Annotation of loncom/lcpasswd, revision 1.8

1.1       harris41    1: #!/usr/bin/perl
1.3       harris41    2: #
                      3: # lcpasswd
                      4: #
                      5: # Scott Harrison
1.6       harris41    6: # SH: October 27, 2000
                      7: # SH: October 28, 2000
1.1       harris41    8: 
                      9: use strict;
                     10: 
                     11: # This script is a setuid script that should
1.4       harris41   12: # be run by user 'www'.  This script allows
                     13: # for synchronous entry of passwords into
                     14: # both the /etc/passwd and the /etc/smbpasswd
                     15: # files.
1.1       harris41   16: 
1.5       harris41   17: # This script works under the same process control mechanism
                     18: # as lcuseradd and lcpasswd, to make sure that only one of these
                     19: # processes is running at any one time on the system.
                     20: 
1.1       harris41   21: # Standard input usage
                     22: # First line is USERNAME
                     23: # Second line is CURRENT PASSWORD
                     24: # Third line is NEW PASSWORD
                     25: 
1.8     ! harris41   26: # Valid passwords must consist of the
        !            27: # ascii characters within the inclusive
        !            28: # range of 0x20 (32) to 0x7E (126).
        !            29: # These characters are:
        !            30: # SPACE and
        !            31: # !"#$%&'()*+,-./0123456789:;<=>?@ABCDEFGHIJKLMNO
        !            32: # PQRSTUVWXYZ[\]^_`abcdefghijklmnopqrstuvwxyz{|}~
        !            33: 
        !            34: # Valid user names must consist of ascii
        !            35: # characters that are alphabetical characters
        !            36: # (A-Z,a-z), numeric (0-9), or the underscore
        !            37: # mark (_). (Essentially, the perl regex \w).
        !            38: 
1.4       harris41   39: # Command-line arguments
                     40: # Yes, but be very careful here (don't pass shell commands)
                     41: # and this is only supported to allow perl-system calls.
                     42: 
                     43: # Usage within code
1.5       harris41   44: # Note: NEVER run as system("/home/httpd/perl/lcpasswd NAME OLDPWD NEWPWD")
1.4       harris41   45: #
1.5       harris41   46: # $exitcode=system("/home/httpd/perl/lcpasswd","NAME","OLDPWD","NEWPWD")/256;
1.4       harris41   47: # print "uh-oh" if $exitcode;
                     48: 
                     49: # These are the exit codes.
                     50: # ( (0,"ok"),
1.7       harris41   51: #   (1,"User ID mismatch.  This program must be run as user 'www'"),
1.4       harris41   52: #   (2,"Error. This program does not accept command-line arguments."),
1.6       harris41   53: #   (3,"Error. Three lines need to be entered into standard input."),
                     54: #   (4,"Error. Too many other simultaneous password change requests being made."),
                     55: #   (5,"Error. User $username does not exist."),
                     56: #   (6,"Error. Invalid entry of current password."),
1.7       harris41   57: #   (7,"Error.  Root was not successfully enabled."),
1.6       harris41   58: #   (8,"Error.  Cannot open /etc/passwd.") )
1.4       harris41   59: 
1.1       harris41   60: # Security
1.6       harris41   61: $ENV{'PATH'}='/bin:/usr/bin'; # Nullify path information except for what smbpasswd needs
                     62: $ENV{'BASH_ENV'}=''; # Nullify shell environment information.
1.1       harris41   63: 
1.4       harris41   64: # Do not print error messages if there are command-line arguments
                     65: my $noprint=0;
                     66: if (@ARGV) {
                     67:     $noprint=1;
                     68: }
                     69: 
1.5       harris41   70: # Read in /etc/passwd, and make sure this process is running from user=www
1.6       harris41   71: open (IN, '</etc/passwd');
1.1       harris41   72: my @lines=<IN>;
                     73: close IN;
                     74: my $wwwid;
                     75: for my $l (@lines) {
                     76:     chop $l;
                     77:     my @F=split(/\:/,$l);
                     78:     if ($F[0] eq 'www') {$wwwid=$F[2];}
                     79: }
                     80: if ($wwwid!=$<) {
1.4       harris41   81:     print("User ID mismatch.  This program must be run as user 'www'\n") unless $noprint;
                     82:     exit 1;
1.1       harris41   83: }
1.2       harris41   84: &disable_root_capability;
1.1       harris41   85: 
1.5       harris41   86: # Handle case of another lcpasswd process
1.6       harris41   87: unless (&try_to_lock('/tmp/lock_lcpasswd')) {
1.5       harris41   88:     print "Error. Too many other simultaneous password change requests being made.\n" unless $noprint;
                     89:     exit 4;
                     90: }
                     91: 
1.4       harris41   92: # Gather input.  Should only be 3 values.
                     93: my @input;
                     94: if (@ARGV==3) {
                     95:     @input=@ARGV;
                     96: }
                     97: elsif (@ARGV) {
                     98:     print("Error. This program needs 3 command-line arguments (username, old password, new password).\n") unless $noprint;
1.6       harris41   99:     unlink('/tmp/lock_lcpasswd');
1.4       harris41  100:     exit 2;
                    101: }
                    102: else {
                    103:     @input=<>;
                    104:     if (@input!=3) {
                    105: 	print("Error. Three lines need to be entered into standard input.\n") unless $noprint;
1.6       harris41  106: 	unlink('/tmp/lock_lcpasswd');
1.4       harris41  107: 	exit 3;
                    108:     }
                    109:     map {chop} @input;
1.1       harris41  110: }
                    111: 
1.4       harris41  112: my ($username,$oldpwd,$newpwd)=@input;
1.8     ! harris41  113: $username=~/^(\w+)$/;
        !           114: my $safeusername=$1;
        !           115: if ($username ne $safeusername) {
        !           116:     print "Error. The user name specified has invalid characters.\n";
        !           117:     unlink('/tmp/lock_lcpasswd');
        !           118:     exit 9;
        !           119: }
        !           120: 
1.1       harris41  121: 
                    122: # Grab the line corresponding to username
                    123: my ($userid,$useroldcryptpwd);
                    124: my @F; my @U;
                    125: for my $l (@lines) {
                    126:     @F=split(/\:/,$l);
                    127:     if ($F[0] eq $username) {($userid,$useroldcryptpwd)=($F[2],$F[1]); @U=@F;}
                    128: }
                    129: 
                    130: # Verify existence of user
                    131: if (!defined($userid)) {
1.4       harris41  132:     print "Error. User $username does not exist.\n" unless $noprint;
1.6       harris41  133:     unlink('/tmp/lock_lcpasswd');
1.4       harris41  134:     exit 5;
1.1       harris41  135: }
                    136: 
                    137: # Verify password entry
                    138: if (crypt($oldpwd,$useroldcryptpwd) ne $useroldcryptpwd) {
1.4       harris41  139:     print "Error. Invalid entry of current password.\n" unless $noprint;
1.6       harris41  140:     unlink('/tmp/lock_lcpasswd');
1.4       harris41  141:     exit 6;
1.1       harris41  142: }
                    143: 
1.2       harris41  144: # Construct new password entry (random salt)
                    145: my $newcryptpwd=crypt($newpwd,(join '', ('.', '/', 0..9, 'A'..'Z', 'a'..'z')[rand 64, rand 64]));
1.1       harris41  146: $U[1]=$newcryptpwd;
1.6       harris41  147: my $userline=join(':',@U);
1.2       harris41  148: my $rootid=&enable_root_capability;
                    149: if ($rootid!=0) {
1.4       harris41  150:     print "Error.  Root was not successfully enabled.\n" unless $noprint;
1.6       harris41  151:     unlink('/tmp/lock_lcpasswd');
1.4       harris41  152:     exit 7;
1.2       harris41  153: }
1.6       harris41  154: open PASSWORDFILE, '>/etc/passwd' or (print("Error.  Cannot open /etc/passwd.\n") && unlink('/tmp/lock_lcpasswd') && exit(8));
1.1       harris41  155: for my $l (@lines) {
                    156:     @F=split(/\:/,$l);
                    157:     if ($F[0] eq $username) {print PASSWORDFILE "$userline\n";}
                    158:     else {print PASSWORDFILE "$l\n";}
                    159: }
                    160: close PASSWORDFILE;
1.8     ! harris41  161: 
1.2       harris41  162: ($>,$<)=(0,0); # fool smbpasswd here to think this is not a setuid environment
1.6       harris41  163: unless (-e '/etc/smbpasswd') {
                    164:     open (OUT,'>/etc/smbpasswd'); close OUT;
1.2       harris41  165: }
                    166: my $smbexist=0;
1.6       harris41  167: open (IN, '</etc/smbpasswd');
1.2       harris41  168: my @lines=<IN>;
                    169: close IN;
                    170: for my $l (@lines) {
                    171:     chop $l;
                    172:     my @F=split(/\:/,$l);
                    173:     if ($F[0] eq $username) {$smbexist=1;}
                    174: }
                    175: unless ($smbexist) {
1.6       harris41  176:     open(OUT,'>>/etc/smbpasswd');
                    177:     print OUT join(':',($safeusername,$userid,'XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX:XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX','','/home/'.$safeusername,'/bin/bash')) . "\n";
1.2       harris41  178:     close OUT;
                    179: }
                    180: open(OUT,"|/usr/bin/smbpasswd -s $safeusername>/dev/null");
                    181: print OUT $newpwd; print OUT "\n";
                    182: print OUT $newpwd; print OUT "\n";
                    183: close OUT;
                    184: $<=$wwwid; # unfool the program
1.1       harris41  185: &disable_root_capability;
1.6       harris41  186: unlink('/tmp/lock_lcpasswd');
1.4       harris41  187: exit 0;
1.1       harris41  188: 
1.4       harris41  189: # ----------------------------------------------------------- have setuid script run as root
1.1       harris41  190: sub enable_root_capability {
1.2       harris41  191:     if ($wwwid==$>) {
1.1       harris41  192: 	($<,$>)=($>,$<);
                    193: 	($(,$))=($),$();
                    194:     }
                    195:     else {
                    196: 	# root capability is already enabled
                    197:     }
1.2       harris41  198:     return $>;
1.1       harris41  199: }
                    200: 
1.4       harris41  201: # ----------------------------------------------------------- have setuid script run as www
1.1       harris41  202: sub disable_root_capability {
1.2       harris41  203:     if ($wwwid==$<) {
1.1       harris41  204: 	($<,$>)=($>,$<);
                    205: 	($(,$))=($),$();
                    206:     }
                    207:     else {
                    208: 	# root capability is already disabled
                    209:     }
                    210: }
                    211: 
1.4       harris41  212: # ----------------------------------- make sure that another lcpasswd process isn't running
1.1       harris41  213: sub try_to_lock {
                    214:     my ($lockfile)=@_;
                    215:     my $currentpid;
                    216:     my $lastpid;
1.5       harris41  217:     # Do not manipulate lock file as root
                    218:     if ($>==0) {
                    219: 	return 0;
                    220:     }
                    221:     # Try to generate lock file.
                    222:     # Wait 3 seconds.  If same process id is in
                    223:     # lock file, then assume lock file is stale, and
                    224:     # go ahead.  If process id's fluctuate, try
                    225:     # for a maximum of 10 times.
1.1       harris41  226:     for (0..10) {
                    227: 	if (-e $lockfile) {
                    228: 	    open(LOCK,"<$lockfile");
                    229: 	    $currentpid=<LOCK>;
                    230: 	    close LOCK;
                    231: 	    if ($currentpid==$lastpid) {
                    232: 		last;
                    233: 	    }
                    234: 	    sleep 3;
                    235: 	    $lastpid=$currentpid;
                    236: 	}
                    237: 	else {
                    238: 	    last;
                    239: 	}
                    240: 	if ($_==10) {
                    241: 	    return 0;
                    242: 	}
                    243:     }
                    244:     open(LOCK,">$lockfile");
                    245:     print LOCK $$;
                    246:     close LOCK;
                    247:     return 1;
                    248: }

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