aes_ctr.c 4.9 KB

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  1. /* crypto/aes/aes_ctr.c -*- mode:C; c-file-style: "eay" -*- */
  2. /* ====================================================================
  3. * Copyright (c) 1998-2002 The OpenSSL Project. All rights reserved.
  4. *
  5. * Redistribution and use in source and binary forms, with or without
  6. * modification, are permitted provided that the following conditions
  7. * are met:
  8. *
  9. * 1. Redistributions of source code must retain the above copyright
  10. * notice, this list of conditions and the following disclaimer.
  11. *
  12. * 2. Redistributions in binary form must reproduce the above copyright
  13. * notice, this list of conditions and the following disclaimer in
  14. * the documentation and/or other materials provided with the
  15. * distribution.
  16. *
  17. * 3. All advertising materials mentioning features or use of this
  18. * software must display the following acknowledgment:
  19. * "This product includes software developed by the OpenSSL Project
  20. * for use in the OpenSSL Toolkit. (http://www.openssl.org/)"
  21. *
  22. * 4. The names "OpenSSL Toolkit" and "OpenSSL Project" must not be used to
  23. * endorse or promote products derived from this software without
  24. * prior written permission. For written permission, please contact
  25. * openssl-core@openssl.org.
  26. *
  27. * 5. Products derived from this software may not be called "OpenSSL"
  28. * nor may "OpenSSL" appear in their names without prior written
  29. * permission of the OpenSSL Project.
  30. *
  31. * 6. Redistributions of any form whatsoever must retain the following
  32. * acknowledgment:
  33. * "This product includes software developed by the OpenSSL Project
  34. * for use in the OpenSSL Toolkit (http://www.openssl.org/)"
  35. *
  36. * THIS SOFTWARE IS PROVIDED BY THE OpenSSL PROJECT ``AS IS'' AND ANY
  37. * EXPRESSED OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  38. * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
  39. * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE OpenSSL PROJECT OR
  40. * ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
  41. * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
  42. * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
  43. * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  44. * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
  45. * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
  46. * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
  47. * OF THE POSSIBILITY OF SUCH DAMAGE.
  48. * ====================================================================
  49. *
  50. */
  51. #ifndef AES_DEBUG
  52. # ifndef NDEBUG
  53. # define NDEBUG
  54. # endif
  55. #endif
  56. #include <assert.h>
  57. #include <openssl/aes.h>
  58. #include "aes_locl.h"
  59. /*
  60. * NOTE: the IV/counter CTR mode is big-endian. The rest of the AES code is
  61. * endian-neutral.
  62. */
  63. /* increment counter (128-bit int) by 1 */
  64. static void AES_ctr128_inc(unsigned char *counter)
  65. {
  66. unsigned long c;
  67. /* Grab bottom dword of counter and increment */
  68. c = GETU32(counter + 12);
  69. c++;
  70. c &= 0xFFFFFFFF;
  71. PUTU32(counter + 12, c);
  72. /* if no overflow, we're done */
  73. if (c)
  74. return;
  75. /* Grab 1st dword of counter and increment */
  76. c = GETU32(counter + 8);
  77. c++;
  78. c &= 0xFFFFFFFF;
  79. PUTU32(counter + 8, c);
  80. /* if no overflow, we're done */
  81. if (c)
  82. return;
  83. /* Grab 2nd dword of counter and increment */
  84. c = GETU32(counter + 4);
  85. c++;
  86. c &= 0xFFFFFFFF;
  87. PUTU32(counter + 4, c);
  88. /* if no overflow, we're done */
  89. if (c)
  90. return;
  91. /* Grab top dword of counter and increment */
  92. c = GETU32(counter + 0);
  93. c++;
  94. c &= 0xFFFFFFFF;
  95. PUTU32(counter + 0, c);
  96. }
  97. /*
  98. * The input encrypted as though 128bit counter mode is being used. The
  99. * extra state information to record how much of the 128bit block we have
  100. * used is contained in *num, and the encrypted counter is kept in
  101. * ecount_buf. Both *num and ecount_buf must be initialised with zeros
  102. * before the first call to AES_ctr128_encrypt(). This algorithm assumes
  103. * that the counter is in the x lower bits of the IV (ivec), and that the
  104. * application has full control over overflow and the rest of the IV. This
  105. * implementation takes NO responsability for checking that the counter
  106. * doesn't overflow into the rest of the IV when incremented.
  107. */
  108. void AES_ctr128_encrypt(const unsigned char *in, unsigned char *out,
  109. const unsigned long length, const AES_KEY *key,
  110. unsigned char ivec[AES_BLOCK_SIZE],
  111. unsigned char ecount_buf[AES_BLOCK_SIZE],
  112. unsigned int *num)
  113. {
  114. unsigned int n;
  115. unsigned long l = length;
  116. assert(in && out && key && counter && num);
  117. assert(*num < AES_BLOCK_SIZE);
  118. n = *num;
  119. while (l--) {
  120. if (n == 0) {
  121. AES_encrypt(ivec, ecount_buf, key);
  122. AES_ctr128_inc(ivec);
  123. }
  124. *(out++) = *(in++) ^ ecount_buf[n];
  125. n = (n + 1) % AES_BLOCK_SIZE;
  126. }
  127. *num = n;
  128. }