2014/07/18 10:53 12,800 aplib.dll
2. 提取pyc， 反编译py文件
2.1 解压CM.exe ，得到1个python 打包的exe。 用IDA静态分析了一把，然后下断点调试，里面有aPsafe_depack()， 从0x8000 偏移量开始， 解压了 0x28131 字节 (164145 字节)， 解压到0x140000000， 解压后的size是2734080 bytes，也就是267 KB。
2.2 这个dump_267k_bin.exe，看了一番， 发现是python编译pyc，然后打包做成的exe。然后发现CM.exe每次启动，会开启一个新的进程CM。
C:\Python37\Lib\site-packages\PyInstaller\utils\cliutils>archive_viewer.py D:\work\pediy_2019_ctf\2019q4\02-tea-ZhongyaRing\tea1\CM.exe
pos, length, uncompressed, iscompressed, type, name
[(0, 252, 326, 1, 'm', 'struct'),
(252, 1104, 1807, 1, 'm', 'pyimod01_os_path'),
(1356, 4372, 9350, 1, 'm', 'pyimod02_archive'),
(5728, 7422, 18670, 1, 'm', 'pyimod03_importers'),
(13150, 1863, 4171, 1, 's', 'pyiboot01_bootstrap'),
(15013, 754, 1178, 1, 's', 'CM'),
(15767, 480, 1027, 1, 'b', 'CM.exe.manifest'),
(16247, 20112, 36352, 1, 'b', 'Crypto\\Cipher\\_AES.cp37-win_amd64.pyd'),
(36359, 7603, 15872, 1, 'b', 'Crypto\\Hash\\_SHA256.cp37-win_amd64.pyd'),
(2406251, 1598380, 3745280, 1, 'b', 'python37.dll'),
(4004631, 49687, 137216, 1, 'b', 'pywintypes37.dll'),
... 省略若干行 ...
(5002231, 0, 0, 0, 'o', 'pyi-windows-manifest-filename CM.exe.manifest'),
(5002231, 214384, 781191, 1, 'x', 'base_library.zip'),
(5216615, 1467669, 1467669, 0, 'z', 'PYZ-00.pyz')]
?
U: go Up one level
O <name>: open embedded archive name
X <name>: extract name
Q: quit
? X CM
to filename? CM.pyc
? O PYZ-00.pyz
Name: (ispkg, pos, len)
{'CMpub': (0, 17, 2250),
'Crypto': (1, 2267, 597),
... 省略若干行 ...
'general': (0, 387075, 918),
'genericpath': (0, 387993, 1775),
'getopt': (0, 389768, 3121),
... 省略若干行 ...
'xml.sax.xmlreader': (0, 1431869, 5400),
'zipfile': (0, 1437269, 23205)}
?
U: go Up one level
O <name>: open embedded archive name
X <name>: extract name
Q: quit
? X CMpub
to filename? CMpub.pyc
? X general
to filename? general.pyc
?
step 2
: 修复pyc；
C:\Python37\Lib\site-packages\PyInstaller\utils\cliutils>archive_viewer.py D:\work\pediy_2019_ctf\2019q4\02-tea-ZhongyaRing\tea1\CM.exe
pos, length, uncompressed, iscompressed, type, name
[(0, 252, 326, 1, 'm', 'struct'),
(252, 1104, 1807, 1, 'm', 'pyimod01_os_path'),
(1356, 4372, 9350, 1, 'm', 'pyimod02_archive'),
(5728, 7422, 18670, 1, 'm', 'pyimod03_importers'),
(13150, 1863, 4171, 1, 's', 'pyiboot01_bootstrap'),
(15013, 754, 1178, 1, 's', 'CM'),
(15767, 480, 1027, 1, 'b', 'CM.exe.manifest'),
(16247, 20112, 36352, 1, 'b', 'Crypto\\Cipher\\_AES.cp37-win_amd64.pyd'),
(36359, 7603, 15872, 1, 'b', 'Crypto\\Hash\\_SHA256.cp37-win_amd64.pyd'),
(2406251, 1598380, 3745280, 1, 'b', 'python37.dll'),
(4004631, 49687, 137216, 1, 'b', 'pywintypes37.dll'),
... 省略若干行 ...
(5002231, 0, 0, 0, 'o', 'pyi-windows-manifest-filename CM.exe.manifest'),
(5002231, 214384, 781191, 1, 'x', 'base_library.zip'),
(5216615, 1467669, 1467669, 0, 'z', 'PYZ-00.pyz')]
?
U: go Up one level
O <name>: open embedded archive name
X <name>: extract name
Q: quit
? X CM
to filename? CM.pyc
? O PYZ-00.pyz
Name: (ispkg, pos, len)
{'CMpub': (0, 17, 2250),
'Crypto': (1, 2267, 597),
... 省略若干行 ...
'general': (0, 387075, 918),
'genericpath': (0, 387993, 1775),
'getopt': (0, 389768, 3121),
... 省略若干行 ...
'xml.sax.xmlreader': (0, 1431869, 5400),
'zipfile': (0, 1437269, 23205)}
?
U: go Up one level
O <name>: open embedded archive name
X <name>: extract name
Q: quit
? X CMpub
to filename? CMpub.pyc
? X general
to filename? general.pyc
?
step3: uncompyle6 反编译pyc，最后得到3个文件：
3. 分析算法， 分解 RSA Numbers
发现CMpub里有10组768 bits的 RSA-N 和 E， 记作 n[0] ~ n[9] , e[0] ~ e[9]。 其中n[0], e[0]又被分成4组192 bit的small n使用。
修改CM.py 让它打印中间过程数据，判定出算法主要流程：
一直在想：作者的成语接龙，循环的脑洞是什么？ 以为9个n有什么联系， 比如前一个n的Low Bits 和后一个n的 High Bits能连起来，最终形成一个圈。
这时候碰巧也搜到关键字： cycling attack RSA 或者 Cycle attack on RSA 的网页。
就是拿e，n 不断循环powmod，密文循环若干次，能得到明文。
试了一下3000次循环， 发现存在固定周期973。伪代码：
/// find cycle ////
int maxk = 3000;
Big c0 = rand();
Big c = c0;
int i = 5;
for(int j = 1; j <= maxk; j++)
{
c = pow(c, e[i], n[i]);
// k = 973
if(c == c0)
{
printf("c = c0, find i= %d, j = %d\n", i, j);
}
if(c == 1)
{
printf("c = 1, find i= %d, j = %d\n", i, j);
}
}
就考虑， 那么就是 e*d = e^973 满足 e*d = 1 mod (lcm(p-1)*(q-1)) , 从而可用的 d=e^972
但是这个d太大了， 不方便。所以还是得从 e,d 分解出n， 求得合适的 d < n才好。
/// find cycle ////
int maxk = 3000;
Big c0 = rand();
Big c = c0;
int i = 5;
for(int j = 1; j <= maxk; j++)
{
c = pow(c, e[i], n[i]);
// k = 973
if(c == c0)
{
printf("c = c0, find i= %d, j = %d\n", i, j);
}
if(c == 1)
{
printf("c = 1, find i= %d, j = %d\n", i, j);
}
}
方法一： 原理可以参考 我2017年的贴：
///// method 1 ////////////
// find w^2 = 1 mod n, then gcd(w + 1, n) = p or gcd(w - 1, n) = p
printf("for p[5]， method 1 \n", tm);
tm = time(NULL);
ek973 = pow(e[5], 973);
ed = ek973 - 1; // k*phi = ed - 1
int s = 0;
while(ed % 2 == 0)
{
s++;
ed /= 2;
}
printf("s=%d, get: ed - 1 = r * 2^s \n", s);
find = 0;
for(int t = 2; t <= 7; t++) // try t=2, 3, 4, 5 ,...
{
w = pow(t, ed, n[5]);
int is = 0;
while(is < s)
{
is++;
w = pow(w, 2, n[5]);
Big p = gcd(w + 1, n[5]);
if(p > 1)
{
char buf[1024] = {0};
printf("try t =%d, s = %d ,get p\n", t, s);
buf << p;
printf("%s\n", buf);
find = 1;
break;
}
}
if(find == 1)
break;
}
tm = time(NULL) - tm;
printf("method 1, time cost: %d seconds\n\n", tm);
///// method 1 ////////////
// find w^2 = 1 mod n, then gcd(w + 1, n) = p or gcd(w - 1, n) = p
printf("for p[5]， method 1 \n", tm);
tm = time(NULL);
ek973 = pow(e[5], 973);
ed = ek973 - 1; // k*phi = ed - 1
int s = 0;
while(ed % 2 == 0)
{
s++;
ed /= 2;
}
printf("s=%d, get: ed - 1 = r * 2^s \n", s);
find = 0;
for(int t = 2; t <= 7; t++) // try t=2, 3, 4, 5 ,...
{
w = pow(t, ed, n[5]);
int is = 0;
while(is < s)
{
is++;
w = pow(w, 2, n[5]);
Big p = gcd(w + 1, n[5]);
if(p > 1)
{
char buf[1024] = {0};
printf("try t =%d, s = %d ,get p\n", t, s);
buf << p;
printf("%s\n", buf);
find = 1;
break;
}
}
if(find == 1)
break;
}
tm = time(NULL) - tm;
printf("method 1, time cost: %d seconds\n\n", tm); [招生]科锐逆向工程师培训(2024年11月15日实地，远程教学同时开班, 第51期)
最后于 2019-12-9 16:27
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