More secure setgroups functions. (thanks muh)

3 files changed, 19 insertions, 4 deletions

diff --git a/src/include/skalibs/setgroups.h b/src/include/skalibs/setgroups.h
index fab0614..98998e0 100644
--- a/src/include/skalibs/setgroups.h
+++ b/src/include/skalibs/setgroups.h
@@ -9,6 +9,7 @@
 
 #include <unistd.h>
 
+extern int setgroups_and_gid (gid_t, size_t, gid_t const *) ;
 extern int setgroups_with_egid (size_t, gid_t const *) ;
 extern int skalibs_setgroups (size_t, gid_t const *) ;
 
diff --git a/src/libstddjb/prot_grps.c b/src/libstddjb/prot_grps.c
index cc4ba0d..c5ea35b 100644
--- a/src/libstddjb/prot_grps.c
+++ b/src/libstddjb/prot_grps.c
@@ -2,16 +2,26 @@
 
 /* MT-unsafe */
 
-#include <skalibs/nonposix.h>
 #include <unistd.h>
+#include <pwd.h>
 #include <grp.h>
 #include <limits.h>
+#include <errno.h>
 #include <skalibs/setgroups.h>
 #include <skalibs/djbunix.h>
 
 int prot_grps (char const *name)
 {
   gid_t tab[NGROUPS_MAX] ;
+  struct passwd *pw ;
   int n = prot_readgroups(name, tab, NGROUPS_MAX) ;
-  return n < 0 ? -1 : setgroups(n, tab) ;
+  if (n < 0) return n ;
+  errno = 0 ;
+  pw = getpwnam(name) ;
+  if (!pw)
+  {
+    if (!errno) errno = ENOENT ;
+    return -1 ;
+  }
+  return setgroups_and_gid(pw->pw_gid, n, tab) ;
 }
diff --git a/src/libstddjb/setgroups.c b/src/libstddjb/setgroups.c
index c7610ab..d064ed2 100644
--- a/src/libstddjb/setgroups.c
+++ b/src/libstddjb/setgroups.c
@@ -10,10 +10,9 @@
 #include <grp.h>
 #include <skalibs/setgroups.h>
 
-int setgroups_with_egid (size_t n, gid_t const *tab)
+int setgroups_and_gid (gid_t g, size_t n, gid_t const *tab)
 {
   size_t i = 1 ;
-  gid_t g = getegid() ;
   if (!n) return setgroups(1, &g) ;
   if (tab[0] == g) return setgroups(n, tab) ;
   for (; i < n ; i++) if (tab[i] == g) break ;
@@ -34,6 +33,11 @@ int setgroups_with_egid (size_t n, gid_t const *tab)
   }
 }
 
+int setgroups_with_egid (size_t n, gid_t const *tab)
+{
+  return setgroups_and_gid(getegid(), n, tab) ;
+}
+
 int skalibs_setgroups (size_t n, gid_t const *tab)
 {
 #ifdef SKALIBS_BSD_SUCKS