2018强网杯记录
1 签到题
2welcome
下载文件，发现是一个BMP图片文件。
于是使用Stegsolve工具分离，发现，得到flag
3 streamgame1
上脚本1
#! /usr/bin/env python3
# coding:utf8
def lfsr(R,mask):
output = (R << 1) & 0xffffff
i=(R&mask)&0xffffff
lastbit=0
while i!=0:
lastbit^=(i&1)
i=i>>1
output^=lastbit
return (output,lastbit)
mask = 0b1010011000100011100
f=open("./key","rb")
c=f.read()
f.close()
count = -1
while count <= 0b1111111111111111111:
count += 1
print(count)
R = count
for i in range(12):
tmp=0
for j in range(8):
(R,out)=lfsr(R,mask)
tmp=(tmp << 1)^out
if tmp != c[i]:
break
if i == 11:
print('succeed')
print('flag{%s}' % bin(count)[2:])
exit(0)
4 streamgame2
上脚本2
#! /usr/bin/env python3
# coding:utf8
def lfsr(R,mask):
output = (R << 1) & 0xffffff
i=(R&mask)&0xffffff
lastbit=0
while i!=0:
lastbit^=(i&1)
i=i>>1
output^=lastbit
return (output,lastbit)
mask = 0x100002
f=open("./key","rb")
c=f.read()
f.close()
count = -1
while count <= 0b111111111111111111111:
count += 1
if count % 10000 == 0:
print(count)
R = count
for i in range(12):
tmp=0
for j in range(8):
(R,out)=lfsr(R,mask)
tmp=(tmp << 1)^out
if tmp != c[i]:
break
if i == 11:
print('succeed')
print('flag{%s}' % bin(count)[2:])
exit(0)
5 streamgame4
上脚本3
#! /usr/bin/env python3
# coding:utf8
def lfsr(R,mask):
output = (R << 1) & 0xffffff
i=(R&mask)&0xffffff
lastbit=0
while i!=0:
lastbit^=(i&1)
i=i>>1
output^=lastbit
return (output,lastbit)
mask = 0b1010011000100011100
f=open("./key","rb")
c=f.read()
f.close()
count = -1
while count <= 0b1111111111111111111:
count += 1
#print(count)
R = count
for i in range(12):
tmp=0
for j in range(8):
(R,out)=lfsr(R,mask)
tmp=(tmp << 1)^out
if tmp != c[i]:
break
if i == 11:
print('succeed')
print('flag{%s}' % bin(count)[2:])
exit(0)
6 web签到题
因为每次在网页里，都有网页代码的提示，三次都是绕过。
第一次绕过是利用php，==的弱等于
240610708 和 QNKCDZO
第二次：传递数组，越过
第三次：利用碰撞试验，
d131dd02c5e6eec4693d9a0698aff95c2fcab58712467eab4004583eb8fb7f89
55ad340609f4b30283e488832571415a085125e8f7cdc99fd91dbdf280373c5b
d8823e3156348f5bae6dacd436c919c6dd53e2b487da03fd02396306d248cda0
e99f33420f577ee8ce54b67080a80d1ec69821bcb6a8839396f9652b6ff72a70
AND
d131dd02c5e6eec4693d9a0698aff95c2fcab50712467eab4004583eb8fb7f89
55ad340609f4b30283e4888325f1415a085125e8f7cdc99fd91dbd7280373c5b
d8823e3156348f5bae6dacd436c919c6dd53e23487da03fd02396306d248cda0
e99f33420f577ee8ce54b67080280d1ec69821bcb6a8839396f965ab6ff72a70
7 simple check
反编译apk，获得java代码，明白了是对字符串的判定。
public class a
{
private static int[] a = { 0, 146527998, 205327308, 94243885, 138810487, 408218567, 77866117, 71548549, 563255818, 559010506, 449018203, 576200653, 307283021, 467607947, 314806739, 341420795, 341420795, 469998524, 417733494, 342206934, 392460324, 382290309, 185532945, 364788505, 210058699, 198137551, 360748557, 440064477, 319861317, 676258995, 389214123, 829768461, 534844356, 427514172, 864054312 };
private static int[] b = { 13710, 46393, 49151, 36900, 59564, 35883, 3517, 52957, 1509, 61207, 63274, 27694, 20932, 37997, 22069, 8438, 33995, 53298, 16908, 30902, 64602, 64028, 29629, 26537, 12026, 31610, 48639, 19968, 45654, 51972, 64956, 45293, 64752, 37108 };
private static int[] c = { 38129, 57355, 22538, 47767, 8940, 4975, 27050, 56102, 21796, 41174, 63445, 53454, 28762, 59215, 16407, 64340, 37644, 59896, 41276, 25896, 27501, 38944, 37039, 38213, 61842, 43497, 9221, 9879, 14436, 60468, 19926, 47198, 8406, 64666 };
private static int[] d = { 0, -341994984, -370404060, -257581614, -494024809, -135267265, 54930974, -155841406, 540422378, -107286502, -128056922, 265261633, 275964257, 119059597, 202392013, 283676377, 126284124, -68971076, 261217574, 197555158, -12893337, -10293675, 93868075, 121661845, 167461231, 123220255, 221507, 258914772, 180963987, 107841171, 41609001, 276531381, 169983906, 276158562 };
public static boolean a(String paramString)
{
if (paramString.length() != b.length) {
return false;
}
int[] arrayOfInt = new int[a.length];
arrayOfInt[0] = 0;
paramString = paramString.getBytes();
int k = paramString.length;
int i = 0;
int j = 1;
while (i < k)
{
arrayOfInt[j] = paramString[i];
j += 1;
i += 1;
}
i = 0;
for (;;)
{
if (i >= c.length) {
break label166;
}
if ((a[i] != b[i] * arrayOfInt[i] * arrayOfInt[i] + c[i] * arrayOfInt[i] + d[i]) || (a[(i + 1)] != b[i] * arrayOfInt[(i + 1)] * arrayOfInt[(i + 1)] + c[i] * arrayOfInt[(i + 1)] + d[i])) {
break;
}
i += 1;
}
label166:
return true;
}
}
首先是判定字符串长度是否为34，然后是对字符串进行双位判定。写出脚本，得到flag
a = [0, 146527998, 205327308, 94243885, 138810487, 408218567, 77866117, 71548549, 563255818, 559010506, 449018203,
576200653, 307283021, 467607947, 314806739, 341420795, 341420795, 469998524, 417733494, 342206934, 392460324,
382290309, 185532945, 364788505, 210058699, 198137551, 360748557, 440064477, 319861317, 676258995, 389214123,
829768461, 534844356, 427514172, 864054312]b = [13710, 46393, 49151, 36900, 59564, 35883, 3517, 52957, 1509, 61207, 63274, 27694, 20932, 37997, 22069, 8438, 33995,
53298, 16908, 30902, 64602, 64028, 29629, 26537, 12026, 31610, 48639, 19968, 45654, 51972, 64956, 45293, 64752,
37108]c = [38129, 57355, 22538, 47767, 8940, 4975, 27050, 56102, 21796, 41174, 63445, 53454, 28762, 59215, 16407, 64340,
37644, 59896, 41276, 25896, 27501, 38944, 37039, 38213, 61842, 43497, 9221, 9879, 14436, 60468, 19926, 47198, 8406,
64666]d = [0, -341994984, -370404060, -257581614, -494024809, -135267265, 54930974, -155841406, 540422378, -107286502,
-128056922, 265261633, 275964257, 119059597, 202392013, 283676377, 126284124, -68971076, 261217574, 197555158,
-12893337, -10293675, 93868075, 121661845, 167461231, 123220255, 221507, 258914772, 180963987, 107841171, 41609001,
276531381, 169983906, 276158562]arrayOfInt = []print()for i in range (0, a.__len__()-1):
arrayOfInt.append(int((-c[i] + (c[i] ** 2 - 4 * b[i] * (d[i] - a[i])) ** 0.5) / 2 / b[i]))
print(int((-c[i] + (c[i] ** 2 - 4 * b[i] * (d[i] - a[i])) ** 0.5) / 2 / b[i]),end=',')answer = bytes(arrayOfInt)print(answer)
answer = str(answer)print(answer[0:36])
print('flag{MAth_i&_GOOd_DON7_90V_7hInK?}'.__len__())
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