FEAT: Add ActiveDirectoryMSI support for bulk copy by bewithgaurav · Pull Request #573 · microsoft/mssql-python

bewithgaurav · 2026-05-12T12:09:27Z

Work Item / Issue Reference

AB#

GitHub Issue: #534

Summary

Adds Authentication=ActiveDirectoryMSI support to bulk copy. Partial fix for #534.

Zero-arg ManagedIdentityCredential() for system-assigned MSI.
ManagedIdentityCredential(client_id=UID) for user-assigned MSI. Matches ODBC convention where UID carries the identity's client_id under MSI.
Threads optional credential_kwargs through get_auth_token / get_raw_token / _acquire_token so future auth methods that need constructor args plug in via the same channel.
Credential cache key stays a plain string for zero-arg auth types and becomes a tuple (auth_type, sorted_kwargs) when kwargs are present, so different client_ids get separate cached credentials.

mssql-py-core (the Rust path used by bulk copy) doesn't itself acquire Entra tokens. Python pre-acquires a JWT and passes it as access_token. Today this works for Default, DeviceCode, and Interactive. MSI was missing, the most common Azure-hosted-service auth method.

ServicePrincipal and Password are explicitly out of scope for this PR. They need different design work and ship separately.

How user-assigned MSI survives the bulkcopy fresh-token path

Connection.__init__ calls process_connection_string, which sanitizes self.connection_str (strips UID=, Authentication=, PWD=). Bulkcopy needs a fresh token at copy time. Re-parsing self.connection_str at that point would lose UID and silently degrade user-assigned MSI to system-assigned (wrong-identity bug).

Fix shape: process_connection_string returns a 4-tuple including the captured credential_kwargs. Connection.__init__ persists _credential_kwargs alongside _auth_type. cursor.bulkcopy() reads self.connection._credential_kwargs directly. No re-parse, no chance for the sanitized string to drop the client_id.

Connection string examples

# System-assigned MSI
"Server=tcp:foo.database.windows.net;Authentication=ActiveDirectoryMSI;Database=mydb;"

# User-assigned MSI
"Server=tcp:foo.database.windows.net;Authentication=ActiveDirectoryMSI;UID=<client_id_guid>;Database=mydb;"

Adds Authentication=ActiveDirectoryMSI to the auth pipeline: - Zero-arg ManagedIdentityCredential() for system-assigned MSI. - ManagedIdentityCredential(client_id=UID) for user-assigned MSI, matching ODBC's convention where UID carries the identity's client_id under MSI. - Threads optional credential_kwargs through get_auth_token / get_raw_token / _acquire_token so future auth methods that need constructor args (e.g. ClientSecretCredential) can plug in via the same channel. - Cache key remains a plain string for zero-arg auth types and becomes a tuple when kwargs are present, so different client_ids get separate cached credentials. Partial fix for #534. ServicePrincipal and Password to follow as separate PRs.

Copilot

Pull request overview

Adds support for Authentication=ActiveDirectoryMSI (managed identity) token acquisition for the bulk copy (mssql-py-core) path, including user-assigned MSI via UID=<client_id>.

Changes:

Add AuthType.MSI (activedirectorymsi) and map it to ManagedIdentityCredential.
Thread optional credential_kwargs through token acquisition and update the credential-instance cache key to incorporate kwargs.
Attempt to extract MSI client_id from the connection string and pass it into bulk copy token acquisition; add tests and a changelog entry.

Reviewed changes

Copilot reviewed 5 out of 5 changed files in this pull request and generated 3 comments.

Show a summary per file

File	Description
`mssql_python/constants.py`	Adds `AuthType.MSI` enum value.
`mssql_python/auth.py`	Adds MSI credential support, credential kwargs plumbing, and cache key changes; adds `extract_credential_kwargs`.
`mssql_python/cursor.py`	Bulk copy now tries to extract MSI credential kwargs and pass them to `get_raw_token`.
`tests/test_008_auth.py`	Adds tests for MSI auth type parsing, credential construction, cache isolation, and connection-string processing.
`CHANGELOG.md`	Documents MSI support for bulk copy.

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Connection.__init__ overwrites self.connection_str with the sanitized (UID-stripped) string returned by process_connection_string. The original implementation re-parsed self.connection_str at bulkcopy time via extract_credential_kwargs, which silently dropped the user-assigned MSI client_id and degraded to system-assigned a wrong-identity bug.MSI Changes: - process_connection_string now returns a 4-tuple including the captured credential_kwargs so callers can persist them. - Connection.__init__ stores _credential_kwargs alongside _auth_type. - cursor.bulkcopy() reads self.connection._credential_kwargs instead of re-parsing self.connection_str. - The public extract_credential_kwargs helper is removed (it only existed to support the broken re-parse path; nothing else needs it). - black --line-length=100 reformats (CI was red). Tests: - test_bulkcopy_path_preserves_user_assigned_msi_client_id: invokes cursor.bulkcopy() with a mocked mssql_py_core, patches AADAuth.get_raw_token to capture the args it receives, and asserts the captured credential_kwargs match Connection._credential_kwargs. Fails if cursor reverts to re-parsing self.connection.connection_str. - test_credential_kwargs_persisted_for_user_assigned_msi: asserts Connection.__init__ stores _credential_kwargs from the 4-tuple. - test_credential_kwargs_none_for_system_assigned_msi. - test_credential_kwargs_none_for_non_msi_auth. Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

)

saurabh500 · 2026-05-14T12:40:46Z

+    identity's client_id. Returns None for system-assigned MSI.
+    """
+    for param in parameters:
+        key, _, value = param.strip().partition("=")


Is it possible to get this from the conn str parser map? Assuming we need the conn str UID

I am not sure what will happen if someone provides a UID={hello=world}

thanks - missed this, parser should be used as a standard across
that handles {hello=world} correctly

@saurabh500

Per @saurabh500's review: braced ODBC values like UID={hello=world} need the canonical parser, not naive partition('='). Without this, the helper returns '{hello=world}' verbatim and ManagedIdentityCredential rejects it. Worse, a UID containing a literal ';' would be truncated. _extract_msi_client_id now delegates to _ConnectionStringParser, which handles braces, escaped '}}' inside braces, and '=' inside braced values correctly. validate_keywords=False so the helper never raises on keys the auth flow doesn't care about. Tests: - test_msi_braced_uid_value_is_unwrapped: UID={hello=world} -> 'hello=world' - test_msi_braced_uid_with_semicolon_is_preserved: UID={abc;def;ghi} Note: process_connection_string and extract_auth_type still use naive split(';') for Authentication= detection across all Entra ID auth types. That's pre-existing and tracked separately for a parser-wide refactor. Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

…microsoft/mssql-python into bewithgaurav/gh534-bulkcopy-msi

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

saurabh500 · 2026-05-14T13:29:05Z

+    except Exception:  # noqa: BLE001 — parser raises ConnectionStringParseError on malformed input;
+        # absence of UID is the safe answer for credential extraction.
+        return None
+    uid = (parsed.get("uid") or "").strip()


I dont know if this is the right place, but we are kind of downgrading to SAMI if UAMI uid is not found.

Since we are falling back, do you think it makes sense to add a logging statement to help debug if needed?

yes you're correct - the fallback to SAMI is expected and as per the ODBC behaviour
added logger statements for better debugging help, thanks for the suggestion!

saurabh500 · 2026-05-14T13:33:23Z

        try:
            with _credential_cache_lock:
-                if auth_type not in _credential_cache:
+                if cache_key not in _credential_cache:


There is no pruning of credential cache. I don't think its needed right now, but I would encourage adding a comment about it.

This case is not usually possible but in some crazy scenario where the same app is serving requests for Multi-tenants (I don't think ODBC supports multi tenant Managed Identity yet).

added a comment to reference this just above the _credential_cache declaration

- Debug log distinguishing user-assigned vs system-assigned MSI when the user passes Authentication=ActiveDirectoryMSI. Helps diagnose which branch was taken when token acquisition fails. Logs client_id length, not value (still identity material). - Comment above _credential_cache explains the cache key shape so the unbounded growth is understood as a deliberate choice rather than an oversight. Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

github-actions · 2026-05-14T14:18:55Z

📊 Code Coverage Report

🔥 Diff Coverage 100%	🎯 Overall Coverage 25%	📈 Total Lines Covered: `6982` out of `27089` 📁 Project: `mssql-python`

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Diff: main...HEAD, staged and unstaged changes

mssql_python/auth.py (100%)
mssql_python/connection.py (100%)
mssql_python/constants.py (100%)

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Missing: 0 lines
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mssql_python.pybind.build._deps.simdutf-src.src.haswell.implementation.cpp: 0.4%
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mssql_python.pybind.build._deps.simdutf-src.include.simdutf.implementation.h: 10.4%
mssql_python.pybind.build._deps.simdutf-src.include.simdutf.scalar.utf16_to_utf8.utf16_to_utf8.h: 25.3%
mssql_python.pybind.logger_bridge.cpp: 59.2%
mssql_python.pybind.ddbc_bindings.h: 59.7%
mssql_python.pybind.build._deps.simdutf-src.include.simdutf.internal.isadetection.h: 65.3%
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mssql_python.pybind.ddbc_bindings.cpp: 74.2%

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Connection.__init__ already parses the same connection string through _ConnectionStringParser via _construct_connection_string (connection.py line 253) before process_connection_string is ever called. By the time _extract_msi_client_id runs, the input is guaranteed parseable. The try/except was dead code. A real parse failure here would indicate an upstream bug and should propagate, not silently degrade user-assigned MSI to system-assigned (which is the wrong-identity failure mode this PR exists to prevent). Brings diff coverage to 100%. Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

saurabh500 · 2026-05-14T14:59:17Z

+    # time we get here the input is guaranteed parseable. No defensive
+    # try/except: a parse failure now means a real bug upstream and should
+    # propagate, not silently degrade user-assigned MSI to system-assigned.
+    parsed = _ConnectionStringParser(validate_keywords=False)._parse(connection_string)


Functionally correct but a tiny perf hit due to double parsing of connections string.
Perfect solution would require parsing done earlier in the connect api and passing around the map to this function. That's a bigger change. I recommend a follow up PR and tracking with a GH issue.

An adhoc fix is to maintain a hashmap of connection string and uid. But that's prone to other problems esp concurrency.

Copilot AI review requested due to automatic review settings May 12, 2026 12:09

bewithgaurav changed the title ~~Add ActiveDirectoryMSI support for bulk copy~~ FIX: Add ActiveDirectoryMSI support for bulk copy May 12, 2026

Copilot started reviewing on behalf of bewithgaurav May 12, 2026 12:11 View session

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Comment thread mssql_python/auth.py Outdated

Comment thread tests/test_008_auth.py

bewithgaurav changed the title ~~FIX: Add ActiveDirectoryMSI support for bulk copy~~ FEAT: Add ActiveDirectoryMSI support for bulk copy May 13, 2026

bewithgaurav marked this pull request as draft May 13, 2026 12:15

bewithgaurav force-pushed the bewithgaurav/gh534-bulkcopy-msi branch from bbda2a2 to 3ca2165 Compare May 14, 2026 12:12

bewithgaurav added a commit that referenced this pull request May 14, 2026

Note follow-up to fold SP credential cache into module-level cache (#573

5ba73eb

)

Merge branch 'main' into bewithgaurav/gh534-bulkcopy-msi

66b8eec

bewithgaurav marked this pull request as ready for review May 14, 2026 12:31

github-actions Bot added the pr-size: medium Moderate update size label May 14, 2026

saurabh500 reviewed May 14, 2026

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bewithgaurav and others added 3 commits May 14, 2026 18:40

Merge branch 'bewithgaurav/gh534-bulkcopy-msi' of https://github.com/…

e106d5f

…microsoft/mssql-python into bewithgaurav/gh534-bulkcopy-msi

Drop reviewer name-drop in test docstring

ff1aa41

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saurabh500 reviewed May 14, 2026

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saurabh500 approved these changes May 14, 2026

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Merge branch 'main' into bewithgaurav/gh534-bulkcopy-msi

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bewithgaurav mentioned this pull request May 14, 2026

Avoid parsing the connection string multiple times in the auth path #580

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Summary

How user-assigned MSI survives the bulkcopy fresh-token path

Connection string examples

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bewithgaurav commented May 12, 2026 •

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