aes_ctr.c 4.6 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. /* NOTE: the IV/counter CTR mode is big-endian. The rest of the AES code
  60. * is endian-neutral. */
  61. /* increment counter (128-bit int) by 1 */
  62. static void AES_ctr128_inc(unsigned char *counter) {
  63. unsigned long c;
  64. /* Grab bottom dword of counter and increment */
  65. c = GETU32(counter + 12);
  66. c++; c &= 0xFFFFFFFF;
  67. PUTU32(counter + 12, c);
  68. /* if no overflow, we're done */
  69. if (c)
  70. return;
  71. /* Grab 1st dword of counter and increment */
  72. c = GETU32(counter + 8);
  73. c++; c &= 0xFFFFFFFF;
  74. PUTU32(counter + 8, c);
  75. /* if no overflow, we're done */
  76. if (c)
  77. return;
  78. /* Grab 2nd dword of counter and increment */
  79. c = GETU32(counter + 4);
  80. c++; c &= 0xFFFFFFFF;
  81. PUTU32(counter + 4, c);
  82. /* if no overflow, we're done */
  83. if (c)
  84. return;
  85. /* Grab top dword of counter and increment */
  86. c = GETU32(counter + 0);
  87. c++; c &= 0xFFFFFFFF;
  88. PUTU32(counter + 0, c);
  89. }
  90. /* The input encrypted as though 128bit counter mode is being
  91. * used. The extra state information to record how much of the
  92. * 128bit block we have used is contained in *num, and the
  93. * encrypted counter is kept in ecount_buf. Both *num and
  94. * ecount_buf must be initialised with zeros before the first
  95. * call to AES_ctr128_encrypt().
  96. *
  97. * This algorithm assumes that the counter is in the x lower bits
  98. * of the IV (ivec), and that the application has full control over
  99. * overflow and the rest of the IV. This implementation takes NO
  100. * responsability for checking that the counter doesn't overflow
  101. * into the rest of the IV when incremented.
  102. */
  103. void AES_ctr128_encrypt(const unsigned char *in, unsigned char *out,
  104. const unsigned long length, const AES_KEY *key,
  105. unsigned char ivec[AES_BLOCK_SIZE],
  106. unsigned char ecount_buf[AES_BLOCK_SIZE],
  107. unsigned int *num) {
  108. unsigned int n;
  109. unsigned long l=length;
  110. assert(in && out && key && counter && num);
  111. assert(*num < AES_BLOCK_SIZE);
  112. n = *num;
  113. while (l--) {
  114. if (n == 0) {
  115. AES_encrypt(ivec, ecount_buf, key);
  116. AES_ctr128_inc(ivec);
  117. }
  118. *(out++) = *(in++) ^ ecount_buf[n];
  119. n = (n+1) % AES_BLOCK_SIZE;
  120. }
  121. *num=n;
  122. }