Use client assertion credential within AzurePipelinesCredential and WorkloadIdentityCredential (#5802)

* Use ClientAssertionCredential within AzurePipelinesCredential.

* Use ClientAssertionCredential in WorkloadIdentityCredential.

* Fix DefaultAzureCredentia.LogMessages test since an extra log got added.

* Disable tests that dont correctly simulate the token request and return
the test response.

* Address PR feedback and make sure base options are passed in to underlying
client assertion credential.

* Address PR feedback - move credential ctor into validation checks.

* Address PR feedback, add const.

* Add a ClientAssertionCredentialImpl to make sure logs use the calling
credential name.

sdk/identity/azure-identity/CMakeLists.txt

@@ -77,6 +77,7 @@ set(
     src/managed_identity_credential.cpp
     src/managed_identity_source.cpp
     src/private/chained_token_credential_impl.hpp
+    src/private/client_assertion_credential_impl.hpp
     src/private/identity_log.hpp
     src/private/managed_identity_source.hpp
     src/private/package_version.hpp

sdk/identity/azure-identity/inc/azure/identity/azure_pipelines_credential.hpp

@@ -8,6 +8,7 @@
 
 #pragma once
 
+#include "azure/identity/client_assertion_credential.hpp"
 #include "azure/identity/detail/client_credential_core.hpp"
 #include "azure/identity/detail/token_cache.hpp"
 
@@ -20,7 +21,7 @@
 
 namespace Azure { namespace Identity {
   namespace _detail {
-    class TokenCredentialImpl;
+    class ClientAssertionCredentialImpl;
   } // namespace _detail
 
   /**
@@ -57,12 +58,9 @@ namespace Azure { namespace Identity {
   private:
     std::string m_serviceConnectionId;
     std::string m_systemAccessToken;
-    _detail::ClientCredentialCore m_clientCredentialCore;
     Azure::Core::Http::_internal::HttpPipeline m_httpPipeline;
     std::string m_oidcRequestUrl;
-    std::unique_ptr<_detail::TokenCredentialImpl> m_tokenCredentialImpl;
-    std::string m_requestBody;
-    _detail::TokenCache m_tokenCache;
+    std::unique_ptr<_detail::ClientAssertionCredentialImpl> m_clientAssertionCredentialImpl;
 
     std::string GetAssertion(Core::Context const& context) const;
     Azure::Core::Http::Request CreateOidcRequestMessage() const;

sdk/identity/azure-identity/inc/azure/identity/client_assertion_credential.hpp

@@ -9,17 +9,15 @@
 #pragma once
 
 #include "azure/identity/detail/client_credential_core.hpp"
-#include "azure/identity/detail/token_cache.hpp"
 
 #include <azure/core/credentials/token_credential_options.hpp>
-#include <azure/core/http/http.hpp>
 
 #include <string>
 #include <vector>
 
 namespace Azure { namespace Identity {
   namespace _detail {
-    class TokenCredentialImpl;
+    class ClientAssertionCredentialImpl;
   } // namespace _detail
 
   /**
@@ -55,11 +53,7 @@ namespace Azure { namespace Identity {
    */
   class ClientAssertionCredential final : public Core::Credentials::TokenCredential {
   private:
-    std::function<std::string(Core::Context const&)> m_assertionCallback;
-    _detail::ClientCredentialCore m_clientCredentialCore;
-    std::unique_ptr<_detail::TokenCredentialImpl> m_tokenCredentialImpl;
-    std::string m_requestBody;
-    _detail::TokenCache m_tokenCache;
+    std::unique_ptr<_detail::ClientAssertionCredentialImpl> m_impl;
 
   public:
     /**

sdk/identity/azure-identity/inc/azure/identity/workload_identity_credential.hpp

@@ -8,6 +8,7 @@
 
 #pragma once
 
+#include "azure/identity/client_assertion_credential.hpp"
 #include "azure/identity/detail/client_credential_core.hpp"
 #include "azure/identity/detail/token_cache.hpp"
 
@@ -18,7 +19,7 @@
 
 namespace Azure { namespace Identity {
   namespace _detail {
-    class TokenCredentialImpl;
+    class ClientAssertionCredentialImpl;
   } // namespace _detail
 
   /**
@@ -74,12 +75,11 @@ namespace Azure { namespace Identity {
    */
   class WorkloadIdentityCredential final : public Core::Credentials::TokenCredential {
   private:
-    _detail::TokenCache m_tokenCache;
-    _detail::ClientCredentialCore m_clientCredentialCore;
-    std::unique_ptr<_detail::TokenCredentialImpl> m_tokenCredentialImpl;
-    std::string m_requestBody;
+    std::unique_ptr<_detail::ClientAssertionCredentialImpl> m_clientAssertionCredentialImpl;
     std::string m_tokenFilePath;
 
+    std::string GetAssertion(Core::Context const& context) const;
+
   public:
     /**
      * @brief Constructs a Workload Identity Credential.

sdk/identity/azure-identity/src/azure_pipelines_credential.cpp

@@ -3,10 +3,10 @@
 
 #include "azure/identity/azure_pipelines_credential.hpp"
 
+#include "private/client_assertion_credential_impl.hpp"
 #include "private/identity_log.hpp"
 #include "private/package_version.hpp"
 #include "private/tenant_id_resolver.hpp"
-#include "private/token_credential_impl.hpp"
 
 #include <azure/core/internal/json/json.hpp>
 
@@ -28,30 +28,6 @@ using Azure::Core::Json::_internal::json;
 using Azure::Identity::_detail::IdentityLog;
 using Azure::Identity::_detail::PackageVersion;
 using Azure::Identity::_detail::TenantIdResolver;
-using Azure::Identity::_detail::TokenCredentialImpl;
-
-namespace {
-bool IsValidTenantId(std::string const& tenantId)
-{
-  const std::string allowedChars = ".-";
-  if (tenantId.empty())
-  {
-    return false;
-  }
-  for (auto const c : tenantId)
-  {
-    if (allowedChars.find(c) != std::string::npos)
-    {
-      continue;
-    }
-    if (!StringExtensions::IsAlphaNumeric(c))
-    {
-      return false;
-    }
-  }
-  return true;
-}
-} // namespace
 
 AzurePipelinesCredential::AzurePipelinesCredential(
     std::string tenantId,
@@ -61,26 +37,10 @@ AzurePipelinesCredential::AzurePipelinesCredential(
     AzurePipelinesCredentialOptions const& options)
     : TokenCredential("AzurePipelinesCredential"), m_serviceConnectionId(serviceConnectionId),
       m_systemAccessToken(systemAccessToken),
-      m_clientCredentialCore(tenantId, options.AuthorityHost, options.AdditionallyAllowedTenants),
       m_httpPipeline(HttpPipeline(options, "identity", PackageVersion::ToString(), {}, {}))
 {
   m_oidcRequestUrl = _detail::DefaultOptionValues::GetOidcRequestUrl();
 
-  bool isTenantIdValid = IsValidTenantId(tenantId);
-  if (!isTenantIdValid)
-  {
-    IdentityLog::Write(
-        IdentityLog::Level::Warning,
-        "Invalid tenant ID provided  for " + GetCredentialName()
-            + ". The tenant ID must be a non-empty string containing only alphanumeric characters, "
-              "periods, or hyphens. You can locate your tenant ID by following the instructions "
-              "listed here: https://learn.microsoft.com/partner-center/find-ids-and-domain-names");
-  }
-  if (clientId.empty())
-  {
-    IdentityLog::Write(
-        IdentityLog::Level::Warning, "No client ID specified for " + GetCredentialName() + ".");
-  }
   if (serviceConnectionId.empty())
   {
     IdentityLog::Write(
@@ -101,20 +61,24 @@ AzurePipelinesCredential::AzurePipelinesCredential(
             + "' needed by " + GetCredentialName() + ". This should be set by Azure Pipelines.");
   }
 
-  if (isTenantIdValid && !clientId.empty() && !serviceConnectionId.empty()
-      && !systemAccessToken.empty() && !m_oidcRequestUrl.empty())
+  if (TenantIdResolver::IsValidTenantId(tenantId) && !clientId.empty()
+      && !serviceConnectionId.empty() && !systemAccessToken.empty() && !m_oidcRequestUrl.empty())
   {
-    m_tokenCredentialImpl = std::make_unique<TokenCredentialImpl>(options);
-    m_requestBody
-        = std::string(
-              "grant_type=client_credentials"
-              "&client_assertion_type="
-              "urn%3Aietf%3Aparams%3Aoauth%3Aclient-assertion-type%3Ajwt-bearer" // cspell:disable-line
-              "&client_id=")
-        + Url::Encode(clientId);
+    ClientAssertionCredentialOptions clientAssertionCredentialOptions{};
+    // Get the options from the base class (including ClientOptions).
+    static_cast<Core::Credentials::TokenCredentialOptions&>(clientAssertionCredentialOptions)
+        = options;
+    clientAssertionCredentialOptions.AuthorityHost = options.AuthorityHost;
+    clientAssertionCredentialOptions.AdditionallyAllowedTenants
+        = options.AdditionallyAllowedTenants;
 
-    IdentityLog::Write(
-        IdentityLog::Level::Informational, GetCredentialName() + " was created successfully.");
+    std::function<std::string(Context const&)> callback
+        = [this](Context const& context) { return GetAssertion(context); };
+
+    // ClientAssertionCredential validates the tenant ID, client ID, and assertion callback and logs
+    // warning messages otherwise.
+    m_clientAssertionCredentialImpl = std::make_unique<_detail::ClientAssertionCredentialImpl>(
+        GetCredentialName(), tenantId, clientId, callback, clientAssertionCredentialOptions);
   }
   else
   {
@@ -214,7 +178,7 @@ AccessToken AzurePipelinesCredential::GetToken(
     TokenRequestContext const& tokenRequestContext,
     Context const& context) const
 {
-  if (!m_tokenCredentialImpl)
+  if (!m_clientAssertionCredentialImpl)
   {
     auto const AuthUnavailable = GetCredentialName() + " authentication unavailable. ";
 
@@ -226,41 +190,6 @@ AccessToken AzurePipelinesCredential::GetToken(
         AuthUnavailable + "Azure Pipelines environment is not set up correctly.");
   }
 
-  auto const tenantId = TenantIdResolver::Resolve(
-      m_clientCredentialCore.GetTenantId(),
-      tokenRequestContext,
-      m_clientCredentialCore.GetAdditionallyAllowedTenants());
-
-  auto const scopesStr
-      = m_clientCredentialCore.GetScopesString(tenantId, tokenRequestContext.Scopes);
-
-  // TokenCache::GetToken() and m_tokenCredentialImpl->GetToken() can only use the lambda
-  // argument when they are being executed. They are not supposed to keep a reference to lambda
-  // argument to call it later. Therefore, any capture made here will outlive the possible time
-  // frame when the lambda might get called.
-  return m_tokenCache.GetToken(scopesStr, tenantId, tokenRequestContext.MinimumExpiration, [&]() {
-    return m_tokenCredentialImpl->GetToken(context, false, [&]() {
-      auto body = m_requestBody;
-      if (!scopesStr.empty())
-      {
-        body += "&scope=" + scopesStr;
-      }
-
-      // Get the request url before calling GetAssertion to validate the authority host scheme.
-      // This is to avoid making a request to the OIDC endpoint if the authority host scheme is
-      // invalid.
-      auto const requestUrl = m_clientCredentialCore.GetRequestUrl(tenantId);
-
-      const std::string assertion = GetAssertion(context);
-
-      body += "&client_assertion=" + Azure::Core::Url::Encode(assertion);
-
-      auto request
-          = std::make_unique<TokenCredentialImpl::TokenRequest>(HttpMethod::Post, requestUrl, body);
-
-      request->HttpRequest.SetHeader("Host", requestUrl.GetHost());
-
-      return request;
-    });
-  });
+  return m_clientAssertionCredentialImpl->GetToken(
+      GetCredentialName(), tokenRequestContext, context);
 }

sdk/identity/azure-identity/src/client_assertion_credential.cpp

@@ -3,15 +3,16 @@
 
 #include "azure/identity/client_assertion_credential.hpp"
 
+#include "private/client_assertion_credential_impl.hpp"
 #include "private/identity_log.hpp"
 #include "private/package_version.hpp"
 #include "private/tenant_id_resolver.hpp"
-#include "private/token_credential_impl.hpp"
 
 #include <azure/core/internal/json/json.hpp>
 
 using Azure::Identity::ClientAssertionCredential;
 using Azure::Identity::ClientAssertionCredentialOptions;
+using Azure::Identity::_detail::ClientAssertionCredentialImpl;
 
 using Azure::Core::Context;
 using Azure::Core::Url;
@@ -24,44 +25,21 @@ using Azure::Identity::_detail::IdentityLog;
 using Azure::Identity::_detail::TenantIdResolver;
 using Azure::Identity::_detail::TokenCredentialImpl;
 
-namespace {
-bool IsValidTenantId(std::string const& tenantId)
-{
-  const std::string allowedChars = ".-";
-  if (tenantId.empty())
-  {
-    return false;
-  }
-  for (auto const c : tenantId)
-  {
-    if (allowedChars.find(c) != std::string::npos)
-    {
-      continue;
-    }
-    if (!StringExtensions::IsAlphaNumeric(c))
-    {
-      return false;
-    }
-  }
-  return true;
-}
-} // namespace
-
-ClientAssertionCredential::ClientAssertionCredential(
+ClientAssertionCredentialImpl::ClientAssertionCredentialImpl(
+    std::string const& credentialName,
     std::string tenantId,
     std::string clientId,
     std::function<std::string(Context const&)> assertionCallback,
     ClientAssertionCredentialOptions const& options)
-    : TokenCredential("ClientAssertionCredential"),
-      m_assertionCallback(std::move(assertionCallback)),
+    : m_assertionCallback(std::move(assertionCallback)),
       m_clientCredentialCore(tenantId, options.AuthorityHost, options.AdditionallyAllowedTenants)
 {
-  bool isTenantIdValid = IsValidTenantId(tenantId);
+  bool isTenantIdValid = TenantIdResolver::IsValidTenantId(tenantId);
   if (!isTenantIdValid)
   {
     IdentityLog::Write(
         IdentityLog::Level::Warning,
-        GetCredentialName()
+        credentialName
             + ": Invalid tenant ID provided. The tenant ID must be a non-empty string containing "
               "only alphanumeric characters, periods, or hyphens. You can locate your tenant ID by "
               "following the instructions listed here: "
@@ -69,14 +47,13 @@ ClientAssertionCredential::ClientAssertionCredential(
   }
   if (clientId.empty())
   {
-    IdentityLog::Write(
-        IdentityLog::Level::Warning, GetCredentialName() + ": No client ID specified.");
+    IdentityLog::Write(IdentityLog::Level::Warning, credentialName + ": No client ID specified.");
   }
   if (!m_assertionCallback)
   {
     IdentityLog::Write(
         IdentityLog::Level::Warning,
-        GetCredentialName()
+        credentialName
             + ": The assertionCallback must be a valid function that returns assertions.");
   }
 
@@ -92,7 +69,7 @@ ClientAssertionCredential::ClientAssertionCredential(
         + Url::Encode(clientId);
 
     IdentityLog::Write(
-        IdentityLog::Level::Informational, GetCredentialName() + " was created successfully.");
+        IdentityLog::Level::Informational, credentialName + " was created successfully.");
   }
   else
   {
@@ -101,23 +78,22 @@ ClientAssertionCredential::ClientAssertionCredential(
     // primarily needed for credentials that are part of the DefaultAzureCredential, which this
     // credential is not intended for.
     IdentityLog::Write(
-        IdentityLog::Level::Warning, GetCredentialName() + " was not initialized correctly.");
+        IdentityLog::Level::Warning, credentialName + " was not initialized correctly.");
   }
 }
 
-ClientAssertionCredential::~ClientAssertionCredential() = default;
-
-AccessToken ClientAssertionCredential::GetToken(
+AccessToken ClientAssertionCredentialImpl::GetToken(
+    std::string const& credentialName,
     TokenRequestContext const& tokenRequestContext,
     Context const& context) const
 {
   if (!m_tokenCredentialImpl)
   {
-    auto const AuthUnavailable = GetCredentialName() + " authentication unavailable. ";
+    auto const AuthUnavailable = credentialName + " authentication unavailable. ";
 
     IdentityLog::Write(
         IdentityLog::Level::Warning,
-        AuthUnavailable + "See earlier " + GetCredentialName() + " log messages for details.");
+        AuthUnavailable + "See earlier " + credentialName + " log messages for details.");
 
     throw AuthenticationException(AuthUnavailable);
   }
@@ -160,3 +136,27 @@ AccessToken ClientAssertionCredential::GetToken(
     });
   });
 }
+
+ClientAssertionCredential::ClientAssertionCredential(
+    std::string tenantId,
+    std::string clientId,
+    std::function<std::string(Context const&)> assertionCallback,
+    ClientAssertionCredentialOptions const& options)
+    : TokenCredential("ClientAssertionCredential"),
+      m_impl(std::make_unique<ClientAssertionCredentialImpl>(
+          GetCredentialName(),
+          tenantId,
+          clientId,
+          assertionCallback,
+          options))
+{
+}
+
+ClientAssertionCredential::~ClientAssertionCredential() = default;
+
+AccessToken ClientAssertionCredential::GetToken(
+    TokenRequestContext const& tokenRequestContext,
+    Context const& context) const
+{
+  return m_impl->GetToken(GetCredentialName(), tokenRequestContext, context);
+}

sdk/identity/azure-identity/src/private/client_assertion_credential_impl.hpp

@@ -0,0 +1,42 @@
+// Copyright (c) Microsoft Corporation.
+// Licensed under the MIT License.
+
+/**
+ * @file
+ * @brief Client Assertion Credential and options.
+ */
+
+#pragma once
+
+#include "azure/identity/client_assertion_credential.hpp"
+#include "azure/identity/detail/client_credential_core.hpp"
+#include "azure/identity/detail/token_cache.hpp"
+#include "token_credential_impl.hpp"
+
+#include <string>
+
+namespace Azure { namespace Identity { namespace _detail {
+  class TokenCredentialImpl;
+
+  class ClientAssertionCredentialImpl final {
+  private:
+    std::function<std::string(Core::Context const&)> m_assertionCallback;
+    _detail::ClientCredentialCore m_clientCredentialCore;
+    std::unique_ptr<TokenCredentialImpl> m_tokenCredentialImpl;
+    std::string m_requestBody;
+    _detail::TokenCache m_tokenCache;
+
+  public:
+    ClientAssertionCredentialImpl(
+        std::string const& credentialName,
+        std::string tenantId,
+        std::string clientId,
+        std::function<std::string(Core::Context const&)> assertionCallback,
+        ClientAssertionCredentialOptions const& options = {});
+
+    Core::Credentials::AccessToken GetToken(
+        std::string const& credentialName,
+        Core::Credentials::TokenRequestContext const& tokenRequestContext,
+        Core::Context const& context) const;
+  };
+}}} // namespace Azure::Identity::_detail

sdk/identity/azure-identity/src/private/tenant_id_resolver.hpp

@@ -25,5 +25,7 @@ namespace Azure { namespace Identity { namespace _detail {
 
     // ADFS is the Active Directory Federation Service, a tenant ID that is used in Azure Stack.
     static bool IsAdfs(std::string const& tenantId);
+
+    static bool IsValidTenantId(std::string const& tenantId);
   };
 }}} // namespace Azure::Identity::_detail

sdk/identity/azure-identity/src/tenant_id_resolver.cpp

@@ -56,3 +56,24 @@ bool TenantIdResolver::IsAdfs(std::string const& tenantId)
 {
   return StringExtensions::LocaleInvariantCaseInsensitiveEqual(tenantId, "adfs");
 }
+
+bool TenantIdResolver::IsValidTenantId(std::string const& tenantId)
+{
+  const std::string allowedChars = ".-";
+  if (tenantId.empty())
+  {
+    return false;
+  }
+  for (auto const c : tenantId)
+  {
+    if (allowedChars.find(c) != std::string::npos)
+    {
+      continue;
+    }
+    if (!StringExtensions::IsAlphaNumeric(c))
+    {
+      return false;
+    }
+  }
+  return true;
+}

sdk/identity/azure-identity/src/workload_identity_credential.cpp

@@ -3,9 +3,9 @@
 
 #include "azure/identity/workload_identity_credential.hpp"
 
+#include "private/client_assertion_credential_impl.hpp"
 #include "private/identity_log.hpp"
 #include "private/tenant_id_resolver.hpp"
-#include "private/token_credential_impl.hpp"
 
 #include <azure/core/internal/environment.hpp>
 
@@ -23,35 +23,32 @@ using Azure::Core::Credentials::TokenRequestContext;
 using Azure::Core::Http::HttpMethod;
 using Azure::Identity::_detail::IdentityLog;
 using Azure::Identity::_detail::TenantIdResolver;
-using Azure::Identity::_detail::TokenCredentialImpl;
 
 WorkloadIdentityCredential::WorkloadIdentityCredential(
     WorkloadIdentityCredentialOptions const& options)
-    : TokenCredential("WorkloadIdentityCredential"), m_clientCredentialCore(
-                                                         options.TenantId,
-                                                         options.AuthorityHost,
-                                                         options.AdditionallyAllowedTenants)
+    : TokenCredential("WorkloadIdentityCredential")
 {
   std::string tenantId = options.TenantId;
   std::string clientId = options.ClientId;
-  std::string authorityHost = options.AuthorityHost;
   m_tokenFilePath = options.TokenFilePath;
 
-  if (!tenantId.empty() && !clientId.empty() && !m_tokenFilePath.empty())
+  if (TenantIdResolver::IsValidTenantId(tenantId) && !clientId.empty() && !m_tokenFilePath.empty())
   {
-    m_clientCredentialCore = Azure::Identity::_detail::ClientCredentialCore(
-        tenantId, authorityHost, options.AdditionallyAllowedTenants);
-    m_tokenCredentialImpl = std::make_unique<TokenCredentialImpl>(options);
-    m_requestBody
-        = std::string(
-              "grant_type=client_credentials"
-              "&client_assertion_type="
-              "urn%3Aietf%3Aparams%3Aoauth%3Aclient-assertion-type%3Ajwt-bearer" // cspell:disable-line
-              "&client_id=")
-        + Url::Encode(clientId);
+    ClientAssertionCredentialOptions clientAssertionCredentialOptions{};
+    // Get the options from the base class (including ClientOptions).
+    static_cast<Core::Credentials::TokenCredentialOptions&>(clientAssertionCredentialOptions)
+        = options;
+    clientAssertionCredentialOptions.AuthorityHost = options.AuthorityHost;
+    clientAssertionCredentialOptions.AdditionallyAllowedTenants
+        = options.AdditionallyAllowedTenants;
 
-    IdentityLog::Write(
-        IdentityLog::Level::Informational, GetCredentialName() + " was created successfully.");
+    std::function<std::string(Context const&)> callback
+        = [this](Context const& context) { return GetAssertion(context); };
+
+    // ClientAssertionCredential validates the tenant ID, client ID, and assertion callback and logs
+    // warning messages otherwise.
+    m_clientAssertionCredentialImpl = std::make_unique<_detail::ClientAssertionCredentialImpl>(
+        GetCredentialName(), tenantId, clientId, callback, clientAssertionCredentialOptions);
   }
   else
   {
@@ -64,30 +61,26 @@ WorkloadIdentityCredential::WorkloadIdentityCredential(
 
 WorkloadIdentityCredential::WorkloadIdentityCredential(
     Core::Credentials::TokenCredentialOptions const& options)
-    : TokenCredential("WorkloadIdentityCredential"),
-      m_clientCredentialCore("", "", std::vector<std::string>())
+    : TokenCredential("WorkloadIdentityCredential")
 {
   std::string const tenantId = _detail::DefaultOptionValues::GetTenantId();
   std::string const clientId = _detail::DefaultOptionValues::GetClientId();
   m_tokenFilePath = _detail::DefaultOptionValues::GetFederatedTokenFile();
 
-  if (!tenantId.empty() && !clientId.empty() && !m_tokenFilePath.empty())
+  if (TenantIdResolver::IsValidTenantId(tenantId) && !clientId.empty() && !m_tokenFilePath.empty())
   {
-    std::string const authorityHost = _detail::DefaultOptionValues::GetAuthorityHost();
+    ClientAssertionCredentialOptions clientAssertionCredentialOptions{};
+    // Get the options from the base class (including ClientOptions).
+    static_cast<Core::Credentials::TokenCredentialOptions&>(clientAssertionCredentialOptions)
+        = options;
 
-    m_clientCredentialCore = Azure::Identity::_detail::ClientCredentialCore(
-        tenantId, authorityHost, std::vector<std::string>());
-    m_tokenCredentialImpl = std::make_unique<TokenCredentialImpl>(options);
-    m_requestBody
-        = std::string(
-              "grant_type=client_credentials"
-              "&client_assertion_type="
-              "urn%3Aietf%3Aparams%3Aoauth%3Aclient-assertion-type%3Ajwt-bearer" // cspell:disable-line
-              "&client_id=")
-        + Url::Encode(clientId);
+    std::function<std::string(Context const&)> callback
+        = [this](Context const& context) { return GetAssertion(context); };
 
-    IdentityLog::Write(
-        IdentityLog::Level::Informational, GetCredentialName() + " was created successfully.");
+    // ClientAssertionCredential validates the tenant ID, client ID, and assertion callback and logs
+    // warning messages otherwise.
+    m_clientAssertionCredentialImpl = std::make_unique<_detail::ClientAssertionCredentialImpl>(
+        GetCredentialName(), tenantId, clientId, callback, clientAssertionCredentialOptions);
   }
   else
   {
@@ -100,11 +93,21 @@ WorkloadIdentityCredential::WorkloadIdentityCredential(
 
 WorkloadIdentityCredential::~WorkloadIdentityCredential() = default;
 
+std::string WorkloadIdentityCredential::GetAssertion(Context const&) const
+{
+  // Read the specified file's content, which is expected to be a Kubernetes service account
+  // token. Kubernetes is responsible for updating the file as service account tokens expire.
+  std::ifstream azureFederatedTokenFile(m_tokenFilePath);
+  std::string assertion(
+      (std::istreambuf_iterator<char>(azureFederatedTokenFile)), std::istreambuf_iterator<char>());
+  return assertion;
+}
+
 AccessToken WorkloadIdentityCredential::GetToken(
     TokenRequestContext const& tokenRequestContext,
     Context const& context) const
 {
-  if (!m_tokenCredentialImpl)
+  if (!m_clientAssertionCredentialImpl)
   {
     auto const AuthUnavailable = GetCredentialName() + " authentication unavailable. ";
 
@@ -116,43 +119,6 @@ AccessToken WorkloadIdentityCredential::GetToken(
         AuthUnavailable + "Azure Kubernetes environment is not set up correctly.");
   }
 
-  auto const tenantId = TenantIdResolver::Resolve(
-      m_clientCredentialCore.GetTenantId(),
-      tokenRequestContext,
-      m_clientCredentialCore.GetAdditionallyAllowedTenants());
-
-  auto const scopesStr
-      = m_clientCredentialCore.GetScopesString(tenantId, tokenRequestContext.Scopes);
-
-  // TokenCache::GetToken() and m_tokenCredentialImpl->GetToken() can only use the lambda argument
-  // when they are being executed. They are not supposed to keep a reference to lambda argument to
-  // call it later. Therefore, any capture made here will outlive the possible time frame when the
-  // lambda might get called.
-  return m_tokenCache.GetToken(scopesStr, tenantId, tokenRequestContext.MinimumExpiration, [&]() {
-    return m_tokenCredentialImpl->GetToken(context, false, [&]() {
-      auto body = m_requestBody;
-      if (!scopesStr.empty())
-      {
-        body += "&scope=" + scopesStr;
-      }
-
-      auto const requestUrl = m_clientCredentialCore.GetRequestUrl(tenantId);
-
-      // Read the specified file's content, which is expected to be a Kubernetes service account
-      // token. Kubernetes is responsible for updating the file as service account tokens expire.
-      std::ifstream azureFederatedTokenFile(m_tokenFilePath);
-      std::string assertion(
-          (std::istreambuf_iterator<char>(azureFederatedTokenFile)),
-          std::istreambuf_iterator<char>());
-
-      body += "&client_assertion=" + Azure::Core::Url::Encode(assertion);
-
-      auto request
-          = std::make_unique<TokenCredentialImpl::TokenRequest>(HttpMethod::Post, requestUrl, body);
-
-      request->HttpRequest.SetHeader("Host", requestUrl.GetHost());
-
-      return request;
-    });
-  });
+  return m_clientAssertionCredentialImpl->GetToken(
+      GetCredentialName(), tokenRequestContext, context);
 }