Subversion Repositories Kolibri OS

;    hmac.inc - HMAC: Keyed-Hashing for Message Authentication

;

;    Copyright (C) 2016 Denis Karpenko

;    Copyright (C) 2016 Jeffrey Amelynck

;

;    This program is free software: you can redistribute it and/or modify

;    it under the terms of the GNU General Public License as published by

;    the Free Software Foundation, either version 3 of the License, or

;    (at your option) any later version.

;

;    This program is distributed in the hope that it will be useful,

;    but WITHOUT ANY WARRANTY; without even the implied warranty of

;    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the

;    GNU General Public License for more details.

;

;    You should have received a copy of the GNU General Public License

;    along with this program.  If not, see .

; Main concept:

; To compute HMAC over the data `text' we perform

; H(K XOR opad, H(K XOR ipad, text))

SHA2_256_BLOCK_SIZE = 64

struct hmac_sha256_context

        hash            rb SHA2_256_LEN

        ipad_ctx        rb LIBCRASH_CTX_LEN

        opad_ctx        rb LIBCRASH_CTX_LEN

ends

; We will precompute partial hashes of K XOR ipad and K XOR opad,

; and store them in the context structure.

proc hmac_sha256_setkey ctx, key, key_length

locals

        k_temp  rb SHA2_256_BLOCK_SIZE

endl

        pusha

; input esi = key, ecx=key_length

        mov     ecx, [key_length]

        cmp     ecx, SHA2_256_BLOCK_SIZE

        ja      .hash_it

; Key is smaller then or equal to blocksize,

; copy key to ipad

        mov     esi, [key]

        lea     edi, [k_temp]

        rep movsb

        mov     ecx, SHA2_256_BLOCK_SIZE

        sub     ecx, [key_length]

        jz      .finish

; append zeros to the key

        xor     al, al

        rep stosb

        jmp     .finish

; Given key is larger then key size, hash it

  .hash_it:

        invoke  sha2_256_init, [ctx]

        invoke  sha2_256_update, [ctx], [key], [key_length]

        invoke  sha2_256_finish, [ctx]

        mov     esi, [ctx]

        lea     edi, [k_temp]

        mov     ecx, SHA2_256_LEN/4

        rep movsd

        xor     eax, eax

        mov     ecx, (SHA2_256_BLOCK_SIZE-SHA2_256_LEN)/4

        rep stosd

  .finish:

; xor ipad buffer with 0x36363...

        lea     esi, [k_temp]

        mov     ecx, SHA2_256_BLOCK_SIZE/4

  @@:

        xor     dword[esi], 0x36363636          ; ipad constant

        add     esi, 4

        dec     ecx

        jnz     @r

; Init our hash with k_xor_ipad

        mov     ebx, [ctx]

        lea     edi, [ebx+hmac_sha256_context.ipad_ctx]

        invoke  sha2_256_init, edi

        lea     esi, [k_temp]

        DEBUGF  1, "HASH: "

        stdcall dump_hex, esi, SHA2_256_BLOCK_SIZE/4

        mov     ebx, [ctx]

        lea     edi, [ebx+hmac_sha256_context.ipad_ctx]

        invoke  sha2_256_update, edi, esi, SHA2_256_BLOCK_SIZE

; xor opad buffer with 0x5c5c5...

        lea     esi, [k_temp]

        mov     ecx, SHA2_256_BLOCK_SIZE/4

  @@:

        xor     dword[esi], 0x36363636 xor 0x5c5c5c5c   ; opad constant

        add     esi, 4

        dec     ecx

        jnz     @r

; Init our hash with k_xor_opad

        mov     ebx, [ctx]

        lea     edi, [ebx+hmac_sha256_context.opad_ctx]

        invoke  sha2_256_init, edi

        lea     esi, [k_temp]

        DEBUGF  1, "HASH: "

        stdcall dump_hex, esi, SHA2_256_BLOCK_SIZE/4

        mov     ebx, [ctx]

        lea     edi, [ebx+hmac_sha256_context.opad_ctx]

        invoke  sha2_256_update, edi, esi, SHA2_256_BLOCK_SIZE

        popa

        ret

endp

; Copy our pre-computed partial hashes to the stack, complete and finalize them.

; TODO: prevent unnescessary copying of output hash

; TODO: remove unnescessary pushing/popping

proc hmac_sha256 ctx, _data, _length

locals

        inner_ctx        rb LIBCRASH_CTX_LEN

        outer_ctx        rb LIBCRASH_CTX_LEN

endl

        pusha

        DEBUGF  1, "HMAC: "

        mov     ebx, [_length]

        shr     ebx, 2

        stdcall dump_hex, [_data], ebx

; Copy partial hashes of ipad and opad to our temporary buffers

        mov     esi, [ctx]

        lea     esi, [esi+hmac_sha256_context.ipad_ctx]

        lea     edi, [inner_ctx]

repeat (LIBCRASH_CTX_LEN)/4*2

        movsd

end repeat

; Append provided data to inner hash and finalize

        lea     ebx, [inner_ctx]

        invoke  sha2_256_update, ebx, [_data], [_length]

        lea     ebx, [inner_ctx]

        invoke  sha2_256_finish, ebx

        DEBUGF  1, "Inner Hash: "

        lea     esi, [inner_ctx]

        stdcall dump_hex, esi, SHA2_256_LEN/4

; Calculate outer hash

        lea     ebx, [outer_ctx]

        lea     esi, [inner_ctx]

        invoke  sha2_256_update, ebx, esi, SHA2_256_LEN

        lea     ebx, [outer_ctx]

        invoke  sha2_256_finish, ebx

; Copy output hash to ctx structure     ; FIXME

        lea     esi, [outer_ctx]

        mov     edi, [ctx]

repeat SHA2_256_LEN/4

        movsd

end repeat

        popa

        ret

endp