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|
/*****************************************************************
|
| AP4 - HMAC Algorithms
|
| Copyright 2002-2009 Axiomatic Systems, LLC
|
|
| This file is part of Bento4/AP4 (MP4 Atom Processing Library).
|
| Unless you have obtained Bento4 under a difference license,
| this version of Bento4 is Bento4|GPL.
| Bento4|GPL 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 2, or (at your option)
| any later version.
|
| Bento4|GPL 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 Bento4|GPL; see the file COPYING. If not, write to the
| Free Software Foundation, 59 Temple Place - Suite 330, Boston, MA
| 02111-1307, USA.
|
****************************************************************/
/*
Portions of this code are based on the code of LibTomCrypt
that was released into public domain by Tom St Denis.
*/
/*----------------------------------------------------------------------
| includes
+---------------------------------------------------------------------*/
#include "Ap4KeyWrap.h"
#include "Ap4AesBlockCipher.h"
#include "Ap4Utils.h"
/*----------------------------------------------------------------------
| constants
+---------------------------------------------------------------------*/
/*----------------------------------------------------------------------
| AP4_AesKeyWrap
+---------------------------------------------------------------------*/
AP4_Result
AP4_AesKeyWrap(const AP4_UI08* kek,
const AP4_UI08* cleartext_key,
AP4_Size cleartext_key_size,
AP4_DataBuffer& wrapped_key)
{
// check parameters
if (cleartext_key_size % 8) {
// not a multiple of 64 bits
return AP4_ERROR_INVALID_PARAMETERS;
}
// the output size is (n+1)*64 bits
// where n is the number of 64-bit blocks
// of the cleartext key
unsigned int n = cleartext_key_size/8;
wrapped_key.SetDataSize((n+1)*8);
// Step 1. Initialize variables.
// Set A = IV, an initial value (0xA6)
// For i = 1 to n
// R[i] = P[i]
AP4_UI08* a = (AP4_UI08*)wrapped_key.UseData();
AP4_SetMemory(a, 0xA6, 8);
AP4_UI08* r = a+8;
AP4_CopyMemory(r, cleartext_key, cleartext_key_size);
// Step 2. Calculate intermediate values.
// For j = 0 to 5
// For i=1 to n
// B = AES(K, A | R[i])
// A = MSB(64, B) ^ t where t = (n*j)+i
// R[i] = LSB(64, B)
AP4_AesBlockCipher* block_cipher = NULL;
AP4_Result result = AP4_AesBlockCipher::Create(kek,
AP4_BlockCipher::ENCRYPT,
AP4_BlockCipher::CBC,
NULL,
block_cipher);
if (AP4_FAILED(result)) return result;
for (unsigned int j=0; j <= 5; j++) {
r = a + 8;
for (unsigned int i=1; i<=n; i++) {
AP4_UI08 workspace[16];
AP4_UI08 b[16];
AP4_CopyMemory(workspace, a, 8);
AP4_CopyMemory(&workspace[8], r, 8);
block_cipher->Process(workspace, 16, b, NULL);
AP4_CopyMemory(a, b, 8);
a[7] ^= n*j+i;
AP4_CopyMemory(r, &b[8], 8);
r += 8;
}
}
delete block_cipher;
// Step 3. Output the results.
// (Nothing to do here since we've worked in-place
return AP4_SUCCESS;
}
/*----------------------------------------------------------------------
| AP4_AesKeyUnwrap
+---------------------------------------------------------------------*/
AP4_Result
AP4_AesKeyUnwrap(const AP4_UI08* kek,
const AP4_UI08* wrapped_key,
AP4_Size wrapped_key_size,
AP4_DataBuffer& cleartext_key)
{
// check parameters
if ((wrapped_key_size % 8) || (wrapped_key_size < 24)) {
// not a multiple of 64 bits or too small
return AP4_ERROR_INVALID_PARAMETERS;
}
// setup the output buffer
unsigned int n = (wrapped_key_size/8)-1;
cleartext_key.SetDataSize(n*8);
// Step 1. Initialize variables.
// Set A = C[0]
// For i = 1 to n
// R[i] = C[i]
AP4_UI08 a[8];
AP4_CopyMemory(a, wrapped_key, 8);
AP4_UI08* r = (AP4_UI08*)cleartext_key.UseData();
AP4_CopyMemory(r, wrapped_key+8, 8*n);
// Step 2. Compute intermediate values.
// For j = 5 to 0
// For i = n to 1
// B = AES-1(K, (A ^ t) | R[i]) where t = n*j+i
// A = MSB(64, B)
// R[i] = LSB(64, B)
AP4_AesBlockCipher* block_cipher = NULL;
AP4_Result result = AP4_AesBlockCipher::Create(kek,
AP4_BlockCipher::DECRYPT,
AP4_BlockCipher::CBC,
NULL,
block_cipher);
if (AP4_FAILED(result)) return result;
for (int j=5; j>=0; j--) {
r = (AP4_UI08*)cleartext_key.UseData()+(n-1)*8;
for (int i=n; i>=1; i--) {
AP4_UI08 workspace[16];
AP4_UI08 b[16];
AP4_CopyMemory(workspace, a, 8);
workspace[7] ^= (n*j)+i;
AP4_CopyMemory(&workspace[8], r, 8);
block_cipher->Process(workspace, 16, b, NULL);
AP4_CopyMemory(a, b, 8);
AP4_CopyMemory(r, &b[8], 8);
r -= 8;
}
}
delete block_cipher;
// Step 3. Output results.
// If A is an appropriate initial value (see 2.2.3),
// Then
// For i = 1 to n
// P[i] = R[i]
// Else
// Return an error
for (unsigned int i=0; i<8; i++) {
if (a[i] != 0xA6) {
cleartext_key.SetDataSize(0);
return AP4_ERROR_INVALID_FORMAT;
}
}
return AP4_SUCCESS;
}
|
