## Downloads
{% file src="" %}
## Solution
This is a tough one with very little solves but I still attempted it because I did a similar challenge in HTB last year [here](https://arne-ctf.gitbook.io/ctf/2024/htb-cyber-apocalypse/misc-multidigilingual). I thought I could breeze past this real quick but it turned out to be more challenging than I thought.
The challenge is straight forward - write a **Perl-Python-JavaScript** file-read polyglot. Firstly, let's write the file-read code for each language:
#### Python
```python
print(open('flag.txt').read())
```
#### Perl
```perl
open(my $file, 'flag.txt');print(<$file>);
```
#### JavaScript
```javascript
console.log(require('fs').readFileSync('flag.txt','utf8'))
```
Combining **Perl+Python:**
```perl
q="""=;open(my $file, 'flag.txt');print(<$file>);#""";print(open('flag.txt').read())
```
This is simple, put the python code behind the '#' symbol and it will be treated as a comment by Perl. Similarly in python, the Perl code is treated as comment when put between the triple double quotes. Here's the hard part - that is invalid JavaScript.
Node error
Anyway, I modified the validation script slightly such that it prints the individual interpreter's output:
```bash
#!/usr/bin/env bash
set -eo pipefail
wrong() {
printf "EXTREMELY LOUD INCORRECT BUZZER!!!\n"
}
trap wrong ERR
code=$(cat)
printf '%s' "$code" | perl -c
printf '%s' "$code" | python3 -c 'import sys,ast; ast.parse(sys.stdin.read())'
printf '%s' "$code" | node -e "const fs=require('fs'), src=fs.readFileSync(0,'utf8'); require('vm').createScript(src)"
perl_out=$(printf '%s' "$code" | perl -)
py_out=$(printf '%s' "$code" | python3 -)
js_out=$(printf '%s' "$code" | node -)
printf 'Perl output:\n%s\n\n' "$perl_out"
printf 'Python output\n%s\n\n' "$py_out"
printf 'JS output\n%s\n\n' "$js_out"
if [[ "$perl_out" == "$py_out" && "$perl_out" == "$js_out" ]]; then
printf "Your triglot compiles!! Here's your output:\n"
printf '%s\n' "$py_out"
else
exit 1
fi
```
I spent a good maybe 5 hours going nowhere until I found this post, .
My final script is:
```javascript
0//1;q=0;print(open('flag.txt').read());'''=;open(my $file, 'flag.txt');print(<$file>);q[
for(x=1,z=(a='')=>a;x;)console.log(require('fs').readFileSync('flag.txt','utf8')+(x--,z()))//]#'''
```
As you can see from the syntax highlighting, it mostly made use of **'//'** in JavaScript to comment most of the other code out. Other thing worth mentioning is the odd **for** loop. To be honest, I still don't quite understand how this loop works. There are only 2 expressions (notice there's only 2 semicolons) and I'd expect the 2nd expression to be a condition in a typical loop but it's not. The decrement is also done in the function itself rather than the '**for'** statement. If anyone could explain to me how this works do reach out to me :)
