tests/utils.py

# This file is dual licensed under the terms of the Apache License, Version
# 2.0, and the BSD License. See the LICENSE file in the root of this repository
# for complete details.

from __future__ import absolute_import, division, print_function

import binascii
import collections
import json
import math
import os
import re
from contextlib import contextmanager

import pytest

import six

from cryptography.exceptions import UnsupportedAlgorithm

import cryptography_vectors


HashVector = collections.namedtuple("HashVector", ["message", "digest"])
KeyedHashVector = collections.namedtuple(
    "KeyedHashVector", ["message", "digest", "key"]
)


def check_backend_support(backend, item):
    for mark in item.node.iter_markers("supported"):
        if not mark.kwargs["only_if"](backend):
            pytest.skip("{0} ({1})".format(
                mark.kwargs["skip_message"], backend
            ))


@contextmanager
def raises_unsupported_algorithm(reason):
    with pytest.raises(UnsupportedAlgorithm) as exc_info:
        yield exc_info

    assert exc_info.value._reason is reason


def load_vectors_from_file(filename, loader, mode="r"):
    with cryptography_vectors.open_vector_file(filename, mode) as vector_file:
        return loader(vector_file)


def load_nist_vectors(vector_data):
    test_data = None
    data = []

    for line in vector_data:
        line = line.strip()

        # Blank lines, comments, and section headers are ignored
        if not line or line.startswith("#") or (line.startswith("[") and
                                                line.endswith("]")):
            continue

        if line.strip() == "FAIL":
            test_data["fail"] = True
            continue

        # Build our data using a simple Key = Value format
        name, value = [c.strip() for c in line.split("=")]

        # Some tests (PBKDF2) contain \0, which should be interpreted as a
        # null character rather than literal.
        value = value.replace("\\0", "\0")

        # COUNT is a special token that indicates a new block of data
        if name.upper() == "COUNT":
            test_data = {}
            data.append(test_data)
            continue
        # For all other tokens we simply want the name, value stored in
        # the dictionary
        else:
            test_data[name.lower()] = value.encode("ascii")

    return data


def load_cryptrec_vectors(vector_data):
    cryptrec_list = []

    for line in vector_data:
        line = line.strip()

        # Blank lines and comments are ignored
        if not line or line.startswith("#"):
            continue

        if line.startswith("K"):
            key = line.split(" : ")[1].replace(" ", "").encode("ascii")
        elif line.startswith("P"):
            pt = line.split(" : ")[1].replace(" ", "").encode("ascii")
        elif line.startswith("C"):
            ct = line.split(" : ")[1].replace(" ", "").encode("ascii")
            # after a C is found the K+P+C tuple is complete
            # there are many P+C pairs for each K
            cryptrec_list.append({
                "key": key,
                "plaintext": pt,
                "ciphertext": ct
            })
        else:
            raise ValueError("Invalid line in file '{}'".format(line))
    return cryptrec_list


def load_hash_vectors(vector_data):
    vectors = []
    key = None
    msg = None
    md = None

    for line in vector_data:
        line = line.strip()

        if not line or line.startswith("#") or line.startswith("["):
            continue

        if line.startswith("Len"):
            length = int(line.split(" = ")[1])
        elif line.startswith("Key"):
            # HMAC vectors contain a key attribute. Hash vectors do not.
            key = line.split(" = ")[1].encode("ascii")
        elif line.startswith("Msg"):
            # In the NIST vectors they have chosen to represent an empty
            # string as hex 00, which is of course not actually an empty
            # string. So we parse the provided length and catch this edge case.
            msg = line.split(" = ")[1].encode("ascii") if length > 0 else b""
        elif line.startswith("MD"):
            md = line.split(" = ")[1]
            # after MD is found the Msg+MD (+ potential key) tuple is complete
            if key is not None:
                vectors.append(KeyedHashVector(msg, md, key))
                key = None
                msg = None
                md = None
            else:
                vectors.append(HashVector(msg, md))
                msg = None
                md = None
        else:
            raise ValueError("Unknown line in hash vector")
    return vectors


def load_pkcs1_vectors(vector_data):
    """
    Loads data out of RSA PKCS #1 vector files.
    """
    private_key_vector = None
    public_key_vector = None
    attr = None
    key = None
    example_vector = None
    examples = []
    vectors = []
    for line in vector_data:
        if (
            line.startswith("# PSS Example") or
            line.startswith("# OAEP Example") or
            line.startswith("# PKCS#1 v1.5")
        ):
            if example_vector:
                for key, value in six.iteritems(example_vector):
                    hex_str = "".join(value).replace(" ", "").encode("ascii")
                    example_vector[key] = hex_str
                examples.append(example_vector)

            attr = None
            example_vector = collections.defaultdict(list)

        if line.startswith("# Message"):
            attr = "message"
            continue
        elif line.startswith("# Salt"):
            attr = "salt"
            continue
        elif line.startswith("# Seed"):
            attr = "seed"
            continue
        elif line.startswith("# Signature"):
            attr = "signature"
            continue
        elif line.startswith("# Encryption"):
            attr = "encryption"
            continue
        elif (
            example_vector and
            line.startswith("# =============================================")
        ):
            for key, value in six.iteritems(example_vector):
                hex_str = "".join(value).replace(" ", "").encode("ascii")
                example_vector[key] = hex_str
            examples.append(example_vector)
            example_vector = None
            attr = None
        elif example_vector and line.startswith("#"):
            continue
        else:
            if attr is not None and example_vector is not None:
                example_vector[attr].append(line.strip())
                continue

        if (
            line.startswith("# Example") or
            line.startswith("# =============================================")
        ):
            if key:
                assert private_key_vector
                assert public_key_vector

                for key, value in six.iteritems(public_key_vector):
                    hex_str = "".join(value).replace(" ", "")
                    public_key_vector[key] = int(hex_str, 16)

                for key, value in six.iteritems(private_key_vector):
                    hex_str = "".join(value).replace(" ", "")
                    private_key_vector[key] = int(hex_str, 16)

                private_key_vector["examples"] = examples
                examples = []

                assert (
                    private_key_vector['public_exponent'] ==
                    public_key_vector['public_exponent']
                )

                assert (
                    private_key_vector['modulus'] ==
                    public_key_vector['modulus']
                )

                vectors.append(
                    (private_key_vector, public_key_vector)
                )

            public_key_vector = collections.defaultdict(list)
            private_key_vector = collections.defaultdict(list)
            key = None
            attr = None

        if private_key_vector is None or public_key_vector is None:
            # Random garbage to defeat CPython's peephole optimizer so that
            # coverage records correctly: https://bugs.python.org/issue2506
            1 + 1
            continue

        if line.startswith("# Private key"):
            key = private_key_vector
        elif line.startswith("# Public key"):
            key = public_key_vector
        elif line.startswith("# Modulus:"):
            attr = "modulus"
        elif line.startswith("# Public exponent:"):
            attr = "public_exponent"
        elif line.startswith("# Exponent:"):
            if key is public_key_vector:
                attr = "public_exponent"
            else:
                assert key is private_key_vector
                attr = "private_exponent"
        elif line.startswith("# Prime 1:"):
            attr = "p"
        elif line.startswith("# Prime 2:"):
            attr = "q"
        elif line.startswith("# Prime exponent 1:"):
            attr = "dmp1"
        elif line.startswith("# Prime exponent 2:"):
            attr = "dmq1"
        elif line.startswith("# Coefficient:"):
            attr = "iqmp"
        elif line.startswith("#"):
            attr = None
        else:
            if key is not None and attr is not None:
                key[attr].append(line.strip())
    return vectors


def load_rsa_nist_vectors(vector_data):
    test_data = None
    p = None
    salt_length = None
    data = []

    for line in vector_data:
        line = line.strip()

        # Blank lines and section headers are ignored
        if not line or line.startswith("["):
            continue

        if line.startswith("# Salt len:"):
            salt_length = int(line.split(":")[1].strip())
            continue
        elif line.startswith("#"):
            continue

        # Build our data using a simple Key = Value format
        name, value = [c.strip() for c in line.split("=")]

        if name == "n":
            n = int(value, 16)
        elif name == "e" and p is None:
            e = int(value, 16)
        elif name == "p":
            p = int(value, 16)
        elif name == "q":
            q = int(value, 16)
        elif name == "SHAAlg":
            if p is None:
                test_data = {
                    "modulus": n,
                    "public_exponent": e,
                    "salt_length": salt_length,
                    "algorithm": value,
                    "fail": False
                }
            else:
                test_data = {
                    "modulus": n,
                    "p": p,
                    "q": q,
                    "algorithm": value
                }
                if salt_length is not None:
                    test_data["salt_length"] = salt_length
            data.append(test_data)
        elif name == "e" and p is not None:
            test_data["public_exponent"] = int(value, 16)
        elif name == "d":
            test_data["private_exponent"] = int(value, 16)
        elif name == "Result":
            test_data["fail"] = value.startswith("F")
        # For all other tokens we simply want the name, value stored in
        # the dictionary
        else:
            test_data[name.lower()] = value.encode("ascii")

    return data


def load_fips_dsa_key_pair_vectors(vector_data):
    """
    Loads data out of the FIPS DSA KeyPair vector files.
    """
    vectors = []
    for line in vector_data:
        line = line.strip()

        if not line or line.startswith("#") or line.startswith("[mod"):
            continue

        if line.startswith("P"):
            vectors.append({'p': int(line.split("=")[1], 16)})
        elif line.startswith("Q"):
            vectors[-1]['q'] = int(line.split("=")[1], 16)
        elif line.startswith("G"):
            vectors[-1]['g'] = int(line.split("=")[1], 16)
        elif line.startswith("X") and 'x' not in vectors[-1]:
            vectors[-1]['x'] = int(line.split("=")[1], 16)
        elif line.startswith("X") and 'x' in vectors[-1]:
            vectors.append({'p': vectors[-1]['p'],
                            'q': vectors[-1]['q'],
                            'g': vectors[-1]['g'],
                            'x': int(line.split("=")[1], 16)
                            })
        elif line.startswith("Y"):
            vectors[-1]['y'] = int(line.split("=")[1], 16)

    return vectors


def load_fips_dsa_sig_vectors(vector_data):
    """
    Loads data out of the FIPS DSA SigVer vector files.
    """
    vectors = []
    sha_regex = re.compile(
        r"\[mod = L=...., N=..., SHA-(?P<sha>1|224|256|384|512)\]"
    )

    for line in vector_data:
        line = line.strip()

        if not line or line.startswith("#"):
            continue

        sha_match = sha_regex.match(line)
        if sha_match:
            digest_algorithm = "SHA-{0}".format(sha_match.group("sha"))

        if line.startswith("[mod"):
            continue

        name, value = [c.strip() for c in line.split("=")]

        if name == "P":
            vectors.append({'p': int(value, 16),
                            'digest_algorithm': digest_algorithm})
        elif name == "Q":
            vectors[-1]['q'] = int(value, 16)
        elif name == "G":
            vectors[-1]['g'] = int(value, 16)
        elif name == "Msg" and 'msg' not in vectors[-1]:
            hexmsg = value.strip().encode("ascii")
            vectors[-1]['msg'] = binascii.unhexlify(hexmsg)
        elif name == "Msg" and 'msg' in vectors[-1]:
            hexmsg = value.strip().encode("ascii")
            vectors.append({'p': vectors[-1]['p'],
                            'q': vectors[-1]['q'],
                            'g': vectors[-1]['g'],
                            'digest_algorithm':
                            vectors[-1]['digest_algorithm'],
                            'msg': binascii.unhexlify(hexmsg)})
        elif name == "X":
            vectors[-1]['x'] = int(value, 16)
        elif name == "Y":
            vectors[-1]['y'] = int(value, 16)
        elif name == "R":
            vectors[-1]['r'] = int(value, 16)
        elif name == "S":
            vectors[-1]['s'] = int(value, 16)
        elif name == "Result":
            vectors[-1]['result'] = value.split("(")[0].strip()

    return vectors


# http://tools.ietf.org/html/rfc4492#appendix-A
_ECDSA_CURVE_NAMES = {
    "P-192": "secp192r1",
    "P-224": "secp224r1",
    "P-256": "secp256r1",
    "P-384": "secp384r1",
    "P-521": "secp521r1",

    "K-163": "sect163k1",
    "K-233": "sect233k1",
    "K-256": "secp256k1",
    "K-283": "sect283k1",
    "K-409": "sect409k1",
    "K-571": "sect571k1",

    "B-163": "sect163r2",
    "B-233": "sect233r1",
    "B-283": "sect283r1",
    "B-409": "sect409r1",
    "B-571": "sect571r1",
}


def load_fips_ecdsa_key_pair_vectors(vector_data):
    """
    Loads data out of the FIPS ECDSA KeyPair vector files.
    """
    vectors = []
    key_data = None
    for line in vector_data:
        line = line.strip()

        if not line or line.startswith("#"):
            continue

        if line[1:-1] in _ECDSA_CURVE_NAMES:
            curve_name = _ECDSA_CURVE_NAMES[line[1:-1]]

        elif line.startswith("d = "):
            if key_data is not None:
                vectors.append(key_data)

            key_data = {
                "curve": curve_name,
                "d": int(line.split("=")[1], 16)
            }

        elif key_data is not None:
            if line.startswith("Qx = "):
                key_data["x"] = int(line.split("=")[1], 16)
            elif line.startswith("Qy = "):
                key_data["y"] = int(line.split("=")[1], 16)

    assert key_data is not None
    vectors.append(key_data)

    return vectors


def load_fips_ecdsa_signing_vectors(vector_data):
    """
    Loads data out of the FIPS ECDSA SigGen vector files.
    """
    vectors = []

    curve_rx = re.compile(
        r"\[(?P<curve>[PKB]-[0-9]{3}),SHA-(?P<sha>1|224|256|384|512)\]"
    )

    data = None
    for line in vector_data:
        line = line.strip()

        curve_match = curve_rx.match(line)
        if curve_match:
            curve_name = _ECDSA_CURVE_NAMES[curve_match.group("curve")]
            digest_name = "SHA-{0}".format(curve_match.group("sha"))

        elif line.startswith("Msg = "):
            if data is not None:
                vectors.append(data)

            hexmsg = line.split("=")[1].strip().encode("ascii")

            data = {
                "curve": curve_name,
                "digest_algorithm": digest_name,
                "message": binascii.unhexlify(hexmsg)
            }

        elif data is not None:
            if line.startswith("Qx = "):
                data["x"] = int(line.split("=")[1], 16)
            elif line.startswith("Qy = "):
                data["y"] = int(line.split("=")[1], 16)
            elif line.startswith("R = "):
                data["r"] = int(line.split("=")[1], 16)
            elif line.startswith("S = "):
                data["s"] = int(line.split("=")[1], 16)
            elif line.startswith("d = "):
                data["d"] = int(line.split("=")[1], 16)
            elif line.startswith("Result = "):
                data["fail"] = line.split("=")[1].strip()[0] == "F"

    assert data is not None
    vectors.append(data)
    return vectors


def load_kasvs_dh_vectors(vector_data):
    """
    Loads data out of the KASVS key exchange vector data
    """

    result_rx = re.compile(r"([FP]) \(([0-9]+) -")

    vectors = []
    data = {
        "fail_z": False,
        "fail_agree": False
    }

    for line in vector_data:
        line = line.strip()

        if not line or line.startswith("#"):
            continue

        if line.startswith("P = "):
            data["p"] = int(line.split("=")[1], 16)
        elif line.startswith("Q = "):
            data["q"] = int(line.split("=")[1], 16)
        elif line.startswith("G = "):
            data["g"] = int(line.split("=")[1], 16)
        elif line.startswith("Z = "):
            z_hex = line.split("=")[1].strip().encode("ascii")
            data["z"] = binascii.unhexlify(z_hex)
        elif line.startswith("XstatCAVS = "):
            data["x1"] = int(line.split("=")[1], 16)
        elif line.startswith("YstatCAVS = "):
            data["y1"] = int(line.split("=")[1], 16)
        elif line.startswith("XstatIUT = "):
            data["x2"] = int(line.split("=")[1], 16)
        elif line.startswith("YstatIUT = "):
            data["y2"] = int(line.split("=")[1], 16)
        elif line.startswith("Result = "):
            result_str = line.split("=")[1].strip()
            match = result_rx.match(result_str)

            if match.group(1) == "F":
                if int(match.group(2)) in (5, 10):
                    data["fail_z"] = True
                else:
                    data["fail_agree"] = True

            vectors.append(data)

            data = {
                "p": data["p"],
                "q": data["q"],
                "g": data["g"],
                "fail_z": False,
                "fail_agree": False
            }

    return vectors


def load_kasvs_ecdh_vectors(vector_data):
    """
    Loads data out of the KASVS key exchange vector data
    """

    curve_name_map = {
        "P-192": "secp192r1",
        "P-224": "secp224r1",
        "P-256": "secp256r1",
        "P-384": "secp384r1",
        "P-521": "secp521r1",
    }

    result_rx = re.compile(r"([FP]) \(([0-9]+) -")

    tags = []
    sets = {}
    vectors = []

    # find info in header
    for line in vector_data:
        line = line.strip()

        if line.startswith("#"):
            parm = line.split("Parameter set(s) supported:")
            if len(parm) == 2:
                names = parm[1].strip().split()
                for n in names:
                    tags.append("[%s]" % n)
                break

    # Sets Metadata
    tag = None
    curve = None
    for line in vector_data:
        line = line.strip()

        if not line or line.startswith("#"):
            continue

        if line in tags:
            tag = line
            curve = None
        elif line.startswith("[Curve selected:"):
            curve = curve_name_map[line.split(':')[1].strip()[:-1]]

        if tag is not None and curve is not None:
            sets[tag.strip("[]")] = curve
            tag = None
        if len(tags) == len(sets):
            break

    # Data
    data = {
        "CAVS": {},
        "IUT": {},
    }
    tag = None
    for line in vector_data:
        line = line.strip()

        if not line or line.startswith("#"):
            continue

        if line.startswith("["):
            tag = line.split()[0][1:]
        elif line.startswith("COUNT = "):
            data["COUNT"] = int(line.split("=")[1])
        elif line.startswith("dsCAVS = "):
            data["CAVS"]["d"] = int(line.split("=")[1], 16)
        elif line.startswith("QsCAVSx = "):
            data["CAVS"]["x"] = int(line.split("=")[1], 16)
        elif line.startswith("QsCAVSy = "):
            data["CAVS"]["y"] = int(line.split("=")[1], 16)
        elif line.startswith("dsIUT = "):
            data["IUT"]["d"] = int(line.split("=")[1], 16)
        elif line.startswith("QsIUTx = "):
            data["IUT"]["x"] = int(line.split("=")[1], 16)
        elif line.startswith("QsIUTy = "):
            data["IUT"]["y"] = int(line.split("=")[1], 16)
        elif line.startswith("OI = "):
            data["OI"] = int(line.split("=")[1], 16)
        elif line.startswith("Z = "):
            data["Z"] = int(line.split("=")[1], 16)
        elif line.startswith("DKM = "):
            data["DKM"] = int(line.split("=")[1], 16)
        elif line.startswith("Result = "):
            result_str = line.split("=")[1].strip()
            match = result_rx.match(result_str)

            if match.group(1) == "F":
                data["fail"] = True
            else:
                data["fail"] = False
            data["errno"] = int(match.group(2))

            data["curve"] = sets[tag]

            vectors.append(data)

            data = {
                "CAVS": {},
                "IUT": {},
            }

    return vectors


def load_x963_vectors(vector_data):
    """
    Loads data out of the X9.63 vector data
    """

    vectors = []

    # Sets Metadata
    hashname = None
    vector = {}
    for line in vector_data:
        line = line.strip()

        if line.startswith("[SHA"):
            hashname = line[1:-1]
            shared_secret_len = 0
            shared_info_len = 0
            key_data_len = 0
        elif line.startswith("[shared secret length"):
            shared_secret_len = int(line[1:-1].split("=")[1].strip())
        elif line.startswith("[SharedInfo length"):
            shared_info_len = int(line[1:-1].split("=")[1].strip())
        elif line.startswith("[key data length"):
            key_data_len = int(line[1:-1].split("=")[1].strip())
        elif line.startswith("COUNT"):
            count = int(line.split("=")[1].strip())
            vector["hash"] = hashname
            vector["count"] = count
            vector["shared_secret_length"] = shared_secret_len
            vector["sharedinfo_length"] = shared_info_len
            vector["key_data_length"] = key_data_len
        elif line.startswith("Z"):
            vector["Z"] = line.split("=")[1].strip()
            assert math.ceil(shared_secret_len / 8) * 2 == len(vector["Z"])
        elif line.startswith("SharedInfo"):
            if shared_info_len != 0:
                vector["sharedinfo"] = line.split("=")[1].strip()
                silen = len(vector["sharedinfo"])
                assert math.ceil(shared_info_len / 8) * 2 == silen
        elif line.startswith("key_data"):
            vector["key_data"] = line.split("=")[1].strip()
            assert math.ceil(key_data_len / 8) * 2 == len(vector["key_data"])
            vectors.append(vector)
            vector = {}

    return vectors


def load_nist_kbkdf_vectors(vector_data):
    """
    Load NIST SP 800-108 KDF Vectors
    """
    vectors = []
    test_data = None
    tag = {}

    for line in vector_data:
        line = line.strip()

        if not line or line.startswith("#"):
            continue

        if line.startswith("[") and line.endswith("]"):
            tag_data = line[1:-1]
            name, value = [c.strip() for c in tag_data.split("=")]
            if value.endswith('_BITS'):
                value = int(value.split('_')[0])
                tag.update({name.lower(): value})
                continue

            tag.update({name.lower(): value.lower()})
        elif line.startswith("COUNT="):
            test_data = dict()
            test_data.update(tag)
            vectors.append(test_data)
        elif line.startswith("L"):
            name, value = [c.strip() for c in line.split("=")]
            test_data[name.lower()] = int(value)
        else:
            name, value = [c.strip() for c in line.split("=")]
            test_data[name.lower()] = value.encode("ascii")

    return vectors


def load_ed25519_vectors(vector_data):
    data = []
    for line in vector_data:
        secret_key, public_key, message, signature, _ = line.split(':')
        # In the vectors the first element is secret key + public key
        secret_key = secret_key[0:64]
        # In the vectors the signature section is signature + message
        signature = signature[0:128]
        data.append({
            "secret_key": secret_key,
            "public_key": public_key,
            "message": message,
            "signature": signature
        })
    return data


def load_nist_ccm_vectors(vector_data):
    test_data = None
    section_data = None
    global_data = {}
    new_section = False
    data = []

    for line in vector_data:
        line = line.strip()

        # Blank lines and comments should be ignored
        if not line or line.startswith("#"):
            continue

        # Some of the CCM vectors have global values for this. They are always
        # at the top before the first section header (see: VADT, VNT, VPT)
        if line.startswith(("Alen", "Plen", "Nlen", "Tlen")):
            name, value = [c.strip() for c in line.split("=")]
            global_data[name.lower()] = int(value)
            continue

        # section headers contain length data we might care about
        if line.startswith("["):
            new_section = True
            section_data = {}
            section = line[1:-1]
            items = [c.strip() for c in section.split(",")]
            for item in items:
                name, value = [c.strip() for c in item.split("=")]
                section_data[name.lower()] = int(value)
            continue

        name, value = [c.strip() for c in line.split("=")]

        if name.lower() in ("key", "nonce") and new_section:
            section_data[name.lower()] = value.encode("ascii")
            continue

        new_section = False

        # Payload is sometimes special because these vectors are absurd. Each
        # example may or may not have a payload. If it does not then the
        # previous example's payload should be used. We accomplish this by
        # writing it into the section_data. Because we update each example
        # with the section data it will be overwritten if a new payload value
        # is present. NIST should be ashamed of their vector creation.
        if name.lower() == "payload":
            section_data[name.lower()] = value.encode("ascii")

        # Result is a special token telling us if the test should pass/fail.
        # This is only present in the DVPT CCM tests
        if name.lower() == "result":
            if value.lower() == "pass":
                test_data["fail"] = False
            else:
                test_data["fail"] = True
            continue

        # COUNT is a special token that indicates a new block of data
        if name.lower() == "count":
            test_data = {}
            test_data.update(global_data)
            test_data.update(section_data)
            data.append(test_data)
            continue
        # For all other tokens we simply want the name, value stored in
        # the dictionary
        else:
            test_data[name.lower()] = value.encode("ascii")

    return data


class WycheproofTest(object):
    def __init__(self, testgroup, testcase):
        self.testgroup = testgroup
        self.testcase = testcase

    def __repr__(self):
        return "<WycheproofTest({!r}, {!r}, tcId={})>".format(
            self.testgroup, self.testcase, self.testcase["tcId"],
        )

    @property
    def valid(self):
        return self.testcase["result"] == "valid"

    @property
    def acceptable(self):
        return self.testcase["result"] == "acceptable"

    @property
    def invalid(self):
        return self.testcase["result"] == "invalid"

    def has_flag(self, flag):
        return flag in self.testcase["flags"]


def skip_if_wycheproof_none(wycheproof):
    # This is factored into its own function so we can easily test both
    # branches
    if wycheproof is None:
        pytest.skip("--wycheproof-root not provided")


def load_wycheproof_tests(wycheproof, test_file):
    path = os.path.join(wycheproof, "testvectors", test_file)
    with open(path) as f:
        data = json.load(f)
        for group in data["testGroups"]:
            cases = group.pop("tests")
            for c in cases:
                yield WycheproofTest(group, c)