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New API: add MetadataInfo class
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Add MetaMetaFileFile class to tuf.api.metadata module.
This class is be used for the "meta" field in Timestamp and
Snapshot metadata files described the specification.

Signed-off-by: Martin Vrachev <[email protected]>
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@MVrachev
MVrachev committed Dec 14, 2020
1 parent dde89c2 commit c8b5474
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Showing 2 changed files with 101 additions and 55 deletions.
28 changes: 15 additions & 13 deletions tests/test_api.py
View file
Original file line number Diff line number Diff line change
Expand Up @@ -33,6 +33,7 @@ def setUpModule():
import tuf.exceptions
from tuf.api.metadata import (
Metadata,
MetadataInfo,
Root,
Snapshot,
Timestamp,
Expand Down Expand Up @@ -224,17 +225,18 @@ def test_metadata_snapshot(self):
# Create a dict representing what we expect the updated data to be
fileinfo = copy.deepcopy(snapshot.signed.meta)
hashes = {'sha256': 'c2986576f5fdfd43944e2b19e775453b96748ec4fe2638a6d2f32f1310967095'}
fileinfo['role1.json']['version'] = 2
fileinfo['role1.json']['hashes'] = hashes
fileinfo['role1.json']['length'] = 123
fileinfo['role1.json'].version = 2
fileinfo['role1.json'].hashes = hashes
fileinfo['role1.json'].length = 123


self.assertNotEqual(snapshot.signed.meta, fileinfo)
snapshot.signed.update('role1', 2, 123, hashes)
self.assertEqual(snapshot.signed.meta, fileinfo)

# Update only version. Length and hashes are optional.
snapshot.signed.update('role1', 3)
fileinfo['role1.json'] = {'version': 3}
fileinfo['role1.json'] = MetadataInfo(3)
self.assertEqual(snapshot.signed.meta, fileinfo)


Expand Down Expand Up @@ -263,18 +265,18 @@ def test_metadata_timestamp(self):
self.assertEqual(timestamp.signed.expires, datetime(2036, 1, 3, 0, 0))

hashes = {'sha256': '0ae9664468150a9aa1e7f11feecb32341658eb84292851367fea2da88e8a58dc'}
fileinfo = copy.deepcopy(timestamp.signed.meta['snapshot.json'])
fileinfo['hashes'] = hashes
fileinfo['version'] = 2
fileinfo['length'] = 520

self.assertNotEqual(timestamp.signed.meta['snapshot.json'], fileinfo)
fileinfo = copy.deepcopy(timestamp.signed.meta)
fileinfo['snapshot.json'].hashes = hashes
fileinfo['snapshot.json'].version = 2
fileinfo['snapshot.json'].length = 520
self.assertNotEqual(timestamp.signed.meta, fileinfo)
timestamp.signed.update(2, 520, hashes)
self.assertEqual(timestamp.signed.meta['snapshot.json'], fileinfo)
self.assertEqual(timestamp.signed.meta, fileinfo)

# Update only version. Length and hashes are optional.
timestamp.signed.update(3)
fileinfo = {'version': 3}
self.assertEqual(timestamp.signed.meta['snapshot.json'], fileinfo)
fileinfo['snapshot.json'] = MetadataInfo(version=3)
self.assertEqual(timestamp.signed.meta, fileinfo)


def test_metadata_root(self):
Expand Down
128 changes: 86 additions & 42 deletions tuf/api/metadata.py
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Original file line number Diff line number Diff line change
Expand Up @@ -418,6 +418,50 @@ def remove_key(self, role: str, keyid: str) -> None:
del self.keys[keyid]


class MetadataInfo:
"""A container with information about a particular metadata file.
Instances of MetadataInfo are used as values in a dictionary called
"meta" in Timestamp and Snapshot.
Attributes:
version: An integer indicating the version of the metadata file.
length: An optional integer indicating the length of the metadata file.
hashes: A optional dictionary containing hash algorithms and the
hashes resulting from applying them over the metadata file.::
'hashes': {
'<HASH ALGO 1>': '<METADATA FILE HASH 1>',
'<HASH ALGO 2>': '<METADATA FILE HASH 2>',
...
}
"""

def __init__(self, version: int, length: Optional[int] = None,
hashes: Optional[JsonDict] = None) -> None:
self.version = version
self.length = length
self.hashes = hashes


def __eq__(self, other: 'MetadataInfo') -> bool:
"""Compare objects by their values instead of by their addresses."""
return (self.version == other.version and
self.length == other.length and
self.hashes == other.hashes)


def to_dict(self) -> JsonDict:
"""Returns the JSON-serializable dictionary representation of self. """
json_dict = {'version': self.version}

if self.length is not None:
json_dict['length'] = self.length

if self.hashes is not None:
json_dict['hashes'] = self.hashes

return json_dict


class Timestamp(Signed):
Expand All @@ -427,23 +471,14 @@ class Timestamp(Signed):
meta: A dictionary that contains information about snapshot metadata::
{
'snapshot.json': {
'version': <SNAPSHOT METADATA VERSION NUMBER>,
'length': <SNAPSHOT METADATA FILE SIZE>, // optional
'hashes': {
'<HASH ALGO 1>': '<SNAPSHOT METADATA FILE HASH 1>',
'<HASH ALGO 2>': '<SNAPSHOT METADATA FILE HASH 2>',
...
} // optional
}
'snapshot.json': <MetadataInfo INSTANCE>
}
"""
def __init__(
self, _type: str, version: int, spec_version: str,
expires: datetime, meta: JsonDict) -> None:
expires: datetime, meta: Dict[str, MetadataInfo]) -> None:
super().__init__(_type, version, spec_version, expires)
# TODO: Add class for meta
self.meta = meta


Expand All @@ -452,22 +487,31 @@ def to_dict(self) -> JsonDict:
"""Returns the JSON-serializable dictionary representation of self. """
json_dict = super().to_dict()
json_dict.update({
'meta': self.meta
'meta': {
'snapshot.json': self.meta['snapshot.json'].to_dict()
}
})
return json_dict


@classmethod
def from_dict(cls, signed_dict: JsonDict) -> 'Timestamp':
"""Creates Timestamp object from its JSON/dict representation. """

# signed_dict is passed by reference, make sure we are not changing it.
changed_signed = signed_dict.copy()
changed_signed['meta']['snapshot.json'] = MetadataInfo(
**signed_dict['meta']['snapshot.json'])

return super().from_dict(changed_signed)


# Modification.
def update(self, version: int, length: Optional[int] = None,
hashes: Optional[JsonDict] = None) -> None:
"""Assigns passed info about snapshot metadata to meta dict. """

self.meta['snapshot.json'] = {'version': version}
if length is not None:
self.meta['snapshot.json']['length'] = length

if hashes is not None:
self.meta['snapshot.json']['hashes'] = hashes
self.meta['snapshot.json'] = MetadataInfo(version, length, hashes)


class Snapshot(Signed):
Expand All @@ -477,38 +521,43 @@ class Snapshot(Signed):
meta: A dictionary that contains information about targets metadata::
{
'targets.json': {
'version': <TARGETS METADATA VERSION NUMBER>,
'length': <TARGETS METADATA FILE SIZE>, // optional
'hashes': {
'<HASH ALGO 1>': '<TARGETS METADATA FILE HASH 1>',
'<HASH ALGO 2>': '<TARGETS METADATA FILE HASH 2>',
...
} // optional
},
'<DELEGATED TARGETS ROLE 1>.json': {
...
},
'<DELEGATED TARGETS ROLE 2>.json': {
...
},
'targets.json': <MetadataInfo INSTANCE>,
'<DELEGATED TARGETS ROLE 1>.json': <MetadataInfo INSTANCE>,
'<DELEGATED TARGETS ROLE 2>.json': <MetadataInfo INSTANCE>,
...
}
"""
def __init__(
self, _type: str, version: int, spec_version: str,
expires: datetime, meta: JsonDict) -> None:
expires: datetime, meta: Dict[str, MetadataInfo]) -> None:
super().__init__(_type, version, spec_version, expires)
# TODO: Add class for meta
self.meta = meta


@classmethod
def from_dict(cls, signed_dict: JsonDict) -> 'Snapshot':
"""Creates Snapshot object from its JSON/dict representation. """

# signed_dict is passed by reference, make sure we are not changing it.
changed_signed = signed_dict.copy()
for meta_path in signed_dict['meta'].keys():
changed_signed['meta'][meta_path] = MetadataInfo(
**signed_dict['meta'][meta_path])

return super().from_dict(changed_signed)


# Serialization.
def to_dict(self) -> JsonDict:
"""Returns the JSON-serializable dictionary representation of self. """
json_dict = super().to_dict()
meta_dict = {}
for meta_path, meta_info in self.meta.items():
meta_dict[meta_path] = meta_info.to_dict()

json_dict.update({
'meta': self.meta
'meta': meta_dict
})
return json_dict

Expand All @@ -520,12 +569,7 @@ def update(
"""Assigns passed (delegated) targets role info to meta dict. """
metadata_fn = f'{rolename}.json'

self.meta[metadata_fn] = {'version': version}
if length is not None:
self.meta[metadata_fn]['length'] = length

if hashes is not None:
self.meta[metadata_fn]['hashes'] = hashes
self.meta[metadata_fn] = MetadataInfo(version, length, hashes)


class Targets(Signed):
Expand Down

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