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.

16 files changed, 743 insertions, 154 deletions

diff --git a/.gitignore b/.gitignore
index 832df90347b..ae36c2696af 100644
--- a/.gitignore
+++ b/.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
diff --git a/debian/mariadb-server-10.3.install b/debian/mariadb-server-10.3.install
index a7d4d665892..106b3a12de7 100644
--- a/debian/mariadb-server-10.3.install
+++ b/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
diff --git a/mysql-test/mysql-test-run.pl b/mysql-test/mysql-test-run.pl
index 6586e51dcd2..02a35e85d4b 100755
--- a/mysql-test/mysql-test-run.pl
+++ b/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>)
diff --git a/mysql-test/suite/plugins/r/pam.result b/mysql-test/suite/plugins/r/pam.result
index 86303206b3b..a16cd7f3d43 100644
--- a/mysql-test/suite/plugins/r/pam.result
+++ b/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;
diff --git a/mysql-test/suite/plugins/suite.pm b/mysql-test/suite/plugins/suite.pm
index a2ac3957af0..346f28cf696 100644
--- a/mysql-test/suite/plugins/suite.pm
+++ b/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'};
diff --git a/mysql-test/suite/plugins/t/pam.test b/mysql-test/suite/plugins/t/pam.test
index 8a95d6baed2..852f1652bea 100644
--- a/mysql-test/suite/plugins/t/pam.test
+++ b/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 $MYSQLTEST_VARDIR/tmp/pam_bad.txt
 drop user test_pam;
diff --git a/mysql-test/suite/plugins/t/pam_init_v1.inc b/mysql-test/suite/plugins/t/pam_init_v1.inc
new file mode 100644
index 00000000000..4861d4fdbf0
--- /dev/null
+++ b/mysql-test/suite/plugins/t/pam_init_v1.inc
@@ -0,0 +1,14 @@
+
+--source include/not_embedded.inc
+
+if (!$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`;
+
diff --git a/mysql-test/suite/plugins/t/pam_v1.test b/mysql-test/suite/plugins/t/pam_v1.test
new file mode 100644
index 00000000000..f8a346e0e4c
--- /dev/null
+++ b/mysql-test/suite/plugins/t/pam_v1.test
@@ -0,0 +1,40 @@
+
+--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;
diff --git a/plugin/auth_pam/CMakeLists.txt b/plugin/auth_pam/CMakeLists.txt
index 51317527c77..4943d576a0d 100644
--- a/plugin/auth_pam/CMakeLists.txt
+++ b/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)
 
diff --git a/plugin/auth_pam/auth_pam.c b/plugin/auth_pam/auth_pam.c
index ffc3d6f5537..1ffc3285a3d 100644
--- a/plugin/auth_pam/auth_pam.c
+++ b/plugin/auth_pam/auth_pam.c
@@ -1,5 +1,5 @@
 /*
-   Copyright (c) 2011, 2012, Monty Program Ab
+   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
@@ -14,36 +14,12 @@
    along with this program; if not, write to the Free Software
    Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02111-1301 USA */
 
-#define _GNU_SOURCE 1 /* for strndup */
 
-#include <mysql/plugin_auth.h>
-#include <stdio.h>
+#include <unistd.h>
 #include <string.h>
-#include <security/pam_appl.h>
-#include <security/pam_modules.h>
-
-struct param {
-  unsigned char buf[10240], *ptr;
-  MYSQL_PLUGIN_VIO *vio;
-};
-
-/* 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
+#include <mysql/plugin_auth.h>
+#include "auth_pam_tool.h"
+#include <my_global.h>
 
 #ifndef DBUG_OFF
 static char pam_debug = 0;
@@ -52,158 +28,163 @@ static char pam_debug = 0;
 #define PAM_DEBUG(X)   /* no-op */
 #endif
 
-static int conv(int n, const struct pam_message **msg,
-                struct pam_response **resp, void *data)
+static char *opt_plugin_dir; /* To be dynamically linked. */
+static const char *tool_name= "auth_pam_tool_dir/auth_pam_tool";
+static const int tool_name_len= 31;
+
+static int pam_auth(MYSQL_PLUGIN_VIO *vio, MYSQL_SERVER_AUTH_INFO *info)
 {
-  struct param *param = (struct param *)data;
-  unsigned char *end = param->buf + sizeof(param->buf) - 1;
-  int i;
+  int p_to_c[2], c_to_p[2]; /* Parent-to-child and child-to-parent pipes. */
+  pid_t proc_id;
+  int result= CR_ERROR;
+  unsigned char field;
 
-  *resp = 0;
+  PAM_DEBUG((stderr, "PAM: opening pipes.\n"));
+  if (pipe(p_to_c) < 0 || pipe(c_to_p) < 0)
+  {
+    /* Error creating pipes. */
+    return CR_ERROR;
+  }
+  PAM_DEBUG((stderr, "PAM: forking.\n"));
+  if ((proc_id= fork()) < 0)
+  {
+    /* Error forking. */
+    close(p_to_c[0]);
+    close(c_to_p[1]);
+    goto error_ret;
+  }
 
-  for (i = 0; i < n; i++)
+  if (proc_id == 0)
   {
-    /* if there's a message - append it to the buffer */
-    if (msg[i]->msg)
+    /* The 'sandbox' process started. */
+    char toolpath[FN_REFLEN];
+    size_t plugin_dir_len= strlen(opt_plugin_dir);
+
+    PAM_DEBUG((stderr, "PAM: Child process prepares pipes.\n"));
+    
+    if (close(p_to_c[1]) < 0 ||
+        close(c_to_p[0]) < 0 ||
+        dup2(p_to_c[0], 0) < 0 || /* Parent's pipe to STDIN. */
+        dup2(c_to_p[1], 1) < 0)   /* Sandbox's pipe to STDOUT. */
     {
-      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';
-      }
+      exit(-1);
     }
-    /* 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)
+
+    PAM_DEBUG((stderr, "PAM: check tool directory: %s, %s.\n",
+                       opt_plugin_dir, tool_name));
+    if (plugin_dir_len + tool_name_len + 2 > sizeof(toolpath))
     {
-      int pkt_len;
-      unsigned char *pkt;
+      /* Tool path too long. */
+      exit(-1);
+    }
 
-      /* 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;
-      }
+    memcpy(toolpath, opt_plugin_dir, plugin_dir_len);
+    if (plugin_dir_len && toolpath[plugin_dir_len-1] != FN_LIBCHAR)
+      toolpath[plugin_dir_len++]= FN_LIBCHAR;
+    memcpy(toolpath+plugin_dir_len, tool_name, tool_name_len+1);
 
-      /* 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 (param->vio->write_packet(param->vio, param->buf, param->ptr - param->buf - 1))
-        return PAM_CONV_ERR;
-
-      pkt_len = param->vio->read_packet(param->vio, &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;
-    }
+    PAM_DEBUG((stderr, "PAM: execute pam sandbox [%s].\n", toolpath));
+    (void) execl(toolpath, toolpath, NULL);
+    PAM_DEBUG((stderr, "PAM: exec() failed.\n"));
+    exit(-1);
   }
-  return PAM_SUCCESS;
-}
 
-#define DO(X) if ((status = (X)) != PAM_SUCCESS) goto end
+  /* Parent process continues. */
 
-#if defined(SOLARIS) || defined(__sun)
-typedef void** pam_get_item_3_arg;
-#else
-typedef const void** pam_get_item_3_arg;
-#endif
+  PAM_DEBUG((stderr, "PAM: parent continues.\n"));
+  if (close(p_to_c[0]) < 0 ||
+      close(c_to_p[1]) < 0)
+    goto error_ret;
 
-static int pam_auth(MYSQL_PLUGIN_VIO *vio, MYSQL_SERVER_AUTH_INFO *info)
-{
-  pam_handle_t *pamh = NULL;
-  int status;
-  const char *new_username= NULL;
-  struct param param;
-  /* 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
+  PAM_DEBUG((stderr, "PAM: parent sends user data [%s], [%s].\n",
+               info->user_name, info->auth_string));
 
-     CREATE USER ... IDENTIFIED WITH pam AS "service"
-  */
-  const char *service = info->auth_string && info->auth_string[0]
-                          ? info->auth_string : "mysql";
+#ifndef DBUG_OFF
+  field= pam_debug;
+#else
+  field= 0;
+#endif
+  if (write(p_to_c[1], &field, 1) != 1 ||
+      write_string(p_to_c[1], (const uchar *) info->user_name,
+                                       info->user_name_length) ||
+      write_string(p_to_c[1], (const uchar *) info->auth_string,
+                                      info->auth_string_length))
+    goto error_ret;
+
+  for (;;)
+  {
+    PAM_DEBUG((stderr, "PAM: listening to the sandbox.\n"));
+    if (read(c_to_p[0], &field, 1) < 1)
+    {
+      PAM_DEBUG((stderr, "PAM: read failed.\n"));
+      goto error_ret;
+    }
 
-  param.ptr = param.buf + 1;
-  param.vio = vio;
+    if (field == AP_EOF)
+    {
+      PAM_DEBUG((stderr, "PAM: auth OK returned.\n"));
+      break;
+    }
 
-  PAM_DEBUG((stderr, "PAM: pam_start(%s, %s)\n", service, info->user_name));
-  DO( pam_start(service, info->user_name, &pam_start_arg, &pamh) );
+    switch (field)
+    {
+    case AP_AUTHENTICATED_AS:
+      PAM_DEBUG((stderr, "PAM: reading authenticated_as string.\n"));
+      if (read_string(c_to_p[0], info->authenticated_as,
+                      sizeof(info->authenticated_as) - 1) < 0)
+        goto error_ret;
+      break;
+
+    case AP_CONV:
+      {
+        unsigned char buf[10240];
+        int buf_len;
+        unsigned char *pkt;
 
-  PAM_DEBUG((stderr, "PAM: pam_authenticate(0)\n"));
-  DO( pam_authenticate (pamh, 0) );
+        PAM_DEBUG((stderr, "PAM: getting CONV string.\n"));
+        if ((buf_len= read_string(c_to_p[0], (char *) buf, sizeof(buf))) < 0)
+          goto error_ret;
 
-  PAM_DEBUG((stderr, "PAM: pam_acct_mgmt(0)\n"));
-  DO( pam_acct_mgmt(pamh, 0) );
+        PAM_DEBUG((stderr, "PAM: sending CONV string.\n"));
+        if (vio->write_packet(vio, buf, buf_len))
+          goto error_ret;
 
-  PAM_DEBUG((stderr, "PAM: pam_get_item(PAM_USER)\n"));
-  DO( pam_get_item(pamh, PAM_USER, (pam_get_item_3_arg) &new_username) );
+        PAM_DEBUG((stderr, "PAM: reading CONV answer.\n"));
+        if ((buf_len= vio->read_packet(vio, &pkt)) < 0)
+          goto error_ret;
 
-  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;
+        PAM_DEBUG((stderr, "PAM: answering CONV.\n"));
+        if (write_string(p_to_c[1], pkt, buf_len))
+          goto error_ret;
+      }
+      break;
 
-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;
-}
+    default:
+      PAM_DEBUG((stderr, "PAM: unknown sandbox field.\n"));
+      goto error_ret;
+    }
+  }
+  result= CR_OK;
 
-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);
+error_ret:
+  close(p_to_c[1]);
+  close(c_to_p[0]);
 
-#ifndef DBUG_OFF
-static MYSQL_SYSVAR_BOOL(debug, pam_debug, PLUGIN_VAR_OPCMDARG,
-       "Log all PAM activity", NULL, NULL, 0);
-#endif
+  PAM_DEBUG((stderr, "PAM: auth result %d.\n", result));
+  return result;
+}
 
 
-static struct st_mysql_sys_var* vars[] = {
-  MYSQL_SYSVAR(use_cleartext_plugin),
-#ifndef DBUG_OFF
-  MYSQL_SYSVAR(debug),
-#endif
-  NULL
-};
+#include "auth_pam_common.c"
 
 
 static int init(void *p __attribute__((unused)))
 {
   if (use_cleartext_plugin)
     info.client_auth_plugin= "mysql_clear_password";
+  if (!(opt_plugin_dir= dlsym(RTLD_DEFAULT, "opt_plugin_dir")))
+    return 1;
   return 0;
 }
 
@@ -212,15 +193,15 @@ maria_declare_plugin(pam)
   MYSQL_AUTHENTICATION_PLUGIN,
   &info,
   "pam",
-  "Sergei Golubchik",
+  "MariaDB Corp",
   "PAM based authentication",
   PLUGIN_LICENSE_GPL,
   init,
   NULL,
-  0x0100,
+  0x0200,
   NULL,
   vars,
-  "1.0",
-  MariaDB_PLUGIN_MATURITY_STABLE
+  "2.0",
+  MariaDB_PLUGIN_MATURITY_BETA
 }
 maria_declare_plugin_end;
diff --git a/plugin/auth_pam/auth_pam_base.c b/plugin/auth_pam/auth_pam_base.c
new file mode 100644
index 00000000000..68be0e92b71
--- /dev/null
+++ b/plugin/auth_pam/auth_pam_base.c
@@ -0,0 +1,179 @@
+/*
+   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;
+}
+
diff --git a/plugin/auth_pam/auth_pam_common.c b/plugin/auth_pam/auth_pam_common.c
new file mode 100644
index 00000000000..1fbd5b12d3a
--- /dev/null
+++ b/plugin/auth_pam/auth_pam_common.c
@@ -0,0 +1,50 @@
+/*
+   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
+};
diff --git a/plugin/auth_pam/auth_pam_tool.c b/plugin/auth_pam/auth_pam_tool.c
new file mode 100644
index 00000000000..3f7015952a0
--- /dev/null
+++ b/plugin/auth_pam/auth_pam_tool.c
@@ -0,0 +1,121 @@
+/*
+   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;
+}
diff --git a/plugin/auth_pam/auth_pam_tool.h b/plugin/auth_pam/auth_pam_tool.h
new file mode 100644
index 00000000000..60ae016db72
--- /dev/null
+++ b/plugin/auth_pam/auth_pam_tool.h
@@ -0,0 +1,81 @@
+/*
+   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
diff --git a/plugin/auth_pam/auth_pam_v1.c b/plugin/auth_pam/auth_pam_v1.c
new file mode 100644
index 00000000000..ab352b1492b
--- /dev/null
+++ b/plugin/auth_pam/auth_pam_v1.c
@@ -0,0 +1,71 @@
+/*
+   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;
diff --git a/plugin/auth_pam/testing/pam_mariadb_mtr.c b/plugin/auth_pam/testing/pam_mariadb_mtr.c
index 473ec246fe0..44af584d7f0 100644
--- a/plugin/auth_pam/testing/pam_mariadb_mtr.c
+++ b/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]);