| // SPDX-License-Identifier: BSD-2-Clause |
| /* 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_private.h" |
| |
| /** |
| @file cbc_decrypt.c |
| CBC implementation, encrypt block, Tom St Denis |
| */ |
| |
| |
| #ifdef LTC_CBC_MODE |
| |
| /** |
| CBC decrypt |
| @param ct Ciphertext |
| @param pt [out] Plaintext |
| @param len The number of bytes to process (must be multiple of block length) |
| @param cbc CBC state |
| @return CRYPT_OK if successful |
| */ |
| int cbc_decrypt(const unsigned char *ct, unsigned char *pt, unsigned long len, symmetric_CBC *cbc) |
| { |
| int x, err; |
| unsigned char tmp[16]; |
| #ifdef LTC_FAST |
| LTC_FAST_TYPE tmpy; |
| #else |
| unsigned char tmpy; |
| #endif |
| |
| LTC_ARGCHK(pt != NULL); |
| LTC_ARGCHK(ct != NULL); |
| LTC_ARGCHK(cbc != NULL); |
| |
| if ((err = cipher_is_valid(cbc->cipher)) != CRYPT_OK) { |
| return err; |
| } |
| |
| /* is blocklen valid? */ |
| if (cbc->blocklen < 1 || cbc->blocklen > (int)sizeof(cbc->IV) || cbc->blocklen > (int)sizeof(tmp)) { |
| return CRYPT_INVALID_ARG; |
| } |
| |
| if (len % cbc->blocklen) { |
| return CRYPT_INVALID_ARG; |
| } |
| #ifdef LTC_FAST |
| if (cbc->blocklen % sizeof(LTC_FAST_TYPE)) { |
| return CRYPT_INVALID_ARG; |
| } |
| #endif |
| |
| if (cipher_descriptor[cbc->cipher]->accel_cbc_decrypt != NULL) { |
| return cipher_descriptor[cbc->cipher]->accel_cbc_decrypt(ct, pt, len / cbc->blocklen, cbc->IV, &cbc->key); |
| } |
| while (len) { |
| /* decrypt */ |
| if ((err = cipher_descriptor[cbc->cipher]->ecb_decrypt(ct, tmp, &cbc->key)) != CRYPT_OK) { |
| return err; |
| } |
| |
| /* xor IV against plaintext */ |
| #if defined(LTC_FAST) |
| for (x = 0; x < cbc->blocklen; x += sizeof(LTC_FAST_TYPE)) { |
| tmpy = *(LTC_FAST_TYPE_PTR_CAST((unsigned char *)cbc->IV + x)) ^ *(LTC_FAST_TYPE_PTR_CAST((unsigned char *)tmp + x)); |
| *(LTC_FAST_TYPE_PTR_CAST((unsigned char *)cbc->IV + x)) = *(LTC_FAST_TYPE_PTR_CAST((unsigned char *)ct + x)); |
| *(LTC_FAST_TYPE_PTR_CAST((unsigned char *)pt + x)) = tmpy; |
| } |
| #else |
| for (x = 0; x < cbc->blocklen; x++) { |
| tmpy = tmp[x] ^ cbc->IV[x]; |
| cbc->IV[x] = ct[x]; |
| pt[x] = tmpy; |
| } |
| #endif |
| |
| ct += cbc->blocklen; |
| pt += cbc->blocklen; |
| len -= cbc->blocklen; |
| } |
| return CRYPT_OK; |
| } |
| |
| #endif |
| |
| /* ref: $Format:%D$ */ |
| /* git commit: $Format:%H$ */ |
| /* commit time: $Format:%ai$ */ |