比賽感受
這次比賽難度很大（應該是我太菜。。。），把我整得懷疑人生，很多題不會，尤其是逆向。最近也有點忙，拖到今天才寫好wp。。。大佬輕噴
Misc
簽到
直接base64解碼得到flag
進制反轉
壓縮包解壓失敗
題目提示說到手機，以為用手機就能解壓，手機沒有出現損壞的提示，但是解壓需要密碼（其實這里就掉坑了。。。）
010打開壓縮包，先遍歷看看有無可疑信息，沒有發現，猜測可能為rar偽加密，因為rar的機制，使用偽加密打開會出錯，找到第24個字節，將C4改為C0，解壓成功
發現一個音頻flag.wav，使用Audacity打開，失敗
使用導入原始數據的方式打開這個音頻文件，聽不懂，結合提示的反轉，可能是倒放，並調節速率
聽起來好像是一首歌，聽歌識曲為： 《Too Good At Goodbyes》
flag就是這個歌名，題目要求大寫，flag就是歌名的大寫
到點了
題目給了三個docx文件，先從第一個文檔開始看，打開是這樣
沒有什么有效信息，可能被隱藏，勾上隱藏字體看看
第二個文檔被加密，這個應該就是線索
暴力破解，得到密碼為20201024（沒有字母，出題人真坑！），打開第二個文檔
因為我不喜歡白色背景，很久前我就把背景設為綠色，好家伙，居然發現圖片下面有一行東西（巧了，瞎貓碰見死耗子。。。），復制出來
AABBAABBBAABBBAAAABBABBABABAAAAABBAAABBBBAABBBAABABABBAAABAAAABAABAABBABAAAAABAA
培根密碼解密得到
GOODNIGHTSWEETIE
goodnightsweetie
第三個文檔很顯然，比其他兩個文檔大很多，里面可能有其他文件，使用foremost分解
發現一個壓縮包，但是沒有分解出來，只分解出兩個圖片
使用binwalk分解，分解后得到一大堆東西
那個4.zip是之前foremost發現的壓縮文件，里面是一張bmp文件，嘗試 wbs43open
輸入之前培根密碼解密得到的兩個密碼，發現GOODNIGHTSWEETIE，才是真的密碼
xixixi
題目提示：室友最近沉迷y神，又氪又肝，還ghs。為了他的身體着想，我把他的s圖整沒了。但我明明刪了腳本啊，為什么還能被他發現......8說了，醫院的空調真舒服~（真的是沉迷y神。。。）
解壓得到vhd文件，就是虛擬磁盤文件，用window系統自帶的磁盤管理附加就可以
里面是一張圖片
看圖片的話，好像是菲謝爾~，除此之外，沒有其他信息。。。可能姿勢不對
帶音樂家
題目給了兩個文件
先分析一下decode_it是什么文件類型
以前看過一個編程語言Veloto就是以這種文件作為源代碼的，嘗試編譯后看看輸出什么
打開壓縮包
注釋那里有東西，但是看不到，復制到編輯器
好家伙，還是看不到，不過能通過光標的移動猜出就是點和橫線，摩斯密碼，通過光標一個一個測出來，並摩斯密碼解密得到信息是
AESKEY9219232322
壓縮包有密碼，密碼為:Hello, World!，打開里面的文檔
根據前面的信息，這個應該就是AES加密，密鑰是9219232322
在線網站解密得到flag:flag{mU51c_And_ch@ract0rs~}
charles Sensor
暫無思路
Reverse
re1
ida載入，搜索字符串，搜到win，定位到引用的函數，反匯編失敗，直接卡住。。。
看看匯編代碼，發現判斷的函數特別長，而且很多跳轉，直接看最后的win那里，因為flag正確的話就會走到這里，根據前面的判斷，flag由flag{xxx}，xxx就是我們要求出的內容，並且flag長度為32
這里有很多的字符比較，全部都符合就輸出win，那么可以直接爆破出結果，但是要先判斷是如何進行加密的，輸入32個字符flag{0123456789abcdefghijklmnopqrstuv}進行動態調試，發現
0被加密為：0xe8
...
9被加密為：0xf1
a被加密為：0x19
...
計算各自偏移了多少，如下圖
爆破腳本如下：
a = [0xeb,0xf1,0x19,0xe8,0x1e,0x1e,0xf0,0xec,0xef,0x1e,0xe9,0x1e,0xec,0xec,0xe8,0xec,0x19,0x19,0xee,0x1b,0xef,0xef,0xec,0xea,0x1c,0xea,0xe8,0xeb,0xee,0xeb,0x1d,0xf1]
flag = ""
for i in range(len(a)):
if 0xe8 <= a[i] <= 0xf1:
flag += chr(a[i]-184)
if 0x19 <= a[i] <= (0x19+26):
flag += chr(a[i]+72)
flag = 'flag{'+flag+'}'
print(flag)
apk1
安卓的逆向，環境問題，反匯編失敗，待研究
其他
暫無思路，懷疑人生
Crypto
simpleRsa
題目給了一個python文件和數據文件，我把相關數據移到python文件
from Crypto.Util.number import *
import gmpy2
p, q, r = [getPrime(512) for i in range(3)]
n = p * q * r
phi = (p - 1) * (q - 1) * (r - 1)
d = getPrime(256)
e = gmpy2.invert(d , phi)
flag = b"flag{xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx}"
c = pow(bytes_to_long(flag), e, n)
print(e, n)
print(c)
e = 1072295425944136507039938677101442481213519408125148233880442849206353379681989305000570387093152236263203395726974692959819315410781180094216209100069530791407495510882640781920564732214327898099944792714253622047873152630438060151644601786843683746256407925709702163565141004356238879406385566586704226148537863811717298966607314747737551724379516675376634771455883976069007134218982435170160647848549412289128982070647832774446345062489374092673169618836701679
n = 1827221992692849179244069834273816565714276505305246103435962887461520381709739927223055239953965182451252194768935702628056587034173800605827424043281673183606478736189927377745575379908876456485016832416806029254972769617393560238494326078940842295153029285394491783712384990125100774596477064482280829407856014835231711788990066676534414414741067759564102331614666713797073811245099512130528600464099492734671689084990036077860042238454908960841595107122933173
c = 1079929174110820494059355415059104229905268763089157771374657932646711017488701536460687319648362549563313125268069722412148023885626962640915852317297916421725818077814237292807218952574111141918158391190621362508862842932945783059181952614317289116405878741758913351697905289993651105968169193211242144991434715552952340791545323270065763529865010326192824334684413212357708275259096202509042838081150055727650443887438253964607414944245877904002580997866300452
和常見的RSA不一樣，n是三個素數相乘。d比較小，造成e很大，很接近n，第一印象是使現成的維納攻擊，但是攻擊失敗，可能是因為三個素數造成
轉換思路，使用 連分數展開並求其各項漸進分數，來求私鑰，代碼如下：
from Crypto.Util.number import *
e = 1072295425944136507039938677101442481213519408125148233880442849206353379681989305000570387093152236263203395726974692959819315410781180094216209100069530791407495510882640781920564732214327898099944792714253622047873152630438060151644601786843683746256407925709702163565141004356238879406385566586704226148537863811717298966607314747737551724379516675376634771455883976069007134218982435170160647848549412289128982070647832774446345062489374092673169618836701679
n = 1827221992692849179244069834273816565714276505305246103435962887461520381709739927223055239953965182451252194768935702628056587034173800605827424043281673183606478736189927377745575379908876456485016832416806029254972769617393560238494326078940842295153029285394491783712384990125100774596477064482280829407856014835231711788990066676534414414741067759564102331614666713797073811245099512130528600464099492734671689084990036077860042238454908960841595107122933173
c = 1079929174110820494059355415059104229905268763089157771374657932646711017488701536460687319648362549563313125268069722412148023885626962640915852317297916421725818077814237292807218952574111141918158391190621362508862842932945783059181952614317289116405878741758913351697905289993651105968169193211242144991434715552952340791545323270065763529865010326192824334684413212357708275259096202509042838081150055727650443887438253964607414944245877904002580997866300452
def transform(x,y):
res = []
while y:
res.append(x//y)
x,y = y,x%y
return res
def continued_fraction(res):
numerator,denominator = 1,0
for i in res[::-1]:
denominator,numerator = numerator,i*numerator+denominator
return numerator,denominator
def wiener_attack(res):
print("Attack start...")
for i in range(1,len(res)):
ress = res[:i]
d = continued_fraction(ress)[1]
m = long_to_bytes(pow(c,d,n))
if b'flag' in m:
print(m,"Success!")
break
res = transform(e,n)
wiener_attack(res)
more_calc
題目給了一個python文件，數據也在里面
import gmpy2
from Crypto.Util.number import *
flag = b"flag{xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx}"
p = getStrongPrime(2048)
for i in range(1, (p+1)//2):
s += pow(i, p-2, p)
s = s % p
q = gmpy2.next_prime(s)
n = p*q
e = 0x10001
c = pow(bytes_to_long(flag), e, n)
print(p)
print(c)
#27405107041753266489145388621858169511872996622765267064868542117269875531364939896671662734188734825462948115530667205007939029215517180761866791579330410449202307248373229224662232822180397215721163369151115019770596528704719472424551024516928606584975793350814943997731939996459959720826025110179216477709373849945411483731524831284895024319654509286305913312306154387754998813276562173335189450448233216133842189148761197948559529960144453513191372254902031168755165124218783504740834442379363311489108732216051566953498279198537794620521800773917228002402970358087033504897205021881295154046656335865303621793069
#350559186837488832821747843236518135605207376031858002274245004287622649330215113818719954185397072838014144973032329600905419861908678328971318153205085007743269253957395282420325663132161022100365481003745940818974280988045034204540385744572806102552420428326265541925346702843693366991753468220300070888651732502520797002707248604275755144713421649971492440442052470723153111156457558558362147002004646136522011344261017461901953583462467622428810167107079281190209731251995976003352201766861887320739990258601550606005388872967825179626176714503475557883810543445555390014562686801894528311600623156984829864743222963877167099892926717479789226681810584894066635076755996423203380493776130488170859798745677727810528672150350333480506424506676127108526488370011099147698875070043925524217837379654168009179798131378352623177947753192948012574831777413729910050668759007704596447625484384743880766558428224371417726480372362810572395522725083798926133468409600491925317437998458582723897120786458219630275616949619564099733542766297770682044561605344090394777570973725211713076201846942438883897078408067779325471589907041186423781580046903588316958615443196819133852367565049467076710376395085898875495653237178198379421129086523
剛開始卡在求s那里，s就是1開始的逆元累加，我想化簡這個式子求出s，但是失敗。因為p已知，實際上求明文，題目條件已經可以求出來了（不需要s，q）
因為 p|n,所以m = c^d mod n 等價於 m = c^d mod p
因為 p-1 | Fai(n),所以 ed = 1 mod Fai(n) 等價於 ed = 1 mod (p-1)
又因為e，p已知，可以求出d，然后就可以求出m
完整代碼如下：
from Crypto.Util.number import*
from gmpy2 import *
p = 27405107041753266489145388621858169511872996622765267064868542117269875531364939896671662734188734825462948115530667205007939029215517180761866791579330410449202307248373229224662232822180397215721163369151115019770596528704719472424551024516928606584975793350814943997731939996459959720826025110179216477709373849945411483731524831284895024319654509286305913312306154387754998813276562173335189450448233216133842189148761197948559529960144453513191372254902031168755165124218783504740834442379363311489108732216051566953498279198537794620521800773917228002402970358087033504897205021881295154046656335865303621793069
c = 350559186837488832821747843236518135605207376031858002274245004287622649330215113818719954185397072838014144973032329600905419861908678328971318153205085007743269253957395282420325663132161022100365481003745940818974280988045034204540385744572806102552420428326265541925346702843693366991753468220300070888651732502520797002707248604275755144713421649971492440442052470723153111156457558558362147002004646136522011344261017461901953583462467622428810167107079281190209731251995976003352201766861887320739990258601550606005388872967825179626176714503475557883810543445555390014562686801894528311600623156984829864743222963877167099892926717479789226681810584894066635076755996423203380493776130488170859798745677727810528672150350333480506424506676127108526488370011099147698875070043925524217837379654168009179798131378352623177947753192948012574831777413729910050668759007704596447625484384743880766558428224371417726480372362810572395522725083798926133468409600491925317437998458582723897120786458219630275616949619564099733542766297770682044561605344090394777570973725211713076201846942438883897078408067779325471589907041186423781580046903588316958615443196819133852367565049467076710376395085898875495653237178198379421129086523
e = 0x10001
d = invert(e,p-1)
m = pow(c,d,p)
print long_to_bytes(m)
RSAssss
題目給了一個python文件和數據文件，我把數據移到python文件那里
from Crypto.Util.number import *
from gmpy2 import next_prime
p = getPrime(512)
q = getPrime(512)
n = p * q * next_prime(p) * next_prime(q)
e = 0x10001
flag = b"flag{xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx}"
cipher = pow(bytes_to_long(flag), e, n)
print(n, cipher)
n = 8030860507195481656424331455231443135773524476536419534745106637165762909478292141556846892146553555609301914884176422322286739546193682236355823149096731058044933046552926707682168435727800175783373045726692093694148718521610590523718813096895883533245331244650675812406540694948121258394822022998773233400623162137949381772195351339548977422564546054188918542382088471666795842185019002025083543162991739309935972705871943787733784491735500905013651061284020447578230135075211268405413254368439549259917312445348808412659422810647972872286215701325216318641985498202349281374905892279894612835009186944143298761257
c = 3304124639719334349997663632110579306673932777705840648575774671427424134287680988314129312593361087606243819528298610131797078262351307396831985397555390640151391138633431951746748156610463582479645561779194981806129898009876517899450840875569675976765155608446799203699927448835004756707151281044859676695533373755798273892503194753948997947653100690841880925445059175494314198605475023939567750409907217654291430615102258523998394231436796902635077995829477347316754739938980814293304289318417443493019704073164585505217658570214989150175123757038125380996050761572021986573934155470641091678664451080065719261207
n是由四個大素數相乘，next_prime(p) * next_prime(q)依次和p和q很接近，嘗試工具分解，但是失敗（數太大），只能先進行數論分析，下面是費馬因子分解
根據費馬因子分解,則有
\[n = ab = c^2 - d^2 = (c+d)(c-d) \therefore c = \frac{a+b}{2},d = \frac{a-b}{2} \]
移項可得：d^2 = c^2-n，其中c為大於√n的最小正整數
\[c = \sqrt{n}+i (i∈Z) \]
假設能找到一個特定的i，使得 c^2-n能被開放，那么就能得到d和c，進而得到因子a，b
由題可知，這幾個素數不會相差很大，因此p1q1,p1q2,p2q1,p2q2都很接近，根據費馬因子分解，可求得因子p1q1,p1q2,p2q1,p2q2，gcd(p1q1,p1q2) = p1
完整代碼如下：
from Crypto.Util.number import *
from gmpy2 import *
n = 8030860507195481656424331455231443135773524476536419534745106637165762909478292141556846892146553555609301914884176422322286739546193682236355823149096731058044933046552926707682168435727800175783373045726692093694148718521610590523718813096895883533245331244650675812406540694948121258394822022998773233400623162137949381772195351339548977422564546054188918542382088471666795842185019002025083543162991739309935972705871943787733784491735500905013651061284020447578230135075211268405413254368439549259917312445348808412659422810647972872286215701325216318641985498202349281374905892279894612835009186944143298761257
c = 3304124639719334349997663632110579306673932777705840648575774671427424134287680988314129312593361087606243819528298610131797078262351307396831985397555390640151391138633431951746748156610463582479645561779194981806129898009876517899450840875569675976765155608446799203699927448835004756707151281044859676695533373755798273892503194753948997947653100690841880925445059175494314198605475023939567750409907217654291430615102258523998394231436796902635077995829477347316754739938980814293304289318417443493019704073164585505217658570214989150175123757038125380996050761572021986573934155470641091678664451080065719261207
e = 0x10001
def fermat_factorization(n):
factor_list = []
get_context().precision = 2048
sqrt_n = int(sqrt(n))
c = sqrt_n
while True:
c += 1
d_square = c**2 - n
if is_square(d_square):
d_square = mpz(d_square)
get_context().precision = 2048
d = int(sqrt(d_square))
factor_list.append([c+d,c-d])
if len(factor_list)==2:
break
return factor_list
factor_list = fermat_factorization(n)
[X1,Y1] = factor_list[0]
[X2,Y2] = factor_list[1]
assert X1*Y1 == n
assert X2*Y2 == n
p1 = gcd(X1,X2)
q1 = X1 // p1
p2 = gcd(Y1,Y2)
q2 = Y1 // p2
Fai = (p1-1)*(q1-1)*(p2-1)*(q2-1)
d = invert(e,Fai)
print long_to_bytes(pow(c,d,n))
Exposure
題目給了一個python文件和一個數據文件，我把數據移到python文件那里
from Crypto.Util.number import *
import gmpy2
p = getStrongPrime(512)
q = getStrongPrime(512)
n = p * q
phi = (p - 1) * (q - 1)
e = 7621
d = gmpy2.invert(e, phi)
flag = b"flag{xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx}"
c = pow(bytes_to_long(flag), e, n) 加密
dp = d % (p - 1) p = 1 mod (p-1)
print(dp >> 200)
print(c, e, n)
dp = 1153696846823715458342658568392537778171840014923745253759529432977932183322553944430236879985
c= 46735962204857190520476434898881001530665718155698898882603422023484998388668858692912250418134186095459060506275961050676051693220280588047233628259880712415593039977585805890920089318643002597837000049626154900908543384761210358835843974072960080857150727010985827690190496793207012355214605393036388807616
e = 7621
n = 140376049134934822153964243403031201922239588054133319056483413311963385321279682186354948441840374124640187894619689719746347334298621083485494086361152915457458004998419817456902929318697902819798254427945343361548635794308362823239150919240307072688623000747781103375481834571274423004856276841225675241863
剛開始以為dp泄露攻擊，但是注意到dp泄露並不完整，dp右移了200位，只知道dp的高位，恢復dp的話，只需要爆破e次，就能得到p
對於恢復dp的解法，超出我的知識范疇，詳細見以下鏈接：
https://github.com/pcw109550/write-up/tree/master/2019/KAPO/Lenstra-Lenstra-Lovasz
完整代碼如下：
secret = 1153696846823715458342658568392537778171840014923745253759529432977932183322553944430236879985
c = 46735962204857190520476434898881001530665718155698898882603422023484998388668858692912250418134186095459060506275961050676051693220280588047233628259880712415593039977585805890920089318643002597837000049626154900908543384761210358835843974072960080857150727010985827690190496793207012355214605393036388807616
e = 7621
n = 140376049134934822153964243403031201922239588054133319056483413311963385321279682186354948441840374124640187894619689719746347334298621083485494086361152915457458004998419817456902929318697902819798254427945343361548635794308362823239150919240307072688623000747781103375481834571274423004856276841225675241863
[n, secret, c] = list(map(Integer, [n, secret, c]))
def facorize(e, dp):
for i in range(2, e):
p = (e * dp - 1 + i) // i
if n % p == 0:
return p
return -1
def recover(secret):
F.<x> = PolynomialRing(Zmod(n))
d = inverse_mod(e, n)
for k in range(1235, e):
print('k =',k)
f = (secret << 200) + x + (k - 1) * d
x0 = f.small_roots(X=2 ** (200 + 1), beta=0.44, epsilon=1/32)
if len(x0) != 0:
dp = x0[0] + (secret << 200)
p = facorize(e, Integer(dp))
if p < 0:
continue
else:
return p, dp
if __name__ == "__main__":
p, dp = recover(secret)
q = n // p
assert p * q == n
Fai = (p - 1) * (q - 1)
d = inverse_mod(e, Fai)
flag = bytes.fromhex(hex(pow(c, d, n))[2:])
print(flag)
blowfishgame
題目給了一個python文件（我只給出主要代碼）
bk = 8
master_key = os.urandom(bk)
sendIV = os.urandom(bk)
class Blow_CBC_demo:
def __init__(self, iv):
self.key = master_key
self.iv = iv
def pad(self, message):
pad_length = bk-len(message)%bk
return message+chr(pad_length)*pad_length
def unpad(self, message):
return message[:-ord(message[-1])]
def encrypt(self, message):
message = self.pad(message)
blow = Blowfish.new(self.key, Blowfish.MODE_CBC, self.iv)
ciphertxt = blow.encrypt(message)
return ciphertxt
def decrypt(self, message):
blow = Blowfish.new(self.key, Blowfish.MODE_CBC, self.iv)
plaintxt = blow.decrypt(message)
plaintxt = self.unpad(plaintxt)
return plaintxt
def send_enc(message):
sys.stdout.flush()
handle = Blow_CBC_demo(sendIV)
ciphertxt = handle.encrypt(message)
message = sendIV+ciphertxt
message = b64encode(message)
print(message)
return
def get_enc():
sys.stdout.flush()
message = sys.stdin.readline().strip()
try:
message = b64decode(message)
if (len(message) > 600):
exit(0)
handle = Blow_CBC_demo(message[:bk])
plaintxt = handle.decrypt(message[bk:])
return plaintxt
except:
print('Error')
exit(0)
def send_pl(m):
sys.stdout.flush()
print(m)
sys.stdout.flush()
def get_pl():
sys.stdout.flush()
return sys.stdin.readline().strip()
def pad(message):
pad_length = bk-len(message)%bk
return message+chr(pad_length)*pad_length
if __name__ == '__main__':
assert(len(flag) == 42)
if (not proof_of_work()):
send_pl("Bye!")
exit()
signal.alarm(180)
send_pl(banner)
send_enc('Blowfish_w0rld')
while True:
try:
message = get_enc().strip()
if message.startswith('get_flag'):
user = get_pl().strip()
blow = Blowfish.new(master_key)
send_pl(b64encode(blow.encrypt(pad(user+flag))))
elif message.startswith('exit'):
exit()
else:
send_enc('Invalid command')
except:
exit()
暫無思路，對CBC的攻擊方式未了解，待了解，也希望大佬不吝賜教
easy matrix
題目提示，提到矩陣和高斯消元法，可能和這個有關系，待研究
Web
由於本人非web選手，所以web的wp就不寫了（其實就是自己不會），可以參考其他師傅的wp
Pwn
待更新~