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Re: [libvirt] [PATCH 2/2] libvirt patch to write a mcs translation file to /run/setrans directory



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On 05/17/2013 05:52 AM, Daniel P. Berrange wrote:
> On Wed, May 15, 2013 at 02:36:32PM -0400, dwalsh redhat com wrote:
>> From: Dan Walsh <dwalsh redhat com>
>> 
>> mcstransd is a translation tool that can translate MCS Labels into human 
>> understandable code.  I have patched it to watch for translation files in
>> the /run/setrans directory.  This allows us to run commands like ps -eZ
>> and see system_u:system_r:svirt_t:Fedora18 rather then
>> system_u:system_r:svirt_t:s0:c1,c2. When used with containers it would
>> make an easy way to list all processes within a container using ps -eZ |
>> grep Fedora18 --- src/security/security_selinux.c | 59
>> ++++++++++++++++++++++++++++++++++++++++- 1 file changed, 58
>> insertions(+), 1 deletion(-)
>> 
>> diff --git a/src/security/security_selinux.c
>> b/src/security/security_selinux.c index 5d108b9..cbcd013 100644 ---
>> a/src/security/security_selinux.c +++ b/src/security/security_selinux.c 
>> @@ -83,6 +83,57 @@
>> virSecuritySELinuxRestoreSecurityTPMFileLabelInt(virSecurityManagerPtr
>> mgr, virDomainTPMDefPtr tpm);
>> 
>> 
>> +static int +virSecuritySELinuxAddMCSFile(const char *name, +
>> const char *label) +{ +    int ret = -1; +    char *tmp = NULL; +
>> context_t con = NULL; + +    if (virAsprintf(&tmp, "%s/%s",
>> SELINUX_TRANS_DIR, name) < 0) { +        virReportOOMError(); +
>> return -1; +    } +    if (! (con = context_new(label))) { +
>> virReportSystemError(errno, "%s", +                             _("unable
>> to allocate security context")); +        goto cleanup; +    } +    if
>> (virFileWriteStr(tmp, context_range_get(con), 0) < 0) { +
>> virReportSystemError(errno, +                             _("unable to
>> create MCS file %s"), tmp); +        goto cleanup; +    } +    ret = 0; 
>> + +cleanup: +    VIR_FREE(tmp); +    context_free(con); +    return ret; 
>> +} + +static int +virSecuritySELinuxRemoveMCSFile(const char *name) +{ +
>> char *tmp=NULL; +    int ret = -1; +    if (virAsprintf(&tmp, "%s/%s",
>> SELINUX_TRANS_DIR, name) < 0) { +        virReportOOMError(); +
>> return -1; +    } +    if (unlink(tmp) < 0 && errno != ENOENT) { +
>> virReportSystemError(errno, +                             _("Unable to
>> remove MCS file %s"), tmp); +        goto cleanup; +    } +    ret = 0; 
>> + +cleanup: +    VIR_FREE(tmp); +    return ret; +} + /* * Returns 0 on
>> success, 1 if already reserved, or -1 on fatal error */ @@ -1953,7
>> +2004,7 @@ virSecuritySELinuxReleaseSecurityLabel(virSecurityManagerPtr
>> mgr, } VIR_FREE(secdef->imagelabel);
>> 
>> -    return 0; +    return virSecuritySELinuxRemoveMCSFile(def->name); }
>> 
>> 
>> @@ -2047,10 +2098,16 @@
>> virSecuritySELinuxSetSecurityProcessLabel(virSecurityManagerPtr mgr
>> ATTRIBUTE_UN return -1; }
>> 
>> +    if (virSecuritySELinuxAddMCSFile(def->name, secdef->label) < 0) { +
>> if (security_getenforce() == 1) +            return -1; +    } +
> 
> As you mentioned offlist, this is not going to work because the 
> SetProcessLabel function is called in a child process, where you can't
> guarantee to see the host's /run directory.
> 
> Instead it should be done in the GenSecurityLabel function which is called
> from a safe context.
> 
> 
> Daniel
> 
Fine, but what about the case where the user is running libvirt and libvirt is
not allowed to write to /run/setrans.  Should we just silently fail in this case?
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