Core Class#

class quart_bcrypt.Bcrypt(app: Optional[Quart] = None, log_rounds: int = 12, prefix: Union[str, bytes] = '2b', long_passwords: bool = False)#

Bcrypt class container for password hashing and checking logic using bcrypt, of course. This class may be used to intialize your Quart app object. The purpose is to provide a simple interface for overriding Werkzeug’s built-in password hashing utilities.

Although such methods are not actually overriden, the API is intentionally made similar so that existing applications which make use of the previous hashing functions might be easily adapted to the stronger facility of bcrypt.

To get started you will wrap your application’s app object something like this:

app = Quart(__name__)
bcrypt = Bcrypt(app)

Now the two primary utility methods are exposed via this object, bcrypt. So in the context of the application, important data, such as passwords, could be hashed using this syntax:

password = 'hunter2'
pw_hash = bcrypt.generate_password_hash(password)

Once hashed, the value is irreversible. However in the case of validating logins a simple hashing of candidate password and subsequent comparison. Importantly a comparison should be done in constant time. This helps prevent timing attacks. A simple utility method is provided for this:

candidate = 'secret'
bcrypt.check_password_hash(pw_hash, candidate)

If both the candidate and the existing password hash are a match check_password_hash returns True. Otherwise, it returns False.

Namespacing Issues

It’s worth noting that if you use the format, bcrypt = Bcrypt(app) you are effectively overriding the bcrypt module. Though it’s unlikely you would need to access the module outside of the scope of the extension be aware that it’s overriden.

Alternatively consider using a different name, such as quart_bcrypt = Bcrypt(app) to prevent naming collisions.

Additionally a configuration value for BCRYPT_LOG_ROUNDS may be set in the configuration of the Quart app. If none is provided this will internally be assigned to 12. (This value is used in determining the complexity of the encryption, see bcrypt for more details.)

You may also set the hash version using the BCRYPT_HASH_PREFIX field in the configuration of the Quart app. If not set, this will default to 2b. (See bcrypt for more details)

By default, the bcrypt algorithm has a maximum password length of 72 bytes and ignores any bytes beyond that. A common workaround is to hash the given password using a cryptographic hash (such as sha256), take its hexdigest to prevent NULL byte problems, and hash the result with bcrypt. If the BCRYPT_HANDLE_LONG_PASSWORDS configuration value is set to True, the workaround described above will be enabled. Warning: do not enable this option on a project that is already using Quart-Bcrypt, or you will break password checking. Warning: if this option is enabled on an existing project, disabling it will break password checking.

Parameters

app – The Quart application object. Defaults to None.

init_app(app: Quart, log_rounds: int = 12, prefix: str = '2b', long_passwords: bool = False) → None#

Initalizes the application with the extension.

Parameters

app – The Quart application object.

generate_password_hash(password: Union[str, bytes], rounds: Optional[int] = None, prefix: Optional[Union[str, bytes]] = None) → bytes#

Generates a password hash using bcrypt. Specifying rounds sets the log_rounds parameter of bcrypt.gensalt() which determines the complexity of the salt. 12 is the default value. Specifying prefix sets the prefix parameter of bcrypt.gensalt() which determines the version of the algorithm used to create the hash.

Example usage of generate_password_hash might look something like this:

pw_hash = bcrypt.generate_password_hash('secret', 10)
Parameters

  • password – The password to be hashed.

  • rounds – The optional number of rounds.

  • prefix – The algorithm version to use.

check_password_hash(pw_hash: bytes, password: str) → bool#

Tests a password hash against a candidate password. The candidate password is first hashed and then subsequently compared in constant time to the existing hash. This will either return True or False.

Example usage of check_password_hash would look something like this:

pw_hash = bcrypt.generate_password_hash('secret', 10)
bcrypt.check_password_hash(pw_hash, 'secret') # returns True
Parameters

  • pw_hash – The hash to be compared against.

  • password – The password to compare.

async async_generate_password_hash(password: Union[str, bytes], rounds: Optional[int] = None, prefix: Optional[Union[str, bytes]] = None) → bytes#

Wraps the generate_password_hash function in Quarts run_sync function to ensure the sync function is run within the event loop.

Example usage of async_generate_password_hash might look something like this:

pw_hash = await bcrypt.async_generate_password_hash('secret', 10)
Parameters

  • password – The password to be hashed.

  • rounds – The optional number of rounds.

  • prefix – The algorithm version to use.

async async_check_password_hash(pw_hash: bytes, password: str) → bool#

Wraps the check_password_hash function in Quarts run_sync function to ensure the sync function is run within the event loop.

Example usage of async_check_password_hash would look something like this:

pw_hash = await bcrypt.async_generate_password_hash('secret', 10)
await bcrypt.check_password_hash(pw_hash, 'secret') # returns True
Parameters

  • pw_hash – The hash to be compared against.

  • password – The password to compare.