UNCTF2022wp

发表于2023-03-06更新于2023-04-01

whereisyourkey

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v5 = [0] * 10
v5[0] = 0x76
v5[1] = 0x67
v5[2] = 0x70
v5[3] = 0x6B
v5[4] = 0x63
v5[5] = 0x6D
v5[6] = 0x68
v5[7] = 0x6E
v5[8] = 0x63
v5[9] = 0x69

for i in range(10):
    if v5[i] == 0x6D:
        print("",end="")
    elif(v5[i] <= 110):
        v5[i] -= 2
    else:
        v5[i] += 3
    print(chr(v5[i]&0xff), end="")

ezzzzre

upx壳，用工具脱

简单的加密

image-20221117221123453

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flag = "HELLOCTF"
for i in flag:
    print(chr( ((ord(i)*2)-69) & 0xff), end="")

Sudoku

动调

v12

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8 5 2 4 9 1 6 7 3
1 9 6 7 3 8 2 5 4
4 3 7 5 6 2 9 1 8
5 2 8 1 4 6 3 9 7
3 7 4 9 2 5 8 6 1
9 6 1 3 8 7 4 2 5
2 1 9 8 5 4 7 3 6
7 4 3 6 1 9 5 8 2
6 8 5 2 7 3 1 4 9
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vme = 50
print("UNCTF{" +
      chr(29 + vme) + chr(15 + vme) + chr(29 + vme) + chr(24 + vme) +
      chr(39 + vme) + chr(25 + vme) + chr(29 + vme) + chr(20 + vme) +
      chr(32 + vme) + "}")

halo

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flag = [0x55, 0x0B, 0x68, 0x0C, 0x73, 0x3E, 0x0C, 0x3A, 0x5D, 0x1B,
          0x21, 0x75, 0x4F, 0x20, 0x4C, 0x71, 0x58, 0x7B, 0x59, 0x2C,
          0x00, 0x77, 0x58, 0x77, 0x0E, 0x72, 0x5B, 0x26, 0x0B, 0x70,
          0x0A, 0x77, 0x66, 0x77, 0x36, 0x76, 0x37, 0x76, 0x62, 0x72,
          0x6D, 0x27, 0x3F, 0x77, 0x26]

enc = ""

for i in range(1):
    flag[i] ^= 0x33

for i in range(len(flag)-1, 0, -1):
    flag[i] = flag[i] ^ i ^ flag[i-1]

for i in flag:
    print(chr(i), end="")
image-20221113213011482

异或满足交换律

Rusty CPU

ida64位无壳

image-20221115234054163

image-20221115234200492

看到将输入编码后塞进switch，猜测是虚拟机

找到操作码后就直接写脚本了

我是选择倒着运行去逆向的。

不过这题比较简单每一位都是单独加密的

手写也不是不行

脚本

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flag = [
    0x67, 0x83, 0x67, 0x70, 0x29, 0x27, 0x7F, 0x68, 0x6B, 0x76,
    0x69, 0x76, 0x74, 0x59, 0x73, 0x74, 0x6F, 0x83, 0x24, 0x91,
    0x7B, 0x20, 0x54, 0x16, 0x84, 0x58, 0x93, 0x62, 0x5D, 0x66,
    0x59, 0x4F
]

op = [
    0x11, 0x11,

    0x22, 0x22,
    0x80, 0x14, 0x1D,
    0x81, 0x11,

    0x80, 0x14, 0x13,
    0x81, 0x13,

    0x80, 0x14, 0x19,
    0x80, 0x12,

    0x80, 0x05,

    0x22, 0x22,

    0x80, 0x14, 0x1F,
    0x81, 0x11,

    0x80, 0x14, 0x10,
    0x81, 0x13,

    0x80, 0x14, 0x15,
    0x80, 0x12,

    0x80, 0x05,

    0x22, 0x22,
    0x80, 0x14, 0x1D,
    0x81, 0x11,
    0x80, 0x14, 0xFA,
    0x81, 0x02,
    0x80, 0x05,

    0x22, 0x22,
    0x80, 0x14, 0x1B,
    0x81, 0x11,
    0x80, 0x14, 0xFA,
    0x81, 0x02,
    0x80, 0x05,

    0x22, 0x22,
    0x80, 0x14, 0x1E,
    0x81, 0x11,
    0x80, 0x14, 0x18,
    0x81, 0x13,
    0x80, 0x14, 0x22,
    0x80, 0x12,
    0x80, 0x05,

    0x22, 0x22,
    0x80, 0x14, 0x17,
    0x81, 0x13,
    0x80, 0x05,

    0x22, 0x22, 0x80, 0x14, 0x24, 0x81, 0x11, 0x80, 0x14, 0x1A,
    0x81, 0x13, 0x80, 0x14, 0x1A, 0x80, 0x12, 0x80, 0x05,

    0x22, 0x22, 0x80, 0x14, 0x1E, 0x81, 0x11, 0x80, 0x14, 0x16, 0x81,
    0x13, 0x80, 0x14, 0x1C, 0x80, 0x12, 0x80, 0x05,

    0x22, 0x22,
    0x80, 0x14, 0x20, 0x81, 0x11, 0x80, 0x14, 0xFA, 0x81, 0x02,
    0x80, 0x05,

    0x22, 0x22, 0x80, 0x14, 0x24, 0x81, 0x11, 0x80,
    0x14, 0x14, 0x81, 0x13, 0x80, 0x14, 0x21, 0x80, 0x12, 0x80,
    0x05,

    0x22, 0x22, 0x80, 0x14, 0x24, 0x81, 0x11, 0x80, 0x14,
    0xFA, 0x81, 0x02, 0x80, 0x05,

    0x22, 0x22, 0x80, 0x14, 0x1D,
    0x81, 0x13, 0x80, 0x05,

    0x22, 0x22, 0x80, 0x14, 0x29, 0x81,
    0x11, 0x80, 0x14, 0x1F, 0x81, 0x13, 0x80, 0x14, 0x23, 0x80,
    0x12, 0x80, 0x05,

    0x22, 0x22, 0x80, 0x14, 0x2B, 0x81, 0x11,
    0x80, 0x14, 0x1A, 0x81, 0x13, 0x80, 0x14, 0x1D, 0x80, 0x12,
    0x80, 0x05,

    0x22, 0x22, 0x80, 0x14, 0x1E, 0x81, 0x13, 0x80,
    0x05,

    0x22, 0x22, 0x80, 0x14, 0x27, 0x81, 0x11, 0x80, 0x14,
    0x1B, 0x81, 0x13, 0x80, 0x14, 0x23, 0x80, 0x12, 0x80, 0x05,

    0x22, 0x22, 0x80, 0x14, 0x1D, 0x81, 0x13, 0x80, 0x05,

    0x22, 0x22, 0x80, 0x14, 0x2A, 0x81, 0x11, 0x80, 0x14, 0x24, 0x81,
    0x13, 0x80, 0x14, 0x26, 0x80, 0x12, 0x80, 0x05,

    0x22, 0x22,
    0x80, 0x14, 0x2A, 0x81, 0x11, 0x80, 0x14, 0x1C, 0x81, 0x13,
    0x80, 0x14, 0x23, 0x80, 0x12, 0x80, 0x05,

    0x22, 0x22, 0x80,
    0x14, 0x30, 0x81, 0x11, 0x80, 0x14, 0x27, 0x81, 0x13, 0x80,
    0x14, 0x25, 0x80, 0x12, 0x80, 0x05,

    0x22, 0x22, 0x80, 0x14,
    0x2D, 0x81, 0x11, 0x80, 0x14, 0x26, 0x81, 0x13, 0x80, 0x14,
    0x2F, 0x80, 0x12, 0x80, 0x05,

    0x22, 0x22, 0x80, 0x14, 0x2B,
    0x81, 0x11, 0x80, 0x14, 0x22, 0x81, 0x13, 0x80, 0x14, 0x30,
    0x80, 0x12, 0x80, 0x05,

    0x22, 0x22, 0x80, 0x14, 0x26, 0x81,
    0x13, 0x80, 0x05,

    0x22, 0x22, 0x80, 0x14, 0x2F, 0x81, 0x11,
    0x80, 0x14, 0x21, 0x81, 0x13, 0x80, 0x14, 0x2D, 0x80, 0x12,
    0x80, 0x05,

    0x22, 0x22, 0x80, 0x14, 0x36, 0x81, 0x11, 0x80,
    0x14, 0x27, 0x81, 0x13, 0x80, 0x14, 0x2C, 0x80, 0x12, 0x80,
    0x05,

    0x22, 0x22, 0x80, 0x14, 0x2C, 0x81, 0x13, 0x80, 0x05,

    0x22, 0x22, 0x80, 0x14, 0x37, 0x81, 0x11, 0x80, 0x14, 0x28,
    0x81, 0x13, 0x80, 0x14, 0x2B, 0x80, 0x12, 0x80, 0x05,

    0x22, 0x22, 0x80, 0x14, 0x37, 0x81, 0x11, 0x80, 0x14, 0xFA, 0x81,
    0x02, 0x80, 0x05,

    0x22, 0x22, 0x80, 0x14, 0x36, 0x81, 0x11,
    0x80, 0x14, 0xFA, 0x81, 0x02, 0x80, 0x05,

    0x22, 0x22, 0x80,
    0x14, 0x33, 0x81, 0x11, 0x80, 0x14, 0xFA, 0x81, 0x02, 0x80,
    0x05,

    0x22, 0x22, 0x80, 0x14, 0x38, 0x81, 0x11, 0x80, 0x14,
    0xFA, 0x81, 0x02, 0x80, 0x05,

    0x22, 0x22, 0x80, 0x14, 0x3D,
    0x81, 0x11, 0x80, 0x14, 0x2F, 0x81, 0x13, 0x80, 0x14, 0x35,
    0x80, 0x12, 0x80, 0x05
]

pos = len(flag)
tmp = 0

for i in range(len(op) - 2, -1, -1):
    if op[i] == 0x80 and op[i + 1] == 0x05:
        pos -= 1

    elif op[i] == 0x80 and op[i + 1] == 0x14:
        tmp = op[i + 2]
        if op[i + 3] == 0x81 and op[i + 4] == 0x13:
            flag[pos] ^= tmp
        elif op[i + 3] == 0x81 and op[i + 4] == 0x11:
            flag[pos] -= tmp
        elif op[i + 3] == 0x80 and op[i + 4] == 0x12:
            flag[pos] += tmp
        elif op[i + 3] == 0x81 and op[i + 4] == 0x02:
            flag[pos] = tmp - flag[pos]

for i in range(0, len(flag)):
    print(chr(flag[i] & 0xff), end="")

vivo50_to_mk_Amerc1a_Gr3at_again

UNCTF{B1den_will_make_Ch1na_gr3at!}

shelled_babyxor

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flag = [
    0x73, 0x68, 0x65, 0x72,
    0x60, 0x5D, 0x5F, 0x49,
    0X53, 0x79, 0x4C, 0x53,
    0x55, 0x52, 0x79, 0x53,
    0x48, 0x56, 0x47, 0x45,
    0x4D, 0x43, 0x42, 0x79,
    0x5F, 0x49, 0x53, 0x54,
    0x79, 0x40, 0x4F, 0x54,
    0x55, 0x52, 0x79, 0x56,
    0x54, 0x49, 0x41, 0x54,
    0x47
]

for i in flag:
    print(chr( (i^0x26) & 0xff), end="")