Tags: action misc github githubaction 

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# CheckIn

## How to Setup Environment

move `challenge.yml` to your repository `.github/workflows/challenge.yml

## Write Up

1. GitHub masks secrets when they are printed to the console like `***`
2. the flag is just a few numbers

just make a script to generate payload and it also can prevent others get the flag from your issue

```python

import random
a=[False for i in range(1000000)]
payload = "01234"
count = 1
while True:
n = random.choice("0123456789")
now = payload[-4:] + n
if not a[int(now)]:
payload+=n
count+=1
if count %100 == 0 :
print(f"process :{count}/99999,payload length: {len(payload)}")
with open("payload.txt","w") as f:
f.write(payload)
if count == 99999:
print("finish")
break
```

Original writeup (https://github.com/ccreater222/my-ctf-challenges/tree/master/RCTF2021/CheckIn).