Mercurial > dropbear
view libtomcrypt/src/modes/xts/xts_decrypt.c @ 1772:0cc85b4a4abb
Move fuzzer-kex initialisation into a constructor function
Hopefully this can avoid hitting AFL timeouts
https://github.com/google/oss-fuzz/pull/2474
author | Matt Johnston <matt@ucc.asn.au> |
---|---|
date | Thu, 29 Oct 2020 23:00:52 +0800 |
parents | 6dba84798cd5 |
children |
line wrap: on
line source
/* LibTomCrypt, modular cryptographic library -- Tom St Denis * * LibTomCrypt is a library that provides various cryptographic * algorithms in a highly modular and flexible manner. * * The library is free for all purposes without any express * guarantee it works. */ #include "tomcrypt.h" /** Source donated by Elliptic Semiconductor Inc (www.ellipticsemi.com) to the LibTom Projects */ #ifdef LTC_XTS_MODE static int _tweak_uncrypt(const unsigned char *C, unsigned char *P, unsigned char *T, symmetric_xts *xts) { unsigned long x; int err; /* tweak encrypt block i */ #ifdef LTC_FAST for (x = 0; x < 16; x += sizeof(LTC_FAST_TYPE)) { *(LTC_FAST_TYPE_PTR_CAST(&P[x])) = *(LTC_FAST_TYPE_PTR_CAST(&C[x])) ^ *(LTC_FAST_TYPE_PTR_CAST(&T[x])); } #else for (x = 0; x < 16; x++) { P[x] = C[x] ^ T[x]; } #endif err = cipher_descriptor[xts->cipher].ecb_decrypt(P, P, &xts->key1); #ifdef LTC_FAST for (x = 0; x < 16; x += sizeof(LTC_FAST_TYPE)) { *(LTC_FAST_TYPE_PTR_CAST(&P[x])) ^= *(LTC_FAST_TYPE_PTR_CAST(&T[x])); } #else for (x = 0; x < 16; x++) { P[x] = P[x] ^ T[x]; } #endif /* LFSR the tweak */ xts_mult_x(T); return err; } /** XTS Decryption @param ct [in] Ciphertext @param ptlen Length of plaintext (and ciphertext) @param pt [out] Plaintext @param tweak [in] The 128--bit encryption tweak (e.g. sector number) @param xts The XTS structure Returns CRYPT_OK upon success */ int xts_decrypt(const unsigned char *ct, unsigned long ptlen, unsigned char *pt, unsigned char *tweak, symmetric_xts *xts) { unsigned char PP[16], CC[16], T[16]; unsigned long i, m, mo, lim; int err; /* check inputs */ LTC_ARGCHK(pt != NULL); LTC_ARGCHK(ct != NULL); LTC_ARGCHK(tweak != NULL); LTC_ARGCHK(xts != NULL); /* check if valid */ if ((err = cipher_is_valid(xts->cipher)) != CRYPT_OK) { return err; } /* get number of blocks */ m = ptlen >> 4; mo = ptlen & 15; /* must have at least one full block */ if (m == 0) { return CRYPT_INVALID_ARG; } if (mo == 0) { lim = m; } else { lim = m - 1; } if (cipher_descriptor[xts->cipher].accel_xts_decrypt && lim > 0) { /* use accelerated decryption for whole blocks */ if ((err = cipher_descriptor[xts->cipher].accel_xts_decrypt(ct, pt, lim, tweak, &xts->key1, &xts->key2)) != CRYPT_OK) { return err; } ct += lim * 16; pt += lim * 16; /* tweak is encrypted on output */ XMEMCPY(T, tweak, sizeof(T)); } else { /* encrypt the tweak */ if ((err = cipher_descriptor[xts->cipher].ecb_encrypt(tweak, T, &xts->key2)) != CRYPT_OK) { return err; } for (i = 0; i < lim; i++) { if ((err = _tweak_uncrypt(ct, pt, T, xts)) != CRYPT_OK) { return err; } ct += 16; pt += 16; } } /* if ptlen not divide 16 then */ if (mo > 0) { XMEMCPY(CC, T, 16); xts_mult_x(CC); /* PP = tweak decrypt block m-1 */ if ((err = _tweak_uncrypt(ct, PP, CC, xts)) != CRYPT_OK) { return err; } /* Pm = first ptlen % 16 bytes of PP */ for (i = 0; i < mo; i++) { CC[i] = ct[16 + i]; pt[16 + i] = PP[i]; } for (; i < 16; i++) { CC[i] = PP[i]; } /* Pm-1 = Tweak uncrypt CC */ if ((err = _tweak_uncrypt(CC, pt, T, xts)) != CRYPT_OK) { return err; } } /* Decrypt the tweak back */ if ((err = cipher_descriptor[xts->cipher].ecb_decrypt(T, tweak, &xts->key2)) != CRYPT_OK) { return err; } return CRYPT_OK; } #endif /* ref: $Format:%D$ */ /* git commit: $Format:%H$ */ /* commit time: $Format:%ai$ */