Verify Azure DLL via public key token

[paulmedynski]

Description

• Consolidated strong name signing into Directory.Build.props.
• Added a conditional compilation constant for strong name signing.
• Added public key token check when SqlClient loads the Azure assembly.
• Added a LogWriter property to SqlClientEventSource to fork event messages to any TextWriter.

Testing

• PR runs will confirm that the public key token check is not active for un-signed builds.
• Manual run of the OneBranch pipelines, followed by manual test app will confirm that the check is active.

[Copilot]

Pull request overview

This PR consolidates strong-name signing configuration from individual project files into a centralized Directory.Build.props file and adds public key token validation for the Azure extension assembly. The changes improve maintainability by eliminating duplicated signing configuration across 11 project files and enhance security by verifying that dynamically loaded Azure authentication provider assemblies are signed with Microsoft's key.

Changes:

• Centralized strong-name signing configuration in src/Directory.Build.props with automatic STRONG_NAME_SIGNING preprocessor constant
• Removed duplicated signing configuration from 11 project files (SqlClient main/ref, SqlServer.Server, Extensions packages, AKV Provider)
• Added conditional public key token verification for Azure extension assembly in SqlAuthenticationProviderManager
• Updated pipeline template comment to reflect generic usage (not just Extension packages)

Reviewed changes

Copilot reviewed 14 out of 14 changed files in this pull request and generated 5 comments.

Show a summary per file

File	Description
src/Directory.Build.props	Added centralized strong-name signing configuration with SignAssembly, AssemblyOriginatorKeyFile, and STRONG_NAME_SIGNING constant when SigningKeyPath is specified
src/Microsoft.Data.SqlClient/src/Microsoft/Data/SqlClient/SqlAuthenticationProviderManager.cs	Added conditional public key token validation (23ec7fc2d6eaa4a5) for Azure extension assembly when STRONG_NAME_SIGNING is enabled
src/Microsoft.Data.SqlClient/src/Microsoft.Data.SqlClient.csproj	Removed duplicated signing configuration, kept InternalsVisibleTo condition for unsigned builds
src/Microsoft.Data.SqlClient/ref/Microsoft.Data.SqlClient.csproj	Removed signing configuration (now inherited from Directory.Build.props)
src/Microsoft.Data.SqlClient/netfx/src/Microsoft.Data.SqlClient.csproj	Removed duplicated signing configuration (legacy project)
src/Microsoft.Data.SqlClient/netfx/ref/Microsoft.Data.SqlClient.csproj	Removed signing configuration (legacy ref project)
src/Microsoft.Data.SqlClient/netcore/src/Microsoft.Data.SqlClient.csproj	Removed duplicated signing configuration (legacy project)
src/Microsoft.Data.SqlClient/netcore/ref/Microsoft.Data.SqlClient.csproj	Removed signing configuration (legacy ref project)
src/Microsoft.Data.SqlClient/add-ons/AzureKeyVaultProvider/Microsoft.Data.SqlClient.AlwaysEncrypted.AzureKeyVaultProvider.csproj	Removed signing configuration and simplified Trim/AOT property group
src/Microsoft.Data.SqlClient.Extensions/Logging/src/Logging.csproj	Removed duplicated signing configuration
src/Microsoft.Data.SqlClient.Extensions/Azure/src/Azure.csproj	Removed duplicated signing configuration
src/Microsoft.Data.SqlClient.Extensions/Abstractions/src/Abstractions.csproj	Removed duplicated signing configuration
src/Microsoft.SqlServer.Server/Microsoft.SqlServer.Server.csproj	Removed signing configuration block
eng/pipelines/steps/compound-build-csproj-step.yml	Updated comment to reflect generic usage (not just Extension packages)

[Copilot]

Pull request overview

Copilot reviewed 14 out of 14 changed files in this pull request and generated no new comments.

[Copilot]

Pull request overview

Copilot reviewed 14 out of 14 changed files in this pull request and generated 1 comment.

[Copilot]

@paulmedynski I've opened a new pull request, #3983, to work on those changes. Once the pull request is ready, I'll request review from you.

[codecov]

Codecov Report

❌ Patch coverage is 77.77778% with 2 lines in your changes missing coverage. Please review.
✅ Project coverage is 64.59%. Comparing base (ee71014) to head (4d0a127).
⚠️ Report is 3 commits behind head on main.

Files with missing lines	Patch %	Lines
...Data/SqlClient/SqlAuthenticationProviderManager.cs	77.77%	2 Missing ⚠️

❗ There is a different number of reports uploaded between BASE (ee71014) and HEAD (4d0a127). Click for more details.

HEAD has 1 upload less than BASE

Flag	BASE (ee71014)	HEAD (4d0a127)
CI-SqlClient	1	0

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #3978      +/-   ##
==========================================
- Coverage   72.43%   64.59%   -7.84%     
==========================================
  Files         287      282       -5     
  Lines       43105    66025   +22920     
==========================================
+ Hits        31225    42652   +11427     
- Misses      11880    23373   +11493     

Flag	Coverage Δ
CI-SqlClient	?
PR-SqlClient-Project	64.59% <77.77%> (?)

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[Copilot]

Copilot reviewed 15 out of 15 changed files in this pull request and generated 2 comments.

[Copilot]

Pull request overview

Copilot reviewed 14 out of 14 changed files in this pull request and generated 1 comment.

[Copilot]

Pull request overview

Copilot reviewed 14 out of 14 changed files in this pull request and generated no new comments.