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104 lines
2.9 KiB
C
104 lines
2.9 KiB
C
/* LibTomCrypt, modular cryptographic library -- Tom St Denis
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*
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* LibTomCrypt is a library that provides various cryptographic
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* algorithms in a highly modular and flexible manner.
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*
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* The library is free for all purposes without any express
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* guarantee it works.
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*/
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#include "tomcrypt.h"
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/**
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@file katja_decrypt_key.c
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Katja PKCS #1 OAEP Decryption, Tom St Denis
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*/
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#ifdef LTC_MKAT
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/**
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(PKCS #1 v2.0) decrypt then OAEP depad
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@param in The ciphertext
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@param inlen The length of the ciphertext (octets)
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@param out [out] The plaintext
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@param outlen [in/out] The max size and resulting size of the plaintext (octets)
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@param lparam The system "lparam" value
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@param lparamlen The length of the lparam value (octets)
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@param hash_idx The index of the hash desired
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@param stat [out] Result of the decryption, 1==valid, 0==invalid
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@param key The corresponding private Katja key
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@return CRYPT_OK if succcessul (even if invalid)
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*/
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int katja_decrypt_key(const unsigned char *in, unsigned long inlen,
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unsigned char *out, unsigned long *outlen,
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const unsigned char *lparam, unsigned long lparamlen,
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int hash_idx, int *stat,
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katja_key *key)
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{
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unsigned long modulus_bitlen, modulus_bytelen, x;
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int err;
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unsigned char *tmp;
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LTC_ARGCHK(out != NULL);
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LTC_ARGCHK(outlen != NULL);
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LTC_ARGCHK(key != NULL);
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LTC_ARGCHK(stat != NULL);
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/* default to invalid */
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*stat = 0;
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/* valid hash ? */
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if ((err = hash_is_valid(hash_idx)) != CRYPT_OK) {
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return err;
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}
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/* get modulus len in bits */
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modulus_bitlen = mp_count_bits( (key->N));
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/* payload is upto pq, so we know q is 1/3rd the size of N and therefore pq is 2/3th the size */
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modulus_bitlen = ((modulus_bitlen << 1) / 3);
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/* round down to next byte */
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modulus_bitlen -= (modulus_bitlen & 7) + 8;
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/* outlen must be at least the size of the modulus */
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modulus_bytelen = mp_unsigned_bin_size( (key->N));
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if (modulus_bytelen != inlen) {
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return CRYPT_INVALID_PACKET;
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}
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/* allocate ram */
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tmp = XMALLOC(inlen);
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if (tmp == NULL) {
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return CRYPT_MEM;
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}
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/* rsa decode the packet */
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x = inlen;
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if ((err = katja_exptmod(in, inlen, tmp, &x, PK_PRIVATE, key)) != CRYPT_OK) {
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XFREE(tmp);
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return err;
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}
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/* shift right by modulus_bytelen - modulus_bitlen/8 bytes */
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for (x = 0; x < (modulus_bitlen >> 3); x++) {
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tmp[x] = tmp[x+(modulus_bytelen-(modulus_bitlen>>3))];
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}
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/* now OAEP decode the packet */
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err = pkcs_1_oaep_decode(tmp, x, lparam, lparamlen, modulus_bitlen, hash_idx,
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out, outlen, stat);
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XFREE(tmp);
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return err;
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}
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#endif /* LTC_MRSA */
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/* ref: HEAD -> master, tag: v1.18.2 */
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/* git commit: 7e7eb695d581782f04b24dc444cbfde86af59853 */
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/* commit time: 2018-07-01 22:49:01 +0200 */
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