config, remote: Made S3 CA bundle customizable (#6018)

* config, remote: Made S3 CA bundle customizable

botocore allows a path to a custom CA bundle either by passing a path
to the CA bundle file into the verify argument of
boto3.session.Session.client or passing None (the default) which will
fall back to the AWS config. Previously, the DVC config only accepted a
boolean into the ssl_verify option in the remote S3 config. This changes
the DVC config to accept both string and None in addition to boolean and
defaults to None. I also changed the default for ssl_verfiy to None in
BaseS3FileSystem. Thus, if ssl_verify is not provided, botocore will
fall back to the AWS config.

Testing

Unit tests to cover the changes to the config schema and addition
ssl_verify types that will be passed into S3FileSystem. Also, ran

dvc push -r object-store data/cifar-10-python.tar.gz

in my work environment that has a private S3 endpoint that requires a
custom CA bundle, both with and without ssl_verify specified in the
config. This was successful, showing that communication could be
established. And I ran

dvc remote modify object-store ssl_verify "$HOME/.aws/cabundle.pem"

and confirmed that the custom CA bundle path was added to the config.

Fixes #6012

* Removed default None on ssl_verify

Responding to PR comment, removed the Optional, default None on
ssl_verify since the config keys are optional by default. Rather
than a missing ssl_verify producing a None that eventually gets
filtered, it doesn't appear in the parsed config in the first place.

Co-authored-by: Robert Van Wesep <robert.g.vanwesep@gsk.com>

dvc/config_schema.py

@@ -145,7 +145,7 @@ class RelPath(str):
                     "session_token": str,
                     Optional("listobjects", default=False): Bool,  # obsoleted
                     Optional("use_ssl", default=True): Bool,
-                    Optional("ssl_verify", default=True): Bool,
+                    "ssl_verify": Any(Bool, str),
                     "sse": str,
                     "sse_kms_key_id": str,
                     "acl": str,

dvc/fs/s3.py

@@ -103,7 +103,7 @@ def _prepare_credentials(self, **config):
         client = login_info["client_kwargs"]
         client["region_name"] = config.get("region")
         client["endpoint_url"] = config.get("endpointurl")
-        client["verify"] = config.get("ssl_verify", True)
+        client["verify"] = config.get("ssl_verify")
 
         # encryptions
         additional = login_info["s3_additional_kwargs"]

tests/unit/fs/test_s3.py

@@ -37,7 +37,15 @@ def test_verify_ssl_default_param(dvc):
     config = {"url": url}
     fs = S3FileSystem(**config)
 
-    assert fs.fs_args["client_kwargs"]["verify"]
+    assert "client_kwargs" not in fs.fs_args
+
+    config = {
+        "url": url,
+        "endpointurl": "https://my.custom.s3:1234",
+    }
+    fs = S3FileSystem(**config)
+
+    assert "verify" not in fs.fs_args["client_kwargs"]
 
 
 def test_s3_config_credentialpath(dvc, monkeypatch):
@@ -72,6 +80,29 @@ def test_ssl_verify_bool_param(dvc):
     assert fs.fs_args["client_kwargs"]["verify"] == config["ssl_verify"]
 
 
+def test_ssl_verify_path_param(dvc):
+    config = {"url": url, "ssl_verify": "/path/to/custom/cabundle.pem"}
+    fs = S3FileSystem(**config)
+
+    assert fs.fs_args["client_kwargs"]["verify"] == config["ssl_verify"]
+
+
+def test_ssl_verify_none_param(dvc):
+    config = {"url": url, "ssl_verify": None}
+    fs = S3FileSystem(**config)
+
+    assert "client_kwargs" not in fs.fs_args
+
+    config = {
+        "url": url,
+        "endpointurl": "https://my.custom.s3:1234",
+        "ssl_verify": None,
+    }
+    fs = S3FileSystem(**config)
+
+    assert "verify" not in fs.fs_args["client_kwargs"]
+
+
 def test_grants(dvc):
     config = {
         "url": url,

tests/unit/test_config.py

@@ -1,4 +1,5 @@
 import os
+import textwrap
 
 import pytest
 
@@ -33,3 +34,39 @@ def test_get_fs(tmp_dir, scm):
     assert config._get_fs("local") == config.wfs
     assert config._get_fs("global") == config.wfs
     assert config._get_fs("system") == config.wfs
+
+
+def test_s3_ssl_verify(tmp_dir, dvc):
+    config = Config(validate=False)
+    with config.edit() as conf:
+        conf["remote"]["remote-name"] = {"url": "s3://bucket/dvc"}
+
+    assert "ssl_verify" not in config["remote"]["remote-name"]
+
+    with config.edit() as conf:
+        section = conf["remote"]["remote-name"]
+        section["ssl_verify"] = False
+
+    assert (tmp_dir / ".dvc" / "config").read_text() == textwrap.dedent(
+        """\
+        [core]
+            no_scm = True
+        ['remote "remote-name"']
+            url = s3://bucket/dvc
+            ssl_verify = False
+        """
+    )
+
+    with config.edit() as conf:
+        section = conf["remote"]["remote-name"]
+        section["ssl_verify"] = "/path/to/custom/cabundle.pem"
+
+    assert (tmp_dir / ".dvc" / "config").read_text() == textwrap.dedent(
+        """\
+        [core]
+            no_scm = True
+        ['remote "remote-name"']
+            url = s3://bucket/dvc
+            ssl_verify = /path/to/custom/cabundle.pem
+        """
+    )