[libvirt] [PATCHv3] security: Don't ignore errors when parsing DAC security labels

[Peter Krempa]

The DAC security driver silently ignored errors when parsing the DAC
label and used default values instead.

With a domain containing the following label definition:

<seclabel type='static' model='dac' relabel='yes'>
  <label>sdfklsdjlfjklsdjkl</label>
</seclabel>

the domain would start normaly but the disk images would be still owned
by root and no error was displayed.

This patch changes the behavior if the parsing of the label fails (note
that a not present label is not a failure and in this case the default
label should be used) the error isn't masked but is raised that causes
the domain start to fail with a descriptive error message:

virsh #  start tr
error: Failed to start domain tr
error: internal error invalid argument: failed to parse DAC label
'sdfklsdjlfjklsdjkl' for domain 'tr'

I also changed the error code to "invalid argument" from "internal
error" and tweaked the various error messages to contain correct and
useful information.
---
Diff to v2:
- Fixed all error reporting paths to contain useful messages
- Tweaked error messages to contain more information
- Fixed printing of seclabel->label instead of seclabel->imagelabel in the imagelabel parsing func.

 src/security/security_dac.c | 95 +++++++++++++++++++++++++++++----------------
 1 file changed, 61 insertions(+), 34 deletions(-)

diff --git a/src/security/security_dac.c b/src/security/security_dac.c
index 211fb37..be65d6e 100644
--- a/src/security/security_dac.c
+++ b/src/security/security_dac.c
@@ -90,6 +90,7 @@ int parseIds(const char *label, uid_t *uidPtr, gid_t *gidPtr)
     return 0;
 }

+/* returns 1 if label isn't found, 0 on success, -1 on error */
 static
 int virSecurityDACParseIds(virDomainDefPtr def, uid_t *uidPtr, gid_t *gidPtr)
 {
@@ -98,20 +99,18 @@ int virSecurityDACParseIds(virDomainDefPtr def, uid_t *uidPtr, gid_t *gidPtr)
     virSecurityLabelDefPtr seclabel;

     if (def == NULL)
-        return -1;
+        return 1;

     seclabel = virDomainDefGetSecurityLabelDef(def, SECURITY_DAC_NAME);
     if (seclabel == NULL || seclabel->label == NULL) {
-        virReportError(VIR_ERR_INTERNAL_ERROR,
-                       _("security label for DAC not found in domain %s"),
-                       def->name);
-        return -1;
+        VIR_DEBUG("DAC seclabel for domain '%s' wasn't found", def->name);
+        return 1;
     }

     if (seclabel->label && parseIds(seclabel->label, &uid, &gid)) {
-        virReportError(VIR_ERR_INTERNAL_ERROR,
-                       _("failed to parse uid and gid for DAC "
-                         "security driver: %s"), seclabel->label);
+       virReportError(VIR_ERR_INVALID_ARG,
+                       _("failed to parse DAC label '%s' for domain '%s'"),
+                       seclabel->label, def->name);
         return -1;
     }

@@ -127,19 +126,35 @@ static
 int virSecurityDACGetIds(virDomainDefPtr def, virSecurityDACDataPtr priv,
                          uid_t *uidPtr, gid_t *gidPtr)
 {
-    if (virSecurityDACParseIds(def, uidPtr, gidPtr) == 0)
-        return 0;
+    int ret;

-    if (priv) {
-        if (uidPtr)
-            *uidPtr = priv->user;
-        if (gidPtr)
-            *gidPtr = priv->group;
-        return 0;
+    if (!def && !priv) {
+        virReportError(VIR_ERR_INTERNAL_ERROR, "%s",
+                       _("Failed to determine default DAC label "
+                         "for an unknown object"));
+        return -1;
     }
-    return -1;
+
+    if ((ret = virSecurityDACParseIds(def, uidPtr, gidPtr)) <= 0)
+        return ret;
+
+    if (!priv) {
+        virReportError(VIR_ERR_INTERNAL_ERROR,
+                       _("DAC security label couldn't be determined "
+                         "for domain '%s'"), def->name);
+        return -1;
+    }
+
+    if (uidPtr)
+        *uidPtr = priv->user;
+    if (gidPtr)
+        *gidPtr = priv->group;
+
+    return 0;
 }

+
+/* returns 1 if label isn't found, 0 on success, -1 on error */
 static
 int virSecurityDACParseImageIds(virDomainDefPtr def,
                                 uid_t *uidPtr, gid_t *gidPtr)
@@ -149,21 +164,19 @@ int virSecurityDACParseImageIds(virDomainDefPtr def,
     virSecurityLabelDefPtr seclabel;

     if (def == NULL)
-        return -1;
+        return 1;

     seclabel = virDomainDefGetSecurityLabelDef(def, SECURITY_DAC_NAME);
     if (seclabel == NULL || seclabel->imagelabel == NULL) {
-        virReportError(VIR_ERR_INTERNAL_ERROR,
-                       _("security label for DAC not found in domain %s"),
-                       def->name);
-        return -1;
+        VIR_DEBUG("DAC imagelabel for domain '%s' wasn't found", def->name);
+        return 1;
     }

     if (seclabel->imagelabel
         && parseIds(seclabel->imagelabel, &uid, &gid)) {
-        virReportError(VIR_ERR_INTERNAL_ERROR,
-                       _("failed to parse uid and gid for DAC "
-                         "security driver: %s"), seclabel->label);
+       virReportError(VIR_ERR_INVALID_ARG,
+                       _("failed to parse DAC imagelabel '%s' for domain '%s'"),
+                       seclabel->imagelabel, def->name);
         return -1;
     }

@@ -179,17 +192,31 @@ static
 int virSecurityDACGetImageIds(virDomainDefPtr def, virSecurityDACDataPtr priv,
                          uid_t *uidPtr, gid_t *gidPtr)
 {
-    if (virSecurityDACParseImageIds(def, uidPtr, gidPtr) == 0)
-        return 0;
+    int ret;

-    if (priv) {
-        if (uidPtr)
-            *uidPtr = priv->user;
-        if (gidPtr)
-            *gidPtr = priv->group;
-        return 0;
+    if (!def && !priv) {
+        virReportError(VIR_ERR_INTERNAL_ERROR, "%s",
+                       _("Failed to determine default DAC imagelabel "
+                         "for an unknown object"));
+        return -1;
+    }
+
+    if ((ret = virSecurityDACParseImageIds(def, uidPtr, gidPtr)) <= 0)
+        return ret;
+
+    if (!priv) {
+        virReportError(VIR_ERR_INTERNAL_ERROR,
+                       _("DAC security imagelabel couldn't be determined "
+                         "for domain '%s'"), def->name);
+        return -1;
     }
-    return -1;
+
+    if (uidPtr)
+        *uidPtr = priv->user;
+    if (gidPtr)
+        *gidPtr = priv->group;
+
+    return 0;
 }


-- 
1.7.12