MDEV-15473 Isolate/sandbox PAM modules, so that they can't crash the server.

New version of PAM plugin (v2.0) added along with the old v1.0.
There the pam module is isolated in the auth_pam_tool application so
cannot crash the server.

.gitignore

@@ -100,6 +100,7 @@ pcre/pcre_chartables.c
 pcre/pcregrep
 pcre/pcretest
 pcre/test*grep
+plugin/auth_pam/auth_pam_tool
 plugin/aws_key_management/aws-sdk-cpp
 plugin/aws_key_management/aws_sdk_cpp
 plugin/aws_key_management/aws_sdk_cpp-prefix

debian/mariadb-server-10.3.install

@@ -40,6 +40,8 @@ usr/bin/wsrep_sst_xtrabackup
 usr/bin/wsrep_sst_xtrabackup-v2
 usr/lib/mysql/plugin/auth_ed25519.so
 usr/lib/mysql/plugin/auth_pam.so
+usr/lib/mysql/plugin/auth_pam_tool_dir/auth_pam_tool
+usr/lib/mysql/plugin/auth_pam_v1.so
 usr/lib/mysql/plugin/auth_socket.so
 usr/lib/mysql/plugin/disks.so
 usr/lib/mysql/plugin/file_key_management.so

mysql-test/mysql-test-run.pl

@@ -2603,8 +2603,22 @@ sub setup_vardir() {
         unlink "$plugindir/symlink_test";
       }
 
+      for (<$bindir/plugin/auth_pam/auth_pam_tool>)
+      {
+        mkpath("$plugindir/auth_pam_tool_dir");
+        if ($opt_use_copy)
+        {
+          copy rel2abs($_), "$plugindir/auth_pam_tool_dir/auth_pam_tool"
+        }
+        else
+        {
+          symlink rel2abs($_), "$plugindir/auth_pam_tool_dir/auth_pam_tool";
+        }
+      }
+
       for (<$bindir/storage/*/*.so>,
            <$bindir/plugin/*/*.so>,
+           <$bindir/plugin/*/auth_pam_tool_dir>,
            <$bindir/libmariadb/plugins/*/*.so>,
            <$bindir/libmariadb/*.so>,
            <$bindir/sql/*.so>)

mysql-test/suite/plugins/r/pam.result

@@ -20,6 +20,13 @@ Challenge input first.
 Enter: not very secret challenge
 Now, the magic number!
 PIN: ****
+#
+# athentication is unsuccessful
+#
+Challenge input first.
+Enter: crash pam module
+Now, the magic number!
+PIN: ***
 drop user test_pam;
 drop user pam_test;
 uninstall plugin pam;

mysql-test/suite/plugins/suite.pm

@@ -14,6 +14,8 @@ sub skip_combinations {
   my %skip;
   $skip{'t/pam.test'} = 'No pam setup for mtr'
              unless -e '/etc/pam.d/mariadb_mtr';
+  $skip{'t/pam_v1.test'} = 'No pam setup for mtr'
+             unless -e '/etc/pam.d/mariadb_mtr';
   $skip{'t/cassandra.test'} = 'Cassandra is not running'
              unless cassandra_running();
   $skip{'t/cassandra_qcache.test'} = $skip{'t/cassandra.test'};

mysql-test/suite/plugins/t/pam.test

@@ -13,6 +13,12 @@ not very secret challenge
 select user(), current_user(), database();
 EOF
 
+--write_file $MYSQLTEST_VARDIR/tmp/pam_ugly.txt
+crash pam module
+666
+select user(), current_user(), database();
+EOF
+
 --echo #
 --echo # athentication is successful, challenge/pin are ok
 --echo # note that current_user() differs from user()
@@ -25,6 +31,12 @@ EOF
 --error 1
 --exec $MYSQL_TEST -u test_pam --plugin-dir=$plugindir < $MYSQLTEST_VARDIR/tmp/pam_bad.txt
 
+--echo #
+--echo # athentication is unsuccessful
+--echo #
+--error 1
+--exec $MYSQL_TEST -u test_pam --plugin-dir=$plugindir < $MYSQLTEST_VARDIR/tmp/pam_ugly.txt
+
 --remove_file $MYSQLTEST_VARDIR/tmp/pam_good.txt
 --remove_file $MYSQLTEST_VARDIR/tmp/pam_bad.txt
 drop user test_pam;

mysql-test/suite/plugins/t/pam_init_v1.inc

+
+--source include/not_embedded.inc
+
+if (!$AUTH_PAM_V1_SO) {
+  skip No pam auth plugin;
+}
+
+eval install plugin pam soname '$AUTH_PAM_V1_SO';
+create user test_pam identified via pam using 'mariadb_mtr';
+create user pam_test;
+grant proxy on pam_test to test_pam;
+
+let $plugindir=`SELECT @@global.plugin_dir`;
+

mysql-test/suite/plugins/t/pam_v1.test

+
+--source pam_init.inc
+
+--write_file $MYSQLTEST_VARDIR/tmp/pam_good.txt
+not very secret challenge
+9225
+select user(), current_user(), database();
+EOF
+
+--write_file $MYSQLTEST_VARDIR/tmp/pam_bad.txt
+not very secret challenge
+9224
+select user(), current_user(), database();
+EOF
+
+--echo #
+--echo # athentication is successful, challenge/pin are ok
+--echo # note that current_user() differs from user()
+--echo #
+--exec $MYSQL_TEST -u test_pam --plugin-dir=$plugindir < $MYSQLTEST_VARDIR/tmp/pam_good.txt
+
+--echo #
+--echo # athentication is unsuccessful
+--echo #
+--error 1
+--exec $MYSQL_TEST -u test_pam --plugin-dir=$plugindir < $MYSQLTEST_VARDIR/tmp/pam_bad.txt
+
+--echo #
+--echo # pam module crashes
+--echo #
+--error 1
+--exec $MYSQL_TEST -u crash_pam_tool --plugin-dir=$plugindir < $MYSQLTEST_VARDIR/tmp/pam_good.txt
+
+--remove_file $MYSQLTEST_VARDIR/tmp/pam_good.txt
+--remove_file $MYSQLTEST_VARDIR/tmp/pam_bad.txt
+drop user test_pam;
+drop user pam_test;
+let $count_sessions= 1;
+--source include/wait_until_count_sessions.inc
+uninstall plugin pam;

plugin/auth_pam/CMakeLists.txt

@@ -8,6 +8,10 @@ IF(HAVE_PAM_APPL_H)
   IF(HAVE_STRNDUP)
     ADD_DEFINITIONS(-DHAVE_STRNDUP)
   ENDIF(HAVE_STRNDUP)
-  MYSQL_ADD_PLUGIN(auth_pam auth_pam.c LINK_LIBRARIES pam MODULE_ONLY)
+  ADD_DEFINITIONS(-D_GNU_SOURCE)
+  MYSQL_ADD_PLUGIN(auth_pam_v1 auth_pam_v1.c LINK_LIBRARIES pam MODULE_ONLY)
+  MYSQL_ADD_PLUGIN(auth_pam auth_pam.c LINK_LIBRARIES pam dl MODULE_ONLY)
+  MYSQL_ADD_EXECUTABLE(auth_pam_tool auth_pam_tool.c DESTINATION  ${INSTALL_PLUGINDIR}/auth_pam_tool_dir COMPONENT Server)
+  TARGET_LINK_LIBRARIES(auth_pam_tool pam)
 ENDIF(HAVE_PAM_APPL_H)
 

plugin/auth_pam/auth_pam_base.c

+/*
+   Copyright (c) 2011, 2018 MariaDB Corporation
+
+   This program is free software; you can redistribute it and/or modify
+   it under the terms of the GNU General Public License as published by
+   the Free Software Foundation; version 2 of the License.
+
+   This program is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+   GNU General Public License for more details.
+
+   You should have received a copy of the GNU General Public License
+   along with this program; if not, write to the Free Software
+   Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02111-1301 USA */
+
+/*
+  This file contains code to interact with the PAM module.
+  To be included into auth_pam_tool.c and auth_pam_v2.c,
+
+  Before the #include these sould be defined:
+  
+  struct param {
+    unsigned char buf[10240], *ptr;
+    MYSQL_PLUGIN_VIO *vio;
+    ...  other arbitrary fields allowed.
+  };
+  static int write_packet(struct param *param, const unsigned char *buf,
+                          int buf_len)
+  static int read_packet(struct param *param, unsigned char **pkt)
+*/
+
+#include <stdio.h>
+#include <string.h>
+#include <security/pam_appl.h>
+#include <security/pam_modules.h>
+
+/* It least solaris doesn't have strndup */
+
+#ifndef HAVE_STRNDUP
+char *strndup(const char *from, size_t length)
+{
+  char *ptr;
+  size_t max_length= strlen(from);
+  if (length > max_length)
+    length= max_length;
+  if ((ptr= (char*) malloc(length+1)) != 0)
+  {
+    memcpy((char*) ptr, (char*) from, length);
+    ptr[length]=0;
+  }
+  return ptr;
+}
+#endif
+
+#ifndef DBUG_OFF
+static char pam_debug = 0;
+#define PAM_DEBUG(X)   do { if (pam_debug) { fprintf X; } } while(0)
+#else
+#define PAM_DEBUG(X)   /* no-op */
+#endif
+
+static int conv(int n, const struct pam_message **msg,
+                struct pam_response **resp, void *data)
+{
+  struct param *param = (struct param *)data;
+  unsigned char *end = param->buf + sizeof(param->buf) - 1;
+  int i;
+
+  *resp = 0;
+
+  for (i = 0; i < n; i++)
+  {
+    /* if there's a message - append it to the buffer */
+    if (msg[i]->msg)
+    {
+      int len = strlen(msg[i]->msg);
+      if (len > end - param->ptr)
+        len = end - param->ptr;
+      if (len > 0)
+      {
+        memcpy(param->ptr, msg[i]->msg, len);
+        param->ptr+= len;
+        *(param->ptr)++ = '\n';
+      }
+    }
+    /* if the message style is *_PROMPT_*, meaning PAM asks a question,
+       send the accumulated text to the client, read the reply */
+    if (msg[i]->msg_style == PAM_PROMPT_ECHO_OFF ||
+        msg[i]->msg_style == PAM_PROMPT_ECHO_ON)
+    {
+      int pkt_len;
+      unsigned char *pkt;
+
+      /* allocate the response array.
+         freeing it is the responsibility of the caller */
+      if (*resp == 0)
+      {
+        *resp = calloc(sizeof(struct pam_response), n);
+        if (*resp == 0)
+          return PAM_BUF_ERR;
+      }
+
+      /* dialog plugin interprets the first byte of the packet
+         as the magic number.
+           2 means "read the input with the echo enabled"
+           4 means "password-like input, echo disabled"
+         C'est la vie. */
+      param->buf[0] = msg[i]->msg_style == PAM_PROMPT_ECHO_ON ? 2 : 4;
+      PAM_DEBUG((stderr, "PAM: conv: send(%.*s)\n",
+                (int)(param->ptr - param->buf - 1), param->buf));
+      if (write_packet(param, param->buf, param->ptr - param->buf - 1))
+        return PAM_CONV_ERR;
+
+      pkt_len = read_packet(param, &pkt);
+      if (pkt_len < 0)
+      {
+        PAM_DEBUG((stderr, "PAM: conv: recv() ERROR\n"));
+        return PAM_CONV_ERR;
+      }
+      PAM_DEBUG((stderr, "PAM: conv: recv(%.*s)\n", pkt_len, pkt));
+      /* allocate and copy the reply to the response array */
+      if (!((*resp)[i].resp= strndup((char*) pkt, pkt_len)))
+        return PAM_CONV_ERR;
+      param->ptr = param->buf + 1;
+    }
+  }
+  return PAM_SUCCESS;
+}
+
+#define DO(X) if ((status = (X)) != PAM_SUCCESS) goto end
+
+#if defined(SOLARIS) || defined(__sun)
+typedef void** pam_get_item_3_arg;
+#else
+typedef const void** pam_get_item_3_arg;
+#endif
+
+static int pam_auth_base(struct param *param, MYSQL_SERVER_AUTH_INFO *info)
+{
+  pam_handle_t *pamh = NULL;
+  int status;
+  const char *new_username= NULL;
+  /* The following is written in such a way to make also solaris happy */
+  struct pam_conv pam_start_arg = { &conv, (char*) param };
+
+  /*
+    get the service name, as specified in
+
+     CREATE USER ... IDENTIFIED WITH pam AS "service"
+  */
+  const char *service = info->auth_string && info->auth_string[0]
+                          ? info->auth_string : "mysql";
+
+  param->ptr = param->buf + 1;
+
+  PAM_DEBUG((stderr, "PAM: pam_start(%s, %s)\n", service, info->user_name));
+  DO( pam_start(service, info->user_name, &pam_start_arg, &pamh) );
+
+  PAM_DEBUG((stderr, "PAM: pam_authenticate(0)\n"));
+  DO( pam_authenticate (pamh, 0) );
+
+  PAM_DEBUG((stderr, "PAM: pam_acct_mgmt(0)\n"));
+  DO( pam_acct_mgmt(pamh, 0) );
+
+  PAM_DEBUG((stderr, "PAM: pam_get_item(PAM_USER)\n"));
+  DO( pam_get_item(pamh, PAM_USER, (pam_get_item_3_arg) &new_username) );
+
+  if (new_username && strcmp(new_username, info->user_name))
+    strncpy(info->authenticated_as, new_username,
+            sizeof(info->authenticated_as));
+  info->authenticated_as[sizeof(info->authenticated_as)-1]= 0;
+
+end:
+  pam_end(pamh, status);
+  PAM_DEBUG((stderr, "PAM: status = %d user = %s\n", status, info->authenticated_as));
+  return status == PAM_SUCCESS ? CR_OK : CR_ERROR;
+}
+

plugin/auth_pam/auth_pam_common.c

+/*
+   Copyright (c) 2011, 2018 MariaDB Corporation
+
+   This program is free software; you can redistribute it and/or modify
+   it under the terms of the GNU General Public License as published by
+   the Free Software Foundation; version 2 of the License.
+
+   This program is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+   GNU General Public License for more details.
+
+   You should have received a copy of the GNU General Public License
+   along with this program; if not, write to the Free Software
+   Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02111-1301 USA */
+
+/*
+  In this file we gather the plugin interface definitions
+  that are same in all the PAM plugin versions.
+  To be included into auth_pam.c and auth_pam_v1.c.
+*/
+
+static struct st_mysql_auth info =
+{
+  MYSQL_AUTHENTICATION_INTERFACE_VERSION,
+  "dialog",
+  pam_auth
+};
+
+static char use_cleartext_plugin;
+static MYSQL_SYSVAR_BOOL(use_cleartext_plugin, use_cleartext_plugin,
+       PLUGIN_VAR_NOCMDARG | PLUGIN_VAR_READONLY,
+       "Use mysql_cleartext_plugin on the client side instead of the dialog "
+       "plugin. This may be needed for compatibility reasons, but it only "
+       "supports simple PAM policies that don't require anything besides "
+       "a password", NULL, NULL, 0);
+
+#ifndef DBUG_OFF
+static MYSQL_SYSVAR_BOOL(debug, pam_debug, PLUGIN_VAR_OPCMDARG,
+       "Log all PAM activity", NULL, NULL, 0);
+#endif
+
+
+static struct st_mysql_sys_var* vars[] = {
+  MYSQL_SYSVAR(use_cleartext_plugin),
+#ifndef DBUG_OFF
+  MYSQL_SYSVAR(debug),
+#endif
+  NULL
+};

plugin/auth_pam/auth_pam_tool.c

+/*
+   Copyright (c) 2011, 2018 MariaDB Corporation
+
+   This program is free software; you can redistribute it and/or modify
+   it under the terms of the GNU General Public License as published by
+   the Free Software Foundation; version 2 of the License.
+
+   This program is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+   GNU General Public License for more details.
+
+   You should have received a copy of the GNU General Public License
+   along with this program; if not, write to the Free Software
+   Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02111-1301 USA */
+
+#include <stdlib.h>
+#include <unistd.h>
+#include <mysql/plugin_auth_common.h>
+
+struct param {
+  unsigned char buf[10240], *ptr;
+};
+
+
+#include "auth_pam_tool.h"
+
+
+static int write_packet(struct param *param  __attribute__((unused)),
+                        const unsigned char *buf, int buf_len)
+{
+  unsigned char b=  AP_CONV;
+  return write(1, &b, 1) < 1 ||
+         write_string(1, buf, buf_len);
+}
+
+
+static int read_packet(struct param *param, unsigned char **pkt)
+{
+  *pkt= (unsigned char *) param->buf;
+  return read_string(0, (char *) param->buf, (int) sizeof(param->buf)) - 1;
+}
+
+
+typedef struct st_mysql_server_auth_info
+{
+  /**
+    User name as sent by the client and shown in USER().
+    NULL if the client packet with the user name was not received yet.
+  */
+  char *user_name;
+
+  /**
+    A corresponding column value from the mysql.user table for the
+    matching account name
+  */
+  char *auth_string;
+
+  /**
+    Matching account name as found in the mysql.user table.
+    A plugin can override it with another name that will be
+    used by MySQL for authorization, and shown in CURRENT_USER()
+  */
+  char authenticated_as[MYSQL_USERNAME_LENGTH+1]; 
+} MYSQL_SERVER_AUTH_INFO;
+
+
+#include "auth_pam_base.c"
+
+
+int main(int argc, char **argv)
+{
+  struct param param;
+  MYSQL_SERVER_AUTH_INFO info;
+  unsigned char field;
+  int res;
+  char a_buf[MYSQL_USERNAME_LENGTH + 1 + 1024];
+
+  if (read(0, &field, 1) < 1)
+    return -1;
+#ifndef DBUG_OFF
+  pam_debug= field;
+#endif
+  
+  PAM_DEBUG((stderr, "PAM: sandbox started [%s].\n", argv[0]));
+
+  info.user_name= a_buf;
+  if ((res= read_string(0, info.user_name, sizeof(a_buf))) < 0)
+    return -1;
+  PAM_DEBUG((stderr, "PAM: sandbox username [%s].\n", info.user_name));
+
+  info.auth_string= info.user_name + res + 1;
+  if (read_string(0, info.auth_string, sizeof(a_buf) - 1 - res) < 0)
+    return -1;
+
+  PAM_DEBUG((stderr, "PAM: sandbox auth string [%s].\n", info.auth_string));
+
+  if ((res= pam_auth_base(&param, &info)) != CR_OK)
+  {
+    PAM_DEBUG((stderr, "PAM: auth failed, sandbox closed.\n"));
+    return -1;
+  }
+
+  if (info.authenticated_as[0])
+  {
+    PAM_DEBUG((stderr, "PAM: send authenticated_as field.\n"));
+    field= AP_AUTHENTICATED_AS;
+    if (write(1, &field, 1) < 1 ||
+        write_string(1, (unsigned char *) info.authenticated_as,
+                     strlen(info.authenticated_as)))
+      return -1;
+  }
+  
+  PAM_DEBUG((stderr, "PAM: send OK result.\n"));
+  field= AP_EOF;
+  if (write(1, &field, 1) != 1)
+    return -1;
+
+  PAM_DEBUG((stderr, "PAM: sandbox closed.\n"));
+  return 0;
+}

plugin/auth_pam/auth_pam_tool.h

+/*
+   Copyright (c) 2011, 2018 MariaDB Corporation
+
+   This program is free software; you can redistribute it and/or modify
+   it under the terms of the GNU General Public License as published by
+   the Free Software Foundation; version 2 of the License.
+
+   This program is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+   GNU General Public License for more details.
+
+   You should have received a copy of the GNU General Public License
+   along with this program; if not, write to the Free Software
+   Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02111-1301 USA */
+
+/*
+  This file contains definitions and functions for
+  the interface between the auth_pam.so (PAM plugin version 2)
+  and the auth_pam_tool executable.
+  To be included both in auth_pam.c and auth_pam_tool.c.
+*/
+
+#define AP_AUTHENTICATED_AS 'A'
+#define AP_CONV 'C'
+#define AP_EOF 'E'
+
+
+static int read_length(int file)
+{
+  unsigned char hdr[2];
+
+  if (read(file, hdr, 2) < 2)
+    return -1;
+
+  return (((int) hdr[0]) << 8) + (int) hdr[1];
+}
+
+
+static void store_length(int len, unsigned char *p_len)
+{
+  p_len[0]= (unsigned char) ((len >> 8) & 0xFF);
+  p_len[1]= (unsigned char) (len  & 0xFF);
+}
+
+
+/*
+  Returns the length of the string read,
+  or -1 on error.
+*/
+
+static int read_string(int file, char *s, int s_size)
+{
+  int len;
+
+  len= read_length(file);
+
+  if (len < 0 || len > s_size-1 ||
+      read(file, s, len) < len)
+    return -1;
+
+  s[len]= 0;
+
+  return len;
+}
+
+
+/*
+  Returns 0 on success.
+*/
+
+static int write_string(int file, const unsigned char *s, int s_len)
+{
+  unsigned char hdr[2];
+  store_length(s_len, hdr);
+  return write(file, hdr, 2) < 2 ||
+         write(file, s, s_len) < s_len;
+}
+
+
+#define MAX_PAM_SERVICE_NAME 1024

plugin/auth_pam/auth_pam_v1.c

+/*
+   Copyright (c) 2011, 2018 MariaDB Corporation
+
+   This program is free software; you can redistribute it and/or modify
+   it under the terms of the GNU General Public License as published by
+   the Free Software Foundation; version 2 of the License.
+
+   This program is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+   GNU General Public License for more details.
+
+   You should have received a copy of the GNU General Public License
+   along with this program; if not, write to the Free Software
+   Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02111-1301 USA */
+
+#include <mysql/plugin_auth.h>
+
+struct param {
+  unsigned char buf[10240], *ptr;
+  MYSQL_PLUGIN_VIO *vio;
+};
+
+static int write_packet(struct param *param, const unsigned char *buf,
+                        int buf_len)
+{
+  return param->vio->write_packet(param->vio, buf, buf_len);
+}
+
+static int read_packet(struct param *param, unsigned char **pkt)
+{
+  return param->vio->read_packet(param->vio, pkt);
+}
+
+#include "auth_pam_base.c"
+
+static int pam_auth(MYSQL_PLUGIN_VIO *vio, MYSQL_SERVER_AUTH_INFO *info)
+{
+  struct param param;
+  param.vio = vio;
+  return pam_auth_base(&param, info);
+}
+
+
+#include "auth_pam_common.c"
+
+
+static int init(void *p __attribute__((unused)))
+{
+  if (use_cleartext_plugin)
+    info.client_auth_plugin= "mysql_clear_password";
+  return 0;
+}
+
+maria_declare_plugin(pam)
+{
+  MYSQL_AUTHENTICATION_PLUGIN,
+  &info,
+  "pam",
+  "Sergei Golubchik",
+  "PAM based authentication",
+  PLUGIN_LICENSE_GPL,
+  init,
+  NULL,
+  0x0100,
+  NULL,
+  vars,
+  "1.0",
+  MariaDB_PLUGIN_MATURITY_STABLE
+}
+maria_declare_plugin_end;

plugin/auth_pam/testing/pam_mariadb_mtr.c

@@ -58,7 +58,17 @@ int pam_sm_authenticate(pam_handle_t *pamh, int flags,
   if (strlen(r1) == atoi(r2) % 100)
     retval = PAM_SUCCESS;
   else
+  {
+    /* Produce the crash for testing purposes. */
+    if ((strlen(r1) == 16) &&
+        memcmp(r1, "crash pam module", 16) == 0 &&
+        atoi(r2) == 666)
+    {
+      r1= 0;
+      *((struct pam_message *) r1)= msg[0];
+    }
     retval = PAM_AUTH_ERR;
+  }
 
   if (argc > 0 && argv[0])
     pam_set_item(pamh, PAM_USER, argv[0]);