5.re-for-50-plz-50 tu-ctf-2016
流程很简单，异或比较
1 x=list('cbtcqLUBChERV[[Nh@_X^D]X_YPV[CJ') 2 y=0x37 3 z='' 4 for t in x: 5 z+=chr(ord(t)^y) 6 print(z)
TUCTF{but_really_whoisjohngalt}
6.key csaw-ctf-2016-quals
运行后打印完?W?h?a?t h?a?p?p?e?n? 便结束
修改指令跳过文件读取，输出=W=r=o=n=g=K=e=y=
关键点就是sub_4020c0函数
关注if比较处
动态调试可直接获得flag
这里的的v7其实是sub_4020c0函数中第三个参数
关注Memory，发现两次循环处理
脚本：
1 x=[ 0x74, 0x68, 0x65, 0x6D, 0x69, 0x64, 0x61, 0x74, 0x68, 0x65, 2 0x6D, 0x69, 0x64, 0x61, 0x74, 0x68, 0x65, 0x6D, 0x69, 0x64, 3 0x6] 4 y=[0x3E, 0x2D, 0x2D, 0x2D, 0x2D, 0x2B, 0x2B, 0x2B, 0x2B, 0x2E, 5 0x2E, 0x2E, 0x2E, 0x3C, 0x3C, 0x3C, 0x3C, 0x2E] 6 # print(len(x)) 7 # print(len(y)) 8 z=[] 9 for i in range(18): 10 z.append((x[i]^y[i])+22+9) 11 12 # print(' '.join(map(hex,z))) 13 print(''.join(map(chr,z)))
idg_cni~bjbfi|gsxb
7.simple-check-100 school-ctf-winter-2015
exe文件有坑，满是辛酸泪，分析elf文件
过掉check_key()函数在linux便可直接输出flag
分析：
1 a1[0] = 0xE37EC854; 2 a1[1] = 0x9A16C764; 3 a1[2] = 0x326511CD; 4 a1[3] = 0x43D3E32D; 5 a1[4] = 0xD29DA992; 6 a1[5] = 0xD32C6DE6; 7 a1[6] = 0x6AFEBDB6; 8 v14 = 0x13; 9 v3 = alloca(32); 10 v15 = &v7; 11 printf("Key: "); 12 __isoc99_scanf((int)"%s", (int)v15, v5, v6, v7, v8, v9, (int)v10, v11, v12, a1[0], a1[1], a1[2], a1[3], a1[4], a1[5]); 13 if ( check_key((int)v15) ) 14 interesting_function(a1);
1 unsigned int *__cdecl interesting_function(int a1[7]) 2 { 3 unsigned int *result; // eax 4 unsigned int temp; // [esp+18h] [ebp-20h] 5 int i; // [esp+1Ch] [ebp-1Ch] 6 int j; // [esp+20h] [ebp-18h] 7 int *__attribute__((__org_arrdim(0,7))) v5; // [esp+24h] [ebp-14h] 8 char *ptr_temp; // [esp+28h] [ebp-10h] 9 unsigned int v7; // [esp+2Ch] [ebp-Ch] 10 11 v7 = __readgsdword(0x14u); 12 result = (unsigned int *)a1; 13 v5 = a1; 14 for ( i = 0; i <= 6; ++i ) 15 { 16 temp = v5[i] ^ 0xDEADBEEF; 17 result = &temp; 18 ptr_temp = (char *)&temp; 19 for ( j = 3; j >= 0; --j ) 20 result = (unsigned int *)putchar((char)(ptr_temp[j] ^ flag_data[i][j])); 21 } 22 return result; 23 }
脚本：
1 win=[0x54, 0xB8, 0xFE, 0x61, 0x00, 0x13, 0x00, 0x00, 0x00, 0x61, 0x6A, 0xFE, 0xBD, 0xB6, 0xD3, 0x2C, 2 0x6D, 0xE6, 0xD2, 0x9D, 0xA9, 0x92, 0x43, 0xD3, 0xE3, 0x2D, 0x32, 0x65, 0x11, 0xCD, 0x9A, 0x16, 3 0xC7, 0x64, 0xE3, 0x7E, 0xC8, 0x30]#windows下调试获取的操作数据 4 win2=[0x6A, 0xFE, 0xBD, 0xB6, 0xD3, 0x2C, 5 0x6D, 0xE6, 0xD2, 0x9D, 0xA9, 0x92, 0x43, 0xD3, 0xE3, 0x2D, 0x32, 0x65, 0x11, 0xCD, 0x9A, 0x16, 6 0xC7, 0x64, 0xE3, 0x7E, 0xC8, 0x54] 7 win2=win2[::-1] 8 9 flag_date=[0xDC, 0x17, 0xBF, 0x5B, 0xD4, 0x0A, 0xD2, 0x1B, 0x7D, 0xDA, 10 0xA7, 0x95, 0xB5, 0x32, 0x10, 0xF6, 0x1C, 0x65, 0x53, 0x53, 11 0x67, 0xBA, 0xEA, 0x6E, 0x78, 0x22, 0x72, 0xD3] 12 13 14 a1=[0 for i in range(7)] 15 a1[0] = 0xE37EC854; 16 a1[1] = 0x9A16C764; 17 a1[2] = 0x326511CD; 18 a1[3] = 0x43D3E32D; 19 a1[4] = 0xD29DA992; 20 a1[5] = 0xD32C6DE6; 21 a1[6] = 0x6AFEBDB6; 22 23 x=[0xef,0xbe,0xad,0xde] 24 25 s='' 26 for i in range(7): 27 temp=(a1[i]^0xDEADBEEF).to_bytes(4,'little') 28 for j in range(3,-1,-1): 29 s+=chr(temp[j]^flag_date[i*4+j]) 30 print(chr(win[i * 4 + j] ^ flag_date[i * 4 + j] ^ x[j]), end='') 31 # print(chr(v8[i*4+j]^flag_date[i*4+j]^x[j]),end='') 32 print() 33 print(s)
exe中栈内变量布局与linux不同，
exe文件：äìgŧ;µ`n:ç,=c!hí±t
elf文件：flag_is_you_know_cracking!!!
flag_is_you_know_cracking!!!