Fetch the supplementary groups properly. Closes #1.

src/main.zig

@@ -19,12 +19,13 @@ const c = @cImport({
     @cInclude("unistd.h");
     @cInclude("grp.h");
     @cInclude("crypt.h");
+    @cInclude("string.h");
 });
 
 fn getGroups(alloc: mem.Allocator, passwd: c.passwd) ![]c.gid_t {
     var ngr: c_int = 0;
     _ = c.getgrouplist(passwd.pw_name, passwd.pw_gid, null, &ngr);
-    const groups = try alloc.alloc(c.gid_t, @intCast(usize, ngr));
+    const groups = try alloc.alloc(c.gid_t, @intCast(ngr));
     _ = c.getgrouplist(passwd.pw_name, passwd.pw_gid, groups.ptr, &ngr);
     return groups;
 }
@@ -32,16 +33,16 @@ fn getGroups(alloc: mem.Allocator, passwd: c.passwd) ![]c.gid_t {
 pub fn main() !u8 {
     const stderr = io.getStdErr().writer();
     if (os.argv.len <= 1) {
-      try stderr.print("Not enough arguments\n", .{});
-      return 1;
+        try stderr.print("Not enough arguments\n", .{});
+        return 1;
     }
 
     const passwd = c.getpwuid(c.getuid()).*;
 
     const shadowEntry = c.getspnam(passwd.pw_name);
     if (shadowEntry == null) {
-      try stderr.print("Missing setuid on binary {s}\n", .{os.argv[0]});
-      return 1;
+        try stderr.print("Missing setuid on binary {s}\n", .{os.argv[0]});
+        return 1;
     }
     const shadow = shadowEntry.*;
 
@@ -55,18 +56,20 @@ pub fn main() !u8 {
         const gr = c.getgrgid(gr_id).*;
         if (gr.gr_gid == wheel.gr_gid) {
             const pass = mem.span(c.getpass("#: "));
-            if (cstr.cmp(shadow.sp_pwdp, c.crypt(pass, shadow.sp_pwdp)) == 0) {
+            if (c.strcmp(shadow.sp_pwdp, c.crypt(pass, shadow.sp_pwdp)) == 0) {
                 crypto.utils.secureZero(u8, pass);
                 _ = c.setuid(0);
                 _ = c.setgid(0);
+                const rootGroups = try getGroups(gpa, c.getpwuid(0).*);
+                _ = c.setgroups(rootGroups.len, rootGroups.ptr);
                 var argl = ArrayList([]const u8).init(gpa);
                 for (os.argv[1..]) |arg| {
                     try argl.append(mem.span(arg));
                 }
                 return process.execv(gpa, try argl.toOwnedSlice());
             } else {
-              try stderr.print("Wrong Password\n", .{});
-              return 1;
+                try stderr.print("Wrong Password\n", .{});
+                return 1;
             }
             break;
         }