433 lines
12 KiB
PHP
433 lines
12 KiB
PHP
; sshlib_host.inc - SSH remote host authentication
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;
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; Copyright (C) 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://datatracker.ietf.org/doc/html/rfc4253#section-6.6
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; https://datatracker.ietf.org/doc/html/rfc3447
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; https://datatracker.ietf.org/doc/html/rfc4716
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; https://datatracker.ietf.org/doc/html/rfc8017
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proc sshlib_host_verify con_ptr, str_host_key, str_signature, message, message_len
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locals
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current_hkb64 rb MAX_PUBLIC_KEY_SIZE*4 ; Current Host key in Base64
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cached_hkb64 rb MAX_PUBLIC_KEY_SIZE*4 ; Cached Host key in Base64
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key_name_sz dd ?
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hostname_sz dd ?
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current_hk64_end dd ?
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endl
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mov eax, [con_ptr]
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lea ebx, [eax + sshlib_connection.hostname_sz]
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mov [hostname_sz], ebx
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cmp [eax+sshlib_connection.algo_hostkey], SSHLIB_HOSTKEY_RSA
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je .rsa
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; ..add more here
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mov eax, SSHLIB_ERR_HKEY_NO_ALGO
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ret
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.rsa:
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stdcall sshlib_host_verify_rsa, [str_host_key], [str_signature], [message], [message_len]
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test eax, eax
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jnz .err
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mov [key_name_sz], ssh_rsa_sz
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.lookup:
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; Convert the current host key to base64
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mov esi, [str_host_key]
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mov ecx, [esi]
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bswap ecx
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add esi, 4
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lea edi, [current_hkb64]
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call base64_encode
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mov [current_hk64_end], edi
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; Try to read the cached key for this host and key type
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lea edi, [cached_hkb64]
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invoke ini_get_str, known_hostsfile, [hostname_sz], [key_name_sz], edi, MAX_PUBLIC_KEY_SIZE*4, 0
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test eax, eax
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jnz .unknown
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; If the cached key is empty, return SSHLIB_HOSTKEY_PROBLEM_UNKNOWN
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lea esi, [cached_hkb64]
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cmp byte[esi], 0
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je .unknown
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; Else, compare it to the current one
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lea edi, [current_hkb64]
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mov ecx, MAX_PUBLIC_KEY_SIZE*4
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.cmploop:
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lodsb
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scasb
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jne .mismatch
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test al, al
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jz .match
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dec ecx
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jnz .cmploop
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jmp .mismatch
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.match:
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xor eax, eax
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ret
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.mismatch:
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int3
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lea eax, [current_hkb64]
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stdcall sshlib_callback_hostkey_problem, [con_ptr], SSHLIB_HOSTKEY_PROBLEM_MISMATCH, eax
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cmp eax, SSHLIB_HOSTKEY_ACCEPT
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je .store
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ret
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.unknown:
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lea eax, [current_hkb64]
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stdcall sshlib_callback_hostkey_problem, [con_ptr], SSHLIB_HOSTKEY_PROBLEM_UNKNOWN, eax
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cmp eax, SSHLIB_HOSTKEY_ACCEPT
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je .store
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ret
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.store:
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lea esi, [current_hkb64]
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mov ecx, [current_hk64_end]
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sub ecx, esi
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invoke ini_set_str, known_hostsfile, [hostname_sz], [key_name_sz], esi, ecx
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xor eax, eax
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ret
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.err:
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ret
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endp
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; https://datatracker.ietf.org/doc/html/rfc3447#section-8.2.2
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; RSASSA-PKCS1-V1_5-VERIFY
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proc sshlib_host_verify_rsa str_host_key, str_signature, M, message_len
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locals
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h_ctx dd ?
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; Signer's RSA public key
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mpint_e dd ? ; public exponent
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mpint_n dd ? ; modulus
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mpint_m dd ?
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EM dd ?
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EM_accent dd ?
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mpint_s dd ? ; rsa_signature_blob
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k dd ? ; Key length
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endl
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DEBUGF 3, "SSH: Performing RSA verification\n"
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mcall 68, 12, sizeof.crash_ctx + 5*(MAX_BITS/8+4)
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test eax, eax
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jz .err_nomem
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mov [h_ctx], eax
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add eax, sizeof.crash_ctx
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mov [mpint_e], eax
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add eax, MAX_BITS/8+4
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mov [mpint_n], eax
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add eax, MAX_BITS/8+4
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mov [mpint_m], eax
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add eax, MAX_BITS/8+4
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mov [EM], eax
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add eax, MAX_BITS/8+4
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mov [EM_accent], eax
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add eax, MAX_BITS/8+4
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mov [mpint_s], eax
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; add eax, MAX_BITS/8+4
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; Host key
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mov esi, [str_host_key]
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mov ecx, [esi]
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bswap ecx
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cmp ecx, MAX_PUBLIC_KEY_SIZE
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ja .err_key
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; Host key type (string)
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cmp dword[esi+4], 0x07000000
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jne .err_key
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cmp dword[esi+8], 'ssh-'
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jne .err_key
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cmp dword[esi+11], '-rsa'
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jne .err_key
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add esi, 4+4+7
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; mpint e
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stdcall mpint_to_little_endian, [mpint_e], esi
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add esi, eax
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add esi, 4
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; mpint n
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stdcall mpint_to_little_endian, [mpint_n], esi
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and eax, not (32-1) ; CHECKME
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mov [k], eax
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; Signature
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mov esi, [str_signature]
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mov ecx, [esi]
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bswap ecx ; TODO: check length
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; Host key type (string)
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cmp dword[esi+4], 0x07000000
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jne .not_ssh_rsa
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cmp dword[esi+8], 'ssh-'
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jne .not_ssh_rsa
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cmp dword[esi+11], '-rsa'
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je .sha1
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.not_ssh_rsa:
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cmp dword[esi+4], 0x0c000000
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jne .not_sha2
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cmp dword[esi+8], 'rsa-'
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jne .not_sha2
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cmp dword[esi+12], 'sha2'
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jne .not_sha2
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cmp dword[esi+16], '-256'
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je .sha2_256
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cmp dword[esi+16], '-512'
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je .sha2_512
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.not_sha2:
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jmp .err_signature
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.sha1:
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DEBUGF 3, "SSH: Using RSA with SHA1 hash\n"
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add esi, 4+4+7
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push esi
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; EMSA-PKCS1-v1_5
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invoke sha1_init, [h_ctx]
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invoke sha1_update, [h_ctx], [M], [message_len]
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invoke sha1_final, [h_ctx]
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mov edi, [EM_accent]
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mov al, 0x00
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stosb
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mov al, 0x01
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stosb
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mov ecx, [k]
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sub ecx, (rsa_sha1_T.len + 3 + SHA1_HASH_SIZE)
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jl .err_key
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jz @f
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mov al, 0xff
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rep stosb
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@@:
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mov al, 0x00
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stosb
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mov esi, rsa_sha1_T
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mov ecx, rsa_sha1_T.len
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rep movsb
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mov esi, [h_ctx]
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mov ecx, SHA1_HASH_SIZE
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rep movsb
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pop esi
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jmp .rsa
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.sha2_256:
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DEBUGF 3, "SSH: Using RSA with SHA2-256 hash\n"
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add esi, 4+4+12
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push esi
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; EMSA-PKCS1-v1_5
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invoke sha256_init, [h_ctx]
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invoke sha256_update, [h_ctx], [M], [message_len]
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invoke sha256_final, [h_ctx]
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mov edi, [EM_accent]
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mov al, 0x00
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stosb
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mov al, 0x01
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stosb
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mov ecx, [k]
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sub ecx, (rsa_sha256_T.len + 3 + SHA256_HASH_SIZE)
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jl .err_key
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jz @f
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mov al, 0xff
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rep stosb
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@@:
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mov al, 0x00
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stosb
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mov esi, rsa_sha256_T
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mov ecx, rsa_sha256_T.len
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rep movsb
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mov esi, [h_ctx]
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mov ecx, SHA256_HASH_SIZE
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rep movsb
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pop esi
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jmp .rsa
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.sha2_512:
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DEBUGF 3, "SSH: Using RSA with SHA2-512 hash\n"
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add esi, 4+4+12
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push esi
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; EMSA-PKCS1-v1_5
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invoke sha512_init, [h_ctx]
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invoke sha512_update, [h_ctx], [M], [message_len]
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invoke sha512_final, [h_ctx]
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mov edi, [EM_accent]
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mov al, 0x00
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stosb
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mov al, 0x01
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stosb
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mov ecx, [k]
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sub ecx, (rsa_sha512_T.len + 3 + SHA512_HASH_SIZE)
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jl .err_key
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jz @f
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mov al, 0xff
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rep stosb
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@@:
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mov al, 0x00
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stosb
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mov esi, rsa_sha512_T
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mov ecx, rsa_sha512_T.len
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rep movsb
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mov esi, [h_ctx]
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mov ecx, SHA512_HASH_SIZE
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rep movsb
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pop esi
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jmp .rsa
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.rsa:
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; RSA signature blob
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stdcall mpint_to_little_endian, [mpint_s], esi
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; cmp eax, [k]
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; jne .err_signature
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; RSAVP1
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stdcall mpint_modexp, [mpint_m], [mpint_s], [mpint_e], [mpint_n]
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; I2OSP
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stdcall mpint_shrink, [mpint_m]
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stdcall mpint_grow, [mpint_m], [k]
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stdcall mpint_to_big_endian, [EM], [mpint_m]
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; Compare EM with EM_accent
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mov esi, [EM]
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add esi, 4
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mov edi, [EM_accent]
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mov ecx, [k]
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shr ecx, 2
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xor eax, eax
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.ct_cmp_loop:
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mov ebx, [esi]
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xor ebx, [edi]
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or eax, ebx
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lea esi, [esi+4]
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lea edi, [edi+4]
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dec ecx
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jnz .ct_cmp_loop
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push eax
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mcall 68, 13, [h_ctx]
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pop eax
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test eax, eax
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jnz .fail
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DEBUGF 3, "SSH: RSA verification OK!\n"
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ret
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.fail:
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DEBUGF 3, "SSH: RSA verification failed!\n"
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mov eax, SSHLIB_ERR_HKEY_VERIFY_FAIL
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ret
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.err_nomem:
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mov eax, SSHLIB_ERR_NOMEM
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ret
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.err_signature:
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mov eax, SSHLIB_ERR_HKEY_SIGNATURE
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ret
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.err_key:
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mov eax, SSHLIB_ERR_HKEY_PUBLIC_KEY
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ret
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endp
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base64_encode:
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xor ebx, ebx
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.loop:
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lodsb
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call .byte
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dec ecx
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jnz .loop
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.final:
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mov al, 0
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test ebx, ebx
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jz .f000
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call .byte
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test ebx, ebx
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jz .f001
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call .byte
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mov byte[edi-2], '='
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.f001:
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mov byte[edi-1], '='
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.f000:
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mov byte[edi], 0
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ret
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.byte:
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inc ebx
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shl edx, 8
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mov dl, al
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cmp ebx, 3
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je .b001
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ret
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.b001:
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shl edx, 8
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inc ebx
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.b002:
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rol edx, 6
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xor eax, eax
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xchg al, dl
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mov al, [base64_table+eax]
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stosb
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dec ebx
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jnz .b002
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ret
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iglobal
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known_hostsfile db '/sys/settings/known_hosts.ini', 0
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base64_table db 'ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/'
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rsa_sha1_T db 0x30, 0x21, 0x30, 0x09, 0x06, 0x05, 0x2B, 0x0E, 0x03, 0x02, 0x1A, 0x05, 0x00, 0x04, 0x14
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.len = $ - rsa_sha1_T
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rsa_sha256_T db 0x30, 0x31, 0x30, 0x0d, 0x06, 0x09, 0x60, 0x86, 0x48, 0x01, 0x65, 0x03, 0x04, 0x02, 0x01, 0x05, 0x00, 0x04, 0x20
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.len = $ - rsa_sha256_T
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rsa_sha512_T db 0x30, 0x51, 0x30, 0x0d, 0x06, 0x09, 0x60, 0x86, 0x48, 0x01, 0x65, 0x03, 0x04, 0x02, 0x03, 0x05, 0x00, 0x04, 0x40
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.len = $ - rsa_sha512_T
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ssh_rsa_sz db 'ssh-rsa', 0
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endg
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