[Core] Support getting SSH certificate inside Cloud Shell

scripts/release/debian/build.sh

@@ -23,6 +23,9 @@ apt-get update
 # uuid-dev is used to build _uuid module: https://github.com/python/cpython/pull/3796
 apt-get install -y libssl-dev libffi-dev python3-dev debhelper zlib1g-dev uuid-dev
 apt-get install -y wget
+# Git is not strictly necessary, but it would allow building an experimental package
+# with dependency which is currently only available in its git repo feature branch.
+apt-get install -y git
 
 # Download Python source code
 PYTHON_SRC_DIR=$(mktemp -d)

src/azure-cli-core/azure/cli/core/auth/adal_authentication.py

@@ -16,12 +16,29 @@ class MSIAuthenticationWrapper(MSIAuthentication):
     # This method is exposed for Azure Core. Add *scopes, **kwargs to fit azure.core requirement
     # pylint: disable=line-too-long
     def get_token(self, *scopes, **kwargs):  # pylint:disable=unused-argument
-        logger.debug("MSIAuthenticationWrapper.get_token invoked by Track 2 SDK with scopes=%s", scopes)
+        logger.debug("MSIAuthenticationWrapper.get_token: scopes=%r, kwargs=%r", scopes, kwargs)
 
         if 'data' in kwargs:
+            from azure.cli.core.util import in_cloud_console
+            if in_cloud_console():
+                # Use MSAL to get VM SSH certificate
+                import msal
+                from .util import check_result, build_sdk_access_token
+                from .identity import AZURE_CLI_CLIENT_ID
+                app = msal.PublicClientApplication(
+                    AZURE_CLI_CLIENT_ID,  # Use a real client_id, so that cache would work
+                    # TODO: This PoC does not currently maintain a token cache;
+                    #   Ideally we should reuse the real MSAL app object which has cache configured.
+                    # token_cache=...,
+                )
+                result = app.acquire_token_interactive(list(scopes), prompt="none", data=kwargs["data"])
+                check_result(result, scopes=scopes)
+                return build_sdk_access_token(result)
+
             from azure.cli.core.azclierror import AuthenticationError
-            raise AuthenticationError("VM SSH currently doesn't support managed identity or Cloud Shell.")
+            raise AuthenticationError("VM SSH currently doesn't support managed identity.")
 
+        # Use msrestazure to get access token
         resource = scopes_to_resource(_normalize_scopes(scopes))
         if resource:
             # If available, use resource provided by SDK
@@ -55,7 +72,7 @@ def set_token(self):
         import traceback
         from azure.cli.core.azclierror import AzureConnectionError, AzureResponseError
         try:
-            super(MSIAuthenticationWrapper, self).set_token()
+            super().set_token()
         except requests.exceptions.ConnectionError as err:
             logger.debug('throw requests.exceptions.ConnectionError when doing MSIAuthentication: \n%s',
                          traceback.format_exc())

src/azure-cli-core/azure/cli/core/auth/credential_adaptor.py

@@ -44,7 +44,7 @@ def _get_token(self, scopes=None, **kwargs):
             raise CLIError(SSLERROR_TEMPLATE.format(str(err)))
 
     def signed_session(self, session=None):
-        logger.debug("CredentialAdaptor.get_token")
+        logger.debug("CredentialAdaptor.signed_session")
         session = session or requests.Session()
         token, external_tenant_tokens = self._get_token()
         header = "{} {}".format('Bearer', token.token)

src/azure-cli-core/azure/cli/core/auth/msal_authentication.py

@@ -6,15 +6,15 @@
 """
 Credentials defined in this module are alternative implementations of credentials provided by Azure Identity.
 
-These credentials implements azure.core.credentials.TokenCredential by exposing get_token method for Track 2
+These credentials implement azure.core.credentials.TokenCredential by exposing get_token method for Track 2
 SDK invocation.
 """
 
 from knack.log import get_logger
 from knack.util import CLIError
 from msal import PublicClientApplication, ConfidentialClientApplication
 
-from .util import check_result, AccessToken
+from .util import check_result, build_sdk_access_token
 
 # OAuth 2.0 client credentials flow parameter
 # https://docs.microsoft.com/en-us/azure/active-directory/develop/v2-oauth2-client-creds-grant-flow
@@ -87,7 +87,7 @@ def get_token(self, *scopes, **kwargs):
             # launch browser, but show the error message and `az login` command instead.
             else:
                 raise
-        return _build_sdk_access_token(result)
+        return build_sdk_access_token(result)
 
 
 class ServicePrincipalCredential(ConfidentialClientApplication):
@@ -130,21 +130,4 @@ def get_token(self, *scopes, **kwargs):
         if not result:
             result = self.acquire_token_for_client(scopes, **kwargs)
         check_result(result)
-        return _build_sdk_access_token(result)
-
-
-def _build_sdk_access_token(token_entry):
-    import time
-    request_time = int(time.time())
-
-    # MSAL token entry sample:
-    # {
-    #     'access_token': 'eyJ0eXAiOiJKV...',
-    #     'token_type': 'Bearer',
-    #     'expires_in': 1618
-    # }
-
-    # Importing azure.core.credentials.AccessToken is expensive.
-    # This can slow down commands that doesn't need azure.core, like `az account get-access-token`.
-    # So We define our own AccessToken.
-    return AccessToken(token_entry["access_token"], request_time + token_entry["expires_in"])
+        return build_sdk_access_token(result)

src/azure-cli-core/azure/cli/core/auth/util.py

@@ -20,17 +20,27 @@ def aad_error_handler(error, **kwargs):
     # https://docs.microsoft.com/en-us/azure/active-directory/develop/reference-aadsts-error-codes
     # Search for an error code at https://login.microsoftonline.com/error
 
+    # To trigger this function for testing, simply provide an invalid scope:
+    # az account get-access-token --scope https://my-invalid-scope
+
     from azure.cli.core.util import in_cloud_console
     if in_cloud_console():
         import socket
         logger.warning("A Cloud Shell credential problem occurred. When you report the issue with the error "
                        "below, please mention the hostname '%s'", socket.gethostname())
 
-    msg = error.get('error_description')
-    login_message = _generate_login_message(**kwargs)
+    error_description = error.get('error_description')
+
+    # Build recommendation message
+    login_command = _generate_login_command(**kwargs)
+    login_message = (
+        # Cloud Shell uses IMDS-like interface for implicit login. If getting token/cert failed,
+        # we let the user explicitly log in to AAD with MSAL.
+        "Please explicitly log in with:\n{}" if error.get('error') == 'broker_error'
+        else "To re-authenticate, please run:\n{}").format(login_command)
 
     from azure.cli.core.azclierror import AuthenticationError
-    raise AuthenticationError(msg, recommendation=login_message)
+    raise AuthenticationError(error_description, recommendation=login_message)
 
 
 def _generate_login_command(scopes=None):
@@ -43,16 +53,6 @@ def _generate_login_command(scopes=None):
     return ' '.join(login_command)
 
 
-def _generate_login_message(**kwargs):
-    from azure.cli.core.util import in_cloud_console
-    login_command = _generate_login_command(**kwargs)
-
-    msg = "To re-authenticate, please {}" .format(
-        "refresh Azure Portal." if in_cloud_console() else "run:\n{}".format(login_command))
-
-    return msg
-
-
 def resource_to_scopes(resource):
     """Convert the ADAL resource ID to MSAL scopes by appending the /.default suffix and return a list.
     For example:
@@ -139,6 +139,23 @@ def check_result(result, **kwargs):
     return None
 
 
+def build_sdk_access_token(token_entry):
+    import time
+    request_time = int(time.time())
+
+    # MSAL token entry sample:
+    # {
+    #     'access_token': 'eyJ0eXAiOiJKV...',
+    #     'token_type': 'Bearer',
+    #     'expires_in': 1618
+    # }
+
+    # Importing azure.core.credentials.AccessToken is expensive.
+    # This can slow down commands that doesn't need azure.core, like `az account get-access-token`.
+    # So We define our own AccessToken.
+    return AccessToken(token_entry["access_token"], request_time + token_entry["expires_in"])
+
+
 def decode_access_token(access_token):
     # Decode the access token. We can do the same with https://jwt.ms
     from msal.oauth2cli.oidc import decode_part

src/azure-cli-core/setup.py

@@ -52,7 +52,7 @@
     'jmespath',
     'knack~=0.9.0',
     'msal-extensions~=1.0.0',
-    'msal>=1.17.0,<2.0.0',
+    'msal @ git+https://github.com/AzureAD/microsoft-authentication-library-for-python.git@cloudshell-imds',  # TBD: 'msal>=1.18.0,<2.0.0',
     'msrestazure~=0.6.4',
     'packaging>=20.9,<22.0',
     'paramiko>=2.0.8,<3.0.0',

src/azure-cli/requirements.py3.Linux.txt

@@ -111,7 +111,8 @@ jsondiff==1.3.0
 knack==0.9.0
 MarkupSafe==1.1.1
 msal-extensions==1.0.0
-msal==1.17.0
+#msal==1.17.0
+git+https://github.com/AzureAD/microsoft-authentication-library-for-python.git@cloudshell-imds#egg=msal
 msrest==0.6.21
 msrestazure==0.6.4
 oauthlib==3.0.1