def decode_ipfs_hash(hex_hash):
""" Decode a Base58 IPFS hash from a 32 byte hex string """
if hex_hash.startswith('0x'):
hex_hash = remove_0x_prefix(hex_hash)
if not hex_hash.startswith('1220'):
hex_hash = '1220' + hex_hash
return multihash.to_b58_string(multihash.from_hex_string(hex_hash))
def _validate_asset_file_checksum(href, expected_multihash, asset_multihash):
expected_multihash = multihash.decode(from_hex_string(expected_multihash))
logger.debug(
'Validate asset file checksum at %s with multihash %s/%s (from headers), expected %s/%s '
'(from checksum:multishash attribute)', href,
to_hex_string(asset_multihash.digest), asset_multihash.name,
to_hex_string(expected_multihash.digest), expected_multihash.name)
if asset_multihash.name != expected_multihash.name:
logger.error(
'Asset at href %s, with multihash name=%s digest=%s, doesn\'t match the expected '
'multihash name=%s digest=%s defined in checksum:multihash attribute',
href, asset_multihash.name, to_hex_string(asset_multihash.digest),
expected_multihash.name, to_hex_string(expected_multihash.digest))
raise serializers.ValidationError({
'href':
_(f"Asset at href {href} has a {asset_multihash.name} multihash while a "
f"{expected_multihash.name} multihash is defined in the checksum:multihash "
"attribute")
})
if asset_multihash != expected_multihash:
logger.error(
'Asset at href %s, with multihash name=%s digest=%s, doesn\'t match the '
'checksum:multihash value name=%s digest=%s', href,
asset_multihash.name, to_hex_string(asset_multihash.digest),
expected_multihash.name, to_hex_string(expected_multihash.digest))
raise serializers.ValidationError({
'href':
_(f"Asset at href {href} with {asset_multihash.name} hash "
f"{to_hex_string(asset_multihash.digest)} doesn't match the "
f"checksum:multihash {to_hex_string(expected_multihash.digest)}")
})
def get_codec(chash):
"""
Extract the codec of a content hash
:param str hash: a hex string containing a content hash
:return: the extracted codec
:rtype: str
"""
buffer = multihash.from_hex_string(chash.lstrip('0x'))
return multicodec.get_codec(buffer)
def create_multihash(digest, hash_type):
'''Returns a multihash from a digest
Args:
digest: string
hash_type: string
hash type sha2-256
Returns: multihash
multihash
'''
return multihash.decode(multihash.encode(multihash.from_hex_string(digest), hash_type))
def encode(value):
"""
Encode Swarm.
:param bytes value: a decoded content
:return: the encoded content
:rtype: str
"""
mhash = multihash.encode(multihash.from_hex_string(value), 'keccak-256')
return make_cid(1, 'swarm-manifest', mhash).buffer
def ipfs_get_json(ipfs_conn: ipfsapi.client.Client,
file_hash: str,
tmpdir: Optional[PS] = None) -> Dict[str, Any]:
""" Perform an ipfs.get and return the json object as a Python dict """
if isinstance(file_hash, bytes):
file_hash = to_b58_string(
from_hex_string('1220' + remove_0x_prefix(file_hash.hex())))
elif is_0x_prefixed(file_hash):
file_hash = to_b58_string(
from_hex_string('1220' + remove_0x_prefix(file_hash)))
elif is_hex(file_hash):
file_hash = to_b58_string(from_hex_string('1220' + file_hash))
elif file_hash.startswith('Qm'):
pass
else:
raise ValueError("Invalid file_hash")
with tempfile.TemporaryDirectory(dir=tmpdir) as _workdir:
workdir = Path(_workdir)
orig_dir = Path.cwd()
assert orig_dir is not None
os.chdir(workdir)
ipfs_conn.get(file_hash)
downloaded: Path = workdir.joinpath(file_hash)
if not downloaded.exists() or not downloaded.is_file():
raise ScatterError("Download filed. File not found.")
contents = ''
with downloaded.open() as _userfile:
userfile_text = _userfile.read()
print("Downloaded... {}".format(userfile_text))
contents = json.loads(userfile_text)
os.chdir(orig_dir)
downloaded.unlink()
return contents
def parse_multihash(multihash_string):
'''Parse a multihash string
Args:
multihash_string: string
multihash string to parse
Returns.
Multihash object
Raises:
TypeError: if incoming data is not a string
ValueError: if the incoming data is not a valid multihash
'''
return multihash.decode(multihash.from_hex_string(multihash_string))
def decode(chash):
"""
Decode a content hash.
:param str hash: a hex string containing a content hash
:return: the decoded content
:rtype: str
"""
buffer = multihash.from_hex_string(chash.lstrip('0x'))
codec = multicodec.get_codec(buffer)
value = multicodec.remove_prefix(buffer)
profile = get_profile(codec)
return profile.decode(value)
def validate_asset_multihash(value):
'''Validate the Asset multihash field
The field value must be a multihash string
Args:
value: string
multihash value
Raises:
ValidationError in case of invalid multihash value
'''
try:
mhash = multihash.decode(multihash.from_hex_string(value))
except ValueError as error:
logger.error("Invalid multihash %s; %s", value, error)
raise ValidationError(code='checksum:multihash',
message=_('Invalid multihash value; %(error)s'),
params={'error': error})
def validate_checksum_multihash_sha256(value):
'''Validate the checksum multihash field
The field value must be a multihash sha256 string
Args:
value: string
multihash value
Raises:
ValidationError in case of invalid multihash value
'''
try:
mhash = multihash.decode(multihash.from_hex_string(value))
except (ValueError, TypeError) as error:
logger.error("Invalid multihash %s; %s", value, error)
raise ValidationError(_('Invalid multihash value; %(error)s'),
params={'error': error}, code='invalid') from None
if mhash.code != HASH_CODES['sha2-256']:
logger.error("Invalid multihash value: must be sha2-256 but is %s", CODE_HASHES[mhash.code])
raise ValidationError(_('Invalid multihash value: must be sha2-256 but is %(code)s'),
params={'code': CODE_HASHES[mhash.code]}, code='invalid')
def test_check_sum_sha256():
"""Test basic check_sum multihash generation."""
with TemporaryDirectory() as tmp:
tmp_file = Path(tmp) / 'file.txt'
message = 'Testing'
with open(tmp_file, 'w') as f:
f.write(message)
_hash = multihash_checksum_sha256(tmp_file)
expected_hash = '1220e806a291cfc3e61f83b98d344ee57e3e8933cccece4fb45e1481f1f560e70eb1'
assert _hash == expected_hash
# Try using stream instead file
stream = BytesIO(message.encode())
stream_hash = multihash_checksum_sha256(stream)
assert stream_hash == expected_hash
digest = multihash.from_hex_string(_hash)
# Ensure digest is a multihash
assert multihash.is_valid(digest)
def test_from_hex_string_invalid_type(self, value):
""" from_hex_string: raises TypeError for invalid types """
with pytest.raises(TypeError) as excinfo:
from_hex_string(value)
assert 'multihash should be str' in str(excinfo.value)
def test_from_digest_string_valid(self, value):
""" from_hex_string: decodes the correct values """
code = value['encoding']['code']
buffer = encode(bytes.fromhex(value['hex']), code)
assert from_hex_string(hexlify(buffer).decode()) == buffer
def test_valid_from_hex_string(self, valid):
for case in valid:
code = case['encoding']['code']
buf = multihash.encode(bytes.fromhex(case['hex']), code)
assert multihash.from_hex_string(hexlify(buf).decode()) == buf
