kernel: proc: Add initial setuid()

Signed-off-by: Ian Moffett <ian@osmora.org>

2 files changed, 58 insertions, 0 deletions

diff --git a/sys/include/sys/ucred.h b/sys/include/sys/ucred.h
index 32eb9b3..ef66a18 100644
--- a/sys/include/sys/ucred.h
+++ b/sys/include/sys/ucred.h
@@ -46,4 +46,5 @@ struct ucred {
 #endif  /* _KERNEL */
 };
 
+int setuid(uid_t new);
 #endif  /* !_SYS_UCRED_H_ */
diff --git a/sys/kern/kern_cred.c b/sys/kern/kern_cred.c
new file mode 100644
index 0000000..828ba3b
--- /dev/null
+++ b/sys/kern/kern_cred.c
@@ -0,0 +1,57 @@
+/*
+ * Copyright (c) 2023-2025 Ian Marco Moffett and the Osmora Team.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright notice,
+ *    this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ * 3. Neither the name of Hyra nor the names of its
+ *    contributors may be used to endorse or promote products derived from
+ *    this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+ * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
+ * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
+ * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
+ * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
+ * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
+ * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+ * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+ * POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#include <sys/types.h>
+#include <sys/errno.h>
+#include <sys/ucred.h>
+#include <sys/proc.h>
+
+int
+setuid(uid_t new)
+{
+    struct proc *td;
+    struct ucred *cur_cred;
+
+    td = this_td();
+    cur_cred = &td->cred;
+
+    /*
+     * Only root can become other users. If you are not
+     * root, fuck off.
+     */
+    if (cur_cred->ruid != 0) {
+        return -EPERM;
+    }
+
+    spinlock_acquire(&cur_cred->lock);
+    cur_cred->euid = new;
+    cur_cred->ruid = new;
+    spinlock_release(&cur_cred->lock);
+    return 0;
+}