aws: add support for instance profiles (#576)

Currently there is no way of assigning IAM roles to runner instances at
creation time. This PR adds an additional field in the AWS backend which
creates EC2 instances with the specified `IamInstanceProfile`,
configurable by the `iam_instance_profile_arn` field in the
`runner-manager.yaml` config.

This implementation only accepts instances profiles by their ARN and not
by their name to keep the implementation as simple as possible.

runner_manager/models/backend.py

@@ -7,6 +7,7 @@
 from mypy_boto3_ec2.type_defs import (
     BlockDeviceMappingTypeDef,
     EbsBlockDeviceTypeDef,
+    IamInstanceProfileTypeDef,
     TagSpecificationTypeDef,
     TagTypeDef,
 )
@@ -133,6 +134,7 @@ class AWSConfig(BackendConfig):
         "BlockDeviceMappings": Sequence[BlockDeviceMappingTypeDef],
         "MaxCount": int,
         "MinCount": int,
+        "IamInstanceProfile": IamInstanceProfileTypeDef,
     },
 )
 
@@ -150,6 +152,7 @@ class AWSInstanceConfig(InstanceConfig):
     tags: Dict[str, str] = {}
     volume_type: VolumeTypeType = "gp3"
     disk_size_gb: int = 20
+    iam_instance_profile_arn: str = ""
 
     def configure_instance(self, runner: Runner) -> AwsInstance:
         """Configure instance."""
@@ -184,6 +187,9 @@ def configure_instance(self, runner: Runner) -> AwsInstance:
                 Tags=tags,
             ),
         ]
+        iam_instance_profile: IamInstanceProfileTypeDef = IamInstanceProfileTypeDef(
+            Arn=self.iam_instance_profile_arn
+        )
         return AwsInstance(
             ImageId=self.image,
             InstanceType=self.instance_type,
@@ -194,4 +200,5 @@ def configure_instance(self, runner: Runner) -> AwsInstance:
             MaxCount=self.max_count,
             MinCount=self.min_count,
             BlockDeviceMappings=block_device_mappings,
+            IamInstanceProfile=iam_instance_profile,
         )

tests/unit/backend/test_aws.py

@@ -46,11 +46,17 @@ def aws_runner(runner: Runner, aws_group: RunnerGroup) -> Runner:
 def test_aws_instance_config(runner: Runner):
     AWSConfig()
     instance_config = AWSInstanceConfig(
-        tags={"test": "test"}, subnet_id="i-0f9b0a3b7b3b3b3b3"
+        tags={"test": "test"},
+        subnet_id="i-0f9b0a3b7b3b3b3b3",
+        iam_instance_profile_arn="test",
     )
     instance: AwsInstance = instance_config.configure_instance(runner)
     assert instance["ImageId"] == instance_config.image
     assert instance["SubnetId"] == instance_config.subnet_id
+    assert (
+        instance["IamInstanceProfile"]["Arn"]
+        == instance_config.iam_instance_profile_arn
+    )
     assert runner.name in instance["UserData"]
     tags = instance["TagSpecifications"][0]["Tags"]
     assert TagTypeDef(Key="test", Value="test") in tags