1. //+CXXFLAGS:=-O2 -g -Wall -Wextra -Wshadow -std=c++11
  2. #include <string>
  3. #include <iostream>
  4. #include <algorithm>
  6. #include <stdint.h>
  7. #include <stdio.h>
  8. #include <openssl/sha.h>
  10. using namespace std;
  12. std::string calculate_flag(
  13. std::string &part1,
  14. int64_t part2,
  15. std::string &part4,
  16. uint64_t factor1,
  17. uint64_t factor2)
  18. {
  20. std::transform(part1.begin(), part1.end(), part1.begin(), ::tolower);
  21. std::transform(part4.begin(), part4.end(), part4.begin(), ::tolower);
  23. SHA_CTX ctx;
  24. SHA1_Init(&ctx);
  26. unsigned int mod = factor1 % factor2;
  27. for (unsigned int i = 0; i < mod; i+=2)
  28. {
  29. SHA1_Update(&ctx,
  30. reinterpret_cast<const unsigned char *>(part1.c_str()),
  31. part1.size());
  32. }
  35. while (part2-- > 0)
  36. {
  37. SHA1_Update(&ctx,
  38. reinterpret_cast<const unsigned char *>(part4.c_str()),
  39. part1.size());
  40. }
  42. unsigned char *hash = new unsigned char[SHA_DIGEST_LENGTH];
  43. SHA1_Final(hash, &ctx);
  45. std::string rv;
  46. for (unsigned int i = 0; i < SHA_DIGEST_LENGTH; i++)
  47. {
  48. char *buf;
  49. asprintf(&buf, "%02x", hash[i]);
  50. rv += buf;
  51. free(buf);
  52. }
  53. return rv;
  54. }
  56. int main(int argc, char **argv)
  57. {
  58. (void)argc; (void)argv; //unused
  59. string part1;
  60. cout << "Part1: Enter flag:" << endl;
  61. cin >> part1;
  63. int64_t part2;
  64. cout << "Part2: Input 51337:" << endl;
  65. cin >> part2;
  67. std::string part3;
  68. cout << "Part3: Watch this: https://www.youtube.com/watch?v=PBwAxmrE194" << endl;
  69. cin >> part3;
  71. std::string part4;
  72. cout << "Part4: C.R.E.A.M. Get da _____: " << endl;
  73. cin >> part4;
  75. uint64_t first, second;
  76. cout << "Part5: Input the two prime factors of the number 270031727027." << endl;
  77. cin >> first;
  78. cin >> second;
  80. uint64_t factor1, factor2;
  81. if (first < second)
  82. {
  83. factor1 = first;
  84. factor2 = second;
  85. }
  86. else
  87. {
  88. factor1 = second;
  89. factor2 = first;
  90. }
  92. std::string flag = calculate_flag(part1, part2, part4, factor1, factor2);
  93. cout << "flag{";
  94. cout << flag;
  95. cout << "}" << endl;
  97. return 0;
  98. }

CSAW2015 - for400 sharp.cpp