No longer permit the exim user to be root. Fixes: #752

3 files changed, 24 insertions, 5 deletions

diff --git a/src/src/EDITME b/src/src/EDITME
index 85922f8aa..7f7f6b3a4 100644
--- a/src/src/EDITME
+++ b/src/src/EDITME
@@ -1,4 +1,4 @@
-# $Cambridge: exim/src/src/EDITME,v 1.25 2010/06/05 11:13:29 pdp Exp $
+# $Cambridge: exim/src/src/EDITME,v 1.26 2010/06/06 02:46:13 pdp Exp $
 
 ##################################################
 #          The Exim mail transport agent         #
@@ -131,8 +131,7 @@ CONFIGURE_FILE=/usr/exim/configure
 # group that is used for Exim processes when they no longer need to be root. In
 # particular, this applies when receiving messages and when doing remote
 # deliveries. (Local deliveries run as various non-root users, typically as the
-# owner of a local mailbox.) Specifying these values as root is very strongly
-# discouraged.
+# owner of a local mailbox.) Specifying these values as root is not supported.
 
 EXIM_USER=
 
diff --git a/src/src/buildconfig.c b/src/src/buildconfig.c
index 51fe02618..36561a968 100644
--- a/src/src/buildconfig.c
+++ b/src/src/buildconfig.c
@@ -1,4 +1,4 @@
-/* $Cambridge: exim/src/src/buildconfig.c,v 1.15 2009/11/16 19:50:36 nm4 Exp $ */
+/* $Cambridge: exim/src/src/buildconfig.c,v 1.16 2010/06/06 02:46:13 pdp Exp $ */
 
 /*************************************************
 *     Exim - an Internet mail transport agent    *
@@ -356,6 +356,7 @@ while (fgets(buffer, sizeof(buffer), base) != NULL)
     uid_t uid = 0;
     gid_t gid = 0;
     int gid_set = 0;
+    int uid_not_set = 0;
     char *username = NULL;
     char *groupname = NULL;
     char *s;
@@ -410,6 +411,7 @@ while (fgets(buffer, sizeof(buffer), base) != NULL)
       while (isspace(*user)) user++;
       username = user;
       gid_set = 1;
+      uid_not_set = 1;
       }
 
     else
@@ -503,6 +505,18 @@ while (fgets(buffer, sizeof(buffer), base) != NULL)
       return 1;
       }
 
+    /* security sanity checks
+    if ref: is being used, we can never be sure, but we can take reasonable
+    steps to filter out the most obvious ones.  */
+
+    if ((!uid_not_set && uid == 0) ||
+        (strcmp(username, "root") == 0) ||
+        (strcmp(username, "toor") == 0) )
+      {
+      printf("\n*** Exim's internal user must not be root.\n\n");
+      return 1;
+      }
+
     /* Output user and group names or uid/gid. When names are set, uid/gid
     are set to zero but will be replaced at runtime. */
 
diff --git a/src/src/exim.c b/src/src/exim.c
index 36f7a1b3d..a68a06227 100644
--- a/src/src/exim.c
+++ b/src/src/exim.c
@@ -1,4 +1,4 @@
-/* $Cambridge: exim/src/src/exim.c,v 1.68 2010/06/06 02:08:50 pdp Exp $ */
+/* $Cambridge: exim/src/src/exim.c,v 1.69 2010/06/06 02:46:13 pdp Exp $ */
 
 /*************************************************
 *     Exim - an Internet mail transport agent    *
@@ -1234,6 +1234,12 @@ This is a feature to make the lives of binary distributors easier. */
 #ifdef EXIM_USERNAME
 if (route_finduser(US EXIM_USERNAME, &pw, &exim_uid))
   {
+  if (exim_uid == 0)
+    {
+    fprintf(stderr, "exim: refusing to run with uid 0 for \"%s\"\n",
+      EXIM_USERNAME);
+    exit(EXIT_FAILURE);
+    }
   exim_gid = pw->pw_gid;
   }
 else