ecdh_kdf.c 4.1 KB

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  1. /* crypto/ec/ecdh_kdf.c */
  2. /*
  3. * Written by Stephen Henson for the OpenSSL project.
  4. */
  5. /* ====================================================================
  6. * Copyright (c) 2013 The OpenSSL Project. All rights reserved.
  7. *
  8. * Redistribution and use in source and binary forms, with or without
  9. * modification, are permitted provided that the following conditions
  10. * are met:
  11. *
  12. * 1. Redistributions of source code must retain the above copyright
  13. * notice, this list of conditions and the following disclaimer.
  14. *
  15. * 2. Redistributions in binary form must reproduce the above copyright
  16. * notice, this list of conditions and the following disclaimer in
  17. * the documentation and/or other materials provided with the
  18. * distribution.
  19. *
  20. * 3. All advertising materials mentioning features or use of this
  21. * software must display the following acknowledgment:
  22. * "This product includes software developed by the OpenSSL Project
  23. * for use in the OpenSSL Toolkit. (http://www.openssl.org/)"
  24. *
  25. * 4. The names "OpenSSL Toolkit" and "OpenSSL Project" must not be used to
  26. * endorse or promote products derived from this software without
  27. * prior written permission. For written permission, please contact
  28. * openssl-core@openssl.org.
  29. *
  30. * 5. Products derived from this software may not be called "OpenSSL"
  31. * nor may "OpenSSL" appear in their names without prior written
  32. * permission of the OpenSSL Project.
  33. *
  34. * 6. Redistributions of any form whatsoever must retain the following
  35. * acknowledgment:
  36. * "This product includes software developed by the OpenSSL Project
  37. * for use in the OpenSSL Toolkit (http://www.openssl.org/)"
  38. *
  39. * THIS SOFTWARE IS PROVIDED BY THE OpenSSL PROJECT ``AS IS'' AND ANY
  40. * EXPRESSED OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  41. * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
  42. * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE OpenSSL PROJECT OR
  43. * ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
  44. * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
  45. * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
  46. * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  47. * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
  48. * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
  49. * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
  50. * OF THE POSSIBILITY OF SUCH DAMAGE.
  51. * ====================================================================
  52. */
  53. #include <string.h>
  54. #include <openssl/ec.h>
  55. #include <openssl/evp.h>
  56. /* Key derivation function from X9.62/SECG */
  57. /* Way more than we will ever need */
  58. #define ECDH_KDF_MAX (1 << 30)
  59. int ECDH_KDF_X9_62(unsigned char *out, size_t outlen,
  60. const unsigned char *Z, size_t Zlen,
  61. const unsigned char *sinfo, size_t sinfolen,
  62. const EVP_MD *md)
  63. {
  64. EVP_MD_CTX *mctx = NULL;
  65. int rv = 0;
  66. unsigned int i;
  67. size_t mdlen;
  68. unsigned char ctr[4];
  69. if (sinfolen > ECDH_KDF_MAX || outlen > ECDH_KDF_MAX
  70. || Zlen > ECDH_KDF_MAX)
  71. return 0;
  72. mctx = EVP_MD_CTX_new();
  73. if (mctx == NULL)
  74. return 0;
  75. mdlen = EVP_MD_size(md);
  76. for (i = 1;; i++) {
  77. unsigned char mtmp[EVP_MAX_MD_SIZE];
  78. EVP_DigestInit_ex(mctx, md, NULL);
  79. ctr[3] = i & 0xFF;
  80. ctr[2] = (i >> 8) & 0xFF;
  81. ctr[1] = (i >> 16) & 0xFF;
  82. ctr[0] = (i >> 24) & 0xFF;
  83. if (!EVP_DigestUpdate(mctx, Z, Zlen))
  84. goto err;
  85. if (!EVP_DigestUpdate(mctx, ctr, sizeof(ctr)))
  86. goto err;
  87. if (!EVP_DigestUpdate(mctx, sinfo, sinfolen))
  88. goto err;
  89. if (outlen >= mdlen) {
  90. if (!EVP_DigestFinal(mctx, out, NULL))
  91. goto err;
  92. outlen -= mdlen;
  93. if (outlen == 0)
  94. break;
  95. out += mdlen;
  96. } else {
  97. if (!EVP_DigestFinal(mctx, mtmp, NULL))
  98. goto err;
  99. memcpy(out, mtmp, outlen);
  100. OPENSSL_cleanse(mtmp, mdlen);
  101. break;
  102. }
  103. }
  104. rv = 1;
  105. err:
  106. EVP_MD_CTX_free(mctx);
  107. return rv;
  108. }