| 1 | /*
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| 2 | * Copyright 2015-2018 The OpenSSL Project Authors. All Rights Reserved.
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| 3 | *
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| 4 | * Licensed under the OpenSSL license (the "License"). You may not use
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| 5 | * this file except in compliance with the License. You can obtain a copy
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| 6 | * in the file LICENSE in the source distribution or at
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| 7 | * https://www.openssl.org/source/license.html
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| 8 | */
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| 9 |
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| 10 | #include <string.h>
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| 11 | #include <openssl/ec.h>
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| 12 | #include <openssl/evp.h>
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| 13 | #include "ec_local.h"
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| 14 |
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| 15 | /* Key derivation function from X9.63/SECG */
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| 16 | /* Way more than we will ever need */
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| 17 | #define ECDH_KDF_MAX (1 << 30)
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| 18 |
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| 19 | int ecdh_KDF_X9_63(unsigned char *out, size_t outlen,
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| 20 | const unsigned char *Z, size_t Zlen,
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| 21 | const unsigned char *sinfo, size_t sinfolen,
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| 22 | const EVP_MD *md)
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| 23 | {
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| 24 | EVP_MD_CTX *mctx = NULL;
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| 25 | int rv = 0;
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| 26 | unsigned int i;
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| 27 | size_t mdlen;
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| 28 | unsigned char ctr[4];
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| 29 | if (sinfolen > ECDH_KDF_MAX || outlen > ECDH_KDF_MAX
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| 30 | || Zlen > ECDH_KDF_MAX)
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| 31 | return 0;
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| 32 | mctx = EVP_MD_CTX_new();
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| 33 | if (mctx == NULL)
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| 34 | return 0;
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| 35 | mdlen = EVP_MD_size(md);
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| 36 | for (i = 1;; i++) {
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| 37 | unsigned char mtmp[EVP_MAX_MD_SIZE];
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| 38 | if (!EVP_DigestInit_ex(mctx, md, NULL))
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| 39 | goto err;
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| 40 | ctr[3] = i & 0xFF;
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| 41 | ctr[2] = (i >> 8) & 0xFF;
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| 42 | ctr[1] = (i >> 16) & 0xFF;
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| 43 | ctr[0] = (i >> 24) & 0xFF;
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| 44 | if (!EVP_DigestUpdate(mctx, Z, Zlen))
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| 45 | goto err;
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| 46 | if (!EVP_DigestUpdate(mctx, ctr, sizeof(ctr)))
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| 47 | goto err;
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| 48 | if (!EVP_DigestUpdate(mctx, sinfo, sinfolen))
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| 49 | goto err;
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| 50 | if (outlen >= mdlen) {
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| 51 | if (!EVP_DigestFinal(mctx, out, NULL))
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| 52 | goto err;
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| 53 | outlen -= mdlen;
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| 54 | if (outlen == 0)
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| 55 | break;
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| 56 | out += mdlen;
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| 57 | } else {
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| 58 | if (!EVP_DigestFinal(mctx, mtmp, NULL))
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| 59 | goto err;
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| 60 | memcpy(out, mtmp, outlen);
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| 61 | OPENSSL_cleanse(mtmp, mdlen);
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| 62 | break;
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| 63 | }
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| 64 | }
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| 65 | rv = 1;
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| 66 | err:
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| 67 | EVP_MD_CTX_free(mctx);
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| 68 | return rv;
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| 69 | }
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| 70 |
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| 71 | /*-
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| 72 | * The old name for ecdh_KDF_X9_63
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| 73 | * Retained for ABI compatibility
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| 74 | */
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| 75 | int ECDH_KDF_X9_62(unsigned char *out, size_t outlen,
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| 76 | const unsigned char *Z, size_t Zlen,
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| 77 | const unsigned char *sinfo, size_t sinfolen,
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| 78 | const EVP_MD *md)
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| 79 | {
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| 80 | return ecdh_KDF_X9_63(out, outlen, Z, Zlen, sinfo, sinfolen, md);
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| 81 | }
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