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171
thirdparty/libtomcrypt/pk/pkcs1/pkcs_1_oaep_encode.c
vendored
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171
thirdparty/libtomcrypt/pk/pkcs1/pkcs_1_oaep_encode.c
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/* 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 pkcs_1_oaep_encode.c
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OAEP Padding for PKCS #1, Tom St Denis
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*/
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#ifdef LTC_PKCS_1
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/**
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PKCS #1 v2.00 OAEP encode
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@param msg The data to encode
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@param msglen The length of the data to encode (octets)
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@param lparam A session or system parameter (can be NULL)
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@param lparamlen The length of the lparam data
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@param modulus_bitlen The bit length of the RSA modulus
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@param prng An active PRNG state
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@param prng_idx The index of the PRNG desired
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@param hash_idx The index of the hash desired
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@param out [out] The destination for the encoded data
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@param outlen [in/out] The max size and resulting size of the encoded data
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@return CRYPT_OK if successful
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*/
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int pkcs_1_oaep_encode(const unsigned char *msg, unsigned long msglen,
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const unsigned char *lparam, unsigned long lparamlen,
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unsigned long modulus_bitlen, prng_state *prng,
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int prng_idx, int hash_idx,
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unsigned char *out, unsigned long *outlen)
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{
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unsigned char *DB, *seed, *mask;
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unsigned long hLen, x, y, modulus_len;
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int err;
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LTC_ARGCHK(msg != NULL);
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LTC_ARGCHK(out != NULL);
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LTC_ARGCHK(outlen != NULL);
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/* test 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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/* valid prng */
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if ((err = prng_is_valid(prng_idx)) != CRYPT_OK) {
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return err;
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}
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hLen = hash_descriptor[hash_idx].hashsize;
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modulus_len = (modulus_bitlen >> 3) + (modulus_bitlen & 7 ? 1 : 0);
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/* test message size */
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if ((2*hLen >= (modulus_len - 2)) || (msglen > (modulus_len - 2*hLen - 2))) {
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return CRYPT_PK_INVALID_SIZE;
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}
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/* allocate ram for DB/mask/salt of size modulus_len */
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DB = XMALLOC(modulus_len);
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mask = XMALLOC(modulus_len);
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seed = XMALLOC(hLen);
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if (DB == NULL || mask == NULL || seed == NULL) {
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if (DB != NULL) {
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XFREE(DB);
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}
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if (mask != NULL) {
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XFREE(mask);
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}
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if (seed != NULL) {
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XFREE(seed);
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}
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return CRYPT_MEM;
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}
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/* get lhash */
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/* DB == lhash || PS || 0x01 || M, PS == k - mlen - 2hlen - 2 zeroes */
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x = modulus_len;
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if (lparam != NULL) {
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if ((err = hash_memory(hash_idx, lparam, lparamlen, DB, &x)) != CRYPT_OK) {
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goto LBL_ERR;
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}
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} else {
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/* can't pass hash_memory a NULL so use DB with zero length */
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if ((err = hash_memory(hash_idx, DB, 0, DB, &x)) != CRYPT_OK) {
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goto LBL_ERR;
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}
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}
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/* append PS then 0x01 (to lhash) */
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x = hLen;
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y = modulus_len - msglen - 2*hLen - 2;
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XMEMSET(DB+x, 0, y);
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x += y;
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/* 0x01 byte */
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DB[x++] = 0x01;
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/* message (length = msglen) */
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XMEMCPY(DB+x, msg, msglen);
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x += msglen;
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/* now choose a random seed */
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if (prng_descriptor[prng_idx].read(seed, hLen, prng) != hLen) {
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err = CRYPT_ERROR_READPRNG;
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goto LBL_ERR;
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}
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/* compute MGF1 of seed (k - hlen - 1) */
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if ((err = pkcs_1_mgf1(hash_idx, seed, hLen, mask, modulus_len - hLen - 1)) != CRYPT_OK) {
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goto LBL_ERR;
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}
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/* xor against DB */
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for (y = 0; y < (modulus_len - hLen - 1); y++) {
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DB[y] ^= mask[y];
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}
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/* compute MGF1 of maskedDB (hLen) */
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if ((err = pkcs_1_mgf1(hash_idx, DB, modulus_len - hLen - 1, mask, hLen)) != CRYPT_OK) {
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goto LBL_ERR;
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}
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/* XOR against seed */
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for (y = 0; y < hLen; y++) {
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seed[y] ^= mask[y];
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}
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/* create string of length modulus_len */
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if (*outlen < modulus_len) {
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*outlen = modulus_len;
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err = CRYPT_BUFFER_OVERFLOW;
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goto LBL_ERR;
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}
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/* start output which is 0x00 || maskedSeed || maskedDB */
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x = 0;
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out[x++] = 0x00;
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XMEMCPY(out+x, seed, hLen);
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x += hLen;
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XMEMCPY(out+x, DB, modulus_len - hLen - 1);
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x += modulus_len - hLen - 1;
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*outlen = x;
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err = CRYPT_OK;
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LBL_ERR:
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#ifdef LTC_CLEAN_STACK
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zeromem(DB, modulus_len);
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zeromem(seed, hLen);
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zeromem(mask, modulus_len);
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#endif
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XFREE(seed);
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XFREE(mask);
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XFREE(DB);
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return err;
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}
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#endif /* LTC_PKCS_1 */
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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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