kthd: verify permissions for chdir()

kthd/src/chdir.c

@@ -0,0 +1,41 @@
+/*
+ * luxOS - a unix-like operating system
+ * Omar Elghoul, 2024
+ * 
+ * kthd: Kernel Thread Helper Daemon
+ */
+
+#include <liblux/liblux.h>
+#include <sys/stat.h>
+#include <errno.h>
+
+void kthdChdir(ChdirCommand *cmd) {
+    cmd->header.header.response = 1;
+    cmd->header.header.length = sizeof(ChdirCommand);
+
+    // simply issue a stat() syscall and ensure the directory is valid
+    struct stat st;
+    if(stat(cmd->path, &st)) {
+        cmd->header.header.status = -1*errno;
+        luxSendLumen(cmd);
+        return;
+    }
+
+    if((st.st_mode & S_IFMT) != S_IFDIR) {
+        cmd->header.header.status = -ENOTDIR;
+        luxSendLumen(cmd);
+        return;
+    }
+
+    // ensure the requesting process has execute permissions on the directory
+    cmd->header.header.status = 0;
+    if(cmd->uid == st.st_uid) {
+        if(!(st.st_mode & S_IXUSR)) cmd->header.header.status = -EPERM;
+    } else if(cmd->gid == st.st_gid) {
+        if(!(st.st_mode & S_IXGRP)) cmd->header.header.status = -EPERM;
+    } else {
+        if(!(st.st_mode & S_IXOTH)) cmd->header.header.status = -EPERM;
+    }
+
+    luxSendLumen(cmd);
+}

kthd/src/main.c

@@ -9,6 +9,7 @@
 #include <stdlib.h>
 
 void kthdExec(ExecCommand *);
+void kthdChdir(ChdirCommand *);
 
 int main() {
     luxInit("kthd");
@@ -41,6 +42,7 @@ int main() {
 
             switch(msg->header.command) {
             case COMMAND_EXEC: kthdExec((ExecCommand *) msg); break;
+            case COMMAND_CHDIR: kthdChdir((ChdirCommand *) msg); break;
             default:
                 luxLogf(KPRINT_LEVEL_WARNING, "unimplemented command 0x%04X, dropping message...\n", msg->header.command);
             }