[libvirt] [PATCHv3 2/2] security: Add a new func use stat to get process DAC label

[Luyao Huang]

When use qemuProcessAttach to attach a qemu process, cannot
get a right DAC label. Add a new func to get process label
via stat func. Do not remove virDomainDefGetSecurityLabelDef
before try to use stat to get process DAC label, because
There are some other func call virSecurityDACGetProcessLabel.

v2 add support freeBSD.
v3 use snprintf instead of VirAsprintf and move the error
settings in virSecurityDACGetProcessLabelInternal.

Signed-off-by: Luyao Huang <lhuang at redhat.com>
---
 src/security/security_dac.c | 85 +++++++++++++++++++++++++++++++++++++++++++--
 1 file changed, 82 insertions(+), 3 deletions(-)

diff --git a/src/security/security_dac.c b/src/security/security_dac.c
index 85253af..8fd1e6e 100644
--- a/src/security/security_dac.c
+++ b/src/security/security_dac.c
@@ -22,6 +22,12 @@
 #include <sys/types.h>
 #include <sys/stat.h>
 #include <fcntl.h>
+#include <errno.h>
+
+#ifdef  __FreeBSD__
+# include <sys/sysctl.h>
+# include <sys/user.h>
+#endif
 
 #include "security_dac.h"
 #include "virerror.h"
@@ -1236,17 +1242,90 @@ virSecurityDACReserveLabel(virSecurityManagerPtr mgr ATTRIBUTE_UNUSED,
     return 0;
 }
 
+#ifdef __linux__
+static int
+virSecurityDACGetProcessLabelInternal(pid_t pid,
+                                      virSecurityLabelPtr seclabel)
+{
+    struct stat sb;
+    char *path = NULL;
+    int ret = -1;
+
+    VIR_INFO("Getting DAC user and group on process '%d'", pid);
+
+    if (virAsprintf(&path, "/proc/%d", (int) pid) < 0)
+        goto cleanup;
+
+    if (lstat(path, &sb) < 0) {
+        virReportSystemError(errno,
+                             _("unable to get PID %d uid and gid via stat"),
+                             pid);
+        goto cleanup;
+    }
+
+    snprintf(seclabel->label, VIR_SECURITY_LABEL_BUFLEN,
+             "+%u:+%u", (unsigned int) sb.st_uid, (unsigned int) sb.st_gid);
+    ret = 0;
+
+cleanup:
+    VIR_FREE(path);
+    return ret;
+}
+#elif defined(__FreeBSD__)
+static int
+virSecurityDACGetProcessLabelInternal(pid_t pid,
+                                      virSecurityLabelPtr seclabel)
+{
+    struct kinfo_proc p;
+    int mib[4];
+    size_t len = 4;
+
+    sysctlnametomib("kern.proc.pid", mib, &len);
+
+    len = sizeof(struct kinfo_proc);
+    mib[3] = pid;
+
+    if (sysctl(mib, 4, &p, &len, NULL, 0) < 0) {
+        virReportSystemError(errno,
+                             _("unable to get PID %d uid and gid via sysctl"),
+                             pid);
+        return -1;
+    }
+
+    snprintf(seclabel->label, VIR_SECURITY_LABEL_BUFLEN,
+             "+%u:+%u", (unsigned int) p.ki_ruid, (unsigned int) p.ki_rgid);
+
+    return 0;
+}
+#else
+static int
+virSecurityDACGetProcessLabelInternal(pid_t pid,
+                                      virSecurityLabelPtr seclabel)
+{
+    virReportError(VIR_ERR_OPERATION_UNSUPPORTED,
+                   "Cannot get proccess DAC label for pid %d on this platform",
+                   (int) pid);
+    return -1;
+}
+#endif
+
 static int
 virSecurityDACGetProcessLabel(virSecurityManagerPtr mgr ATTRIBUTE_UNUSED,
                               virDomainDefPtr def,
-                              pid_t pid ATTRIBUTE_UNUSED,
+                              pid_t pid,
                               virSecurityLabelPtr seclabel)
 {
     virSecurityLabelDefPtr secdef =
         virDomainDefGetSecurityLabelDef(def, SECURITY_DAC_NAME);
 
-    if (!secdef || !seclabel)
-        return -1;
+    if (secdef == NULL) {
+        VIR_DEBUG("missing label for DAC security "
+                  "driver in domain %s", def->name);
+
+        if (virSecurityDACGetProcessLabelInternal(pid, seclabel) < 0)
+            return -1;
+        return 0;
+    }
 
     if (secdef->label)
         ignore_value(virStrcpy(seclabel->label, secdef->label,
-- 
1.8.3.1