First public CTF in 2020! 85th place, not bad, A good start to the year!
Note: The flags for this CTF is case-insensitive
# Forensics
Doc. Holmes-----```Prompt: Sherlock got it on his super secret channels. You have received a copy of mail. Is everything okay with it?```
Pretty simple, using ```file some.file``` gives us ```Microsoft Word 2007+```, renamed it, then open it up and it gives us a piece of work in a word document with a few random pictures.  After extracting with binwalk, I went to the ```_some.doc.extracted/word/media```, then noticed that the original document had 2 pictures shown, but this contained 3. So opened ```image3.jpg``` then got the flag.![](https://raw.githubusercontent.com/Immobility/CTF-Writeups/master/sarCTF2020/images/image3.jpg)```FLAG{prominentplace}```
Blogger-----```Prompt: Recently, John's keys began to be pressed by themselves when he runs his blog. You need to figure out what's the matter.```
USB inputs can be traced with pcap files, the USB HID usage tables can be found on USB.org. The manual can be found [here](https://www.usb.org/sites/default/files/documents/hut1_12v2.pdf) Page 53. I then traced source from 1.7.1 to host because of remote usage, then traced the last few bytes of the inputs. 
Since we're looking for ```FLAG```, I looked for the usage IDs, 09, 0F, 04, 0A, respectively. Which leads to packet 541.![](https://raw.githubusercontent.com/Immobility/CTF-Writeups/master/sarCTF2020/images/usb1.png) F
![](https://raw.githubusercontent.com/Immobility/CTF-Writeups/master/sarCTF2020/images/usb2.png) L
![](https://raw.githubusercontent.com/Immobility/CTF-Writeups/master/sarCTF2020/images/usb3.png) A
![](https://raw.githubusercontent.com/Immobility/CTF-Writeups/master/sarCTF2020/images/usb4.png) G
Decrypt it up to the ```}``` symbol and you get```FLAG{like_a_b100dh0und}```
# Reverse
crossw0rd-----```Prompt: While the children were playing toys, Sherlock was solving crosswords in large volumes.```
After disassembling the ELF file, we get![](https://raw.githubusercontent.com/Immobility/CTF-Writeups/master/sarCTF2020/images/cross1.png)Get into the ```_Z5checkv``` and we see![](https://raw.githubusercontent.com/Immobility/CTF-Writeups/master/sarCTF2020/images/cross2.png)The top part is taking in an input, hence we see the ```_scanf``` function. Let's check the ```_Z1ePc``` function.
Intersting, looks like there is a function inside the function since it calls. Let's try going in the loop and find out.
```Func _Z1ePc```![](https://github.com/Immobility/CTF-Writeups/blob/master/sarCTF2020/images/cross3.1.png)
```Func _Z1bPc```![](https://github.com/Immobility/CTF-Writeups/blob/master/sarCTF2020/images/cross3.2.png)
```Func _Z1dPc```![](https://github.com/Immobility/CTF-Writeups/blob/master/sarCTF2020/images/cross3.3.png)
```Func _Z1fPc```![](https://github.com/Immobility/CTF-Writeups/blob/master/sarCTF2020/images/cross3.4.png)
```Func _Z1cPc```![](https://github.com/Immobility/CTF-Writeups/blob/master/sarCTF2020/images/cross3.5.png)
```Func _Z1aPc```![](https://github.com/Immobility/CTF-Writeups/blob/master/sarCTF2020/images/cross3.6.png)
So we start in *```_Z1ePc```*, let's get the values that we need:
add rax, 7cmp     al, 35h ; '5'
add rax, 11hcmp     al, 67h ; 'g'
add rax, 2cmp     al, 41h ; 'A'
*```_Z1bPc```*
add rax, 0Fhcmp     al, 69h ; 'i'
add rax, 9cmp     al, 72h ; 'r'
add rax, 1cmp     al, 4Ch ; 'L'
*```_Z1dPc```*
add rax, 0Ahcmp     al, 33h ; '3'
add rax, 12hcmp     al, 7Dh ; '}'
add rax, 6cmp     al, 61h ; 'a'
*```_Z1fPc```*
cmp     al, 46h ; 'F'
add rax, 0Ehcmp     al, 35h ; '5'
add rax, 10hcmp     al, 6Eh ; 'n'
*```_Z1cPc```*
add rax, 3cmp     al, 47h ; 'G'
add rax, 0Bhcmp     al, 76h ; 'v'
add rax, 5cmp     al, 33h ; '3'
*```_Z1aPc```*
add rax, 4cmp     al, 7Bh ; '{'
add rax, 0Chcmp     al, 33h ; '3'
add rax, 8cmp     al, 79h ; 'y'
add rax, 0Dhcmp     al, 72h ; 'r'
Since we loaded our string to rax, think of the string as an array. rax is our array and basically adding to it shows us the position of the array that we're trying to compare the character to. So what do we do? Of course, put the numbers that are getting "added" to rax in order. The highest number we see is 12h, which means there are 19 characters in the string because we need to include the 0th array value. After rearranging them, we get the flag:```FLAG{3a5yr3v3r5ing}```
Let's check!![](https://github.com/Immobility/CTF-Writeups/blob/master/sarCTF2020/images/cross4.png)
# Misc
True Detective-----```Prompt: And now it's time to show the skills of a real detective! https://clck.ru/MCop6```We need to figure out where the each place is. However, there's a small trick I discovered. First, go to the developer tools on the browser you're using and take a look at the debugger menu on the google docs and look at the viewform. ![](https://raw.githubusercontent.com/Immobility/CTF-Writeups/master/sarCTF2020/images/truedet1.png)
Next, go all the way to the bottom as that's where the form stores the warnings.
![](https://raw.githubusercontent.com/Immobility/CTF-Writeups/master/sarCTF2020/images/truedet2.png)
There we go! Our prompt answers and the flag pieces!
```,"1 - FLAG{08"]]]],null,null,null,null,[["1cTysniECWio21dKH90wnnzNxlB4gKBJI7Bri1Q_K4moAtg",null,[740,385,0]]]],[2014750817,"What is the name of this place?",null,0,[[1092335700,null,0,null,[[4,300,["(bridport|Bridport)"],"2 - c49c3d9a"]]]],null,null,null,null,[["1sd8oiCWcjd1_HiCrOA2f1hrgkknzJvT_Y-tVgx5qjBanKw",null,[740,417,0]]]],[771036932,"Very beautiful Park where Sherlock likes to walk. Where is it?",null,0,[[1600364512,null,0,null,[[4,300,["(finsbury|Finsbury)"],"3 - e8898343"]]]],null,null,null,null,[["1-w_MvKBaer5I78ICXo70E94lH4vKSPmCRekszxbOblJRvA",null,[740,377,0]]]],[302390155,"Every Englishman has been to this square at least once",null,0,[[661956933,null,0,null,[[4,300,["(euston|Euston)"],"4 - 7729747b"]]]],null,null,null,null,[["1sGu1uvZD9tXdbS0ypGTsI05LDj8Bd1U03VV_vjDLI3bY6A",null,[740,385,0]]]],[1070034509,"Which Embassy building is shown in the photo",null,0,[[2072641709,null,0,null,[[4,300,["(hungary|Hungary)"],"5 - cf1be8}"]```
```FLAG{08c49c3d9ae88983437729747bcf1be8}```
# Crypto
Invitation-----```Prompt: Sherlock doesn't like going to parties. But this time an invitation came to him, which he could not refuse.```
A dancing men puzzle!![](https://github.com/Immobility/CTF-Writeups/blob/master/sarCTF2020/images/task_3e55f673c10d-1.png)All we need to do here is to look for the signs that look like: ![](https://raw.githubusercontent.com/Immobility/CTF-Writeups/master/sarCTF2020/images/dancing1.png)
The flag starts from the right side: ![](https://raw.githubusercontent.com/Immobility/CTF-Writeups/master/sarCTF2020/images/dancing2.png)
Which translates to:flag{discoinSaratov}. But this didn't work, so we formatted to ```flag{disco_in_Saratov}```
# PPC
Mind palace I-----I should get back to practicing scripting.```Prompt: It looks like the situation is hopeless, there is no time to think. However, you can use the mind palace and solve all problems instantly.
nc 212.47.229.1 33001```This was at first tricky, since I thought that it had to do with Python pacakges since it kept writing ```pip``` and ```piiiip```, but turns out it was a Morse code, with ```pip``` being ```.``` and ```piiiip``` being ```-```
I logged the results by writing ```nc 212.47.229.1 33001 > res.log```, then using vim, by first writing: ```%s/pip/./g``` then ```%s/piiiip/-/g```. Then I removed the ^M s (```%s/^M//g  note;```), then decoded the input by removing the spaces first, then finding for similar morse that looked like ```..-. .-.. .- --.``` then went on from there. It turns out around 3 sentences from the Adventure of the Empty House chapter from Return of Sherlock Holmes. ```..-. .-.. .- --. ... .... . .-. .-.. --- -.-. -.- .-.. .. -.- . ... -.-- --- ..- .-. -- --- .-. ... . ```
```flag{sherlocklikesyourmorse}```