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[原创]KCTF2022春季赛第三题分析(4qwerty7)
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发表于: 2022-5-13 20:13 6345
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用 SEH 异常修改了部分内容的AES加密，要求输入被加密后的结果等于特定值。
首先密钥是字符串 Enj0y_1t_4_fuuuN 被修改后的 MD5 哈希后的值。
MD5 的修改在于其正弦表 sine_table[42] = 0xD4AF3085。
然后 AES 加密的逻辑中将 Sbox 的部分内容修改，修改后的 Sbox 表为
密钥扩展部分未使用被修改的部分。
行移位的代码被改成逆行移位；同时最终比较的结果中也有两字节被修改，结果为 577CF56D56967745B0BDA1C789A5ABDCF4F24BFEBEF5F55C4D30420F2B3BE6CB。
找份AES随便改改就行
[ 99, 124, 119, 123, 242, 107, 111, 197, 48, 1,
103, 43, 254, 215, 171, 118, 202, 130, 201, 125,
250, 89, 71, 240, 173, 212, 162, 175, 156, 164,
114, 192, 183, 253, 147, 38, 54, 63, 247, 204,
52, 165, 229, 241, 113, 216, 49, 21, 4, 199,
35, 195, 24, 150, 5, 154, 7, 18, 128, 226,
235, 39, 178, 117, 9, 131, 44, 26, 27, 110,
90, 160, 82, 59, 214, 179, 41, 227, 47, 132,
83, 209, 0, 237, 32, 252, 177, 91, 106, 203,
190, 57, 74, 76, 88, 207, 208, 239, 170, 251,
67, 77, 51, 133, 69, 249, 2, 127, 80, 60,
159, 168, 81, 10, 64, 143, 146, 157, 56, 245,
188, 182, 218, 33, 16, 255, 243, 210, 205, 12,
19, 236, 95, 151, 68, 23, 196, 167, 126, 61,
100, 93, 25, 115, 96, 129, 79, 220, 34, 42,
144, 136, 70, 238, 184, 20, 222, 94, 11, 219,
224, 50, 58, 163, 73, 6, 36, 92, 194, 211,
172, 98, 145, 149, 228, 121, 231, 200, 55, 109,
141, 213, 78, 169, 108, 86, 244, 234, 101, 122,
174, 8, 186, 120, 37, 46, 28, 166, 180, 198,
232, 221, 116, 31, 75, 189, 139, 138, 112, 62,
181, 102, 72, 3, 246, 14, 97, 53, 87, 185,
134, 193, 29, 158, 225, 248, 152, 17, 105, 217,
142, 148, 155, 30, 135, 233, 206, 85, 40, 223,
140, 161, 137, 13, 191, 230, 66, 104, 65, 153,
45, 15, 176, 84, 187, 22
][ 99, 124, 119, 123, 242, 107, 111, 197, 48, 1,
103, 43, 254, 215, 171, 118, 202, 130, 201, 125,
250, 89, 71, 240, 173, 212, 162, 175, 156, 164,
114, 192, 183, 253, 147, 38, 54, 63, 247, 204,
52, 165, 229, 241, 113, 216, 49, 21, 4, 199,
35, 195, 24, 150, 5, 154, 7, 18, 128, 226,
235, 39, 178, 117, 9, 131, 44, 26, 27, 110,
90, 160, 82, 59, 214, 179, 41, 227, 47, 132,
83, 209, 0, 237, 32, 252, 177, 91, 106, 203,
190, 57, 74, 76, 88, 207, 208, 239, 170, 251,
67, 77, 51, 133, 69, 249, 2, 127, 80, 60,
159, 168, 81, 10, 64, 143, 146, 157, 56, 245,
188, 182, 218, 33, 16, 255, 243, 210, 205, 12,
19, 236, 95, 151, 68, 23, 196, 167, 126, 61,
100, 93, 25, 115, 96, 129, 79, 220, 34, 42,
144, 136, 70, 238, 184, 20, 222, 94, 11, 219,
224, 50, 58, 163, 73, 6, 36, 92, 194, 211,
172, 98, 145, 149, 228, 121, 231, 200, 55, 109,
141, 213, 78, 169, 108, 86, 244, 234, 101, 122,
174, 8, 186, 120, 37, 46, 28, 166, 180, 198,
232, 221, 116, 31, 75, 189, 139, 138, 112, 62,
181, 102, 72, 3, 246, 14, 97, 53, 87, 185,
134, 193, 29, 158, 225, 248, 152, 17, 105, 217,
142, 148, 155, 30, 135, 233, 206, 85, 40, 223,
140, 161, 137, 13, 191, 230, 66, 104, 65, 153,
45, 15, 176, 84, 187, 22
]#My AES implementation# By Daniel Millerdef xor(s1, s2):
return tuple(a^b for a,b in zip(s1, s2))
class AES(object):
def __init__(self):
self.Gmul = {}
for f in (0x02, 0x03, 0x0e, 0x0b, 0x0d, 0x09):
self.Gmul[f] = tuple(self.gmul(f, x) for x in range(0,0x100))
Rcon = ( 0x8d, 0x01, 0x02, 0x04, 0x08, 0x10, 0x20, 0x40, 0x80, 0x1b, 0x36, 0x6c, 0xd8, 0xab, 0x4d, 0x9a )
Ori = tuple(list(bytes.fromhex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
Sbox = (
99, 124, 119, 123, 242, 107, 111, 197, 48, 1,
103, 43, 254, 215, 171, 118, 202, 130, 201, 125,
250, 89, 71, 240, 173, 212, 162, 175, 156, 164,
114, 192, 183, 253, 147, 38, 54, 63, 247, 204,
52, 165, 229, 241, 113, 216, 49, 21, 4, 199,
35, 195, 24, 150, 5, 154, 7, 18, 128, 226,
235, 39, 178, 117, 9, 131, 44, 26, 27, 110,
90, 160, 82, 59, 214, 179, 41, 227, 47, 132,
83, 209, 0, 237, 32, 252, 177, 91, 106, 203,
190, 57, 74, 76, 88, 207, 208, 239, 170, 251,
67, 77, 51, 133, 69, 249, 2, 127, 80, 60,
159, 168, 81, 10, 64, 143, 146, 157, 56, 245,
188, 182, 218, 33, 16, 255, 243, 210, 205, 12,
19, 236, 95, 151, 68, 23, 196, 167, 126, 61,
100, 93, 25, 115, 96, 129, 79, 220, 34, 42,
144, 136, 70, 238, 184, 20, 222, 94, 11, 219,
224, 50, 58, 163, 73, 6, 36, 92, 194, 211,
172, 98, 145, 149, 228, 121, 231, 200, 55, 109,
141, 213, 78, 169, 108, 86, 244, 234, 101, 122,
174, 8, 186, 120, 37, 46, 28, 166, 180, 198,
232, 221, 116, 31, 75, 189, 139, 138, 112, 62,
181, 102, 72, 3, 246, 14, 97, 53, 87, 185,
134, 193, 29, 158, 225, 248, 152, 17, 105, 217,
142, 148, 155, 30, 135, 233, 206, 85, 40, 223,
140, 161, 137, 13, 191, 230, 66, 104, 65, 153,
45, 15, 176, 84, 187, 22
)
Sbox_inv = None
@staticmethod
def rot_word(word):
return word[1:] + word[:1]
@staticmethod
def sub_word(word):
return (AES.Sbox[b] for b in word)
def key_schedule(self):
expanded = []
expanded.extend(list(self.key))
for i in range(self.nk, self.nb * (self.nr + 1)):
t = expanded[(i-1)*4:i*4]
if i % self.nk == 0:
t = xor( AES.sub_word( AES.rot_word(t) ), (AES.Rcon[i // self.nk],0,0,0) )
elif self.nk > 6 and i % self.nk == 4:
t = AES.sub_word(t)
expanded.extend( xor(t, expanded[(i-self.nk)*4:(i-self.nk+1)*4]))
return expanded
def add_round_key(self, rkey):
for i, b in enumerate(rkey):
self.state[i] ^= b
def sub_bytes(self):
for i, b in enumerate(self.state):
self.state[i] = AES.Sbox[b]
def inv_sub_bytes(self):
for i, b in enumerate(self.state):
self.state[i] = AES.Sbox_inv[b]
def shift_rows(self):
rows = []
for r in range(4):
rows.append( self.state[r::4] )
rows[r] = rows[r][r:] + rows[r][:r]
self.state = [ r[c] for c in range(4) for r in rows ]
def inv_shift_rows(self):
rows = []
for r in range(4):
rows.append( self.state[r::4] )
rows[r] = rows[r][4-r:] + rows[r][:4-r]
self.state = [ r[c] for c in range(4) for r in rows ]
@staticmethod
def gmul(a, b):
p = 0
for c in range(8):
if b & 1:
p ^= a
a <<= 1
if a & 0x100:
a ^= 0x11b
b >>= 1
return p
def mix_columns(self):
ss = []
for c in range(4):
col = self.state[c*4:(c+1)*4]
ss.extend((
self.Gmul[0x02][col[0]] ^ self.Gmul[0x03][col[1]] ^ col[2] ^ col[3] ,
col[0] ^ self.Gmul[0x02][col[1]] ^ self.Gmul[0x03][col[2]] ^ col[3] ,
col[0] ^ col[1] ^ self.Gmul[0x02][col[2]] ^ self.Gmul[0x03][col[3]],
self.Gmul[0x03][col[0]] ^ col[1] ^ col[2] ^ self.Gmul[0x02][col[3]],
))
self.state = ss
def inv_mix_columns(self):
ss = []
for c in range(4):
col = self.state[c*4:(c+1)*4]
ss.extend((
self.Gmul[0x0e][col[0]] ^ self.Gmul[0x0b][col[1]] ^ self.Gmul[0x0d][col[2]] ^ self.Gmul[0x09][col[3]],
self.Gmul[0x09][col[0]] ^ self.Gmul[0x0e][col[1]] ^ self.Gmul[0x0b][col[2]] ^ self.Gmul[0x0d][col[3]],
self.Gmul[0x0d][col[0]] ^ self.Gmul[0x09][col[1]] ^ self.Gmul[0x0e][col[2]] ^ self.Gmul[0x0b][col[3]],
self.Gmul[0x0b][col[0]] ^ self.Gmul[0x0d][col[1]] ^ self.Gmul[0x09][col[2]] ^ self.Gmul[0x0e][col[3]],
))
self.state = ss
def state_to_mat(self):
def tt(v):
if v >= 128:
v -= 256
return v
k = 0
a = [[0]*4 for _ in range(4)]
for i in range(4):
for j in range(4):
a[j][i] = tt(self.state[k])
k += 1
return a
def cipher(self, block):
n = self.nb * 4
self.state = list(block)
keys = self.key_schedule()
self.add_round_key(keys[0:n])
for r in range(1, self.nr):
self.sub_bytes()
self.inv_shift_rows() # changed
self.mix_columns()
k = keys[r*n:(r+1)*n]
self.add_round_key(k)
self.sub_bytes()
self.inv_shift_rows() # changed
self.add_round_key(keys[self.nr*n:])
return bytes(self.state)
def inv_cipher(self, block):
n = self.nb * 4
self.state = list(block)
keys = self.key_schedule()
k = keys[self.nr*n:(self.nr+1)*n]
self.add_round_key(k)
for r in range(self.nr-1, 0, -1):
self.shift_rows() # changed
self.inv_sub_bytes()
k = keys[r*n:(r+1)*n]
self.add_round_key(k)
self.inv_mix_columns()
self.shift_rows() # changed
self.inv_sub_bytes()
self.add_round_key(keys[0:n])
return bytes(self.state)
def inv_box_gen(box):
inv = [0] * 256
for i, v in enumerate(box):
inv[v] = i
return tuple(inv)
AES.Sbox_inv = inv_box_gen(AES.Sbox)
class AES_128(AES):
def __init__(self):
super().__init__()
self.nb = 4
self.nr = 10
self.nk = 4
ori = b'1111111111111111'
key = bytes.fromhex('2F65B1FF31ED86D09A285C0F4048059D')
res = bytes.fromhex('1EE3517FDB630179A4109948246918BC')
cipher = AES_128()
cipher.key = key
print(cipher.cipher(ori) == res)
ans = bytes.fromhex('577CF56D56967745B0BDA1C789A5ABDCF4F24BFEBEF5F55C4D30420F2B3BE6CB')
print(cipher.inv_cipher(ans[:16]) + cipher.inv_cipher(ans[16:]))
# flag{db5c6a8dfec4d0ec5569899640}#My AES implementation# By Daniel Millerdef xor(s1, s2):
return tuple(a^b for a,b in zip(s1, s2))
class AES(object):
def __init__(self):
self.Gmul = {}
for f in (0x02, 0x03, 0x0e, 0x0b, 0x0d, 0x09):
self.Gmul[f] = tuple(self.gmul(f, x) for x in range(0,0x100))
Rcon = ( 0x8d, 0x01, 0x02, 0x04, 0x08, 0x10, 0x20, 0x40, 0x80, 0x1b, 0x36, 0x6c, 0xd8, 0xab, 0x4d, 0x9a )
Ori = tuple(list(bytes.fromhex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
Sbox = (
99, 124, 119, 123, 242, 107, 111, 197, 48, 1,
103, 43, 254, 215, 171, 118, 202, 130, 201, 125,
250, 89, 71, 240, 173, 212, 162, 175, 156, 164,
114, 192, 183, 253, 147, 38, 54, 63, 247, 204,
52, 165, 229, 241, 113, 216, 49, 21, 4, 199,
35, 195, 24, 150, 5, 154, 7, 18, 128, 226,
235, 39, 178, 117, 9, 131, 44, 26, 27, 110,
90, 160, 82, 59, 214, 179, 41, 227, 47, 132,
83, 209, 0, 237, 32, 252, 177, 91, 106, 203,
190, 57, 74, 76, 88, 207, 208, 239, 170, 251,
67, 77, 51, 133, 69, 249, 2, 127, 80, 60,
159, 168, 81, 10, 64, 143, 146, 157, 56, 245,
188, 182, 218, 33, 16, 255, 243, 210, 205, 12,
19, 236, 95, 151, 68, 23, 196, 167, 126, 61,
100, 93, 25, 115, 96, 129, 79, 220, 34, 42,
144, 136, 70, 238, 184, 20, 222, 94, 11, 219,
224, 50, 58, 163, 73, 6, 36, 92, 194, 211,
172, 98, 145, 149, 228, 121, 231, 200, 55, 109,
141, 213, 78, 169, 108, 86, 244, 234, 101, 122,
174, 8, 186, 120, 37, 46, 28, 166, 180, 198,
232, 221, 116, 31, 75, 189, 139, 138, 112, 62,
181, 102, 72, 3, 246, 14, 97, 53, 87, 185,
134, 193, 29, 158, 225, 248, 152, 17, 105, 217,
142, 148, 155, 30, 135, 233, 206, 85, 40, 223,
140, 161, 137, 13, 191, 230, 66, 104, 65, 153,
45, 15, 176, 84, 187, 22
)
Sbox_inv = None
@staticmethod
def rot_word(word):
return word[1:] + word[:1]
@staticmethod
def sub_word(word):
return (AES.Sbox[b] for b in word)
def key_schedule(self):
expanded = []
expanded.extend(list(self.key))
for i in range(self.nk, self.nb * (self.nr + 1)):
t = expanded[(i-1)*4:i*4]
if i % self.nk == 0:
t = xor( AES.sub_word( AES.rot_word(t) ), (AES.Rcon[i // self.nk],0,0,0) )
elif self.nk > 6 and i % self.nk == 4:
t = AES.sub_word(t)
expanded.extend( xor(t, expanded[(i-self.nk)*4:(i-self.nk+1)*4]))
return expanded
def add_round_key(self, rkey):
for i, b in enumerate(rkey):
self.state[i] ^= b
def sub_bytes(self):
for i, b in enumerate(self.state):
self.state[i] = AES.Sbox[b]
def inv_sub_bytes(self):
for i, b in enumerate(self.state):
self.state[i] = AES.Sbox_inv[b]
def shift_rows(self):
rows = []
for r in range(4):
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