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pwnable.kr-balckjack-Writeup

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pwnable.kr-balckjack-Writeup

该题的代码奇长无比（788行）但题挺容易，并且比较有意思

首先从提供的网址https://cboard.cprogramming.com/c-programming/114023-simple-blackjack-program.html查看该题用到的代码如下：

  1 // Programmer: Vladislav Shulman
  2 // Final Project
  3 // Blackjack
  4  
  5 // Feel free to use any and all parts of this program and claim it as your own work
  6  
  7 //FINAL DRAFT
  8  
  9 #include <stdlib.h>
 10 #include <stdio.h>
 11 #include <math.h>
 12 #include <time.h>                //Used for srand((unsigned) time(NULL)) command
 13 #include <process.h>             //Used for system("cls") command
 14  
 15 #define spade 06                 //Used to print spade symbol
 16 #define club 05                  //Used to print club symbol
 17 #define diamond 04               //Used to print diamond symbol
 18 #define heart 03                 //Used to print heart symbol
 19 #define RESULTS "Blackjack.txt"  //File name is Blackjack
 20  
 21 //Global Variables
 22 int k;
 23 int l;
 24 int d;
 25 int won;
 26 int loss;
 27 int cash = 500;
 28 int bet;
 29 int random_card;
 30 int player_total=0;
 31 int dealer_total;
 32  
 33 //Function Prototypes
 34 int clubcard();      //Displays Club Card Image
 35 int diamondcard();   //Displays Diamond Card Image
 36 int heartcard();     //Displays Heart Card Image
 37 int spadecard();     //Displays Spade Card Image
 38 int randcard();      //Generates random card
 39 int betting();       //Asks user amount to bet
 40 void asktitle();     //Asks user to continue
 41 void rules();        //Prints "Rules of Vlad's Blackjack" menu
 42 void play();         //Plays game
 43 void dealer();       //Function to play for dealer AI
 44 void stay();         //Function for when user selects 'Stay'
 45 void cash_test();    //Test for if user has cash remaining in purse
 46 void askover();      //Asks if user wants to continue playing
 47 void fileresults();  //Prints results into Blackjack.txt file in program directory
 48  
 49 //Main Function
 50 int main(void)
 51 {
 52     int choice1;
 53     printf("
");
 54     printf("
");
 55     printf("
");
 56     printf("
              222                111                            ");
 57     printf("
            222 222            11111                              ");
 58     printf("
           222   222          11 111                            "); 
 59     printf("
                222              111                               "); 
 60     printf("
               222               111                           ");   
 61     printf("
");
 62     printf("
%c%c%c%c%c     %c%c            %c%c         %c%c%c%c%c    %c    %c                ", club, club, club, club, club, spade, spade, diamond, diamond, heart, heart, heart, heart, heart, club, club);  
 63     printf("
%c    %c    %c%c           %c  %c       %c     %c   %c   %c              ", club, club, spade, spade, diamond, diamond, heart, heart, club, club);            
 64     printf("
%c    %c    %c%c          %c    %c     %c          %c  %c               ", club, club, spade, spade, diamond, diamond, heart, club, club);                        
 65     printf("
%c%c%c%c%c     %c%c          %c %c%c %c     %c          %c %c              ", club, club, club, club, club, spade, spade, diamond, diamond, diamond, diamond, heart, club, club);      
 66     printf("
%c    %c    %c%c         %c %c%c%c%c %c    %c          %c%c %c             ", club, club, spade, spade, diamond, diamond, diamond, diamond, diamond, diamond, heart, club, club, club);                       
 67     printf("
%c     %c   %c%c         %c      %c    %c          %c   %c               ", club, club, spade, spade, diamond, diamond, heart, club, club);                                         
 68     printf("
%c     %c   %c%c        %c        %c    %c     %c   %c    %c             ", club, club, spade, spade, diamond, diamond, heart, heart, club, club);                                                            
 69     printf("
%c%c%c%c%c%c    %c%c%c%c%c%c%c   %c        %c     %c%c%c%c%c    %c     %c            ", club, club, club, club, club, club, spade, spade, spade, spade, spade, spade, spade, diamond, diamond, heart, heart, heart, heart, heart, club, club);                                                                                     
 70     printf("
");     
 71     printf("
                        21                                   ");
 72      
 73     printf("
     %c%c%c%c%c%c%c%c      %c%c         %c%c%c%c%c    %c    %c                ", diamond, diamond, diamond, diamond, diamond, diamond, diamond, diamond, heart, heart, club, club, club, club, club, spade, spade);                     
 74     printf("
        %c%c        %c  %c       %c     %c   %c   %c              ", diamond, diamond, heart, heart, club, club, spade, spade);                                      
 75     printf("
        %c%c       %c    %c     %c          %c  %c               ", diamond, diamond, heart, heart, club, spade, spade);                                           
 76     printf("
        %c%c       %c %c%c %c     %c          %c %c              ", diamond, diamond, heart, heart, heart, heart, club, spade, spade);                                     
 77     printf("
        %c%c      %c %c%c%c%c %c    %c          %c%c %c             ", diamond, diamond, heart, heart, heart, heart, heart, heart, club, spade, spade, spade);                                                
 78     printf("
        %c%c      %c      %c    %c          %c   %c               ", diamond, diamond, heart, heart, club, spade, spade);                                                                               
 79     printf("
     %c  %c%c     %c        %c    %c     %c   %c    %c             ", diamond, diamond, diamond, heart, heart, club, spade, spade);                                                                                                               
 80     printf("
      %c%c%c      %c        %c     %c%c%c%c%c    %c     %c            ", diamond, diamond, diamond, heart, heart, club, club, club, club, club, spade, spade);                                                                                                                                        
 81     printf("
");  
 82     printf("
         222                     111                         ");
 83     printf("
        222                      111                         ");
 84     printf("
       222                       111                         ");
 85     printf("
      222222222222222      111111111111111                       ");
 86     printf("
      2222222222222222    11111111111111111                         ");
 87     printf("
");
 88     printf("
");
 89      
 90     asktitle();
 91      
 92     printf("
");
 93     printf("
");
 94     system("pause");
 95     return(0);
 96 } //end program
 97  
 98 void asktitle() // Function for asking player if they want to continue
 99 {
100     char choice1;
101     int choice2;
102      
103      printf("
                 Are You Ready?");
104      printf("
                ----------------");
105      printf("
                      (Y/N)
                        ");
106      scanf("
%c",&choice1);
107  
108     while((choice1!='Y') && (choice1!='y') && (choice1!='N') && (choice1!='n')) // If invalid choice entered
109     {                                                                           
110         printf("
");
111         printf("Incorrect Choice. Please Enter Y for Yes or N for No.
");
112         scanf("%c",&choice1);
113     }
114  
115  
116     if((choice1 == 'Y') || (choice1 == 'y')) // If yes, continue. Prints menu.
117     { 
118             system("cls");
119             printf("
Enter 1 to Begin the Greatest Game Ever Played.");
120             printf("
Enter 2 to See a Complete Listing of Rules.");
121             printf("
Enter 3 to Exit Game. (Not Recommended)");
122             printf("
Choice: ");
123             scanf("%d", &choice2); // Prompts user for choice
124             if((choice2<1) || (choice2>3)) // If invalid choice entered
125             {
126                 printf("
Incorrect Choice. Please enter 1, 2 or 3
");
127                 scanf("%d", &choice2);
128             }
129             switch(choice2) // Switch case for different choices
130             {   
131                 case 1: // Case to begin game
132                    system("cls");
133                     
134                    play();
135                                        
136                    break;
137                     
138                 case 2: // Case to see rules
139                    system("cls");
140                    rules();
141                    break;
142                     
143                 case 3: // Case to exit game
144                    printf("
Your day could have been perfect.");
145                    printf("
Have an almost perfect day!

");
146                    system("pause");
147                    exit(0);
148                    break;
149                     
150                 default:
151                    printf("
Invalid Input");
152             } // End switch case
153     } // End if loop
154     
155              
156  
157     else if((choice1 == 'N') || (choice1 == 'n')) // If no, exit program
158     {
159         printf("
Your day could have been perfect.");
160         printf("
Have an almost perfect day!

");
161         system("pause");
162         exit(0);
163     }
164      
165     return;
166 } // End function
167  
168 void rules() //Prints "Rules of Vlad's Blackjack" list
169 {
170      char choice1;
171      int choice2;
172       
173      printf("
           RULES of VLAD's BLACKJACK");
174      printf("
          ---------------------------");
175      printf("
I.");
176      printf("
     Thou shalt not question the odds of this game.");
177      printf("
      %c This program generates cards at random.", spade);
178      printf("
      %c If you keep losing, you are very unlucky!
", diamond);
179       
180      printf("
II.");
181      printf("
     Each card has a value.");
182      printf("
      %c Number cards 1 to 10 hold a value of their number.", spade);
183      printf("
      %c J, Q, and K cards hold a value of 10.", diamond);
184      printf("
      %c Ace cards hold a value of 11", club);
185      printf("
     The goal of this game is to reach a card value total of 21.
");
186       
187      printf("
III.");
188      printf("
     After the dealing of the first two cards, YOU must decide whether to HIT or STAY.");
189      printf("
      %c Staying will keep you safe, hitting will add a card.", spade);
190      printf("
     Because you are competing against the dealer, you must beat his hand.");
191      printf("
     BUT BEWARE!.");
192      printf("
      %c If your total goes over 21, you will LOSE!.", diamond);
193      printf("
     But the world is not over, because you can always play again.
");
194      printf("
%c%c%c YOUR RESULTS ARE RECORDED AND FOUND IN SAME FOLDER AS PROGRAM %c%c%c
", spade, heart, club, club, heart, spade);
195      printf("
Would you like to go the previous screen? (I will not take NO for an answer)");
196      printf("
                  (Y/N)
                    ");
197      scanf("
%c",&choice1);
198       
199      while((choice1!='Y') && (choice1!='y') && (choice1!='N') && (choice1!='n')) // If invalid choice entered
200     {                                                                           
201         printf("
");
202         printf("Incorrect Choice. Please Enter Y for Yes or N for No.
");
203         scanf("%c",&choice1);
204     }
205  
206  
207     if((choice1 == 'Y') || (choice1 == 'y')) // If yes, continue. Prints menu.
208     { 
209             system("cls");
210             asktitle();
211     } // End if loop
212     
213              
214  
215     else if((choice1 == 'N') || (choice1 == 'n')) // If no, convinces user to enter yes
216     {
217         system("cls");
218         printf("
                 I told you so.
");
219         asktitle();
220     }
221      
222     return;
223 } // End function
224  
225 int clubcard() //Displays Club Card Image
226 {
227      
228      
229     srand((unsigned) time(NULL)); //Generates random seed for rand() function
230     k=rand()%13+1;
231      
232     if(k<=9) //If random number is 9 or less, print card with that number
233     {
234     //Club Card
235     printf("-------
");
236     printf("|%c    |
", club);
237     printf("|  %d  |
", k);
238     printf("|    %c|
", club);
239     printf("-------
");
240     }
241      
242      
243     if(k==10) //If random number is 10, print card with J (Jack) on face
244     {
245     //Club Card
246     printf("-------
");
247     printf("|%c    |
", club);
248     printf("|  J  |
");
249     printf("|    %c|
", club);
250     printf("-------
");
251     }
252      
253      
254     if(k==11) //If random number is 11, print card with A (Ace) on face
255     {
256     //Club Card
257     printf("-------
");
258     printf("|%c    |
", club);
259     printf("|  A  |
");
260     printf("|    %c|
", club);
261     printf("-------
");
262     if(player_total<=10) //If random number is Ace, change value to 11 or 1 depending on dealer total
263          {
264              k=11;
265          }
266           
267          else
268          {
269  
270              k=1;
271          }
272     }
273      
274      
275     if(k==12) //If random number is 12, print card with Q (Queen) on face
276     {
277     //Club Card
278     printf("-------
");
279     printf("|%c    |
", club);
280     printf("|  Q  |
");
281     printf("|    %c|
", club);
282     printf("-------
");
283     k=10; //Set card value to 10
284     }
285      
286      
287     if(k==13) //If random number is 13, print card with K (King) on face
288     {
289     //Club Card
290     printf("-------
");
291     printf("|%c    |
", club);
292     printf("|  K  |
");
293     printf("|    %c|
", club);
294     printf("-------
");
295     k=10; //Set card value to 10
296     }
297     return k;           
298 }// End function
299  
300 int diamondcard() //Displays Diamond Card Image
301 {
302      
303      
304     srand((unsigned) time(NULL)); //Generates random seed for rand() function
305     k=rand()%13+1;
306      
307     if(k<=9) //If random number is 9 or less, print card with that number
308     {
309     //Diamond Card
310     printf("-------
");
311     printf("|%c    |
", diamond);
312     printf("|  %d  |
", k);
313     printf("|    %c|
", diamond);
314     printf("-------
");
315     }
316      
317     if(k==10) //If random number is 10, print card with J (Jack) on face
318     {
319     //Diamond Card
320     printf("-------
");
321     printf("|%c    |
", diamond);
322     printf("|  J  |
");
323     printf("|    %c|
", diamond);
324     printf("-------
");
325     }
326      
327     if(k==11) //If random number is 11, print card with A (Ace) on face
328     {
329     //Diamond Card
330     printf("-------
");
331     printf("|%c    |
", diamond);
332     printf("|  A  |
");
333     printf("|    %c|
", diamond);
334     printf("-------
");
335     if(player_total<=10) //If random number is Ace, change value to 11 or 1 depending on dealer total
336          {
337              k=11;
338          }
339           
340          else
341          {
342              k=1;
343          }
344     }
345      
346     if(k==12) //If random number is 12, print card with Q (Queen) on face
347     {
348     //Diamond Card
349     printf("-------
");
350     printf("|%c    |
", diamond);
351     printf("|  Q  |
");
352     printf("|    %c|
", diamond);
353     printf("-------
");
354     k=10; //Set card value to 10
355     }
356      
357     if(k==13) //If random number is 13, print card with K (King) on face
358     {
359     //Diamond Card
360     printf("-------
");
361     printf("|%c    |
", diamond);
362     printf("|  K  |
");
363     printf("|    %c|
", diamond);
364     printf("-------
");
365     k=10; //Set card value to 10
366     }
367     return k;
368 }// End function
369  
370 int heartcard() //Displays Heart Card Image
371 {
372      
373      
374     srand((unsigned) time(NULL)); //Generates random seed for rand() function
375     k=rand()%13+1;
376      
377     if(k<=9) //If random number is 9 or less, print card with that number
378     {
379     //Heart Card
380     printf("-------
");
381     printf("|%c    |
", heart); 
382     printf("|  %d  |
", k);
383     printf("|    %c|
", heart);
384     printf("-------
");
385     }
386      
387     if(k==10) //If random number is 10, print card with J (Jack) on face
388     {
389     //Heart Card
390     printf("-------
");
391     printf("|%c    |
", heart);
392     printf("|  J  |
");
393     printf("|    %c|
", heart);
394     printf("-------
");
395     }
396      
397     if(k==11) //If random number is 11, print card with A (Ace) on face
398     {
399     //Heart Card
400     printf("-------
");
401     printf("|%c    |
", heart);
402     printf("|  A  |
");
403     printf("|    %c|
", heart);
404     printf("-------
");
405     if(player_total<=10) //If random number is Ace, change value to 11 or 1 depending on dealer total
406          {
407              k=11;
408          }
409           
410          else
411          {
412              k=1;
413          }
414     }
415      
416     if(k==12) //If random number is 12, print card with Q (Queen) on face
417     {
418     //Heart Card
419     printf("-------
");
420     printf("|%c    |
", heart);
421     printf("|  Q  |
");
422     printf("|    %c|
", heart);
423     printf("-------
");
424     k=10; //Set card value to 10
425     }
426      
427     if(k==13) //If random number is 13, print card with K (King) on face
428     {
429     //Heart Card
430     printf("-------
");
431     printf("|%c    |
", heart);
432     printf("|  K  |
");
433     printf("|    %c|
", heart);
434     printf("-------
");
435     k=10; //Set card value to 10
436     }
437     return k;
438 } // End Function
439  
440 int spadecard() //Displays Spade Card Image
441 {
442      
443      
444     srand((unsigned) time(NULL)); //Generates random seed for rand() function
445     k=rand()%13+1;
446      
447     if(k<=9) //If random number is 9 or less, print card with that number
448     {
449     //Spade Card
450     printf("-------
");
451     printf("|%c    |
", spade);
452     printf("|  %d  |
", k);
453     printf("|    %c|
", spade);
454     printf("-------
");
455     }
456      
457     if(k==10) //If random number is 10, print card with J (Jack) on face
458     {
459     //Spade Card
460     printf("-------
");
461     printf("|%c    |
", spade);
462     printf("|  J  |
");
463     printf("|    %c|
", spade);
464     printf("-------
");
465     }
466      
467     if(k==11) //If random number is 11, print card with A (Ace) on face
468     {
469     //Spade Card
470     printf("-------
");
471     printf("|%c    |
", spade);
472     printf("|  A  |
");
473     printf("|    %c|
", spade);
474     printf("-------
");
475     if(player_total<=10) //If random number is Ace, change value to 11 or 1 depending on dealer total
476          {
477              k=11;
478          }
479           
480          else
481          {
482              k=1;
483          }
484     }
485      
486     if(k==12) //If random number is 12, print card with Q (Queen) on face
487     {
488     //Spade Card
489     printf("-------
");
490     printf("|%c    |
", spade);
491     printf("|  Q  |
");
492     printf("|    %c|
", spade);
493     printf("-------
");
494     k=10; //Set card value to 10
495     }
496      
497     if(k==13) //If random number is 13, print card with K (King) on face
498     {
499     //Spade Card
500     printf("-------
");
501     printf("|%c    |
", spade);
502     printf("|  K  |
");
503     printf("|    %c|
", spade);
504     printf("-------
");
505     k=10; //Set card value to 10
506     }
507     return k;
508 } // End Function
509  
510 int randcard() //Generates random card
511 {
512       
513                 
514      srand((unsigned) time(NULL)); //Generates random seed for rand() function
515      random_card = rand()%4+1;
516       
517      if(random_card==1)
518      {   
519          clubcard();
520          l=k;
521      }
522       
523      if(random_card==2)
524      {
525          diamondcard();
526          l=k;
527      }
528       
529      if(random_card==3)
530      {
531          heartcard();
532          l=k;
533      }
534           
535      if(random_card==4)
536      {
537          spadecard();
538          l=k;
539      }    
540      return l;
541 } // End Function   
542  
543 void play() //Plays game
544 {
545       
546      int p=0; // holds value of player_total
547      int i=1; // counter for asking user to hold or stay (aka game turns)
548      char choice3;
549       
550      cash = cash;
551      cash_test();
552      printf("
Cash: $%d
",cash); //Prints amount of cash user has
553      randcard(); //Generates random card
554      player_total = p + l; //Computes player total
555      p = player_total;
556      printf("
Your Total is %d
", p); //Prints player total
557      dealer(); //Computes and prints dealer total
558      betting(); //Prompts user to enter bet amount
559         
560      while(i<=21) //While loop used to keep asking user to hit or stay at most twenty-one times
561                   //  because there is a chance user can generate twenty-one consecutive 1's
562      {
563          if(p==21) //If user total is 21, win
564          {
565              printf("
Unbelievable! You Win!
");
566              won = won+1;
567              cash = cash+bet;
568              printf("
You have %d Wins and %d Losses. Awesome!
", won, loss);
569              dealer_total=0;
570              askover();
571          }
572       
573          if(p>21) //If player total is over 21, loss
574          {
575              printf("
Woah Buddy, You Went WAY over.
");
576              loss = loss+1;
577              cash = cash - bet;
578              printf("
You have %d Wins and %d Losses. Awesome!
", won, loss);
579              dealer_total=0;
580              askover();
581          }
582       
583          if(p<=21) //If player total is less than 21, ask to hit or stay
584          {         
585              printf("

Would You Like to Hit or Stay?");
586               
587              scanf("%c", &choice3);
588              while((choice3!='H') && (choice3!='h') && (choice3!='S') && (choice3!='s')) // If invalid choice entered
589              {                                                                           
590                  printf("
");
591                  printf("Please Enter H to Hit or S to Stay.
");
592                  scanf("%c",&choice3);
593              }
594  
595  
596              if((choice3=='H') || (choice3=='h')) // If Hit, continues
597              { 
598                  randcard();
599                  player_total = p + l;
600                  p = player_total;
601                  printf("
Your Total is %d
", p);
602                  dealer();
603                   if(dealer_total==21) //Is dealer total is 21, loss
604                   {
605                       printf("
Dealer Has the Better Hand. You Lose.
");
606                       loss = loss+1;
607                       cash = cash - bet;
608                       printf("
You have %d Wins and %d Losses. Awesome!
", won, loss);
609                       dealer_total=0;
610                       askover();
611                   } 
612       
613                   if(dealer_total>21) //If dealer total is over 21, win
614                   {                      
615                       printf("
Dealer Has Went Over!. You Win!
");
616                       won = won+1;
617                       cash = cash+bet;
618                       printf("
You have %d Wins and %d Losses. Awesome!
", won, loss);
619                       dealer_total=0;
620                       askover();
621                   }
622              }
623              if((choice3=='S') || (choice3=='s')) // If Stay, does not continue
624              {
625                 printf("
You Have Chosen to Stay at %d. Wise Decision!
", player_total);
626                 stay();
627              }
628           }
629              i++; //While player total and dealer total are less than 21, re-do while loop 
630      } // End While Loop
631 } // End Function
632  
633 void dealer() //Function to play for dealer AI
634 {
635      int z;
636       
637      if(dealer_total<17)
638      {
639       srand((unsigned) time(NULL) + 1); //Generates random seed for rand() function
640       z=rand()%13+1;
641       if(z<=10) //If random number generated is 10 or less, keep that value
642       {
643          d=z;
644           
645       }
646       
647       if(z>11) //If random number generated is more than 11, change value to 10
648       {
649          d=10;
650       }
651       
652       if(z==11) //If random number is 11(Ace), change value to 11 or 1 depending on dealer total
653       {
654          if(dealer_total<=10)
655          {
656              d=11;
657          }
658           
659          else
660          {
661              d=1;
662          }
663       }
664      dealer_total = dealer_total + d;
665      }
666            
667      printf("
The Dealer Has a Total of %d", dealer_total); //Prints dealer total
668       
669 } // End Function 
670  
671 void stay() //Function for when user selects 'Stay'
672 {
673      dealer(); //If stay selected, dealer continues going
674      if(dealer_total>=17)
675      {
676       if(player_total>=dealer_total) //If player's total is more than dealer's total, win
677       {
678          printf("
Unbelievable! You Win!
");
679          won = won+1;
680          cash = cash+bet;
681          printf("
You have %d Wins and %d Losses. Awesome!
", won, loss);
682          dealer_total=0;
683          askover();
684       }
685       if(player_total<dealer_total) //If player's total is less than dealer's total, loss
686       {
687          printf("
Dealer Has the Better Hand. You Lose.
");
688          loss = loss+1;
689          cash = cash - bet;
690          printf("
You have %d Wins and %d Losses. Awesome!
", won, loss);
691          dealer_total=0;
692          askover();
693       }
694       if(dealer_total>21) //If dealer's total is more than 21, win
695       {
696          printf("
Unbelievable! You Win!
");
697          won = won+1;
698          cash = cash+bet;
699          printf("
You have %d Wins and %d Losses. Awesome!
", won, loss);
700          dealer_total=0;
701          askover();
702       }
703      }
704      else
705      {
706          stay();
707      }
708       
709 } // End Function
710  
711 void cash_test() //Test for if user has cash remaining in purse
712 {
713      if (cash <= 0) //Once user has zero remaining cash, game ends and prompts user to play again
714      {
715         printf("You Are Bankrupt. Game Over");
716         cash = 500;
717         askover();
718      }
719 } // End Function
720  
721 int betting() //Asks user amount to bet
722 {
723  printf("

Enter Bet: $");
724  scanf("%d", &bet);
725  
726  if (bet > cash) //If player tries to bet more money than player has
727  {
728         printf("
You cannot bet more money than you have.");
729         printf("
Enter Bet: ");
730         scanf("%d", &bet);
731         return bet;
732  }
733  else return bet;
734 } // End Function
735  
736 void askover() // Function for asking player if they want to play again
737 {
738     char choice1;
739          
740      printf("
Would You Like To Play Again?");
741      printf("
Please Enter Y for Yes or N for No
");
742      scanf("
%c",&choice1);
743  
744     while((choice1!='Y') && (choice1!='y') && (choice1!='N') && (choice1!='n')) // If invalid choice entered
745     {                                                                           
746         printf("
");
747         printf("Incorrect Choice. Please Enter Y for Yes or N for No.
");
748         scanf("%c",&choice1);
749     }
750  
751  
752     if((choice1 == 'Y') || (choice1 == 'y')) // If yes, continue.
753     { 
754             system("cls");
755             play();
756     }
757   
758     else if((choice1 == 'N') || (choice1 == 'n')) // If no, exit program
759     {
760         fileresults();
761         printf("
BYE!!!!

");
762         system("pause");
763         exit(0);
764     }
765     return;
766 } // End function
767  
768 void fileresults() //Prints results into Blackjack.txt file in program directory
769 {
770     FILE *fpresults; //File pointer is fpresults
771     fpresults = fopen(RESULTS, "w"); //Creates file and writes into it
772     if(fpresults == NULL) // what to do if file missing from directory
773     {
774                printf("
Error: File Missing
");
775                system("pause");
776                exit(1);
777     }
778     else
779     {     
780      fprintf(fpresults,"
	 RESULTS");
781      fprintf(fpresults,"
	---------
");
782      fprintf(fpresults,"
You Have Won %d Times
", won);
783      fprintf(fpresults,"
You Have Lost %d Times
", loss);
784      fprintf(fpresults,"
Keep Playing and Set an All-Time Record!");
785     } 
786      fclose(fpresults);
787      return;
788 } // End Function

View Code

虽然代码足足有近800行，但根据代码的流程逐渐分析，还是能分析出以下信息：

游戏规则
- 玩家在每轮游戏开始之前设置赌资；
- 玩家的任务是通过hit（继续加扑克牌）或者stay（等待）使自己的点数之和等于21；
- 卡片1~10的点数即为相对应的数字，卡片J，Q，K的点数为10，卡片A的点数为11；
- 当自己的点数大于了21，或者自己的点数小于了庄家的点数，玩家输；则要从赌本中减去赌资；
- 当玩家的点数之和等于21时，玩家胜；玩家就从庄家处赚取同赌资金额的金钱；
当玩家的赌本大于1000000时，胜利，即可拿到flag；

由以上分析，首先先到了三种方法作弊（或者相信自己的人品无穷大，可以通过自己的努力能成为百万富翁）：

直接修改赌本为 ≥ 1000000；
通过修改，使自己每局都能获胜，那么需要
在每局结束时动手脚，增加赌本

分析代码，前两种想法没有找到相应的漏洞，
第三种方法，分析betting函数:

 1 int betting() //Asks user amount to bet
 2 {
 3  printf("

Enter Bet: $");
 4  scanf("%d", &bet);
 5 
 6  if (bet > cash) //If player tries to bet more money than player has
 7  {
 8         printf("
You cannot bet more money than you have.");
 9         printf("
Enter Bet: ");
10         scanf("%d", &bet);
11         return bet;
12  }
13  else return bet;
14 } // End Function

可以看出函数对输入的赌资只做了是否小于赌本的判断，那么我们就可以输入一个负的大小合适的赌本（大小合适指不会数据溢出），如-1000000；
那么，如果我们输掉了那一局，我们的赌本就要减负的1000000，就是加正的1000000，就可以拿到flag；

经过几次探索，拿到flag如下：

则flag即为YaY_I_AM_A_MILLIONARE_LOL
2017-2-16 8:16;47

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原文地址：https://www.cnblogs.com/WangAoBo/p/6404135.html

pwnable.kr-balckjack-Writeup

pwnable.kr-balckjack-Writeup

游戏规则

当玩家的赌本大于1000000时，胜利，即可拿到flag；