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DEFCON2K12 Prequals: for400 writeup

Written by Nicolas Hureau
2012-06-04 03:24:00

In this forensic challenge, we have access to a Windows RAM dump. The clue is "HBgary say waht?!" so we know it is an email related problem. Let's fire up an hex editor and volatility. Let's look at the processes that were running at the time of the dump:

kalenz@chev ~/lse/ctf/defcon/f400 12-06-04 3:10:11
> vol.py -f memory.dmp --profile=Win7SP1x86 pstree
Volatile Systems Volatility Framework 2.0
Name                                Pid    PPid   Thds   Hnds   Time
 0x8541F130:wininit.exe                396    328      3     75 2012-05-28 02:31:20
. 0x8545EB00:lsm.exe                   512    396     10    143 2012-05-28 02:31:21
. 0x85457030:services.exe              492    396      9    207 2012-05-28 02:31:21
.. 0x854BE660:svchost.exe              780    492     19    440 2012-05-28 02:31:23
.. 0x855C5030:dirmngr.exe             1424    492      5     83 2012-05-28 02:31:26
.. 0x8567D108:TPAutoConnSvc.          1812    492      9    133 2012-05-28 02:31:28
... 0x85793A38:TPAutoConnect.         2408   1812      5    145 2012-05-28 02:33:54
.. 0x85619D40:vmtoolsd.exe            1568    492      8    255 2012-05-28 02:31:27
.. 0x8558BA30:svchost.exe             1328    492     18    305 2012-05-28 02:31:26
.. 0x8573B8C0:svchost.exe             1872    492     13    327 2012-05-28 02:33:28
.. 0x85674840:svchost.exe             1220    492      5     69 2012-05-28 02:33:28
.. 0x856795D8:msdtc.exe                296    492     12    143 2012-05-28 02:31:31
.. 0x854A33F0:svchost.exe              684    492      7    258 2012-05-28 02:31:23
.. 0x84690538:taskhost.exe            2060    492      7    150 2012-05-28 02:33:52
.. 0x854D6BD0:svchost.exe              820    492     17    410 2012-05-28 02:31:23
... 0x85501A00:dwm.exe                2116    820      7    143 2012-05-28 02:33:52
.. 0x855F6A58:svchost.exe             1476    492      6    107 2012-05-28 02:31:26
.. 0x854DA030:svchost.exe              844    492     26    851 2012-05-28 02:31:23
.. 0x84863030:svchost.exe             2872    492      4     40 2012-05-28 02:55:09
.. 0x8550B8F0:svchost.exe              996    492     10    502 2012-05-28 02:31:23
.. 0x856A6030:dllhost.exe             1996    492     13    184 2012-05-28 02:31:29
.. 0x85578518:spoolsv.exe             1296    492     14    331 2012-05-28 02:31:25
.. 0x8552B030:svchost.exe             1124    492     14    349 2012-05-28 02:31:24
.. 0x85491C48:svchost.exe              616    492     11    352 2012-05-28 02:31:22
.. 0x84433560:SearchIndexer.          1508    492     13    612 2012-05-28 02:33:29
. 0x8545BC00:lsass.exe                 500    396      6    535 2012-05-28 02:31:21
 0x852067B8:csrss.exe                  336    328      9    378 2012-05-28 02:31:19
 0x85744D40:explorer.exe              2176   2108     21    831 2012-05-28 02:33:52
. 0x85431D40:mspaint.exe              2696   2176      5    115 2012-05-28 02:34:23
. 0x85787030:VMwareTray.exe           2284   2176      5     67 2012-05-28 02:33:54
. 0x8485EAB8:chrome.exe               3440   2176     24    716 2012-05-28 02:36:00
.. 0x84881D40:chrome.exe              3624   3440      4    130 2012-05-28 02:36:07
.. 0x8495D508:chrome.exe              4004   3440      6    124 2012-05-28 02:36:41
.. 0x8494DD40:rundll32.exe            3916   3440      2     84 2012-05-28 02:36:37
.. 0x84945030:chrome.exe              3884   3440      6    126 2012-05-28 02:36:37
.. 0x848DF550:chrome.exe              3736   3440      6    126 2012-05-28 02:36:19
.. 0x8494ED40:chrome.exe              3924   3440      6    209 2012-05-28 02:36:37
. 0x85431780:calc.exe                 2712   2176      4     77 2012-05-28 02:34:24
. 0x85716D40:thunderbird.ex           2372   2176     36    432 2012-05-28 02:47:24
.. 0x84A25030:gpg.exe                 2464   2372      0 ------ 2012-05-28 02:54:56
.. 0x849BC030:gpg.exe                 2404   2372      0 ------ 2012-05-28 02:56:03
.. 0x848A8D40:gpg.exe                 2360   2372      0 ------ 2012-05-28 02:54:56
.. 0x84A16168:gpg-connect-ag          3616   2372      0 ------ 2012-05-28 02:50:29
.. 0x849E2540:gpg.exe                 2804   2372      0 ------ 2012-05-28 02:50:29
. 0x85789BD8:GoogleUpdate.e           2304   2176      5    109 2012-05-28 02:33:54
. 0x85787400:vmtoolsd.exe             2292   2176      6    214 2012-05-28 02:33:54
 0x84A25D40:gpg-agent.exe             4036   3128      1     72 2012-05-28 02:50:30
. 0x8491E738:pinentry.exe             3252   4036      0 ------ 2012-05-28 02:55:15
. 0x849EA8C0:pinentry.exe             1168   4036      0 ------ 2012-05-28 02:56:10
. 0x848E1030:pinentry.exe              668   4036      0 ------ 2012-05-28 02:56:22
. 0x84A22A38:pinentry.exe             3692   4036      0 ------ 2012-05-28 02:56:27
. 0x848636B8:pinentry.exe             3816   4036      0 ------ 2012-05-28 02:56:18
. 0x84A27AF0:pinentry.exe             1856   4036      0 ------ 2012-05-28 02:55:43
. 0x849FB620:pinentry.exe             3868   4036      0 ------ 2012-05-28 02:56:30
. 0x84997778:pinentry.exe             2576   4036      0 ------ 2012-05-28 02:56:23
. 0x85709D40:pinentry.exe             2904   4036      0 ------ 2012-05-28 02:55:13
. 0x84965C90:pinentry.exe             3284   4036      0 ------ 2012-05-28 02:55:03
 0x84415AE8:csrss.exe                  388    380     11    369 2012-05-28 02:31:20
. 0x85792D40:conhost.exe              2416    388      1     33 2012-05-28 02:33:54
 0x85420170:winlogon.exe               432    380      3    110 2012-05-28 02:31:20
 0x84138C40:System                       4      0     86    496 2012-05-28 02:31:14
. 0x846EA308:smss.exe                  244      4      2     29 2012-05-28 02:31:14

We can see two interesting things: a Thunderbird process and a GnuPG process. Let's try to find PGP armored data by looking for "BEGIN PGP" in the memory. We find a few encrypted messages and a public key:

text:::
-----BEGIN PGP PUBLIC KEY BLOCK-----
Version: GnuPG v2.0.17 (MingW32)
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=3D811y
-----END PGP PUBLIC KEY BLOCK-----

We now have to find the private key to be able to decipher the messages. Of course the private key is not present in its armored form in the memory, so we have to look for its binary counterpart. We know that the private key contains all the data of the public key (RFC 4880), therefore we just have to look for a few bytes of the public key in the memory. Let's look at what the public key looks like:

text:::
kalenz@chev /sgoinfre/defcon/forensics/400 12-06-04 03:14:44
> pgpdump -i public-key
Old: Public Key Packet(tag 6)(141 bytes)
    Ver 4 - new
    Public key creation time - Sat May 26 21:21:53 CEST 2012
    Pub alg - RSA Encrypt or Sign(pub 1)
    RSA n(1024 bits) - d5 df 3d 1e 6a 72 99 be df ba b2 f5 d2 ab 44 4c 74 bd 8b 73 cc 14 11 ef 5e fc 4a 18 3d 47 01 27 24 6a 6c 84 5a 2a 8b 6f f1 9a d0 9f 6b 52 ee 01 74 ee 23 cf 72 13 52 2f e1 8a e6 43 70 c7 c3 4a 0b 05 55 22 e4 5a 90 51 5a ea 63 c5 1a 00 4a 6d 25 1f a2 f4 78 7e 20 38 4c 39 c3 f4 49 f9 03 4b d7 cc 1d 0e 47 0a 0a b0 a6 48 0f d0 cb 98 d5 7b 8d cb 1e 36 06 d1 a5 04 80 e1 c6 c3 e9 0a be a9 
    RSA e(17 bits) - 01 00 01 
Old: User ID Packet(tag 13)(58 bytes)
    User ID - Poseidon (defcon ctf quals key) <poseidon.ddtek@gmail.com>
Old: Signature Packet(tag 2)(190 bytes)
    Ver 4 - new
    Sig type - Positive certification of a User ID and Public Key packet(0x13).
    Pub alg - RSA Encrypt or Sign(pub 1)
    Hash alg - SHA1(hash 2)
    Hashed Sub: signature creation time(sub 2)(4 bytes)
        Time - Sat May 26 21:21:53 CEST 2012
    Hashed Sub: key flags(sub 27)(1 bytes)
        Flag - This key may be used to certify other keys
        Flag - This key may be used to sign data
        Flag - This key may be used for authentication
    Hashed Sub: key expiration time(sub 9)(4 bytes)
        Time - Mon Jun 25 21:21:53 CEST 2012
    Hashed Sub: preferred symmetric algorithms(sub 11)(5 bytes)
        Sym alg - AES with 256-bit key(sym 9)
        Sym alg - AES with 192-bit key(sym 8)
        Sym alg - AES with 128-bit key(sym 7)
        Sym alg - CAST5(sym 3)
        Sym alg - Triple-DES(sym 2)
    Hashed Sub: preferred hash algorithms(sub 21)(5 bytes)
        Hash alg - SHA256(hash 8)
        Hash alg - SHA1(hash 2)
        Hash alg - SHA384(hash 9)
        Hash alg - SHA512(hash 10)
        Hash alg - SHA224(hash 11)
    Hashed Sub: preferred compression algorithms(sub 22)(3 bytes)
        Comp alg - ZLIB <RFC1950>(comp 2)
        Comp alg - BZip2(comp 3)
        Comp alg - ZIP <RFC1951>(comp 1)
    Hashed Sub: features(sub 30)(1 bytes)
        Flag - Modification detection (packets 18 and 19)
    Hashed Sub: key server preferences(sub 23)(1 bytes)
        Flag - No-modify
    Sub: issuer key ID(sub 16)(8 bytes)
        Key ID - 0x64FDCDE0FB9C695E
    Hash left 2 bytes - 7f 65 
    RSA m^d mod n(1023 bits) - 56 94 a2 5d 58 b0 ff 1e 9d 5b 0c 3e e3 f3 cf f2 8a e7 e7 8c f4 e0 1d be 39 50 a3 ec 13 b3 c4 85 10 1d 89 7e 85 99 a6 46 cd e5 03 f9 dd ba 0a 73 e0 c6 78 14 f8 ad 61 91 6a c3 4a d9 55 9f 9d 8b 95 31 3b 4c 6a b5 44 4f 1a 27 b2 22 4c 0e 59 5d c7 86 c0 8a d8 50 90 31 32 d6 65 6c db c6 05 c5 56 83 c9 26 37 a6 88 f2 dc 02 76 3b c4 24 b2 76 2e 97 23 60 e3 13 82 17 d7 36 c5 fe b2 e8 f3 d7 
        -> PKCS-1
Old: Public Subkey Packet(tag 14)(141 bytes)
    Ver 4 - new
    Public key creation time - Sat May 26 21:21:53 CEST 2012
    Pub alg - RSA Encrypt or Sign(pub 1)
    RSA n(1024 bits) - c5 d3 fc 58 d3 16 fa 25 c8 c5 ff 66 e5 e9 13 57 72 6d 2b 51 bc 32 f6 7b c6 f3 4f 8c d9 78 9f 55 7d 1a 05 f2 0a bf 4c 47 46 8b 89 b2 98 73 15 e9 cd 14 37 18 5e ec d8 28 f7 23 1a 17 55 3e a4 b1 c1 c2 87 49 9a 96 75 b1 14 84 cf b2 25 46 5f ee ef d9 83 88 89 aa 88 0c b7 b0 3a 18 78 e7 a4 e0 e9 00 89 98 66 ff 89 c6 b3 4f 4a 07 20 23 69 a5 33 2c f8 d5 ea 1f 6b be 00 68 8e 28 53 08 ba 85 
    RSA e(17 bits) - 01 00 01 
Old: Signature Packet(tag 2)(165 bytes)
    Ver 4 - new
    Sig type - Subkey Binding Signature(0x18).
    Pub alg - RSA Encrypt or Sign(pub 1)
    Hash alg - SHA1(hash 2)
    Hashed Sub: signature creation time(sub 2)(4 bytes)
        Time - Sat May 26 21:21:53 CEST 2012
    Hashed Sub: key flags(sub 27)(1 bytes)
        Flag - This key may be used to encrypt communications
        Flag - This key may be used to encrypt storage
    Hashed Sub: key expiration time(sub 9)(4 bytes)
        Time - Mon Jun 25 21:21:53 CEST 2012
    Sub: issuer key ID(sub 16)(8 bytes)
        Key ID - 0x64FDCDE0FB9C695E
    Hash left 2 bytes - 1c 6e 
    RSA m^d mod n(1024 bits) - 9e 62 c8 31 80 a3 b8 a4 63 43 c4 9b 68 7e c5 dc d1 7c d5 b1 29 c6 e4 89 52 51 e9 6e a4 c6 bf c7 51 9f b9 5e a3 cf de 0e 7d 0f 04 dc 25 9d ea a2 17 42 69 aa 86 92 40 86 bd 36 ab b7 51 8d b3 a9 5d 19 9f 89 d5 24 a5 7d 78 55 97 c8 db bd ef 0d 89 dc 99 87 93 2b c6 57 b4 63 79 5c 9a f0 cc 33 f2 fc f2 42 dc 20 6d 26 32 bf a6 50 b8 3f 20 94 a3 7a b3 e3 55 6a e9 95 95 60 03 3e 9a 64 a2 c2 
        -> PKCS-1

Let's look for "d5 df 3d 1e 6a 72 99 be df ba b2 f5 d2 ab 44". It yields three results, two of which are the public key in binary form, and the last is longer and somewhat different but has a lot of the public key data in it. It must therefore be the private key:

We now just have to dump the private key (this is the armored version):

text:::
-----BEGIN PGP PRIVATE KEY BLOCK-----
Version: GnuPG v2.0.19 (GNU/Linux)
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=pDML
-----END PGP PRIVATE KEY BLOCK-----

And, then try to decrypt all the messages we found earlier. There were a bunch of funny messages and then we stumbled upon this one:

text:::
-----BEGIN PGP MESSAGE-----
Charset: ISO-8859-1
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=x441
-----END PGP MESSAGE-----

And that's it:

text:::
kalenz@chev /sgoinfre/defcon/forensics/400 12-06-04 03:17:21
> gpg -d foolol3
gpg: encrypted with RSA key, ID EC1B51DB
gpg: encrypted with 1024-bit RSA key, ID D7A51CC5, created 2012-05-26
      "Poseidon (defcon ctf quals key) <poseidon.ddtek@gmail.com>"
the key is: as it turns out, Phil Zimmermann also likes sheep.

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LSE Week 2012 videos

Written by Nicolas Hureau
2012-09-30 16:30:00

It has been about three months since the 2012 edition of the LSE week, and we are happy because it was quite a success, having on average 57 people attending each talk.

Now is time to publish slides (in english) and videos (in french).

CSAT (Pierre-Marie de Rodat - 30mn)

The premise of an interactive disassembler aiming at being collaborative.

slides

ARM architecture (Julien Frêche - 30mn)

Global overview and emulator writing.

slides

Datameat (Victor Apercé - 1h)

Metadata oriented filesystem.

slides

FrASM (Pierre-Marie de Rodat - 30mn)

An assembler writing framework.

slides

Video game console emulation (Pierre Bourdon & Nicolas Hureau - 1h30)

Implications and problems of emulating high performance hardware and cycle-accurate emulation. slides

Possible optimizations for an interpreter (Benoît Zanotti - 30mn)

What can be done? How will it impact performance? Prolog as an example. slides

Routing protocol: BGP4 (Sylvain Laurent - 18h00 - 30mn)

Introduction to BGP4 and its role in networks. slides

WTF is ACPI? (Ivan Delalande - 1h)

Global overview and implementation of an ACPI VM. slides

Forensics (Samuel Chevet - 1h)

Interest and tools. slides

Tutorial: Arduino development (Augustin Chéron - 1h)

Use cases, limitations and demonstration of the Arduino platform. slides

Tutorial: Exploitation techniques (Clément Rouault - 1h)

Examples and mitigation of software exploits. slides

Introduction to CTFs (Nicolas Hureau - 1h)

Interest of participating in security contests and walkthrough of a few exercises. slides

WPA2 enterprise and Wi-Fi security (Pierre Bourdon - 1h)

What is to be avoided when deploying Wi-Fi on a student campus. slides

C!: Interface Implementation (Marwan Burelle - 30mn)

slides

Evolution of rootkits (Samuel Chevet - 1h)

Inner working, analysis and development of the major rootkits. slides

Crackme LSE Week (Pierre Bourdon - 30mn)

Making-of and solution of the LSE Week crackme. slides

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NDH2K13 crackme300 writeup

Written by Nicolas Hureau
2013-03-09 00:00:00

Connect to the remote machine and break the code. Oh wait, maybe you'll
need some tools.

Score   300
Link    ssh://user:ndh2k13@z0b.nuitduhack.com:2222/

We are able to retrieve two files: - an ELF asking for a password - a vmlinux

Launching crackme on my box failed miserably. The code didn't make any sense and the e_flags field of the ELF header which was supposed to be 0 was equal to 0x20.

As we were provided with a vmlinux, I guessed the ELF loading routine of the kernel had been modified to check if e_flags was 0x20, and in this case apply some operation. When reversing load_elf_binary (fs/binfmt_elf.c), you see that the code is xored. It can be fixed with the following code:

#include <stdio.h>

#define OFFSET (0x610)
#define SIZE (0x418 + 0xe + 0x28)

int main(int argc, char** argv)
{
    char key[] =
        "\x12\x43\x34\x65\x78\xcf\xdc\xca\x98\x90"
        "\x65\x31\x21\x56\x83\xfa\xcd\x30\xfd\x12"
        "\x84\x98\xb7\x54\xa5\x62\x61\xf9\xe3\x09"
        "\xc8\x94\x12\xe6\x87";

    FILE* f = fopen(argv[1], "r+");
    char buf[SIZE];

    fseek(f, OFFSET, SEEK_SET);
    fread(buf, 1, SIZE, f);

    for (int i = 0; i < SIZE; ++i)
        buf[i] = buf[i] ^ key[i % 35];

    fseek(f, OFFSET, SEEK_SET);
    fwrite(buf, 1, SIZE, f);

    fclose(f);
    return 0;
}

Now that we have a working ELF, we can look at it and see that it a quite straightforward to reverse. There may only be four different characters: - w - a - s - d

Looking closer, we can see that there is to globals, which begin at 0, and that must both be equals to 15 to have the right password. We can also se that there is a 16x16 table filled with ones and zeroes, and the globals (which are in fact w and h position in the table) must point to a 0 (it's a maze, you must get from (0, 0) to (15, 15) without going through a wall).

The following python script find the correct sequence of keys, which is the key:

#! /usr/bin/env python3

import sys

TABLE = [
    0x00, 0x01, 0x00, 0x00, 0x01, 0x00, 0x00, 0x00, 0x01, 0x01, 0x01, 0x00, 0x01, 0x00, 0x01, 0x01,
    0x00, 0x01, 0x00, 0x01, 0x01, 0x00, 0x01, 0x00, 0x00, 0x00, 0x01, 0x00, 0x01, 0x00, 0x01, 0x01,
    0x00, 0x00, 0x00, 0x01, 0x00, 0x00, 0x01, 0x00, 0x01, 0x01, 0x00, 0x00, 0x00, 0x00, 0x01, 0x01,
    0x01, 0x01, 0x00, 0x01, 0x01, 0x00, 0x01, 0x01, 0x01, 0x01, 0x00, 0x01, 0x01, 0x00, 0x00, 0x00,
    0x01, 0x01, 0x00, 0x00, 0x00, 0x00, 0x01, 0x01, 0x01, 0x00, 0x00, 0x01, 0x01, 0x00, 0x01, 0x01,
    0x01, 0x00, 0x00, 0x01, 0x01, 0x01, 0x00, 0x00, 0x01, 0x00, 0x01, 0x00, 0x00, 0x00, 0x01, 0x01,
    0x01, 0x00, 0x01, 0x01, 0x01, 0x01, 0x01, 0x00, 0x00, 0x00, 0x01, 0x01, 0x01, 0x00, 0x00, 0x00,
    0x01, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x01, 0x01, 0x00, 0x01, 0x00, 0x00, 0x00, 0x01, 0x01,
    0x00, 0x01, 0x01, 0x01, 0x00, 0x01, 0x01, 0x01, 0x01, 0x00, 0x01, 0x00, 0x01, 0x01, 0x01, 0x00,
    0x00, 0x01, 0x01, 0x01, 0x00, 0x01, 0x01, 0x00, 0x00, 0x00, 0x01, 0x00, 0x01, 0x01, 0x00, 0x00,
    0x00, 0x00, 0x00, 0x00, 0x00, 0x01, 0x01, 0x00, 0x01, 0x01, 0x01, 0x00, 0x01, 0x00, 0x00, 0x01,
    0x01, 0x01, 0x01, 0x01, 0x00, 0x00, 0x01, 0x00, 0x01, 0x00, 0x00, 0x00, 0x01, 0x00, 0x01, 0x01,
    0x01, 0x00, 0x00, 0x00, 0x01, 0x00, 0x01, 0x00, 0x01, 0x00, 0x01, 0x01, 0x00, 0x00, 0x00, 0x00,
    0x01, 0x00, 0x01, 0x00, 0x00, 0x00, 0x01, 0x00, 0x01, 0x00, 0x01, 0x01, 0x01, 0x00, 0x01, 0x00,
    0x00, 0x00, 0x01, 0x01, 0x01, 0x01, 0x01, 0x00, 0x01, 0x00, 0x00, 0x00, 0x00, 0x00, 0x01, 0x00,
    0x01, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x01, 0x01, 0x00, 0x01, 0x00, 0x01, 0x01, 0x00,
]

CHARS = {
    "w" : "wad",
    "s" : "sad",
    "a" : "was",
    "d" : "wsd",
}

def get_counts(key):
    count_1 = 0
    count_2 = 0

    for i in key:
        if i == 's':
            count_1 += 1
        elif i == 'd':
            count_2 += 1
        elif i == 'w':
            count_1 -= 1
        else:
            count_2 -= 1

    return count_1, count_2

def test(key):
    count_1, count_2 = get_counts(key)

    if count_1 == 15 and count_2 == 15:
        print(key)
        sys.exit(0)

    if count_1 < 0 or count_2 < 0 or count_1 > 15 or count_2 > 15:
        return False

    offset = (count_1 << 4) + count_2
    if TABLE[offset] != 0:
        return False

    print(key)

    for c in CHARS[key[-1:]]:
        test(key + c)

    return False

test("s")

Key is:

1	ssddsssassdddssssdssaawaasssddddddwwwwwwddwwwwwdwwdddsssssaassssaasssddddwwddsss

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NDH2K12 Prequals

Written by Nicolas Hureau
2012-03-26 01:00:00

We deemed it was a good idea to have some content to open our blog, therefore we chose to put it online right after the Nuit du Hack 2012 CTF prequals which happened March 24-25th.

After the Codegate where we finished at the 14th place and first French team, we were confident that we could achieve a similar ranking during the NdH2k12 prequals.

We were at 10/12 challenges after 18 hours, but like many other teams, we were blocked by this !@$#? BMP chall at 15500 points. We finally ended up 7th at 17200 points, having all 13 challenges done (yes, 13/12).

We were a bit disappointed by these prequals, and the best résumé we could think of about these 48 hours is: "WTF is happening to the scoreboard?".

Hereafter you will find some writeups and also a few pictures and a timelapse of people working on the prequals in our lab!

Writeups
Timelapse

Video file

Images

Our setup:

We always have security in mind at the LSE, that is why when kushou doesn't want to lose his password, he just pastes it on an IRC channel so that anyone can reminds him!

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DEFCON2K12 Prequals

Written by Nicolas Hureau
2012-06-04 22:56:00

So it was DEFCON 2012 Prequals this week-end! First time for a few of us and definitly first time as "LSE". We planned it carefully, bought food and drinks, defined a sleep schedule to be up and running for the prequals beginning, and of course, none of us respected "the Plan". Too bad.

About the CTF, we noticed that the further you pwn the challenges, the less guessing you have. Hence we had problems (as lots of other teams I guess according to the IRC channel) with ur200, f100, and almost had f200 (we had the picture).

We are quite happy with our finishing rank (20) even though we were secretly hoping to be around place 15.

Hereafter you will find some writeups and also a few pictures and a timelapse of people working on the prequals in our lab!

Writeups
- pwn100
- pwn300
- gb300
- for400
- for500
Timelapse

Video file

Images

Our setup:

2:41:11 until the start:

Did you say Alpha?:

See you next week for Secuinside!

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LSE Blog

Operating systems, computer security, languages theory, and even more!

DEFCON2K12 Prequals: for400 writeup

LSE Week 2012 videos

CSAT (Pierre-Marie de Rodat - 30mn)

ARM architecture (Julien Frêche - 30mn)

Datameat (Victor Apercé - 1h)

FrASM (Pierre-Marie de Rodat - 30mn)

Video game console emulation (Pierre Bourdon & Nicolas Hureau - 1h30)

Possible optimizations for an interpreter (Benoît Zanotti - 30mn)

Routing protocol: BGP4 (Sylvain Laurent - 18h00 - 30mn)

WTF is ACPI? (Ivan Delalande - 1h)

Forensics (Samuel Chevet - 1h)

Tutorial: Arduino development (Augustin Chéron - 1h)

Tutorial: Exploitation techniques (Clément Rouault - 1h)

Introduction to CTFs (Nicolas Hureau - 1h)

WPA2 enterprise and Wi-Fi security (Pierre Bourdon - 1h)

C!: Interface Implementation (Marwan Burelle - 30mn)

Evolution of rootkits (Samuel Chevet - 1h)

Crackme LSE Week (Pierre Bourdon - 30mn)

NDH2K13 crackme300 writeup

NDH2K12 Prequals

Writeups

Timelapse

Images

DEFCON2K12 Prequals

Writeups

Timelapse

Images