Padre — A Password Derivator

A simple password derivator with a focus on long-term stability and flexible use.

Password derivators work by deriving complex passwords based on a single master password. Given a domain, username, and an optional sequence number, padre yields a password of configurable length and characters.

Usage

To generate a password for a user my_username of the website example.com, one would use below command.

padre example.com my_username

Realizing that there are constraints by the website, one can configure the password shall be 32 characters long and consist only of letters, numbers, and ! or $ as below.

padre example.com my_username -l 32 -c 'a-zA-Z0-9!$'

After getting notified by haveibeenpwned the password can be changed by generating another iteration.

padre example.com my_username -i 1 -l 32 -c 'a-zA-Z0-9!$'

The argument to iteration is used as a salt, so users are not limited to numbers there.

Keeping a database of accounts

In order to not have to type stuff like that over and over again, a CSV file containing the accounts can be used in conjunction with grep.

echo "example.com,my_username,1,32,a-zA-Z0-9!$" >> accounts.csv
grep example.com accounts.csv | padre -

Providing the password as a QR code

I often find myself generating passwords that I then need to transfer to my mobile phone. This can be done by having a trustworthy QR code app on the phone and generating a QR code from the password using the qrencode utility.

padre (...) | qrencode -t ansiutf8

Building

Padre can be built on pretty much any Linux system. It has zero dependencies that need to be provided, not even a standard library or run-time.

Internally, padre uses scrypt v1.3.2 as its key-derivation function. To get the standard library out of the picture, the source code of scrypt was modified to some extent. This mostly means throwing out stuff, pasting the remainder together into a single file, and changing a bunch of type aliases.

scrypt in turn uses SHA-256 and an implementation based on the one from the WJCryptLib is provided. Similarly, it was copied here and adapted.

Build padre as follows.

make

Tests are provided via shell script test.sh. To run the script you must have the expect utility available.

Implementation notes

The program is built in one step, following the "jumbo build" principle. There are no external dependencies.

A lot of resources allocated throughout the code are not freed. This is on purpose. It is much easier to just let the OS release the resources when the process exits in such a short-lived program.

• cli.c — the command-line interface parser
• tui.c — the terminal UI for entering the master password
• padre.c — the password-derivation logic
• main.c — entry() point, program flow

The dependency graph is shown below.

                                           ┌──────────┐
                                           │ sha256.c │
                                           └──────────┘
                                                ↑
                                           ┌──────────┐
                                           │ scrypt.c │
                                           └──────────┘
                                                ↑
┌───────┐            ┌───────┐              ┌─────────┐
│ cli.c │            │ tui.c │              │ padre.c │
└───────┘            └───────┘              └─────────┘
    ↑                    ↑                       ↑
    └────────────────────┼───────────────────────┘
                    ┌────────┐
                    │ main.c │
                    └────────┘
                         ↑
                    ┌─────────┐
                    │ linux.c │
                    └─────────┘

UNLICENSE

This is free and unencumbered software released into the public domain.

Anyone is free to copy, modify, publish, use, compile, sell, or distribute this software, either in source code form or as a compiled binary, for any purpose, commercial or non-commercial, and by any means.

In jurisdictions that recognize copyright laws, the author or authors of this software dedicate any and all copyright interest in the software to the public domain. We make this dedication for the benefit of the public at large and to the detriment of our heirs and successors. We intend this dedication to be an overt act of relinquishment in perpetuity of all present and future rights to this software under copyright law.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.

For more information, please refer to https://unlicense.org/