Rewriting URL request function to satisfy GitHub CodeQL server side request forgery (SSRF) warning

I'm working on a function that returns a HTTP response from https://pypi.org/simple/ when Python's pip installer requests it for a package. When pushing my code onto GitHub, the CodeQL checks warn of the risk of server side request forgery (SSRF), and asks me to create validation checks for the "user-defined input" (which is pip, in this case).

I have already made many attempts at validating the URL to satisfy this SSRF warning, but GitHub CodeQL has not accepted any of them so far. How can I rewrite the following to satisfy GitHub CodeQL's requirements for guarding against SSRF?

The relevant block of code:

import requests
from fastapi import APIRouter, Response

pypi = APIRouter(prefix="/pypi", tags=["bootstrap"])

@pypi.get("/{package}/", response_class=Response)
def get_pypi_package_downloads_list(package: str) -> Response:
    """
    Obtain list of all package downloads from PyPI via the simple API (PEP 503).
    """
    url = f"https://pypi.org/simple/{package}"
    full_path_response = requests.get(url)

The following is a non-exhaustive overview of attempts I've tried in order to satisfy that SSRF warning. However, none of them have worked for me.

# Attempt 1
# Check that it's a PyPI URL
url = f"https://pypi.org/simple/{package}"
if "pypi" in url:
    full_path_response = requests.get(url)
else:
    raise ValueError("This is not a valid package")


# Attempt 2
# Validate that package name is alphanumeric (allow _ and -)
if package.replace("_", "").replace("-", "").isalnum():  
    url = f"https://pypi.org/simple/{package}"
    full_path_response = requests.get(url)
else:
    raise ValueError("This is not a valid package")


# Attempt 3
# Check that it's a valid connection
with requests.get("https://pypi.org/simple/{package}") as http_response:
    if http_response.status_code == 200:
        full_path_response = http_response
    else:
        raise ValueError("This is not a valid package")


# Attempt 4
# Tried using RegEx matching to validate package name
if re.match(r"^[a-z0-9\_\-]+$", package):
    full_path_response = requests.get(f"https://pypi.org/simple/{package}")
else:
    raise ValueError("This is not a valid package")


# Attempt 5
# Use urllib.parse.urlparse to parse and validate the url
def validate_url(url: str) -> bool:
    parsed_url = urlparse(url)
    if parsed_url.scheme == "https" and parsed_url.hostname == "pypi.org":
        return True
    else:
        return False

def validate_package(package: str) -> bool:
    if package.replace("_", "").replace("-", "").isalnum():
        return True
    else:
        return False

# Validate package and URL
if validate_package(package) and validate_url(f"https://pypi.org/simple/{package}"):
    full_path_response = requests.get(
        f"https://pypi.org/simple/{package}"
    )  # Get response from PyPI
else:
    raise ValueError("This is not a valid package")


# Attempt 6
# Using a Pydantic model
from pydantic import BaseModel, HttpUrl, ValidationError

class UrlValidator(BaseModel):
    url: HttpUrl

def validate(url: str):
    try:
        UrlValidator(url=url)
    except ValidationError:
        log.error(f"{url} was not a valid URL")
        return False
    else:
        log.info(f"{url} was a valid URL")
        return True

# Attempt at URL validation to satisfy GitHub CodeQL requirements
url = f"https://pypi.org/simple/{package}"
if validate(url):
    full_path_response = requests.get(url)


# Attempt 7
# Encoding string before injection
from urllib.parse import quote_plus

def _validate_package_name(package: str) -> bool:
    # Check that it only contains alphanumerics, "_", or "-", and isn't excessively long
    if re.match(r"^[a-z0-9\-\_]+$", package):
        return True
    else:
        return False

def _get_full_path_response(package: str) -> requests.Response:
    # Sanitise string
    package_clean = quote_plus(package)
    print(f"Cleaned package: {package_clean}")

    # Validation checks
    if _validate_package_name(package_clean):
        url = f"https://pypi.org/simple/{package_clean}"
        print(f"URL: {url}")
        return requests.get(url)
    else:
        raise ValueError(f"{package_clean} is not a valid package name")
full_path_response = _get_full_path_response(package)


# Attempt 8
# The nuclear option of maintaining a list of approved packages
approved_packages: list = [pkg.lower() for pkg in approved_packages]  # List of package names from running `conda env list`

# Validate package and URL
if package.lower() in approved_packages:
    url = f"https://pypi.org/simple/{package}"
    full_path_response = requests.get(url)
else:
    raise ValueError(f"{package} is not a valid package name")

Thanks!

Solution

It turns out that this was a false positive due to the py/partial-ssrf check being incorrectly written. This issue has recently been reported as resolved, and the fix will be implemented in GitHub CodeQL v2.18.0.

From the dialogue, partial-SSRF can be guarded against as follows:

At that point, validating your input using mechanisms like isalnum() (as stated in the query help) or regex matches should help you avoid this alert.