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[原创]网刃杯逆向wp
2021-9-14 15:51 16909

[原创]网刃杯逆向wp

2021-9-14 15:51
16909

re1

根据常数搜索到Sm3,然后爆破就行。

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ss = ['6b8575c6092240cde08414dafd535bee', 'f0f659f2951290ad5e076b3fe5e70425', 'c1d6c663570de9fad13ddef955d8a02b', '14c4e442fba6d820ea90ae73ed90ad83', '25d997669868d0cf89782349256efb33', '78b1ea6bb1ac10287864c8f52d2758b6', '67d1259c26765356ddb58c6faf28080c', 'c1e14e0c86f55ba1d74b35b66f96ad36', '3e4f3ee942d1a57182e24df201b7022b', 'c35557f7e5c389061fb2e2ffa1a644ad', '15593844fae18fe1a25f3a9017c73810', 'c6c21ca591a63755fd77bf5c55a0238a', 'f90cb529875e83cc191c0e10ead6f73e', '3ddbe25f9b183c3e2c33c3b1e501fcd8', '30fdf04c347f1d4e335bda670d54eaaf', '33feb100c8c7c3769af6e9d26486c646']
m = '77'
IV='7380166f4914b2b9172442d7da8a0600a96f30bc163138aae38dee4db0fb0e4e'
#填充函数
def filling(m):
    #消息m是一个16进制字符串
    #直接加16进制比较好
    #61626364616263646162636461626364616263646162636461626364616263646162636461626364616263646162636461626364616263646162636461626364
 
    #a = int(m,16)
    #b = bin(a)[2:]#消息转换为二进制
    length_b = len(m)*4#记录消息的长度
    #s1='{:04b}'.format(s1)
    b = m
    b = b + '8'#补 1
    c = len(b)%128
    c = 112 - c#补 0 的个数
    d = '0'*c
    b = b + d#补 0
    length_m = '{:016x}'.format(length_b)#也是16进制
    b = b + length_m#填充完毕
    #b = int(b)
    #b = hex(b)[2:]
    return b
 
#分组函数
def fenzu(m):
    m = filling(m)
    len_m = len(m)/128
    m_list = []
    for i in range(int(len_m)):
        a = m[0+128*i:+128*(i+1)]
        m_list.append(a)
    return m_list
 
#扩展函数
def expand(m,n):#n代表是第几组消息,消息之间没有关系,不用迭代
    B = fenzu(m)#列表
    W = ['0' for i in range(68)]
    W_0 = ['0' for i in range(64)]
    for i in range(int(len(B[n])/8)):#128/8=16个字
        w = B[n][i*8:(i+1)*8]
        W[i] = w
    for j in range(16,68):
        a = or_16(W[j-16],W[j-9])
 
        W_j_3 = Cyc_shift(W[j-3],15)
        #print(W_j_3)
        a = or_16(a,W_j_3)
 
        a = Replace_P1(a)
        #print(a)
        W_j_13=Cyc_shift(W[j-13],7)
        a = or_16(a,W_j_13)
        a = or_16(a,W[j-6])
        W[j]=a
    #return W
    for j in range(64):
        W_0[j]=or_16(W[j],W[j+4])
    return W,W_0
 
#置换函数
def Replace_P1(X):
    #X为32位字
    X_15 = Cyc_shift(X,15#循环移位
    X_23 = Cyc_shift(X,23)
    a = or_16(X,X_15)
    a = or_16(a,X_23)
    return a
 
#置换函数
def Replace_P0(X):
    #X为32位字
    X_9 = Cyc_shift(X,9)
    X_17 = Cyc_shift(X,17)
    a = or_16(X,X_9)
    a = or_16(a,X_17)
    return a
 
#异或函数
def or_16(A,B):
    A = int(A,16)
    B = int(B,16)
    C = A ^ B
    C = '{:08x}'.format(C)
    return C
 
#循环移位函数
def Cyc_shift(W,n):
    a = int(W,16)
    a = '{:032b}'.format(a)
    while n>=32:
        n=n-32
    a = a[n:] + a[:n]
    a = int(a,2)
    a = '{:08x}'.format(a)
    return a
 
#常量Tj
def T_j(j):
    if j<=15:
        T_j='79cc4519'
    else:
        T_j='7a879d8a'
    return T_j
 
#mod 2^32 算术加运算
def add(x,y):
    x = int(x,16)
    x = '{:032b}'.format(x)
    x = list(x)
    y = int(y, 16)
    y = '{:032b}'.format(y)
    y = list(y)
    #print(x)
    #print(y)
    a = [0 for _ in range(32)]
    carry = 0
    for i in range(32):
        m = int(x[31-i])+int(y[31-i])+carry
        if m>=2:
            d=m-2
            a[31-i]=str(d)
            carry=1
        else:
            carry=0
            d=m
            a[31 - i] = str(d)
    #print(a)
    b=''.join(a)
    b=int(b,2)
    b='{:08x}'.format(b)
    return b
 
#布尔函数
def FF_j(X,Y,Z,j):
    if j<=15:
        a = or_16(X,Y)
        a = or_16(a,Z)
    else:
        a = and_Cal(X,Y)
        b = and_Cal(X,Z)
        c = and_Cal(Y,Z)
        a = or_Cal(a,b)
        a = or_Cal(a,c)
    return a
 
#布尔函数
def GG_j(X, Y, Z, j):
    if j <= 15:
        a = or_16(X, Y)
        a = or_16(a, Z)
    else:
        a = and_Cal(X,Y)
        b = qufan(X)
        b = and_Cal(b,Z)
        a = or_Cal(a,b)
    return a
 
#与运算函数
def and_Cal(a,b):
    a = int(a,16)
    b = int(b,16)
    a_b = a & b
    a_b = '{:08x}'.format(a_b)
    return a_b
 
#或运算函数
def or_Cal(a,b):
    a = int(a, 16)
    b = int(b, 16)
    a_b = a | b
    a_b = '{:08x}'.format(a_b)
    return a_b
 
#按位取反函数
def qufan(A):
    A = int(A,16)
    A = '{:032b}'.format(A)
    A = list(A)
    for i in range(32):
        if A[i]=='0':
            A[i]='1'
        else:
            A[i]='0'
    A = ''.join(A)
    A = int(A,2)
    A = '{:08x}'.format(A)
    return A
 
#压缩函数
m_list = fenzu(m)
m_len = len(m_list)
V = ['0' for i in range(m_len+1)]
V[0]=IV
 
#压缩函数
def CF(m,n,k):
    w = expand(m, n)
    W = w[0]
    W_0 = w[1]
    A=V[k][0:8]
    B=V[k][8:16]
    C=V[k][16:24]
    D=V[k][24:32]
    E=V[k][32:40]
    F=V[k][40:48]
    G=V[k][48:56]
    H=V[k][56:64]
    #print(W_0)
    all=''
    for j in range(64):
        #print(E)
        b= a = Cyc_shift(A,12)
        #t = b
        T = T_j(j)
        #
        T = Cyc_shift(T,j)#忘记移位了,移位问题
        a = add(a,E)
        a = add(a,T)
        SS1 = Cyc_shift(a,7)
        SS2 = or_16(SS1,b)
        b = FF_j(A,B,C,j)
        b = add(b,D)
        b = add(b,SS2)
        TT1 = add(b,W_0[j]) #
        b = GG_j(E,F,G,j)
        b = add(b, H)
        b = add(b, SS1)
        TT2 = add(b, W[j]) #
        D = C
        C = Cyc_shift(B,9)
        B = A
        A = TT1#
        H = G
        G = Cyc_shift(F,19)
        F = E
        E = Replace_P0(TT2) #
        all = A+B+C+D+E+F+G+H
        #print(all)
    #V[k+1]=or_16(all,V[k])
    #return V[k+1]
    #print(t)
    #return all
    V[k+1]=or_16(V[k],all)
 
#print(CF(m,0,0))
#print(V)
def hash(m=m):
    for i in range(m_len):
        v_n=CF(m,i,i)
    #print(V[-1])
    return V[-1]
 
#b=''
#b=a[0:8]+'\0'+a[8:16]+'\0'+a[16:24]+'\0'+a[24:32]+'\0'+a[32:40]+'\0'+a[40:48]+'\0'+a[48:56]+'\0'+a[56:64]
#print(b)
flag = ""
ttt = ""
for j in range(len(ss)):
    for i in range(0xff):
        arg = ttt + hex(i)[2:].rjust(2,"0")
        res = hash(m=arg)[:32]
        #print(res, i)
        if res == ss[j]:
            flag += chr(i)
            ttt += hex(i)[2:].rjust(2,"0")
            print(flag)
            break
#print('输入的消息m是:\n',m)
#print('消息m的hash值为:\n',b)

re2

本来用unicorn可以秒这道题,但是不知道我多蠢,模拟了一个自己patch过的文件,导致没跑出来,解出这个题之后才发觉,所以写两种方法。

 

两个地方反调试:

 

图片描述

 

这里也需要过跳转:

 

图片描述

 

关键地方就是check分数,得到正确的分数进行简单计算即可:

 

图片描述

 

要得到score,patch反调试,然后程序内改汇编进行爆破。

 

.text:00992388 90 nop
.text:00992389
.text:00992389 loc_992389: ; CODE XREF: sub_992290+12C↓j
.text:00992389 8B 8D 68 FF FF FF mov ecx, [ebp+var_98]
.text:0099238F 8B 01 mov eax, [ecx+0]
.text:00992391 83 C0 01 add eax, 1
.text:00992394 89 01 mov [ecx], eax
.text:00992396 89 41 4C mov [ecx+4Ch], eax
.text:00992399 90 nop
.text:0099239A 90 nop
.text:0099239B 90 nop
.text:0099239C 90 nop

 

拿到分数。

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v12 = 0x2100
flag = ""
a1 = 0x2100 ^ 0xAC0B
 
while(v12):
    v9 = v12 % 8 + 48
    flag += chr(v9)
    v12 //= 8
print("flag{" + "b0d8" + flag + "}")

unicorn模拟程序爆破解法:

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from unicorn import *
from unicorn.x86_const import *
from pwn import *
 
score = 0
def read(name):
    with open(name,"rb") as fp:
        return fp.read()
def hook_code(mu, address, size, user_data):
    #print('>>> Tracing instruction at 0x%x, instruction size = 0x%x' % (address, size))
    #bytes = mu.mem_read(address, 20)
    #print('地址:%x, 内容:%s' % (address, binascii.b2a_hex(bytes)))
 
    if address == 0x4017ac:
        mu.reg_write(UC_X86_REG_EAX, 0x500000)
        mu.reg_write(UC_X86_REG_ECX, 0x500000)
        mu.reg_write(UC_X86_REG_EIP, 0x4017b2)
    if address == 0x401c2f:
        eax = mu.reg_read(UC_X86_REG_EAX)
        result = u32(mu.mem_read(BASE+0x10004c,4))
        if eax == 0x1a8cd:
            print("score: " + hex(result))
            global score
            score = result
            mu.reg_write(UC_X86_REG_EIP, 0x401c31)
        else:
            mu.mem_write(BASE+0x10004c, p32(result+1))
            mu.reg_write(UC_X86_REG_EIP, 0x4017ac)
 
# 模拟器开始的内存地址
BASE = 0x400000
STACK_ADDR = 0Xf00000
#栈大小
STACK_SIZE = 1024 * 1024  # 1MB
 
print("Emulate revers2.exe:")
try:
    #初始化模拟器为x86_32
    mu = Uc(UC_ARCH_X86, UC_MODE_32)
    #为这个模拟器分配1M内存
    mu.mem_map(BASE, 2 * 1024 * 1024, UC_PROT_ALL)
    mu.mem_map(STACK_ADDR, STACK_SIZE)
    #将程序内容写入内存
    mu.mem_write(BASE, read("./revers2.exe"))
    mu.mem_write(BASE+0x10004c, b"\x00\x00\x00\x00")
    mu.mem_write(0x40733c, b"\x00\x00\x00\x3f\x00\x00\xc0\x3f\x00\x00\xa0\x40\x00\x00\x20\x41\x80\x96\x18\x4b")
    mu.reg_write(UC_X86_REG_ESP, STACK_ADDR + STACK_SIZE - 1)
    mu.hook_add(UC_HOOK_CODE, hook_code)
    mu.emu_start(0x4017ac, 0x401c31)
 
except UcError as e:
    print("ERROR: %s" % e)
 
flag = ""
a1 = score ^ 0xAC0B
while(score):
    v9 = score % 8 + 48
    flag += chr(v9)
    score //= 8
print("flag{" + ''.join(reversed(list(hex(a1)[2:]))) + flag + "}")

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