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BSides San Francisco CTF Writeup

この大会は2017/2/12 9:00(JST)~2017/2/14 9:00(JST)に開催されました。
今回もチームで参戦。結果は3527点で727チーム中23位でした。
自分で解けた問題をWriteupとして書いておきます。

[]root (Crypto 250)

pcapファイルが与えられている。No.11のパケットから証明書をエクスポートし、証明書(公開鍵)の内容を見てみる。

$ openssl x509 -in 11.cer -text -pubkey -inform DER
Certificate:
    Data:
        Version: 3 (0x2)
        Serial Number: 11416077129378495227 (0x9e6e0daa0910fafb)
    Signature Algorithm: sha256WithRSAEncryption
        Issuer: C=US, ST=New York, L=New York, O=E Corp, CN=pki.e-corp.com/emailAddress=pki@e-corp.com
        Validity
            Not Before: Feb  1 00:39:00 2017 GMT
            Not After : Feb  1 00:39:00 2018 GMT
        Subject: C=US, ST=New York, L=New York, O=E Corp, CN=pki.e-corp.com/emailAddress=pki@e-corp.com
        Subject Public Key Info:
            Public Key Algorithm: rsaEncryption
                Public-Key: (4103 bit)
                Modulus:
                    72:6f:6f:74:00:00:00:00:00:00:00:00:00:00:00:
                    00:00:00:00:00:00:1b:00:00:00:00:00:00:00:00:
                    00:00:00:00:00:1f:ff:fb:00:00:00:00:00:00:00:
                    00:00:00:00:00:1f:ff:fb:00:00:00:00:00:00:00:
                    00:00:00:00:00:1f:ff:ff:77:77:77:7b:00:00:00:
                    00:00:00:00:00:1f:ff:ff:ff:ff:ff:fb:00:00:00:
                    00:00:00:00:00:1f:ff:ff:ff:ff:fb:00:00:00:00:
                    00:00:00:00:00:1f:ff:ff:ff:ff:fb:00:00:00:00:
                    00:00:00:00:00:1f:ff:ff:ff:ff:ff:fb:00:00:00:
                    00:00:00:00:00:1f:ff:ff:22:22:22:2b:00:00:00:
                    00:00:00:00:00:1f:ff:fb:00:00:00:00:00:00:00:
                    00:00:00:00:00:1f:ff:fb:00:00:00:00:00:00:00:
                    00:00:00:00:00:1f:ff:fb:00:00:00:00:00:00:00:
                    00:00:00:00:00:1f:ff:fb:00:00:00:00:00:00:00:
                    00:00:00:00:00:1f:ff:fb:00:00:00:00:00:00:00:
                    00:00:00:00:00:1f:ff:fb:00:00:00:00:00:00:00:
                    00:00:00:00:00:1f:ff:fb:00:00:00:00:00:00:00:
                    26:52:93:c4:42:2b:e3:53:26:38:fe:eb:2a:63:5e:
                    86:5e:5b:cc:d4:86:2d:14:91:f8:e4:6e:d4:1a:fd:
                    ab:32:ab:1e:91:3c:29:6c:45:a7:23:a3:71:cc:4a:
                    d2:18:d2:73:a4:94:ac:50:1a:1c:67:75:76:b8:4d:
                    3a:17:00:b2:4e:38:f3:d7:c8:09:0c:95:27:67:f8:
                    a9:da:53:2e:b4:49:6a:95:3f:a2:b2:64:1f:93:af:
                    58:32:1e:49:1a:d6:b3:e1:f6:60:0e:a1:75:76:35:
                    a2:d4:75:62:df:f2:f2:45:bf:c8:ed:51:14:20:93:
                    1d:e2:46:d5:63:34:d8:89:7d:64:65:b2:27:f6:c0:
                    95:ec:e1:ad:99:4c:75:51:f0:8d:bc:21:f8:b4:06:
                    91:ee:51:f5:f7:2d:05:2d:93:52:06:2f:90:b0:e7:
                    c5:2c:2e:b1:81:96:c2:c9:85:10:1a:f4:ea:c6:74:
                    99:39:6c:62:41:ad:4f:24:39:ed:11:f8:7d:67:e7:
                    3a:23:9b:86:5c:45:d6:5a:61:cf:0f:56:08:2d:e8:
                    31:b9:7f:b2:8a:e8:22:2a:71:95:e0:ec:06:c0:82:
                    81:ff:c1:6e:71:06:e7:7e:68:b8:c4:51:04:24:be:
                    eb:55:82:fe:21:cc:34:5f:53:53:46:82:b7:5c:36:
                    8d:73:c9
                Exponent: 31337 (0x7a69)
        X509v3 extensions:
            X509v3 Subject Key Identifier: 
                4D:EC:FC:58:C3:9F:6B:A7:C9:0F:FC:0B:25:FD:46:F2:7C:AB:F8:44
            X509v3 Authority Key Identifier: 
                keyid:4D:EC:FC:58:C3:9F:6B:A7:C9:0F:FC:0B:25:FD:46:F2:7C:AB:F8:44

            X509v3 Basic Constraints: 
                CA:TRUE
    Signature Algorithm: sha256WithRSAEncryption
         0d:f1:f7:4f:e1:a7:7d:0c:92:d7:29:69:09:0e:5a:49:2b:25:
         b5:95:1c:32:f6:6e:04:52:5e:fc:82:d1:9e:6a:6a:60:23:42:
         62:8a:37:24:7b:ac:f1:e6:d9:8b:d9:b7:53:a8:d5:c6:a9:9a:
         e8:7d:28:a2:41:74:1e:c5:1f:08:8c:de:7a:f1:28:f1:a9:ba:
         bf:fb:11:29:2a:3d:4f:d1:5b:a2:5f:86:ba:e8:09:30:d3:c4:
         40:67:b2:57:bd:80:b2:c9:bf:98:d2:9e:ab:2c:07:65:9f:5e:
         3f:44:8c:5f:d9:b7:a0:aa:85:5c:9d:f1:46:90:0c:7f:41:35:
         24:73:99:49:03:5f:a3:a8:45:26:c0:51:ce:0b:a5:e0:30:2a:
         59:4e:98:77:fb:4a:83:3c:af:09:e8:61:47:a5:80:1f:b0:8c:
         f0:7e:9a:b5:75:54:bd:b0:8f:05:9e:04:75:d8:c0:e6:4b:b5:
         6b:ba:20:0c:14:fb:4c:87:c3:e9:8f:47:ba:1e:23:70:9d:5b:
         bd:11:63:a3:45:e2:91:54:02:b2:af:f6:ff:cb:c7:bd:0e:b1:
         87:bf:19:11:59:93:77:1c:a0:f5:b7:1a:c1:24:d6:1d:b2:70:
         0b:96:ac:34:45:80:8d:27:53:45:15:d9:75:89:02:45:60:aa:
         ee:0e:8f:0a:a0:36:e8:2a:00:18:09:d9:0a:2d:78:bb:06:f4:
         14:b4:04:2c:f6:c0:b6:5c:a3:f8:28:1b:91:b5:2b:9e:e4:af:
         35:cf:fb:b8:7b:ed:9f:73:7b:b6:14:a8:5e:21:5f:a0:66:76:
         3d:25:65:07:ff:02:ed:24:1f:07:d9:6a:79:db:c1:7f:ce:83:
         2c:bd:2f:1c:3a:22:41:a3:f3:30:27:b4:01:59:49:32:90:32:
         96:f0:a2:8b:b7:36:61:64:cf:7e:c1:97:bd:7b:25:e8:74:65:
         f4:d4:71:21:24:ba:10:95:c0:f7:9c:4d:c9:e8:82:1e:71:4d:
         d6:3b:9b:5c:f2:72:01:41:cc:34:f7:42:e2:e8:f5:a2:9c:21:
         61:08:5c:d4:b5:bf:fe:f4:ce:9f:b8:0e:fc:a8:9d:9f:8e:0f:
         a3:f6:41:98:73:77:cc:0b:d9:7b:5a:1f:54:fd:1f:75:bd:ba:
         d0:a1:de:ac:6f:43:a9:64:31:07:91:de:b4:0e:53:da:0d:08:
         07:dc:0a:f1:8a:03:30:6b:75:f5:96:43:b3:75:30:79:a9:8e:
         fd:06:5e:d1:c4:54:09:c7:f3:2f:69:a9:5a:8d:33:02:09:9d:
         4e:a3:63:33:66:ca:9a:82:f8:5f:5b:dc:3f:45:16:35:de:68:
         d2:17:bf:0b:15:b9:d9:ae:8b
-----BEGIN PUBLIC KEY-----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-----END PUBLIC KEY-----
-----BEGIN CERTIFICATE-----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=
-----END CERTIFICATE-----

nをFermat法で素因数分解してみる。

def isqrt(n):
    x = n
    y = (x + n // x) // 2
    while y < x:
        x = y
        y = (x + n // x) // 2
    return x

def fermat(n):
    x = isqrt(n) + 1
    y = isqrt(x * x - n)

    while True:
        w = x * x - n - y * y
        if w == 0:
            break
        elif w > 0:
            y += 1
        else:
            x += 1
    return x - y, x + y

n = 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
p, q = fermat(n)
print 'p =', p
print 'q =', q

実行結果は以下の通り。

p = 345709341936068338730678003778405323582109317075021198605451259081268526297654818935837545259489748700537817158904946124698593212156185601832821337576558516676594811692389205842412600462658083813048872307642872332289082295535733483056820073388473845450507806559178316793666044371642249466611007764799781626418800031166072773475575269610775901034485376573476373962417949231752698909821646794161147858557311852386822684705642251949742285300552861190676326816587042282505137369676427345123087656274137257931639760324708350318503061363031086796994100943084772281097123781070811610760735943618425858558459014484742232018933
q = 345709341936068338730678003778405323582109317075021198605451259081268526297654818935837545259489748700537817158904946124698593212156185601832821337576558516676594811692389205842412600462658083813048872307642872332289082295535733483056820073388473845450507806559178316793666044371642249466611007764799781626418800031166072773475575269610775901034485376573476373962417949231752698909821646794161147858557311852386822684705642251949742285300552861190676326816587042282505137369676427345123087656274137257931639760324708350318503061363031086796994100943084772281097123781070811610760735943618425858558459014484742232019973

pとqがわかったので、秘密鍵を作成する。

$ rsatool.py -f PEM -o secret.pem -p 345709341936068338730678003778405323582109317075021198605451259081268526297654818935837545259489748700537817158904946124698593212156185601832821337576558516676594811692389205842412600462658083813048872307642872332289082295535733483056820073388473845450507806559178316793666044371642249466611007764799781626418800031166072773475575269610775901034485376573476373962417949231752698909821646794161147858557311852386822684705642251949742285300552861190676326816587042282505137369676427345123087656274137257931639760324708350318503061363031086796994100943084772281097123781070811610760735943618425858558459014484742232018933 -q 345709341936068338730678003778405323582109317075021198605451259081268526297654818935837545259489748700537817158904946124698593212156185601832821337576558516676594811692389205842412600462658083813048872307642872332289082295535733483056820073388473845450507806559178316793666044371642249466611007764799781626418800031166072773475575269610775901034485376573476373962417949231752698909821646794161147858557311852386822684705642251949742285300552861190676326816587042282505137369676427345123087656274137257931639760324708350318503061363031086796994100943084772281097123781070811610760735943618425858558459014484742232019973 -e 31337
Using (p, q) to initialise RSA instance

n =
726f6f7400000000000000000000000000000000001b000000000000000000000000001ffffb0000
000000000000000000001ffffb0000000000000000000000001fffff7777777b0000000000000000
1ffffffffffffb00000000000000001ffffffffffb0000000000000000001ffffffffffb00000000
00000000001ffffffffffffb00000000000000001fffff2222222b00000000000000001ffffb0000
000000000000000000001ffffb0000000000000000000000001ffffb000000000000000000000000
1ffffb0000000000000000000000001ffffb0000000000000000000000001ffffb00000000000000
00000000001ffffb00000000000000265293c4422be3532638feeb2a635e865e5bccd4862d1491f8
e46ed41afdab32ab1e913c296c45a723a371cc4ad218d273a494ac501a1c677576b84d3a1700b24e
38f3d7c8090c952767f8a9da532eb4496a953fa2b2641f93af58321e491ad6b3e1f6600ea1757635
a2d47562dff2f245bfc8ed511420931de246d56334d8897d6465b227f6c095ece1ad994c7551f08d
bc21f8b40691ee51f5f72d052d9352062f90b0e7c52c2eb18196c2c985101af4eac67499396c6241
ad4f2439ed11f87d67e73a239b865c45d65a61cf0f56082de831b97fb28ae8222a7195e0ec06c082
81ffc16e7106e77e68b8c4510424beeb5582fe21cc345f53534682b75c368d73c9

e = 31337 (0x7a69)

d =
618caed447e3b3a23fe661970669b19fc8517f1affef47db561cb4eec562b589878940899882f490
236c017870796d86753252ae97d1d1b6869490ec30867fa71e7062aecf0057fcae6bfb324c5133d1
693cc566e44c48c1ee139f5fc079d203feebf1c911d1bcccb8b925e5adbc6a851c2072bebcea000c
8c4850736a69c0865e310824f9e7de36429cb3e32ff88bf7ef4ccb39e7585de9ed3a1feaea85d087
486ba35c521e0be928a478d51a5915f3672b673c2247383670ba5991427b3dcce8d2e5c4bd7e7c0f
0a3a96eff4a0de771767a8e20f46c97a8e5f9d7878d6f3116cce6bb8462014be21875d557137bd24
8eb3590d95fce7a17bdcbdd223465cc017d6fc76fbfe2e4b9ccc49241ba452fdf84d1c8185cad33a
83c5b5ac43d946df4c3648af4f7714cd584db1ecd14458c8827ac222c3ca08280c2ba687c19aa8df
77d498cfaf700c9019f505380a78ba43f2f1bcd82a15e19c4daa3b33051d31aec1a94e043f81b7fb
21af1975588fdaa0dbfb269f118e5c4e9e26922c1440ab85357aab110361662927b74f2fe27825ba
e9e9d7aa341d8341b93588eda2e780cd99ad790ac28146f113b3d09f470e64c07a0bd51d8b4b7470
c9a931414305a53fda0a168561a2b8906ce7ff4215c0912248d55ca3e0499af1f59877b78a07a377
e570f1b9fe70b9b5cd9461bf6bc39f8734ea07b4e3f6a71129179b4183d3e4f0a9

p =
ab28ba5dbd67a4b8b4c20b76958ad57ef5513ea01af2ad59b1691a4b60e7eee058aa4776bc96a3b7
b3b3ab98a743ff0e16c22033481dfd0c83654311e153b14d5067ea4664d419b97ba28a6ee5693b00
acb7c7046762b0d8ece2bdbdc4c784923178beb1c8c78fd123003f4c107f2aa772a7f22f3052ee69
561a265acf618513acd76321d2c3a6dcd6456152c4032d8fd285ee013746eb1439f4c9c66b9ffd90
3b63208bbb0bf82b52cfc6bd12df96f3d9fa12c96456fd94e7f5c1238b3d5089e6be64ac555f8468
3ede12cc1ffa1a66fbe5e4d2c830e14d6954c48747bc1cec60582a312ee97274a9f7211e3213ff20
81d9f69b07a7b0fa8f89edd037e730ff5

q =
ab28ba5dbd67a4b8b4c20b76958ad57ef5513ea01af2ad59b1691a4b60e7eee058aa4776bc96a3b7
b3b3ab98a743ff0e16c22033481dfd0c83654311e153b14d5067ea4664d419b97ba28a6ee5693b00
acb7c7046762b0d8ece2bdbdc4c784923178beb1c8c78fd123003f4c107f2aa772a7f22f3052ee69
561a265acf618513acd76321d2c3a6dcd6456152c4032d8fd285ee013746eb1439f4c9c66b9ffd90
3b63208bbb0bf82b52cfc6bd12df96f3d9fa12c96456fd94e7f5c1238b3d5089e6be64ac555f8468
3ede12cc1ffa1a66fbe5e4d2c830e14d6954c48747bc1cec60582a312ee97274a9f7211e3213ff20
81d9f69b07a7b0fa8f89edd037e731405

Saving PEM as secret.pem

Wiresharkで以下の設定によりSSLの復号をし、SSL Streamを見る。

  • IP address: 4.3.2.1
  • Port: 443
  • Protocol: http
  • Key File: secret.pem
GET /modulus.txt HTTP/1.0
Host: 4.3.2.1
User-Agent: E Corp PKI Modulus Fetch
Accept: */*

HTTP/1.0 200 ok
Content-type: text/plain

72:6f:6f:74:00:00:00:00:00:00:00:00:00:00:00:
00:00:00:00:00:00:1b:00:00:00:00:00:00:00:00:
00:00:00:00:00:1f:ff:fb:00:00:00:00:00:00:00:
00:00:00:00:00:1f:ff:fb:00:00:00:00:00:00:00:
00:00:00:00:00:1f:ff:ff:77:77:77:7b:00:00:00:
00:00:00:00:00:1f:ff:ff:ff:ff:ff:fb:00:00:00:
00:00:00:00:00:1f:ff:ff:ff:ff:fb:00:00:00:00:
00:00:00:00:00:1f:ff:ff:ff:ff:fb:00:00:00:00:
00:00:00:00:00:1f:ff:ff:ff:ff:ff:fb:00:00:00:
00:00:00:00:00:1f:ff:ff:22:22:22:2b:00:00:00:
00:00:00:00:00:1f:ff:fb:00:00:00:00:00:00:00:
00:00:00:00:00:1f:ff:fb:00:00:00:00:00:00:00:
00:00:00:00:00:1f:ff:fb:00:00:00:00:00:00:00:
00:00:00:00:00:1f:ff:fb:00:00:00:00:00:00:00:
00:00:00:00:00:1f:ff:fb:00:00:00:00:00:00:00:
00:00:00:00:00:1f:ff:fb:00:00:00:00:00:00:00:
00:00:00:00:00:1f:ff:fb:00:00:00:00:00:00:00:
00:00:00:00:1f:ff:00:ff:fb:00:00:00:00:00:00:
00:00:00:00:1f:00:00:00:fb:00:00:00:00:00:00:
00:00:00:1f:00:00:00:00:00:fb:00:00:00:00:00:
00:00:00:1f:00:00:00:00:00:fb:00:00:00:00:00:
00:00:1f:00:00:00:00:00:00:00:fb:00:00:00:00:
00:00:1f:00:00:00:00:00:00:00:fb:00:00:00:00:
00:00:00:1f:00:00:00:00:00:fb:00:00:00:00:00:
00:00:00:1f:00:00:00:00:00:fb:00:00:00:00:00:
00:00:00:00:1f:00:00:00:fb:00:00:00:00:00:00:
00:00:00:00:1f:ff:00:ff:fb:00:00:00:00:00:00:
00:00:00:00:00:00:1b:00:00:00:00:00:00:00:00:
00:00:00:00:00:00:00:00:00:00:00:00:66:6c:61:
67:3a:77:68:65:6e:5f:73:6f:6c:76:69:6e:67:5f:
70:72:6f:62:6c:65:6d:73:5f:64:69:67:5f:61:74:
5f:74:68:65:5f:72:6f:6f:74:73:5f:69:6e:73:74:
65:61:64:5f:6f:66:5f:6a:75:73:74:5f:68:61:63:
6b:69:6e:67:5f:61:74:5f:74:68:65:5f:6c:65:61:
76:65:73

最後の66:6c:61:からフラグのASCIIコードのようなので、デコードする。

enc = '66:6c:61:67:3a:77:68:65:6e:5f:73:6f:6c:76:69:6e:67:5f:70:72:6f:62:6c:65:6d:73:5f:64:69:67:5f:61:74:5f:74:68:65:5f:72:6f:6f:74:73:5f:69:6e:73:74:65:61:64:5f:6f:66:5f:6a:75:73:74:5f:68:61:63:6b:69:6e:67:5f:61:74:5f:74:68:65:5f:6c:65:61:76:65:73'

dec = enc.replace(':', '').decode('hex')
print dec

実行結果は以下の通り。

flag:when_solving_problems_dig_at_the_roots_instead_of_just_hacking_at_the_leaves
when_solving_problems_dig_at_the_roots_instead_of_just_hacking_at_the_leaves