One telnet client at a time and ask for a password (it's 'xv6').

Hopefully this is enough to prevent all the random connections to josmp.

One telnet client at a time and ask for a password (it's 'xv6').
db8baf3d · Silas Boyd-Wickizer · 36c8e1dc · db8baf3d · db8baf3d · db8baf3d
--- a/Makefile
+++ b/Makefile
@@ -98,6 +98,7 @@ UPROGS= \
 	_forkexectree \
 	_forkexecbench \
 	_forktree \
+	_login \
 	_ls \
 	_mapbench \
 	_maptest \

--- a/login.cc
+++ b/login.cc
+#include "types.h"
+#include "user.h"
+
+static const char *
+readpw(void)
+{
+  static char pw[64];
+  for (int i = 0; i < sizeof(pw); i++) {
+    int r = read(0, &pw[i], 1);
+    if (r != 1)
+      return 0;
+    if (pw[i] == '\r') {
+      pw[i] = 0;
+    } else if (pw[i] == '\n') {
+      pw[i] = 0;
+      return pw;
+    }
+  }
+  return 0;
+}
+
+int
+main(void)
+{
+  const char *pw;
+
+  printf(1, "password: ");
+  pw = readpw();
+
+  if (pw && !strcmp(pw, "xv6")) {
+    static const char *argv[] = { "/sh", 0 };
+    exec(argv[0], argv);
+  }
+  exit();
+}
--- a/telnetd.cc
+++ b/telnetd.cc
@@ -46,16 +46,18 @@ main(void)
      continue;
    }
    if (pid == 0) {
-      static const char *argv[] = { "sh", 0 };
+      static const char *argv[] = { "/login", 0 };
      close(0);
      close(1);
      close(2);
      dup(ss);
      dup(ss);
      dup(ss);
-      exec("sh", argv);
+      exec(argv[0], argv);
      exit();
    }
    close(ss);
+    wait();
+    printf(1, "telnetd: connection closed\n");
  }
 }