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 /* * AES (Rijndael) cipher - decrypt * * Modifications to public domain implementation: * - cleanup * - use C pre-processor to make it easier to change S table access * - added option (AES_SMALL_TABLES) for reducing code size by about 8 kB at * cost of reduced throughput (quite small difference on Pentium 4, * 10-25% when using -O1 or -O2 optimization) * * Copyright (c) 2003-2012, Jouni Malinen * * This software may be distributed under the terms of the BSD license. * See README for more details. */ #include "includes.h" #include "common.h" #include "crypto.h" #include "aes_i.h" /** * Expand the cipher key into the decryption key schedule. * * @return the number of rounds for the given cipher key size. */ static int rijndaelKeySetupDec(u32 rk[], const u8 cipherKey[], int keyBits) { int Nr, i, j; u32 temp; /* expand the cipher key: */ Nr = rijndaelKeySetupEnc(rk, cipherKey, keyBits); if (Nr < 0) return Nr; /* invert the order of the round keys: */ for (i = 0, j = 4*Nr; i < j; i += 4, j -= 4) { temp = rk[i ]; rk[i ] = rk[j ]; rk[j ] = temp; temp = rk[i + 1]; rk[i + 1] = rk[j + 1]; rk[j + 1] = temp; temp = rk[i + 2]; rk[i + 2] = rk[j + 2]; rk[j + 2] = temp; temp = rk[i + 3]; rk[i + 3] = rk[j + 3]; rk[j + 3] = temp; } /* apply the inverse MixColumn transform to all round keys but the * first and the last: */ for (i = 1; i < Nr; i++) { rk += 4; for (j = 0; j < 4; j++) { rk[j] = TD0_(TE4((rk[j] >> 24) )) ^ TD1_(TE4((rk[j] >> 16) & 0xff)) ^ TD2_(TE4((rk[j] >> 8) & 0xff)) ^ TD3_(TE4((rk[j] ) & 0xff)); } } return Nr; } void * aes_decrypt_init(const u8 *key, size_t len) { u32 *rk; int res; rk = os_malloc(AES_PRIV_SIZE); if (rk == NULL) return NULL; res = rijndaelKeySetupDec(rk, key, len * 8); if (res < 0) { os_free(rk); return NULL; } rk[AES_PRIV_NR_POS] = res; return rk; } static void rijndaelDecrypt(const u32 rk[/*44*/], int Nr, const u8 ct[16], u8 pt[16]) { u32 s0, s1, s2, s3, t0, t1, t2, t3; #ifndef FULL_UNROLL int r; #endif /* ?FULL_UNROLL */ /* * map byte array block to cipher state * and add initial round key: */ s0 = GETU32(ct ) ^ rk[0]; s1 = GETU32(ct + 4) ^ rk[1]; s2 = GETU32(ct + 8) ^ rk[2]; s3 = GETU32(ct + 12) ^ rk[3]; #define ROUND(i,d,s) \ d##0 = TD0(s##0) ^ TD1(s##3) ^ TD2(s##2) ^ TD3(s##1) ^ rk[4 * i]; \ d##1 = TD0(s##1) ^ TD1(s##0) ^ TD2(s##3) ^ TD3(s##2) ^ rk[4 * i + 1]; \ d##2 = TD0(s##2) ^ TD1(s##1) ^ TD2(s##0) ^ TD3(s##3) ^ rk[4 * i + 2]; \ d##3 = TD0(s##3) ^ TD1(s##2) ^ TD2(s##1) ^ TD3(s##0) ^ rk[4 * i + 3] #ifdef FULL_UNROLL ROUND(1,t,s); ROUND(2,s,t); ROUND(3,t,s); ROUND(4,s,t); ROUND(5,t,s); ROUND(6,s,t); ROUND(7,t,s); ROUND(8,s,t); ROUND(9,t,s); if (Nr > 10) { ROUND(10,s,t); ROUND(11,t,s); if (Nr > 12) { ROUND(12,s,t); ROUND(13,t,s); } } rk += Nr << 2; #else /* !FULL_UNROLL */ /* Nr - 1 full rounds: */ r = Nr >> 1; for (;;) { ROUND(1,t,s); rk += 8; if (--r == 0) break; ROUND(0,s,t); } #endif /* ?FULL_UNROLL */ #undef ROUND /* * apply last round and * map cipher state to byte array block: */ s0 = TD41(t0) ^ TD42(t3) ^ TD43(t2) ^ TD44(t1) ^ rk[0]; PUTU32(pt , s0); s1 = TD41(t1) ^ TD42(t0) ^ TD43(t3) ^ TD44(t2) ^ rk[1]; PUTU32(pt + 4, s1); s2 = TD41(t2) ^ TD42(t1) ^ TD43(t0) ^ TD44(t3) ^ rk[2]; PUTU32(pt + 8, s2); s3 = TD41(t3) ^ TD42(t2) ^ TD43(t1) ^ TD44(t0) ^ rk[3]; PUTU32(pt + 12, s3); } void aes_decrypt(void *ctx, const u8 *crypt, u8 *plain) { u32 *rk = ctx; rijndaelDecrypt(ctx, rk[AES_PRIV_NR_POS], crypt, plain); } void aes_decrypt_deinit(void *ctx) { os_memset(ctx, 0, AES_PRIV_SIZE); os_free(ctx); }