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[MSI V2] - Adds Authentication Operation to MSI v2 mTLS flows #5533

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Merged
Parent: ImdsV2: Merge into Main
merged 4 commits into from
Oct 24, 2025
Merged

[MSI V2] - Adds Authentication Operation to MSI v2 mTLS flows #5533

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gladjohn Oct 15, 2025
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gladjohn Oct 16, 2025
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gladjohn Oct 22, 2025
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gladjohn Oct 24, 2025
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4 changes: 4 additions & 0 deletions ...icrosoft.Identity.Client/ApiConfig/Parameters/AcquireTokenForManagedIdentityParameters.cs
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Expand Up @@ -4,6 +4,7 @@
using System;
using System.Collections.Generic;
using System.Linq;
using System.Security.Cryptography.X509Certificates;
using System.Text;
using System.Threading;
using System.Threading.Tasks;
Expand All @@ -26,6 +27,8 @@ internal class AcquireTokenForManagedIdentityParameters : IAcquireTokenParameter

internal Func<AttestationTokenInput, CancellationToken, Task<AttestationTokenResponse>> AttestationTokenProvider { get; set; }

internal X509Certificate2 MtlsCertificate { get; set; }

public void LogParameters(ILoggerAdapter logger)
{
if (logger.IsLoggingEnabled(LogLevel.Info))
Expand All @@ -37,6 +40,7 @@ public void LogParameters(ILoggerAdapter logger)
Resource: {Resource}
Claims: {!string.IsNullOrEmpty(Claims)}
RevokedTokenHash: {!string.IsNullOrEmpty(RevokedTokenHash)}
IsMtlsPopRequested: {IsMtlsPopRequested}
""");
}
}
Expand Down
12 changes: 11 additions & 1 deletion src/client/Microsoft.Identity.Client/Internal/Requests/AuthenticationRequestParameters.cs
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Expand Up @@ -127,7 +127,17 @@ public string Claims
}
}

public IAuthenticationOperation AuthenticationScheme => _commonParameters.AuthenticationOperation;
private IAuthenticationOperation _requestOverrideScheme;

/// <summary>
/// Effective authentication operation (scheme) for this request.
/// Defaults to the app's configured operation unless a request-scoped override is applied.
/// </summary>
public IAuthenticationOperation AuthenticationScheme
{
get => _requestOverrideScheme ?? _commonParameters.AuthenticationOperation;
internal set => _requestOverrideScheme = value;
}

public IEnumerable<string> PersistedCacheParameters => _commonParameters.AdditionalCacheParameters;

Expand Down
30 changes: 30 additions & 0 deletions src/client/Microsoft.Identity.Client/Internal/Requests/ManagedIdentityAuthRequest.cs
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Expand Up @@ -2,9 +2,11 @@
// Licensed under the MIT License.

using System.Collections.Generic;
using System.Security.Cryptography.X509Certificates;
using System.Threading;
using System.Threading.Tasks;
using Microsoft.Identity.Client.ApiConfig.Parameters;
using Microsoft.Identity.Client.AuthScheme.PoP;
using Microsoft.Identity.Client.Cache.Items;
using Microsoft.Identity.Client.Core;
using Microsoft.Identity.Client.ManagedIdentity;
Expand Down Expand Up @@ -39,6 +41,20 @@ protected override async Task<AuthenticationResult> ExecuteAsync(CancellationTok
{
AuthenticationResult authResult = null;
ILoggerAdapter logger = AuthenticationRequestParameters.RequestContext.Logger;

// Prime the scheme before any cache lookup if we already have a binding cert from a prior mint
if (AuthenticationRequestParameters.IsMtlsPopRequested)
{
if (_managedIdentityClient.RuntimeMtlsBindingCertificate != null)
{
AuthenticationRequestParameters.AuthenticationScheme = new MtlsPopAuthenticationOperation(_managedIdentityClient.RuntimeMtlsBindingCertificate);

logger.Info("[ManagedIdentity] Using prior mTLS binding certificate for cache lookup.");
logger.InfoPii(
() => $"[ManagedIdentity][PII] Prior mTLS cert thumbprint: {_managedIdentityClient.RuntimeMtlsBindingCertificate.Thumbprint}",
() => "[ManagedIdentity][PII] Prior mTLS cert thumbprint: ***");
}
}

// 1. FIRST, handle ForceRefresh
if (_managedIdentityParameters.ForceRefresh)
Expand Down Expand Up @@ -209,6 +225,20 @@ await _managedIdentityClient
.SendTokenRequestForManagedIdentityAsync(AuthenticationRequestParameters.RequestContext, _managedIdentityParameters, cancellationToken)
.ConfigureAwait(false);

if (AuthenticationRequestParameters.IsMtlsPopRequested && _managedIdentityParameters.MtlsCertificate != null)
{
// Remember the cert...
_managedIdentityClient.SetRuntimeMtlsBindingCertificate(_managedIdentityParameters.MtlsCertificate);

// Apply mTLS scheme BEFORE caching...
AuthenticationRequestParameters.AuthenticationScheme =
new MtlsPopAuthenticationOperation(_managedIdentityParameters.MtlsCertificate);

_managedIdentityParameters.MtlsCertificate = null;
AuthenticationRequestParameters.RequestContext.Logger.Info(
"[ManagedIdentity] Applied mtls_pop scheme prior to caching.");
}

var msalTokenResponse = MsalTokenResponse.CreateFromManagedIdentityResponse(managedIdentityResponse);
msalTokenResponse.Scope = AuthenticationRequestParameters.Scope.AsSingleString();

Expand Down
8 changes: 8 additions & 0 deletions src/client/Microsoft.Identity.Client/ManagedIdentity/AbstractManagedIdentity.cs
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Expand Up @@ -61,6 +61,14 @@ public virtual async Task<ManagedIdentityResponse> AuthenticateAsync(

ManagedIdentityRequest request = await CreateRequestAsync(resource).ConfigureAwait(false);

// When IMDSv2 mints a binding certificate during this request (via CSR),
// it's exposed via request.MtlsCertificate. Bubble it up so the request
// layer can set the mtls_pop scheme
if (parameters.IsMtlsPopRequested && request?.MtlsCertificate != null)
{
parameters.MtlsCertificate = request.MtlsCertificate;
}

// Automatically add claims / capabilities if this MI source supports them
if (_sourceType.SupportsClaimsAndCapabilities())
{
Expand Down
20 changes: 20 additions & 0 deletions src/client/Microsoft.Identity.Client/ManagedIdentity/ManagedIdentityClient.cs
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Expand Up @@ -10,6 +10,7 @@
using System.IO;
using Microsoft.Identity.Client.Core;
using Microsoft.Identity.Client.ManagedIdentity.V2;
using System.Security.Cryptography.X509Certificates;

namespace Microsoft.Identity.Client.ManagedIdentity
{
Expand All @@ -22,6 +23,10 @@ internal class ManagedIdentityClient
private const string LinuxHimdsFilePath = "/opt/azcmagent/bin/himds";
internal static ManagedIdentitySource s_sourceName = ManagedIdentitySource.None;

// Holds the most recently minted mTLS binding certificate for this application instance.
private X509Certificate2 _runtimeMtlsBindingCertificate;
internal X509Certificate2 RuntimeMtlsBindingCertificate => Volatile.Read(ref _runtimeMtlsBindingCertificate);

internal static void ResetSourceForTest()
{
s_sourceName = ManagedIdentitySource.None;
Expand Down Expand Up @@ -157,5 +162,20 @@ private static bool ValidateAzureArcEnvironment(string identityEndpoint, string
logger?.Verbose(() => "[Managed Identity] Azure Arc managed identity is not available.");
return false;
}

/// <summary>
/// Sets (or replaces) the in-memory binding certificate used to prime the mtls_pop scheme on subsequent requests.
/// The certificate is intentionally NOT disposed here to avoid invalidating caller-held references (e.g., via AuthenticationResult).
/// </summary>
/// <remarks>
/// Lifetime considerations:
/// - The binding certificate is ephemeral and valid for the token’s binding duration.
/// - If rotation occurs, older certificates will be eligible for GC once no longer referenced.
/// - Explicit disposal can be revisited if a deterministic rotation / shutdown strategy is introduced.
/// </remarks>
internal void SetRuntimeMtlsBindingCertificate(X509Certificate2 cert)
{
Volatile.Write(ref _runtimeMtlsBindingCertificate, cert);
}
}
}
55 changes: 24 additions & 31 deletions tests/Microsoft.Identity.Test.Unit/ManagedIdentityTests/ImdsV2Tests.cs
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Expand Up @@ -314,20 +314,19 @@ public async Task mTLSPopTokenHappyPath(
Assert.IsNotNull(result);
Assert.IsNotNull(result.AccessToken);
Assert.AreEqual(result.TokenType, MTLSPoP);
// Assert.IsNotNull(result.BindingCertificate); // TODO: implement mTLS Pop BindingCertificate
Assert.IsNotNull(result.BindingCertificate);
Assert.AreEqual(TokenSource.IdentityProvider, result.AuthenticationResultMetadata.TokenSource);

// TODO: broken until Gladwin's PR is merged in
/*result = await managedIdentityApp.AcquireTokenForManagedIdentity(ManagedIdentityTests.Resource)
result = await managedIdentityApp.AcquireTokenForManagedIdentity(ManagedIdentityTests.Resource)
.WithMtlsProofOfPossession()
.WithAttestationProviderForTests(s_fakeAttestationProvider)
.ExecuteAsync().ConfigureAwait(false);

Assert.IsNotNull(result);
Assert.IsNotNull(result.AccessToken);
Assert.AreEqual(result.TokenType, MTLSPoP);
// Assert.IsNotNull(result.BindingCertificate); // TODO: implement mTLS Pop BindingCertificate
Assert.AreEqual(TokenSource.Cache, result.AuthenticationResultMetadata.TokenSource);*/
Assert.IsNotNull(result.BindingCertificate);
Assert.AreEqual(TokenSource.Cache, result.AuthenticationResultMetadata.TokenSource);
}
}

Expand Down Expand Up @@ -358,19 +357,18 @@ public async Task mTLSPopTokenIsPerIdentity(
Assert.IsNotNull(result);
Assert.IsNotNull(result.AccessToken);
Assert.AreEqual(result.TokenType, MTLSPoP);
// Assert.IsNotNull(result.BindingCertificate); // TODO: implement mTLS Pop BindingCertificate
Assert.IsNotNull(result.BindingCertificate);
Assert.AreEqual(TokenSource.IdentityProvider, result.AuthenticationResultMetadata.TokenSource);

// TODO: broken until Gladwin's PR is merged in
/*result = await managedIdentityApp.AcquireTokenForManagedIdentity(ManagedIdentityTests.Resource)
result = await managedIdentityApp.AcquireTokenForManagedIdentity(ManagedIdentityTests.Resource)
.WithMtlsProofOfPossession()
.ExecuteAsync().ConfigureAwait(false);

Assert.IsNotNull(result);
Assert.IsNotNull(result.AccessToken);
Assert.AreEqual(result.TokenType, MTLSPoP);
// Assert.IsNotNull(result.BindingCertificate); // TODO: implement mTLS Pop BindingCertificate
Assert.AreEqual(TokenSource.Cache, result.AuthenticationResultMetadata.TokenSource);*/
Assert.IsNotNull(result.BindingCertificate);
Assert.AreEqual(TokenSource.Cache, result.AuthenticationResultMetadata.TokenSource);
#endregion Identity 1

#region Identity 2
Expand All @@ -393,20 +391,19 @@ public async Task mTLSPopTokenIsPerIdentity(
Assert.IsNotNull(result2);
Assert.IsNotNull(result2.AccessToken);
Assert.AreEqual(result2.TokenType, MTLSPoP);
// Assert.IsNotNull(result2.BindingCertificate); // TODO: implement mTLS Pop BindingCertificate
Assert.IsNotNull(result2.BindingCertificate);
Assert.AreEqual(TokenSource.IdentityProvider, result2.AuthenticationResultMetadata.TokenSource);

// TODO: broken until Gladwin's PR is merged in
/*result2 = await managedIdentityApp2.AcquireTokenForManagedIdentity(ManagedIdentityTests.Resource)
result2 = await managedIdentityApp2.AcquireTokenForManagedIdentity(ManagedIdentityTests.Resource)
.WithMtlsProofOfPossession()
.WithAttestationProviderForTests(s_fakeAttestationProvider)
.ExecuteAsync().ConfigureAwait(false);

Assert.IsNotNull(result2);
Assert.IsNotNull(result2.AccessToken);
Assert.AreEqual(result2.TokenType, MTLSPoP);
// Assert.IsNotNull(result2.BindingCertificate); // TODO: implement mTLS Pop BindingCertificate
Assert.AreEqual(TokenSource.Cache, result2.AuthenticationResultMetadata.TokenSource);*/
Assert.IsNotNull(result2.BindingCertificate);
Assert.AreEqual(TokenSource.Cache, result2.AuthenticationResultMetadata.TokenSource);
#endregion Identity 2

// TODO: Assert.AreEqual(CertificateCache.Count, 2);
Expand Down Expand Up @@ -439,26 +436,22 @@ public async Task mTLSPopTokenIsReAcquiredWhenCertificatIsExpired(
Assert.IsNotNull(result);
Assert.IsNotNull(result.AccessToken);
Assert.AreEqual(result.TokenType, MTLSPoP);
// Assert.IsNotNull(result.BindingCertificate); // TODO: implement mTLS Pop BindingCertificate
Assert.IsNotNull(result.BindingCertificate);
Assert.AreEqual(TokenSource.IdentityProvider, result.AuthenticationResultMetadata.TokenSource);

// TODO: Add functionality to check cert expiration in the cache
/**
AddMocksToGetEntraToken(httpManager, userAssignedIdentityId, userAssignedId, mTLSPop: true);

result = await managedIdentityApp.AcquireTokenForManagedIdentity(ManagedIdentityTests.Resource)
.WithMtlsProofOfPossession()
.WithAttestationProviderForTests(s_fakeAttestationProvider)
.ExecuteAsync().ConfigureAwait(false);
//To-Do : Add cert expiry check functionality
//AddMocksToGetEntraToken(httpManager, userAssignedIdentityId, userAssignedId, mTLSPop: true);

Assert.IsNotNull(result);
Assert.IsNotNull(result.AccessToken);
Assert.AreEqual(result.TokenType, MTLSPoP);
// Assert.IsNotNull(result.BindingCertificate); // TODO: implement mTLS Pop BindingCertificate
Assert.AreEqual(TokenSource.IdentityProvider, result.AuthenticationResultMetadata.TokenSource);
//result = await managedIdentityApp.AcquireTokenForManagedIdentity(ManagedIdentityTests.Resource)
// .WithMtlsProofOfPossession()
// .WithAttestationProviderForTests(s_fakeAttestationProvider)
// .ExecuteAsync().ConfigureAwait(false);

Assert.AreEqual(CertificateCache.Count, 1); // expired cert was removed from the cache
*/
//Assert.IsNotNull(result);
//Assert.IsNotNull(result.AccessToken);
//Assert.AreEqual(result.TokenType, MTLSPoP);
//Assert.IsNotNull(result.BindingCertificate);
//Assert.AreEqual(TokenSource.IdentityProvider, result.AuthenticationResultMetadata.TokenSource);
}
}
#endregion mTLS Pop Token Tests
Expand Down