From 8b45766aaa2c8f5682be4f630d4e73ba32a9f191 Mon Sep 17 00:00:00 2001
From: apio <blobs.trading@gmail.com>
Date: Sat, 8 Apr 2023 16:31:33 +0200
Subject: [PATCH] su: Use user names and read from the password file instead of
 using raw user IDs

---
 apps/su.cpp | 24 +++++++++++++++---------
 1 file changed, 15 insertions(+), 9 deletions(-)

diff --git a/apps/su.cpp b/apps/su.cpp
index 2141be81..bc2a84f3 100644
--- a/apps/su.cpp
+++ b/apps/su.cpp
@@ -1,11 +1,12 @@
 #include <os/ArgumentParser.h>
+#include <pwd.h>
 #include <stdio.h>
 #include <stdlib.h>
 #include <unistd.h>
 
 int main(int argc, char** argv)
 {
-    StringView id;
+    StringView name;
 
     if (geteuid() != 0)
     {
@@ -14,19 +15,24 @@ int main(int argc, char** argv)
     }
 
     os::ArgumentParser parser;
-    parser.add_positional_argument(id, "id"_sv, true);
+    parser.add_positional_argument(name, "name"_sv, true);
     parser.parse(argc, argv);
 
-    int uid = atoi(id.chars());
-
-    if (uid == 0)
+    struct passwd* entry = getpwnam(name.chars());
+    if (!entry)
     {
-        fprintf(stderr, "Already root!\n");
+        fprintf(stderr, "su: user %s not found!\n", name.chars());
         return 1;
     }
 
-    setgid(uid);
-    setuid(uid);
+    if (getuid() != geteuid())
+    {
+        fprintf(stderr, "FIXME: you have to enter %s's password first!\n", name.chars());
+        return 1;
+    }
 
-    execl("/bin/sh", "sh", NULL);
+    setgid(entry->pw_gid);
+    setuid(entry->pw_uid);
+
+    execl(entry->pw_shell, entry->pw_shell, NULL);
 }