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

On Tue, May 15, 2018 at 05:50 PM +0200, Stefan Berger <stefanb(a)linux.vnet.ibm.com&gt; 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(a)linux.vnet.ibm.com&gt; 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@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@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@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@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(a)linux.vnet.ibm.com&gt; >>>> --- >>>>   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.