mirror of
https://github.com/Scandal-UK/Incognito_RCM.git
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63 lines
1.6 KiB
C
63 lines
1.6 KiB
C
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/*
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* Copyright (c) 2012 by naehrwert
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* This file is released under the GPLv2.
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*/
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#include "../utils/types.h"
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#include "aes.h"
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#include "aes_xts.h"
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int aes_xts_init(aes_xts_ctxt_t *ctxt, int mode, const u8 *data_key, const u8 *tweak_key, int keybits) {
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ctxt->mode = mode;
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ctxt->keybits = keybits;
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aes_setkey_enc(&ctxt->twk_ctxt, tweak_key, keybits);
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if (mode == AES_ENCRYPT)
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aes_setkey_enc(&ctxt->aes_ctxt, data_key, keybits);
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else if (mode == AES_DECRYPT)
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aes_setkey_dec(&ctxt->aes_ctxt, data_key, keybits);
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else
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return -1;
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return 0;
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}
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int aes_xts_crypt(aes_xts_ctxt_t *ctxt, u64 seqno, u32 sector_size, const u8 *in, u8 *out) {
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u32 i = 0, j = 0;
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u8 tweak[0x10], buf[0x10];
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u8 carry_in, carry_out;
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//Check alignment.
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if (!(sector_size % 0x10 == 0))
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return -1;
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//Init tweak.
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((u64 *) tweak)[0] = seqno; //_ES64(seqno);
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((u64 *) tweak)[1] = 0;
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aes_crypt_ecb(&ctxt->twk_ctxt, AES_ENCRYPT, tweak, tweak);
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//En-/decrypt sector.
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for (i = 0; i < sector_size; i += 0x10) {
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for (j = 0; j < 0x10; j++)
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buf[j] = in[i + j] ^ tweak[j];
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//En-/decrypt 0x10 bytes.
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aes_crypt_ecb(&ctxt->aes_ctxt, ctxt->mode, buf, buf);
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for (j = 0; j < 0x10; j++)
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out[i + j] = buf[j] ^ tweak[j];
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//Update tweak (GF MUL).
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carry_in = 0;
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for (j = 0; j < 0x10; j++) {
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carry_out = (tweak[j] >> 7) & 1;
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tweak[j] = ((tweak[j] << 1) + carry_in) & 0xFF;
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carry_in = carry_out;
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}
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if (carry_out)
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tweak[0] ^= 0x87;
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}
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return 0;
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}
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