Stripe-CTF Level-1

miner.rb

require 'digest/sha1'

@ctf_username = "user-8lmmcgvw"

def addToLedger
	user_in_ledger = false
	File.open("LEDGER.txt").each_line do |line|
	    if line.match(/^#{@ctf_username}:/)
	    	user_in_ledger = true
	    end
	end
	unless user_in_ledger
		`echo "#{@ctf_username}: 1" >> LEDGER.txt`
	end
	`git add LEDGER.txt`
end

def reset
	`git fetch && git reset --hard origin/master`
    addToLedger()
	@difficulty = File.read("difficulty.txt").tr("\n","")
	@tree = `git write-tree`
	@parent = `git rev-parse HEAD`
	@timestamp = Time.now.to_i
end


reset()

threadA = Thread.fork do
	loop do
		remote_sha=`git ls-remote origin -h refs/heads/master 2>/dev/null`.sub("\trefs/heads/master\n","")
		local_sha = `git rev-parse HEAD`.sub("\n","")

		if remote_sha != local_sha
			print "remote_sha: #{remote_sha} != local_sha: #{local_sha}\n\n" 
			reset()
		end
		sleep 10
	end
end

counter = 0;
loop do
	content="tree #{@tree}parent #{@parent}author CTF user <[email protected]> #{@timestamp} +0000
committer CTF user <[email protected]> #{@timestamp} +0000

Give me a Gitcoin

#{counter}"
	fix_content = content + "\n"
	store = "commit #{fix_content.length}\0#{fix_content}"
	sha1 = Digest::SHA1.hexdigest(store)
  	if sha1 < @difficulty
  		threadA.kill
  		print "Mined a Gitcoin with commit: #{sha1}"
  		`git hash-object -t commit --stdin -w <<< "#{content}"`
	    `git reset --hard "#{sha1}"`
	    `git push origin master`
	    break
	end
	counter+=1
end