Module cvtool.core.checksum

Tools for adding and validating checksums

"""
Tools for adding and validating checksums
"""
import hashlib
import json


def calculate_checksum(dictionary, overwrite=True, checksum_location='version_metadata'):
    """
    Calculate the checksum for a dictionary and add it to the Header.

    Parameters:
    dictionary (dict): The dictionary to set the checksum for.
    overwrite (bool): Overwrite the existing checksum (default True).
    checksum_location (str): Sub-dictionary to look for / add the checksum to.

    Raises:
    RuntimeError: If the 'checksum' key already exists and 'overwrite' is False.
    """
    if 'checksum' in dictionary[checksum_location]:
        if not overwrite:
            raise RuntimeError('Checksum already exists.')
        del dictionary[checksum_location]['checksum']
    checksum = _checksum(dictionary)
    dictionary[checksum_location]['checksum'] = checksum


def validate_checksum(dictionary, checksum_location='version_metadata'):
    """
    Validate the checksum in the dictionary.

    Parameters:
    dictionary (dict): The dictionary containing the 'checksum' to validate.
    checksum_location (str): Sub-dictionary to look for / add the checksum to.

    Raises:
    KeyError: If the 'checksum' key does not exist.
    RuntimeError: If the 'checksum' value is invalid.
    """
    if 'checksum' not in dictionary[checksum_location]:
        raise KeyError('No checksum to validate')
    dictionary_copy = _deepcopy(dictionary)
    del dictionary_copy[checksum_location]['checksum']
    checksum = _checksum(dictionary_copy)
    if dictionary[checksum_location]['checksum'] != checksum:
        msg = (
            'Expected checksum: "{}"\n'
            'Calculated checksum: "{}"'
        ).format(dictionary[checksum_location]['checksum'], checksum)
        raise RuntimeError(msg)


def _checksum(obj):
    obj_str = json.dumps(obj, sort_keys=True)
    checksum_hex = hashlib.md5(obj_str.encode('utf-8')).hexdigest()
    return 'md5: {}'.format(checksum_hex)

Functions

def calculate_checksum(dictionary, overwrite=True, checksum_location='version_metadata')

Calculate the checksum for a dictionary and add it to the Header.

Parameters: dictionary (dict): The dictionary to set the checksum for. overwrite (bool): Overwrite the existing checksum (default True). checksum_location (str): Sub-dictionary to look for / add the checksum to.

Raises: RuntimeError: If the 'checksum' key already exists and 'overwrite' is False.

Expand source code

def calculate_checksum(dictionary, overwrite=True, checksum_location='version_metadata'):
    """
    Calculate the checksum for a dictionary and add it to the Header.

    Parameters:
    dictionary (dict): The dictionary to set the checksum for.
    overwrite (bool): Overwrite the existing checksum (default True).
    checksum_location (str): Sub-dictionary to look for / add the checksum to.

    Raises:
    RuntimeError: If the 'checksum' key already exists and 'overwrite' is False.
    """
    if 'checksum' in dictionary[checksum_location]:
        if not overwrite:
            raise RuntimeError('Checksum already exists.')
        del dictionary[checksum_location]['checksum']
    checksum = _checksum(dictionary)
    dictionary[checksum_location]['checksum'] = checksum

def validate_checksum(dictionary, checksum_location='version_metadata')

Validate the checksum in the dictionary.

Parameters: dictionary (dict): The dictionary containing the 'checksum' to validate. checksum_location (str): Sub-dictionary to look for / add the checksum to.

Raises: KeyError: If the 'checksum' key does not exist. RuntimeError: If the 'checksum' value is invalid.

Expand source code

def validate_checksum(dictionary, checksum_location='version_metadata'):
    """
    Validate the checksum in the dictionary.

    Parameters:
    dictionary (dict): The dictionary containing the 'checksum' to validate.
    checksum_location (str): Sub-dictionary to look for / add the checksum to.

    Raises:
    KeyError: If the 'checksum' key does not exist.
    RuntimeError: If the 'checksum' value is invalid.
    """
    if 'checksum' not in dictionary[checksum_location]:
        raise KeyError('No checksum to validate')
    dictionary_copy = _deepcopy(dictionary)
    del dictionary_copy[checksum_location]['checksum']
    checksum = _checksum(dictionary_copy)
    if dictionary[checksum_location]['checksum'] != checksum:
        msg = (
            'Expected checksum: "{}"\n'
            'Calculated checksum: "{}"'
        ).format(dictionary[checksum_location]['checksum'], checksum)
        raise RuntimeError(msg)