when called with the setid bit change euid to uid sooner to make sure that we can access our own files even when we dropped most capabilities. (Closes #21)

git-svn-id: file:///home/lennart/svn/public/pulseaudio/trunk@1455 fefdeb5f-60dc-0310-8127-8f9354f1896f

2 files changed, 33 insertions, 29 deletions

diff --git a/src/daemon/caps.c b/src/daemon/caps.c
index 2ea51c9f..8043230c 100644
--- a/src/daemon/caps.c
+++ b/src/daemon/caps.c
@@ -35,6 +35,9 @@
 #ifdef HAVE_SYS_CAPABILITY_H
 #include <sys/capability.h>
 #endif
+#ifdef HAVE_SYS_PRCTL_H
+#include <sys/prctl.h>
+#endif
 
 #include <pulsecore/core-error.h>
 
@@ -76,35 +79,31 @@ void pa_drop_root(void) {
 
 #endif
 
-#ifdef HAVE_SYS_CAPABILITY_H
+#if defined(HAVE_SYS_CAPABILITY_H) && defined(HAVE_SYS_PRCTL_H)
 
-/* Limit capabilities set to CAPSYS_NICE */
+/* Limit permitted capabilities set to CAPSYS_NICE */
 int pa_limit_caps(void) {
     int r = -1;
     cap_t caps;
     cap_value_t nice_cap = CAP_SYS_NICE;
 
-    /* Only drop caps when called SUID */
-    if (getuid() == 0)
-        return 0;
-
     caps = cap_init();
     assert(caps);
-
     cap_clear(caps);
-
-    cap_set_flag(caps, CAP_EFFECTIVE, 1, &nice_cap, CAP_SET);
     cap_set_flag(caps, CAP_PERMITTED, 1, &nice_cap, CAP_SET);
 
     if (cap_set_proc(caps) < 0)
         goto fail;
 
+    if (prctl(PR_SET_KEEPCAPS, 1, 0, 0, 0) < 0)
+        goto fail;
+    
     pa_log_info("dropped capabilities successfully.");
-
-    r = 0;
+    
+    r = 1;
 
 fail:
-    cap_free (caps);
+    cap_free(caps);
 
     return r;
 }
@@ -114,24 +113,22 @@ int pa_drop_caps(void) {
     cap_t caps;
     int r = -1;
 
-    /* Only drop caps when called SUID */
-    if (getuid() == 0)
-        return 0;
-
     caps = cap_init();
     assert(caps);
 
     cap_clear(caps);
 
+    prctl(PR_SET_KEEPCAPS, 0, 0, 0, 0);
+    
     if (cap_set_proc(caps) < 0) {
         pa_log("failed to drop capabilities: %s", pa_cstrerror(errno));
         goto fail;
     }
-
+    
     r = 0;
 
 fail:
-    cap_free (caps);
+    cap_free(caps);
 
     return r;
 }
diff --git a/src/daemon/main.c b/src/daemon/main.c
index 211dd30c..72e47975 100644
--- a/src/daemon/main.c
+++ b/src/daemon/main.c
@@ -329,22 +329,29 @@ int main(int argc, char *argv[]) {
     struct timeval tv;
 #endif
 
-    setlocale(LC_ALL, "");
-
-    pa_limit_caps();
-
 #ifdef HAVE_GETUID
     real_root = getuid() == 0;
     suid_root = !real_root && geteuid() == 0;
+#else
+    real_root = 0;
+    suid_root = 0;
+#endif
+
+    if (suid_root) {
+        if (pa_limit_caps() > 0)
+            /* We managed to drop capabilities except the needed
+             * ones. Hence we can drop the uid. */
+            pa_drop_root();
+    }
+
+    setlocale(LC_ALL, "");
 
     if (suid_root && (pa_own_uid_in_group(PA_REALTIME_GROUP, &gid) <= 0 || gid >= 1000)) {
         pa_log_warn("WARNING: called SUID root, but not in group '"PA_REALTIME_GROUP"'.");
+        pa_drop_caps();
         pa_drop_root();
+        suid_root = real_root = 0;
     }
-#else
-    real_root = 0;
-    suid_root = 0;
-#endif
 
     LTDL_SET_PRELOADED_SYMBOLS();
 
@@ -381,10 +388,10 @@ int main(int argc, char *argv[]) {
     if (conf->high_priority && conf->cmd == PA_CMD_DAEMON)
         pa_raise_priority();
 
-    pa_drop_caps();
-
-    if (suid_root)
+    if (suid_root) {
+        pa_drop_caps();
         pa_drop_root();
+    }
 
     if (conf->dl_search_path)
         lt_dlsetsearchpath(conf->dl_search_path);