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Enforces $max_connects and implements input timeout.
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@icculus
icculus committed May 9, 2002
1 parent 9c01547 commit 50d3b72
Showing 1 changed file with 82 additions and 31 deletions.
113 changes: 82 additions & 31 deletions IcculusFinger_daemon.pl
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Expand Up @@ -41,9 +41,9 @@
# !!! TODO: Make [center] tags attempt to format plain text.


use strict; # don't touch this line, nootch.
use warnings; # don't touch this line, either.
use DBI; # or this. I guess. Maybe.
use strict; # don't touch this line, nootch.
use warnings; # don't touch this line, either.
use DBI; # or this. I guess. Maybe.

# Version of IcculusFinger. Change this if you are forking the code.
my $version = "v2.0.5";
Expand All @@ -63,6 +63,12 @@
# URLs. "$url?user=$user&section=sectionname".
my $base_url = 'http://icculus.org/cgi-bin/finger/finger.pl';

# The processes path is replaced with this string, for security reasons, and
# to satisfy the requirements of Taint mode. Make this as simple as possible.
# Currently, the only thing that uses the PATH environment var is the
# "fortune" fakeuser, which can be safely removed.
my $safe_path = '/usr/bin:/usr/local/bin';

# Turn the process into a daemon. This will handle creating/answering socket
# connections, and forking off children to handle them. This flag can be
# toggle via command line options (--daemonize, --no-daemonize, -d), but this
Expand Down Expand Up @@ -93,7 +99,18 @@
# clients will be made to wait until some of the current requests are
# serviced. 5 to 10 is usually a good number. Set it higher if you get a
# massive amount of finger requests simultaneously.
my $max_connects = 5;
my $max_connects = 10;

# This is how long, in seconds, before an idle connection will be summarily
# dropped. This prevents abuse from people hogging a connection without
# actually sending a request, without this, enough connections like this
# will block legitimate ones. At worst, they can only block for this long
# before being booted and thus freeing their connection slot for the next
# guy in line. Setting this to undef lets people sit forever, but removes
# reliance on the IO::Select package. Note that this timeout is how long
# they user has to complete the read_request() function, so don't set it so
# low that legitimate lag can kill them. The default is usually safe.
my $read_timeout = 15;

# Set this to non-zero to log all finger requests via the standard Unix
# syslog facility (requires Sys::Syslog qw(:DEFAULT setlogsock) ...)
Expand Down Expand Up @@ -134,7 +151,7 @@
# This is the maximum size, in bytes, that a finger request can be. This is
# to prevent malicious finger clients from trying to fill all of system
# memory.
my $max_request_size = 1024;
my $max_request_size = 512;

# This is what is reported to the finger client if the desired user's planfile
# is missing or empty, or the user is unknown (we make NO distinction, for
Expand Down Expand Up @@ -853,37 +870,63 @@ sub do_fingering {


sub read_request {
my $ch;
my $count;
my $retval = '';
my $count = 0;
my $s = undef;
my $elapsed = undef;
my $starttime = undef;

if (defined $read_timeout) {
$s = new IO::Select();
$s->add(fileno(STDIN));
$starttime = time();
$elapsed = 0;
}

while (1) {
if (defined $read_timeout) {
my $ready = scalar($s->can_read($read_timeout - $elapsed));
return undef if (not $ready);
$elapsed = (time() - $starttime);
}

for ($count = 0; $count < $max_request_size; $count++) {
# !!! FIXME: A timeout would be great, here.
$ch = getc(STDIN);
my $ch;
my $rc = sysread(STDIN, $ch, 1);
return undef if ($rc != 1);
if ($ch ne "\015") {
last if (($ch eq '') or ($ch eq "\012"));
return($retval) if (($ch eq '') or ($ch eq "\012"));
$retval .= $ch;
$count++;
return($retval) if ($count >= $max_request_size);
}
}

return($retval);
return(undef); # shouldn't ever hit this.
}


sub finger_mainline {
my $query_string = read_request();

if ($use_syslog) {
syslog("info", "finger request: \"$query_string\"\n")
or die("Couldn't write to syslog: $!\n");
}
my $syslog_text;
if (not defined $query_string) {
$syslog_text = "input timeout on finger request. Dropped client.\n";
print($syslog_text); # tell the client, if they care.
syslog("info", $syslog_text) if ($use_syslog);
} else {
$syslog_text = "finger request: \"$query_string\"\n";
if ($use_syslog) {
syslog("info", $syslog_text) or
die("Couldn't write to syslog: $!\n");
}

my ($user, $args) = $query_string =~ /\A(.*?)(\?.*|\b)\Z/;
$user =~ tr/A-Z/a-z/ if defined $user;
$args = parse_args($args);
my ($user, $args) = $query_string =~ /\A(.*?)(\?.*|\b)\Z/;
$user =~ tr/A-Z/a-z/ if defined $user;
$args = parse_args($args);

if (verify_and_load_request($args, $user)) {
do_fingering($query_string, $user)
if (verify_and_load_request($args, $user)) {
do_fingering($query_string, $user)
}
}

return(0);
Expand Down Expand Up @@ -912,14 +955,18 @@ sub go_to_background {

sub drop_privileges {
delete @ENV{qw(IFS CDPATH ENV BASH_ENV)};
$ENV{'PATH'} = '/usr/bin:/usr/local/bin';
$ENV{'PATH'} = $safe_path;
$) = $wanted_gid if (defined $wanted_gid);
$> = $wanted_uid if (defined $wanted_uid);
}


# Mainline.

if (defined $read_timeout) {
use IO::Select;
}

foreach (@ARGV) {
$daemonize = 1, next if $_ eq '--daemonize';
$daemonize = 1, next if $_ eq '-d';
Expand All @@ -942,9 +989,9 @@ sub drop_privileges {
} else {
go_to_background();

# clean up zombies from future forks...
use POSIX ":sys_wait_h";
$SIG{CHLD} = sub { 1 until (waitpid(-1, WNOHANG) == -1); };
# reap zombies from client forks...
my $total_kids = 0;
$SIG{CHLD} = sub { wait(); $total_kids--; };

use IO::Socket::INET;
my $listensock = IO::Socket::INET->new(LocalPort => $server_port,
Expand All @@ -958,6 +1005,9 @@ sub drop_privileges {

while (1)
{
# prevent connection floods.
sleep(1) while ($total_kids >= $max_connects);

my $client = $listensock->accept();
syslog_and_die("accept() failed: $!") if (not $client);

Expand All @@ -969,21 +1019,22 @@ sub drop_privileges {
my $kidpid = fork();
syslog_and_die("fork() failed: $!") if (not defined $kidpid);

if ($kidpid == 0) { # this is the child process.
close($listensock); # no need for listen socket in child.
if ($kidpid) { # this is the parent process.
close($client); # parent has no use for client socket.
$total_kids++;
} else {
close($listensock); # child has no use for listen socket.
local *FH = $client;
open(STDIN, "<&FH") or syslog_and_die("no STDIN reassign: $!");
open(STDERR, ">&FH") or syslog_and_die("no STDERR reassign: $!");
open(STDOUT, ">&FH") or syslog_and_die("no STDOUT reassign: $!");
my $retval = finger_mainline();
close($client);
exit $retval;
exit $retval; # kill child.
}

close($client); # parent has no use for this socket.
}

close($listensock); # probably won't ever hit this.
close($listensock); # shouldn't ever hit this.
}

exit $retval;
Expand Down

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