[PATCH xserver v2 1/4] os: move xf86PrivsElevated here

[Ben Crocker]

From: Nicolai Hähnle <nicolai.haehnle at amd.com>

Having different types of code all trying to check for elevated privileges
is a bad idea. This implementation is the most thorough one.

Signed-off-by: Nicolai Hähnle <nicolai.haehnle at amd.com>
Reviewed-by: Ben Crocker <bcrocker at redhat.com>
Reviewed-by: Antoine Martin <antoine at nagafix.co.uk>
Tested-by: Ben Crocker <bcrocker at redhat.com>
---
 hw/xfree86/common/xf86Init.c | 59 +----------------------------------------
 include/os.h                 |  3 +++
 os/utils.c                   | 63 ++++++++++++++++++++++++++++++++++++++++++++
 3 files changed, 67 insertions(+), 58 deletions(-)

diff --git a/hw/xfree86/common/xf86Init.c b/hw/xfree86/common/xf86Init.c
index cdbf80c61..88d202463 100644
--- a/hw/xfree86/common/xf86Init.c
+++ b/hw/xfree86/common/xf86Init.c
@@ -238,64 +238,7 @@ xf86PrintBanner(void)
 Bool
 xf86PrivsElevated(void)
 {
-    static Bool privsTested = FALSE;
-    static Bool privsElevated = TRUE;
-
-    if (!privsTested) {
-#if defined(WIN32)
-        privsElevated = FALSE;
-#else
-        if ((getuid() != geteuid()) || (getgid() != getegid())) {
-            privsElevated = TRUE;
-        }
-        else {
-#if defined(HAVE_ISSETUGID)
-            privsElevated = issetugid();
-#elif defined(HAVE_GETRESUID)
-            uid_t ruid, euid, suid;
-            gid_t rgid, egid, sgid;
-
-            if ((getresuid(&ruid, &euid, &suid) == 0) &&
-                (getresgid(&rgid, &egid, &sgid) == 0)) {
-                privsElevated = (euid != suid) || (egid != sgid);
-            }
-            else {
-                printf("Failed getresuid or getresgid");
-                /* Something went wrong, make defensive assumption */
-                privsElevated = TRUE;
-            }
-#else
-            if (getuid() == 0) {
-                /* running as root: uid==euid==0 */
-                privsElevated = FALSE;
-            }
-            else {
-                /*
-                 * If there are saved ID's the process might still be privileged
-                 * even though the above test succeeded. If issetugid() and
-                 * getresgid() aren't available, test this by trying to set
-                 * euid to 0.
-                 */
-                unsigned int oldeuid;
-
-                oldeuid = geteuid();
-
-                if (seteuid(0) != 0) {
-                    privsElevated = FALSE;
-                }
-                else {
-                    if (seteuid(oldeuid) != 0) {
-                        FatalError("Failed to drop privileges.  Exiting\n");
-                    }
-                    privsElevated = TRUE;
-                }
-            }
-#endif
-        }
-#endif
-        privsTested = TRUE;
-    }
-    return privsElevated;
+    return PrivsElevated();
 }
 
 static void
diff --git a/include/os.h b/include/os.h
index e141a6b02..7b4cb9481 100644
--- a/include/os.h
+++ b/include/os.h
@@ -368,6 +368,9 @@ System(const char *cmdline);
 #define Fclose(a) fclose(a)
 #endif
 
+extern _X_EXPORT Bool
+PrivsElevated(void);
+
 extern _X_EXPORT void
 CheckUserParameters(int argc, char **argv, char **envp);
 extern _X_EXPORT void
diff --git a/os/utils.c b/os/utils.c
index 4a8d1249f..4305dab26 100644
--- a/os/utils.c
+++ b/os/utils.c
@@ -1719,6 +1719,69 @@ System(const char *cmdline)
 }
 #endif
 
+Bool
+PrivsElevated(void)
+{
+    static Bool privsTested = FALSE;
+    static Bool privsElevated = TRUE;
+
+    if (!privsTested) {
+#if defined(WIN32)
+        privsElevated = FALSE;
+#else
+        if ((getuid() != geteuid()) || (getgid() != getegid())) {
+            privsElevated = TRUE;
+        }
+        else {
+#if defined(HAVE_ISSETUGID)
+            privsElevated = issetugid();
+#elif defined(HAVE_GETRESUID)
+            uid_t ruid, euid, suid;
+            gid_t rgid, egid, sgid;
+
+            if ((getresuid(&ruid, &euid, &suid) == 0) &&
+                (getresgid(&rgid, &egid, &sgid) == 0)) {
+                privsElevated = (euid != suid) || (egid != sgid);
+            }
+            else {
+                printf("Failed getresuid or getresgid");
+                /* Something went wrong, make defensive assumption */
+                privsElevated = TRUE;
+            }
+#else
+            if (getuid() == 0) {
+                /* running as root: uid==euid==0 */
+                privsElevated = FALSE;
+            }
+            else {
+                /*
+                 * If there are saved ID's the process might still be privileged
+                 * even though the above test succeeded. If issetugid() and
+                 * getresgid() aren't available, test this by trying to set
+                 * euid to 0.
+                 */
+                unsigned int oldeuid;
+
+                oldeuid = geteuid();
+
+                if (seteuid(0) != 0) {
+                    privsElevated = FALSE;
+                }
+                else {
+                    if (seteuid(oldeuid) != 0) {
+                        FatalError("Failed to drop privileges.  Exiting\n");
+                    }
+                    privsElevated = TRUE;
+                }
+            }
+#endif
+        }
+#endif
+        privsTested = TRUE;
+    }
+    return privsElevated;
+}
+
 /*
  * CheckUserParameters: check for long command line arguments and long
  * environment variables.  By default, these checks are only done when
-- 
2.13.6