login-utils/setpwnam.c

   1 /*
   2  *  setpwnam.c --
   3  *  edit an entry in a password database.
   4  *
   5  *  (c) 1994 Salvatore Valente <svalente@mit.edu>
   6  *  This file is free software; you can redistribute it and/or
   7  *  modify it under the terms of the GNU Library General Public License as
   8  *  published by the Free Software Foundation; either version 2 of the
   9  *  License, or (at your option) any later version.
  10  *
  11  *  Edited 11/10/96 (DD/MM/YY ;-) by Nicolai Langfeldt (janl@math.uio.no)
  12  *  to read /etc/passwd directly so that passwd, chsh and chfn can work
  13  *  on machines that run NIS (né YP).  Changes will not be made to
  14  *  usernames starting with +.
  15  *
  16  *  This file is distributed with no warranty.
  17  *
  18  *  Usage:
  19  *  1) get a struct passwd * from getpwnam().
  20  *     You should assume a struct passwd has an infinite number of fields,
  21  *     so you should not try to create one from scratch.
  22  *  2) edit the fields you want to edit.
  23  *  3) call setpwnam() with the edited struct passwd.
  24  *
  25  *  A _normal user_ program should never directly manipulate
  26  *  /etc/passwd but use getpwnam() and (family, as well as)
  27  *  setpwnam().
  28  *
  29  *  But, setpwnam was made to _edit_ the password file.  For use by
  30  *  chfn, chsh and passwd.  _I_ _HAVE_ to read and write /etc/passwd
  31  *  directly.  Let those who say nay be forever silent and think about
  32  *  how getpwnam (and family) works on a machine running YP.
  33  *
  34  *  Added checks for failure of malloc() and removed error reporting
  35  *  to stderr, this is a library function and should not print on the
  36  *  screen, but return appropriate error codes.
  37  *  27-Jan-97  - poe@daimi.aau.dk
  38  *
  39  *  Thanks to "two guys named Ian".
  40  *
  41  *   $Author: poer $
  42  *   $Revision: 1.13 $
  43  *   $Date: 1997/06/23 08:26:29 $
  44  *
  45  */
  46
  47 #undef DEBUG
  48
  49 /*  because I use getpwent(), putpwent(), etc... */
  50 #define _SVID_SOURCE
  51
  52 #include <sys/types.h>
  53 #include <stdio.h>
  54 #include <string.h>
  55 #include <stdlib.h>
  56 #include <unistd.h>
  57 #include <fcntl.h>
  58 #include <pwd.h>
  59 #include <errno.h>
  60 #include <signal.h>
  61 #include <sys/resource.h>
  62 #include <sys/stat.h>
  63 #include <paths.h>
  64
  65 #include "setpwnam.h"
  66
  67 #define false 0
  68 #define true 1
  69
  70 typedef int boolean;
  71
  72 static void pw_init(void);
  73
  74 /*
  75  *  setpwnam () --
  76  *      takes a struct passwd in which every field is filled in and valid.
  77  *      If the given username exists in the passwd file, the entry is
  78  *      replaced with the given entry.
  79  */
  80 int
  81 setpwnam (struct passwd *pwd)
  82 {
  83     FILE *fp = NULL, *pwf = NULL;
  84     int x, save_errno, fd, ret;
  85     boolean found;
  86     int oldumask;
  87     int namelen;
  88     int buflen = 256;
  89     int contlen;
  90     char *linebuf = malloc(buflen);
  91
  92     if (!linebuf) return -1;
  93
  94     oldumask = umask(0);   /* Create with exact permissions */
  95
  96     pw_init();
  97
  98     /* sanity check */
  99     for (x = 0; x < 3; x++) {
 100         if (x > 0) sleep(1);
 101         fd = open(PTMPTMP_FILE, O_WRONLY|O_CREAT, 0644);
 102         if (fd == -1) {
 103             umask(oldumask);
 104             return -1;
 105         }
 106         ret = link(PTMPTMP_FILE, PTMP_FILE);
 107         unlink(PTMPTMP_FILE);
 108         if (ret == -1)
 109             close(fd);
 110         else
 111             break;
 112     }
 113     umask(oldumask);
 114     if (ret == -1) return -1;
 115
 116     /* ptmp should be owned by root.root or root.wheel */
 117     if (chown(PTMP_FILE, (uid_t) 0, (gid_t) 0) < 0) return -1;
 118
 119     /* open ptmp for writing and passwd for reading */
 120     fp = fdopen(fd, "w");
 121     if (!fp) goto fail;
 122
 123     pwf = fopen(PASSWD_FILE, "r");
 124     if (!pwf) goto fail;
 125
 126     namelen = strlen(pwd->pw_name);
 127
 128     /* parse the passwd file */
 129     found = false;
 130     /* Do you wonder why I don't use getpwent? Read comments at top of file */
 131     while (fgets(linebuf, buflen, pwf) != NULL) {
 132         contlen = strlen(linebuf);
 133         while (linebuf[contlen-1] != '\n' && !feof(pwf)) {
 134             /* Extend input buffer if it failed getting the whole line */
 135
 136             /* So now we double the buffer size */
 137             buflen *= 2;
 138
 139             linebuf = realloc(linebuf, buflen);
 140             if (linebuf == NULL) goto fail;
 141
 142             /* And fill the rest of the buffer */
 143             if (fgets(&linebuf[contlen], buflen/2, pwf) == NULL) break;
 144             contlen = strlen(linebuf);
 145
 146             /* That was a lot of work for nothing.  Gimme perl! */
 147         }
 148
 149         /* Is this the username we were sent to change? */
 150         if (!found && linebuf[namelen] == ':' &&
 151             !strncmp(linebuf, pwd->pw_name, namelen)) {
 152             /* Yes! So go forth in the name of the Lord and change it! */
 153             if (putpwent(pwd, fp) < 0) goto fail;
 154             found = true;
 155             continue;
 156         }
 157         /* Nothing in particular happened, copy input to output */
 158         fputs(linebuf, fp);
 159     }
 160
 161     if (fclose(fp) < 0) goto fail;
 162     fp = NULL;
 163     close (fd);
 164     fd = -1;
 165     fclose (pwf); /* I don't think I want to know if this failed */
 166     pwf = NULL;
 167
 168     if (!found) {
 169         errno = ENOENT; /* give me something better */
 170         goto fail;
 171     }
 172
 173     /* we don't care if we can't remove the backup file */
 174     unlink(PASSWD_FILE".OLD");
 175     /* we don't care if we can't create the backup file */
 176     link(PASSWD_FILE, PASSWD_FILE".OLD");
 177     /* we DO care if we can't rename to the passwd file */
 178     if(rename(PTMP_FILE, PASSWD_FILE) < 0)
 179         goto fail;
 180     /* finally:  success */
 181     return 0;
 182
 183 fail:
 184     save_errno = errno;
 185     if (fp != NULL) fclose (fp);
 186     if (pwf != NULL) fclose(pwf);
 187     if (fd >= 0) close (fd);
 188     if (linebuf != NULL) free(linebuf);
 189     unlink(PTMP_FILE);
 190     errno = save_errno;
 191     return -1;
 192 }
 193
 194 /* Set up the limits so that we're not foiled */
 195
 196 static void
 197 pw_init()
 198 {
 199     struct rlimit rlim;
 200
 201     /* Unlimited resource limits. */
 202     rlim.rlim_cur = rlim.rlim_max = RLIM_INFINITY;
 203     setrlimit(RLIMIT_CPU, &rlim);
 204     setrlimit(RLIMIT_FSIZE, &rlim);
 205     setrlimit(RLIMIT_STACK, &rlim);
 206     setrlimit(RLIMIT_DATA, &rlim);
 207     setrlimit(RLIMIT_RSS, &rlim);
 208
 209 #ifndef DEBUG
 210     /* Don't drop core (not really necessary, but GP's). */
 211     rlim.rlim_cur = rlim.rlim_max = 0;
 212     setrlimit(RLIMIT_CORE, &rlim);
 213 #endif
 214
 215     /* Turn off signals. */
 216     signal(SIGALRM, SIG_IGN);
 217     signal(SIGHUP, SIG_IGN);
 218     signal(SIGINT, SIG_IGN);
 219     signal(SIGPIPE, SIG_IGN);
 220     signal(SIGQUIT, SIG_IGN);
 221     signal(SIGTERM, SIG_IGN);
 222     signal(SIGTSTP, SIG_IGN);
 223     signal(SIGTTOU, SIG_IGN);
 224
 225     /* Create with exact permissions. */
 226     umask(0);
 227 }