photon-os-advisories/generate.py

import sys
from glob import glob
import subprocess
import markdown
import json
import urllib.request
from datetime import datetime
import copy
import os
import re
from bs4 import BeautifulSoup

CVE_REGEX = r"CVE-\d{4}-\d{4,7}"
FILE_FORMAT = "/Security-Updates-{version}.md"
ADVISORY_URL = "https://github.com/vmware/photon/wiki/Security-Update-{slug}"
PHOTON_VERSIONS = range(1, 5)
ADVISORIES_DIR = "photon-wiki"


def last_modified_date(file):
    p = int(
        subprocess.check_output(
            ["git", "log", "--date=iso-strict", "-1", "--format=%ct", "--", file],
            cwd=ADVISORIES_DIR,
        )
        .decode("utf-8")
        .strip()
    )
    return datetime.utcfromtimestamp(p)


def created_date(file):
    with open(ADVISORIES_DIR + "/" + file) as f:
        for line in f:
            if line.startswith("Issue"):
                return datetime.strptime(line.split(": ")[1].strip(), "%Y-%m-%d")


def advisory_slug(os_version, advisory):
    _id = int(float(advisory.split("-")[2]))
    return f"{os_version}.0-{_id}"


def get_osv(cve_data_all_versions):
    for os_version in PHOTON_VERSIONS:
        filename = FILE_FORMAT.format(version=os_version)
        file = ADVISORIES_DIR + filename

        # Returns the version that fixed any of the given CVEs + OS + Package combination
        # there should only be one
        def cve_fixed_version(package, cves, os_version):
            # list of fixed versions with a matching
            # CVE/pkg/OS combination
            fixed_versions = set([
                x["res_ver"]
                for cve in cves
                for x in cve_data_all_versions[cve]
                if (x["os"] == os_version and x["pkg"] == package)
            ])
            # There should only be a single such reference
            # 
            if len(fixed_versions) != 1:
                print(f"Found multiple matching versions for {package}")
                print(fixed_versions)
                print(cves)
                return None
            return fixed_versions.pop()

        with open(file, "r") as f:
            table_html = markdown.markdown(
                f.read(), extensions=["markdown.extensions.tables"]
            )
            soup = BeautifulSoup(table_html, "html.parser")
            for tr in soup.find("tbody").find_all("tr"):
                (advisory, severity, published_date, packages, cves) = [
                    x.text for x in tr.find_all("td")
                ]
                packages = json.loads(packages.replace("'", '"'))
                cves = re.findall(CVE_REGEX, cves)
                slug = advisory_slug(os_version, advisory)
                advisory_file = f"Security-Update-{slug}.md"
                modified = last_modified_date(advisory_file)
                published = created_date(advisory_file)

                def affected(pkg, cves, os_version):
                    r = {
                        "package": {
                            "ecosystem": f"photon:{os_version}.0",
                            "name": pkg,
                            "purl": f"pkg:rpm/vmware/{pkg}?distro=photon-{os_version}",
                        }
                    }
                    fixed_version = cve_fixed_version(pkg, cves, os_version)
                    if fixed_version:
                        r["ranges"] = {
                            "events": [
                                {"introduced": "0"},
                                {"fixed": fixed_version},
                            ],
                            "type": "ECOSYSTEM"
                        }
                    return r

                yield {
                    "id": advisory,
                    "modified": modified.isoformat("T") + "Z",
                    "published": published.isoformat("T") + "Z",
                    "related": cves,
                    "affected": [
                        affected(pkg, cves, os_version)
                        for pkg in packages
                    ],
                    "references": [
                        {"type": "ADVISORY", "url": ADVISORY_URL.format(slug=slug)}
                    ],
                }


def merge_advisories(advisory_file, data):
    # read the current advisory data as json
    with open(advisory_file, "r") as f:
        original = json.load(f)
        current = copy.deepcopy(original)
    # merge the data
    assert current["id"] == data["id"]
    current["affected"].extend(data["affected"])
    current["references"].extend(data["references"])
    current["related"].extend(data["related"])

    # Make sure no CVE references are duplicated
    current["related"] = list(set(current["related"])).sort()

    # Pick the earlier published date
    # and the later modified date
    current["published"] = (
        min(
            datetime.strptime(current["published"], "%Y-%m-%dT%H:%M:%SZ"),
            datetime.strptime(data["published"], "%Y-%m-%dT%H:%M:%SZ"),
        ).isoformat("T")
        + "Z"
    )

    current["modified"] = (
        max(
            datetime.strptime(current["modified"], "%Y-%m-%dT%H:%M:%SZ"),
            datetime.strptime(data["modified"], "%Y-%m-%dT%H:%M:%SZ"),
        ).isoformat("T")
        + "Z"
    )

    no_important_changes = True
    # One of the important keys has changed
    for key in ["id", "affected", "references", "related", "published"]:
        if current[key] != original[key]:
            no_important_changes = False

    if no_important_changes:
        return None

    return current


def __main__():
    cve_data = {}
    for branch in PHOTON_VERSIONS:
        print(f"Fetching CVE Data for Photon OS {branch}.0")
        url = f"https://packages.vmware.com/photon/photon_cve_metadata/cve_data_photon{branch}.0.json"
        with urllib.request.urlopen(url) as r:
            data = json.loads(r.read().decode())
            for row in data:
                row["os"] = branch
                cve = row.pop("cve_id")
                if (
                    row["aff_ver"]
                    == f"all versions before {row['res_ver']} are vulnerable"
                ):
                    del row["aff_ver"]
                else:
                    print(row)
                    raise Exception("Unimplemented affected version range")
                if cve in cve_data:
                    cve_data[cve].append(row)
                else:
                    cve_data[cve] = [row]

    for advisory in glob("advisories/*.json"):
        os.remove(advisory)
    for d in get_osv(cve_data):
        fn = f"advisories/{d['id']}.json"
        if os.path.exists(fn):
            print(f"Updating {fn}")
            d = merge_advisories(fn, d)
        else:
            print(f"Creating {fn}")
        if d:
            with open(fn, "w") as f:
                f.write(json.dumps(d, indent=4, sort_keys=True))


if __name__ == "__main__":
    __main__()