Mercurial > dropbear
view libtomcrypt/src/encauth/ocb3/ocb3_decrypt_last.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 |
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/* 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. */ /** @file ocb3_decrypt_last.c OCB implementation, internal helper, by Karel Miko */ #include "tomcrypt.h" #ifdef LTC_OCB3_MODE /** Finish an OCB (decryption) stream @param ocb The OCB state @param ct The remaining ciphertext @param ctlen The length of the ciphertext (octets) @param pt [out] The output buffer @return CRYPT_OK if successful */ int ocb3_decrypt_last(ocb3_state *ocb, const unsigned char *ct, unsigned long ctlen, unsigned char *pt) { unsigned char iOffset_star[MAXBLOCKSIZE]; unsigned char iPad[MAXBLOCKSIZE]; int err, x, full_blocks, full_blocks_len, last_block_len; LTC_ARGCHK(ocb != NULL); if (ct == NULL) LTC_ARGCHK(ctlen == 0); if (ctlen != 0) { LTC_ARGCHK(ct != NULL); LTC_ARGCHK(pt != NULL); } if ((err = cipher_is_valid(ocb->cipher)) != CRYPT_OK) { goto LBL_ERR; } full_blocks = ctlen/ocb->block_len; full_blocks_len = full_blocks * ocb->block_len; last_block_len = ctlen - full_blocks_len; /* process full blocks first */ if (full_blocks>0) { if ((err = ocb3_decrypt(ocb, ct, full_blocks_len, pt)) != CRYPT_OK) { goto LBL_ERR; } } if (last_block_len>0) { /* Offset_* = Offset_m xor L_* */ ocb3_int_xor_blocks(iOffset_star, ocb->Offset_current, ocb->L_star, ocb->block_len); /* Pad = ENCIPHER(K, Offset_*) */ if ((err = cipher_descriptor[ocb->cipher].ecb_encrypt(iOffset_star, iPad, &ocb->key)) != CRYPT_OK) { goto LBL_ERR; } /* P_* = C_* xor Pad[1..bitlen(C_*)] */ ocb3_int_xor_blocks(pt+full_blocks_len, (unsigned char *)ct+full_blocks_len, iPad, last_block_len); /* Checksum_* = Checksum_m xor (P_* || 1 || zeros(127-bitlen(P_*))) */ ocb3_int_xor_blocks(ocb->checksum, ocb->checksum, pt+full_blocks_len, last_block_len); for(x=last_block_len; x<ocb->block_len; x++) { if (x == last_block_len) ocb->checksum[x] ^= 0x80; else ocb->checksum[x] ^= 0x00; } /* Tag = ENCIPHER(K, Checksum_* xor Offset_* xor L_$) xor HASH(K,A) */ /* at this point we calculate only: Tag_part = ENCIPHER(K, Checksum_* xor Offset_* xor L_$) */ for(x=0; x<ocb->block_len; x++) { ocb->tag_part[x] = (ocb->checksum[x] ^ iOffset_star[x]) ^ ocb->L_dollar[x]; } if ((err = cipher_descriptor[ocb->cipher].ecb_encrypt(ocb->tag_part, ocb->tag_part, &ocb->key)) != CRYPT_OK) { goto LBL_ERR; } } else { /* Tag = ENCIPHER(K, Checksum_m xor Offset_m xor L_$) xor HASH(K,A) */ /* at this point we calculate only: Tag_part = ENCIPHER(K, Checksum_m xor Offset_m xor L_$) */ for(x=0; x<ocb->block_len; x++) { ocb->tag_part[x] = (ocb->checksum[x] ^ ocb->Offset_current[x]) ^ ocb->L_dollar[x]; } if ((err = cipher_descriptor[ocb->cipher].ecb_encrypt(ocb->tag_part, ocb->tag_part, &ocb->key)) != CRYPT_OK) { goto LBL_ERR; } } err = CRYPT_OK; LBL_ERR: #ifdef LTC_CLEAN_STACK zeromem(iOffset_star, MAXBLOCKSIZE); zeromem(iPad, MAXBLOCKSIZE); #endif return err; } #endif /* ref: $Format:%D$ */ /* git commit: $Format:%H$ */ /* commit time: $Format:%ai$ */