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68 lines
2.0 KiB
C
68 lines
2.0 KiB
C
/*
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* Copyright 2015-2016 The OpenSSL Project Authors. All Rights Reserved.
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*
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* Licensed under the OpenSSL license (the "License"). You may not use
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* this file except in compliance with the License. You can obtain a copy
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* in the file LICENSE in the source distribution or at
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* https://www.openssl.org/source/license.html
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*/
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#include <string.h>
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#include <openssl/ec.h>
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#include <openssl/evp.h>
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/* Key derivation function from X9.62/SECG */
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/* Way more than we will ever need */
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#define ECDH_KDF_MAX (1 << 30)
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int ECDH_KDF_X9_62(unsigned char *out, size_t outlen,
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const unsigned char *Z, size_t Zlen,
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const unsigned char *sinfo, size_t sinfolen,
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const EVP_MD *md)
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{
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EVP_MD_CTX *mctx = NULL;
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int rv = 0;
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unsigned int i;
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size_t mdlen;
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unsigned char ctr[4];
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if (sinfolen > ECDH_KDF_MAX || outlen > ECDH_KDF_MAX
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|| Zlen > ECDH_KDF_MAX)
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return 0;
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mctx = EVP_MD_CTX_new();
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if (mctx == NULL)
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return 0;
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mdlen = EVP_MD_size(md);
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for (i = 1;; i++) {
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unsigned char mtmp[EVP_MAX_MD_SIZE];
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EVP_DigestInit_ex(mctx, md, NULL);
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ctr[3] = i & 0xFF;
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ctr[2] = (i >> 8) & 0xFF;
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ctr[1] = (i >> 16) & 0xFF;
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ctr[0] = (i >> 24) & 0xFF;
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if (!EVP_DigestUpdate(mctx, Z, Zlen))
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goto err;
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if (!EVP_DigestUpdate(mctx, ctr, sizeof(ctr)))
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goto err;
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if (!EVP_DigestUpdate(mctx, sinfo, sinfolen))
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goto err;
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if (outlen >= mdlen) {
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if (!EVP_DigestFinal(mctx, out, NULL))
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goto err;
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outlen -= mdlen;
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if (outlen == 0)
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break;
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out += mdlen;
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} else {
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if (!EVP_DigestFinal(mctx, mtmp, NULL))
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goto err;
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memcpy(out, mtmp, outlen);
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OPENSSL_cleanse(mtmp, mdlen);
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break;
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}
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}
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rv = 1;
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err:
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EVP_MD_CTX_free(mctx);
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return rv;
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}
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