72 lines
1.9 KiB
C
72 lines
1.9 KiB
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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* Tom St Denis, tomstdenis@iahu.ca, http://libtomcrypt.org
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*/
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#include "mycrypt.h"
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/* PKCS #1 v1.5 Signature Padding -- Tom St Denis */
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#ifdef PKCS_1
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int pkcs_1_v15_sa_encode(const unsigned char *msghash, unsigned long msghashlen,
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int hash_idx, unsigned long modulus_bitlen,
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unsigned char *out, unsigned long *outlen)
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{
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unsigned long derlen, modulus_bytelen, x, y;
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int err;
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_ARGCHK(msghash != NULL)
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_ARGCHK(out != NULL);
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_ARGCHK(outlen != NULL);
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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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/* hack, to detect any hash without a DER OID */
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if (hash_descriptor[hash_idx].DERlen == 0) {
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return CRYPT_INVALID_ARG;
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}
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/* get modulus len */
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modulus_bytelen = (modulus_bitlen>>3) + (modulus_bitlen & 7 ? 1 : 0);
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/* get der len ok? Forgive my lame German accent.... */
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derlen = hash_descriptor[hash_idx].DERlen;
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/* valid sizes? */
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if (msghashlen + 3 + derlen > modulus_bytelen) {
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return CRYPT_PK_INVALID_SIZE;
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}
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if (*outlen < modulus_bytelen) {
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return CRYPT_BUFFER_OVERFLOW;
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}
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/* packet is 0x00 0x01 PS 0x00 T, where PS == 0xFF repeated modulus_bytelen - 3 - derlen - msghashlen times, T == DER || hash */
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x = 0;
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out[x++] = 0x00;
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out[x++] = 0x01;
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for (y = 0; y < (modulus_bytelen - 3 - derlen - msghashlen); y++) {
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out[x++] = 0xFF;
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}
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out[x++] = 0x00;
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for (y = 0; y < derlen; y++) {
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out[x++] = hash_descriptor[hash_idx].DER[y];
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}
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for (y = 0; y < msghashlen; y++) {
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out[x++] = msghash[y];
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}
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*outlen = modulus_bytelen;
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return CRYPT_OK;
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}
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#endif /* PKCS_1 */
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