mirror of
https://github.com/bol-van/zapret2.git
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78 lines
1.9 KiB
C
78 lines
1.9 KiB
C
#include "aes-ctr.h"
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#include <string.h>
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#define AES_BLOCKLEN 16
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// add 64-bit value to 16-byte big endian counter
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#if defined(__GNUC__) && !defined(__llvm__)
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__attribute__((optimize ("no-strict-aliasing")))
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#endif
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void ctr_add(uint8_t *counter, uint64_t add)
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{
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#ifndef __BYTE_ORDER__
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#error "__BYTE_ORDER__ not defined"
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#endif
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uint64_t *c = (uint64_t*)counter;
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#if __BYTE_ORDER__==__ORDER_BIG_ENDIAN__
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uint64_t sum = c[1] + add;
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if (sum < c[1]) // overflow
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c[0]++;
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c[1] = sum;
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#else
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uint64_t lsw = __builtin_bswap64(c[1]);
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uint64_t sum = lsw + add;
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if (sum < lsw) // overflow
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c[0] = __builtin_bswap64(__builtin_bswap64(c[0]) + 1);
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c[1] = __builtin_bswap64(sum);
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#endif
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}
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// increment 16-byte big endian counter
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static inline void ctr_increment(uint8_t *counter)
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{
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for (int8_t bi = (AES_BLOCKLEN - 1); (bi >= 0) && !++counter[bi]; bi--);
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}
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#if defined(__GNUC__) && !defined(__llvm__)
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__attribute__((optimize ("no-strict-aliasing")))
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#endif
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void aes_ctr_xcrypt_buffer(aes_context *ctx, const uint8_t *iv, const uint8_t *in, size_t length, uint8_t *out)
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{
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uint8_t bi, ivc[AES_BLOCKLEN], buffer[AES_BLOCKLEN];
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size_t i, l16 = length & ~0xF;
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memcpy(ivc, iv, AES_BLOCKLEN);
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for (i = 0; i < l16; i += 16)
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{
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aes_cipher(ctx, ivc, buffer);
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ctr_increment(ivc);
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*((uint64_t*)(out + i)) = *((uint64_t*)(in + i)) ^ ((uint64_t*)buffer)[0];
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*((uint64_t*)(out + i + 8)) = *((uint64_t*)(in + i + 8)) ^ ((uint64_t*)buffer)[1];
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}
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if (i<length)
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{
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memcpy(buffer, ivc, AES_BLOCKLEN);
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aes_cipher(ctx, buffer, buffer);
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for (bi=0 ; i < length; i++, bi++)
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out[i] = in[i] ^ buffer[bi];
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}
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}
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int aes_ctr_crypt(const uint8_t *key, unsigned int key_len, const uint8_t *iv, const uint8_t *in, size_t length, uint8_t *out)
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{
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int ret = 0;
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aes_context ctx;
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aes_init_keygen_tables();
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if (!(ret = aes_setkey(&ctx, AES_ENCRYPT, key, key_len)))
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aes_ctr_xcrypt_buffer(&ctx, iv, in, length, out);
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return ret;
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}
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