BTLO - Secrets

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BTLO - Secrets

Challenge: https://blueteamlabs.online/home/challenge/secrets-85aa2bb3a9

:::spoiler TOC [TOC] :::

Scenario

You’re a senior cyber security engineer and during your shift, we have intercepted/noticed a high privilege actions from unknown source that could be identified as malicious. We have got you the ticket that made these actions. You are the one who created the secret for these tickets. Please fix this and submit the low privilege ticket so we can make sure that you deserve this position. Here is the ticket:

eyJ0eXAiOiJKV1QiLCJhbGciOiJIUzI1NiJ9.eyJmbGFnIjoiQlRMe180X0V5ZXN9IiwiaWF0Ijo5MDAwMDAwMCwibmFtZSI6IkdyZWF0RXhwIiwiYWRtaW4iOnRydWV9.jbkZHll_W17BOALT95JQ17glHBj9nY-oWhT1uiahtv8

==Q1==

Can you identify the name of the token? (Format: String)

Recon

看到三段用.拼起來就直覺是jwt

:::spoiler Flag Flag: jwt :::

==Q2==

What is the structure of this token? (Format: Section.Section.Section)

Recon

Common Sense就是header + payload + signature 圖片

:::spoiler Flag Flag: header.payload.signature :::

==Q3==

What is the hint you found from this token? (Format: String)

Recon

這一題真的不知道在衝三小，最後參考1才知道，但實在是太隱晦了，不管是問題還是答案出乎意料

:::spoiler Flag Flag: _4_Eyes :::

==Q4==

What is the Secret? (Format: String)

Recon

這個直覺就是要爆破簽署的secrets，因為看來看去都沒有其他地方有leak出來，所以可以用hashcat或是john爆破出來

Exploit

  • Hashcat - Hacking JWT Tokens: Bruteforcing Weak Signing Key (Hashcat) 
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      $ echo 'eyJ0eXAiOiJKV1QiLCJhbGciOiJIUzI1NiJ9.eyJmbGFnIjoiQlRMe180X0V5ZXN9IiwiaWF0Ijo5MDAwMDAwMCwibmFtZSI6IkdyZWF0RXhwIiwiYWRtaW4iOnRydWV9.jbkZHll_W17BOALT95JQ17glHBj9nY-oWhT1uiahtv8'> jwt.txt
  $ hashcat -a 3 -m 16500 jwt.txt ?a?a?a?a
  hashcat (v6.2.6) starting

  OpenCL API (OpenCL 3.0 PoCL 4.0+debian  Linux, None+Asserts, RELOC, SPIR, LLVM 15.0.7, SLEEF, DISTRO, POCL_DEBUG) - Platform #1 [The pocl project]
  ==================================================================================================================================================
  * Device #1: cpu-sandybridge-Intel(R) Core(TM) i7-10700F CPU @ 2.90GHz, 2910/5884 MB (1024 MB allocatable), 4MCU

  Minimum password length supported by kernel: 0
  Maximum password length supported by kernel: 256

  Hashes: 1 digests; 1 unique digests, 1 unique salts
  Bitmaps: 16 bits, 65536 entries, 0x0000ffff mask, 262144 bytes, 5/13 rotates

  Optimizers applied:
  * Zero-Byte
  * Not-Iterated
  * Single-Hash
  * Single-Salt
  * Brute-Force

  Watchdog: Temperature abort trigger set to 90c

  Host memory required for this attack: 1 MB

  eyJ0eXAiOiJKV1QiLCJhbGciOiJIUzI1NiJ9.eyJmbGFnIjoiQlRMe180X0V5ZXN9IiwiaWF0Ijo5MDAwMDAwMCwibmFtZSI6IkdyZWF0RXhwIiwiYWRtaW4iOnRydWV9.jbkZHll_W17BOALT95JQ17glHBj9nY-oWhT1uiahtv8:bT!0

  Session..........: hashcat
  Status...........: Cracked
  Hash.Mode........: 16500 (JWT (JSON Web Token))
  Hash.Target......: eyJ0eXAiOiJKV1QiLCJhbGciOiJIUzI1NiJ9.eyJmbGFnIjoiQl...iahtv8
  Time.Started.....: Sun Dec 31 03:50:45 2023 (7 secs)
  Time.Estimated...: Sun Dec 31 03:50:52 2023 (0 secs)
  Kernel.Feature...: Pure Kernel
  Guess.Mask.......: ?a?a?a?a [4]
  Guess.Queue......: 1/1 (100.00%)
  Speed.#1.........:  2621.9 kH/s (6.10ms) @ Accel:128 Loops:47 Thr:1 Vec:8
  Recovered........: 1/1 (100.00%) Digests (total), 1/1 (100.00%) Digests (new)
  Progress.........: 16902144/81450625 (20.75%)
  Rejected.........: 0/16902144 (0.00%)
  Restore.Point....: 177664/857375 (20.72%)
  Restore.Sub.#1...: Salt:0 Amplifier:0-47 Iteration:0-47
  Candidate.Engine.: Device Generator
  Candidates.#1....: s5VH -> RT^a
  Hardware.Mon.#1..: Util: 95%

  Started: Sun Dec 31 03:50:44 2023
  Stopped: Sun Dec 31 03:50:53 2023
  • John - Hacking JWT Tokens: Bruteforcing Weak Signing Key (JohnTheRipper) 這要取決於wordlist有沒有，所以我只是先以secret=1234，然後用john爆破 圖片 
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      $ echo 'eyJ0eXAiOiJKV1QiLCJhbGciOiJIUzI1NiJ9.eyJmbGFnIjoiQlRMe180X0V5ZXN9IiwiaWF0Ijo5MDAwMDAwMCwibmFtZSI6IkdyZWF0RXhwIiwiYWRtaW4iOnRydWV9.2kwB24fBrrmotFu9cdeRb1EMg1kRfGlLQPvhE1OUtp0'> jwt.txt
  $ john jwt.txt --wordlist=/usr/share/wordlists/rockyou.txt --format=HMAC-SHA256                                                                                                                 
  Using default input encoding: UTF-8
  Loaded 1 password hash (HMAC-SHA256 [password is key, SHA256 128/128 AVX 4x])
  Will run 4 OpenMP threads
  Press 'q' or Ctrl-C to abort, almost any other key for status
  1234             (?)     
  1g 0:00:00:00 DONE (2023-12-31 03:46) 100.0g/s 409600p/s 409600c/s 409600C/s 123456..oooooo
  Use the "--show" option to display all of the cracked passwords reliably
  Session completed.

:::spoiler Flag Flag: bT!0 :::

==Q5==

Can you generate a new verified signature ticket with a low privilege? (Format: String.String.String)

Recon

我們知道了secrets===bT!0==，所以我們可以用這個secrets簽章新的payload 圖片

:::spoiler Flag Flag: eyJ0eXAiOiJKV1QiLCJhbGciOiJIUzI1NiJ9.eyJmbGFnIjoiQlRMe180X0V5ZXN9IiwiaWF0Ijo5MDAwMDAwMCwibmFtZSI6IkdyZWF0RXhwIiwiYWRtaW4iOmZhbHNlfQ.nMXNFvttCvtDcpswOQA8u_LpURwv6ZrCJ-ftIXegtX4 :::

Reference

  1. BTLO — Secrets Walkthrough ↩