pam_pwhistory: add helper to handle SELinux

The purpose of the helper is to enable tighter confinement of login and
password changing services. The helper is thus called only when SELinux
is enabled on the system.

Resolves: https://github.com/linux-pam/linux-pam/pull/247

1 files changed, 119 insertions, 0 deletions

diff --git a/modules/pam_pwhistory/pwhistory_helper.c b/modules/pam_pwhistory/pwhistory_helper.c
new file mode 100644
index 00000000..b08a14a7
--- /dev/null
+++ b/modules/pam_pwhistory/pwhistory_helper.c
@@ -0,0 +1,119 @@
+/*
+ * Copyright (c) 2013 Red Hat, Inc.
+ * Author: Tomas Mraz <tmraz@redhat.com>
+ *
+ * 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, and the entire permission notice in its entirety,
+ *    including the disclaimer of warranties.
+ * 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. The name of the author may not be used to endorse or promote
+ *    products derived from this software without specific prior
+ *    written permission.
+ *
+ * ALTERNATIVELY, this product may be distributed under the terms of
+ * the GNU Public License, in which case the provisions of the GPL are
+ * required INSTEAD OF the above restrictions.  (This clause is
+ * necessary due to a potential bad interaction between the GPL and
+ * the restrictions contained in a BSD-style copyright.)
+ *
+ * THIS SOFTWARE IS PROVIDED ``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 AUTHOR 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 "config.h"
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <syslog.h>
+#include <errno.h>
+#include <unistd.h>
+#include <signal.h>
+#include <security/_pam_types.h>
+#include <security/_pam_macros.h>
+#include <security/pam_modutil.h>
+#include "opasswd.h"
+#include "pam_inline.h"
+
+
+static int
+check_history(const char *user, const char *debug)
+{
+  char pass[PAM_MAX_RESP_SIZE + 1];
+  char *passwords[] = { pass };
+  int npass;
+  int dbg = atoi(debug); /* no need to be too fancy here */
+  int retval;
+
+  /* read the password from stdin (a pipe from the pam_pwhistory module) */
+  npass = pam_read_passwords(STDIN_FILENO, 1, passwords);
+
+  if (npass != 1)
+    { /* is it a valid password? */
+      helper_log_err(LOG_DEBUG, "no password supplied");
+      return PAM_AUTHTOK_ERR;
+    }
+
+  retval = check_old_pass(user, pass, dbg);
+
+  memset(pass, '\0', PAM_MAX_RESP_SIZE);	/* clear memory of the password */
+
+  return retval;
+}
+
+static int
+save_history(const char *user, const char *howmany, const char *debug)
+{
+  int num = atoi(howmany);
+  int dbg = atoi(debug); /* no need to be too fancy here */
+  int retval;
+
+  retval = save_old_pass(user, num, dbg);
+
+  return retval;
+}
+
+int
+main(int argc, char *argv[])
+{
+  const char *option;
+  const char *user;
+
+  /*
+   * we establish that this program is running with non-tty stdin.
+   * this is to discourage casual use.
+   */
+
+  if (isatty(STDIN_FILENO) || argc < 4)
+    {
+      fprintf(stderr,
+            "This binary is not designed for running in this way.\n");
+      return PAM_SYSTEM_ERR;
+    }
+
+  option = argv[1];
+  user = argv[2];
+
+  if (strcmp(option, "check") == 0 && argc == 4)
+    return check_history(user, argv[3]);
+  else if (strcmp(option, "save") == 0 && argc == 5)
+    return save_history(user, argv[3], argv[4]);
+
+  fprintf(stderr, "This binary is not designed for running in this way.\n");
+
+  return PAM_SYSTEM_ERR;
+}