Purrito Bin (=♡ᆺ♡=)

ultra fast, minimalistic, encrypted command line paste-bin

Features and Highlights

• Very lightweight: 2-3 MB of RAM on average.
• Listen on multiple address/port combinations, both IPv4 and IPv6.
• Configurable paste size limit.
• Auto-cleaning of pastes, with configurable paste lifetime at submission time:
  • domain.tld/{day,week,month}
  • domain.tld/<time-in-minutes>
  • domain.tld/0 for a paste with infinite life.

• Paste storage in plain text, easy to integrate with all web servers (Apache, Nginx, etc.).
• Encrypted pasting similar to PrivateBin.
• Optional https support for secure communication.
• Tiny code base, less than 1000 lines of code, for very easy auditing.
• Well documented, man purrito.

• uSockets
• uWebSockets
• lmdbxx

If these are not available in an OS's repositories, they can be manually installed by following the steps in the GitHub workflow

Compilation

$ meson --prefix "/usr" -C build
$ ninja -C build
$ sudo ninja -C build install

The server is run using the command purrito. To quickly view the available options:

$ purrito -h
usage: purrito [-abcdefghijklmnpqrstvwxz] -d domain [-a slug_characters]
               [-b max_database_size] [-c public_cert_file] [-e dhparams_file]
               [-f index_file] [-g slug_size] [-h] [-i bind_ip]
               [-j autoclean_interval] [-k private_key_file] [-l]
               [-m max_paste_size] [-n server name] [-p bind_port]
               [-q default_time_limit] [-r max_retries] [-s storage_directory]
               [-t] [-v header_value] [-w passphrase] [-x header]
               [-z database_directory]

For an indepth explanation, there is a man page provided.

$ man purrito

Make sure that whatever link is provided to the -d domain option, is also able to serve the paste.html from this repository.

Client (=｀ﻌ´=) Shell client definitions

Define these functions somewhere in the dot files of the desired shell (they work on all POSIX compliant shells).

: ${P_SERVER=https://bsd.ac}
: ${P_PORT=42069}
: ${P_MAXTIME=30}


POSIX shell client to upload standard message

purr() {
    curl --silent --max-time "${P_MAXTIME}" --data-binary "@${1:-/dev/stdin}" "${P_SERVER}:${P_PORT}"
}

POSIX shell client to upload encrypted message

meow() {
    # generate a 256 byte random key
    # for using the aes-256-cbc cipher
    key="$(openssl rand -hex 32)"
    iv="$(openssl rand -hex 16)"
    # calculate its encryption and upload it
    url="$(openssl enc -aes-256-cbc -K ${key} -iv ${iv} -e -base64 -A < ${1:-/dev/stdin} | purr)"
    printf %s\n "${url%\/}/paste.html#${url##\/}${key}${iv}"
    unset key iv url
}

POSIX shell client to decrypt the message

meowd() {
    url="$1"
    baseurl="${url%\/}"
    vals="${url###}"
    paste=$(printf %s\n "${vals}" | cut -d'' -f1)
    key=$(printf %s\n "${vals}" | cut -d'' -f2)
    iv=$(printf %s\n "${vals}" | cut -d'_' -f3)
    curl --max-time "${P_MAXTIME}" --write-out "\n" --silent "${baseurl}/${paste}" | openssl enc -aes-256-cbc -base64 -d -K ${key} -iv ${iv}
    unset url baseurl vals paste key iv
}

The stdout from a command can be pasted or from the cat/head/tail of a file or the input from a file or from the command line.

$ purr c00lfile.txt
https://bsd.ac/purrit0


$ purr < h0tfile.txt
https://bsd.ac/purri1o

$ echo Hello world. | purr
https://bsd.ac/d4nklit

$ purr
This is my input
it can span multiple lines
<Ctrl-d to exit>
https://bsd.ac/curlpr0

$ meow
really cool paste
<Ctrl-d to exit>
https://bsd.ac/paste.html#329r1ml_9f5d0f2928b33c2a6a0752811170735af16c8eecfa208e1bdb84d831427be82b_fd579e101a3d31d0362f0ec6473573ad

In a encrypted storage setting, the paste is encrypted before sending it to the server. Now the server will only be used as a storage bin and even in case of a non-https connection, it is guaranteed that no one else will be able to read the data that was sent.

How does it work?

Steps automatically done by the provided clients, on the client side:

• Randomly generate an ecryption key and initialization vector iv.
• Encrypt the data using said key and iv, the encrypted data is called the cipher.
• Send the cipher to the pastebin and get a standard paste url as above, which will be converted to the form

   https://bsd.ac/paste.html#pasteID_key_iv

The standard client is meow, a companion to the above purr, which is also POSIX compliant and should work in all shells. It has exactly the same usage as purr, so please look at those examples to see how to use it. The only dependency on the client side is the presence of LibreSSL or OpenSSL, to do the encryption.

There will be other clients in the clients folder, added on demand for other platforms, which will do all this automatically. Pull requests for other clients are highly welcome.

Why is this secure?

• All the encryption is done on the client side.
• Only the cipher is sent to PurritoBin.
• The url only contains the encrypted cipher and has no knowledge of the actual data.
• When visiting the html webpage the key is in the hash property of the webpage, which is never sent to the server.
• All decryption is done inside the browser, using javascript, Crypto JS on the client side.

NOTE: Anyone who has the full link is going to be able to read the decrypted text. Only send the full hash included url to trusted parties, through a secure communication channel.

Design principles

The aim is to follow the KISS philosophy and only aim to do one thing. There are tools which manage to do the other things better, so make the current one as integrable as possible.

Purrito Bin is very, very easily integrated into any setup. It runs as an unprivileged user in a single directory without access to any other systems resource.

In OpenBSD, it is automatically pledges and unveils the bare minimum to function, so even in the case of a bug in the code, an attacker has no access to the system.

Pull requests to harden the code by default in linux and other operating systems are highly welcome.

Extras System services

The services directory consists of OpenRC and SystemD service files. They need the purritobin user and group to exist.

Pure C client

ericonr has made a very nice C client, which also supports encrypted pastes - https://github.com/ericonr/purr-c It uses BearSSL and is very instructive for all who wish to get a small example of using SSL in C together with networking.

Credits

uNetworking: for their uWebSockets and uSockets
brix: for their crypto-js
solusipse: for their fiche pastebin