src/common/username.c

   1 /*-------------------------------------------------------------------------
   2  *
   3  * username.c
   4  *        get user name
   5  *
   6  * Portions Copyright (c) 1996-2024, PostgreSQL Global Development Group
   7  * Portions Copyright (c) 1994, Regents of the University of California
   8  *
   9  * IDENTIFICATION
  10  *        src/common/username.c
  11  *
  12  *-------------------------------------------------------------------------
  13  */
  14
  15 #ifndef FRONTEND
  16 #include "postgres.h"
  17 #else
  18 #include "postgres_fe.h"
  19 #endif
  20
  21 #include <pwd.h>
  22 #include <unistd.h>
  23
  24 #include "common/username.h"
  25
  26 /*
  27  * Returns the current user name in a static buffer
  28  * On error, returns NULL and sets *errstr to point to a palloc'd message
  29  */
  30 const char *
  31 get_user_name(char **errstr)
  32 {
  33 #ifndef WIN32
  34         struct passwd *pw;
  35         uid_t           user_id = geteuid();
  36
  37         *errstr = NULL;
  38
  39         errno = 0;                                      /* clear errno before call */
  40         pw = getpwuid(user_id);
  41         if (!pw)
  42         {
  43                 *errstr = psprintf(_("could not look up effective user ID %ld: %s"),
  44                                                    (long) user_id,
  45                                                    errno ? strerror(errno) : _("user does not exist"));
  46                 return NULL;
  47         }
  48
  49         return pw->pw_name;
  50 #else
  51         /* Microsoft recommends buffer size of UNLEN+1, where UNLEN = 256 */
  52         /* "static" variable remains after function exit */
  53         static char username[256 + 1];
  54         DWORD           len = sizeof(username);
  55
  56         *errstr = NULL;
  57
  58         if (!GetUserName(username, &len))
  59         {
  60                 *errstr = psprintf(_("user name lookup failure: error code %lu"),
  61                                                    GetLastError());
  62                 return NULL;
  63         }
  64
  65         return username;
  66 #endif
  67 }
  68
  69
  70 /*
  71  * Returns the current user name in a static buffer or exits
  72  */
  73 const char *
  74 get_user_name_or_exit(const char *progname)
  75 {
  76         const char *user_name;
  77         char       *errstr;
  78
  79         user_name = get_user_name(&errstr);
  80
  81         if (!user_name)
  82         {
  83                 fprintf(stderr, "%s: %s\n", progname, errstr);
  84                 exit(1);
  85         }
  86         return user_name;
  87 }