RTCP - That's a Lot of Stuff...
Posted on sam. 25 janvier 2020 in CTF
solves : 154
Point : 275
Do you want some numbers? Here, take these numbers. I don't need them anyways. I have too many numbers at home, so go on, take them. Shoves numbers towards the computer screen
31 34 33 20 31 35 36 20 31 32 32 20 31 35 32 20 31 34 33 20 31 31 30 20 31 36 34 20 31 35 32 20 31 31 35 20 31 30 37 20 36 35 20 36 32 20 31 31 35 20 36 33 20 31 31 32 20 31 37 32 20 31 31 35 20 31 32 34 20 31 30 32 20 31 36 35 20 31 34 33 20 36 31 20 37 31 20 31 35 30 20 31 34 33 20 31 35 32 20 31 31 36 20 31 34 36 20 31 31 36 20 31 30 36 20 37 31 20 31 35 32 20 31 31 35 20 31 30 34 20 31 30 32 20 31 31 35 20 31 33 30 20 36 32 20 31 31 35 20 36 30 20 31 34 34 20 31 31 30 20 31 31 36 20 37 31
He have a hex value chain. First, decode it with xxd :
$ echo "31 34 33 20 31 35 36 20 31 32 32 20 31 35 32 20 31 34 33 20 31 31 30 20 31 36 34 20 31 35 32 20 31 31 35 20 31 30 37 20 36 35 20 36 32 20 31 31 35 20 36 33 20 31 31 32 20 31 37 32 20 31 31 35 20 31 32 34 20 31 30 32 20 31 36 35 20 31 34 33 20 36 31 20 37 31 20 31 35 30 20 31 34 33 20 31 35 32 20 31 31 36 20 31 34 36 20 31 31 36 20 31 30 36 20 37 31 20 31 35 32 20 31 31 35 20 31 30 34 20 31 30 32 20 31 31 35 20 31 33 30 20 36 32 20 31 31 35 20 36 30 20 31 34 34 20 31 31 30 20 31 31 36 20 37 31" | xxd -r -p
143 156 122 152 143 110 164 152 115 107 65 62 115 63 112 172 115 124 102 165 143 61 71 150 143 152 116 146 116 106 71 152 115 104 102 115 130 62 115 60 144 110 116 71
Ok. We got a new encoded string. All the characteres are not above 7 (0-7), that is the Octal encoding. We can decode it with printf function with some corrections on this string :
$ printf $(echo "143 156 122 152 143 110 164 152 115 107 65 62 115 63 112 172 115 124 102 165 143 61 71 150 143 152 116 146 116 106 71 152 115 104 102 115 130 62 115 60 144 110 116 71" | sed -E 's/^(.*)/\\\1/' | sed 's/ /\\/g')
cnRjcHtjMG52M3JzMTBuc19hcjNfNF9jMDBMX2M0dHN9
Perfect. We got, again a new encoded string. We don't have the typical padding == of base64 but it's still base64 encoded string.
$ echo -n "cnRjcHtjMG52M3JzMTBuc19hcjNfNF9jMDBMX2M0dHN9" | base64 -d
rtcp{c0nv3rs10ns_ar3_4_c00L_c4ts}
One line version
$ printf $(echo "31 34 33 20 31 35 36 20 31 32 32 20 31 35 32 20 31 34 33 20 31 31 30 20 31 36 34 20 31 35 32 20 31 31 35 20 31 30 37 20 36 35 20 36 32 20 31 31 35 20 36 33 20 31 31 32 20 31 37 32 20 31 31 35 20 31 32 34 20 31 30 32 20 31 36 35 20 31 34 33 20 36 31 20 37 31 20 31 35 30 20 31 34 33 20 31 35 32 20 31 31 36 20 31 34 36 20 31 31 36 20 31 30 36 20 37 31 20 31 35 32 20 31 31 35 20 31 30 34 20 31 30 32 20 31 31 35 20 31 33 30 20 36 32 20 31 31 35 20 36 30 20 31 34 34 20 31 31 30 20 31 31 36 20 37 31" | xxd -r -p | sed -E 's/^(.*)/\\\1/' | sed 's/ /\\/g') | base64 -d
rtcp{c0nv3rs10ns_ar3_4_c00L_c4ts}