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| 1 | +# Copyright 2023 The Sigstore Authors |
| 2 | +# |
| 3 | +# Licensed under the Apache License, Version 2.0 (the "License"); |
| 4 | +# you may not use this file except in compliance with the License. |
| 5 | +# You may obtain a copy of the License at |
| 6 | +# |
| 7 | +# http://www.apache.org/licenses/LICENSE-2.0 |
| 8 | +# |
| 9 | +# Unless required by applicable law or agreed to in writing, software |
| 10 | +# distributed under the License is distributed on an "AS IS" BASIS, |
| 11 | +# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
| 12 | +# See the License for the specific language governing permissions and |
| 13 | +# limitations under the License. |
| 14 | + |
| 15 | +""" |
| 16 | +Trust root management for sigstore-python. |
| 17 | +""" |
| 18 | + |
| 19 | +from __future__ import annotations |
| 20 | + |
| 21 | +from datetime import datetime, timezone |
| 22 | +from pathlib import Path |
| 23 | +from typing import Iterable |
| 24 | + |
| 25 | +from cryptography.x509 import Certificate, load_der_x509_certificate |
| 26 | +from sigstore_protobuf_specs.dev.sigstore.common.v1 import TimeRange |
| 27 | +from sigstore_protobuf_specs.dev.sigstore.trustroot.v1 import ( |
| 28 | + CertificateAuthority, |
| 29 | + TransparencyLogInstance, |
| 30 | +) |
| 31 | +from sigstore_protobuf_specs.dev.sigstore.trustroot.v1 import ( |
| 32 | + TrustedRoot as _TrustedRoot, |
| 33 | +) |
| 34 | + |
| 35 | +from sigstore._internal.tuf import DEFAULT_TUF_URL, STAGING_TUF_URL, TrustUpdater |
| 36 | +from sigstore.errors import MetadataError |
| 37 | + |
| 38 | + |
| 39 | +def _is_timerange_valid(period: TimeRange | None, *, allow_expired: bool) -> bool: |
| 40 | + """ |
| 41 | + Given a `period`, checks that the the current time is not before `start`. If |
| 42 | + `allow_expired` is `False`, also checks that the current time is not after |
| 43 | + `end`. |
| 44 | + """ |
| 45 | + now = datetime.now(timezone.utc) |
| 46 | + |
| 47 | + # If there was no validity period specified, the key is always valid. |
| 48 | + if not period: |
| 49 | + return True |
| 50 | + |
| 51 | + # Active: if the current time is before the starting period, we are not yet |
| 52 | + # valid. |
| 53 | + if now < period.start: |
| 54 | + return False |
| 55 | + |
| 56 | + # If we want Expired keys, the key is valid at this point. Otherwise, check |
| 57 | + # that we are within range. |
| 58 | + return allow_expired or (period.end is None or now <= period.end) |
| 59 | + |
| 60 | + |
| 61 | +class TrustedRoot(_TrustedRoot): |
| 62 | + """Complete set of trusted entities for a Sigstore client""" |
| 63 | + |
| 64 | + @classmethod |
| 65 | + def from_file(cls, path: str) -> "TrustedRoot": |
| 66 | + """Create a new trust root from file""" |
| 67 | + tr: TrustedRoot = cls().from_json(Path(path).read_bytes()) |
| 68 | + return tr |
| 69 | + |
| 70 | + @classmethod |
| 71 | + def from_tuf(cls, url: str, offline: bool = False) -> "TrustedRoot": |
| 72 | + """Create a new trust root from a TUF repository. |
| 73 | +
|
| 74 | + If `offline`, will use trust root in local TUF cache. Otherwise will |
| 75 | + update the trust root from remote TUF repository. |
| 76 | + """ |
| 77 | + path = TrustUpdater(url, offline).get_trusted_root_path() |
| 78 | + return cls.from_file(path) |
| 79 | + |
| 80 | + @classmethod |
| 81 | + def production(cls, offline: bool = False) -> "TrustedRoot": |
| 82 | + """Create new trust root from Sigstore production TUF repository. |
| 83 | +
|
| 84 | + If `offline`, will use trust root in local TUF cache. Otherwise will |
| 85 | + update the trust root from remote TUF repository. |
| 86 | + """ |
| 87 | + return cls.from_tuf(DEFAULT_TUF_URL, offline) |
| 88 | + |
| 89 | + @classmethod |
| 90 | + def staging(cls, offline: bool = False) -> "TrustedRoot": |
| 91 | + """Create new trust root from Sigstore staging TUF repository. |
| 92 | +
|
| 93 | + If `offline`, will use trust root in local TUF cache. Otherwise will |
| 94 | + update the trust root from remote TUF repository. |
| 95 | + """ |
| 96 | + return cls.from_tuf(STAGING_TUF_URL, offline) |
| 97 | + |
| 98 | + @staticmethod |
| 99 | + def _get_tlog_keys(tlogs: list[TransparencyLogInstance]) -> Iterable[bytes]: |
| 100 | + """Return public key contents given transparency log instances.""" |
| 101 | + |
| 102 | + for key in tlogs: |
| 103 | + if not _is_timerange_valid(key.public_key.valid_for, allow_expired=False): |
| 104 | + continue |
| 105 | + key_bytes = key.public_key.raw_bytes |
| 106 | + if key_bytes: |
| 107 | + yield key_bytes |
| 108 | + |
| 109 | + @staticmethod |
| 110 | + def _get_ca_keys( |
| 111 | + cas: list[CertificateAuthority], *, allow_expired: bool |
| 112 | + ) -> Iterable[bytes]: |
| 113 | + """Return public key contents given certificate authorities.""" |
| 114 | + |
| 115 | + for ca in cas: |
| 116 | + if not _is_timerange_valid(ca.valid_for, allow_expired=allow_expired): |
| 117 | + continue |
| 118 | + for cert in ca.cert_chain.certificates: |
| 119 | + yield cert.raw_bytes |
| 120 | + |
| 121 | + def get_ctfe_keys(self) -> list[bytes]: |
| 122 | + """Return the active CTFE public keys contents.""" |
| 123 | + ctfes: list[bytes] = list(self._get_tlog_keys(self.ctlogs)) |
| 124 | + if not ctfes: |
| 125 | + raise MetadataError("Active CTFE keys not found in trusted root") |
| 126 | + return ctfes |
| 127 | + |
| 128 | + def get_rekor_keys(self) -> list[bytes]: |
| 129 | + """Return the rekor public key content.""" |
| 130 | + keys: list[bytes] = list(self._get_tlog_keys(self.tlogs)) |
| 131 | + |
| 132 | + if len(keys) != 1: |
| 133 | + raise MetadataError("Did not find one active Rekor key in trusted root") |
| 134 | + return keys |
| 135 | + |
| 136 | + def get_fulcio_certs(self) -> list[Certificate]: |
| 137 | + """Return the Fulcio certificates.""" |
| 138 | + |
| 139 | + certs: list[Certificate] |
| 140 | + |
| 141 | + # Return expired certificates too: they are expired now but may have |
| 142 | + # been active when the certificate was used to sign. |
| 143 | + certs = [ |
| 144 | + load_der_x509_certificate(c) |
| 145 | + for c in self._get_ca_keys(self.certificate_authorities, allow_expired=True) |
| 146 | + ] |
| 147 | + |
| 148 | + if not certs: |
| 149 | + raise MetadataError("Fulcio certificates not found in trusted root") |
| 150 | + return certs |
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