Adding upstream version 6.0.4-dfsg.upstream/6.0.4-dfsgupstream

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 898 insertions, 0 deletions

diff --git a/src/VBox/Additions/common/pam/pam_vbox.cpp b/src/VBox/Additions/common/pam/pam_vbox.cpp
new file mode 100644
index 00000000..b3ad83e5
--- /dev/null
+++ b/src/VBox/Additions/common/pam/pam_vbox.cpp
@@ -0,0 +1,898 @@
+/* $Id: pam_vbox.cpp $ */
+/** @file
+ * pam_vbox - PAM module for auto logons.
+ */
+
+/*
+ * Copyright (C) 2008-2019 Oracle Corporation
+ *
+ * This file is part of VirtualBox Open Source Edition (OSE), as
+ * available from http://www.virtualbox.org. This file is free software;
+ * you can redistribute it and/or modify it under the terms of the GNU
+ * General Public License (GPL) as published by the Free Software
+ * Foundation, in version 2 as it comes in the "COPYING" file of the
+ * VirtualBox OSE distribution. VirtualBox OSE is distributed in the
+ * hope that it will be useful, but WITHOUT ANY WARRANTY of any kind.
+ */
+
+
+/*********************************************************************************************************************************
+*   Header Files                                                                                                                 *
+*********************************************************************************************************************************/
+#define PAM_SM_AUTH
+#define PAM_SM_ACCOUNT
+#define PAM_SM_PASSWORD
+#define PAM_SM_SESSION
+
+#ifdef DEBUG
+# define PAM_DEBUG
+#endif
+
+#include <security/pam_appl.h>
+#ifdef RT_OS_LINUX
+# include <security/_pam_macros.h>
+#endif
+
+#include <pwd.h>
+#include <syslog.h>
+#include <stdlib.h>
+
+#include <iprt/assert.h>
+#include <iprt/buildconfig.h>
+#include <iprt/env.h>
+#include <iprt/initterm.h>
+#include <iprt/mem.h>
+#include <iprt/stream.h>
+#include <iprt/string.h>
+#include <iprt/thread.h>
+#include <iprt/time.h>
+
+#include <VBox/VBoxGuestLib.h>
+
+#include <VBox/log.h>
+#ifdef VBOX_WITH_GUEST_PROPS
+# include <VBox/HostServices/GuestPropertySvc.h>
+#endif
+
+#define VBOX_MODULE_NAME                    "pam_vbox"
+
+#define VBOX_PAM_FLAG_SILENT                "PAM_SILENT"
+#define VBOX_PAM_FLAG_DISALLOW_NULL_AUTHTOK "PAM_DISALLOW_NULL_AUTHTOK"
+#define VBOX_PAM_FLAG_ESTABLISH_CRED        "PAM_ESTABLISH_CRED"
+#define VBOX_PAM_FLAG_DELETE_CRED           "PAM_DELETE_CRED"
+#define VBOX_PAM_FLAG_REINITIALIZE_CRED     "PAM_REINITIALIZE_CRED"
+#define VBOX_PAM_FLAG_REFRESH_CRED          "PAM_REFRESH_CRED"
+
+RT_C_DECLS_BEGIN
+RTDECL(int) pam_sm_authenticate(pam_handle_t *hPAM, int iFlags, int argc, const char **argv);
+RTDECL(int) pam_sm_setcred(pam_handle_t *hPAM, int iFlags, int argc, const char **argv);
+RTDECL(int) pam_sm_acct_mgmt(pam_handle_t *hPAM, int iFlags, int argc, const char **argv);
+RTDECL(int) pam_sm_open_session(pam_handle_t *hPAM, int iFlags, int argc, const char **argv);
+RTDECL(int) pam_sm_close_session(pam_handle_t *hPAM, int iFlags, int argc, const char **argv);
+RTDECL(int) pam_sm_chauthtok(pam_handle_t *hPAM, int iFlags, int argc, const char **argv);
+RT_C_DECLS_END
+
+/** For debugging. */
+#ifdef DEBUG
+static pam_handle_t *g_pam_handle;
+static int g_verbosity = 99;
+#else
+static int g_verbosity = 0;
+#endif
+
+/**
+ * User-provided thread data for the credentials waiting thread.
+ */
+typedef struct PAMVBOXTHREAD
+{
+    /** The PAM handle. */
+    pam_handle_t *hPAM;
+    /** The timeout (in ms) to wait for credentials. */
+    uint32_t      uTimeoutMS;
+    /** The overall result of the thread operation. */
+    int           rc;
+} PAMVBOXTHREAD, *PPAMVBOXTHREAD;
+
+/**
+ * Write to system log.
+ *
+ * @param  pszBuf                   Buffer to write to the log (NULL-terminated)
+ */
+static void pam_vbox_writesyslog(char *pszBuf)
+{
+#ifdef RT_OS_LINUX
+    openlog("pam_vbox", LOG_PID, LOG_AUTHPRIV);
+    syslog(LOG_ERR, "%s", pszBuf);
+    closelog();
+#elif defined(RT_OS_SOLARIS)
+    syslog(LOG_ERR, "pam_vbox: %s\n", pszBuf);
+#endif
+}
+
+
+/**
+ * Displays an error message.
+ *
+ * @param   hPAM                    PAM handle.
+ * @param   pszFormat               The message text.
+ * @param   ...                     Format arguments.
+ */
+static void pam_vbox_error(pam_handle_t *hPAM, const char *pszFormat, ...)
+{
+    RT_NOREF1(hPAM);
+    va_list va;
+    char *buf;
+    va_start(va, pszFormat);
+    if (RT_SUCCESS(RTStrAPrintfV(&buf, pszFormat, va)))
+    {
+        LogRel(("%s: Error: %s", VBOX_MODULE_NAME, buf));
+        pam_vbox_writesyslog(buf);
+        RTStrFree(buf);
+    }
+    va_end(va);
+}
+
+
+/**
+ * Displays a debug message.
+ *
+ * @param   hPAM                    PAM handle.
+ * @param   pszFormat               The message text.
+ * @param   ...                     Format arguments.
+ */
+static void pam_vbox_log(pam_handle_t *hPAM, const char *pszFormat, ...)
+{
+    RT_NOREF1(hPAM);
+    if (g_verbosity)
+    {
+        va_list va;
+        char *buf;
+        va_start(va, pszFormat);
+        if (RT_SUCCESS(RTStrAPrintfV(&buf, pszFormat, va)))
+        {
+            /* Only do normal logging in debug mode; could contain
+             * sensitive data! */
+            LogRel(("%s: %s", VBOX_MODULE_NAME, buf));
+            /* Log to syslog */
+            pam_vbox_writesyslog(buf);
+            RTStrFree(buf);
+        }
+        va_end(va);
+    }
+}
+
+
+/**
+ * Sets a message using PAM's conversation function.
+ *
+ * @return  IPRT status code.
+ * @param   hPAM                    PAM handle.
+ * @param   iStyle                  Style of message (0 = Information, 1 = Prompt
+ *                                  echo off, 2 = Prompt echo on, 3 = Error).
+ * @param   pszText                 Message text to set.
+ */
+static int vbox_set_msg(pam_handle_t *hPAM, int iStyle, const char *pszText)
+{
+    AssertPtrReturn(hPAM, VERR_INVALID_POINTER);
+    AssertPtrReturn(pszText, VERR_INVALID_POINTER);
+
+    if (!iStyle)
+        iStyle = PAM_TEXT_INFO;
+
+    int rc = VINF_SUCCESS;
+
+    pam_message msg;
+    msg.msg_style = iStyle;
+#ifdef RT_OS_SOLARIS
+    msg.msg = (char*)pszText;
+#else
+    msg.msg = pszText;
+#endif
+
+#ifdef RT_OS_SOLARIS
+    pam_conv *conv = NULL;
+    int pamrc = pam_get_item(hPAM, PAM_CONV, (void **)&conv);
+#else
+    const pam_conv *conv = NULL;
+    int pamrc = pam_get_item(hPAM, PAM_CONV, (const void **)&conv);
+#endif
+    if (   pamrc == PAM_SUCCESS
+        && conv)
+    {
+        pam_response *resp = NULL;
+#ifdef RT_OS_SOLARIS
+        pam_message *msg_p = &msg;
+#else
+        const pam_message *msg_p = &msg;
+#endif
+        pam_vbox_log(hPAM, "Showing message \"%s\" (type %d)", pszText, iStyle);
+
+        pamrc = conv->conv(1 /* One message only */, &msg_p, &resp, conv->appdata_ptr);
+        if (resp != NULL) /* If we use PAM_TEXT_INFO we never will get something back! */
+        {
+            if (resp->resp)
+            {
+                pam_vbox_log(hPAM, "Response to message \"%s\" was \"%s\"",
+                             pszText, resp->resp);
+                /** @todo Save response!  */
+                free(resp->resp);
+            }
+            free(resp);
+        }
+    }
+    else
+        rc = VERR_NOT_FOUND;
+    return rc;
+}
+
+
+/**
+ * Initializes pam_vbox.
+ *
+ * @return  IPRT status code.
+ * @param   hPAM                    PAM handle.
+ */
+static int pam_vbox_init(pam_handle_t *hPAM)
+{
+#ifdef DEBUG
+    g_pam_handle = hPAM; /* hack for getting assertion text */
+#endif
+
+    /* Don't make assertions panic because the PAM stack +
+     * the current logon module won't work anymore (or just restart).
+     * This could result in not able to log into the system anymore. */
+    RTAssertSetMayPanic(false);
+
+    pam_vbox_log(hPAM, "pam_vbox: %sr%s, running on %s\n",
+                 RTBldCfgVersion(), RTBldCfgRevisionStr(), RTBldCfgTargetArch());
+
+    int rc = RTR3InitDll(0);
+    if (RT_FAILURE(rc))
+    {
+        pam_vbox_error(hPAM, "pam_vbox_init: could not init runtime! rc=%Rrc. Aborting\n", rc);
+        return PAM_SUCCESS; /* Jump out as early as we can to not mess around. */
+    }
+
+    pam_vbox_log(hPAM, "pam_vbox_init: runtime initialized\n");
+    if (RT_SUCCESS(rc))
+    {
+        rc = VbglR3InitUser();
+        if (RT_FAILURE(rc))
+        {
+            switch(rc)
+            {
+                case VERR_ACCESS_DENIED:
+                    pam_vbox_error(hPAM, "pam_vbox_init: access is denied to guest driver! Please make sure you run with sufficient rights. Aborting\n");
+                    break;
+
+                case VERR_FILE_NOT_FOUND:
+                    pam_vbox_error(hPAM, "pam_vbox_init: guest driver not found! Guest Additions installed? Aborting\n");
+                    break;
+
+                default:
+                    pam_vbox_error(hPAM, "pam_vbox_init: could not init VbglR3 library! rc=%Rrc. Aborting\n", rc);
+                    break;
+            }
+        }
+        pam_vbox_log(hPAM, "pam_vbox_init: guest lib initialized\n");
+    }
+
+    if (RT_SUCCESS(rc))
+    {
+        char *rhost = NULL;
+        char *tty = NULL;
+        char *prompt = NULL;
+#ifdef RT_OS_SOLARIS
+        pam_get_item(hPAM, PAM_RHOST, (void**) &rhost);
+        pam_get_item(hPAM, PAM_TTY, (void**) &tty);
+        pam_get_item(hPAM, PAM_USER_PROMPT, (void**) &prompt);
+#else
+        pam_get_item(hPAM, PAM_RHOST, (const void**) &rhost);
+        pam_get_item(hPAM, PAM_TTY, (const void**) &tty);
+        pam_get_item(hPAM, PAM_USER_PROMPT, (const void**) &prompt);
+#endif
+        pam_vbox_log(hPAM, "pam_vbox_init: rhost=%s, tty=%s, prompt=%s\n",
+                     rhost ? rhost : "<none>", tty ? tty : "<none>", prompt ? prompt : "<none>");
+    }
+
+    return rc;
+}
+
+
+/**
+ * Shuts down pam_vbox.
+ *
+ * @return  IPRT status code.
+ * @param   hPAM                    PAM handle.
+ */
+static void pam_vbox_shutdown(pam_handle_t *hPAM)
+{
+    RT_NOREF1(hPAM);
+    VbglR3Term();
+}
+
+
+/**
+ * Checks for credentials provided by the host / HGCM.
+ *
+ * @return  IPRT status code. VERR_NOT_FOUND if no credentials are available,
+ *          VINF_SUCCESS on successful retrieval or another IPRT error.
+ * @param   hPAM                    PAM handle.
+ */
+static int pam_vbox_check_creds(pam_handle_t *hPAM)
+{
+    int rc = VbglR3CredentialsQueryAvailability();
+    if (RT_FAILURE(rc))
+    {
+        if (rc != VERR_NOT_FOUND)
+            pam_vbox_error(hPAM, "pam_vbox_check_creds: could not query for credentials! rc=%Rrc. Aborting\n", rc);
+#ifdef DEBUG
+        else
+            pam_vbox_log(hPAM, "pam_vbox_check_creds: no credentials available\n");
+#endif
+    }
+    else
+    {
+        char *pszUsername;
+        char *pszPassword;
+        char *pszDomain;
+
+        rc = VbglR3CredentialsRetrieve(&pszUsername, &pszPassword, &pszDomain);
+        if (RT_FAILURE(rc))
+        {
+            pam_vbox_error(hPAM, "pam_vbox_check_creds: could not retrieve credentials! rc=%Rrc. Aborting\n", rc);
+        }
+        else
+        {
+#ifdef DEBUG
+            pam_vbox_log(hPAM, "pam_vbox_check_creds: credentials retrieved: user=%s, password=%s, domain=%s\n",
+                         pszUsername, pszPassword, pszDomain);
+#else
+            /* Don't log passwords in release mode! */
+            pam_vbox_log(hPAM, "pam_vbox_check_creds: credentials retrieved: user=%s, password=XXX, domain=%s\n",
+                         pszUsername, pszDomain);
+#endif
+            /* Fill credentials into PAM. */
+            int pamrc = pam_set_item(hPAM, PAM_USER, pszUsername);
+            if (pamrc != PAM_SUCCESS)
+            {
+                pam_vbox_error(hPAM, "pam_vbox_check_creds: could not set user name! pamrc=%d, msg=%s. Aborting\n",
+                               pamrc, pam_strerror(hPAM, pamrc));
+            }
+            else
+            {
+                pamrc = pam_set_item(hPAM, PAM_AUTHTOK, pszPassword);
+                if (pamrc != PAM_SUCCESS)
+                    pam_vbox_error(hPAM, "pam_vbox_check_creds: could not set password! pamrc=%d, msg=%s. Aborting\n",
+                                   pamrc, pam_strerror(hPAM, pamrc));
+
+            }
+            /** @todo Add handling domains as well. */
+            VbglR3CredentialsDestroy(pszUsername, pszPassword, pszDomain,
+                                     3 /* Three wipe passes */);
+            pam_vbox_log(hPAM, "pam_vbox_check_creds: returned with pamrc=%d, msg=%s\n",
+                         pamrc, pam_strerror(hPAM, pamrc));
+        }
+    }
+
+#ifdef DEBUG
+    pam_vbox_log(hPAM, "pam_vbox_check_creds: returned with rc=%Rrc\n", rc);
+#endif
+    return rc;
+}
+
+
+#ifdef VBOX_WITH_GUEST_PROPS
+/**
+ * Reads a guest property.
+ *
+ * @return  IPRT status code.
+ * @param   hPAM                    PAM handle.
+ * @param   uClientID               Guest property service client ID.
+ * @param   pszKey                  Key (name) of guest property to read.
+ * @param   fReadOnly               Indicates whether this key needs to be
+ *                                  checked if it only can be read (and *not* written)
+ *                                  by the guest.
+ * @param   pszValue                Buffer where to store the key's value.
+ * @param   cbValue                 Size of buffer (in bytes).
+ */
+static int pam_vbox_read_prop(pam_handle_t *hPAM, uint32_t uClientID,
+                              const char *pszKey, bool fReadOnly,
+                              char *pszValue, size_t cbValue)
+{
+    AssertPtrReturn(hPAM, VERR_INVALID_POINTER);
+    AssertReturn(uClientID, VERR_INVALID_PARAMETER);
+    AssertPtrReturn(pszKey, VERR_INVALID_POINTER);
+    AssertPtrReturn(pszValue, VERR_INVALID_POINTER);
+
+    int rc;
+
+    uint64_t u64Timestamp = 0;
+    char *pszValTemp;
+    char *pszFlags = NULL;
+    /* The buffer for storing the data and its initial size.  We leave a bit
+     * of space here in case the maximum values are raised. */
+    void *pvBuf = NULL;
+    uint32_t cbBuf = GUEST_PROP_MAX_VALUE_LEN + GUEST_PROP_MAX_FLAGS_LEN + _1K;
+
+    /* Because there is a race condition between our reading the size of a
+     * property and the guest updating it, we loop a few times here and
+     * hope.  Actually this should never go wrong, as we are generous
+     * enough with buffer space. */
+    for (unsigned i = 0; i < 10; i++)
+    {
+        void *pvTmpBuf = RTMemRealloc(pvBuf, cbBuf);
+        if (pvTmpBuf)
+        {
+            pvBuf = pvTmpBuf;
+            rc = VbglR3GuestPropRead(uClientID, pszKey, pvBuf, cbBuf,
+                                     &pszValTemp, &u64Timestamp, &pszFlags,
+                                     &cbBuf);
+        }
+        else
+            rc = VERR_NO_MEMORY;
+
+        switch (rc)
+        {
+            case VERR_BUFFER_OVERFLOW:
+            {
+                /* Buffer too small, try it with a bigger one next time. */
+                cbBuf += _1K;
+                continue; /* Try next round. */
+            }
+
+            default:
+                break;
+        }
+
+        /* Everything except VERR_BUFFER_OVERLOW makes us bail out ... */
+        break;
+    }
+
+    if (RT_SUCCESS(rc))
+    {
+        /* Check security bits. */
+        if (pszFlags)
+        {
+            if (   fReadOnly
+                && !RTStrStr(pszFlags, "RDONLYGUEST"))
+            {
+                /* If we want a property which is read-only on the guest
+                 * and it is *not* marked as such, deny access! */
+                pam_vbox_error(hPAM, "pam_vbox_read_prop: key \"%s\" should be read-only on guest but it is not\n",
+                               pszKey);
+                rc = VERR_ACCESS_DENIED;
+            }
+        }
+        else /* No flags, no access! */
+        {
+            pam_vbox_error(hPAM, "pam_vbox_read_prop: key \"%s\" contains no/wrong flags (%s)\n",
+                           pszKey, pszFlags);
+            rc = VERR_ACCESS_DENIED;
+        }
+
+        if (RT_SUCCESS(rc))
+        {
+            /* If everything went well copy property value to our destination buffer. */
+            if (!RTStrPrintf(pszValue, cbValue, "%s", pszValTemp))
+            {
+                pam_vbox_error(hPAM, "pam_vbox_read_prop: could not store value of key \"%s\"\n",
+                               pszKey);
+                rc = VERR_INVALID_PARAMETER;
+            }
+
+            if (RT_SUCCESS(rc))
+                pam_vbox_log(hPAM, "pam_vbox_read_prop: read key \"%s\"=\"%s\"\n",
+                             pszKey, pszValue);
+        }
+    }
+
+    pam_vbox_log(hPAM, "pam_vbox_read_prop: read key \"%s\" with rc=%Rrc\n",
+                 pszKey, rc);
+    return rc;
+}
+
+
+/**
+ * Waits for a guest property to be changed.
+ *
+ * @return  IPRT status code.
+ * @param   hPAM                    PAM handle.
+ * @param   uClientID               Guest property service client ID.
+ * @param   pszKey                  Key (name) of guest property to wait for.
+ * @param   uTimeoutMS              Timeout (in ms) to wait for the change. Specify
+ *                                  RT_INDEFINITE_WAIT to wait indefinitly.
+ */
+static int pam_vbox_wait_prop(pam_handle_t *hPAM, uint32_t uClientID,
+                              const char *pszKey, uint32_t uTimeoutMS)
+{
+    AssertPtrReturn(hPAM, VERR_INVALID_POINTER);
+    AssertReturn(uClientID, VERR_INVALID_PARAMETER);
+    AssertPtrReturn(pszKey, VERR_INVALID_POINTER);
+
+    int rc;
+
+    /* The buffer for storing the data and its initial size.  We leave a bit
+     * of space here in case the maximum values are raised. */
+    void *pvBuf = NULL;
+    uint32_t cbBuf = GUEST_PROP_MAX_NAME_LEN + GUEST_PROP_MAX_VALUE_LEN + GUEST_PROP_MAX_FLAGS_LEN + _1K;
+
+    for (int i = 0; i < 10; i++)
+    {
+        void *pvTmpBuf = RTMemRealloc(pvBuf, cbBuf);
+        if (pvTmpBuf)
+        {
+            char *pszName = NULL;
+            char *pszValue = NULL;
+            uint64_t u64TimestampOut = 0;
+            char *pszFlags = NULL;
+
+            pvBuf = pvTmpBuf;
+            rc = VbglR3GuestPropWait(uClientID, pszKey, pvBuf, cbBuf,
+                                     0 /* Last timestamp; just wait for next event */, uTimeoutMS,
+                                     &pszName, &pszValue, &u64TimestampOut,
+                                     &pszFlags, &cbBuf);
+        }
+        else
+            rc = VERR_NO_MEMORY;
+
+        if (rc == VERR_BUFFER_OVERFLOW)
+        {
+            /* Buffer too small, try it with a bigger one next time. */
+            cbBuf += _1K;
+            continue; /* Try next round. */
+        }
+
+        /* Everything except VERR_BUFFER_OVERLOW makes us bail out ... */
+        break;
+    }
+
+    return rc;
+}
+#endif
+
+/**
+ * Thread function waiting for credentials to arrive.
+ *
+ * @return  IPRT status code.
+ * @param   hThreadSelf             Thread handle.
+ * @param   pvUser                  Pointer to a PAMVBOXTHREAD structure providing
+ *                                  required data used / set by the thread.
+ */
+static DECLCALLBACK(int) pam_vbox_wait_thread(RTTHREAD hThreadSelf, void *pvUser)
+{
+    RT_NOREF1(hThreadSelf);
+    PPAMVBOXTHREAD pUserData = (PPAMVBOXTHREAD)pvUser;
+    AssertPtr(pUserData);
+
+    int rc = VINF_SUCCESS;
+    /* Get current time stamp to later calculate rest of timeout left. */
+    uint64_t u64StartMS = RTTimeMilliTS();
+
+#ifdef VBOX_WITH_GUEST_PROPS
+    uint32_t uClientID = 0;
+    rc = VbglR3GuestPropConnect(&uClientID);
+    if (RT_FAILURE(rc))
+    {
+        pam_vbox_error(pUserData->hPAM, "pam_vbox_wait_thread: Unable to connect to guest property service, rc=%Rrc\n", rc);
+    }
+    else
+    {
+        pam_vbox_log(pUserData->hPAM, "pam_vbox_wait_thread: clientID=%u\n", uClientID);
+#endif
+        for (;;)
+        {
+#ifdef VBOX_WITH_GUEST_PROPS
+            if (uClientID)
+            {
+                rc = pam_vbox_wait_prop(pUserData->hPAM, uClientID,
+                                        "/VirtualBox/GuestAdd/PAM/CredsWaitAbort",
+                                        500 /* Wait 500ms, same as VBoxGINA/VBoxCredProv. */);
+                switch (rc)
+                {
+                    case VINF_SUCCESS:
+                        /* Somebody (guest/host) wants to abort waiting for credentials. */
+                        break;
+
+                    case VERR_INTERRUPTED:
+                        pam_vbox_error(pUserData->hPAM, "pam_vbox_wait_thread: The abort notification request timed out or was interrupted\n");
+                        break;
+
+                    case VERR_TIMEOUT:
+                        /* We did not receive an abort message within time. */
+                        break;
+
+                    case VERR_TOO_MUCH_DATA:
+                        pam_vbox_error(pUserData->hPAM, "pam_vbox_wait_thread: Temporarily unable to get abort notification\n");
+                        break;
+
+                    default:
+                        pam_vbox_error(pUserData->hPAM, "pam_vbox_wait_thread: The abort notification request failed with rc=%Rrc\n", rc);
+                        break;
+                }
+
+                if (RT_SUCCESS(rc)) /* Abort waiting. */
+                {
+                    pam_vbox_log(pUserData->hPAM, "pam_vbox_wait_thread: Got notification to abort waiting\n");
+                    rc = VERR_CANCELLED;
+                    break;
+                }
+            }
+#endif
+            if (   RT_SUCCESS(rc)
+                || rc == VERR_TIMEOUT)
+            {
+                rc = pam_vbox_check_creds(pUserData->hPAM);
+                if (RT_SUCCESS(rc))
+                {
+                    /* Credentials retrieved. */
+                    break; /* Thread no longer is required, bail out. */
+                }
+                else if (rc == VERR_NOT_FOUND)
+                {
+                    /* No credentials found, but try next round (if there's
+                     * time left for) ... */
+#ifndef VBOX_WITH_GUEST_PROPS
+                    RTThreadSleep(500); /* Wait 500 ms. */
+#endif
+                }
+                else
+                    break; /* Something bad happend ... */
+            }
+            else
+                break;
+
+            /* Calculate timeout value left after process has been started.  */
+            uint64_t u64Elapsed = RTTimeMilliTS() - u64StartMS;
+            /* Is it time to bail out? */
+            if (pUserData->uTimeoutMS < u64Elapsed)
+            {
+                pam_vbox_log(pUserData->hPAM, "pam_vbox_wait_thread: Waiting thread has reached timeout (%dms), exiting ...\n",
+                             pUserData->uTimeoutMS);
+                rc = VERR_TIMEOUT;
+                break;
+            }
+        }
+#ifdef VBOX_WITH_GUEST_PROPS
+    }
+    VbglR3GuestPropDisconnect(uClientID);
+#endif
+
+    /* Save result. */
+    pUserData->rc = rc; /** @todo Use ASMAtomicXXX? */
+
+    int rc2 = RTThreadUserSignal(RTThreadSelf());
+    AssertRC(rc2);
+
+    pam_vbox_log(pUserData->hPAM, "pam_vbox_wait_thread: Waiting thread returned with rc=%Rrc\n", rc);
+    return rc;
+}
+
+
+/**
+ * Waits for credentials to arrive by creating and waiting for a thread.
+ *
+ * @return  IPRT status code.
+ * @param   hPAM                    PAM handle.
+ * @param   uClientID               Guest property service client ID.
+ * @param   uTimeoutMS              Timeout (in ms) to wait for the change. Specify
+ *                                  RT_INDEFINITE_WAIT to wait indefinitly.
+ */
+static int pam_vbox_wait_for_creds(pam_handle_t *hPAM, uint32_t uClientID, uint32_t uTimeoutMS)
+{
+    RT_NOREF1(uClientID);
+    PAMVBOXTHREAD threadData;
+    threadData.hPAM = hPAM;
+    threadData.uTimeoutMS = uTimeoutMS;
+
+    RTTHREAD threadWait;
+    int rc = RTThreadCreate(&threadWait, pam_vbox_wait_thread,
+                            (void *)&threadData, 0,
+                            RTTHREADTYPE_DEFAULT, 0 /* Flags */, "pam_vbox");
+    if (RT_SUCCESS(rc))
+    {
+        pam_vbox_log(hPAM, "pam_vbox_wait_for_creds: Waiting for credentials (%dms) ...\n", uTimeoutMS);
+        /* Wait for thread to initialize. */
+        /** @todo We can do something else here in the meantime later. */
+        rc = RTThreadUserWait(threadWait, RT_INDEFINITE_WAIT);
+        if (RT_SUCCESS(rc))
+            rc = threadData.rc; /* Get back thread result to take further actions. */
+    }
+    else
+        pam_vbox_error(hPAM, "pam_vbox_wait_for_creds: Creating thread failed with rc=%Rrc\n", rc);
+
+    pam_vbox_log(hPAM, "pam_vbox_wait_for_creds: Waiting for credentials returned with rc=%Rrc\n", rc);
+    return rc;
+}
+
+
+DECLEXPORT(int) pam_sm_authenticate(pam_handle_t *hPAM, int iFlags, int argc, const char **argv)
+{
+    RT_NOREF1(iFlags);
+
+    /* Parse arguments. */
+    for (int i = 0; i < argc; i++)
+    {
+        if (!RTStrICmp(argv[i], "debug"))
+            g_verbosity = 1;
+        else
+            pam_vbox_error(hPAM, "pam_vbox_authenticate: unknown command line argument \"%s\"\n", argv[i]);
+    }
+    pam_vbox_log(hPAM, "pam_vbox_authenticate called\n");
+
+    int rc = pam_vbox_init(hPAM);
+    if (RT_FAILURE(rc))
+        return PAM_SUCCESS; /* Jump out as early as we can to not mess around. */
+
+    bool fFallback = true;
+
+#ifdef VBOX_WITH_GUEST_PROPS
+    uint32_t uClientId;
+    rc = VbglR3GuestPropConnect(&uClientId);
+    if (RT_SUCCESS(rc))
+    {
+        char szVal[256];
+        rc = pam_vbox_read_prop(hPAM, uClientId,
+                                "/VirtualBox/GuestAdd/PAM/CredsWait",
+                                true /* Read-only on guest */,
+                                szVal, sizeof(szVal));
+        if (RT_SUCCESS(rc))
+        {
+            /* All calls which are checked against rc2 are not critical, e.g. it does
+             * not matter if they succeed or not. */
+            uint32_t uTimeoutMS = RT_INDEFINITE_WAIT; /* Wait infinite by default. */
+            int rc2 = pam_vbox_read_prop(hPAM, uClientId,
+                                         "/VirtualBox/GuestAdd/PAM/CredsWaitTimeout",
+                                         true /* Read-only on guest */,
+                                         szVal, sizeof(szVal));
+            if (RT_SUCCESS(rc2))
+            {
+                uTimeoutMS = RTStrToUInt32(szVal);
+                if (!uTimeoutMS)
+                {
+                    pam_vbox_error(hPAM, "pam_vbox_authenticate: invalid waiting timeout value specified, defaulting to infinite timeout\n");
+                    uTimeoutMS = RT_INDEFINITE_WAIT;
+                }
+                else
+                    uTimeoutMS = uTimeoutMS * 1000; /* Make ms out of s. */
+            }
+
+            rc2 = pam_vbox_read_prop(hPAM, uClientId,
+                                     "/VirtualBox/GuestAdd/PAM/CredsMsgWaiting",
+                                     true /* Read-only on guest */,
+                                     szVal, sizeof(szVal));
+            const char *pszWaitMsg = NULL;
+            if (RT_SUCCESS(rc2))
+                pszWaitMsg = szVal;
+
+            rc2 = vbox_set_msg(hPAM, 0 /* Info message */,
+                               pszWaitMsg ? pszWaitMsg : "Waiting for credentials ...");
+            if (RT_FAILURE(rc2)) /* Not critical. */
+                pam_vbox_error(hPAM, "pam_vbox_authenticate: error setting waiting information message, rc=%Rrc\n", rc2);
+
+            if (RT_SUCCESS(rc))
+            {
+                /* Before we actuall wait for credentials just make sure we didn't already get credentials
+                 * set so that we can skip waiting for them ... */
+                rc = pam_vbox_check_creds(hPAM);
+                if (rc == VERR_NOT_FOUND)
+                {
+                    rc = pam_vbox_wait_for_creds(hPAM, uClientId, uTimeoutMS);
+                    if (rc == VERR_TIMEOUT)
+                    {
+                        pam_vbox_log(hPAM, "pam_vbox_authenticate: no credentials given within time\n");
+
+                        rc2 = pam_vbox_read_prop(hPAM, uClientId,
+                                                 "/VirtualBox/GuestAdd/PAM/CredsMsgWaitTimeout",
+                                                 true /* Read-only on guest */,
+                                                 szVal, sizeof(szVal));
+                        if (RT_SUCCESS(rc2))
+                        {
+                            rc2 = vbox_set_msg(hPAM, 0 /* Info message */, szVal);
+                            AssertRC(rc2);
+                        }
+                    }
+                    else if (rc == VERR_CANCELLED)
+                    {
+                        pam_vbox_log(hPAM, "pam_vbox_authenticate: waiting aborted\n");
+
+                        rc2 = pam_vbox_read_prop(hPAM, uClientId,
+                                                 "/VirtualBox/GuestAdd/PAM/CredsMsgWaitAbort",
+                                                 true /* Read-only on guest */,
+                                                 szVal, sizeof(szVal));
+                        if (RT_SUCCESS(rc2))
+                        {
+                            rc2 = vbox_set_msg(hPAM, 0 /* Info message */, szVal);
+                            AssertRC(rc2);
+                        }
+                    }
+                }
+
+                /* If we got here we don't need the fallback, so just deactivate it. */
+                fFallback = false;
+            }
+        }
+
+        VbglR3GuestPropDisconnect(uClientId);
+    }
+#endif /* VBOX_WITH_GUEST_PROPS */
+
+    if (fFallback)
+    {
+        pam_vbox_log(hPAM, "pam_vbox_authenticate: falling back to old method\n");
+
+        /* If anything went wrong in the code above we just do a credentials
+         * check like it was before: Try retrieving the stuff and authenticating. */
+        int rc2 = pam_vbox_check_creds(hPAM);
+        if (RT_SUCCESS(rc))
+            rc = rc2;
+    }
+
+    pam_vbox_shutdown(hPAM);
+
+    pam_vbox_log(hPAM, "pam_vbox_authenticate: overall result rc=%Rrc\n", rc);
+
+    /* Never report an error here because if no credentials from the host are available or something
+     * went wrong we then let do the authentication by the next module in the stack. */
+
+    /* We report success here because this is all we can do right now -- we passed the credentials
+     * to the next PAM module in the block above which then might do a shadow (like pam_unix/pam_unix2)
+     * password verification to "really" authenticate the user. */
+    return PAM_SUCCESS;
+}
+
+
+DECLEXPORT(int) pam_sm_setcred(pam_handle_t *hPAM, int iFlags, int argc, const char **argv)
+{
+    pam_vbox_log(hPAM, "pam_vbox_setcred called, iFlags=0x%x\n", iFlags);
+    for (int i = 0; i < argc; i++)
+        pam_vbox_log(hPAM, "pam_vbox_setcred: argv[%d] = %s\n", i, argv[i]);
+    return PAM_SUCCESS;
+}
+
+
+DECLEXPORT(int) pam_sm_acct_mgmt(pam_handle_t *hPAM, int iFlags, int argc, const char **argv)
+{
+    RT_NOREF3(iFlags, argc, argv);
+    pam_vbox_log(hPAM, "pam_vbox_acct_mgmt called\n");
+    return PAM_SUCCESS;
+}
+
+
+DECLEXPORT(int) pam_sm_open_session(pam_handle_t *hPAM, int iFlags, int argc, const char **argv)
+{
+    RT_NOREF3(iFlags, argc, argv);
+    pam_vbox_log(hPAM, "pam_vbox_open_session called\n");
+    RTPrintf("This session was provided by VirtualBox Guest Additions. Have a lot of fun!\n");
+    return PAM_SUCCESS;
+}
+
+
+DECLEXPORT(int) pam_sm_close_session(pam_handle_t *hPAM, int iFlags, int argc, const char **argv)
+{
+    RT_NOREF3(iFlags, argc, argv);
+    pam_vbox_log(hPAM, "pam_vbox_close_session called\n");
+    return PAM_SUCCESS;
+}
+
+
+DECLEXPORT(int) pam_sm_chauthtok(pam_handle_t *hPAM, int iFlags, int argc, const char **argv)
+{
+    RT_NOREF3(iFlags, argc, argv);
+    pam_vbox_log(hPAM, "pam_vbox_sm_chauthtok called\n");
+    return PAM_SUCCESS;
+}
+
+
+#ifdef DEBUG
+DECLEXPORT(void) RTAssertMsg1Weak(const char *pszExpr, unsigned uLine, const char *pszFile, const char *pszFunction)
+{
+    pam_vbox_log(g_pam_handle,
+                 "\n!!Assertion Failed!!\n"
+                 "Expression: %s\n"
+                 "Location  : %s(%d) %s\n",
+                 pszExpr, pszFile, uLine, pszFunction);
+    RTAssertMsg1(pszExpr, uLine, pszFile, pszFunction);
+}
+#endif
+