题目很有意思。是我们所熟悉的21点游戏。题目的意思是，当我们赢得100万的时候，我们就会get到flag，游戏代码较长放在文末：
其实这个游戏还是很好玩的，一拿到代码，我就首先怀疑会不会还是rand函数用同一个种子的问题，但是阅读了源代码发现并不是这个问题。
于是我就尝试输入了一些非法数据，发现程序对金钱的上限有限制，对下限没有限制。另外我们还注意到，在第二次输入的时候没有了前面的$符号，也就是说，这两个输入可能是分别来写的～oh，interesting~
我们故意输一下，想赢是需要运气，但是输的话这个还是很容易,我们发现，虽然我们输了，但是我们的钱增加了
让我们来阅读源码，看看bet和cash到底是如何存储和比较的。
在int betting函数中,它只对输入的金额做了一次判断，当第二次输入的时候，就直接返回bet了。
所以我们就可以很轻松的通过nc pwnable.kr 9009连接到服务器后得到flag了
// Programmer: Vladislav Shulman
// Final Project
// Blackjack
// Feel free to use any and all parts of this program and claim it as your own work
//FINAL DRAFT
#include <stdlib.h>
#include <stdio.h>
#include <math.h>
#include <time.h> //Used for srand((unsigned) time(NULL)) command
//#include <process.h> //Used for system("clear") command
#define spade 06 //Used to print spade symbol
#define club 05 //Used to print club symbol
#define diamond 04 //Used to print diamond symbol
#define heart 03 //Used to print heart symbol
#define RESULTS "Blackjack.txt" //File name is Blackjack
//Global Variables
int k;
int l;
int d;
int won;
int loss;
int cash = 500;
int bet;
int random_card;
int player_total=0;
int dealer_total;
//Function Prototypes
int clubcard(); //Displays Club Card Image
int diamondcard(); //Displays Diamond Card Image
int heartcard(); //Displays Heart Card Image
int spadecard(); //Displays Spade Card Image
int randcard(); //Generates random card
int betting(); //Asks user amount to bet
void asktitle(); //Asks user to continue
void rules(); //Prints "Rules of Vlad's Blackjack" menu
void play(); //Plays game
void dealer(); //Function to play for dealer AI
void stay(); //Function for when user selects 'Stay'
void cash_test(); //Test for if user has cash remaining in purse
void askover(); //Asks if user wants to continue playing
void fileresults(); //Prints results into Blackjack.txt file in program directory
//Main Function
int main(void)
{
int choice1;
printf("\n");
printf("\n");
printf("\n");
printf("\n 222 111 ");
printf("\n 222 222 11111 ");
printf("\n 222 222 11 111 ");
printf("\n 222 111 ");
printf("\n 222 111 ");
printf("\n");
printf("\n%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);
printf("\n%c %c %c%c %c %c %c %c %c %c ", club, club, spade, spade, diamond, diamond, heart, heart, club, club);
printf("\n%c %c %c%c %c %c %c %c %c ", club, club, spade, spade, diamond, diamond, heart, club, club);
printf("\n%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);
printf("\n%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);
printf("\n%c %c %c%c %c %c %c %c %c ", club, club, spade, spade, diamond, diamond, heart, club, club);
printf("\n%c %c %c%c %c %c %c %c %c %c ", club, club, spade, spade, diamond, diamond, heart, heart, club, club);
printf("\n%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);
printf("\n");
printf("\n 21 ");
printf("\n %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);
printf("\n %c%c %c %c %c %c %c %c ", diamond, diamond, heart, heart, club, club, spade, spade);
printf("\n %c%c %c %c %c %c %c ", diamond, diamond, heart, heart, club, spade, spade);
printf("\n %c%c %c %c%c %c %c %c %c ", diamond, diamond, heart, heart, heart, heart, club, spade, spade);
printf("\n %c%c %c %c%c%c%c %c %c %c%c %c ", diamond, diamond, heart, heart, heart, heart, heart, heart, club, spade, spade, spade);
printf("\n %c%c %c %c %c %c %c ", diamond, diamond, heart, heart, club, spade, spade);
printf("\n %c %c%c %c %c %c %c %c %c ", diamond, diamond, diamond, heart, heart, club, spade, spade);
printf("\n %c%c%c %c %c %c%c%c%c%c %c %c ", diamond, diamond, diamond, heart, heart, club, club, club, club, club, spade, spade);
printf("\n");
printf("\n 222 111 ");
printf("\n 222 111 ");
printf("\n 222 111 ");
printf("\n 222222222222222 111111111111111 ");
printf("\n 2222222222222222 11111111111111111 ");
printf("\n");
printf("\n");
asktitle();
printf("\n");
printf("\n");
system("pause");
return(0);
} //end program
void asktitle() // Function for asking player if they want to continue
{
char choice1;
int choice2;
printf("\n Are You Ready?");
printf("\n ----------------");
printf("\n (Y/N)\n ");
scanf("\n%c",&choice1);
while((choice1!='Y') && (choice1!='y') && (choice1!='N') && (choice1!='n')) // If invalid choice entered
{
printf("\n");
printf("Incorrect Choice. Please Enter Y for Yes or N for No.\n");
scanf("%c",&choice1);
}
if((choice1 == 'Y') || (choice1 == 'y')) // If yes, continue. Prints menu.
{
system("clear");
printf("\nEnter 1 to Begin the Greatest Game Ever Played.");
printf("\nEnter 2 to See a Complete Listing of Rules.");
printf("\nEnter 3 to Exit Game. (Not Recommended)");
printf("\nChoice: ");
scanf("%d", &choice2); // Prompts user for choice
if((choice2<1) || (choice2>3)) // If invalid choice entered
{
printf("\nIncorrect Choice. Please enter 1, 2 or 3\n");
scanf("%d", &choice2);
}
switch(choice2) // Switch case for different choices
{
case 1: // Case to begin game
system("clear");
play();
break;
case 2: // Case to see rules
system("clear");
rules();
break;
case 3: // Case to exit game
printf("\nYour day could have been perfect.");
printf("\nHave an almost perfect day!\n\n");
system("pause");
exit(0);
break;
default:
printf("\nInvalid Input");
} // End switch case
} // End if loop
else if((choice1 == 'N') || (choice1 == 'n')) // If no, exit program
{
printf("\nYour day could have been perfect.");
printf("\nHave an almost perfect day!\n\n");
system("pause");
exit(0);
}
return;
} // End function
void rules() //Prints "Rules of Vlad's Blackjack" list
{
char choice1;
int choice2;
printf("\n RULES of VLAD's BLACKJACK");
printf("\n ---------------------------");
printf("\nI.");
printf("\n Thou shalt not question the odds of this game.");
printf("\n %c This program generates cards at random.", spade);
printf("\n %c If you keep losing, you are very unlucky!\n", diamond);
printf("\nII.");
printf("\n Each card has a value.");
printf("\n %c Number cards 1 to 10 hold a value of their number.", spade);
printf("\n %c J, Q, and K cards hold a value of 10.", diamond);
printf("\n %c Ace cards hold a value of 11", club);
printf("\n The goal of this game is to reach a card value total of 21.\n");
printf("\nIII.");
printf("\n After the dealing of the first two cards, YOU must decide whether to HIT or STAY.");
printf("\n %c Staying will keep you safe, hitting will add a card.", spade);
printf("\n Because you are competing against the dealer, you must beat his hand.");
printf("\n BUT BEWARE!.");
printf("\n %c If your total goes over 21, you will LOSE!.", diamond);
printf("\n But the world is not over, because you can always play again.\n");
printf("\n%c%c%c YOUR RESULTS ARE RECORDED AND FOUND IN SAME FOLDER AS PROGRAM %c%c%c\n", spade, heart, club, club, heart, spade);
printf("\nWould you like to go the previous screen? (I will not take NO for an answer)");
printf("\n (Y/N)\n ");
scanf("\n%c",&choice1);
while((choice1!='Y') && (choice1!='y') && (choice1!='N') && (choice1!='n')) // If invalid choice entered
{
printf("\n");
printf("Incorrect Choice. Please Enter Y for Yes or N for No.\n");
scanf("%c",&choice1);
}
if((choice1 == 'Y') || (choice1 == 'y')) // If yes, continue. Prints menu.
{
system("clear");
asktitle();
} // End if loop
else if((choice1 == 'N') || (choice1 == 'n')) // If no, convinces user to enter yes
{
system("clear");
printf("\n I told you so.\n");
asktitle();
}
return;
} // End function
int clubcard() //Displays Club Card Image
{
srand((unsigned) time(NULL)); //Generates random seed for rand() function
k=rand()%13+1;
if(k<=9) //If random number is 9 or less, print card with that number
{
//Club Card
printf("-------\n");
printf("|%c |\n", club);
printf("| %d |\n", k);
printf("| %c|\n", club);
printf("-------\n");
}
if(k==10) //If random number is 10, print card with J (Jack) on face
{
//Club Card
printf("-------\n");
printf("|%c |\n", club);
printf("| J |\n");
printf("| %c|\n", club);
printf("-------\n");
}
if(k==11) //If random number is 11, print card with A (Ace) on face
{
//Club Card
printf("-------\n");
printf("|%c |\n", club);
printf("| A |\n");
printf("| %c|\n", club);
printf("-------\n");
if(player_total<=10) //If random number is Ace, change value to 11 or 1 depending on dealer total
{
k=11;
}
else
{
k=1;
}
}
if(k==12) //If random number is 12, print card with Q (Queen) on face
{
//Club Card
printf("-------\n");
printf("|%c |\n", club);
printf("| Q |\n");
printf("| %c|\n", club);
printf("-------\n");
k=10; //Set card value to 10
}
if(k==13) //If random number is 13, print card with K (King) on face
{
//Club Card
printf("-------\n");
printf("|%c |\n", club);
printf("| K |\n");
printf("| %c|\n", club);
printf("-------\n");
k=10; //Set card value to 10
}
return k;
}// End function
int diamondcard() //Displays Diamond Card Image
{
srand((unsigned) time(NULL)); //Generates random seed for rand() function
k=rand()%13+1;
if(k<=9) //If random number is 9 or less, print card with that number
{
//Diamond Card
printf("-------\n");
printf("|%c |\n", diamond);
printf("| %d |\n", k);
printf("| %c|\n", diamond);
printf("-------\n");
}
if(k==10) //If random number is 10, print card with J (Jack) on face
{
//Diamond Card
printf("-------\n");
printf("|%c |\n", diamond);
printf("| J |\n");
printf("| %c|\n", diamond);
printf("-------\n");
}
if(k==11) //If random number is 11, print card with A (Ace) on face
{
//Diamond Card
printf("-------\n");
printf("|%c |\n", diamond);
printf("| A |\n");
printf("| %c|\n", diamond);
printf("-------\n");
if(player_total<=10) //If random number is Ace, change value to 11 or 1 depending on dealer total
{
k=11;
}
else
{
k=1;
}
}
if(k==12) //If random number is 12, print card with Q (Queen) on face
{
//Diamond Card
printf("-------\n");
printf("|%c |\n", diamond);
printf("| Q |\n");
printf("| %c|\n", diamond);
printf("-------\n");
k=10; //Set card value to 10
}
if(k==13) //If random number is 13, print card with K (King) on face
{
//Diamond Card
printf("-------\n");
printf("|%c |\n", diamond);
printf("| K |\n");
printf("| %c|\n", diamond);
printf("-------\n");
k=10; //Set card value to 10
}
return k;
}// End function
int heartcard() //Displays Heart Card Image
{
srand((unsigned) time(NULL)); //Generates random seed for rand() function
k=rand()%13+1;
if(k<=9) //If random number is 9 or less, print card with that number
{
//Heart Card
printf("-------\n");
printf("|%c |\n", heart);
printf("| %d |\n", k);
printf("| %c|\n", heart);
printf("-------\n");
}
if(k==10) //If random number is 10, print card with J (Jack) on face
{
//Heart Card
printf("-------\n");
printf("|%c |\n", heart);
printf("| J |\n");
printf("| %c|\n", heart);
printf("-------\n");
}
if(k==11) //If random number is 11, print card with A (Ace) on face
{
//Heart Card
printf("-------\n");
printf("|%c |\n", heart);
printf("| A |\n");
printf("| %c|\n", heart);
printf("-------\n");
if(player_total<=10) //If random number is Ace, change value to 11 or 1 depending on dealer total
{
k=11;
}
else
{
k=1;
}
}
if(k==12) //If random number is 12, print card with Q (Queen) on face
{
//Heart Card
printf("-------\n");
printf("|%c |\n", heart);
printf("| Q |\n");
printf("| %c|\n", heart);
printf("-------\n");
k=10; //Set card value to 10
}
if(k==13) //If random number is 13, print card with K (King) on face
{
//Heart Card
printf("-------\n");
printf("|%c |\n", heart);
printf("| K |\n");
printf("| %c|\n", heart);
printf("-------\n");
k=10; //Set card value to 10
}
return k;
} // End Function
int spadecard() //Displays Spade Card Image
{
srand((unsigned) time(NULL)); //Generates random seed for rand() function
k=rand()%13+1;
if(k<=9) //If random number is 9 or less, print card with that number
{
//Spade Card
printf("-------\n");
printf("|%c |\n", spade);
printf("| %d |\n", k);
printf("| %c|\n", spade);
printf("-------\n");
}
if(k==10) //If random number is 10, print card with J (Jack) on face
{
//Spade Card
printf("-------\n");
printf("|%c |\n", spade);
printf("| J |\n");
printf("| %c|\n", spade);
printf("-------\n");
}
if(k==11) //If random number is 11, print card with A (Ace) on face
{
//Spade Card
printf("-------\n");
printf("|%c |\n", spade);
printf("| A |\n");
printf("| %c|\n", spade);
printf("-------\n");
if(player_total<=10) //If random number is Ace, change value to 11 or 1 depending on dealer total
{
k=11;
}
else
{
k=1;
}
}
if(k==12) //If random number is 12, print card with Q (Queen) on face
{
//Spade Card
printf("-------\n");
printf("|%c |\n", spade);
printf("| Q |\n");
printf("| %c|\n", spade);
printf("-------\n");
k=10; //Set card value to 10
}
if(k==13) //If random number is 13, print card with K (King) on face
{
//Spade Card
printf("-------\n");
printf("|%c |\n", spade);
printf("| K |\n");
printf("| %c|\n", spade);
printf("-------\n");
k=10; //Set card value to 10
}
return k;
} // End Function
int randcard() //Generates random card
{
srand((unsigned) time(NULL)); //Generates random seed for rand() function
random_card = rand()%4+1;
if(random_card==1)
{
clubcard();
l=k;
}
if(random_card==2)
{
diamondcard();
l=k;
}
if(random_card==3)
{
heartcard();
l=k;
}
if(random_card==4)
{
spadecard();
l=k;
}
return l;
} // End Function
void play() //Plays game
{
int p=0; // holds value of player_total
int i=1; // counter for asking user to hold or stay (aka game turns)
char choice3;
cash = cash;
cash_test();
printf("\nCash: $%d\n",cash); //Prints amount of cash user has
randcard(); //Generates random card
player_total = p + l; //Computes player total
p = player_total;
printf("\nYour Total is %d\n", p); //Prints player total
dealer(); //Computes and prints dealer total
betting(); //Prompts user to enter bet amount
while(i<=21) //While loop used to keep asking user to hit or stay at most twenty-one times
// because there is a chance user can generate twenty-one consecutive 1's
{
if(p==21) //If user total is 21, win
{
printf("\nUnbelievable! You Win!\n");
won = won+1;
cash = cash+bet;
printf("\nYou have %d Wins and %d Losses. Awesome!\n", won, loss);
dealer_total=0;
askover();
}
if(p>21) //If player total is over 21, loss
{
printf("\nWoah Buddy, You Went WAY over.\n");
loss = loss+1;
cash = cash - bet;
printf("\nYou have %d Wins and %d Losses. Awesome!\n", won, loss);
dealer_total=0;
askover();
}
if(p<=21) //If player total is less than 21, ask to hit or stay
{
printf("\n\nWould You Like to Hit or Stay?");
scanf("%c", &choice3);
while((choice3!='H') && (choice3!='h') && (choice3!='S') && (choice3!='s')) // If invalid choice entered
{
printf("\n");
printf("Please Enter H to Hit or S to Stay.\n");
scanf("%c",&choice3);
}
if((choice3=='H') || (choice3=='h')) // If Hit, continues
{
randcard();
player_total = p + l;
p = player_total;
printf("\nYour Total is %d\n", p);
dealer();
if(dealer_total==21) //Is dealer total is 21, loss
{
printf("\nDealer Has the Better Hand. You Lose.\n");
loss = loss+1;
cash = cash - bet;
printf("\nYou have %d Wins and %d Losses. Awesome!\n", won, loss);
dealer_total=0;
askover();
}
if(dealer_total>21) //If dealer total is over 21, win
{
printf("\nDealer Has Went Over!. You Win!\n");
won = won+1;
cash = cash+bet;
printf("\nYou have %d Wins and %d Losses. Awesome!\n", won, loss);
dealer_total=0;
askover();
}
}
if((choice3=='S') || (choice3=='s')) // If Stay, does not continue
{
printf("\nYou Have Chosen to Stay at %d. Wise Decision!\n", player_total);
stay();
}
}
i++; //While player total and dealer total are less than 21, re-do while loop
} // End While Loop
} // End Function
void dealer() //Function to play for dealer AI
{
int z;
if(dealer_total<17)
{
srand((unsigned) time(NULL) + 1); //Generates random seed for rand() function
z=rand()%13+1;
if(z<=10) //If random number generated is 10 or less, keep that value
{
d=z;
}
if(z>11) //If random number generated is more than 11, change value to 10
{
d=10;
}
if(z==11) //If random number is 11(Ace), change value to 11 or 1 depending on dealer total
{
if(dealer_total<=10)
{
d=11;
}
else
{
d=1;
}
}
dealer_total = dealer_total + d;
}
printf("\nThe Dealer Has a Total of %d", dealer_total); //Prints dealer total
} // End Function
void stay() //Function for when user selects 'Stay'
{
dealer(); //If stay selected, dealer continues going
if(dealer_total>=17)
{
if(player_total>=dealer_total) //If player's total is more than dealer's total, win
{
printf("\nUnbelievable! You Win!\n");
won = won+1;
cash = cash+bet;
printf("\nYou have %d Wins and %d Losses. Awesome!\n", won, loss);
dealer_total=0;
askover();
}
if(player_total<dealer_total) //If player's total is less than dealer's total, loss
{
printf("\nDealer Has the Better Hand. You Lose.\n");
loss = loss+1;
cash = cash - bet;
printf("\nYou have %d Wins and %d Losses. Awesome!\n", won, loss);
dealer_total=0;
askover();
}
if(dealer_total>21) //If dealer's total is more than 21, win
{
printf("\nUnbelievable! You Win!\n");
won = won+1;
cash = cash+bet;
printf("\nYou have %d Wins and %d Losses. Awesome!\n", won, loss);
dealer_total=0;
askover();
}
}
else
{
stay();
}
} // End Function
void cash_test() //Test for if user has cash remaining in purse
{
if (cash <= 0) //Once user has zero remaining cash, game ends and prompts user to play again
{
printf("You Are Bankrupt. Game Over");
cash = 500;
askover();
}
} // End Function
int betting() //Asks user amount to bet
{
printf("\n\nEnter Bet: $");
scanf("%d", &bet);
if (bet > cash) //If player tries to bet more money than player has
{
printf("\nYou cannot bet more money than you have.");
printf("\nEnter Bet: ");
scanf("%d", &bet);
return bet;
}
else return bet;
} // End Function
void askover() // Function for asking player if they want to play again
{
char choice1;
printf("\nWould You Like To Play Again?");
printf("\nPlease Enter Y for Yes or N for No\n");
scanf("\n%c",&choice1);
while((choice1!='Y') && (choice1!='y') && (choice1!='N') && (choice1!='n')) // If invalid choice entered
{
printf("\n");
printf("Incorrect Choice. Please Enter Y for Yes or N for No.\n");
scanf("%c",&choice1);
}
if((choice1 == 'Y') || (choice1 == 'y')) // If yes, continue.
{
system("clear");
play();
}
else if((choice1 == 'N') || (choice1 == 'n')) // If no, exit program
{
fileresults();
printf("\nBYE!!!!\n\n");
system("pause");
exit(0);
}
return;
} // End function
void fileresults() //Prints results into Blackjack.txt file in program directory
{
FILE *fpresults; //File pointer is fpresults
fpresults = fopen(RESULTS, "w"); //Creates file and writes into it
if(fpresults == NULL) // what to do if file missing from directory
{
printf("\nError: File Missing\n");
system("pause");
exit(1);
}
else
{
fprintf(fpresults,"\n\t RESULTS");
fprintf(fpresults,"\n\t---------\n");
fprintf(fpresults,"\nYou Have Won %d Times\n", won);
fprintf(fpresults,"\nYou Have Lost %d Times\n", loss);
fprintf(fpresults,"\nKeep Playing and Set an All-Time Record!");
}
fclose(fpresults);
return;
} // End Function