508 lines
17 KiB
PHP
508 lines
17 KiB
PHP
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; sshlib_dh_gex.inc - Diffie Hellman Group exchange
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;
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; Copyright (C) 2015-2021 Jeffrey Amelynck
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;
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; This program is free software: you can redistribute it and/or modify
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; it under the terms of the GNU General Public License as published by
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; the Free Software Foundation, either version 3 of the License, or
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; (at your option) any later version.
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;
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; This program is distributed in the hope that it will be useful,
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; but WITHOUT ANY WARRANTY; without even the implied warranty of
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; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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; GNU General Public License for more details.
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;
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; You should have received a copy of the GNU General Public License
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; along with this program. If not, see <http://www.gnu.org/licenses/>.
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; https://www.ietf.org/rfc/rfc4419.txt
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proc sshlib_dh_gex con_ptr
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locals
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mpint_tmp dd ?
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mpint_p dd ?
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mpint_g dd ?
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mpint_x dd ?
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mpint_e dd ?
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mpint_f dd ?
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mpint_K_big dd ?
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k_h_ctx dd ?
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temp_ctx dd ?
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H dd ? ; exchange hash
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rx_iv dd ? ; Rx initialisation vector
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tx_iv dd ? ; Tx initialisation vector
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rx_enc_key dd ? ; Rx encryption key
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tx_enc_key dd ? ; Tx encryption key
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rx_int_key dd ? ; Rx integrity key
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tx_int_key dd ? ; Tx integrity key
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K_length dd ?
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session_id_x rb SHA256_HASH_SIZE+1
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str_K_S dd ? ; server public host key and certificates (K_S)
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mpint_f_big dd ? ; pointer to original
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str_s_of_H dd ? ; signature of H
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endl
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; Allocate memory for temp variables
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mov ecx, 7*(MAX_BITS/8+4) + 7*SHA256_HASH_SIZE + 2*sizeof.crash_ctx
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mcall 68, 12
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test eax, eax
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jz .err_nomem
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; Init pointers for temp variables
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mov [mpint_tmp], eax
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add eax, (MAX_BITS/8+4)
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mov [mpint_p], eax
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add eax, (MAX_BITS/8+4)
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mov [mpint_g], eax
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add eax, (MAX_BITS/8+4)
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mov [mpint_x], eax
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add eax, (MAX_BITS/8+4)
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mov [mpint_e], eax
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add eax, (MAX_BITS/8+4)
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mov [mpint_f], eax
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add eax, (MAX_BITS/8+4)
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mov [mpint_K_big], eax
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add eax, (MAX_BITS/8+4)
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mov [k_h_ctx], eax
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add eax, sizeof.crash_ctx
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mov [temp_ctx], eax
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add eax, sizeof.crash_ctx
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mov [H], eax
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add eax, SHA256_HASH_SIZE
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mov [rx_iv], eax
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add eax, SHA256_HASH_SIZE
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mov [tx_iv], eax
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add eax, SHA256_HASH_SIZE
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mov [rx_enc_key], eax
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add eax, SHA256_HASH_SIZE
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mov [tx_enc_key], eax
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add eax, SHA256_HASH_SIZE
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mov [rx_int_key], eax
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add eax, SHA256_HASH_SIZE
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mov [tx_int_key], eax
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; add eax, SHA256_HASH_SIZE
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; Copy the partial exchange hash to our temporary one
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mov esi, [con_ptr]
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lea esi, [esi+sshlib_connection.part_ex_hash_ctx]
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mov edi, [temp_ctx]
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mov ecx, sizeof.crash_ctx/4
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rep movsd
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;----------------------------------------------
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; >> Send Diffie-Hellman Group Exchange Request
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DEBUGF 2, "Sending GEX\n"
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stdcall sshlib_send_packet, [con_ptr], ssh_msg_gex_req, ssh_msg_gex_req.length, 0
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cmp eax, 0
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jl .err
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;---------------------------------------------
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; << Parse Diffie-Hellman Group Exchange Group
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stdcall sshlib_recv_packet, [con_ptr], 0
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cmp eax, 0
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jl .err
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mov ebx, [con_ptr]
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cmp [ebx + sshlib_connection.rx_buffer.message_code], SSH_MSG_KEX_DH_GEX_GROUP
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jne .err_proto
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DEBUGF 2, "Received GEX group\n"
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lea esi, [ebx + sshlib_connection.rx_buffer + sizeof.ssh_packet_header]
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stdcall mpint_to_little_endian, [mpint_p], esi
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add esi, 4
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add esi, eax
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DEBUGM 1, "DH modulus (p): ", [mpint_p]
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stdcall mpint_to_little_endian, [mpint_g], esi
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add esi, 4
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add esi, eax
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DEBUGM 1, "DH base (g): ", [mpint_g]
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;-------------------------------------------
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; >> Send Diffie-Hellman Group Exchange Init
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; generate a random number x, where 1 < x < (p-1)/2
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mov edi, [mpint_x]
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mov dword[edi], DH_PRIVATE_KEY_SIZE/8
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add edi, 4
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mov ecx, DH_PRIVATE_KEY_SIZE/8/4
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@@:
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push ecx
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call MBRandom
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pop ecx
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stosd
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dec ecx
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jnz @r
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; If the highest bit is set, add a zero byte
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shl eax, 1
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jnc @f
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mov byte[edi], 0
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mov eax, [mpint_x]
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inc dword[eax]
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@@:
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DEBUGM 1, "DH private key (x): ", [mpint_x]
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; Compute e = g^x mod p
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stdcall mpint_modexp, [mpint_e], [mpint_g], [mpint_x], [mpint_p]
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stdcall mpint_shrink, [mpint_e]
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DEBUGM 1, "DH public key (e): ", [mpint_e]
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; Create group exchange init packet
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mov byte[ebx + sshlib_connection.tx_buffer.message_code], SSH_MSG_KEX_DH_GEX_INIT
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lea edi, [ebx + sshlib_connection.tx_buffer.message_code+1]
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stdcall mpint_to_big_endian, edi, [mpint_e]
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DEBUGF 2, "Sending GEX init\n"
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mov ecx, dword[ebx + sshlib_connection.tx_buffer.message_code+1] ;;;; dword[edi]
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bswap ecx
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add ecx, 5
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lea esi, [ebx + sshlib_connection.tx_buffer.message_code]
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stdcall sshlib_send_packet, [con_ptr], esi, ecx, 0
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cmp eax, 0
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jl .err
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;---------------------------------------------
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; << Parse Diffie-Hellman Group Exchange Reply
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stdcall sshlib_recv_packet, [con_ptr], 0
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cmp eax, 0
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jl .err
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mov ebx, [con_ptr]
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cmp [ebx + sshlib_connection.rx_buffer.message_code], SSH_MSG_KEX_DH_GEX_REPLY
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jne .err_proto
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DEBUGF 2, "Received GEX Reply\n"
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;--------------------------------
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; HASH: string K_S, the host key
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lea esi, [ebx + sshlib_connection.rx_buffer + sizeof.ssh_packet_header]
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mov [str_K_S], esi
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mov edx, [esi]
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bswap edx
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add edx, 4
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lea eax, [esi+edx]
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mov [mpint_f_big], eax
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invoke sha256_update, [temp_ctx], esi, edx
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;--------------------------------------------------------------------------
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; HASH: uint32 min, minimal size in bits of an acceptable group
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; uint32 n, preferred size in bits of the group the server will send
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; uint32 max, maximal size in bits of an acceptable group
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invoke sha256_update, [temp_ctx], ssh_msg_gex_req+sizeof.ssh_packet_header-ssh_packet_header.message_code, 12
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;----------------------------
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; HASH: mpint p, safe prime
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stdcall mpint_shrink, [mpint_p]
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stdcall mpint_to_big_endian, [mpint_tmp], [mpint_p]
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add eax, 4
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invoke sha256_update, [temp_ctx], [mpint_tmp], eax
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;----------------------------------------
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; HASH: mpint g, generator for subgroup
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stdcall mpint_shrink, [mpint_g]
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stdcall mpint_to_big_endian, [mpint_tmp], [mpint_g]
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add eax, 4
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invoke sha256_update, [temp_ctx], [mpint_tmp], eax
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;---------------------------------------------------
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; HASH: mpint e, exchange value sent by the client
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mov ebx, [con_ptr]
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lea esi, [ebx + sshlib_connection.tx_buffer + sizeof.ssh_packet_header]
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mov edx, [esi]
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bswap edx
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add edx, 4
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invoke sha256_update, [temp_ctx], esi, edx
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;---------------------------------------------------
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; HASH: mpint f, exchange value sent by the server
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mov esi, [mpint_f_big]
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mov edx, [esi]
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bswap edx
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add edx, 4
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invoke sha256_update, [temp_ctx], esi, edx
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stdcall mpint_to_little_endian, [mpint_f], [mpint_f_big]
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mov esi, [mpint_f_big]
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add esi, eax
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add esi, 4
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mov [str_s_of_H], esi
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DEBUGM 1, "DH exchange value (f): ", [mpint_f]
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;--------------------------------------
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; Calculate shared secret K = f^x mod p
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stdcall mpint_modexp, [mpint_tmp], [mpint_f], [mpint_x], [mpint_p]
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stdcall mpint_shrink, [mpint_tmp]
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DEBUGM 1, "DH shared secret (K): ", [mpint_tmp]
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; We always need it in big endian order, so store it as such.
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stdcall mpint_to_big_endian, [mpint_K_big], [mpint_tmp]
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mov [K_length], eax
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;-----------------------------------
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; HASH: mpint K, the shared secret
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add eax, 4
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invoke sha256_update, [temp_ctx], [mpint_K_big], eax
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;-------------------------------
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; Finalize the exchange hash (H)
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invoke sha256_final, [temp_ctx]
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mov esi, [temp_ctx]
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add esi, crash_ctx.hash
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mov edi, [H]
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mov ecx, SHA256_HASH_SIZE/4
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rep movsd
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DEBUGF 1, "Exchange hash H: "
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stdcall dump_hex, [H], SHA256_HASH_SIZE/4
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;--------------------------
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; Set or get the session id
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mov eax, [con_ptr]
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cmp [eax + sshlib_connection.status], SSHLIB_CON_STAT_KEX_DONE
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jae @f
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; If first KEX, verify host public key
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stdcall sshlib_host_verify, [con_ptr], [str_K_S], [str_s_of_H], [H], SHA256_HASH_SIZE
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test eax, eax
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jnz .err
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mov eax, [con_ptr]
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mov esi, [H]
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lea edi, [eax + sshlib_connection.session_id]
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mov ecx, SHA256_HASH_SIZE/4
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rep movsd
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@@:
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lea esi, [eax + sshlib_connection.session_id]
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lea edi, [session_id_x+1]
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mov ecx, SHA256_HASH_SIZE/4
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rep movsd
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;---------------
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; Calculate keys
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; First, calculate partial hash of K and H so we can re-use it for every key.
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invoke sha256_init, [k_h_ctx]
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mov ecx, [K_length]
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add ecx, 4
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invoke sha256_update, [k_h_ctx], [mpint_K_big], ecx
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invoke sha256_update, [k_h_ctx], [H], SHA256_HASH_SIZE
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;---------------------------------------------------------------
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; Initial IV client to server: HASH(K || H || "A" || session_id)
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mov esi, [k_h_ctx]
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mov edi, [temp_ctx]
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mov ecx, sizeof.crash_ctx/4
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rep movsd
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lea edx, [session_id_x]
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mov byte[edx], 'A'
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invoke sha256_update, [temp_ctx], edx, SHA256_HASH_SIZE+1
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invoke sha256_final, [temp_ctx]
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mov edi, [tx_iv]
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mov esi, [temp_ctx]
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mov ecx, SHA256_HASH_SIZE/4
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rep movsd
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DEBUGF 1, "Remote IV: "
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stdcall dump_hex, [tx_iv], SHA256_HASH_SIZE/4
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;---------------------------------------------------------------
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; Initial IV server to client: HASH(K || H || "B" || session_id)
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mov esi, [k_h_ctx]
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mov edi, [temp_ctx]
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mov ecx, sizeof.crash_ctx/4
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rep movsd
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lea edx, [session_id_x]
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mov byte[edx], 'B'
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invoke sha256_update, [temp_ctx], edx, SHA256_HASH_SIZE+1
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invoke sha256_final, [temp_ctx]
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mov edi, [rx_iv]
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mov esi, [temp_ctx]
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mov ecx, SHA256_HASH_SIZE/4
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rep movsd
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DEBUGF 1, "Local IV: "
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stdcall dump_hex, [rx_iv], SHA256_HASH_SIZE/4
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;-------------------------------------------------------------------
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; Encryption key client to server: HASH(K || H || "C" || session_id)
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mov esi, [k_h_ctx]
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mov edi, [temp_ctx]
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mov ecx, sizeof.crash_ctx/4
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rep movsd
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lea edx, [session_id_x]
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mov byte[edx], 'C'
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invoke sha256_update, [temp_ctx], edx, SHA256_HASH_SIZE+1
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||
|
|
invoke sha256_final, [temp_ctx]
|
||
|
|
mov edi, [tx_enc_key]
|
||
|
|
mov esi, [temp_ctx]
|
||
|
|
mov ecx, SHA256_HASH_SIZE/4
|
||
|
|
rep movsd
|
||
|
|
|
||
|
|
DEBUGF 1, "Remote key: "
|
||
|
|
stdcall dump_hex, [tx_enc_key], SHA256_HASH_SIZE/4
|
||
|
|
|
||
|
|
;-------------------------------------------------------------------
|
||
|
|
; Encryption key server to client: HASH(K || H || "D" || session_id)
|
||
|
|
|
||
|
|
mov esi, [k_h_ctx]
|
||
|
|
mov edi, [temp_ctx]
|
||
|
|
mov ecx, sizeof.crash_ctx/4
|
||
|
|
rep movsd
|
||
|
|
lea edx, [session_id_x]
|
||
|
|
mov byte[edx], 'D'
|
||
|
|
invoke sha256_update, [temp_ctx], edx, SHA256_HASH_SIZE+1
|
||
|
|
invoke sha256_final, [temp_ctx]
|
||
|
|
mov edi, [rx_enc_key]
|
||
|
|
mov esi, [temp_ctx]
|
||
|
|
mov ecx, SHA256_HASH_SIZE/4
|
||
|
|
rep movsd
|
||
|
|
|
||
|
|
DEBUGF 1, "Local key: "
|
||
|
|
stdcall dump_hex, [rx_enc_key], SHA256_HASH_SIZE/4
|
||
|
|
|
||
|
|
;------------------------------------------------------------------
|
||
|
|
; Integrity key client to server: HASH(K || H || "E" || session_id)
|
||
|
|
|
||
|
|
mov esi, [k_h_ctx]
|
||
|
|
mov edi, [temp_ctx]
|
||
|
|
mov ecx, sizeof.crash_ctx/4
|
||
|
|
rep movsd
|
||
|
|
lea edx, [session_id_x]
|
||
|
|
mov byte[edx], 'E'
|
||
|
|
invoke sha256_update, [temp_ctx], edx, SHA256_HASH_SIZE+1
|
||
|
|
invoke sha256_final, [temp_ctx]
|
||
|
|
mov edi, [tx_int_key]
|
||
|
|
mov esi, [temp_ctx]
|
||
|
|
mov ecx, SHA256_HASH_SIZE/4
|
||
|
|
rep movsd
|
||
|
|
|
||
|
|
DEBUGF 1, "Remote Integrity key: "
|
||
|
|
stdcall dump_hex, [tx_int_key], SHA256_HASH_SIZE/4
|
||
|
|
|
||
|
|
;------------------------------------------------------------------
|
||
|
|
; Integrity key server to client: HASH(K || H || "F" || session_id)
|
||
|
|
|
||
|
|
mov esi, [k_h_ctx]
|
||
|
|
mov edi, [temp_ctx]
|
||
|
|
mov ecx, sizeof.crash_ctx/4
|
||
|
|
rep movsd
|
||
|
|
lea edx, [session_id_x]
|
||
|
|
mov byte[edx], 'F'
|
||
|
|
invoke sha256_update, [temp_ctx], edx, SHA256_HASH_SIZE+1
|
||
|
|
invoke sha256_final, [temp_ctx]
|
||
|
|
mov edi, [rx_int_key]
|
||
|
|
mov esi, [temp_ctx]
|
||
|
|
mov ecx, SHA256_HASH_SIZE/4
|
||
|
|
rep movsd
|
||
|
|
|
||
|
|
DEBUGF 1, "Local Integrity key: "
|
||
|
|
stdcall dump_hex, [rx_int_key] , SHA256_HASH_SIZE/4
|
||
|
|
|
||
|
|
;-------------------------------------
|
||
|
|
; << Parse Diffie-Hellman New Keys MSG
|
||
|
|
|
||
|
|
stdcall sshlib_recv_packet, [con_ptr], 0
|
||
|
|
cmp eax, 0
|
||
|
|
jl .err
|
||
|
|
|
||
|
|
mov ebx, [con_ptr]
|
||
|
|
cmp [ebx + sshlib_connection.rx_buffer.message_code], SSH_MSG_NEWKEYS
|
||
|
|
jne .err_proto
|
||
|
|
|
||
|
|
DEBUGF 2, "Received New Keys\n"
|
||
|
|
|
||
|
|
;-------------------------------
|
||
|
|
; >> Reply with New Keys message
|
||
|
|
|
||
|
|
stdcall sshlib_send_packet, [con_ptr], ssh_msg_new_keys, ssh_msg_new_keys.length, 0
|
||
|
|
cmp eax, 0
|
||
|
|
jl .err
|
||
|
|
|
||
|
|
;----------------------------------------------
|
||
|
|
; Set keys and initialize transport subroutines
|
||
|
|
|
||
|
|
DEBUGF 2, "SSH: Setting encryption keys\n"
|
||
|
|
|
||
|
|
mov ebx, [con_ptr]
|
||
|
|
stdcall aes256_ctr_init, [rx_iv]
|
||
|
|
test eax, eax
|
||
|
|
jz .err_nomem
|
||
|
|
mov [ebx + sshlib_connection.rx_crypt_ctx_ptr], eax
|
||
|
|
stdcall aes256_set_encrypt_key, eax, [rx_enc_key]
|
||
|
|
mov [ebx + sshlib_connection.rx_crypt_proc], aes256_ctr_crypt
|
||
|
|
mov [ebx + sshlib_connection.rx_crypt_blocksize], AES256_BLOCKSIZE
|
||
|
|
|
||
|
|
stdcall aes256_ctr_init, [tx_iv]
|
||
|
|
test eax, eax
|
||
|
|
jz .err_nomem
|
||
|
|
mov [ebx + sshlib_connection.tx_crypt_ctx_ptr], eax
|
||
|
|
stdcall aes256_set_encrypt_key, eax, [tx_enc_key]
|
||
|
|
mov [ebx + sshlib_connection.tx_crypt_proc], aes256_ctr_crypt
|
||
|
|
mov [ebx + sshlib_connection.tx_crypt_blocksize], AES256_BLOCKSIZE
|
||
|
|
|
||
|
|
mov [ebx + sshlib_connection.tx_pad_size], AES256_BLOCKSIZE
|
||
|
|
mov [ebx + sshlib_connection.tx_pad_proc], MBRandom
|
||
|
|
|
||
|
|
lea ecx, [ebx + sshlib_connection.rx_mac_ctx]
|
||
|
|
stdcall hmac_sha256_setkey, ecx, [rx_int_key], SHA256_HASH_SIZE
|
||
|
|
mov [ebx + sshlib_connection.rx_mac_proc], hmac_sha256
|
||
|
|
mov [ebx + sshlib_connection.rx_mac_length], SHA256_HASH_SIZE
|
||
|
|
|
||
|
|
lea ecx, [ebx + sshlib_connection.tx_mac_ctx]
|
||
|
|
stdcall hmac_sha256_setkey, ecx, [tx_int_key], SHA256_HASH_SIZE
|
||
|
|
mov [ebx + sshlib_connection.tx_mac_proc], hmac_sha256
|
||
|
|
mov [ebx + sshlib_connection.tx_mac_length], SHA256_HASH_SIZE
|
||
|
|
|
||
|
|
mov [ebx + sshlib_connection.status], SSHLIB_CON_STAT_KEX_DONE
|
||
|
|
xor eax, eax
|
||
|
|
|
||
|
|
.err:
|
||
|
|
push eax
|
||
|
|
xor eax, eax
|
||
|
|
mov ecx, (7*(MAX_BITS/8+4) + 7*SHA256_HASH_SIZE + 2*sizeof.crash_ctx)/4
|
||
|
|
mov edi, [mpint_tmp]
|
||
|
|
rep stosd
|
||
|
|
|
||
|
|
mcall 68, 13, [mpint_tmp]
|
||
|
|
pop eax
|
||
|
|
ret
|
||
|
|
|
||
|
|
.err_nomem:
|
||
|
|
DEBUGF 3, "Out of memory during key exchange!\n"
|
||
|
|
mov eax, SSHLIB_ERR_NOMEM
|
||
|
|
ret
|
||
|
|
|
||
|
|
.err_proto:
|
||
|
|
DEBUGF 3, "Protocol error during key exchange!\n"
|
||
|
|
mov eax, SSHLIB_ERR_PROTOCOL
|
||
|
|
jmp .err
|
||
|
|
|
||
|
|
endp
|