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Restore the uid to www after running smbpasswd as euid root, uid root.

    1: #!/usr/bin/perl
    2: #
    3: # lcuserdel
    4: #
    5: # Scott Harrison
    6: # SH: October 27, 2000
    7: # SH: October 28, 2000
    8: # SH: October 29, 2000
    9: 
   10: use strict;
   11: 
   12: # This script is a setuid script (chmod 6755) that should
   13: # be run by user 'www'.  It DOES NOT delete directories.
   14: # All it does is remove a user's entries from
   15: # /etc/passwd, /etc/groups, and /etc/smbpasswd.
   16: # It also disables user directory access by making the directory
   17: # to be owned by user=www (as opposed to the former "username").
   18: # This command only returns an error if it is
   19: # invoked incorrectly (by passing bad command-line arguments, etc).
   20: 
   21: # This script works under the same process control mechanism
   22: # as lcuseradd and lcpasswd, to make sure that only one of these
   23: # processes is running at any one time on the system.
   24: 
   25: # Standard input usage
   26: # First line is USERNAME
   27: 
   28: # Valid user names must consist of ascii
   29: # characters that are alphabetical characters
   30: # (A-Z,a-z), numeric (0-9), or the underscore
   31: # mark (_). (Essentially, the perl regex \w).
   32: 
   33: # Command-line arguments [USERNAME]
   34: # Yes, but be very careful here (don't pass shell commands)
   35: # and this is only supported to allow perl-system calls.
   36: 
   37: # Usage within code
   38: #
   39: # $exitcode=system("/home/httpd/perl/lcuserdel","NAME")/256;
   40: # print "uh-oh" if $exitcode;
   41: 
   42: # These are the exit codes.
   43: # ( (0,"ok"),
   44: #   (1,"User ID mismatch.  This program must be run as user 'www'"),
   45: #   (2,"Error. This program needs just 1 command-line argument (username).") )
   46: #   (3,"Error. Only one line should be entered into standard input."),
   47: #   (4,"Error. Too many other simultaneous password change requests being made."),
   48: #   (5,"Error. The user name specified has invalid characters.") )
   49: 
   50: # Security
   51: $ENV{'PATH'}=""; # Nullify path information.
   52: $ENV{'BASH_ENV'}=""; # Nullify shell environment information.
   53: 
   54: # Do not print error messages if there are command-line arguments
   55: my $noprint=0;
   56: if (@ARGV) {
   57:     $noprint=1;
   58: }
   59: 
   60: # Read in /etc/passwd, and make sure this process is running from user=www
   61: open (IN, "</etc/passwd");
   62: my @lines=<IN>;
   63: close IN;
   64: my $wwwid;
   65: for my $l (@lines) {
   66:     chop $l;
   67:     my @F=split(/\:/,$l);
   68:     if ($F[0] eq 'www') {$wwwid=$F[2];}
   69: }
   70: if ($wwwid!=$<) {
   71:     print("User ID mismatch.  This program must be run as user 'www'\n") unless $noprint;
   72:     exit 1;
   73: }
   74: &disable_root_capability;
   75: 
   76: # Handle case of another lcpasswd process
   77: unless (&try_to_lock("/tmp/lock_lcpasswd")) {
   78:     print "Error. Too many other simultaneous password change requests being made.\n" unless $noprint;
   79:     exit 4;
   80: }
   81: 
   82: # Gather input.  Should only be 1 value (user name).
   83: my @input;
   84: if (@ARGV==1) {
   85:     @input=@ARGV;
   86: }
   87: elsif (@ARGV) {
   88:     print("Error. This program needs just 1 command-line argument (username).\n") unless $noprint;
   89:     unlink('/tmp/lock_lcpasswd');
   90:     exit 2;
   91: }
   92: else {
   93:     @input=<>;
   94:     if (@input!=1) {
   95: 	print("Error. Only one line should be entered into standard input.\n") unless $noprint;
   96: 	unlink('/tmp/lock_lcpasswd');
   97: 	exit 3;
   98:     }
   99:     map {chop} @input;
  100: }
  101: 
  102: my ($username)=@input;
  103: $username=~/^(\w+)$/;
  104: my $safeusername=$1;
  105: if ($username ne $safeusername) {
  106:     print "Error. The user name specified has invalid characters.\n";
  107:     unlink('/tmp/lock_lcpasswd');
  108:     exit 5;
  109: }
  110: 
  111: &enable_root_capability;
  112: 
  113: # By using the system userdel command:
  114: # Remove entry from /etc/passwd if it exists
  115: # Remove entry from /etc/groups if it exists
  116: # I surround with groupdel command to make absolutely sure the group definition disappears.
  117: system('/usr/sbin/groupdel',$safeusername); # ignore error message
  118: system('/usr/sbin/userdel',$safeusername); # ignore error message
  119: system('/usr/sbin/groupdel',$safeusername); # ignore error message
  120: 
  121: # Remove entry from /etc/smbpasswd if it exists
  122: #  the safest way to do this is with smbpasswd -x
  123: #  as that's independent of location of the smbpasswd file.
  124: #
  125: if (-e '/usr/bin/smbpasswd') {
  126:   ($>,$<) = (0,0);		# fool smbpasswd to think this is not setuid.
  127:   system('/usr/bin/smbpasswd -x '.$safeusername);
  128:   $< = $wwwid;
  129: }
  130: 
  131: 
  132: # Change ownership on directory from username:username to www:www
  133: # This prevents subsequently added users from having access.
  134: 
  135: system('/bin/chown','-R','www:www',"/home/$safeusername");
  136: 
  137: &disable_root_capability;
  138: unlink("/tmp/lock_lcpasswd");
  139: exit 0;
  140: 
  141: # ----------------------------------------------------------- have setuid script run as root
  142: sub enable_root_capability {
  143:     if ($wwwid==$>) {
  144: 	($<,$>)=($>,$<);
  145: 	($(,$))=($),$();
  146:     }
  147:     else {
  148: 	# root capability is already enabled
  149:     }
  150:     return $>;
  151: }
  152: 
  153: # ----------------------------------------------------------- have setuid script run as www
  154: sub disable_root_capability {
  155:     if ($wwwid==$<) {
  156: 	($<,$>)=($>,$<);
  157: 	($(,$))=($),$();
  158:     }
  159:     else {
  160: 	# root capability is already disabled
  161:     }
  162: }
  163: 
  164: # ----------------------------------- make sure that another lcpasswd process isn't running
  165: sub try_to_lock {
  166:     my ($lockfile)=@_;
  167:     my $currentpid;
  168:     my $lastpid;
  169:     # Do not manipulate lock file as root
  170:     if ($>==0) {
  171: 	return 0;
  172:     }
  173:     # Try to generate lock file.
  174:     # Wait 3 seconds.  If same process id is in
  175:     # lock file, then assume lock file is stale, and
  176:     # go ahead.  If process id's fluctuate, try
  177:     # for a maximum of 10 times.
  178:     for (0..10) {
  179: 	if (-e $lockfile) {
  180: 	    open(LOCK,"<$lockfile");
  181: 	    $currentpid=<LOCK>;
  182: 	    close LOCK;
  183: 	    if ($currentpid==$lastpid) {
  184: 		last;
  185: 	    }
  186: 	    sleep 3;
  187: 	    $lastpid=$currentpid;
  188: 	}
  189: 	else {
  190: 	    last;
  191: 	}
  192: 	if ($_==10) {
  193: 	    return 0;
  194: 	}
  195:     }
  196:     open(LOCK,">$lockfile");
  197:     print LOCK $$;
  198:     close LOCK;
  199:     return 1;
  200: }
  201: 
  202: