SNOW-694457: Fix leaking HTTP_PROXY and HTTPS_PROXY environment variables

[ozturkberkay]

Please answer these questions before submitting your pull requests. Thanks!

1. What GitHub issue is this PR addressing? Make sure that there is an accompanying issue to your PR.

   Fixes SNOW-694457: Connector is leaking HTTP(S)_PROXY environment variables #1329

2. Fill out the following pre-review checklist:

   • I am adding a new automated test(s) to verify correctness of my new code
   • I am adding new logging messages
   • I am adding a new telemetry message
   • I am modifying authorization mechanisms
   • I am adding new credentials
   • I am modifying OCSP code
   • I am adding a new dependency

3. Please describe how your code solves the related issue.

   Connector is overwriting the HTTP_PROXY and HTTPS_PROXY environment variables. I think this is a big problem, the client should not overwrite any environment variable, this has caused a bunch of very hard to debug problems for me at work. Since snowflake uses the vendored requests library to send the query requests, why not just pass in the proxies to that instead of changing the environment variables? If there is a strong reason for changing the variables, I think we should do something like this:

@contextlib.contextmanager
def set_proxy_env_vars(proxy: str) -> Generator[Any, Any, None]:
    proxy_env_vars = {"HTTP_PROXY": None, "HTTPS_PROXY": None}
    for env in proxy_env_vars:
        proxy_env_vars[env] = os.environ.get(env)
        os.environ[env] = proxy
    yield
    for env, val in proxy_env_vars.items():
        os.environ[env] = val

This will change the environment variables only for the scope of the contextmanager and revert the variables back to their original values.

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[ozturkberkay]

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[ozturkberkay]

@sfc-gh-sfan I was wondering if this can prioritized?

[sfc-gh-sfan]

This change looks good to me, but I could also see potential dependency on the env var. @sfc-gh-mkeller: What do you think?

[sfc-gh-dszmolka]

hi @sfc-gh-sfan @sfc-gh-mkeller could we please look into this PR ? apparently it's still valid and would help. thank you !

[sfc-gh-mkeller]

I want to apologize, I dropped the ball on this PR. In exchange I rebased the branch onto main. The code change looks good to me

@sfc-gh-dszmolka do you have access to test this as a last sanity check before merging?

I'd especially like to know that this works with the SOCKS5 change introduced in #1398. So that we'd be sure that my rebase was good!

[sfc-gh-mkeller]

Instead of doing proxy_user or '' and proxy_password or '' I'd personally prefer to set the default values of the function to those. That'd end up changing this code to:

        auth = (
            f"{proxy_user}:{proxy_password}@"
            if proxy_user or proxy_password
            else ""
        )

I did get caught out by all those ORs, but it doesn't actually change what the code does.
This is more of my nitpick

[sfc-gh-mkeller]

@sfc-gh-aling could you please take this and get it merged once we can sanity check correctness?
I no longer feel confident merging code into this project, I haven't been operating on it for a while 😓

I did add everything that is new since the PR was opened and I know what they are

[sfc-gh-dszmolka]

@sfc-gh-mkeller @sfc-gh-aling i'm trying to sanity-test this manually , hope this is something you had in mind.
Using the example from original issue submission #1329

test script:

# cat PythonConnector1398.py 
import snowflake.connector
import os

print(f'Starting test. Proxy envvars: HTTP_PROXY={os.environ.get("HTTP_PROXY")}, HTTPS_PROXY={os.environ.get("HTTPS_PROXY")}')

proxies_to_test = ["http://my.pro.xy", "https://s.my.pro.xy", "socks5://localhost"]

for proxy_to_test in proxies_to_test:
    snowflake_config = {
      "account": os.environ.get("SFACCOUNT"),
      "user": os.environ.get("SFUSER"),
      "password": os.environ.get("SFPASS"),
      "proxy_host": proxy_to_test,
      "proxy_port": "8080",
      "no_retry": True,
      }

    print(f'=> Testing with {proxy_to_test}.')
    print(f'Before attempting to connect to Snowflake - HTTP_PROXY={os.environ.get("HTTP_PROXY")}, HTTPS_PROXY={os.environ.get("HTTPS_PROXY")}')
    try:
      # no such proxies so this will fail
      conn = snowflake.connector.connect(**snowflake_config)
      conn.close()
    except:
      print(f"Could not connect to Snowflake.")      

    print(f'After attempting to connect to Snowflake - HTTP_PROXY={os.environ.get("HTTP_PROXY")}, HTTPS_PROXY={os.environ.get("HTTPS_PROXY")}\n')

latest release PythonConnector 3.12.1 which doesn't have this PR

# pip install snowflake-connector-python==3.12.1
# python PythonConnector1398.py 
Starting test. Proxy envvars: HTTP_PROXY=None, HTTPS_PROXY=None
=> Testing with http://my.pro.xy.
Before attempting to connect to Snowflake - HTTP_PROXY=None, HTTPS_PROXY=None
Could not connect to Snowflake.
After attempting to connect to Snowflake - HTTP_PROXY=http://my.pro.xy:8080, HTTPS_PROXY=http://my.pro.xy:8080

=> Testing with https://s.my.pro.xy.
Before attempting to connect to Snowflake - HTTP_PROXY=http://my.pro.xy:8080, HTTPS_PROXY=http://my.pro.xy:8080
Could not connect to Snowflake.
After attempting to connect to Snowflake - HTTP_PROXY=http://s.my.pro.xy:8080, HTTPS_PROXY=http://s.my.pro.xy:8080

=> Testing with socks5://localhost.
Before attempting to connect to Snowflake - HTTP_PROXY=http://s.my.pro.xy:8080, HTTPS_PROXY=http://s.my.pro.xy:8080
Could not connect to Snowflake.
After attempting to connect to Snowflake - HTTP_PROXY=http://socks5://localhost:8080, HTTPS_PROXY=http://socks5://localhost:8080

(also observe how the socks5:// scheme is somehow detected as ... nothing, but part of the proxy hostname? then added to the detected scheme http://)

this PR

# <spun up a brand new container python:3.11-bookworm to avoid messing with env>
# pip install git+https://github.com/snowflakedb/snowflake-connector-python.git@refs/pull/1398/head
root@ce6aa87f78ab:/test# pip install git+https://github.com/snowflakedb/snowflake-connector-python.git@refs/pull/1398/head
Collecting git+https://github.com/snowflakedb/snowflake-connector-python.git@refs/pull/1398/head
..
  Running command git checkout -q d71ab887593f489b2aaf7b8431f06535e60a97d8
  Resolved https://github.com/snowflakedb/snowflake-connector-python.git to commit d71ab887593f489b2aaf7b8431f06535e60a97d8
Successfully built snowflake-connector-python
# python PythonConnector1398.py 
Starting test. Proxy envvars: HTTP_PROXY=None, HTTPS_PROXY=None
=> Testing with http://my.pro.xy.
Before attempting to connect to Snowflake - HTTP_PROXY=None, HTTPS_PROXY=None
Could not connect to Snowflake.
After attempting to connect to Snowflake - HTTP_PROXY=None, HTTPS_PROXY=None

=> Testing with https://s.my.pro.xy.
Before attempting to connect to Snowflake - HTTP_PROXY=None, HTTPS_PROXY=None
Could not connect to Snowflake.
After attempting to connect to Snowflake - HTTP_PROXY=None, HTTPS_PROXY=None

=> Testing with socks5://localhost.
Before attempting to connect to Snowflake - HTTP_PROXY=None, HTTPS_PROXY=None
Could not connect to Snowflake.
After attempting to connect to Snowflake - HTTP_PROXY=None, HTTPS_PROXY=None

Looks good at the first glance. Do you need me to test anything else, or did i miss something perhaps?

I would also like to add that even with current-version 3.12.1, subsequent runs of the test script shows proxies as None, so it doesn't seem to be actually changed OS-wide, but rather inside the process. Which might be still bad enough of course.

edit: adding an existing proxy (listening on http) to the test shows that the connector installed from the PR correctly passes the request to the proxy without changing the envvar value