagerSetSocketLabel;
>>>>>    virSecurityManagerSetTapFDLabel;
>>>>> +virSecurityManagerSetTPMLabels;
>>>>>    virSecurityManagerStackAddNested;
>>>>>    virSecurityManagerTransactionAbort;
>>>>>    virSecurityManagerTransactionCommit;
>>>>> diff --git a/src/qemu/qemu_tpm.c b/src/qemu/qemu_tpm.c
>>>>> index 024d24d..62f0146 100644
>>>>> --- a/src/qemu/qemu_tpm.c
>>>>> +++ b/src/qemu/qemu_tpm.c
>>>>> @@ -684,7 +684,26 @@ qemuExtTPMStartEmulator(virQEMUDriverPtr driver,
>>>>>
>>>>>        virCommandSetErrorBuffer(cmd, &errbuf);
>>>>>
>>>>> -    if (virCommandRun(cmd, &exitstatus) < 0 || exitstatus != 0) {
>>>>> +    if (virSecurityManagerSetTPMLabels(driver->securityManager,
>>>>> +                                       def) < 0)
>>>>> +        goto cleanup;
>>>>> +
>>>>> +    if
>>>>> (virSecurityManagerSetChildProcessLabel(driver->securityManager,
>>>>> +                                               def, cmd) < 0)
>>>>> +        goto cleanup;
>>>>> +
>>>>> +    if (virSecurityManagerPreFork(driver->securityManager) < 0)
>>>>> +        goto cleanup;
>>>>> +
>>>>> +    /* make sure we run this with the appropriate user */
>>>>> +    virCommandSetUID(cmd, cfg->swtpm_user);
>>>>> +    virCommandSetGID(cmd, cfg->swtpm_group);
>>>>> +
>>>>> +    ret = virCommandRun(cmd, &exitstatus);
>>>>> +
>>>>> +    virSecurityManagerPostFork(driver->securityManager);
>>>>> +
>>>>> +    if (ret < 0 || exitstatus != 0) {
>>>>>            VIR_ERROR(_("Could not start 'swtpm'. exitstatus: %d "
>>>>>                        "stderr: %s"), exitstatus, errbuf);
>>>>>            virReportError(VIR_ERR_INTERNAL_ERROR,
>>>> Don't we have to set ret to -1 here (for the case where ret == 0 &&
>>>> exitstatus != 0)?
>>> Very true.
>> ret is initialized with '-1'. So we are good.
> No we are not good since @ret is overwritten with:
>
> ret = virCommandRun(cmd, &exitstatus);
>
> So it’s possible that virCommandRun returns 0 but exitstatus != 0
> => ret == 0; exitstatus != 0
> => virReportError(…) reports an error but the return value @ret remains 0.

After the modifications the patch looks like this and doesn't touch 
'ret' anymore:

@@ -684,7 +686,12 @@ qemuExtTPMStartEmulator(virQEMUDriverPtr driver,

      virCommandSetErrorBuffer(cmd, &errbuf);

-    if (virCommandRun(cmd, &exitstatus) < 0 || exitstatus != 0) {
+    if (qemuSecurityStartTPMEmulator(driver, def, cmd,
+                                     cfg->swtpm_user, cfg->swtpm_group,
+                                     &exitstatus, &cmdret) < 0)
+        goto cleanup;
+
+    if (cmdret < 0 || exitstatus != 0) {
          virReportError(VIR_ERR_INTERNAL_ERROR,
                         _("Could not start 'swtpm'. exitstatus: %d, "
                         "error: %s"), exitstatus, errbuf);


     Stefan