rolling back r14887, #2884 as it caused regressions in debbuilder

tools/rospack/main.cpp

@@ -31,6 +31,9 @@
 #include "rospack/rospack.h"
 
 #include <stdexcept>
+#if !defined(WIN32)
+  #include <unistd.h>
+#endif
 #include <stdlib.h>
 
 int main(int argc, char **argv)
@@ -41,6 +44,27 @@ int main(int argc, char **argv)
     return 0;
   }
 
+#if !defined(WIN32)
+  // If it looks we're running under sudo, try to drop back to the normal
+  // user, to avoid writing the cache with inappropriate permissions,
+  // #2884.
+  // Do the group first, because we can't do it after changing the user.
+  char* sudo_gid_string = getenv("SUDO_GID");
+  if(sudo_gid_string)
+  {
+    gid_t sudo_gid = (int)strtol(sudo_gid_string, (char **)NULL, 10);
+    if(setgid(sudo_gid))
+      perror("[rospack] Failed to change GID; cache permissions may need to be adjusted manually. setgid()");
+  }
+  char* sudo_uid_string = getenv("SUDO_UID");
+  if(sudo_uid_string)
+  {
+    uid_t sudo_uid = (int)strtol(sudo_uid_string, (char **)NULL, 10);
+    if(setuid(sudo_uid))
+      perror("[rospack] Failed to change UID; cache permissions may need to be adjusted manually. setuid()");
+  }
+#endif
+
   int ret;
   bool quiet;
   try

tools/rospack/rospack.cpp

@@ -42,8 +42,6 @@
   #include <dirent.h>
   #include <sys/time.h>
   #include <sys/file.h>
-  #include <sys/types.h>
-  #include <pwd.h>
 #endif
 #include <stdexcept>
 #include <time.h>
@@ -1580,15 +1578,7 @@ string ROSPack::getCachePath()
       cache_file_name = dotros + "\\rospack_cache";
     }
 #else // UNIX
-    // Get the user's home directory by looking up the password entry based
-    // on UID.  If that doesn't work, we fall back on examining $HOME,
-    // knowing that that can cause trouble when mixed with sudo (#2884).  
-    struct passwd* passwd_ent;
-    // Look up based on effective UID, just in case we got here by set-uid
-    if((passwd_ent = getpwuid(geteuid())))
-      ros_home = passwd_ent->pw_dir;
-    else
-      ros_home = getenv("HOME");
+    ros_home = getenv("HOME");
     if (ros_home)
     {
       // By providing the trailing slash, stat() will only succeed if the