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FEAT: Add "token_provider= " parameter for custom Azure Identity credential support - #603

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FEAT: Add "token_provider= " parameter for custom Azure Identity credential support#603
jahnvi480 wants to merge 32 commits into
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jahnvi/custom-credential-support

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@jahnvi480 jahnvi480 commented May 27, 2026

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Work Item / Issue Reference

AB#45121

GitHub Issue: #577


Summary

This pull request introduces a new token_provider parameter for Microsoft Entra ID (Azure AD) authentication, enabling the use of any credential object with a .get_token(scope) method (such as those from azure-identity). It also adds robust support for custom credential objects, improves token acquisition error handling, and refines identity key computation for connection pooling. Several internal utilities and documentation comments have been added to clarify and harden the authentication process.

Authentication and Token Provider Support:

  • Added a token_provider parameter to connect() and the Connection class, accepting any object with a get_token(scope) method for Microsoft Entra ID authentication (e.g., DefaultAzureCredential, AzureCliCredential, ManagedIdentityCredential). This is mutually exclusive with Authentication= in the connection string and with pre-acquired tokens in attrs_before. Bulk copy operations now re-acquire a fresh token from the provider for each operation.
  • Introduced the TokenProvider protocol to define the expected interface for custom credential objects, ensuring compatibility with both minimal implementations and all azure-identity credentials.

Token Acquisition and Error Handling:

  • Added _get_token_from_credential, acquire_token_from_credential, and acquire_raw_token_from_credential utility functions to centralize token acquisition, handle errors, and log token details, including expiry. These functions provide clear error messages for common mistakes (e.g., async credentials, missing .token attribute) and warn if an already-expired token is returned.
  • Improved documentation and logging for the Azure SQL Database OAuth scope, clarifying that only the Azure commercial cloud is supported via the token_provider path.

Connection Pooling and Identity Key Computation:

  • Refined the logic for computing connection pool identity keys: managed identities now use distinct prefixes (msi:client:<client_id> vs. msi:system), and token-based identities use a SHA-256 hash of the token. The computation is now expiry-aware and avoids collisions between system- and user-assigned identities.
  • Added compute_token_identity to encapsulate the hashing logic for token-based identity keys.

Type Checking and Coverage:

  • Updated .coveragerc to exclude type-checking-only imports from coverage, improving test accuracy.

These changes significantly improve the flexibility, reliability, and clarity of Microsoft Entra ID authentication support in the codebase.

Add a new 'credential' parameter to connect() that accepts any object
following the Azure TokenCredential protocol (.get_token() method).
This allows users to authenticate with any azure-identity credential
class without being limited to the driver's hardcoded credential map.

Changes:
- auth.py: Add _get_token_from_credential() shared helper,
  acquire_token_from_credential(), acquire_raw_token_from_credential()
- db_connection.py: Add credential=None parameter to connect()
- connection.py: Validate credential, acquire token, store for
  bulk copy token refresh. Mutually exclusive with Authentication=
- cursor.py: Check _custom_credential before _auth_type in bulk copy
- constants.py: Unify _KEY_* constants with _ALLOWED_CONNECTION_STRING_PARAMS
  to use single source of truth (_CONNECTION_STRING_*_KEY pattern)
- test_008_auth.py: Add 12 new tests for custom credential flow

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Pull request overview

This PR adds a new credential= parameter to the public connection API to support custom Azure Identity (Entra ID) credential objects for token acquisition, and wires that credential through to bulk copy so fresh tokens can be acquired when needed.

Changes:

  • Added credential parameter to connect() / Connection to accept objects implementing .get_token(scope).
  • Implemented credential-based token acquisition helpers in auth.py and integrated credential token usage into Cursor.bulkcopy().
  • Refactored connection-string key constants and added test coverage for the new credential flows.

Reviewed changes

Copilot reviewed 6 out of 6 changed files in this pull request and generated 2 comments.

Show a summary per file
File Description
tests/test_008_auth.py Adds unit tests for the new credential token helpers and connect(..., credential=...) behaviors.
mssql_python/db_connection.py Extends the connect() API to accept and forward the new credential parameter.
mssql_python/cursor.py Updates bulk copy to acquire a fresh token from a user-supplied custom credential when present.
mssql_python/constants.py Refactors connection-string key constants/aliases used by auth/connection code.
mssql_python/connection.py Implements the new credential parameter behavior (validation, token acquisition, mutual exclusivity with Authentication=).
mssql_python/auth.py Adds centralized helpers for acquiring raw tokens / ODBC token structs from custom credentials.

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Comment thread mssql_python/connection.py Outdated
Comment thread mssql_python/db_connection.py
jahnvi480 added 2 commits May 27, 2026 19:51
- Strip UID/PWD/Trusted_Connection from connection_str when credential=
  is used (same as Authentication= path) to avoid leaking unused secrets
- Add credential= parameter to Connection.__init__ and connect() in
  mssql_python.pyi type stubs
The _make_cursor helper uses MagicMock for the connection, which
auto-creates truthy attributes. Without explicitly setting
_custom_credential = None, the bulk copy code takes the custom
credential path instead of the expected _auth_type path.
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📊 Code Coverage Report

🔥 Diff Coverage

98%


🎯 Overall Coverage

81%


📈 Total Lines Covered: 7161 out of 8770
📁 Project: mssql-python


Diff Coverage

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

  • mssql_python/init.py (100%)
  • mssql_python/auth.py (97.9%): Missing lines 727
  • mssql_python/connection.py (98.1%): Missing lines 84
  • mssql_python/constants.py (100%)
  • mssql_python/db_connection.py (100%)

Summary

  • Total: 109 lines
  • Missing: 2 lines
  • Coverage: 98%

mssql_python/auth.py

Lines 723-731

  723         frame = frame.f_back
  724         level += 1
  725     # Every frame was internal (not expected in practice); fall back to the
  726     # outermost real frame rather than blaming this helper.
! 727     return max(level - 1, 1)
  728 
  729 
  730 def _get_token_from_credential(
  731     credential: "TokenCredential",

mssql_python/connection.py

Lines 80-88

  80     """
  81 
  82     def get_token(self, scope: str) -> Any:
  83         """Return an object with a ``.token`` attribute for ``scope``."""
! 84         ...
  85 
  86 
  87 # Add SQL_WMETADATA constant for metadata decoding configuration
  88 SQL_WMETADATA: int = -99  # Special flag for column name decoding


📋 Files Needing Attention

📉 Files with overall lowest coverage (click to expand)
mssql_python.pybind.logger_bridge.cpp: 59.2%
mssql_python.pybind.ddbc_bindings.h: 59.9%
mssql_python.pybind.logger_bridge.hpp: 70.8%
mssql_python.pybind.ddbc_bindings.cpp: 76.3%
mssql_python.__init__.py: 77.6%
mssql_python.row.py: 77.6%
mssql_python.ddbc_bindings.py: 79.6%
mssql_python.pybind.connection.connection_pool.cpp: 81.4%
mssql_python.pybind.connection.connection.cpp: 83.7%
mssql_python.logging.py: 85.5%

🔗 Quick Links

⚙️ Build Summary 📋 Coverage Details

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jahnvi480 and others added 3 commits May 27, 2026 22:00
Rename the public API parameter from 'credential' to 'token_provider'
to reduce ambiguity in our multi-auth-path context. 'credential' could
be confused with SQL auth username/password; 'token_provider' clearly
signals token-based Entra ID auth.

- Rename parameter: credential -> token_provider (connect, Connection)
- Rename internal attr: _custom_credential -> _token_provider
- Update error messages, docstrings, comments, .pyi stubs
- Improve docstring with usage example and explicit guidance
- All 97 tests pass
@jahnvi480 jahnvi480 changed the title FEAT: Add "credential= " parameter for custom Azure Identity credential support FEAT: Add "token_provider= " parameter for custom Azure Identity credential support May 29, 2026
@jahnvi480
jahnvi480 marked this pull request as draft June 2, 2026 03:17
jahnvi480 and others added 4 commits June 23, 2026 13:49
…ial-support

# Conflicts:
#	mssql_python/cursor.py
#	tests/test_008_auth.py
…lk-copy token branch

C2: capture token expires_on from custom credential and store on connection. C3: raise DB-API InterfaceError/OperationalError instead of ValueError/TypeError for token_provider misuse and acquisition failures. Add unit tests covering the cursor bulk-copy token_provider branch (success, get_token failure, invalid token).
@github-actions github-actions Bot added pr-size: large Substantial code update and removed pr-size: medium Moderate update size labels Jun 25, 2026
jahnvi480 and others added 6 commits June 26, 2026 10:05
…ol typing; fix docstring error type

- auth.py: type credential params as TokenProvider Protocol; hard-code commercial-cloud scope
- connection.py: warn on ignored UID/PWD/Trusted_Connection when token_provider set; validate get_token arity; document token lifecycle limitations
- db_connection.py: note sovereign clouds out of scope
- test_008_auth.py: cover arity validation and dropped-credential warning
…al collision

The native connection pool keys on the sanitized connection string only, and
the access token lives in attrs_before (applied once on a new physical
connection, never re-applied on reuse). Two different principals sharing the
same Server/Database collapsed into one pool bucket, so one caller could be
handed another's authenticated connection (silent identity confusion).

Fix: Connection.__init__ disables pooling whenever SQL_COPT_SS_ACCESS_TOKEN is
present in attrs_before. One condition covers all access-token paths: raw
attrs_before token, built-in Authentication=ActiveDirectory* (token-injecting),
and token_provider=. Driver-native paths (e.g. ServicePrincipal) keep creds in
the connection string and remain poolable.

Adds regression tests in TestTokenProviderPooling.
- Remove unnecessary f-prefix from two non-interpolated SQL_WCHAR error
  strings in connection.py (flagged by flake8-no-fstring-u style linters).
- Type token_provider as Optional[TokenProvider] (was Optional[object]) in
  the .pyi stubs for Connection.__init__ and connect(), matching the runtime.
- Drop the 'See docs/DESIGN_TOKEN_PROVIDER_SUPPORT.md' comment in connection.py
  (that file is not part of the PR).
- The expired-token warning in _get_token_from_credential is reached via two
  call chains at different depths (connect vs bulk-copy), so a fixed stacklevel
  cannot point at user code for both. Compute the stacklevel dynamically via
  _stacklevel_to_caller(), which walks out of the package to the first external
  frame. Works across all supported Python versions.
…token warning

The _stacklevel_to_caller() helper walked frames on every expired-token warning
and relied on __file__ (fragile under zipimport/frozen deploys). The expired
case is rare and the message is self-explanatory, so a fixed stacklevel=2 is
sufficient. Removes the helper, _PACKAGE_DIR, and the now-unused os import.
@jahnvi480
jahnvi480 marked this pull request as ready for review June 29, 2026 05:15
@jahnvi480
jahnvi480 marked this pull request as draft June 29, 2026 09:30
Comment thread mssql_python/connection.py Outdated
jahnvi480 added a commit that referenced this pull request Jul 3, 2026
…#659)

For MSI auth the identity (client id) is known without a token, so the pool key can be computed up front. Acquisition of the access token is deferred to an internal token_factory callback that the native layer invokes only when it opens a physical connection. A same-identity pool hit therefore reuses the pooled connection and never pays for a token.

Token-dependent identities (DefaultAzureCredential / raw token / interactive / device-code) still acquire eagerly because the pool key is the token hash.

The internal token_factory is intentionally distinct from the public token_provider= credential API proposed in PR #603 (issue #577).
Integrate identity-aware connection pooling (#660) from main and remove the now-obsolete access-token pooling-disable guard. With the identity-aware pool key (connStr + msi:/acct:/tok: identity), access-token connections (token_provider=, built-in Authentication=ActiveDirectory*, and raw SQL_COPT_SS_ACCESS_TOKEN) are safe to pool: distinct principals land in distinct pool buckets, while same-identity reuse benefits from pooling.

- connection.py: drop the disable-pooling guard; fix the 'if token_provider / elif Authentication' chain broken by the auto-merge; update the pooling docstring note.

- test_008_auth.py: TestTokenProviderPooling now asserts pooling is enabled with an identity-aware pool key for every access-token path.

- auth.py / test_020: resolve merge conflicts; consolidate the OAuth scope constant on _SQL_SCOPE.
@jahnvi480
jahnvi480 requested a review from sdebruyn July 27, 2026 10:02
@sumitmsft

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Looks good.. have some minor comments but not very critical to solve and can be ignored.

sumitmsft
sumitmsft previously approved these changes Jul 31, 2026
@jahnvi480
jahnvi480 dismissed sdebruyn’s stale review July 31, 2026 07:54

Please re-review

@bewithgaurav bewithgaurav left a comment

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added comments inline, the PR description needs revision - requesting changes
can skip some minor ones if needed

Comment thread mssql_python/db_connection.py
Comment thread mssql_python/auth.py
Comment thread tests/test_020_bulkcopy_auth_cleanup.py
Comment thread mssql_python/connection.py Outdated
Comment thread mssql_python/cursor.py Outdated
Comment thread mssql_python/cursor.py Outdated
Comment thread tests/test_008_auth.py Outdated
Comment thread tests/test_008_auth.py Outdated
Comment thread mssql_python/mssql_python.pyi
…on, MSI disjoint encoding, acct account-binding)

Revert token_provider= pooling from credential object-identity back to token-hash (tok:) keying: object identity assumes a credential object maps to a stable principal, but mutable credentials (e.g. AzureCliCredential) can mint different principals from the same object, so a pool hit could hand back a stale-principal connection. Token-hash re-derives identity from the actual token every connect.

Additional hardening: reject embedded NUL in connection string/kwargs at the Python boundary; encode MSI identities disjointly (msi:client:<id> vs msi:system); bind the deferred acct: token factory to the pooled home_account_id; add compute_token_identity helper; freeze bytearray raw tokens to immutable bytes; derive warning stacklevel dynamically.
The .pyi stub is not shipped (not in setup.py package_data) and is misnamed
for a package stub, so type checkers never read it. Real type info for
token_provider comes from inline hints in db_connection.py plus the shipped
py.typed marker. Reverting keeps the PR surgical; ship-vs-delete of the stub
file is tracked as a separate backlog item.
- Re-export TokenProvider from the package root so rom mssql_python import
  TokenProvider works for type annotations (added to __all__).
- Normalize MSI client_id (strip {braces}, lowercase) in compute_identity_key
  so the same managed identity keys one pool regardless of GUID casing/bracing.
- Downgrade the already-expired-token diagnostic from warnings.warn to
  logger.warning so it is never promoted to an exception under -W error.
- Type _token_expires_on as Optional[float] (a custom provider may report a
  float POSIX timestamp).
- CHANGELOG: note that NUL characters in connection strings/params are now
  rejected with InterfaceError instead of being silently truncated.

Tests updated accordingly (log assertion instead of pytest.warns) plus new
cases for the re-export and client_id normalization.
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