src/common/exec.c

   1 /*-------------------------------------------------------------------------
   2  *
   3  * exec.c
   4  *              Functions for finding and validating executable files
   5  *
   6  *
   7  * Portions Copyright (c) 1996-2024, PostgreSQL Global Development Group
   8  * Portions Copyright (c) 1994, Regents of the University of California
   9  *
  10  *
  11  * IDENTIFICATION
  12  *        src/common/exec.c
  13  *
  14  *-------------------------------------------------------------------------
  15  */
  16
  17 /*
  18  * On macOS, "man realpath" avers:
  19  *    Defining _DARWIN_C_SOURCE or _DARWIN_BETTER_REALPATH before including
  20  *    stdlib.h will cause the provided implementation of realpath() to use
  21  *    F_GETPATH from fcntl(2) to discover the path.
  22  * This should be harmless everywhere else.
  23  */
  24 #define _DARWIN_BETTER_REALPATH
  25
  26 #ifndef FRONTEND
  27 #include "postgres.h"
  28 #else
  29 #include "postgres_fe.h"
  30 #endif
  31
  32 #include <signal.h>
  33 #include <sys/stat.h>
  34 #include <sys/wait.h>
  35 #include <unistd.h>
  36
  37 #ifdef EXEC_BACKEND
  38 #if defined(HAVE_SYS_PERSONALITY_H)
  39 #include <sys/personality.h>
  40 #elif defined(HAVE_SYS_PROCCTL_H)
  41 #include <sys/procctl.h>
  42 #endif
  43 #endif
  44
  45 #include "common/string.h"
  46
  47 /* Inhibit mingw CRT's auto-globbing of command line arguments */
  48 #if defined(WIN32) && !defined(_MSC_VER)
  49 extern int      _CRT_glob = 0;          /* 0 turns off globbing; 1 turns it on */
  50 #endif
  51
  52 /*
  53  * Hacky solution to allow expressing both frontend and backend error reports
  54  * in one macro call.  First argument of log_error is an errcode() call of
  55  * some sort (ignored if FRONTEND); the rest are errmsg_internal() arguments,
  56  * i.e. message string and any parameters for it.
  57  *
  58  * Caller must provide the gettext wrapper around the message string, if
  59  * appropriate, so that it gets translated in the FRONTEND case; this
  60  * motivates using errmsg_internal() not errmsg().  We handle appending a
  61  * newline, if needed, inside the macro, so that there's only one translatable
  62  * string per call not two.
  63  */
  64 #ifndef FRONTEND
  65 #define log_error(errcodefn, ...) \
  66         ereport(LOG, (errcodefn, errmsg_internal(__VA_ARGS__)))
  67 #else
  68 #define log_error(errcodefn, ...) \
  69         (fprintf(stderr, __VA_ARGS__), fputc('\n', stderr))
  70 #endif
  71
  72 static int      normalize_exec_path(char *path);
  73 static char *pg_realpath(const char *fname);
  74
  75 #ifdef WIN32
  76 static BOOL GetTokenUser(HANDLE hToken, PTOKEN_USER *ppTokenUser);
  77 #endif
  78
  79 /*
  80  * validate_exec -- validate "path" as an executable file
  81  *
  82  * returns 0 if the file is found and no error is encountered.
  83  *                -1 if the regular file "path" does not exist or cannot be executed.
  84  *                -2 if the file is otherwise valid but cannot be read.
  85  * in the failure cases, errno is set appropriately
  86  */
  87 int
  88 validate_exec(const char *path)
  89 {
  90         struct stat buf;
  91         int                     is_r;
  92         int                     is_x;
  93
  94 #ifdef WIN32
  95         char            path_exe[MAXPGPATH + sizeof(".exe") - 1];
  96
  97         /* Win32 requires a .exe suffix for stat() */
  98         if (strlen(path) < strlen(".exe") ||
  99                 pg_strcasecmp(path + strlen(path) - strlen(".exe"), ".exe") != 0)
 100         {
 101                 strlcpy(path_exe, path, sizeof(path_exe) - 4);
 102                 strcat(path_exe, ".exe");
 103                 path = path_exe;
 104         }
 105 #endif
 106
 107         /*
 108          * Ensure that the file exists and is a regular file.
 109          *
 110          * XXX if you have a broken system where stat() looks at the symlink
 111          * instead of the underlying file, you lose.
 112          */
 113         if (stat(path, &buf) < 0)
 114                 return -1;
 115
 116         if (!S_ISREG(buf.st_mode))
 117         {
 118                 /*
 119                  * POSIX offers no errno code that's simply "not a regular file".  If
 120                  * it's a directory we can use EISDIR.  Otherwise, it's most likely a
 121                  * device special file, and EPERM (Operation not permitted) isn't too
 122                  * horribly off base.
 123                  */
 124                 errno = S_ISDIR(buf.st_mode) ? EISDIR : EPERM;
 125                 return -1;
 126         }
 127
 128         /*
 129          * Ensure that the file is both executable and readable (required for
 130          * dynamic loading).
 131          */
 132 #ifndef WIN32
 133         is_r = (access(path, R_OK) == 0);
 134         is_x = (access(path, X_OK) == 0);
 135         /* access() will set errno if it returns -1 */
 136 #else
 137         is_r = buf.st_mode & S_IRUSR;
 138         is_x = buf.st_mode & S_IXUSR;
 139         errno = EACCES;                         /* appropriate thing if we return nonzero */
 140 #endif
 141         return is_x ? (is_r ? 0 : -2) : -1;
 142 }
 143
 144
 145 /*
 146  * find_my_exec -- find an absolute path to this program's executable
 147  *
 148  *      argv0 is the name passed on the command line
 149  *      retpath is the output area (must be of size MAXPGPATH)
 150  *      Returns 0 if OK, -1 if error.
 151  *
 152  * The reason we have to work so hard to find an absolute path is that
 153  * on some platforms we can't do dynamic loading unless we know the
 154  * executable's location.  Also, we need an absolute path not a relative
 155  * path because we may later change working directory.  Finally, we want
 156  * a true path not a symlink location, so that we can locate other files
 157  * that are part of our installation relative to the executable.
 158  */
 159 int
 160 find_my_exec(const char *argv0, char *retpath)
 161 {
 162         char       *path;
 163
 164         /*
 165          * If argv0 contains a separator, then PATH wasn't used.
 166          */
 167         strlcpy(retpath, argv0, MAXPGPATH);
 168         if (first_dir_separator(retpath) != NULL)
 169         {
 170                 if (validate_exec(retpath) == 0)
 171                         return normalize_exec_path(retpath);
 172
 173                 log_error(errcode(ERRCODE_WRONG_OBJECT_TYPE),
 174                                   _("invalid binary \"%s\": %m"), retpath);
 175                 return -1;
 176         }
 177
 178 #ifdef WIN32
 179         /* Win32 checks the current directory first for names without slashes */
 180         if (validate_exec(retpath) == 0)
 181                 return normalize_exec_path(retpath);
 182 #endif
 183
 184         /*
 185          * Since no explicit path was supplied, the user must have been relying on
 186          * PATH.  We'll search the same PATH.
 187          */
 188         if ((path = getenv("PATH")) && *path)
 189         {
 190                 char       *startp = NULL,
 191                                    *endp = NULL;
 192
 193                 do
 194                 {
 195                         if (!startp)
 196                                 startp = path;
 197                         else
 198                                 startp = endp + 1;
 199
 200                         endp = first_path_var_separator(startp);
 201                         if (!endp)
 202                                 endp = startp + strlen(startp); /* point to end */
 203
 204                         strlcpy(retpath, startp, Min(endp - startp + 1, MAXPGPATH));
 205
 206                         join_path_components(retpath, retpath, argv0);
 207                         canonicalize_path(retpath);
 208
 209                         switch (validate_exec(retpath))
 210                         {
 211                                 case 0:                 /* found ok */
 212                                         return normalize_exec_path(retpath);
 213                                 case -1:                /* wasn't even a candidate, keep looking */
 214                                         break;
 215                                 case -2:                /* found but disqualified */
 216                                         log_error(errcode(ERRCODE_WRONG_OBJECT_TYPE),
 217                                                           _("could not read binary \"%s\": %m"),
 218                                                           retpath);
 219                                         break;
 220                         }
 221                 } while (*endp);
 222         }
 223
 224         log_error(errcode(ERRCODE_UNDEFINED_FILE),
 225                           _("could not find a \"%s\" to execute"), argv0);
 226         return -1;
 227 }
 228
 229
 230 /*
 231  * normalize_exec_path - resolve symlinks and convert to absolute path
 232  *
 233  * Given a path that refers to an executable, chase through any symlinks
 234  * to find the real file location; then convert that to an absolute path.
 235  *
 236  * On success, replaces the contents of "path" with the absolute path.
 237  * ("path" is assumed to be of size MAXPGPATH.)
 238  * Returns 0 if OK, -1 if error.
 239  */
 240 static int
 241 normalize_exec_path(char *path)
 242 {
 243         /*
 244          * We used to do a lot of work ourselves here, but now we just let
 245          * realpath(3) do all the heavy lifting.
 246          */
 247         char       *abspath = pg_realpath(path);
 248
 249         if (abspath == NULL)
 250         {
 251                 log_error(errcode_for_file_access(),
 252                                   _("could not resolve path \"%s\" to absolute form: %m"),
 253                                   path);
 254                 return -1;
 255         }
 256         strlcpy(path, abspath, MAXPGPATH);
 257         free(abspath);
 258
 259 #ifdef WIN32
 260         /* On Windows, be sure to convert '\' to '/' */
 261         canonicalize_path(path);
 262 #endif
 263
 264         return 0;
 265 }
 266
 267
 268 /*
 269  * pg_realpath() - realpath(3) with POSIX.1-2008 semantics
 270  *
 271  * This is equivalent to realpath(fname, NULL), in that it returns a
 272  * malloc'd buffer containing the absolute path equivalent to fname.
 273  * On error, returns NULL with errno set.
 274  *
 275  * On Windows, what you get is spelled per platform conventions,
 276  * so you probably want to apply canonicalize_path() to the result.
 277  *
 278  * For now, this is needed only here so mark it static.  If you choose to
 279  * move it into its own file, move the _DARWIN_BETTER_REALPATH #define too!
 280  */
 281 static char *
 282 pg_realpath(const char *fname)
 283 {
 284         char       *path;
 285
 286 #ifndef WIN32
 287         path = realpath(fname, NULL);
 288 #else                                                   /* WIN32 */
 289
 290         /*
 291          * Microsoft is resolutely non-POSIX, but _fullpath() does the same thing.
 292          * The documentation claims it reports errors by setting errno, which is a
 293          * bit surprising for Microsoft, but we'll believe that until it's proven
 294          * wrong.  Clear errno first, though, so we can at least tell if a failure
 295          * occurs and doesn't set it.
 296          */
 297         errno = 0;
 298         path = _fullpath(NULL, fname, 0);
 299 #endif
 300
 301         return path;
 302 }
 303
 304
 305 /*
 306  * Find another program in our binary's directory,
 307  * then make sure it is the proper version.
 308  */
 309 int
 310 find_other_exec(const char *argv0, const char *target,
 311                                 const char *versionstr, char *retpath)
 312 {
 313         char            cmd[MAXPGPATH];
 314         char       *line;
 315
 316         if (find_my_exec(argv0, retpath) < 0)
 317                 return -1;
 318
 319         /* Trim off program name and keep just directory */
 320         *last_dir_separator(retpath) = '\0';
 321         canonicalize_path(retpath);
 322
 323         /* Now append the other program's name */
 324         snprintf(retpath + strlen(retpath), MAXPGPATH - strlen(retpath),
 325                          "/%s%s", target, EXE);
 326
 327         if (validate_exec(retpath) != 0)
 328                 return -1;
 329
 330         snprintf(cmd, sizeof(cmd), "\"%s\" -V", retpath);
 331
 332         if ((line = pipe_read_line(cmd)) == NULL)
 333                 return -1;
 334
 335         if (strcmp(line, versionstr) != 0)
 336         {
 337                 pfree(line);
 338                 return -2;
 339         }
 340
 341         pfree(line);
 342         return 0;
 343 }
 344
 345
 346 /*
 347  * Execute a command in a pipe and read the first line from it. The returned
 348  * string is palloc'd (malloc'd in frontend code), the caller is responsible
 349  * for freeing.
 350  */
 351 char *
 352 pipe_read_line(char *cmd)
 353 {
 354         FILE       *pipe_cmd;
 355         char       *line;
 356
 357         fflush(NULL);
 358
 359         errno = 0;
 360         if ((pipe_cmd = popen(cmd, "r")) == NULL)
 361         {
 362                 log_error(errcode(ERRCODE_SYSTEM_ERROR),
 363                                   _("could not execute command \"%s\": %m"), cmd);
 364                 return NULL;
 365         }
 366
 367         /* Make sure popen() didn't change errno */
 368         errno = 0;
 369         line = pg_get_line(pipe_cmd, NULL);
 370
 371         if (line == NULL)
 372         {
 373                 if (ferror(pipe_cmd))
 374                         log_error(errcode_for_file_access(),
 375                                           _("could not read from command \"%s\": %m"), cmd);
 376                 else
 377                         log_error(errcode(ERRCODE_NO_DATA),
 378                                           _("no data was returned by command \"%s\""), cmd);
 379         }
 380
 381         (void) pclose_check(pipe_cmd);
 382
 383         return line;
 384 }
 385
 386
 387 /*
 388  * pclose() plus useful error reporting
 389  */
 390 int
 391 pclose_check(FILE *stream)
 392 {
 393         int                     exitstatus;
 394         char       *reason;
 395
 396         exitstatus = pclose(stream);
 397
 398         if (exitstatus == 0)
 399                 return 0;                               /* all is well */
 400
 401         if (exitstatus == -1)
 402         {
 403                 /* pclose() itself failed, and hopefully set errno */
 404                 log_error(errcode(ERRCODE_SYSTEM_ERROR),
 405                                   _("%s() failed: %m"), "pclose");
 406         }
 407         else
 408         {
 409                 reason = wait_result_to_str(exitstatus);
 410                 log_error(errcode(ERRCODE_SYSTEM_ERROR),
 411                                   "%s", reason);
 412                 pfree(reason);
 413         }
 414         return exitstatus;
 415 }
 416
 417 /*
 418  *      set_pglocale_pgservice
 419  *
 420  *      Set application-specific locale and service directory
 421  *
 422  *      This function takes the value of argv[0] rather than a full path.
 423  *
 424  * (You may be wondering why this is in exec.c.  It requires this module's
 425  * services and doesn't introduce any new dependencies, so this seems as
 426  * good as anyplace.)
 427  */
 428 void
 429 set_pglocale_pgservice(const char *argv0, const char *app)
 430 {
 431         char            path[MAXPGPATH];
 432         char            my_exec_path[MAXPGPATH];
 433
 434         /* don't set LC_ALL in the backend */
 435         if (strcmp(app, PG_TEXTDOMAIN("postgres")) != 0)
 436         {
 437                 setlocale(LC_ALL, "");
 438
 439                 /*
 440                  * One could make a case for reproducing here PostmasterMain()'s test
 441                  * for whether the process is multithreaded.  Unlike the postmaster,
 442                  * no frontend program calls sigprocmask() or otherwise provides for
 443                  * mutual exclusion between signal handlers.  While frontends using
 444                  * fork(), if multithreaded, are formally exposed to undefined
 445                  * behavior, we have not witnessed a concrete bug.  Therefore,
 446                  * complaining about multithreading here may be mere pedantry.
 447                  */
 448         }
 449
 450         if (find_my_exec(argv0, my_exec_path) < 0)
 451                 return;
 452
 453 #ifdef ENABLE_NLS
 454         get_locale_path(my_exec_path, path);
 455         bindtextdomain(app, path);
 456         textdomain(app);
 457         /* set for libpq to use, but don't override existing setting */
 458         setenv("PGLOCALEDIR", path, 0);
 459 #endif
 460
 461         if (getenv("PGSYSCONFDIR") == NULL)
 462         {
 463                 get_etc_path(my_exec_path, path);
 464                 /* set for libpq to use */
 465                 setenv("PGSYSCONFDIR", path, 0);
 466         }
 467 }
 468
 469 #ifdef EXEC_BACKEND
 470 /*
 471  * For the benefit of PostgreSQL developers testing EXEC_BACKEND on Unix
 472  * systems (code paths normally exercised only on Windows), provide a way to
 473  * disable address space layout randomization, if we know how on this platform.
 474  * Otherwise, backends may fail to attach to shared memory at the fixed address
 475  * chosen by the postmaster.  (See also the macOS-specific hack in
 476  * sysv_shmem.c.)
 477  */
 478 int
 479 pg_disable_aslr(void)
 480 {
 481 #if defined(HAVE_SYS_PERSONALITY_H)
 482         return personality(ADDR_NO_RANDOMIZE);
 483 #elif defined(HAVE_SYS_PROCCTL_H) && defined(PROC_ASLR_FORCE_DISABLE)
 484         int                     data = PROC_ASLR_FORCE_DISABLE;
 485
 486         return procctl(P_PID, 0, PROC_ASLR_CTL, &data);
 487 #else
 488         errno = ENOSYS;
 489         return -1;
 490 #endif
 491 }
 492 #endif
 493
 494 #ifdef WIN32
 495
 496 /*
 497  * AddUserToTokenDacl(HANDLE hToken)
 498  *
 499  * This function adds the current user account to the restricted
 500  * token used when we create a restricted process.
 501  *
 502  * This is required because of some security changes in Windows
 503  * that appeared in patches to XP/2K3 and in Vista/2008.
 504  *
 505  * On these machines, the Administrator account is not included in
 506  * the default DACL - you just get Administrators + System. For
 507  * regular users you get User + System. Because we strip Administrators
 508  * when we create the restricted token, we are left with only System
 509  * in the DACL which leads to access denied errors for later CreatePipe()
 510  * and CreateProcess() calls when running as Administrator.
 511  *
 512  * This function fixes this problem by modifying the DACL of the
 513  * token the process will use, and explicitly re-adding the current
 514  * user account.  This is still secure because the Administrator account
 515  * inherits its privileges from the Administrators group - it doesn't
 516  * have any of its own.
 517  */
 518 BOOL
 519 AddUserToTokenDacl(HANDLE hToken)
 520 {
 521         int                     i;
 522         ACL_SIZE_INFORMATION asi;
 523         ACCESS_ALLOWED_ACE *pace;
 524         DWORD           dwNewAclSize;
 525         DWORD           dwSize = 0;
 526         DWORD           dwTokenInfoLength = 0;
 527         PACL            pacl = NULL;
 528         PTOKEN_USER pTokenUser = NULL;
 529         TOKEN_DEFAULT_DACL tddNew;
 530         TOKEN_DEFAULT_DACL *ptdd = NULL;
 531         TOKEN_INFORMATION_CLASS tic = TokenDefaultDacl;
 532         BOOL            ret = FALSE;
 533
 534         /* Figure out the buffer size for the DACL info */
 535         if (!GetTokenInformation(hToken, tic, (LPVOID) NULL, dwTokenInfoLength, &dwSize))
 536         {
 537                 if (GetLastError() == ERROR_INSUFFICIENT_BUFFER)
 538                 {
 539                         ptdd = (TOKEN_DEFAULT_DACL *) LocalAlloc(LPTR, dwSize);
 540                         if (ptdd == NULL)
 541                         {
 542                                 log_error(errcode(ERRCODE_OUT_OF_MEMORY),
 543                                                   _("out of memory"));
 544                                 goto cleanup;
 545                         }
 546
 547                         if (!GetTokenInformation(hToken, tic, (LPVOID) ptdd, dwSize, &dwSize))
 548                         {
 549                                 log_error(errcode(ERRCODE_SYSTEM_ERROR),
 550                                                   "could not get token information: error code %lu",
 551                                                   GetLastError());
 552                                 goto cleanup;
 553                         }
 554                 }
 555                 else
 556                 {
 557                         log_error(errcode(ERRCODE_SYSTEM_ERROR),
 558                                           "could not get token information buffer size: error code %lu",
 559                                           GetLastError());
 560                         goto cleanup;
 561                 }
 562         }
 563
 564         /* Get the ACL info */
 565         if (!GetAclInformation(ptdd->DefaultDacl, (LPVOID) &asi,
 566                                                    (DWORD) sizeof(ACL_SIZE_INFORMATION),
 567                                                    AclSizeInformation))
 568         {
 569                 log_error(errcode(ERRCODE_SYSTEM_ERROR),
 570                                   "could not get ACL information: error code %lu",
 571                                   GetLastError());
 572                 goto cleanup;
 573         }
 574
 575         /* Get the current user SID */
 576         if (!GetTokenUser(hToken, &pTokenUser))
 577                 goto cleanup;                   /* callee printed a message */
 578
 579         /* Figure out the size of the new ACL */
 580         dwNewAclSize = asi.AclBytesInUse + sizeof(ACCESS_ALLOWED_ACE) +
 581                 GetLengthSid(pTokenUser->User.Sid) - sizeof(DWORD);
 582
 583         /* Allocate the ACL buffer & initialize it */
 584         pacl = (PACL) LocalAlloc(LPTR, dwNewAclSize);
 585         if (pacl == NULL)
 586         {
 587                 log_error(errcode(ERRCODE_OUT_OF_MEMORY),
 588                                   _("out of memory"));
 589                 goto cleanup;
 590         }
 591
 592         if (!InitializeAcl(pacl, dwNewAclSize, ACL_REVISION))
 593         {
 594                 log_error(errcode(ERRCODE_SYSTEM_ERROR),
 595                                   "could not initialize ACL: error code %lu", GetLastError());
 596                 goto cleanup;
 597         }
 598
 599         /* Loop through the existing ACEs, and build the new ACL */
 600         for (i = 0; i < (int) asi.AceCount; i++)
 601         {
 602                 if (!GetAce(ptdd->DefaultDacl, i, (LPVOID *) &pace))
 603                 {
 604                         log_error(errcode(ERRCODE_SYSTEM_ERROR),
 605                                           "could not get ACE: error code %lu", GetLastError());
 606                         goto cleanup;
 607                 }
 608
 609                 if (!AddAce(pacl, ACL_REVISION, MAXDWORD, pace, ((PACE_HEADER) pace)->AceSize))
 610                 {
 611                         log_error(errcode(ERRCODE_SYSTEM_ERROR),
 612                                           "could not add ACE: error code %lu", GetLastError());
 613                         goto cleanup;
 614                 }
 615         }
 616
 617         /* Add the new ACE for the current user */
 618         if (!AddAccessAllowedAceEx(pacl, ACL_REVISION, OBJECT_INHERIT_ACE, GENERIC_ALL, pTokenUser->User.Sid))
 619         {
 620                 log_error(errcode(ERRCODE_SYSTEM_ERROR),
 621                                   "could not add access allowed ACE: error code %lu",
 622                                   GetLastError());
 623                 goto cleanup;
 624         }
 625
 626         /* Set the new DACL in the token */
 627         tddNew.DefaultDacl = pacl;
 628
 629         if (!SetTokenInformation(hToken, tic, (LPVOID) &tddNew, dwNewAclSize))
 630         {
 631                 log_error(errcode(ERRCODE_SYSTEM_ERROR),
 632                                   "could not set token information: error code %lu",
 633                                   GetLastError());
 634                 goto cleanup;
 635         }
 636
 637         ret = TRUE;
 638
 639 cleanup:
 640         if (pTokenUser)
 641                 LocalFree((HLOCAL) pTokenUser);
 642
 643         if (pacl)
 644                 LocalFree((HLOCAL) pacl);
 645
 646         if (ptdd)
 647                 LocalFree((HLOCAL) ptdd);
 648
 649         return ret;
 650 }
 651
 652 /*
 653  * GetTokenUser(HANDLE hToken, PTOKEN_USER *ppTokenUser)
 654  *
 655  * Get the users token information from a process token.
 656  *
 657  * The caller of this function is responsible for calling LocalFree() on the
 658  * returned TOKEN_USER memory.
 659  */
 660 static BOOL
 661 GetTokenUser(HANDLE hToken, PTOKEN_USER *ppTokenUser)
 662 {
 663         DWORD           dwLength;
 664
 665         *ppTokenUser = NULL;
 666
 667         if (!GetTokenInformation(hToken,
 668                                                          TokenUser,
 669                                                          NULL,
 670                                                          0,
 671                                                          &dwLength))
 672         {
 673                 if (GetLastError() == ERROR_INSUFFICIENT_BUFFER)
 674                 {
 675                         *ppTokenUser = (PTOKEN_USER) LocalAlloc(LPTR, dwLength);
 676
 677                         if (*ppTokenUser == NULL)
 678                         {
 679                                 log_error(errcode(ERRCODE_OUT_OF_MEMORY),
 680                                                   _("out of memory"));
 681                                 return FALSE;
 682                         }
 683                 }
 684                 else
 685                 {
 686                         log_error(errcode(ERRCODE_SYSTEM_ERROR),
 687                                           "could not get token information buffer size: error code %lu",
 688                                           GetLastError());
 689                         return FALSE;
 690                 }
 691         }
 692
 693         if (!GetTokenInformation(hToken,
 694                                                          TokenUser,
 695                                                          *ppTokenUser,
 696                                                          dwLength,
 697                                                          &dwLength))
 698         {
 699                 LocalFree(*ppTokenUser);
 700                 *ppTokenUser = NULL;
 701
 702                 log_error(errcode(ERRCODE_SYSTEM_ERROR),
 703                                   "could not get token information: error code %lu",
 704                                   GetLastError());
 705                 return FALSE;
 706         }
 707
 708         /* Memory in *ppTokenUser is LocalFree():d by the caller */
 709         return TRUE;
 710 }
 711
 712 #endif