Bug fixes and new features.

- Made the CHECK_GID feature optional (by compile-time configuration).
- The supplementary group access list is now set, if the target user has a pwent.
- Target users can be required to have a pwent (by compile-time configuration).
- Child exit statuses are now correctly propagated to the parent.
- Updated the README.
- Bumped version number to 0.5.

README

@@ -70,6 +70,11 @@ DEFAULT_UID           The default (numeric) UID to become, if no UID is given vi
 DEFAULT_GID           The same as DEFAULT_UID, but for the GID. The same reasons and
                       restrictions apply.
 
+REQUIRE_PWENT	      If set, target users are reuired to have passwd-entries. These are
+		      used to set the supplementary group access list. Defaults to 0.
+
+ALLOW_CHECKGID	      If set, enabled the CHECK_GID feature, q.v. Defaults to 1.
+
 
 The following configuration parameters shouldn't normally be changed. In case you have a
 clash with some other ENV arguments to the target program, they can be changed, however.

execwrap.c

@@ -2,7 +2,7 @@
 
 Superuser-exec wrapper for HTTP serves and other needs (made especially for lighttpd).
 Allows programs to be run with configurable uid/gid.
-Version 0.4 (2006-06-09)
+Version 0.5 (2008-07-07)
 
 For documentation on how to configure the wrapper, see the README.
 Command line option -v displays version, while -V displays compile-time configuration.
@@ -12,6 +12,11 @@ Brief version history:
 
 Vers  Date        Changes
 -----------------------------------------------------------------------------------------
+0.5   2008-07-07  Added proper handling of the supplementary group access list. Fixed a
+                  bug with passing on return values from the child process. Added
+                  compile-time configuration options to disable the CHECK_GID feature and
+                  to require the target user to have a pwent (in /etc/passwd).
+                  Thanks to stbuehler, hoffie and _lotek from #lighttpd for help.
 0.4   2006-06-09  Added a BSD license.
 0.3   2005-09-27  Changed the wrapper to stay resident and propagate SIGTERM to the
                   target. Not doing so will prevent the server from managing the target.
@@ -26,7 +31,7 @@ Vers  Date        Changes
 
 License:
 
-Copyright (c) 2006, Sune Foldager
+Copyright (c) 2008, Sune Foldager
 All rights reserved.
 
 Redistribution and use in source and binary forms, with or without modification, are
@@ -76,6 +81,9 @@ SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 #define RC_WRONG_GROUP          22
 #define RC_EXEC                 23
 #define RC_BAD_OPTION           24
+#define RC_CHILD_ABNORMAL_EXIT  25
+#define RC_MISSING_PWENT        26
+
 
 /* User configuration. */
 #include "execwrap_config.h"
@@ -95,7 +103,7 @@ SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 #endif
 
 /* Useful macro and other stuff. */
-#define VERSION_STRING "ExecWrap v0.3 by Sune Foldager."
+#define VERSION_STRING "ExecWrap v0.5   Copyright (c) 2008, Sune Foldager."
 #define STRLEN(a) (sizeof(a)-1)
 
 /* Shortcuts. */
@@ -111,8 +119,10 @@ SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 #include <stdlib.h>
 #include <string.h>
 #include <sys/stat.h>
+#include <sys/wait.h>
 #include <unistd.h>
 #include <signal.h>
+#include <pwd.h>
 
 
 /* The global child PID and previous SIGTERM handler. */
@@ -155,6 +165,9 @@ int main(int argc, char* argv[], char* envp[])
                 printf("TARGET_PATH_PREFIX : %s\n", TARGET_PATH_PREFIX);
                 printf("DEFAULT_UID        : %d\n", DEFAULT_UID);
                 printf("DEFAULT_GID        : %d\n", DEFAULT_GID);
+                puts("");
+                printf("REQUIRE_PWENT      : %d\n", REQUIRE_PWENT);
+                printf("ALLOW_CHECKGID     : %d\n", ALLOW_CHECKGID);
                 return 0;
     }
 
@@ -198,10 +211,12 @@ int main(int argc, char* argv[], char* envp[])
     }
 
     /* Check GID instead of UID. */
+    #if ALLOW_CHECKGID
     if(!strncmp(ENV_CHECK_GID, s, ENV_CHECK_GID_LEN))
     {
       check_gid = 1;
     }
+    #endif
 
     /* Use non-resident wrapping style. */
     if(!strncmp(ENV_NON_RESIDENT, s, ENV_NON_RESIDENT_LEN))
@@ -214,6 +229,12 @@ int main(int argc, char* argv[], char* envp[])
   /* See if we got all we need. */
   if(!target) return RC_MISSING_CONFIG;
 
+  /* Fetch user information from passwd. */
+  struct passwd *pwent = getpwuid(uid);
+  #if REQUIRE_PWENT
+  if(!pwent) return RC_MISSING_PWENT;
+  #endif
+
   /* Install the SIGTERM handler. */
   if(!non_resident)
   {
@@ -225,7 +246,8 @@ int main(int argc, char* argv[], char* envp[])
   if(non_resident || !(pid = fork()))
   {
 
-    /* We're in the child. Drop privileges. */
+    /* We're in the child. Drop privileges and set the group list. */
+    if(pwent && initgroups(pwent->pw_name, gid)) return RC_SETGID;
     if(setgid(gid)) return RC_SETGID;
     if(setuid(uid)) return RC_SETUID;
 
@@ -262,7 +284,6 @@ int main(int argc, char* argv[], char* envp[])
   /* Here we're in the parent. Wait for the child to be done, and return. */
   int status;
   wait(&status);
-  return status;
+  if(WIFEXITED(status)) return WEXITSTATUS(status);
-
+  return RC_CHILD_ABNORMAL_EXIT;
 }
-

execwrap_config.h

@@ -9,7 +9,7 @@ See the README for documentation.
 
 
 /* Our parent must have this UID, or we will abort. */
-#define PARENT_UID              104
+#define PARENT_UID              106
 
 /* Minimum UID we can switch to. */
 #define TARGET_MIN_UID          1000
@@ -26,3 +26,9 @@ See the README for documentation.
 /* Default GID to switch to, if none given. */
 #define DEFAULT_GID             65534
 
+
+/* Require users to have pwents (i.e. entries in /etc/passwd or similar)? */
+#define REQUIRE_PWENT           0
+
+/* Allow use of the CHECK_GID mode? */
+#define ALLOW_CHECKGID          1