# PHP magic hashes

PHP has some unique features which makes hash "collisions" more easier when using the `==` to compare.

The raw text are taken directly from [spaze/hashes](https://github.com/spaze/hashes/)

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### Floating comparison

Any strings that starts with any numbers of `0`, followed by `e` then ends with only numbers will be treated as zero. An example of such strings are `0e123456` and `00e123456`. [Example code](https://3v4l.org/n8iOp)

This behavior can be extended to numbers, like `'0' == '000'`. [Example code](https://3v4l.org/K9QRb)

With loose comparison `==`, these two example strings will equate to each other as both of them are treated as a zero in the backend.

Sometimes, hashes of specific strings will result in those special strings as an result. Those hashes are called `magic hashes`

Here is an example of such weak comparison for [sha256](https://3v4l.org/Lu7tm).

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### Plaintext

Plaintext.txt just contains some ways to abuse php's weak comparison

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### Truncated text

For bcrypt, passwords are automatically truncated to 72 characters, so as long as the first 72 characters match, the hashes will match.

[Bcrypt example](https://3v4l.org/MsfS0)

Descrypt have similar behavior to bcrypt, but passwords are instead truncated to 8 characters.

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## Pre-hashed

<!--- Modified from https://github.com/spaze/hashes?tab%253Dreadme-ov-file#pbkdf2-hmac-sha1-pbkdf2-hmac-sha224-pbkdf2-hmac-sha256-->

These are a different kind of magic hashes, they don't need the loose comparison operator `==` and work even with strict comparison `===`.

If you use a password longer than 64 bytes and hash it with PBKDF2-HMAC-SHA1, it is first pre-hashed with SHA1.

For example, `PBKDF2-HMAC-SHA1(password1) === PBKDF2-HMAC-SHA1(password2)` as `sha1(password1) === bin2hex(password2)`.

This behavior can also be seen in `PBKDF2-HMAC-SHA224` and `PBKDF2-HMAC-SHA256`.