/* Cache handling for passwd lookup.

   Copyright (C) 1998-2018 Free Software Foundation, Inc.

   This file is part of the GNU C Library.

   Contributed by Ulrich Drepper <drepper@cygnus.com>, 1998.

   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, or

   (at your option) any later version.

   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, see <http://www.gnu.org/licenses/>.  */

#include <assert.h>

#include <errno.h>

#include <error.h>

#include <libintl.h>

#include <pwd.h>

#include <stdbool.h>

#include <stddef.h>

#include <stdio.h>

#include <stdlib.h>

#include <string.h>

#include <time.h>

#include <unistd.h>

#include <sys/mman.h>

#include <sys/socket.h>

#include <stackinfo.h>

#include <scratch_buffer.h>

#include "nscd.h"

#include "dbg_log.h"

/* This is the standard reply in case the service is disabled.  */

static const pw_response_header disabled =

{

  .version = NSCD_VERSION,

  .found = -1,

  .pw_name_len = 0,

  .pw_passwd_len = 0,

  .pw_uid = -1,

  .pw_gid = -1,

  .pw_gecos_len = 0,

  .pw_dir_len = 0,

  .pw_shell_len = 0

};

/* This is the struct describing how to write this record.  */

const struct iovec pwd_iov_disabled =

{

  .iov_base = (void *) &disabled,

  .iov_len = sizeof (disabled)

};

/* This is the standard reply in case we haven't found the dataset.  */

static const pw_response_header notfound =

{

  .version = NSCD_VERSION,

  .found = 0,

  .pw_name_len = 0,

  .pw_passwd_len = 0,

  .pw_uid = -1,

  .pw_gid = -1,

  .pw_gecos_len = 0,

  .pw_dir_len = 0,

  .pw_shell_len = 0

};

static time_t

cache_addpw (struct database_dyn *db, int fd, request_header *req,

	     const void *key, struct passwd *pwd, uid_t owner,

	     struct hashentry *const he, struct datahead *dh, int errval)

{

  bool all_written = true;

  ssize_t total;

  time_t t = time (NULL);

  /* We allocate all data in one memory block: the iov vector,

     the response header and the dataset itself.  */

  struct dataset

  {

    struct datahead head;

    pw_response_header resp;

    char strdata[0];

  } *dataset;

  assert (offsetof (struct dataset, resp) == offsetof (struct datahead, data));

  time_t timeout = MAX_TIMEOUT_VALUE;

  if (pwd == NULL)

    {

      if (he != NULL && errval == EAGAIN)

	{

	  /* If we have an old record available but cannot find one

	     now because the service is not available we keep the old

	     record and make sure it does not get removed.  */

	  if (reload_count != UINT_MAX && dh->nreloads == reload_count)

	    /* Do not reset the value if we never not reload the record.  */

	    dh->nreloads = reload_count - 1;

	  /* Reload with the same time-to-live value.  */

	  timeout = dh->timeout = t + db->postimeout;

	  total = 0;

	}

      else

	{

	  /* We have no data.  This means we send the standard reply for this

	     case.  */

	  total = sizeof (notfound);

	  if (fd != -1

	      && TEMP_FAILURE_RETRY (send (fd, &notfound, total,

					   MSG_NOSIGNAL)) != total)

	    all_written = false;

	  /* If we have a transient error or cannot permanently store

	     the result, so be it.  */

	  if (errno == EAGAIN || __builtin_expect (db->negtimeout == 0, 0))

	    {

	      /* Mark the old entry as obsolete.  */

	      if (dh != NULL)

		dh->usable = false;

	    }

	  else if ((dataset = mempool_alloc (db, (sizeof (struct dataset)

						  + req->key_len), 1)) != NULL)

	    {

	      timeout = datahead_init_neg (&dataset->head,

					   (sizeof (struct dataset)

					    + req->key_len), total,

					   db->negtimeout);

	      /* This is the reply.  */

	      memcpy (&dataset->resp, &notfound, total);

	      /* Copy the key data.  */

	      char *key_copy = memcpy (dataset->strdata, key, req->key_len);

	      /* If necessary, we also propagate the data to disk.  */

	      if (db->persistent)

		{

		  // XXX async OK?

		  uintptr_t pval = (uintptr_t) dataset & ~pagesize_m1;

		  msync ((void *) pval,

			 ((uintptr_t) dataset & pagesize_m1)

			 + sizeof (struct dataset) + req->key_len, MS_ASYNC);

		}

	      (void) cache_add (req->type, key_copy, req->key_len,

				&dataset->head, true, db, owner, he == NULL);

	      pthread_rwlock_unlock (&db->lock);

	      /* Mark the old entry as obsolete.  */

	      if (dh != NULL)

		dh->usable = false;

	    }

	}

    }

  else

    {

      /* Determine the I/O structure.  */

      size_t pw_name_len = strlen (pwd->pw_name) + 1;

      size_t pw_passwd_len = strlen (pwd->pw_passwd) + 1;

      size_t pw_gecos_len = strlen (pwd->pw_gecos) + 1;

      size_t pw_dir_len = strlen (pwd->pw_dir) + 1;

      size_t pw_shell_len = strlen (pwd->pw_shell) + 1;

      char *cp;

      const size_t key_len = strlen (key);

      const size_t buf_len = 3 * sizeof (pwd->pw_uid) + key_len + 1;

      char *buf = alloca (buf_len);

      ssize_t n;

      /* We need this to insert the `byuid' entry.  */

      int key_offset;

      n = snprintf (buf, buf_len, "%d%c%n%s", pwd->pw_uid, '\0',

		    &key_offset, (char *) key) + 1;

      total = (offsetof (struct dataset, strdata)

	       + pw_name_len + pw_passwd_len

	       + pw_gecos_len + pw_dir_len + pw_shell_len);

      /* If we refill the cache, first assume the reconrd did not

	 change.  Allocate memory on the cache since it is likely

	 discarded anyway.  If it turns out to be necessary to have a

	 new record we can still allocate real memory.  */

      bool alloca_used = false;

      dataset = NULL;

      if (he == NULL)

	{

	  /* Prevent an INVALIDATE request from pruning the data between

	     the two calls to cache_add.  */

	  if (db->propagate)

	    pthread_mutex_lock (&db->prune_run_lock);

	  dataset = (struct dataset *) mempool_alloc (db, total + n, 1);

	}

      if (dataset == NULL)

	{

	  if (he == NULL && db->propagate)

	    pthread_mutex_unlock (&db->prune_run_lock);

	  /* We cannot permanently add the result in the moment.  But

	     we can provide the result as is.  Store the data in some

	     temporary memory.  */

	  dataset = (struct dataset *) alloca (total + n);

	  /* We cannot add this record to the permanent database.  */

	  alloca_used = true;

	}

      timeout = datahead_init_pos (&dataset->head, total + n,

				   total - offsetof (struct dataset, resp),

				   he == NULL ? 0 : dh->nreloads + 1,

				   db->postimeout);

      dataset->resp.version = NSCD_VERSION;

      dataset->resp.found = 1;

      dataset->resp.pw_name_len = pw_name_len;

      dataset->resp.pw_passwd_len = pw_passwd_len;

      dataset->resp.pw_uid = pwd->pw_uid;

      dataset->resp.pw_gid = pwd->pw_gid;

      dataset->resp.pw_gecos_len = pw_gecos_len;

      dataset->resp.pw_dir_len = pw_dir_len;

      dataset->resp.pw_shell_len = pw_shell_len;

      cp = dataset->strdata;

      /* Copy the strings over into the buffer.  */

      cp = mempcpy (cp, pwd->pw_name, pw_name_len);

      cp = mempcpy (cp, pwd->pw_passwd, pw_passwd_len);

      cp = mempcpy (cp, pwd->pw_gecos, pw_gecos_len);

      cp = mempcpy (cp, pwd->pw_dir, pw_dir_len);

      cp = mempcpy (cp, pwd->pw_shell, pw_shell_len);

      /* Finally the stringified UID value.  */

      memcpy (cp, buf, n);

      char *key_copy = cp + key_offset;

      assert (key_copy == (char *) rawmemchr (cp, '\0') + 1);

      assert (cp == dataset->strdata + total - offsetof (struct dataset,

							 strdata));

      /* Now we can determine whether on refill we have to create a new

	 record or not.  */

      if (he != NULL)

	{

	  assert (fd == -1);

	  if (dataset->head.allocsize == dh->allocsize

	      && dataset->head.recsize == dh->recsize

	      && memcmp (&dataset->resp, dh->data,

			 dh->allocsize - offsetof (struct dataset, resp)) == 0)

	    {

	      /* The data has not changed.  We will just bump the

		 timeout value.  Note that the new record has been

		 allocated on the stack and need not be freed.  */

	      dh->timeout = dataset->head.timeout;

	      ++dh->nreloads;

	    }

	  else

	    {

	      /* We have to create a new record.  Just allocate

		 appropriate memory and copy it.  */

	      struct dataset *newp

		= (struct dataset *) mempool_alloc (db, total + n, 1);

	      if (newp != NULL)

		{

		  /* Adjust pointer into the memory block.  */

		  cp = (char *) newp + (cp - (char *) dataset);

		  key_copy = (char *) newp + (key_copy - (char *) dataset);

		  dataset = memcpy (newp, dataset, total + n);

		  alloca_used = false;

		}

	      /* Mark the old record as obsolete.  */

	      dh->usable = false;

	    }

	}

      else

	{

	  /* We write the dataset before inserting it to the database

	     since while inserting this thread might block and so would

	     unnecessarily let the receiver wait.  */

	  assert (fd != -1);

	  if (writeall (fd, &dataset->resp, dataset->head.recsize)

	      != dataset->head.recsize)

	    all_written = false;

	}

      /* Add the record to the database.  But only if it has not been

	 stored on the stack.  */

      if (! alloca_used)

	{

	  /* If necessary, we also propagate the data to disk.  */

	  if (db->persistent)

	    {

	      // XXX async OK?

	      uintptr_t pval = (uintptr_t) dataset & ~pagesize_m1;

	      msync ((void *) pval,

		     ((uintptr_t) dataset & pagesize_m1) + total + n,

		     MS_ASYNC);

	    }

	  /* NB: in the following code we always must add the entry

	     marked with FIRST first.  Otherwise we end up with

	     dangling "pointers" in case a latter hash entry cannot be

	     added.  */

	  bool first = true;

	  /* If the request was by UID, add that entry first.  */

	  if (req->type == GETPWBYUID)

	    {

	      if (cache_add (GETPWBYUID, cp, key_offset, &dataset->head, true,

			     db, owner, he == NULL) < 0)

		goto out;

	      first = false;

	    }

	  /* If the key is different from the name add a separate entry.  */

	  else if (strcmp (key_copy, dataset->strdata) != 0)

	    {

	      if (cache_add (GETPWBYNAME, key_copy, key_len + 1,

			     &dataset->head, true, db, owner, he == NULL) < 0)

		goto out;

	      first = false;

	    }

	  /* We have to add the value for both, byname and byuid.  */

	  if ((req->type == GETPWBYNAME || db->propagate)

	      && __builtin_expect (cache_add (GETPWBYNAME, dataset->strdata,

					      pw_name_len, &dataset->head,

					      first, db, owner, he == NULL)

				   == 0, 1))

	    {

	      if (req->type == GETPWBYNAME && db->propagate)

		(void) cache_add (GETPWBYUID, cp, key_offset, &dataset->head,

				  false, db, owner, false);

	    }

	out:

	  pthread_rwlock_unlock (&db->lock);

	  if (he == NULL && db->propagate)

	    pthread_mutex_unlock (&db->prune_run_lock);

	}

    }

  if (__builtin_expect (!all_written, 0) && debug_level > 0)

    {

      char buf[256];

      dbg_log (_("short write in %s: %s"),  __FUNCTION__,

	       strerror_r (errno, buf, sizeof (buf)));

    }

  return timeout;

}

union keytype

{

  void *v;

  uid_t u;

};

static int

lookup (int type, union keytype key, struct passwd *resultbufp, char *buffer,

	size_t buflen, struct passwd **pwd)

{

  if (type == GETPWBYNAME)

    return __getpwnam_r (key.v, resultbufp, buffer, buflen, pwd);

  else

    return __getpwuid_r (key.u, resultbufp, buffer, buflen, pwd);

}

static time_t

addpwbyX (struct database_dyn *db, int fd, request_header *req,

	  union keytype key, const char *keystr, uid_t c_uid,

	  struct hashentry *he, struct datahead *dh)

{

  /* Search for the entry matching the key.  Please note that we don't

     look again in the table whether the dataset is now available.  We

     simply insert it.  It does not matter if it is in there twice.  The

     pruning function only will look at the timestamp.  */

  struct passwd resultbuf;

  struct passwd *pwd;

  int errval = 0;

  struct scratch_buffer tmpbuf;

  scratch_buffer_init (&tmpbuf);

  if (__glibc_unlikely (debug_level > 0))

    {

      if (he == NULL)

	dbg_log (_("Haven't found \"%s\" in user database cache!"), keystr);

      else

	dbg_log (_("Reloading \"%s\" in user database cache!"), keystr);

    }

  while (lookup (req->type, key, &resultbuf,

		 tmpbuf.data, tmpbuf.length, &pwd) != 0

	 && (errval = errno) == ERANGE)

    if (!scratch_buffer_grow (&tmpbuf))

      {

	/* We ran out of memory.  We cannot do anything but sending a

	   negative response.  In reality this should never

	   happen.  */

	pwd = NULL;

	/* We set the error to indicate this is (possibly) a temporary

	   error and that it does not mean the entry is not available

	   at all.  */

	errval = EAGAIN;

	break;

      }

  /* Add the entry to the cache.  */

  time_t timeout = cache_addpw (db, fd, req, keystr, pwd, c_uid, he, dh,

				errval);

  scratch_buffer_free (&tmpbuf);

  return timeout;

}

void

addpwbyname (struct database_dyn *db, int fd, request_header *req,

	     void *key, uid_t c_uid)

{

  union keytype u = { .v = key };

  addpwbyX (db, fd, req, u, key, c_uid, NULL, NULL);

}

time_t

readdpwbyname (struct database_dyn *db, struct hashentry *he,

	       struct datahead *dh)

{

  request_header req =

    {

      .type = GETPWBYNAME,

      .key_len = he->len

    };

  union keytype u = { .v = db->data + he->key };

  return addpwbyX (db, -1, &req, u, db->data + he->key, he->owner, he, dh);

}

void

addpwbyuid (struct database_dyn *db, int fd, request_header *req,

	    void *key, uid_t c_uid)

{

  char *ep;

  uid_t uid = strtoul ((char *) key, &ep, 10);

  if (*(char *) key == '\0' || *ep != '\0')  /* invalid numeric uid */

    {

      if (debug_level > 0)

	dbg_log (_("Invalid numeric uid \"%s\"!"), (char *) key);

      errno = EINVAL;

      return;

    }

  union keytype u = { .u = uid };

  addpwbyX (db, fd, req, u, key, c_uid, NULL, NULL);

}

time_t

readdpwbyuid (struct database_dyn *db, struct hashentry *he,

	      struct datahead *dh)

{

  char *ep;

  uid_t uid = strtoul (db->data + he->key, &ep, 10);

  /* Since the key has been added before it must be OK.  */

  assert (*(db->data + he->key) != '\0' && *ep == '\0');

  request_header req =

    {

      .type = GETPWBYUID,

      .key_len = he->len

    };

  union keytype u = { .u = uid };

  return addpwbyX (db, -1, &req, u, db->data + he->key, he->owner, he, dh);

}